ULTIMATE BIO MIDTERM QUIZLET
atomic mass
an approx of the total mass of an atom, measured in Daltons
What is linear electron flow?
an electron transport chain that is similar to the one in cellular respiration
protein phosphatases
an enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase
protein kinase
an enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein
The second type of receptors described are receptor tyrosine kinases. Explain what a kinase enzyme does.
an enzymes that catalyzes the transfer of phosphate groups
nondisjunction
an error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other
independent event
an event whose outcome is unaffected by what has happened on previous trials, such as in a sequence of coin tosses
Shape of the bacterial chromosome between prokaryotic and eukaryotic cells?
circular in prokaryotes; linear in eukaryotes
adhesion
clinging of one substance to another
photosystem
composed of a protein complex called a reaction center surrounded by several light-harvesting complexes
State the hypothesis formulated by George Beadle while studying eye color mutations in Drosophila
in Drosophila, each of the various mutations affecting eye color blocks pigment synthesis at a specific step by preventing production of the enzyme that catalyzes that step
cis-trans isomer
have covalent bonds to the same atoms, but these atoms differ in their special arrangements due to the inflexibility of double bonds (petroleum and trans fat)
Describe Nirenberg's experiment in which he identified the first codon.
he synthesized an artificial mRNA by linking identical RNA nucleotides containing uracil as their base
carrier proteins
hold onto passengers and change shape in a way that shuttles them across the membrane.
single-strand binding proteins
holds DNA strands apart
Break down hydrolysis and what each root word means.
hydro: water lysis: break
As electrons fall from photosystem II to photosystem I, the cytochrome complex uses the energy to pump ________ ions. This builds a proton gradient that is used in chemiosmosis to produce ___?
hydrogen; ATP
What two ions form when water dissociates?
hydronium (H3O+) and hydroxide ions (OH-)
Why are the "tails" hydrophobic?
hydrophobic (avoid water) because they are hydrocarbon; their bonds are relatively nonpolar carbon-to-hydrogen
Are hydrocarbons hydrophobic or hydrophilic?
hydrophobic, meaning they do not dissolve in water; majority of their bonds are relatively nonpolar carbon-to-hydrogen linkages
glycogen
is a strorage polysaccharide produced by vertebrates; stored in liver
P generation
parent generation
When Thomas Hunt Morgan mated a white-eyed male fly with a red-eyed female, he came to the startling conclusion that the trait for eye color was located on the chromosome that determines sex. Show this cross.
parental generation: A red-eyed female was crossed with a white-eyed male. F1 generation: All the offspring of the P generation had red eyes F2 generation: The offspring showed a ratio of three red-eyed flies to one white- eyed fly. However, there were no white-eyed females.
Name a human enzyme that functions well in pH 2. Where is it found?
pepsin; in the stomach
Figure 17.12
pg 335
What are the three components of a nucleotide?
phosphate group, sugar, nucleotide
In what photosystem does NADP+ redctase catalyze the transfer of the excited electron and H+ to NADP+ to form NADPH?
photosystem I
What are the two categories of mutagens?
physical and chemical
T or F: In meiosis, the DNA is replicated during interphase, followed by two divisions. The first division is meiosis I.
true
Name the enzyme that uses the DNA template strand to transcribe a new mRNA strand.
RNA polymerase
Recall that DNA polymerase III adds new nucleotides to the template DNA strand to assemble each new strand of DNA. Both enzymes can assemble a new polynucleotide only in the 5'--> direction. Which enzyme, DNA polymerase III or RNA polymerase, does not require a primer to begin synthesis?
RNA polymerase
isotonic
Referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell.
monosomy
Refers to a diploid cell that has only one copy of a particular chromosome instead of the normal two. Turner syndrome is a human monosomy; the female has only one X chromosome
trisomy
Refers to a diploid cell that has three copies of a particular chromosome instead of the normal two. Trisomy 21 is trisomic for chromosome 21
In the cell fractionation, which organelles are the smallest ones isolated in this procedure?
Ribosomes
When are the nucleioli visible? What are assembled here?
Ribosomes are assembled.
What is the function of ribosomes? What are their two components?
Ribosomes- complexes made of ribosmal RNA abd protein, are the cellular components and carry out protein synthesis. The two components are Ribosmal RNA and proteins.
Scanning Electron Microscopy vs. Transmission Electron Microscopy
Scanning- Useful to study the surface of a specimen. Show a 3D image of the surface of a specimen. Transmission- Used to study the internal ultrastructure of cells. Profiles a thin section of a specimen.
Figure 17.8
See page 333 of text for the labeled figure and description of each stage.
Label the ester linkages on figure 5.11.
See page 75 of text for the labeled figure.
Figure 5.20, levels of protein structure
See pages 82-83 of text for the labeled figure.
Describe the means by which Hershey and Chase established that only the DNA of a phage enters an E. coli cell. What conclusions did these scientists draw based on these observations?
Separate samples of the nonradioactive E. coli cells were allowed to be infected by the protein- labeled and DNA-labeled batches of T2. The researchers then tested the two samples shortly after the onset of infection to see which type of molecule—protein or DNA—had entered the bacterial cells and would therefore be capable of reprogramming them. Hershey and Chase found that the phage of DNA entered the host cells but the phage protein did not. Hershey and Chase concluded that the DNA injected by the phage must be the molecule carrying the genetic information that makes the cells produce new viral DNA and proteins.
Four functions of microtubules
Shape and support Cell Serve as tracks along which organelles equipped with motor proteins can move Seperate chromosomes during cell division.
What are Okazaki fragments, and how are they welded together?
Short segments of DNA synthesized away from the replication fork on a template strand during DNA replication. They are joined together by the enzyme DNA ligase to make up the lagging strand of newly synthesized DNA
Function of Mitochondria
Sites of cellular respiration, the metabolic process that generates ATP by extracting energy from sugars, fats, and other fuels.
Function of chloroplasts
Sites of photosynthesis
What are three things that can be determined from karyotype?
Size of the chromosome, position of the centromere, and pattern of the stained bands
What event is coded for by UAA, UAG, and UGA?
Stop
G1
"first gap"; the first part of interphase
G2
"second gap"; the last part of interphase
hydroxyl group
-OH
What is a gene?
-a region of DNA that can be expressed to produce a final functional product that is either a polypeptide or an RNA molecule -one gene codes for one polypeptide
Give two problems with the davson-danelli model of membrane structure.
-all membranes of a cell are not identical -protein placement-membrane proteins are amphipathic, if such proteins were layerd on surface of membrane, their hydrophobic parts would be in aqueous surroundings.
What is the root word for sugar?
-ose
Describe what happens to a transport vesicle and its contents when it arrives at the Golgi.
...
What are Chargaff's rules?
1. The base composition varies between species 2. Within a species, the number of A and T bases are equal and the number G and C bases are equal
How many times does the cell divide in meiosis?
2
How many nucleotide bases are there? How many amino acids?
4; 20
Duchenne muscular dystrophy
A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue
Describe why many neurons and intestinal cells each have greatly increased surface area.
A sufficiently high ratio of surface area to volume is especially important in cells that exchange a lot of material with their surroundings.
a. Sugar source
A sugar source is a plant organ that is a net producer of sugar by photosynthesis or by breakdown of starch
What are the base pairings?
A-T, C-G, A-U
what powers active transport?
ATP
What is the start codon?
AUG
17. What is the cohesion-tension hypothesis?
According to the cohesion-tension hypothesis, transpiration provides the pull for the ascent of xylem sap, and the cohesion of water molecules transmits this pull along the entire length of the xylem from shoots to roots. Hence, xylem sap is normally under negative pressure or tension. Because transpiration is a "pulling" process, our exploration of the rise of xylem sap by the cohesion-tension mechanism begins not with the roots but with the leaves, where the driving force for transpirational pull begins.
Why is the genetic code said to be redundant but not ambiguous?
Although more than one codon may specify a particular amino acid, neither codon specifies any other amino acid
Explain the energy usage in anabolic pathways of biosynthesis.
Anabolic pathways can use small molecules from food directly or build other substances using intermediates of glycolysis or the citric acid cycle.
b. Aquaporins
Aquaporins are the transport proteins that facilitate the transport of water molecules across membranes.
Which two domains consists of prokaryotic cells?
Bacteria and Archaea
What revision of detail (but not of basic principle) did this hypothesis undergo as more information was gained? *important*
Because not all proteins are enzymes, and because each protein consists of two or more different polypeptide chains, each specified by its own gene, the hypothesis was revised. Beadle and Tatum's idea was restated as the one gene-one polypeptide hypothesis.
Name three human sex-linked disorders.
Duchenne muscular dystrophy, Hemophilia, color blindness
A second function of lysosomes is to recycle cellular components in a process called autophagy. Describe this process.
During autophagy, a damaged organelle or small amount of cytosol becomes surrounded by a double membrane, which is of origin unknown and a lysosome fused with the membrane of the vesicle.
How many hydrogen bonds can a single water molecule form?
Each water molecule can form 4 hydrogen bonds.
Who has more potential energy: electron in the first energy shell/electron in the third energy shell?
Electron in the third energy shell has more potential energy because of its relative distance from the nucleus.
List all the structures of the endomembrane system.
Endoplasmic Reticulum (smooth and rough), Lysosomes, Golgi Apparatus, Vacuoles.
Production of one net G3P?
The Calvin cycle must be turned three times. Each turn will require a starting molecule of ribulose bisphosphate (RuBP), a five-carbon compound. This means we start with 15 carbons distributed in three RuBPs. After fixing three molecules of CO2 using the enzyme rubisco, the Calvin cycle forms six G3Ps with a total of 18 carbons. At this point the net gain of carbons is 3, or one net G3P molecule.
How does a prokaryotic ribosome differ from a eukaryotic ribosome? What is the medical significance of this difference?
Eukaryotic ribosomes are slightly larger in structure and differ somewhat from bacterial ribosomes in their molecular composition. Certain antibiotic drugs can inactivate bacterial ribosomes without inhibiting the ability of eukaryotic ribosomes to make proteins. These drugs, including tetracycline and streptomycin, are used to combat bacterial infections
Why is height a good example of polygenic inheritance?
For many characters, such as human skin color and height, an either-or classification is impossible because the characters vary in the population in gradients along a continuum
Four functions of microfilaments. Actin- globular protein
Form structural networks Bear tension Help support cell shape Gives outer cytoplasmic layer of a cell
maltose
Formed from glucose and glucose; found in malt sugar
Type of Ribosome Location Product Free Ribosomes Bound Ribosomes
Free Ribosomes - Location- Suspended in Cytosol. - Product- Enzymes Bound Ribosomes - Location- Attached to the outside of the endoplasmic reticulum or nuclear envelope. - Product- Lysosomes
What are the three major types of membrane receptors?
G protein-coupled receptor, G protein, GDP
What are the parts of the cell cycle?
G1, S, G2, M
In this reduction stage, the low-energy acid 1, 3-bisphosphoglycerate is reduced by electrons from NADPH to form the three-carbon sugar ___
G3P
What activates a G protein?
GTP
Why is the inner membrane of mitochondria highly folded?
Give the mitochondrial membrane a larger surface area, thus enhancing productivity of cellular respiration.
Who has more potential energy: water/glucose?
Glucose has more potential energy. Energy is stored in chemical bonds, and there are more bonds in C6H12O6 than in H2O.
What was the purpose of Griffith's studies?
He was attempting to develop a vaccine against pneumonia
Explain how hydrogen bonding contributes to water's high specific heat.
Heat is absorbed and released when hydrogen bonds form; therefore, a calorie of heat causes a relatively small change in the temperature of water because much of the heat is used to disrupt hydrogen bonds before water molecule can begin moving faster. Also, when the temperature of water drops slightly, many additional hydrogen bonds form, releasing a huge amount of energy in the form of heat
22. What are some evolutionary adaptations that allow xerophytes to survive in arid climates?
Highly reduced leaves resist excessive water loss; photosynthesis is mainly carried out in the stem. Fleshy stems store water for use during long dry periods. Some xerophytes have roots that are more than 20 m long, allowing them to acquire moisture at or near the water table. Crassulacean acid metabolism (CAM) is a specialized form of photosynthesis found in succulents of the family Crassulaceae and several other families. Because the leaves of CAM plants take in CO2, the stomata can remain closed during the day, when evaporative stresses are greater.
G1 checkpoint
If a cell receives the go-ahead signal at this checkpoint, the cell cycle will continue. It is regulated by the cyclin-CDk complexes.
Explain how the regeneration of RuBP is accomplished.
In a complex series of reactions, the carbon skeletons of five molecules of G3P are rearranged by the last steps of the Calvin cycle into three molecules of RuBP. To accomplish this, the cycle spends three more molecules of ATP. The RuBP is now prepared to receive CO2 again, and the cycle continues.
How does a hormone qualify as a long-distance signaling example?
In hormonal signaling in animals, also known as endocrine signaling, specialized cells release hormone molecules, which travel via the circulatory system to other parts of the body, where they reach target cells that can recognize and respond to the hormones.
What happens to the cytoplasmic concentration of calcium when it is used as a second messenger?
In response to a signal relayed by a signal transduction pathway, the cytosolic calcium level may rise, usually by a mechanism that releases Ca2+ from the cell's ER.
What is a major disadvantage of an electron microscope?
In the process of preparing the specimen, the cells are killed.
6. Water and solutes move through plant tissues in several ways, including between and around cell walls, and from cell to cell. Communication between plant cells is accomplished because the cytosol of adjacent cells is continuous. Describe and explain how this is accomplished by the plasmodesmata.
In the symplastic route, water and solutes move along the continuum of cytosol. After entering one cell, substances can move from cell to cell via plasmodesmata.
primary electron acceptor
In the thylakoid membrane of a chloroplast or in the membrane of some prokaryotes, the primary electron acceptor is a specialized molecule that shares the reaction center complex with a pair of chlorophyll a molecules and that accepts an electron from them
Distinguish between the leading and lagging stands during DNA replication
Leading strand: the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the madatory 5'-->3' direction Lagging strand: a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5'-->3' direction away from the replication fork
12. How is the surface area for absorption in roots greatly increased?
Many root cells have root hairs that dramatically increase the absorptive capacity of roots by increasing the membrane surface area.
Who performed the experiments that elucidated the correct mechanism of DNA replication?
Matthew Meselson and Franklin Stahl
E. Membrane Potential
Membrane potential is the difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances. It is established mainly through the pumping of H+ by proton pumps.
B. What is active transport?
Membrane traffic that involves pumping a solute across a membrane against its gradient. This type of transport requires work and the cell must expend energy (ATP is required).
How did Meselson and Stahl create "heavy" DNA for their experiments?
Meselson and Stahl cultured E. coli for several generations in a medium containing nucleotide precursors labeled with a heavy isotope of nitrogen
Another name for centrosomes? Role of centrioles?
Microtubule- organizing center. Centrioles help organize microtubule assembly in animal cells.
What are some of the things that will result in a final-form functional protein?
Modifications of a protein after translation include protein folding, chemical modification of amino acids, enzymatic removal or rearrangement of amino acids, or the formation of quaternary-level proteins as in the case of hemoglobin
multiple alleles (blood groups are an excellent example)
Most genes exist in more than two allelic forms, for example, ABO blood groups
What are the two electron carrier molecules that feed electrons into the electron transport system?
