Cell Bio: Final
The first task you are assigned in your summer laboratory job is to prepare a concentrated NaOH stock solution. The molecular weight of NaOH is 40. How many grams of solid NaOH will you need to weigh out to obtain a 500 ml solution that has a concentration of 10 M? o 800 g o 200 g o 400 g o 160 g
(500 mL) x (1L/1000mL) x (10 mol / 1L) x (40g / 1 mol) 200 g
What happens in the photosystem I and II, respectively?
-1: It is responsible for providing high-energy electrons with which to reduce NADP+ to produce NADPH to be used in the Calvin cycle. -2: uses light energy to oxidize two molecules of water into one molecule of molecular oxygen.
Which ions generate electrochemical gradients in plant cells and animal cells?
-Animal:Na+, K+, pump -Plant: Na+, K+, Ca2+, Cl-
Which of the following are second messengers? -Ca2+ -IP3 -cAMP -ATP -DAG -GTP -K+
-CA2+ -IP3 -cAMP
Describe the difference between anabolic and catabolic pathways.
-Catabolic: breaking down large molecules into simple ones, release energy -Anabolic: construct biochemical processes, forming complex molecules from simple ones, require energy
What are clathrin, COPI and COPII?
-Clathrin: protein that assembles into a polyhedray cage on the cytosolic side of a membrane so as to form a clathrin coated pit, which buds off by endocytosis to form an intracellular clathrin-coated vesicle. Stimulate budding and promote onward transporation. -COPI-protein complex coats vesicle transporting proteins from cis end of golgi complex back to rough ER. -COPII-vesicle coat protein, transports proteins from rough ER to golgi.
Name different proteins of the extracellular matrix.
-Collagen -Elastin -Fibronectin -Integrin -CAGS, -Proteoglycans -Cellulose
Name at least two types of cytoskeletal drugs and how they act.
-Cytochalasin: cell permeable and protein inhibitor of actin polymerization. Disrupts actin filament and activates p53 dependent pathways. -Colchicine: medication for gout, toxic natural product, and secondary metabolite.
Describe the major differences between DNA and RNA.
-DNA deoxyribose sugar double-stranded thymine more stable -RNA ribose sugar single-stranded uracil less stable
Describe briefly the three main chromatographic principles by which proteins can be purified.
-Gel filtration- separation based on size. Two phases, stationary and mobile. Smaller molecules flow at reduced amounts -Ion- based on charge of the ions and the pH in the solution. Opposite charges are retarded -Affinity- is based on the antibody binding to the protein
What is the source of electrons for the mitochondrial and chloroplastic electron transport chain?
-M:NADPH and succinate -C:light (slpitting of water)
What is the terminal electron acceptor in the mitochondrial and chloroplastic electron transport chains?
-M:O2 -C:NADP+
How does cholesterol affect membrane fluidity?
-Maintains membrane fluidity and stability -Protects specific proteins -More fluid without cholesterol and short -Other factors that affect fluidity:temp, pH, kinks in chains, number of carbons(less more fluid) -Prevents rapid movement
What are elements of the spindle apparatus?
-Microtubles -Asters -Kinetochores -Centrioles -Centrosome -Chromosomes -Chromatids
Where do the electrons for the electron transport chain come from in mitochondria and chloroplasts
-Mitochondria= it is the conversion of oxygen to water, NAPD to NAD+, and succinate to fumarate that generates a protein (NADH and FADH) -Chloroplasts=light drives the conversion of water to oxygen and NADP+ to NADPH with transfer to H+ ions across chloroplast membranes
Name at least two types of proteins associated with the cytoskeleton and describe briefly their function.
-Myosin 1:functions as monomer and in vesicle transport. -Myosin 2: responsible for producing muscle contraction in muscle cells or -Kinesin- moves toward (+) end of actin/microfilaments usually carrying ER Myosin -Dynein- usually move toward (-) end of filaments carrying golgi
Describe the building blocks of DNA.
-Nucleotides binded together by phoshodiester bonds -5 carbon sugar -Phosphate group -Nitrogenous base
Which structure connects two plant cells? What are the elements of this structure?