NADH and FADH2
Which organism did Beadle and Tatum use in their research? How did this organism's nutritional requirements facilitate this research?
Neurospora. Wild-type Neurospora has modest food requirements. It can grow in the laboratory on a simple solution of inorganic salts, glucose, and the vitamin biotin, and incorporated into agar, a support medium. From this minimal medium, the mold cells use their metabolic pathways to produce all other molecules they need. Beadle and Tatum identified mutants that could not survive on minimal medium, apparently because they were unable to synthesize certain essential molecules from the minimal ingredients.
Describe the nuclear envelope. How many layers is it? What connects the layers?
Nuclear Envelope- Double membrane enclosing the nucleus; perforated by pores; continuous with ER
What is the nuclear lamina? Nuclear matrix?
Nuclear Lamina- a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope. Nuclear matrix- a framework of fiber extending throughout the nuclear interior.
Why does oil float on top of water?
Oil molecules cannot form hydrogen bonds with water and thus behave hydrophobically, because there is a prevalence of relatively nonpolar covalent bonds—in this case, bonds between the carbon and hydrogen, which share electrons almost equally.
Explain the concept of reading frame.
On an mRNA, the reading frame is the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis
13. What are the roles of the apoplast and the symplast, and how does the Casparian strip relate to these structures?
Once inside the root cells, water can pass from cell to cell via diffusion. Water is also transported by way of the symplastic route, as well as the transmembrane route.
What are two benefits of multistep pathways.
One benefit of multiple steps is the possibility of greatly amplifying a signal. If some of the molecules in a pathway transmit the signal to numerous molecules at the next step in the series, the result can be a large number of activated molecules at the end of the pathway. Moreover, multistep pathways provide more opportunities for coordination and regulation than simpler systems do. This allows fine-tuning of the response, in both unicellular and multicellular organisms.
Explain what is meant by 5' and 3' ends of the nucleotide.
One end has a phosphate attached to the 5' carbon, and the other has a hydroxyl group on the 3' carbon
Cite two significant findings that resulted from the research of Beadle and Tatum.
One, that metabolic defects are linked to defective genes, and two, support for the one gene-one enzyme hypothesis
Explain how chemiosmosis is different in photosynthesis and cellular respiration.
Oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts. In mitochondria, the high-energy electrons dropped down the transport chain are extracted from organic molecules, whereas in chloroplasts, the source of electrons is water. Chloroplasts do not need molecules from food to make ATP; their photosystems capture light energy and use it to drive the electrons from water to the top of the transport chain. In other words, mitochondria use chemiosmosis to transfer chemical energy from food molecules to ATP, whereas chloroplasts transform light energy into chemical energy in ATP.
what is facilitated diffusion? is it passive or active?
PASSIVE transport aided by proteins
Figure 12.7!!!!
Pages 232-233
2. Competition for light, water, and nutrients is intense among the land plants. Plant success is generally related to photosynthesis, so evolution has resulted in many structural adaptations for efficiently acquiring light from the sun and CO2 from the air. As you read this section, focus on how this is accomplished. Let's look first at adaptations to increase light capture. How do plants reduce selfshading?
Plants reduce self-shading by undergoing self-pruning, where nonproductive leaves undergo programmed cell death.
Ways a protein may be denatured?
Possible examples of ways a protein may become denatured include alteration of pH, salt concentration, temperature, transfer from aqueous environment to nonpolar solvent, chemicals, and excessive heat.
d. Pressure Potential
Pressure potential is the physical pressure on a solution. Unlike solute potential, pressure potential can be positive or negative relative to atmospheric pressure.
Explain the difference between an allosteric activator and an allosteric inhibitor
The binding of an activator to a regulatory site stabilizes the shape that has functional active sites, whereas the binding of an inhibitor stabilizes the inactive form of the enzyme.
What happens in step 4?
The changes in the enzyme and G protein are only temporary because the G protein also functions as a GTPase enzyme—in other words, it then hydrolyzes its bound GTP to GDP. Now inactive again, the G protein leaves the enzyme, which returns to its original state. The G protein is now available for reuse. The GTPase function of the G protein allows the pathway to shut down rapidly when the signaling molecule is no longer present.
A. What is passive transport?
The diffusion of a substance across a biological membrane from a region of high concentration to a region of low concentration
What commonly held idea was rendered obsolete by the discovery of ribozymes?
The idea that all biological catalysts are proteins
What is the important relationship between the second messenger and protein kinase A?
The immediate effect of cAMP is usually the activation of a serine/threonine kinase called protein kinase A. The activated protein kinase A then phosphorylates various other proteins, depending on the cell type.
M checkpoint
The kinetochores must all be attached to spindle fibers during metaphase. This will activate an enzyme (separase), which allows the sister chromatids to separate and anaphase will proceed
light reactions
The light reactions are the steps of photosynthesis that convert solar energy to chemical energy. 1. Water is split, providing a source of electrons and protons and giving off O2 as a by-product. 2. Light absorbed by chlorophyll drives a transfer of the electrons and hydrogen ions from water to an acceptor called NADP+, where they are temporarily stored. 3. The light reactions use solar power to reduce NADP+ to NADPH by adding a pair of electrons along with an H+. 4. The light reactions also generate ATP, using chemiosmosis to power the addition of a phosphate group to ADP, a process called photophosphorylation
ionic bond
The lone valence electron of a sodium atom is transferred to join the 7 valence electrons of a chlorine atom. Each resulting ion has a completed valence shell. An ionic bond can form between the oppositely charged ions, forming sodium chloride, NaCl
Besides packaging secretory proteins into transport vesicles, what is another major function of the rough ER?
The membrane keeps them separate from proteins that are produced by free ribosomes and will remain in the cytosol. Rough ER is a membrane factory for the cell; it grows in place by adding membrane proteins and phospholipids to its own membrane.
What is the consequence of alternative splicing of identical mRNA transcripts?
The number of different protein products an organism produces can be much greater than its number of genes
Where are the gametes of an animal produced?
The only cells of the human body not produced by mitosis are the gametes, which develop from specialized cells called germ cells in the gonads—ovaries in females and testes in males.
random fertilization
The random nature of fertilization adds to the genetic variation arising from meiosis. In humans, each male and female gamete represents one of about 8.4 million possible chromosome combinations due to independent assortment. The fusion of a male gamete with a female gamete during fertilization will produce a zygote with any of about 70 trillion diploid combinations.
Explain how using pea plants allowed Mendel to control mating; that is, how did this approach let Mendel be positive about the exact characteristics of each parent?
The reproductive organs of a pea plant are in its flowers, and each pea flower has both pollen-producing organs (stamens) and an egg-bearing organ (carpel).To achieve cross-pollination (fertilization between different plants), Mendel removed the immature stamens of a plant before they produced pollen and then dusted pollen from another plant onto the altered flowers. Each resulting zygote then developed into a plant embryo encased in a seed (pea). Mendel could thus always be sure of the parentage of new seeds.
X inactivation maintains the proper gene dosage. How is the X chromosome inactivated?
The selection of which X chromosome will form the Barr body occurs randomly and independently in each embryonic cell present at the time of X inactivation.
Snurps band together in little snurp groups to form spliceosomes. How do spliceosomes work?
The spliceosome interacts with certain sites along an intron, releasing the intron, which is rapidly degraded, and joining together two exons that flanked the intron
diffusion
The spontaneous movement of a substance down its concentration gradient, from a region where it is more concentrated to a region where it is less concentrated
What are the symptoms of phenylketonuria (PKU)? How is newborn screening used to identify children with this disorder?
The symptoms of phenylketonuria include an inability to metabolize the amino acid phenylalanine, causing severe mental intellectual disability. Some genetic disorders, including phenylketonuria, can be detected at birth by simple biochemical tests that are now routinely performed in most hospitals in the United States
23. What is translocation?
The transport of products of photosynthesis
20. What are stomata and how do they help regulate the rate of transpiration?
The waxy cuticle limits water loss through the remaining surface of the leaf. Each stoma is flanked by a pair of guard cells. Guard cells control the diameter of the stoma by changing shape, thereby widening or narrowing the gap between the guard cell pair. Under the same environmental conditions, the amount of water lost by a leaf depends largely on the number of stomata and the average size of their pores.
What do we mean when we say the two strands of DNA are antiparallel?
Their subunits run in opposite directions
Do linked genes sort independently?
These genes do not sort independently, but rather are transmitted as a unit. It is important to note that as Morgan's experiments illustrated, some mechanism (later discovered to be "crossing over") occasionally breaks the linkage between specific alleles of genes on the same chromosome.
Explain how the electron transport chain is utilized in oxidative phosphorylation.
This mode of ATP synthesis is powered by the redox reactions of the electron transport chain.
What are the components of the mitotic spindle? What is the source of these components?
This structure consists of fibers made of microtubules and associated proteins. While the mitotic spindle assembles, the other microtubules of the cytoskeleton partially disassemble, providing the material used to construct the spindle. The spindle microtubules elongate (polymerize) by incorporating more subunits of the protein tubulin and shorten (depolymerize) by losing subunits. The source of these components is the cytoplasm during prophase.
anchorage dependence
To divide, they must be attached to a substratum, such as the inside of a culture jar or the extracellular matrix of a tissue
What is the semiconservative model of replication?
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand
How does a somatic cell compare to a gamete in terms of chromosome number?
Unlike somatic cells, gametes contain a single set of chromosomes. Such cells are called haploid cells, and each has a haploid number of chromosomes (n). For humans, the haploid number is 23.
Explain a fatty acid chain.
Unsaturated fatty acids have one or more double bond, with one fewer hydrogen atom on each double- bonded carbon. Nearly all double bonds in naturally occurring fatty acids are cis bonds, which cause a kink in the hydrocarbon chain whenever they occur.
How is the cell plate formed? What is the source of the material for the cell plate?
Vesicles derived from the Golgi apparatus move along microtubules to the middle of the cell, where they coalesce, producing a cell plate
Distinguish between the virulent and nonvirulent strains of Streptococcus pneumoniae studied by Frederick Griffith
Virulent strains are pathogenic (disease-causing), whereas the non virulent strains are non pathogenic (harmless)
G2 checkpoint
When sufficient MPF accumulates, the G2 checkpoint is passed, and mitosis is promoted.
What happens in step 2?
When the appropriate signaling molecule binds to the extracellular side of the receptor, the receptor is activated and changes shape. Its cytoplasmic side then binds an inactive G protein, causing a GTP to displace the GDP. This activates the G protein. See page 211 of text for the labeled figure.
Explain the binding of the ligand to the receptor.
When the ligand binds to the receptor and the gate opens, specific ions can flow through the channel and rapidly change the concentration of that particular ion inside the cell. This change may directly affect the activity of the cell in some way. See page 213 of text for the labeled figure.
Summarize how water's high specific heat contributes to the moderation of temperature. How is this property important to life?
With a high specific heat, a large body of water can absorb and store a huge amount of heat from the sun in the daytime and during summer while warming up only a few degrees. As this water generally cools during the night and during winter, it warms the air, contributing to milder climates in coastal regions.
What is the TATA box, and how did it get its name?
a DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex. Its name is from the thymine (T) and adenine (A) that make it up
chromosome theory of inheritance
a basic principle in biology stating that genes are located at specific positions (loci) on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patters
genome
a cell's endowment of DNA, its genetic information
How can a nucleotide-pair substitution result in a silent mutation?
a change in the nucleotide pair may transform one codon into another that is translated into the same amino acid. This mutation has no observable effect on the phenotype.
sex-linked gene
a gene located on either sex chromosome. Most sex-linked genes are on the X chromosome and show distinctive patterns of inheritance; there are very few genes on the Y chromome
linkage map
a genetic map based on the frequencies between markers during crossing over of homologous chromosomes
action spectrum
a graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process
What is a polyribosome?
a group of several ribosomes attached to, and translating, the same messenger RNA molecule
benign tumor
a mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor's origin
products
a material resulting from a chemical reaction
signal transduction
a membrane protein (receptor) may bind w/a specific shape that fits the shape of a chemical messenger. the external messenger(signaling molecule) may cause a shape change in the protein that relays the message to the inside of the cell, usually by binding to a cytoplasmic protein.
photorespiration
a metabolic process, the plant consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco
What is the purpose of meiosis?
a modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell, producing gametes, and introducing genetic variability.
ligand
a molecule that binds specifically to another molecule, usually a larger one
polar molecule
a molecule whose overall charge is unevenly distributed
What are frameshift mutations?
a mutation occuring when nucleotides are inserted in or deleted from a gene and the number inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons
synaptic signaling
a nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell; animal nervous system
Cytoskeleton
a network of fibers extending throughout the cytoplasm, organize the structures and activities of the cells. Three functions: Support, Motility, and regulation. Three fibers that make up cytoskeleton: microtubules, microfilaments, intermediate filaments.
hydrogen bond
a noncovalent attraction between the hydrogen of one molecule with the oxygen or nitrogen of another molecule
What is the G_0 phase?
a nondividing state occupied by cells that have left the cell cycle, sometimes reversibly, such as liver cells
What is an anticodon?
a nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule
homologous chromosomes
a pair of chromosomes of the same length, centromere position, and staining pattern
What are homologs (homologous chromosomes)?
a pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci
fermentation
a partial degradation of sugars or other organic fuel that occurs without the use of oxygen
dipeptide
a plymer of two amino acids linked by a peptide bond
What is a transcription unit?
a region of DNA that is transcribed into an RNA molecule
gamete
a reproductive cell
monomer
a smaller molecule that serves as the building blocks of polymers
amino
acts as a base
DNA polymerase
adds DNA nucleotides to new strands; removes RNA primer and replaces with DNA; fills the gap left after nuclease excises damaged segments of the DNA strand
What are the four nitrogenous bases found in DNA?
adenine, guanine, cytosine, thymine
What are the four nitrogenous bases found in RNA?
adenine, guanine, cytosine, uracil
19. Leaves generally have large surface areas and high surface-to-volume ratios. Give an advantage and disadvantage of these traits.
advantage: Enhances light absorption for photosynthesis. disadvantage: Increases water loss by way of the stomata.
heterotroph
an organism that obtains organic food molecules by eating other organisms or substances derived from them
autotroph
an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Use energy from the sun or oxidation of inorganic substances to make organic molecules from inorganic ones
Which reaction builds up larger molecules?
anabolic
Which reaction consumes energy?
anabolic
Which reaction is considered "uphill"?
anabolic
What is a somatic cell?
any cell in a multicellular organism except a sperm or egg or their precursors
ligand
any molecule that binds specifically to a receptor site of another molecule.
cofactor
any nonprotein molecule/ion that is required for the proper functioning of an enzyme; can be permanently bound to the active site, along with the substrate, during catalysis
Describe one example Garrod used to illustrate his hypothesis.
as one example the hereditary condition called alkaptonuria. In this disorder, the urine is black because it contains the chemical alkapton, which darkens upon exposure to air. Garrod reasoned that most people have an enzyme that metabolizes alkapton, whereas people with alkaptonuria have inherited an inability to make that enzyme
What type of reproduction will result in genetically identical offspring?
asexual reproduction
light-harvesting complex
associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem
kinetic energy
associated with the relative motion of objects
electronegativity
attraction of a particular atom for the electrons of a covalent bond
What molecules make up the "rungs"?
base pairs joined by hydrogen bonding
methyl
can affect gene expression; CH3
sulfhydryl
can form cross-links that stabilize protein structure
The large molecules of all living things fall into just four main classes. Name them.
carbohydrates, lipids, proteins, nucleic acids
Four main classes that all large molecules of living things fall into.
carbohydrates, proteins, lipids, nucleic acids
What are the three classes that are called macromolecules?
carbohydrates, proteins, nucleic acids
enzymatic activity
carries out sequential steps of a metabolic pathway
What type of reaction is cellular respiration?
catabolic
What type of reaction is photosynthesis?
catabolic
Which reaction breaks down molecules?
catabolic
Which reaction releases energy?
catabolic
Which reaction requires enzymes to catalyze reactions?
catabolic, anabolic
aquaporins
channel proteins; allows entry of up to 3 billion water molecules per second, passing single file through its central channel which fits ten at a time.
what are the 2 forces that drive the diffusion of ions across the membrane?
chemical and electrical
What are the three main kinds of work that a cell does?
chemical, transport, mechanical
Besides mitochondrial DNA, what other organelle has its own genes? (known as extranuclear genes)
chloroplasts or mitochondria
how does cholesterol affect membrane fluidity?
cholesterol restrains phospholipid fluid at higher temperatures making membranes less fluid.
secondary (a helix, b pleated sheet)
coils and folds resulting from the hydrogen bonds between the repeating constituents of the polypeptide backbone a-helix: delicate coil held together by hydrogen bonding between every fourth amino acids beta pleated sheet: two or more strands of the polypeptide chain lying side by side, connected by hydrogen bonds between parts of the two parallel polypeptide backbone
isomer
compounds that have the same number of atoms of the same elements but different structures and therefore different properties
protein attachment to cytoskeleton and ECM
coordinate extracellular and intracellular exchanges.
Arrange these bonds from strongest to weakest.
covalent ionic hydrogen van der Waals
dihybrid cross
cross between two organisms that are each heterozygous for both of the characters being followed
monohybrid cross
cross between two organisms that are heterozygous for the character being followed
What occurs during meiosis between homologous chromosomes, causing the linked genes to become unlinked?
crossing over
What are the two common second messengers?
cyclic AMP (cAMP) and calcium ions (Ca2+)
mRNA
description: messenger RNA, single stranded function: carries genetic material from the DNA to the protein-synthesizing machinery of the cell
How is the arrangement of chromosomes different from metaphase of mitosis?
during mitosis, individual chromosomes line up at the metaphase plate; during meiosis, pairs of homologous chromosomes line up at the metaphase plate
Mendel's law of independent assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
law of independent assortment
each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes
For an exergonic reaction, is deltaG negative of positive?
exergonic reaction proceeds with a net release of free energy; and b/c the chemical mixture loses free energy, deltaG is negative
Is cellular respiration an endergonic or an exergonic reaction? What is its deltaG?
exergonic reaction; deltaG=-686 kcal/mol
macromolecule
extremely large on the molecular side, sometimes consisting of thousands of atoms
What three organic molecules are often utilized to make ATP by cellular respiration?
fats, proteins, sucrose, starch
Name some forms of lipids.
fats, waxes, oils, phospholipids, and steroids
Mendel's Second concept
for each character, an organism inherits two copies of a gene, one from each parent
sucrose
formed from glucose and fructose; found in table sugar
lactose
formed from glucose and galactose; found in milk
How is a karyotype prepared?
from isolated somatic cells, which are treated with a drug to stimulate mitosis and then grown in culture for several days. Cells arrested in metaphase, when chromosomes are most highly condensed, are stained and then viewed with a microscope equipped with a digital camera. A photograph of the chromosomes is displayed on a computer monitor, and the images of the chromosomes are arranged into pairs according to their appearance.
enzymes
function: accelerate chemical reactions example: maltase, pepsin, sucrase
motor and contractile proteins
function: movement example: actin, myosin
receptor proteins
function: reponse of cell to chemical stimuli example: G protein-coupled receptors; tyrosine kinase receptors
linked genes
genes located close enough together on a chromosome that they tend to be inherited together
fructose
glucose + fructose form sucrose
The carbohydrate produced directly from the Calvin cycle is not glucose, but the three-carbon compound ___________ _-_________ (G3P). Each turn of the Calvin cycle fixes one molecule of CO2; therefore, it will take _ turns of the Calvin cycle to net one G3P.
glyceraldehyde 3-phosphate; 3
What are the building blocks of fats? Use figure 5.10.
glycerol and fatty acids; See page 75 of text for the labeled figure.
egg cell
haploid
gamete.
haploid
sex cell
haploid
sperm
haploid
starch
has 1-4 B-glucose linkages
carboxyl
has acidic properties; -COOH
Mendel's Third concept
if two alleles at a locus differ, then one, the dominant allele, determines the organism's appearance; the other, the recessive allele, has no noticeable effect on the organism's appearance
karyotype
images of the chromosomes that are arranged in pairs, starting with the longest chromosomes
There are two divisions in meiosis. What will separate in the first division in meiosis I?
in meiosis I, homologous chromosomes seperate
What are the three ways that sexually reproducing organisms bring about new alleles by changes in DNA?
independent assortment of chromosomes, crossing over, random fertilization
atomic number
indicates the number of protons in the nucleus of a specific element, as well as the number of electrons in an electrically neutral atom
How is deltaG affected by the enzyme?
it cannot make an endergonic reaction exergonic
why doesnt the plant cell burst?
it has a cell wall.
Why is oxygen the ultimate electron acceptor?
it is extremely electronegative
What effect does an enzyme have on Ea?
it lowers the Ea barrier
phosphate
key component of ATP
flaccid
limp
G protein
loosely attached to the cytoplasmic side of the membrane, the G protein functions as a molecular switch that is either on or off, depending on which of two guanine nucleotides is attached, GDP or GTP-hence the term G protein (GTP, guanosine triphosphate, similar to ATP)
When compounds lose electrons, they ____ energy; when compounds gain electrons, they ____ energy.
lose; gain
Each member of the electron transport chain is _____ in free energy than the preceding member of the chain, but higher in _______________. The molecule at zero free energy, which is ______, is lowest of all the molecules in free energy and highest in electronegativity.
lower; electronegativity; oxygen
What are the three disaccharides that have the formula C12H22O11?
maltose, sucrose, and lactose
By what process are eggs formed?
meiosis
By what process are gametes produced?
meiosis
Which process reduces chromosome number of daughter cells?
meiosis
During which division is the chromosome number reduced?
meiosis I
carbon dioxide
molecule: yes compound: yes molecular formula: CO2
water
molecule: yes compound: yes molecular formula: H2O
What controls the cell cycle?
molecules present in the cytoplasm during the S or M phase control the progression to those phases
van der Waals interactions
molecules with nonpolar covalent bonds may have positively and negatively charged ions. Electrons are not always symmetrically distributed in such a molecule and may accumulate by chance in one part of the molecule, resulting in positive and negative charges. These ever-changing regions of positive and negative charge enable all atoms and molecules to stick to one another. These van der Waals interactions are individually weak, and occur only when atoms and molecules are very close together, but can be powerful when many such interactions occur simultaneously.
What are the monomers of all carbohydrates?
monosaccharides, or simple sugars
In what body systems are ligand-gated ion channels and voltage-gated channels of particular importance?
nervous system
How many times do the chromosomes duplicate?
none
Difference between a nonsense and missense mutation?
nonsense: changes an amino acids codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein missense: a nucleotide-pair substitution that results in a codon that codes for a different amino acid
autosome
not directly involved in determining sex; not a sex chromosome; 22 in humans
nonpolar covalent bond
occur between atoms of the same element, the electrons are shared equally, and therefore their polarity is neutral
A number of genes will cause a variation in phenotype, depending on whether the gene came from the father or the mother. This variation occurs because of genomic imprinting. Explain genomic imprinting.
occurs during gamete formation and results in the silencing of a particular allele of certain genes. B/c these genes are imprinted differently in sperm and eggs, the zygote expresses only one allele of an imprinted gene that is inherited from either the female or male parent. The imprints are then transmitted to all body cells during development.
spontaneous process
occurs without an overall input of energy; is energetically favaorable
Name unsaturated fats.
olive oil, cod liver oil, plant or fish fats
polar covalent bond
one atom is bonded to a more electronegative atom, and the electrons of the bond are not shared equally
chromatid
one of two identical joined copies of the original chromosome
Formula for catabolic degradation of glucose by cellular respiration.
organic compounds + oxygen --> carbon dioxide + water + energy
Quantitative variation usually indicates what?
polygenic inheritance
cation
positively charged ion
In eukaryotes, what is the pre-mRNA called?
primary transcipt
What are the four levels of protein structure?
primary, secondary, tertiary and quaternary
Number of chromosomes between prokaryotic and eukaryotic cells?
prokaryotic cells have a singular circular chromosome; eukaryotic cells have distinct linear chromosomes (the number varies by species in eukaryotes)
repair enzymes
proofread and repair DNA
Synapsis and crossing over are unique to meiosis. During what specific phase do these occur?
prophase I
When does crossing over occur in meiosis?
prophase I
Adenine
purine; found in both DNA and RNA
dynamic equilibrium
reactions are still going on, but with no net effect on the concentrations of reactants and products. Equilibrium does not mean that the reactants and products are equal in the concentration, but only that their concentrations have stabilized at a particular ratio
What are the three stages of a signal transduction pathway?
reception, transduction, response
What are the colors of the visible spectrum?
red, orange, yellow, green, blue, indigo, violet
electron shells
represented as concentric circles in diagrams, electron shells represent the average distance from the nucleus and energy level of electrons circling the nucleus of an atom
What are the three key roles of cell division?
reproduction, growth and development, tissue removal
trace element
required by an organism in only minute quantities; some such as iron (Fe) are required by all forms of life, where others like iodine (I) are required only by certain species
sex chromosome
responsible for determine the sex of an individual; 1 in humans
What enzyme is responsible for carbon fixation in the Calvin cycle, and possibly the most abundant protein on Earth?
rubisco
F2 generation
second filial generation
What is the function of the electron transport chain in cellular respiration?
shuttles electrons down a series of redox reactions that release energy used to make ATP
cystic electron flow
similar to the first forms of photosynthesis to evolve; no water is split, there is no production of NADPH and there is no release of oxygen
What type is the RNA in a snRNP?
small nuclear RNA
Explain how the splice sites are recognized.
snRNAs, part of the spliceosome complex, recognize specific nucleotide sequences on the intron and catalyze the process of intron removal. This is an excellent example of catalytic function in snRNA
What two types of molecules make up a snurp?
snRNPs are made up of RNA and protein molecules
What are snRNPs?
snRNPs are small nuclear ribonucleoproteins
cell-cell recognition
some glycoproteins serve as identification tags that are specifically recognized by membrane proteins of other cells.
What are the events of prophase I?
synapsis: The pairing and physical connection of duplicated homologous chromosomes during prophase I of meiosis crossing over: The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis chiasmata: The X-shaped, microscopically visible region where crossing over has occurred earlier in prophase I between homologous nonsister chromatids. Chiasmata become visible after synapsis ends, with the two homologs remaining associated due to sister chromatid cohesion.
primase
synthesizes RNA primer
Why are cancer cells immortal even though most body cells have a limited life span?
telomerase activity in cancerous somatic cells, suggesting that its ability to stabilize telomere length may allow these cancer cells to persist
DNA is double-stranded, but for each protein, only one of these two strands is used to produce an mRNA transcript. What is the coding strand called?
template strand
pleiotropy
the ability of a single gene to have multiple effects. In humans, pleiotropic alleles are responsible for multiple symptoms associated with certain hereditary diseases, such as cystic fibrosis and sickle-cell disease.
reduction
the addition of electrons to another substance
activation energy (Ea)
the amount of energy that reactants must absorb before a chemical reaction will start; aka free energy of activation
calorie
the amount of heat it takes to raise the temperature of 1 g of water by 1degree C, also the amount of heat that 1 g of water releases when it cools by 1degree C
specific heat
the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1degree C
energy
the capacity to cause change-for instance, by doing work
endocytosis
the cell takes in molecules and particular matter by forming new vesicles from the plasma membrane
denaturation
the changing of a protein during which the protein unravels and loses its native shape because the weak chemical bonds and interactions within a protein have been destroyed
What comprises a transcription initiation complex?
the completed assembly of transcription factors and RNA polymerase bound to a promoter
chromatin
the complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers
passive transport
the diffusion of a substance across a membrane without the use of energy from the cell
osmosis
the diffusion of water across a selectively permeable membrane.
solvent
the dissolving agent of a solution
What determines the chemical behavior of an atom?
the distribution of electrons in the atom's electron shells
cytokinesis
the division of the cytoplasm
What are the monomers of DNA and RNA and of proteins?
the four types of nucleotides, which differ in their nitrogenous bases Amino acids
asexual reproduction
the generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts); in most cases, the offspring are genetically identical to the parent
meiosis
the human body produces gametes by a variation of cell division
cell cycle
the life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells
oxidation
the loss of electrons from one substance
introns
the noncoding segments of nucleic acid that lie between coding regions, also called intervening sequences
radioactive isotope
the nucleus decays spontaneously, giving off particles and energy; when the decay leads to a change in the number of protons, it transforms the atom to an atom of a different element
cohesion
the phenomenon of the collective hydrogen bonds holding water together
incomplete dominance.
the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele; neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere between those of the two parental varieties
transcription
the synthesis of RNA using a DNA template
translation
the synthesis of a polypeptide using the genetic info encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids
reception
the target cell's detection of a signaling molecule coming from outside the cell. A chemical signal is "detected" when the signaling molecule binds to a receptor protein located at the cell's surface or inside the cell
response
the third stage of cell signaling, the transduced signal triggers a specific cellular response. The response may be almost any imaginable cellular activity
metabolism
the totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism
evaporation
the transformation of a liquid to a gas
law of segregation
the two alleles for each gene separate during gamete formation
multiplication rule
to determine this probability, we multiply the probability of one event by the probability of the other event. (For example, by the multiplication rule, the probability that both coins will land heads up is ½ × ½ = ¼)
How were Neurospora spores treated to increase the mutation rate?
treated with X-rays to increase the mutation rate
T of F: When two monomers are joined, a molecule of water is always removed
true
ligand-gated ion channel receptor
type of membrane receptor containing a region that can act as a "gate" when the receptor changes shape
map unit
unit of measurement of the distance between genes (equivalent to a 1% recombination frequency)
What is a trans fat? Why should you limit them in your diet?
unsaturated fat with a trans double bond; should be limited in your diet because they have been found to contribute to atherosclerosis, a cardiovascular disease caused by plaque buildup within the walls of blood vessels.
Helicase
untwists and separates strands
turgid
very firm
What compound is the source of electrons for linear electron flow?
water
GDP
when GDP is bound to the G protein, the G protein is inactive. The receptor and G protein work together with another protein, usually an enzyme
ions
when a signaling molecule binds as a ligand to the receptor protein, the gate opens or closes, allowing/blocking the flow of specific ions, such as Na+ or Ca2+, through a channel in the receptor
exocytosis
when the cell secretes certain molecules by the fusion of vesicles with the plasma membrane.