-Plasmodesmata -Plasma membrane lining
Describe briefly the characteristics of the following items with regard to proteins: o Primary structure o Secondary structure o Tertiary structure o Quaternary structure
-Primary:amino acid sequence of polypeptide chain, held together by covalent/peptide bonds -Secondary:highly local sub-cultures, alpha helix and beta strand -Tertiary:3D structure of a single protein molecule -Quaternary: large assembly of several protein molecules or polypeptide chains, called subunits
Describe briefly the different phases of the cell cycle.
-S phase:period where DNA is synthesized -M phase: chromosomes are condensed, nucleus and cytoplasm divide -G1: between the end of mitosis and start of DNA synthesis -G2:between end of DNA synthesis and start of mitosis
What do you separate by SDS Polyacrylamide-Gel electrophoresis?
-Separates by protein size, and molecular weight -It is a commonly used technique and also separated s-s linkages.
What is alternative splicing?
-Splicing of the same gene in different ways. -Removal of introns from RNA transcript
Name at least three different types of cell junctions found in epithelial cells.
-Tight junctions- act as a barrier does not allow ions to pass through -Gap junctions- allow the passage of ions and H2O soluble molecules to pass through. -Desmisomes- cannot intermediate filaments of neighbor cells -Hemidesomes- anchor intermediate to basil lamina -Adherons (adhere junction)- actin filaments attach from neighbor cells
Describe the three protein import mechanisms?
-Vesicle Transport -Gated -Transmembrane
What are the functions of clathrin and COP proteins?
-clathrin=helps makes the vesicles -COP= direct the vesicles to target proteins They make a clathrin coat and once the vesicle is created the coat is shredded. Basically is helps to enforce vesicles Protein targeting is the mechanism by which a cell transports proteins to the appropriate positions in the cell or outside of it and then are removed.
Describe briefly the molecular forces (on the atomic level) that govern the interaction between molecules?
-covalent bonds- shared electrons -electrostatic (ionic)- charged molecule interactions -van der waals- weak interactions -dipole-dipole-partially neg and pos -ion-ion -hydrogen bonds- between H with N, O, of F
What are the four major forms of intercellular signaling?
-endocrine -paracrine -synaptic (neuronal) -contact-dependent
What are proteins kinases and which class of enzymes reverses the effects?
-enzyme that transfers the terminal phosphate group of ATP to one or more specific amino acids(serine, threonine, or tyrosine) of a target protein -reversed by diesterase
When do cells use active transport across a membrane?
-from low to high-movement of a substance against concentration gradient. -concerned with accumulating high concentrations of molecules needed
For which compartment would you expect gated, transmembrane, and vesicle transport?
-gated= nucleus -transmembrane= chloroplasts, mitochondria, peroxisomes -vesicle transport= golgi/ER
Describe the molecular structure of a phospholipids (schematic). How are they arranged in a lipid bilayer? How can proteins be associated with this structure?
-has a hydrophilic head and hydrophobic tail, polar head group, glycerol, fatty acid, phosphate, ester group -yes
In the electron-transport chain in chloroplasts, ________-energy electrons are taken from __________. o high; H2O. o low; H2O. o high; NADPH. o low; NADPH. Does this occur in photosystem I or II?
-high; H2O. -photosystem II
Which protein integrates the extracellular matrix with the cytosol?
-integrins -fibronectins
What are the three classes of cell surface receptors?
-ion-channel coupled -enzyme coupled -G-protein coupled
Describe briefly or illustrate schematically the difference between conventional light microscopy and fluorescence microscopy.
-light=light source underneath, inverted -fluorescence=light comes through the objective straight through specimen, filter system, mirror system Picture:
What are characteristics of endocrine signaling?
-long distance -slow acting/delivery -long term -secreted into the blood -hormones released throughout blood -produced in one tissue, transported throughout blood and target receptor -a signal molecule binds to a receptor that initiates release of hormones throughout blood
Which process is involved in the nutritional utilization of fatty acids in cells and where does that process occur in animal and plant cells?
-mitochondrial matrix in eukaryotic cells -cytosol in prokaryotic cells
In cells glucose (C6H12O6) is metabolized to pyruvate (C3H4O3). Would you describe this as an oxidative process or a reduction? And should this be considered as a catabolic pathway or an anabolic?