How many times more acidic is a pH of 3 compared to a pH of 5?
10^2 = 100
How many times more basic is a pH of 12 compared to a pH of 8?
10^4 = 10,000
How many different aminoacyl-tRNA synthetases are there?
20
How many chromosomes in a human gamete?
23
Given that the DNA of a certain fly species consists of 27.3% adenine and 22.5% guanine, use Chargaff's rules to deduce the percentages of thymine and cytosine.
27.3% thymine 22.5% cytosin
What is the atomic number of helium and its atomic mass?
2;4
How many nucleotides are required to code for these 20 amino acids?
3
S
"synthesis"; when the chromosomes duplicate
G protein-coupled receptor
(GPCR) a cell-surface transmembrane receptor that works with the help of a G protein
The net production of one G3P requires _ molecules of ATP and _ molecules of NADPH.
9;6
amniocentesis
1. A sample of amniotic fluid can be taken starting at the fourteenth to sixteenth week of pregnancy. 2. Biochemical and genetic tests can be performed immediately on the amniotic fluid or later on the cultured cell. 3. Fetal cells must be cultured for several weeks to obtain sufficient numbers for karyotyping.
CVS
1. A sample of chorionic villus tissue can be taken as early as the eighth to tenth week of pregnancy. 2. Karyotyping and biochemical and genetic tests can be performed on the fetal cells immediately, providing results within a day or so.
Summarize the events of initiation
1. A small ribosomal subunit binds to a molecule of mRNA. (In a bacterial cell, the mRNA binding site on this subunit recognizes a specific nucleotide sequence on the mRNA just upstream of the start codon.) 2. An initiator tRNA, within the anticodon UAC, base-pairs with the start codon, AUG. 3. This tRNA carries the amino acid methionine (Met). 4. The arrival of a large ribosomal subunit completes the initiative complex. 5. Proteins called initiation factors are required to bring all the translation components together. 6. Hydrolysis of GTP provides the energy for the assembly. 7. The initiator tRNA is in the P site; the A site is available to the tRNA bearing the next amino acid. See page 340 in text for the labeled figure.
What are three properties of RNA that allow it to function as an enzyme?
1. Because RNA is single-stranded, a region of an RNA molecule may base-pair with a complementary region elsewhere in the same molecule, which gives the molecule a particular three-dimensional structure. A specific structure is essential to the catalytic function of ribozymes, just as it is for enzymatic proteins. 2. Like certain amino acids in an enzymatic protein, some of the bases in RNA contain functional groups that may participate in catalysis. 3. This ability of RNA to hydrogen-bond with other nucleic acid molecules (either RNA or DNA) adds specificity to its catalytic activity.
Describe at least three types of post-translational modifications.
1. Certain amino acids may be chemically modified by the attachment of sugars, lipids, phosphate groups, or other additions. 2. Enzymes may remove one or more amino acids from the leading (amino) end of the polypeptide chain. 3. Two or more polypeptides that are synthesized separately may come together, becoming the subunits of a protein that has quaternary structure.
What are four characteristics of Down syndrome?
1. Characteristic facial features 2. Short stature 3. Correctable heart defects 4. Developmental delays
Describe the action of different types of chemical mutagens.
1. Chemicals that are similar to normal DNA nucleotides but that pair incorrectly during DNA replication 2. Chemicals that interfere with correct DNA replication by inserting themselves into the DNA and distorting the double helix 3. Chemicals that cause chemical changes in bases that change their pairing properties
Steps to synthesis of a new strand
1. Helicase unwinds the parental double helix 2. Molecules of a single-stranded binding protein stabilize the unwound template strands 3. The leading strand is synthesized continuously in the 5'-->3' direction by DNA polymerase III after being primed by primase 4. Primase begins synthesis of the RNA primer for the lagging strand 5. DNA polymerase III synthesizes discontinuously the lagging stand in the 5'-->3' direction 6. DNA polymerase I removes all the RNA primer sections and replaces them with DNA nucleotides 7. The replacement of the primer with DNA leaves the new DNA nucleotides with a free 3' end. DNA ligase joins the free 3' end to its adjacent 5' end, forming a continuous and unbroken strand of DNA on both the leading and lagging stands.
Explain the three key events in the C4 pathway.
1. In mesophyll cells, the enzyme PEP carboxylase adds carbon dioxide to PEP. 2. A four-carbon compound conveys the atoms of the CO2 into a bundle-sheath cell via plasmodesmata. 3. In bundle-sheath cells, CO2 is released and enters the Calvin cycle.
Describe four ways that chemiosmosis is similar in photosynthesis and cellular respiration.
1. In photosynthesis and cellular respiration, an electron transport chain assembled in a membrane pumps protons across the membrane as electrons are passed through a series of carriers that are progressively more electronegative. 2. In photosynthesis and cellular respiration, ATP synthase complex couples the diffusion of hydrogen ions down their gradient to the phosphorylation of ADP. 3. The inner membrane of the mitochondrion pumps protons from the mitochondrial matrix out to the intermembrane space, which then serves as a reservoir of hydrogen ions. The thylakoid membrane of the chloroplast pumps protons from the stroma into the thylakoid space (interior of the thylakoid), which functions as the H+reservoir. 4. In the mitochondrion, protons diffuse down their concentration gradient from the inter- membrane space through ATP synthase to the matrix, driving ATP synthesis. In the chloroplast, ATP is synthesized as the hydrogen ions diffuse from the thylakoid space back to the stroma through ATP synthase complexes, whose catalytic knobs are on the stroma side of the membrane.
25. Label the following diagram, describing pressure flow in a sieve tube. See page 795 of your text for the labeled figure.
1. Loading of sugar (green dots) into the sieve tube at the source reduces water potential inside the sieve-tube elements. This causes the tube to take up water by osmosis. 2. This uptake of water generates a positive pressure that forces the sap to flow along the tube. 3. The pressure is relieved by the unloading of sugar and the consequent loss of water at the sink. 4. In leaf-to-root translocation, xylem recycles water from sink to source
Endomembrane system function to digest a cellular component.
1. Nuclear envelope is connected to rough ER, which is also continuous with smooth ER. 2. Membrane and proteins produced by the ER flow in the in the form of transport vesicles to the Goligi. 3. Golgi pinches off transport vesicles and other vesicles that give rise to lysosomes, other types of specialized vesicles, and vacuoles. 4. Lysosome is available for fusion with another vesicle for digestion. 5. Transport vesicle carries proteins to plasma membrane for secretion. 6. Plasma membrane expands by fusion of vesicles; proteins are secreted from cell.
List three important facts about the promoter here.
1. Promoter of a gene includes within it the transcription start point. 2. Promoter typically extends several dozen of more nucleotide pairs upstream from the start point. 3. RNA polymerase binds in a precise location and orientation on the promoter
Three functions/ materials of Central vacuoles.
1. Proteins stockpiles in vacuoles of storage cells in seeds. 2. Main repository of inorganic ions, such as potassium and chloride. 1. Disposal sites for metabolic by-products.
three ways in which RNA differs from DNA
1. RNA contains ribose instead of deoxyribose as its sugar. 2. RNA has the nitrogenous base uracil rather than thymine. 3. An RNA molecule usually consists of a single strand rather than DNA's double strand
List and describe three major functions of the smooth ER.
1. Synthesis of lipids, oils, phospholipids, and steroids. 2. Other enzymes of smooth ER help detoxify drugs and poisons. 3. Metabolism of carbohydrates.
How does a bacteriophage destroy a bacteria cell?
1. The T4 phage uses its tail fibers to bind to specific receptor sites on the outer surface of an E. coli cell. 2. Sheath of the tail contracts, injecting the phage DNA into the cell and leaving an empty capsid outside 3. Cell's DNA is hydrolyzed 4. Phage DNA directs production of phage proteins and copies the phage genome by host and viral enzymes, using components w/in the cell 5. Three separate sets of proteins self-assemble to form phage head, tail, and tail fibers 6. Phage genome is packaged inside the capsid as the head forms 7. Phage directs production of an enzyme that damages the bacteria cell wall, allowing fluid to enter 8. The cell swells, burst, releasing 100-200 phage particles
Now, summarize the events of elongation
1. The anticodon of an incoming aminoacyl tRNA base-pairs with the complementary mRNA codon in the A site. 2. Hydrolysis of GTP increases the accuracy and efficiency of this step. 3. An rRNA molecule of the large ribosomal subunit catalyzes the formation of a peptide bond between the amino group of the new amino acid in the A site and the carboxyl end of the growing polypeptide in the P site. 4. This step removes the polypeptide from the tRNA in the P site and attaches it to the amino acid on the tRNA in the A site. 5. The ribosome translocates the tRNA in the A site to the P site. At the same time, the empty tRNA in the P site is moved to the E site, where it is released. 6. The mRNA moves along with its bound tRNAs, bringing the next codon to be translated into the A site. See page 341 in text for the labeled figure.
Calvin cycle
1. The cycle begins by incorporating CO2 from the air into organic molecules already present in the chloroplast. This initial incorporation of carbon into organic compounds is known as carbon fixation. 2. The Calvin cycle then reduces the fixed carbon to carbohydrate by the addition of electrons. The reducing power is provided by NADPH, which acquired its cargo of electrons in the light reactions. 3. To convert CO2 to carbohydrate, the Calvin cycle also requires chemical energy in the form of ATP, which is also generated by the light reactions.
What are three important functions of the 5' cap and poly-A tail?
1. They seems to facilitate the export of mature mRNA from the nucleus 2. They help protect the mRNA from degradation by hydrolytic enzymes 3. They help ribosomes attach to the 5' end of the mRNA once the mRNA reaches the cytoplasm
Describe two important ways in which bacterial and eukaryotic gene expression differ.
1. Transcription is terminated differently in bacteria and eukaryotes. 2. In the absence of a nucleus, bacterial cells can simultaneously transcribe and translate the same gene, and the newly made protein can quickly diffuse to its site of function. The eukaryotic cell's nuclear envelope segregates transcription from translation and provides a compartment for extensive RNA processing. This processing state includes additional steps whose regulation can help coordinate the eukaryotic cell's elaborate activities.
List the three places in the light reactions where a proton-motive force is generated by increasing the concentration of H+in the stroma.
1. Water is split by photosystem II on the side of the membrane facing the thylakoid space 2. As plastoquinone (Pq), a mobile carrier, transfers electrons to the cytochrome complex, four protons are translocated across the membrane into the thylakoid space 3. A hydrogen ion is removed from the stroma when it is taken up by NADP+.
How many chromosomes are in each cell at the end of the first meiotic division? Are the resultant daughter cells haploid, or diploid?
3; haploid
Each NADH can form a maximum of how many ATP molecules? FADH2?
3;2
An event that is certain to occur has a probability of _, while an event that is certain not to occur has a probability of _.
1; 0
Why can extremes of pH or very high temperatures affect enzyme activity?
3D structures of proteins are sensitive to their environment. As a consequence, each enzyme works better under some conditions than other conditions, because these optimal conditions favor the most active shape for their enzyme molecule.
How many daughter cells are formed?
4
How many DNA molecules are in each of your somatic cells?
46
How many chromosomes are in a human somatic cell?
46
Here is a short DNA template. Below it, assemble the complementary mRNA strand. 3'A C G A C C A G T A A A 5' How many codons are there above?
5' U G C U G G U C A U U U 3' 4
What is the direction of synthesis of the new strand?
5'-->3' direction
Acid precipitation is increasing. What is the pH of uncontaminated rain?
5.6
Of the 64 possible codons, how many code for amino acids?
61
So, the language of DNA is a triplet code. How many unique triplets exist?
64
formula for photosynthesis
6CO2 + 6H2O + light energy --> C6H12O6 + 6O2
photosynthesis equation
6CO2 + 6H2O-->C6H12O6 + 6O2
liver cell
diploid
skin cell
diploid
somatic cell
diploid
zygote
diploid
sickle-cell disease
A recessively inherited human blood disorder in which a single nucleotide change in the β-globin gene causes hemoglobin to aggregate, changing red blood cell shape and causing multiple symptoms in afflicted individuals
How do buffers moderate pH change?
A buffer is a substance that minimizes changes in the concentration of H+ and OH- in a solution. It does so by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted. Most buffer solutions contain a weak acid and its corresponding base, which combine reversibly with hydrogen ions
aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number. Trisomy 21 (Down syndrome) is an aneuploidy
polyploidy
A chromosomal alteration in which the organism possesses more than two complete chromosome sets. It is the result of an accident of cell division
achondroplasia
A form of dwarfism that occurs in one of every 25,000 people. Heterozygous individuals have the dwarf phenotype. Like the presence of extra fingers or toes, achondroplasia is a trait for which the recessive allele is much more prevalent than the corresponding dominant allele
Huntington's disease
A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms
hemophelia
A human genetic disease caused by a sex-linked recessive allele, resulting in the absence of one or more blood-clotting proteins; characterized by excessive bleeding following injury
cystic fibrosis
A human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated
What happens in Tay-Sachs Disease? Explain the role of lysosome.
A lipid digesting enzyme is missing or inactive, and the brain becomes impaired by an accumulation of lipids in the cells.
What is a lysosome? What do they contain? What is their pH?
A lysosome is a membranous sac of hydrolytic enzymes that animal cell uses to digest macromolecules. Contains lysosomal enzymes.
Prokaryote reproduction does not involve mitosis, but instead occurs by binary fission. This process involves an origin of replication. Describe binary fission.
A method of asexual reproduction by "division in half." In prokaryotes, binary fission does not involve mitosis, but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.
color blindness
A mild disorder almost always inherited as an X-linked allele
What situation did Archibald Garrod suggest caused "inborn errors of metabolism"?
A person's inability to make a particular enzyme
plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment
What is a C4 plant?
A plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle.
What is a C3 plant?
A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate.
b. Sugar sink
A sugar sink is an organ that is a net consumer or depository of sugar. Growing roots, buds, stems, and fruits are sugar sinks. Although expanding leaves are sugar sinks, mature leaves, if well illuminated, are sugar sources.
How do motor proteins called dyneins cause movement of cilia? How is ATP involved?
Adynein molecule persoms complex cycle of movement caused by changes in shape of the protein. ATP provieds energy.
Explain the name ATP and the molecules that make it up.
ATP contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups bonded to it, forming adenosine triphosphate
the light reactions store chemical energy in ___ and _____, which shuttle the energy to the carbohydrate-producing ______ cycle.
ATP; NADPH; Calvin
One function of lysosomes is intracellular digestion of particles engulfed by phagocytosis. Describe this process of digestion. What human cells carry out phagocytosis?
Amoebas and many other protists eat by engulfing smaller organisms or other food particles. The food vacuole formed in this way then fuses with a lysosome, whose enzymes digest the food. Digestion products including simple sugars, amino acids, and other monomers, pass into the cytosol and become nutrients for the cell. Human cells such as macrophages (white blood cells) help defend against bacteria.
Phosphofructokinase is an allosteric enzyme that catalyzes an important step in glycolysis. Explain how this step is a control point in cellular respiration.
As ATP accumulates, inhibition of the enzyme slows down glycolysis. The enzyme becomes active again as cellular work converts ATP to ADP (and AMP) faster than ATP is being regenerated. This mechanism helps synchronize the rates of glycolysis and the citric acid cycle.
Explain why ice floats. Why is 4°C the critical temperature?
As a result of hydrogen bonding, water expands as it solidifies. At 4°C water acts like other liquids, expanding as it warms and contracting as it cools. However, below 4°C water begins to freeze as more and more hydrogen molecules are moving to slowly to break the hydrogen bonds. Hydrogen bonds keep the molecules far enough apart to make ice about 10% less dense than water at 4°C; it is this lower density of ice that allows it to float.
At which end do kinetochore microtubules shorten during anaphase? Explain the Inquiry Figure that supports where this shortening occurs.
As the chromosomes moved poleward, the microtubule segments on the kinetochore side of the mark shortened, while those on the spindle pole side stayed the same length. During anaphase in this cell type, chromosome movement is correlated with kinetochore microtubules shortening at their kinetochore ends and not at their spindle pole ends. This experiment supports the hypothesis that during anaphase, a chromosome is walked along a microtubule as the microtubule depolymerizes at its kinetochore end, releasing tubulin subunits.
independent assortment of chromosomes
At metaphase I, the homologous pairs, each consisting of one maternal and one paternal chromosome, are situated at the metaphase plate. Each pair may orient with either its maternal or paternal homolog closer to a given pole—its orientation is as random as the flip of a coin. Thus, there is a 50% chance that a particular daughter cell of meiosis I will get the maternal chromosome of a certain homologous pair and a 50% chance that it will get the paternal chromosome. Because each pair of homologous chromosomes is positioned independently of the other pairs at metaphase I, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair. This is called independent assortment. Each daughter cell represents one outcome of all possible combinations of maternal and paternal chromosomes.
What is quorum sensing?
Bacterial cells secrete small molecules that can be detected by other bacterial cells. The concentration of such signaling molecules, sensed by the bacteria, allows them to monitor the local density of cells, a phenomenon called quorum sensing. Quorum sensing allows bacterial populations to coordinate their behaviors so they can carry out activities that are only productive when performed by a given number of cells in synchrony.
Why does alcohol abuse increase tolerance to other drugs such as barbiturates?
Barbiturates, alcohol, and many other drugs induce proliferation of smooth ER which are associated with detoxification enzymes, thus increasing rate of detoxification.
Compare and contrast C4 plants with CAM plants. In your explanation, give two key similarities and two key differences.
Both C4 and CAM plants thrive in hot, dry conditions. Both have evolved methods to reduce water loss and to "fix" carbon dioxide in an intermediate compound before it enters the Calvin cycle. C4 plants have Kranz anatomy, with thick-walled bundle-sheath cells. CO2 is added to PEP to make a four-carbon intermediate so that CO2 will not be lost through photorespiration. CAM plants prevent water loss by closing their stomata during the day, but in order to have CO2 available, it is fixed in crassulacean acid when the stomata are open at night. In C4 plants, the initial steps of carbon fixation are separated structurally from the Calvin cycle. In CAM plants, the two steps occur at different times (temporal separation of steps.)
Who has more potential energy: boy at top of slide/boy at the bottom?
Boy at the top of a slide has more potential energy, because of his location.
9. What is bulk flow? Does it depend on solute concentration?
Bulk flow is the movement of liquid in response to a pressure gradient. The bulk flow of material always occurs from higher to lower pressure. Unlike osmosis, bulk flow is independent of solute concentration.
b. Solute Potential
By definition, what is the ψs of pure water? 0 Adding solutes has a negative effect on water potential. When solutes are added, they bind water molecules. As a result, there are fewer free water molecules, reducing the capacity of the water to move and do work. The solute potential of a solution is therefore always negative.
What is the formula of a hexose sugar?
C6H12O6
carbonyl group
C=O
Exercise will result in the production of CO2, which will acidify the blood. Explain the buffering system that minimizes blood pH changes.
Carbonic acid (H2CO3) is formed when CO2 reacts with water in the blood plasma. Carbonic acid dissociates to yield a bicarbonate ion (HCO3-) and a hydrogen ion (H+). The chemical equilibrium between carbonic acid and bicarbonate acts as a pH regulator, the reaction shifting from left or right as other processes in the solution add or remove hydrogen ions.
Explain the energy usage in catabolic reactions of cellular respiration.
Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration. Many carbohydrates can enter glycolysis, most often after conversion to glucose. Amino acids of proteins must be deaminated before being oxidized. The fatty acids of fats undergo beta oxidation to two-carbon fragments and then enter the citric acid cycle as acetyl CoA.
Figure 11.18 shows four different cellular results from a single signaling molecule. Briefly describe each response.
Cell A: Pathway leads to a single response. Cell B: Cross-talk occurs between two pathways. Cell C: Pathway branches lead to two responses. Cell D: Different receptor leads to a different response.
Cell Wall Plasma Membrane Bacterial Chromosome Nucleoid Cytoplasm Flagella
Cell Wall- rigid structure outside the plasma membrane. Plasma Membrane- membrane enclosing the protiens. Bacterial Chromosome- Chromosome is bacteria Nucleoid- Region where the cell's DNA is located (not enclosed by membrane. Cytoplasm- Region between the nucleus and the plama membrane of a eukaryotic cell. Flagella- Locomotion organelles of some bacteria
Why are cells so small? Explain the relationship of surface area to volume.
Cells are so small because if a cell grows beyond a certain limit, not enough material will be able to cross the cell membrane. As a cell increases in size the volume grows proportianately more than its surface area. (Area is proportional to a linear dimension squared, whereas volume is proportional to the linear dimension cubed)
density-dependent inhibition
Cells normally divide until they form a single layer of cells on the inner surface of the culture container, at which point the cells stop dividing. If some cells are removed, those bordering the open space begin dividing again and continue until the vacancy is filled. Follow-up studies revealed that the binding of a cell-surface protein to its counterpart on an adjoining cell sends a growth-inhibiting signal to both cells, preventing them from moving forward in the cell cycle, even in the presence of growth factors.
What is the role of the electron transport chain in forming the H+ gradient across the inner mitochondrial membrane?
Certain members of the electron transport chain accept and release protons (H+) along with electrons. At certain steps along the chain, electron transfers cause H+ to be taken up and released into the surrounding solution. In eukaryotic cells, the electron carriers are spatially arranged in the inner mitochondrial membrane in such a way that H+ is accepted from the mitochondrial matrix and deposited in the intermembrane space. The H+ gradient that results is referred to as a proton-motive force, emphasizing the capacity of the gradient to perform work. The force drives H+ back across the membrane through the H+ channels provided by ATP synthases.
Cilia vs. Flagella
Cilia- occur in large number, differ in beating pattern (oars) Flagella- one or few
Consider coffee to which you have added sugar. Which of these is the solvent? Which is the solute?
Coffee is the solvent and sugar is the solute
Organization of microtubules
Composed of nine sets of triplet microtubules
Uracil
Pyrimidine; found in RNA only
Peroxisomes
Contain enzymes that transfer hydrogen from various substrates to oxygen, producing peroxide.
Cytosine
Pyrimidine; found in both DNA and RNA
Describe cytokinesis in a plant cell.
Cytokinesis in plant cells, which have cell walls, is markedly different. There is no cleavage furrow. Instead, during telophase, vesicles derived from the Golgi apparatus move along microtubules to the middle of the cell, where they coalesce, producing a cell plate. Cell wall materials carried in the vesicles collect in the cell plate as it grows. The cell plate enlarges until itssurrounding membrane fuses with the plasma membrane along the perimeter of the cell. Two daughter cells result, each with its own plasma membrane. Meanwhile, a new cell wall arising from the contents of the cell plate has formed between the daughter cells.
crossing over
Crossing over begins very early in prophase I as homologous chromosomes pair loosely along their lengths. Each gene on one homolog is aligned precisely with the corresponding gene on the other homolog. In a single crossover event, the DNA of two nonsister chromatids—one maternal and one paternal chromatid of a homologous pair—is broken by specific proteins at precisely corresponding points, and the two segments beyond the crossover point are each joined to the other chromatid. Thus, a paternal chromatid is joined to a piece of maternal chromatid beyond the crossover point, and vice versa. In this way, crossing over produces chromosomes with new combinations of maternal and paternal alleles.
Explain the physical events of crossing over.
Crossing over, a genetic rearrangement between nonsister chromatids involving the exchange of corresponding segments of DNA molecules, begins during pairing and synaptonemal complex formation, and is completed while homologs are in synapsis. A chiasma exists at the point where a crossover has occurred.
What are the two chemical components of chromosomes?
DNA and protein
What is the central dogma of molecular genetics as proclaimed by Francis Crick?
DNA-->RNA-->Protein
What is the flow of genetic information?
DNA-->RNA-->protein
nuclease
DNA-cutting enzyme
What did Oswald Avery determine to be the transforming factor? Explain his experimental approach.
DNA. He broke open the heat-killed pathogenic bacteria and extracted the cellular contents. Then he treated each of three samples with an agent that inactivated one type of molecule, and then tested the sample for its ability to transform live nonpathogenic bacteria. Only when DNA was allowed to remain active did transformation occur.
How do ribose and deoxyribose sugars differ?
Deoxyribose sugar lacks an oxygen atom on the second carbon ring
What is the difference between an aldehyde sugar and a ketone sugar?
Depending on the location of the carbonyl group, a sugar is either an aldose (aldehyde sugar) or a ketose (ketone sugar). Glucose, for example, is an aldose; fructose, an isomer of glucose, is a ketose. In aldehyde sugars, the carbonyl group is at the end of the carbon skeleton, while in the ketone sugars, the carbonyl group is within the carbon skeleton.
10. Summarize the three processes that act together to transport resources through the whole plant.
Diffusion, active transport, and bulk flow act in concert to transport resources throughout the whole plant. Although diffusion is an effective transport mechanism over the spatial scales typically found at the cellular level, bulk flow, or the movement of liquid in response to a pressure gradient, is used for long-distance transport throughout the plant. And although sugars in the phloem are transported these long distances via bulk flow due to a pressure difference, the active transport of sugar at the cellular level maintains this pressure difference.
What type of bond is seen in O2?
Double covalent. Two oxygen atoms form a molecule by sharing two pairs of valence electrons
F. Cotransport
During cotransport, plant cells use the energy in the H+ gradient and membrane potential to drive the active transport of many different solutes. For instance, cotransport with H+ is responsible for absorption of neutral solutes, such as the sugar sucrose, by phloem cells and other plant cells. An H+/sucrose cotransporter couples movement of sucrose against its concentration gradient with movement of H+ down its electrochemical gradient.
Describe what happens to the centrosome during interphase and then prophase.
During interphase, a cell that is about to divide grows and copies its chromosomes in preparation for cell division. During prophase, the centrosomes move away from each other, propelled partly by the lengthening microtubules around them.
Explain the difference between kinetochore and nonkinetechore microtubules. What is the function of each?
During prometaphase, some of the spindle microtubules attach to the kinetochores; these are called kinetochore microtubules. Meanwhile, microtubules that do not attach to kinetochores have been elongating, and by metaphase they overlap and interact with other nonkinetochore microtubules from the opposite pole of the spindle.
Describe the difference between the location of DNA in prokaryotic and eukaryotic cells?
Eukaryotic- DNA is in an organelle called the nucleus, which is bounded by double membrane. Prokaryotic- DNA is in concentrated in a non membrane enclosed nucleoid.
Why is the total count about 36 or 38 ATP molecules rather than a specific number?
First, phosphorylation and the redox reactions are not directly coupled to each other, so the ratio of the number of NADH molecules to the number of ATP molecules is not a whole number. Second, the ATP yield varied slightly, depending on the type of shuttle used to transport electrons from the cytosol into the mitochondrion. A third variable that reduces the yield of ATP is the use of the proton-motive force generated by the redox reactions of respiration to drive other kinds of work.
Vacuoles Food vacuoles Contractile Vacuoles Central vacuoles
Food- formed by phagocytosis Contractile- many freshwater protists pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell. Central- In plants hydrolysis is carried out in vacuoles. Develops by the coalescence of smaller vacuoles, themselves derived from Golgi Apparatus and Endoplasmic Reticulum.
What happens to each of the six carbons found in the original glucose molecule?
For each pyruvate molecule formed from the original glucose molecule, the pyruvate is broken down to three CO2 molecules, including the molecule of CO2 released during the conversion of pyruvate to acetyl CoA
Chaperone proteins (chaperonins) assist in the proper folding of proteins. Explain the process.
From Left to Right: 1. An unfolded polypeptide enters the cylinder from one end. 2. The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide. 3. The cap comes off, and the properly folded protein is released See page 85 of text for the labeled figure.
Figure 11.12 explains a cellular response is initiated; how might that response be inhibited?
Further regulation of cell metabolism is provided by other G protein systems that inhibit adenylyl cyclase. In these systems, a different signaling molecule activates a different receptor, which in turn activates an inhibitory G protein.
A G protein is also a GTPase enzyme. Why is this important?
G protein also functions as a GTPase enzyme—in other words, it then hydrolyzes its bound GTP to GDP. Now inactive again, the G protein leaves the enzyme, which returns to its original state. The G protein is now available for reuse. The GTPase function of the G protein allows the pathway to shut down rapidly when the signaling molecule is no longer present.
Why is pyruvate a key juncture n metabolism?
Glycolysis is common to fermentation and cellular respiration. The end product of glycolysis, pyruvate, represents a fork in the catabolic pathways of glucose oxidation. In a facultative anaerobe or a muscle cell, which are capable of both aerobic cellular respiration and fermentation, pyruvate is committed to one of those two pathways, usually depending on whether or not oxygen is present.
Vertical leaf orientation
Grass, Keeps light rays parallel to the leaf surfaces, so no leaf receives too much light and light penetrates more deeply to the lower leaves
How does ATP synthase use the flow of hydrogen to produce ATP?
H+ ions flow down their gradient and enter binding sites within a rotor, changing the shape of each subunit so that the rotor spins within the membrane, before leaving the rotor and passing through a second half channel into the mitochondrial matrix. The spinning of the rotor causes an internal rod to spin, activating catalytic sites in the knob that produce ATP.
Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound?
H2O
What was concluded from the results of Stanley Miller's experiment?
He concluded that organic molecules, a first step in the origin of life, may have been synthesized abiotically on the early Earth.
18. The second mechanism that pulls water up through the plant involves transpiration, adhesion, and cohesion. Refer to Figure 36.11 in your text. Note that water is moving from a region of high water potential to a region of lower water potential. The arrow on the left side of the figure shows this gradient. Write an essay to explain the movement of water from the roots to the leaves. Include each of these terms in your essay, and label them on the figure; root hairs, lower water potential, higher water potential, hydrogen bonding, adhesion, cohesion, xylem tubes, and stoma. Spend time with this figure and its explanation. It is an essential concept! See page 789 of your text for the labeled figure.
Hydrogen bonding, including cohesion between water molecules and adhesion between water molecules and xylem tubes, forms an unbroken chain of water molecules extending from leaves to the soil. The force driving the ascent of xylem sap is a gradient of water potential (ψ). For bulk flow over long distance, the ψ gradient is due mainly to a gradient of the pressure potential (ψp). Transpiration results in lower water potential at the leaf end where the stomata are found compared with higher water potential at the root end.
What happens if all the chromosome kinetochores are not attached to spindle fibers? When this occurs, which checkpoint is not passed?