-oxidative -catabolic
What is produced in the light reaction of photosynthesis?
-oxygen:released out of plant -glucose(food):spread thru stem to roots
Name at least three different functions of membrane proteins?
-transport of substances across membranes --enzymatic activity -signal transduction -attachment to the cytoskeleton and extracellular matrix
What is characteristic for the plus end and the minus end of actin and microtubule filaments?
-two ends polymerize at different rates -fast growing is plus end, slow growing is minus end
Name three modifications that have to be made to an RNA molecule in eukaryotic cells before the RNA molecule becomes a mature mRNA.
1) RNA cappins 2) polyadenylation 3)splicing
True or false: 1. Centrifugation can be used to separate cellular components effectively. 2. Centrifugation can only be used to separate large objects, but small particles like microsomes and ribosomes cannot be separated. 3. Centrifugation is an outdated technology and has been replaced by other methods.
1. Centrifugation can be used to separate cellular components effectively. TRUE 2. Centrifugation can only be used to separate large objects, but small particles like microsomes and ribosomes cannot be separated. FALSE 3. Centrifugation is an outdated technology and has been replaced by other methods. FALSE
Give examples for gated, transmembrane, and vesicle transport (with respect to the compartments involved).
1. Gated transport (e.g. proteins move between cytosol to nucleus, which are topographically equivalent, through nuclear pore complexes) 2. Transmembrane transport (e.g. cytosol to ER lumen. Goes from one place to another that is topologically distinct) 3. Vesicular transport (e.g. ER lumen to golgi lumen).
True or false: 1. Nextgen sequencing is based on the principle of sequencing by synthesis. 2. Microarray analysis is used to detect alternative splice variants. 3. PCR can only be used to identify transcripts, but cannot be used for quantification.
1. Nextgen sequencing is based on the principle of sequencing by synthesis. TRUE 2. Microarray analysis is used to detect alternative splice variants. FALSE 3. PCR can only be used to identify transcripts, but cannot be used for quantification. FALSE
True or false: 1. Restriction enzymes cut DNA randomly. 2. Restriction enzymes recognize specific sequences on DNA and always cuts so that only blunt ends are produced. 3. Restriction enzymes can be used to compare different genomes based on the produced pattern of DNA fragments.
1. Restriction enzymes cut DNA randomly. FALSE 2. Restriction enzymes recognize specific sequences on DNA and always cuts so that only blunt ends are produced. FALSE 3. Restriction enzymes can be used to compare different genomes based on the produced pattern of DNA fragments. TRUE
Describe briefly the three maturation steps of mRNA before it can leave the nucleus for translation
1. mRNA splicing of introns which joins together exons 2. Addition to create 5' end cap 3. Adding poly-a-tail at the end of mRNA transcript
Modern eucaryotes depend on mitochondria to generate most of the cell's ATP. How many molecules of ATP can a single molecule of glucose generate? o 30 o 2 o 20 o 36
2
In which direction is DNA read during transcription?
3'-5'
In which direction is DNA synthesized?
5'-3'
Which of the following DNA strands can form a DNA duplex by pairing with itself at each position? o 5′-AAGCCGAA-3′ o 5′-AAGCCGTT-3′ o 5′-AAGCGCAA-3′ o 5′-AAGCGCTT-3′
5′-AAGCGCTT-3′
You are interested in a single-stranded DNA molecule that contains the following sequence: o 5′- .....GATTGCAT.... -3′ Which molecule can be used as a probe that will hybridize to your sequence of interest? o 5′-GATTGCAT-3′ o 5′-TACGTTAG-3′ o 5′-CTAACGTA-3′ o 5′-ATGCAATC-3′
5′-ATGCAATC-3′
Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing? o5′CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′ o5′UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3′ o5′AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3′ o5′GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′
5′CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′
Starting with onedouble-stranded DNA molecule, how many cycles of PCR would you have to perform to produce about 100 double‐stranded copies (assuming 100% efficiency per cycle)? o 2 o 7 o 25 o 100
7
What is an action potential? Describe briefly.