If all the chromosome kinetochores are not attached to spindle fibers, the sister chromatids remain together, delaying anaphase. When this occurs, the M phase checkpoint is not passed.
Explain how AMP stimulates cellular respiration while citrate and ATP inhibit it.
If the cell is working hard and its ATP concentration begins to drop, respiration speeds up. When there is plenty of ATP to meet demand, respiration slows down, sparing valuable organic molecules for other functions.
a. Plasmolyze
Imagine that a cell is flaccid (limp) as a result of losing water. The cell has a pressure potential of zero. Suppose this cell is bathed in a solution of higher solute concentration than the cell itself. Because the external solution has the lower water potential, water diffuses out of the cell. The cell's protoplast undergoes plasmolysis—that is, it shrinks and pulls away from the cell wall.
Describe cytokinesis in an animal cell.
In animal cells, cytokinesis occurs by a process known as cleavage. The first sign of cleavage is the appearance of a cleavage furrow, a shallow groove in the cell surface near the old metaphase plate. On the cytoplasmic side of the furrow is a contractile ring of actin microfilaments associated with molecules of the protein myosin. The actin microfilaments interact with the myosin molecules, causing the ring to contract. The contraction of the dividing cell's ring of microfilaments is like the pulling of a drawstring. The cleavage furrow deepens until the parent cell is pinched in two, producing two completely separated cells, each with its own nucleus and share of cytosol, organelles, and other subcellular structures.
Who are the two men who built the first molecular model of DNA?
James Watson and Francis Crick
Explain the relationship between wavelength and energy.
Light is a form of energy known as electromagnetic energy, also called electromagnetic radiation. Electromagnetic energy travels in rhythmic waves analogous to those created by dropping a pebble into a pond. Electromagnetic waves, however, are disturbances of electric and magnetic fields rather than disturbances of a material medium such as water. The distance between the crests of electromagnetic wave sis called the wavelength.
21. What are some factors that could possible stimulate the opening and closing of stomata?
Light stimulates guard cells to accumulate K+ and become turgid. This response is triggered by illumination of blue-light receptors in the plasma membrane of guard cells. Activation of these receptors stimulates the activity of proton pumps in the plasma membrane of the guard cells, in turn promoting absorption of K Stomata open in response to the depletion of CO2 within the leaf's air spaces as a result of photosynthesis. As CO2 concentrations decrease during the day, the stomata progressively open if sufficient water is supplied to the leaf. The internal "clock" ensures that stomata continue their daily rhythm of opening and closing. This rhythm occurs even if the plant is kept in the dark.
Explain lumen, transport vesicles, and the difference between smooth and rough ER.
Lumen- the ER membrane separates the internal compartment of the ER. Transport Vesicles- vesicles in transit from one part of the cell to another Smooth vs. Rough: Smooth- lacks ribosomes Rough- has ribosomes on surface.
What does MPF trigger? What are some specific activities that it triggers?
MPF triggers the cell's passage past the G2 checkpoint into M phase.
What is the difference between Magnification and Resolution?
Magnification- ratio of an objects image size to its real size. Resolution- measure of the clarity of the image; it is the minimum distance two points can be seperated and still be distinguished as two points.
For aerobic respiration to continue, the cell must be supplied with oxygen (the ultimate electron acceptor). What is the electron acceptor in fermentation?
NAD+
In cellular respiration, what electron carrier is hydrogen transferred to first?
NAD+
In phase two, the reduction stage, what molecule will donate electrons, and so is the source of the reducing power?
NADPH
Dominant alleles are not necessarily more common than recessive alleles in the gene pool. Explain why this is true.
Natural selection determines how common an allele is in the gene pool. For example, having six fingers (polydactyly) is dominant to five fingers, but the presence of six fingers is not common in the human gene pool.
Figure 16.2
Pg 306
List the three components of a nucleotide
Phosphate, sugar (deoxyribose), nitrogenous base
Large molecules (polymers) are converted to monomers in what type of reaction?
Polymers are disassembled to monomers by hydrolysis, a process that is essentially the reverse of a dehydration reaction
Explain how proteins are targeted for the ER.
Polypeptide synthesis begins on a free ribosome in the cytosol. An SRP binds to a receptor protein in the ER membrane. This receptor is part of a protein complex that has a membrane pore and a signal-cleaving enzyme. The SRP leaves, and the polypeptide synthesis resumes, with simultaneous translocation across the membrane. The signal-cleaving enzyme cuts off the signal polypeptide. The rest of the completed polypeptide leaves the ribosome and folds into its final conformation. See page 343 in text for the labeled figure.
List three types of cellular responses often induced by calcium ions.
Possible examples include muscle cell contraction, secretion of certain substances, cell division, and plant cells greening in response to light.
The signal for apoptosis can come from outside or inside the cell. Give one example when the signal comes from outside the cell and two examples of cellular occurrences that would prompt an apoptosis signal from inside the cell.
Possible examples of cellular occurrences that would prompt apoptosis from inside the cell include the death-signaling molecule, presumably released by a neighboring cell. Examples of apoptosis from inside the cell include a signal from the nucleus, generated when DNA has suffered irreparable damage, and from endoplasmic reticulum, when excessive protein misfolding occurs. Such signals occur during the development of digits in mice, humans, and other mammals, and in certain degenerative diseases of the nervous system, and in some cases the disease is the result from a lack of apoptosis, such as in cancer
Mode of reproduction between prokaryotic and eukaryotic cells?
Prokaryotes divid by fission; eukaryotes by mitosis
The rough ER is studded with ribosomes. As proteins are synthesized, they are threaded into the lumen of the rough ER. Some of these proteins have carbohydrates attached to them in the ER to form glycoproteins. What does the ER then do with these secretory proteins?
Proteins that have carbohydrates covalently bonded to them. The carbohydrates are attached to proteins in the ER by specialized molecules built into the ER membrane.
Thymine
Pyrimidine; found in DNA only
Distinguish between the structure of pyrimidines and purines
Pyrimidines: cytosine (C), thymine (T), and uracil (U); characterized by a six-membered ring Purines: adenine (A) and guanine (G); characterized by a six-membered ring fused to a five-membered ring
Alcohol fermentation starts with glucose and yields ethanol. Explain this process.
Pyruvate is converted to ethanol (ethyl alcohol) in two steps. The first step releases carbon dioxide from the pyruvate, which is converted to the two-carbon compound acetaldehyde. In the second step, acetaldehyde is reduced by NADH to ethanol. This regenerates the supply of NAD needed for the continuation of glycolysis. Many bacteria carry out alcohol fermentation under anaerobic conditions.
Lactic acid fermentation starts with glucose and yields lactate. Explain this process.
Pyruvate is reduced directly by NADH to form lactate as an end product, with no release of CO2. (Lactate is the ionized form of lactic acid.) Pyruvate, the end product of glycolysis, serves as an electron acceptor for oxidizing NADH back to NAD+, which can then be reused in glycolysis.
16. There are two mechanisms that pull water up through the plant, from roots to leaves. Explain root pressure. Note that it is a minor mechanism for the upward movement of water.
Root pressure is the pressure exerted in the roots of plants as the result of osmosis, causing exudation from cut stems and guttation of water from leaves.
Who proposed the fluid mosaic model of membrane structure? when?
SJ Singer and G Nicholson; 1972
What is the role of the second messenger cAMP in figure 11.12?
The cAMP acts as a second messenger and activates another protein, usually protein kinase A, leading to cellular responses.
Figure 8.21
See page 160 of text for the labeled figured. a. What is the substrate molecule to initiate this metabolic pathway? Threonine b. What is the inhibitor molecule? Isoleucine c. What type of inhibitor is it? Noncompetitive inhibitor d. When does it have the most significant regulatory effect? When it binds to an allosteric site e. What is this type of metabolic control called? Feedback inhibition
What happens in step 1 of receptors in the plasma membrane?
See page 212 of text for the labeled figure. Many receptor tyrosine kinases have the structure depicted schematically here. Before the signaling molecule binds, the receptors exist as individual units referred to as monomers. Notice that each has an extracellular ligand-binding site, an α helix spanning the membrane, and an intracellular tail containing multiple tyrosines.
What happens in step 2 of receptors in the plasma membrane?
See page 212 of text for the labeled figure. The binding of a signaling molecule (such as a growth factor) causes two receptor monomers to associate closely with each other, forming a complex known as a dimer (dimerization).
What happens in step 3 of receptors in the plasma membrane?
See page 212 of your text for the labeled figure. Dimerization activates the tyrosine kinase region of each monomer; each tyrosine kinase adds a phosphate from an ATP molecule to a tyrosine on the tail of the other monomer.
What happens in step 4 of receptors in the plasma membrane?
See page 212 of your text for the labeled figure. Now that the receptor is fully activated, it is recognized by specific relay proteins inside the cell. Each such protein binds to a specific phosphorylated tyrosine, undergoing a resulting structural change that activates the bound protein. Each activated protein triggers a transduction pathway, leading to a cellular response.
This diagram uses testosterone, a hydrophobic steroid hormone, as an example of how intracellular receptors work. At each arrow, add an explanation of what is happening in the cell.
See page 214 of your text for the labeled figure. The steroid hormone testosterone passes through the plasma membrane. Testosterone binds to a receptor protein in the cytoplasm, activating it. The hormone-receptor complex enters the nucleus and binds to specific genes. The bound protein acts as a transcription factor, stimulating the transcription of the gene into mRNA. The mRNA is translated into a specific protein.
Figure 11.9
See page 215 of your text for the labeled figure.
Study Figure 12.5 in your text. Summarize what occurs at the DNA level in each stage.
See page 230 of your text for the labeled figure. One of the multiple chromosomes in a eukaryotic cell is represented here, not yet duplicated. Normally it would be a long, thin chromatin fiber containing one DNA molecule and associated proteins; here its condensed form is shown for illustration purposes only. Once duplicated, a chromosome consists of two sister chromatids connected along their entire lengths by sister chromatid cohesion. Each chromatid contains a copy of the DNA molecule. Molecular and mechanical processes separate the sister chromatids into two chromosomes and distribute them to two daughter cells.
Figure 13.9, mitosis vs meiosis
See page 256 in text for the labeled figure.
Try the following problem (Figure 15.7b in your text). A female who carries an allele for color blindness, but who is not color-blind, mates with a male who has normal color vision. What is the probability that they will have a son who is color-blind? A Punnett square to use for this problem is shown in the following figure.
See page 291 of text for the labeled figure. If a carrier mates with a male who has normal color vision, there is a 50% chance that each daughter will be a carrier like her mother and a 50% chance that each son will have the disorder.
Sketch of T2 bacteriophage
See page 306 of text for the labeled figure.
Figure 16.11
See page 312 in text for the labeled figure.
Sketch of a chromosome
See page 319 in your text for the labeled figure
Study Figure 17.2 in your text carefully. On the following unlabeled figure, describe the technique used to identify and isolate mutant fungi.
See page 327 in text for the labeled figure.
Sketch a model of an atom of helium, showing the electrons, protons, neutrons, and atomic nucleus.
See page 33 of text for the labeled figure.
Figure 17.7 in your text will require a bit of study
See page 332 in text for the labeled figure and description of each stage
Use the following figure to explain the process of a specific amino acid being joined to a tRNA
See page 338 of text for the labeled figure.
Fig 17.17
See page 339 of text for the labeled figure.
Fig. 17.26
See page 348 in text for the labeled figure.
Figure 4.2
See page 59 of text for the labeled figure.
Figure 4.4
See page 61 of text for the labeled figure.
Figure 4.7, types of isomers
See page 62 of text for the labeled figure.
Figure 5.3
See page 70 of text for the labeled figure.
Explain figure 5.7 and carbon numbering.
See page 73 of text for the labeled figure. When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below or above the plane of the ring. These two ring forms for glucose are called alpha and beta. In starch, all the glucose monomers are in the alpha configuration.
Figure 5.12, phospholipid
See page 76 in text for the labeled figure.
Figure 5.13, phospholipid bilayer
See page 77 of text for the labeled figure.
Study Figure 5.20
See page 83 in text for the labeled figure. Hydrophobic interaction: amino acids with hydrophobic R groups end up in clusters at the core of the protein, out of contact with water. Van der Waals interaction: transient interactions between R groups Hydrogen Bond: weak bonds between the hydrogen of one R group and the oxygen or nitrogen of another R group Disulfide Bridge: links between the sulfhydryl groups of two cysteine amino acids, sulfur to sulfur Ionic Bond: bonds between an R group that is positively charged and an R group that is negatively charged These interactions tend to fold an amino acid chain into a distinctive three-dimensional form.
Fig 16.13 and 16.15
See pages 314-315 in your text for the labeled figures
On the following diagram, identify the following: 30-nm fiber, metaphase chromosome, double helix, histone proteins, nucleosomes, protein scaffold, and looped domains (300-nm fiber)
See pages 320-321 in text for the labeled figure.
Figure 4.9, chemical groups
See pages 64-65 in text for the labeled chart.
Define the origins of replication
Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides
Explain the events that occur in the carbon fixation stage of the Calvin cycle.
The Calvin cycle incorporates each CO2 molecule, one at a time, by attaching it to a five- carbon sugar named ribulose bisphosphate. The enzyme that catalyzes this first step is RuBP carboxylase, or rubisco. The product of the reaction is a six-carbon intermediate so unstable that it immediately splits in half, forming two molecules of 3-phosphoglycerate
Explain the difference between a pH of 8 and a pH of 12 in terms of H+ concentration.
The H+ concentration of a pH 12 is 104 times greater than that of a pH of 8.
What is a key difference between receptor tyrosine kinases and G protein-coupled receptors?
The ability of a single ligand-binding event to trigger so many pathways is a key difference between receptor tyrosine kinases and G protein-coupled receptors. Abnormal receptor tyrosine kinases that function even in the absence of signaling molecules are associated with many kinds of cancer.
What happens in step 3?
The activated G protein dissociates from the receptor, diffuses along the membrane, and then binds to an enzyme, altering the enzyme's shape and activity. Once activated, the enzyme can trigger the next step leading to a cellular response. See page 211 of text for the labeled figure.
Why does the activity of cyclin-dependent kinases (CDks) rise and fall?
The activity of CDks rises and falls with changes in the concentration of its cyclin partner, MPF.
What products of fossil fuel burning contribute to acid precipitation?
The burning of fossil fuels releases gaseous compounds into the atmosphere. When these compounds react with water, the water becomes more acidic, altering the delicate balance of conditions for life on Earth.
G. Chemiosmosis
The diffusion of water from a region of high concentration to a region of low concentration across a semipermeable membrane
11. Which structure controls the movement of water and minerals into the xylem? How are its cells modified to achieve this function?
The endodermis, the innermost layer of cells in the root cortex, functions as a last checkpoint for the selective passage of minerals from the cortex into the vascular cylinder. Located in the transverse and radial walls of each endodermal cell, the Casparian strip serves as an impervious belt of waxy material called suberin. Because of the Casparian strip, water and minerals cannot cross the endodermis and enter the vascular cylinder via the apoplast. Instead, water and minerals that are passively moving through the apoplast must cross the selectively permeable plasma membrane of an endodermal cell before they can enter the vascular cylinder.
Explain the concept of blending, and then describe how Mendel's "particulate" (gene) hypothesis was different.
The explanation of heredity most widely in favor during the 1800s was the "blending" hypothesis, the idea that genetic material contributed by the two parents mixes in a manner analogous to the way blue and yellow paints blend to make green. This hypothesis predicts that over many generations, a freely mating population will give rise to a uniform population of individuals. However, our everyday observations and the results of breeding experiments with animals and plants, contradict that prediction. The blending hypothesis also fails to explain other phenomena of inheritance, such as traits reappearing after skipping a generation. An alternative to the blending model is a "particulate" hypothesis of inheritance: the gene idea. According to this model, parents pass on discrete heritable units—genes—that retain their separate identities in offspring.
Explain why water is such a fine solvent.
The fact that water is such a versatile solvent can be traced back to the polarity of the water molecule. Water can dissolve ionic compounds, many compounds made up of nonionic polar molecules, as well as molecules such as proteins if they have polar and ionic regions on their surface.
Explain the process of the flow of genetic information.
The mRNA molecule interacts with the cell's protein-synthesizing machinery to direct production of a polypeptide, which folds into all or part of a protein. The sites of protein synthesis are tiny structures called ribosomes. In a eukaryotic cell, ribosomes are in the cytoplasm, but DNA resides in the nucleus. Messenger RNA conveys genetic instructions for building proteins from nucleus to the cytoplasm
Explain the potential influence of the environment on phenotypic expression.
The outcome of a genotype lies within its norm of reaction, a phenotype range that depends on the environment in which the genotype of expressed. For some characters, such as the ABO blood group system, the norm of reaction has no breadth whatsoever. Other characteristics, such as a person's blood count of red and white cells, varies quite a bit, depending on such factors as the altitude, the customary level of physical activity, and the presence of infectious agents. Genetics refers to such characters as multifactorial, meaning that many factors, both genetic and environmental, collectively influence phenotype.
How does tyrosine kinase function in the membrane receptor?
The part of the receptor protein extending into the cytoplasm functions as a tyrosine kinase, an enzyme that catalyzes the transfer of a phosphate group from ATP to the amino acid tyrosine on a substrate protein. Thus, receptor tyrosine kinases are membrane receptors that attach phosphates to tyrosines.
What is the difference between a first messenger and a second messenger?
The pathway's "first messenger" is considered to be the extracellular signaling molecule—the ligand—that binds to the membrane receptor. Many signaling pathways also involve small, non- protein, water-soluble molecules or ions called second messengers.
5. The evolution of mycorrhizae was a critical step in the successful colonization of land by plants. What are they, and what is their role in resource acquisition?
The term mycorrhizae refers to the mutualistic associations between roots and fungi. Mycorrhizae are a critical step in the successful colonization of land by vascular plants, especially given the poorly developed soils available at the time.
Found within the nucleus are the chromosomes which are made of chromatin. What are the two components of chromatin? When do the thin chromatin fibers condense to become distinct chromosomes?
The two components of chromatin are DNA and Protiens. When thin chromatin fibers coil up (condense), be coming thick enough to be distinguished as seperate structures.
How did Hershey and Chase "label" viral DNA and viral protein so that they could be distinguished? Explain why they chose each radioactive tag in light of the chemical composition of DNA and protein.
They used radioactive isotopes of sulfur to tag protein in one batch of T2 and a radioactive isotope of phosphorus to tag DNA in a second batch. Because proteins, but not DNA, contain sulfur, radioactive sulfur atoms were incorporated only into the protein of the phage.
Explain why the dihybrid cross detailed in Figure 14.12 in your text has four yellow Labrador retrievers instead of the three that would have been predicted by Mendel's work.
This dihybrid cross results in four yellow Labrador retrievers rather than three because the dominant allele, symbolized by E, results in the deposition of either black or brown pigment. If the Lab is homozygous recessive for the second locus (ee), then the coat is yellow, regardless of the genotype at the black/brown locus. The E/e gene is epistatic to the B/b gene.
Explain the role of PEP carboxylase in C4 plants, including key differences between it and rubisco.
This enzyme adds CO2 to phosphoenolpyruvate (PEP), forming the four-carbon product oxaloacetate. PEP carboxylase has a much higher affinity for CO2 than does rubisco and no affinity for O2. Therefore, PEP carboxylase can fix carbon efficiently when rubisco cannot—that is, when it is hot and dry and stomata are partially closed, causing CO2 concentration in the leaf to fall and O2 concentration to rise.
15. Describe the process of transpiration in your own words and how it affects the transportation of minerals and water.
Transpiration is the loss of water vapor from leaves through the stomata.
C. What are transport proteins?
Transport proteins span the membrane; they allow hydrophilic substances to avoid contact with the lipid bilayer of a cell membrane as they move.
What was the first codon-amino acid pair to be identified?
UUU (poly-U)-phenylalanine
Horizontal leaf orientation
Understory plants in tropical rain forest capture light more effectively in low-light conditions
Why did researchers originally think that protein was the genetic material?
Until the 1940s, the case for proteins seemed stronger, especially since biochemists had identified them as a class of macromolecules with great heterogeneity and specificity of function, essential requirements for the hereditary material. Moreover, little was known about nucleic acids, whose physical and chemical properties seemed far too uniform to account for the multitude of specific inherited traits exhibited by every organism
H. Water Potential
Water potential is the physical property that predicts the direction in which water will flow. It includes the effects of solute concentration and physical pressure. The equation for water potential is ψ = ψs + ψp, where ψ is water potential, ψs is solute potential, and ψp is the pressure potential.
How does water's specific heat compare to alcohol's specific heat?
Water's specific heat is unusually high at 1 cal/g•°C, whereas alcohol's specific heat is is 0.6 cal/g•°C.
a. Flaccid
When a flaccid cell is placed in pure water, water moves into the cell via osmosis because the solutes inside the cell create a lower water potential. The contents of the cell begin to swell and press the plasma membrane against the cell wall. The partially elastic wall, exerting turgor pressure, confines the pressurized protoplast. When this pressure is enough to offset the tendency for water to enter because of the solutes in the cell, then the solute potential equals the pressure potential, causing the water potential to equal zero.
Explain what happens as the ligand dissociates.
When the ligand dissociates from this receptor, the gate closes and ions no longer enter the cell. See page 213 of text for the labeled figure.
3. What triggers self pruning?
When there is a high leaf area index, the lower leaves respire more than they photosynthesize; this triggers the nonproductive leaves to undergo programmed cell death and they are eventually shed in the process called self-pruning.
Scientists expected to find one aminoacyl-tRNA synthetase per codon, but far fewer have been discovered. How does wobble explain this?
Wobble is flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon. This flexibility explains why there are only about 45 tRNAs.
For each of the following human aneuploidies, give the sex of the individual as well as any physical manifestation of the syndrome.
XXY: Male, Klinefelter syndrome-male sex organs, but abnormally small/ sterile testes; some breast enlargement and other female characteristics XXX: Female, Trisomy X-no unusual physical features other than being slightly taller than average; at risk for learning disabilities; fertile XO: Female, Turner syndrome-phenotypically female, but sterile due to lack of maturation in sex organs; secondary sex characteristics developed with estrogen replacement; normal intelligence XYY: Male, Normal sexual development; taller than average stature
malignant tumor
a cancerous tumor containing cells that have significant genetic and cellular changes and are capable of invading and surviving in new sites; can impair the functions of one or more genes
Define chromosome. How many are in human cells?
a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells, and each chromosome consists of one very long DNA molecule and associated proteins; 46
chromosome
a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins
Define point mutations.
a change in a single nucleotide pair of a gene
Define transformation
a change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer
Define mutations.
a change in the nucleotide sequence of an organism's DNA or in the DNA or RNA of a virus
catalyst
a chemical agent that selectively increase the rate of a reaction without being consumed by the reaction
functional group
a chemical group that affects molecular function by being directly involved in chemical reactions
What is a cell cycle checkpoint?
a control point in the cell cycle where stop and go-ahead signals can regulate the cycle
What is glycosidic linkage?
a covalent bond formed between two monosaccharides by a dehydration reaction
peptide bond
a covalent bond in which two amino acids are joined by a dehydration reaction
deletion
a deficiency in a chromosome resulting in the loss of a fragment through breakage
Barr body
a dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactived X chromosome
gene
a discrete unit of hereditary info consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)
gamete
a haploid reproductive cell, such as an egg or sperm; unite during sexual reproduction to produce a diploid zygote
character
a heritable feature that varies among individuals, such as flower color
How can we tell if a fatty acid chain is unsaturated?
a kink in the chain, indicating a double bond
alternation of generations
a life cycle in which there is both a multicellular diploid form; characteristic of plants and some algae
solution
a liquid that is a completely homogenous mixture of two or more substances
polymer
a long chain-like molecule, consisting of many similar or identical building blocks linked by covalent bonds
enzyme
a macromolecule serving as a catalyst, a chemical agent that increases the rate of reaction without being consumed by the reaction; most enzymes are proteins
describe the davson-danelli model of membrane structure.
a phospholipid bilayer between two layers of proteins; sandwich-like
polypeptide
a polymer of many amino acids liked by a peptide bond See page 80 of text for the labeled figure.
What are growth factors?
a protein released by certain cells that stimulates other cells to divide
What is a release factor? By what mechanism is termination accomplished?
a protein shaped like an aminoacyl tRNA, which binds directly to the stop codon in the A site. Hydrolyzation is the mechanism by which termination is accomplished, releasing the polypeptide through the exit tunnel of the ribosome's large subunit
paracrine signaling
a secreting cell acts on nearby target cells by discharging molecules of a local regulator fluid into the extracellular; growth factors
glycolysis
a series of reactions that ultimately splits glucose into pyruvate
signal transduction pathway
a series of steps linking mechanical, chemical, or electrical stimulus to a specific cellular response
Transfer RNA has two attachment sites. What binds at each site? Sketch tRNA.
a specific anticodon binds at one end of tRNA, and a corresponding amino acid at the other end. See page 337 of text for the labeled figure.
locus
a specific place along the length of a chromosome where a given gene is located
What is a kinetochore?
a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle
compound
a substance consisting of two or more different elements combined in a fixed ratio (NaCl and H2O)
element
a substance that cannot be broken down to other substances by chemical reactions (gold, copper, carbon)
acid
a substance that increases the hydrogen ion concentration of a solution
base
a substance that reduces the hydrogen ion concentration of a solution
epistasis
a type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene
What was the role of Rosalind Franklin in the discovery of the double helix?
a very accomplished X-ray crystallographer, conducted critical experiments resulting in the photograph that allowed Watson and Crick to deduce the double-helical structure of DNA
Summary about the citric acid cycle.
a. How many NADHs are formed? 1 b. How many total carbons are lost as pyruvate is oxidized? 3 c. The carbons have been lost in the molecule carbon dioxide. d. How many FADH2 have been formed? 1 e. How many ATPs are formed? 1 f. How many times does the citric acid cycle occur for each molecule of glucose? 2
What are four mechanisms enzymes use to lower activation energy?
a. In reactions involving two or more reactants, the active site provides a template on which the substrates can come together in the proper orientation for a reaction to occur between them. b. As the active site of an enzyme clutches the bound substrate, the enzyme may stretch the substrate molecules toward their transition-state form, stressing and bending critical chemical bonds that must be broken during the reaction. c. The active site may also provide a microenvironment that is more conducive to a particular type of reaction than the solution itself would be without the enzyme. d. Direct participation of the active site in the chemical reaction is another mechanism of catalysis.
What are the steps necessary to convert pyruvate to acetyl CoA?
a. Pyruvate's carboxyl group, which is already fully oxidized and thus has little chemical energy, is removed and given off as a molecule of CO2 . b. The remaining two-carbon fragment is oxidized, forming acetate (the ionized form of acetic acid). The extracted electrons are transferred to NAD+ , storing energy in the form of NADH. c. Finally, coenzyme A, a sulfur compound derived from a B vitamin, is attached via its sulfur atom to the acetate, for acetyl CoA, which has a high potential energy. This molecule will now feed its acetyl group into the citric acid cycle for further oxidation.
Explain how Mendel's simple cross of purple and white flowers did the following: a. refuted blending b. determined dominant and recessive characteristics c. demonstrated the merit of experiments that covered multiple generations
a. The reappearance of white-flowered plants in the F2 generation was evidence that the heritable factor causing white flowers had not been diluted or destroyed by coexisting with the purple-flower factor in the F1 hybrids. b. Mendel reasoned that the heritable factor for white flowers did not disappear in the F1 plants, but was somehow hidden, or masked, when the purple-flower factor was present. In Mendel's terminology, purple flower color is a dominant trait, and white flower color is a recessive trait. c. Had Mendel stopped his experiments with the F1 generation, the basic patterns of inheritance would have escaped him. Mendel's quantitative analysis of the F2 plants from thousands of genetic crosses like these allowed him to deduce two fundamental principles of heredity: the law of segregation and the law of independent assortment.
What factors affect the rate of enzyme action? Explain each.
a. initial concentration: the more substrate molecules that are available, the more frequently they access the active sites of the enzyme molecules b. pH: with some exceptions, the optimal pH values for most enzymes fall in the range of pH 6-8 c. temperature: up to a point, the rate of an enzymatic reaction increases with increasing temperature, b/c substrates collide with active sites more frequently when molecules move rapidly. Above that temperature, the speed of the enzymatic reaction drops sharply
RNA processing occurs only in eukaryotic cells. The primary transcript is altered at both ends, and sections in the middle are removed. What happens at the 5' end? What happens at the 3' end?
a. the 5' end is synthesized first; it receives a 5' cap, a modified form of a guanine (G) nucleotide added onto the 5' end after transcription of the first 20-40 nucleotides b. the 3' end of the pre-mRNA molecule is also modified before the mRNA exits the nucleus. An enzyme adds 50-250 more adenine (A) nucleotides, forming a poly-A tail
Mendel's First concept
alternative versions of genes account for variations in inherited characters
hydroxyl
always polar
-NH2
amino
What are the monomers of proteins called?
amino acids
What are the two most widely used methods for testing a fetus for genetic disorders?
amniocentesis and chorionic villus sampling
What is a ribozyme?
an RNA molecule that functions as an enzyme, such as an intron that catalyzes its own removal during RNA splicing
duplication
an aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated
translocation
an aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome
inversion
an aberration in chromosome structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated
potential energy
an object not presently moving; it is the energy that matter possesses b/c of its location or structure
What is a hydrocarbon? Give example.
an organic molecule consisting of only carbon and hydrogen; fats are examples of such
coenzyme
an organic molecule serving as a cofactor
What are alleles?
any of the alternative versions of a gene that may produce distinguishable phenotypic effects (allele for freckles)
matter
anything that takes up space and has mass (rocks, metals, oils, gases)
reaction center complex
associated with a special pair of chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain
Why is water considered polar?
because of its unequal sharing of electrons and its V-like shape
induced fit
caused by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate; this change allows additional weak bonds to form, causing the active site to enfold the substrate and hold it in place
What happens to a cell during apoptosis?
cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components. The cell shrinks and becomes lobed, and the cell's parts are packaged up in vesicles that are engulfed and digested by specialized scavenger cells, leaving no trace.
Describe structure of a eukaryotic ribosome.
consists of a large subunit and a small subunit, each made up of proteins and one or more rRNAs
Chromosomes in bacteria
consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded
cellular respiration
consumes oxygen as a reactant along with the organic fuel
Kinases drive the cell cycle, but they must be activated by attachment of a ______.
cyclin
Where does glycolysis occur? Does it require oxygen?
cystol; no
Intracellular receptors are found either in the _________ or _______ of target cells. In order to be able to pass through the plasma membrane, the chemical messengers are either ___________ or very small, like nitric oxide.
cytoplasm; nucleus; hydrophobic
Monomers are connected in what type of reaction? What occurs in this reaction?
dehydration reaction; two monomer molecules are covalently bonded to each other with the loss of a water molecule. in this reaction, each monomer contributes part of the water molecule that is released during the reaction. This reaction is repeated as monomers are added to the chain one by one, making a polymer
What are the ways chromosome structure can be altered?
deletion, duplication, inversion, translocation
rRNA
description: ribosomal RNA function: together with proteins, makes up ribosomes, the most abundant type of RNA
tRNA
description: transfer RNA, about 75 nucleotides long; folds into a clover-leaf shape function: transfers amino acids from the cytoplasmic pool of amino acids to a growing polypeptide in a ribosome
carbonyl
determines the two groups of sugars
structural isomer
differ in the covalent arrangement of their atoms (pentane and 2-methylbutane)
isotope
different atomic formations of the same element, having more neutrons than other atoms of the same element and therefore having greater mass
isotope
different atomic forms of the same element (example includes carbon-12)
However, meiosis always begins with cells that are _______ , and as a result of meiosis, daughter cells are formed that are always _______. These cells can be gametes (in animals) or spores (in plants).
diploid; haploid
In sexually reproducing organisms, why are there exactly two chromosomes in each homologous pair?
each somatic cell in a diploid organism has two sets of chromosomes, one set inherited from each parent
trait
each variant for a character, such as purple or white color for flowers
what is the combination of these 2 forces called
electrochemical gradient
essential element
elements that an organism needs to live a healthy life and reproduce; comprise about 20-25% of the 92 natural elements
Is photosynthesis endergonic or exergonic? What is the energy source that drives it?
endergonic; uses 686 kcal to make mole of glucose; energy comes from environment by using light and turning it into chemical energy
receptor-mediated endocytosis
endocytosis in which the vesicles contain proteins with receptor cites specific to the molecules being taken in
What is the first step in glycolysis called?
energy investment phase
What is the second step in glycolysis called?
energy payoff phase (provides both ATP and NADH)
List four important functions of fats.
energy storage, long-term food reserve in mammals, adipose tissue cushions vital organs, body insulation
potential energy
energy that matter possessed because of its location or structure
How is protein structure involved in enzyme specificity?
enzymes are proteins, and proteins are macromolecules with unique 3D configuration. The specificity results from its shape, which is a consequence of its amino acid sequence. It is also attributed to a compatible fit between the shape of its active site and the shape of the substrate
What are the four types of proteins?
enzymes, storage, motor and contractile, transport and receptor
F1 generation
first filial generation
storage proteins
function: storage of amino acids example: casein, ovalbumin
transport proteins
function: transport example: proteins embedded in the plasma membranes; aquaporins; hemoglobin
hydrophilic substance
has an affinity for water (cotton)
amphipathic
has both a hydrophobic region and hydrophilic region
channel proteins
have a hydrophilic channel that some molecules/ions use as a tunnel through membrane
centromere
in a duplicated chromosome, the region on each sister chromatid where they are most closely attached to each other by proteins that bind to specific DNA sequences; this close attachment causes a constriction in the condensed chromosome
energy coupling
in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction
Much like transcription, we can divide translation into three stages. List them.
initiation, elongation, termination
Identify two mechanisms by which frameshifts may occur.
insertion and deletion
How is the chromosome number of daughter cells different in meiosis?
it yields nonidentical daughter cells that have only one set of chromosomes (23), half as many chromosomes as the parent cell
ligase
joins the sugar-phosphate backbones of all the Okazaki fragments into a continuous DNA strand
Name saturated fats.
lard, butter, or most animal fats
What is the source of energy that excites the electron in photosystem II?
light
What are the two processes that make up photosynthesis?
light reactions and Calvin cycle
primary
linked series of amino acids with a unique sequence
What strategy did Beadle and Tatum adopt to test this hypothesis?
m bombarded the bread mold Neurospora with X-rays, and then looked among the survivors for mutants that differ in their nutritional needs from the wild-type bread mold.
glycolipids
membrane carbs covalently bonded to lipids
glycoproteins
membrane carbs covalently bonded to proteins
Where are the electron carriers found in eukaryotic cells for electron transport? In prokaryotic cells?
membrane of mitochondria; plasma membrane
Describe the fluid mosaic model of membrane structure.
membrane proteins are dispersed, individually inserted in phospholipid bilayer, with their hydrophilic regions protruding.
intercellular joining
membrane proteins of adjacent cells may hook together in various kinds of junctions, such as gap or tight junctions
how do phospholipids with unsaturated hydrocarbon chains affect membrane fluidity?
membrane remains fluid to lower temperatures; because of (cis) kinks, phospholipids can not pack together as closely
how does decreasing temperature affect membrane fluidity?
membrane remains fluid until phospholipids settle in a closely packaged arrangement
What is membrane fluidity?
membranes dont stay completely still; most lipids and proteins shift laterally, some proteins drift.
What is always the first amino acid in the new polypeptide?
methionine
In animal cells, the assembly of spindle microtubules starts at the centrosome. What is another name for the centrosome?
microtubule-organizing center
enantionmers
mirror images of each other that differ in shape due to the presence of an asymmetric carbon, one that is attached to four different atoms, or a group of atoms (ibuprofen and albuterol); R and S directions
What group of genes do you inherit from your mother only?
mitochondrial DNA
By what process are the damaged cells in a wound replaced?
mitosis
By what process does a zygote develop into a multicellular organism?
mitosis
In which process are identical daughter cells produced?
mitosis
M
mitosis distributes the daughter chromosomes to daughter nuclei, and cytokinesis divides the cytoplasm, producing two daughter cells
number of DNA replications
mitosis: 1 meiosis: 1; occurs during interphase before meiosis I begins
number of divisions
mitosis: 1 meiosis: 2
number of daughter cells
mitosis: 2 meiosis: 4
chromosome number of daughter cells
mitosis: 2n meiosis: n
role in the animal body
mitosis: enables multicellular adult to arise from zygote; produce cells for growth, repair, and in some species, asexual reproduction meiosis: produces gametes; reduces number of chromosomes by half and introduces genetic variability among the gametes
What characteristics do all lipids share?
mix poorly with water
methane
molecule: yes compound: yes molecular formula: CH4
What is the chromosome number?
n
If energy is released, deltaG must be what?
negative
anion
negatively charged ion
What occurs in the glycolysis step of cellular respiration?
occurs in almost all living cells, serving as the starting point for fermentation/cellular respiration
hydrogen bonding
occurs when the slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of a nearby molecule, holding them together. Hydrogen bonds are fragile and at any given moment a substantial percentage of all the water molecules are hydrogen-bonded to their neighbors.
coenzyme
organic molecule serving as a cofactor; most vitamins function as such
quaternary
overall protein structure that results from the aggregation of these polypeptide subunits
tertiary
overall shape of the polypeptide resulting from interactions between the side chains (R groups) of the various amino acids
NAD+
oxidized; lower energy
What strongly electronegative atom, pulling electrons down the ETC, is the final electron acceptor?
oxygen
Fermentation allows for the production of ATP without what two factors?
oxygen or electron transport chain
What four elements make up 96% of all living matter?
oxygen, carbon, hydrogen, and nitrogen
Figure 14.11
page 273
transcription factors
special proteins called transcription factors control which genes are turned on (which genes are transcribed into mRNA) in a particular cell at a particular time
fuction of transport proteins
provides hydrophilic channel that it selective; some shuttle substances from one side to the other by changing shape; some hydrolize ATP
describe active transport
pumping a molecule across a membrane against its gradient by expending energy carrier proteins are involved
Guanine
purine; found in both DNA and RNA
NADH
reduced; higher energy
What is the SRY gene?
refers to the Sex determining Region of Y, a gene found on the Y chromosome that is required for the development of testes
What is represented by R? How many are there?
refers to the side chains of amino acids; 20
When cell signaling causes a nuclear response, what normally happens?
regulation of the gene activity in the cell nucleus
When the terminal phosphate bond is broken, a molecule of inorganic phosphate Pi is formed, and energy is....
released (making it exergonic)
topoisomerase
relieves strain caused by unwinding; joins DNA fragments together
Name the two types of gametes.
sperm and eggs
What is the source of O2 in the atmosphere?
splitting water
During meiosis I, homologous chromosomes separate. What separates during meiosis II?
sister chromatids separate during this process
What are the two categories of polysaccharides?
storage (starch, glycogen); structural (cellulose, chitin)
Carbon chains form skeletons. List here the types of skeletons that can be formed.
straight, branched, closed rings
Strength and weakness of amniocentesis
strength: In addition to fetal cells, amniotic fluid is also collected. Amniotic fluid can be used to detect additional enzymatic or developmental problems not detectable from the karyotype weakness: Cells must be cultured for several weeks before karyotyping, and the test cannot be performed until the fourteenth to sixteenth week
Strength and weakness of CVS
strength: These cells proliferate rapidly enough to allow karyotyping to be carried out immediately, and CVS can be performed as early as the eighth to tenth week weakness: No amniotic fluid is collected with this technique
cellulose
structural polysaccharide that comprises plant cell walls
chitin
structural polysaccharide that gives cockroaches their exterior
neutron
subatomic particle that is electrically neutral
electron
subatomic particle with one unit of a negative charge
proton
subatomic particle with one unit of positive charge
hydrophobic substance
substances that are nonionic and nonpolar and cannot form hydrogen bonds and therefore seem to repel water
noncompetitive inhibitor
substances that reduce the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product
competitive inhibitor
substances that reduce the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics
What is the second form of phosphorylation called?
substrate level
What two molecules make up the "uprights"?
sugar and phosphate
Figure 9.9 on page 169
summary of glycolysis
When cell signaling causes a cytoplasmic response, what normally happens?
synthesis of a particular protein
transcription summary
template: DNA product synthesized: RNA location in eukaryotic cell: nucleus
translation summary
template: mRNA product synthesized: polypeptide location in eukaryotic cell: cytoplasm
mechanical work
the beating of cilia, the contraction of muscle cells, and the movement of chromosomes during cellular respiration
allosteric regulation
the binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site
transduction
the binding of the signaling molecule changes the receptor protein in some way, initiating the process of transduction. The transduction stage converts the signal to a form that can bring about a specific cellular response
transformation
the conversion of a normal animal cell to a cancerous cell
What is a thymine dimer, how does it occur, and how is it repaired?
the covalent linking of thymine bases that are adjacent on a DNA strand, causing the DNA to buckle and interfere with DNA replication. In order to repair, a nuclease enzyme cuts the damaged DNA strand, and the damaged section is removed. DNA polymerase fills in the missing nucleotides, and DNA ligase seals the free end of the new DNA to the old DNA, making the strand complete
mitosis
the division of the genetic material in the nucleus; followed immediately by cytokinesis
How do scaffolding proteins enhance a cellular response?
the efficiency of signal transduction is apparently increased by the presence of scaffolding proteins, large relay proteins to which several other relay proteins are simultaneously attached
What are the two components that are involved in oxidative phosphorylation?
the electron transport chain and ATP synthesis
chemiosmosis
the energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP
What happens when NAD+ is reduced, and what enzyme is involved?
the enzymatic transfer of 2 e- and 1 proton from an organic molecule in food to NAD+ reduces the NAD+ to NADH; the second proton is released; dehydrogenase
molarity
the number of moles of solute per liter of a solution-is the unit of concentration most often used by biologists for aqueous solutions
What occurs in synapsis?
the pairing and physical connection of duplicated homologous chromosomes during prophase I of meiosis
codominance
the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways (ex. in the human MN blood group, determined by the codominant alleles for two specific molecules located on the surface of red blood cells, the M and N molecules)
What is free energy? What is its symbol?
the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell. Free energy is symbolized by the letter G
proton-motive force
the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions across a biological membrane during chemiosmosis
addition rule
the probability that any two or more mutually exclusive events will occur is calculated by adding their individual probabilties
What is gene expression?
the process by which info encoded in DNA directs the synthesis of proteins or, in some cases, RNAs that are not translated into proteins and instead function as RNAs
genetic recombination
the process during which linked genes become unlinked
transport work
the pumping of substances across membranes against the direction of spontaneous movement (sodium-potassium pump)
chemical work
the pushing of endergonic reactions that would not occur spontaneously (synthesis of polymers from monomers)
heat of vaporization
the quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state
absorption spectrum
the range of a pigment's ability to absorb various wavelengths of light; also a graph of such a range
substrate
the reactant on which an enzyme works
What is crossing over?
the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis
concentration gradient
the region along which the density of a chemical substance decreases
exons (exons are expressed)
the segments of nucleic acid that are eventually expressed by being translated into amino acid sequences
In humans, how have sex-linked genes been historically modified?
the sex-linked traits are actually X-linked genes
ligand.
the signal molecule (ligand) bind to the receptor
incomplete dominance
the situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele (ex. the crossing of red snapdragons with white snapdragons to produce F1 hybrids with pink flowers)
complete dominance
the situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable
active site
the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs
metastasis
the spread of cancer cells to locations distant from their original site
solute
the substance dissolved by the solvent
Mendel's Fourth concept (law of segregation)
the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes**
Example of character and trait.
the varying color of the flowers on pea plants is a character, and the specific variations, white and purple,are traits
What is membrane potential? which side of the membrane is positive?
the voltage across a membrane; the outside
What unusual result suggested that the eye-color trait is located on the X chromosome?
the white-eye trait showed up only in males
peripheral proteins
these proteins are not imbedded in the lipid bilayer at all; they are loosely bound to the surface of a membrane, often exposed to parts of integral proteins.
integral proteins
these proteins penetrate the hydrophobic core of the lipid bilayer.
What happens to chromosome number in meiosis?
they are reduced by half
What do geneticists call the offspring that show these new combinations after crossing over and experimenting genetic recombination?
they call the offspring that show these new combinations recombinant types, or recombinants for short
What are the strands said to be antiparallel?
they run in opposite 5'-->3' directions from each other
If a fat is composed of three fatty acids and one glycerol molecule, how many water molecules will be removed to form it? Again, what is this process called?
three water molecules for every triacylglycerol formed; dehydration synthesis
What is the purpose of meiosis??
to reduce the number of sets of chromosomes from two to one in gametes
Each activated protein in the figure above triggers a signal ____________ pathway leading to a ________ response.
transduction; cellular
The step that converts pyruvate to acetyl CoA at the top of the diagram occurs twice per glucose. What does oxidation of pyruvate account for?
two additional reduced NADH molecules and two molecules of CO2
parental combination
two genes linked on the same chromosome; will be transmitted as a unit and will not sort independently
glucose
two monomers of this form maltose
molecule
two or more atoms held together by a covalent bond
sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes
What cause Down syndrome?
usually the result of an extra chromosome 21, so that each cell has a total of 47 chromosomes. Because the cells are trisomic for chromosome 21, Down syndrome is often called trisomy 21