Action potentials are caused when different ions cross the neuron membrane. A stimulus first causes sodium channels to open. Because there are many more sodium ions on the outside, and the inside of the neuron is negative relative to the outside, sodium ions rush into the neuron.
Which of the following statements about the cytoskeleton is true? o All eukaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm. o The cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell. o The three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another.
All eukaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm.
Which proteins regulate the cell cycle?
CDKs and cyclins
Which of the following statements about collagen is false? o Collagen synthase organizes the mature collagen molecules into ordered collagen fibrils. o Collagen is synthesized as procollagen and secreted to the outside of the cell in a secretory vesicle. o The terminal procollagen domains are cleaved by a protease in the extracellular space. o Cells can break down a collagen matrix using matrix proteases
Collagen synthase organizes the mature collagen molecules into ordered collagen fibrils.
What is the importance of tight junctions with regard to nutrient uptake?
Doesn't block nutrient uptake but regulates it, to control what it takes in and keeps out
Where are cell membranes assembled?
ER
Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels? o lysosome -> endosome -> plasma membrane o ER -> lysosome -> plasma membrane o Golgi -> lysosome -> plasma membrane o ER -> Golgi -> plasma membrane
ER -> Golgi -> plasma membrane
Which of the following choices reflects the appropriate order through which a protein destined for the plasma membrane travels? o lysosome → endosome → plasma membrane o ER → lysosome → plasma membrane o Golgi → lysosome → plasma membrane o ER → Golgi → plasma membrane
ER → Golgi → plasma membrane
Which of the following statements about RNA splicing is false? o Conventional introns are not found in bacterial genes. o For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene. o Small RNA molecules in the nucleus perform the splicing reactions necessary for the removal of introns. o Splicing occurs after the 5' cap has been added to the end of the primary transcript.
For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene.
When does RNA production occur during the cell cycle?
G1
What is the difference between genomic and cDNA clones?
Genomic -Still has introns- noncoding doesn't cover extract coding sequence -Random DNA sequence -Cut DNA fragments -Whole genome cDNA -Comes directly from mRNA -Cap removed still have poly A tail -contains entire gene without introns can over express -Uninterrupted DNA sequence in membrane protein
Match the general type of biochemical reaction catalyzed in the left column with the class of enzyme listed in the column on the right. o ___ removes a phosphate group from a molecule o ___ hydrolyzes ATP o ___ hydrolyzes bonds between nucleotides o ___ adds phosphate groups to molecules o ___ catalyzes reactions in which one molecule is oxidized and another is reduced o ___ hydrolyzes peptide bonds o ___ joins two ends of DNA together o ___ catalyzes the synthesis of polymers such as RNA and DNA o ___ rearranges bonds within a single molecule A. ATPase B. polymerase C. ligase D. kinase E. isomerase F. nuclease G. oxidoreductase H. protease I. phosphatase
I. phosphatase = removes a phosphate group from a molecule A. ATPase = hydrolyzes ATP F. nuclease= hydrolyzes bonds between nucleotides D. kinase= adds phosphate groups to molecules G. oxidoreductase= catalyzes reactions in which one molecule is oxidized and another is reduced H. protease= hydrolyzes peptide bonds C. ligase= joins two ends of DNA together B. polymerase= catalyzes the synthesis of polymers such as RNA and DNA E. isomerase= rearranges bonds within a single molecule
Which of the following statements about membrane-enclosed organelles is true? o In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. o The nucleus is the only organelle that is surrounded by a double membrane. o Other than the nucleus, most organelles are small and thus, in a typical cell, only about 10% of a cell's volume is occupied by membrane enclosed organelles; the other 90% of the cell volume is the cytosol. o The nucleus is the only organelle that contains DNA.
In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane.
Why are dideoxyribonucleoside triphosphates used during DNA sequencing? o They cannot be incorporated into DNA by DNA polymerase. o They are incorporated into DNA particularly well by DNA polymerases from thermophilic bacteria. o Incorporation of a dideoxyribonucleoside triphosphate leads to the termination of replication for that strand. o Dideoxyribonucleoside triphosphates are more stable than deoxyribonucleoside triphosphates.
Incorporation of a didoxyribonucleoside triphosphate leads to the termination of replication for that strand.
Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?
Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.
DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA? o It contains uracil. o It contains thymine. o It is single stranded. o It has 5′-to-3′ directionality.
It contains thymine
Does the same signaling molecule always induce the same response in its various target cells?
No, a single signal molecule can have different effects on a different types of target cells
If you weigh yourself on a scale one morning, then eat four pounds of food during the day, will you weigh four pounds more the next morning?
No, the weight will not increase by four pounds in the next morning. This is because, the food what we eat is digested and the nutrients are metabolized to derive energy. Some of the energy is utilized for daily activities, and excess energy is stored. The unabsorbed food is excreted.
Which of the following methods is not used by cells to regulate the amount of a protein in the cell? o Genes can be transcribed into mRNA with different efficiencies. o Many ribosomes can bind to a single mRNA molecule. o Proteins can be tagged with ubiquitin, marking them for degradation. o Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.
Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.
Which of the following statements about molecular switches is false? o Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. o Protein kinases transfer the terminal phosphate from ATP onto a protein. o Serine/threonine kinases are the most common types of protein kinase. o A GTP-binding protein exchanges its bound GDP for GTP to become activated.
Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.
Which of the following statements about the endoplasmic reticulum (ER) is false? o The ER is the major site for new membrane synthesis in the cell. o Proteins to be delivered to the ER lumen are synthesized on smooth ER. o The ER membrane is contiguous with the outer nuclear membrane.
Proteins to be delivered to the ER lumen are synthesized on smooth ER.
The information stored in the DNA sequences is used directly as a template to make ___________. o lipids. o RNA. o polypeptides. o carbohydrates.
RNA
Which of the following statements about restriction nucleases is false? o A reproducible set of DNA fragments will be produced every time a restriction nuclease digests a known piece of DNA. o Restriction nucleases recognize specific sequences on single-stranded DNA. o Some bacteria use restriction nucleases as protection from foreign DNA. o Some restriction nucleases cut in a staggered fashion, leaving short, single-stranded regions of DNA at the ends of the cut molecule.
Restriction nucleases recognize specific sequences on single-stranded DNA.
Microtubules are important for transporting cargo in nerve cell axons, as diagrammed below. Notice that the two types of cargo are traveling in opposite directions. Which of the following statements is likely to be false? o The gray cargo is attached to dynein. o The black cargo and the gray cargo require ATP hydrolysis for their motion. o The black cargo moving toward the axon terminal contains a domain that specifically interacts with the tail domain of a particular kind of motor. o The black cargo and the gray cargo are moving along microtubules of opposite polarity.
The black cargo and the gray cargo are moving along microtubules of opposite polarity.
Which of the following statements about skeletal muscle contraction is false? o When a muscle cell receives a signal from the nervous system, voltage gated channels open in the T-tubule membrane. o The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction. o A change in the conformation of troponin leads to changes in tropomyosin such that it no longer blocks the binding of myosin heads to the actin filament. o During muscle contraction, the Z discs move closer together as the myosin heads walk toward the plus ends of the actin filaments.
The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction.
The four phases of the cell cycle, in order, are G1, ___, ______, and ______. A cell contains the most DNA after ____ phase of the cell cycle. A cell is smallest in size after ______ phase of the cell cycle. Growth occurs in ____, ______, and ______ phase of the cell cycle. A cell does not enter mitosis until is has completed _____ synthesis.
The four phases of the cell cycle, in order, are G1, (S), (G2), and (M). A cell contains the most DNA after (S) phase of the cell cycle. A cell is smallest in size after (M) phase of the cell cycle. Growth occurs in (G1), (S), and (G2) phase of the cell cycle. A cell does not enter mitosis until is has completed (DNA) synthesis.
Which of the following statements about plant cell walls is true? o The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall. o The molecular components of the cell wall are the same in all plant tissues. o Because plant cell walls are rigid, they are not deposited until the cell has stopped growing. o The cellulose found in cell walls is produced as a precursor molecule in the cell and delivered to the extracellular space by exocytosis.
The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall.
Which of the following statements regarding dynamic instability is false? o Each microtubule filament grows and shrinks independently of its neighbors. o The GTP cap helps protect a growing microtubule from depolymerization. o GTP hydrolysis by the tubulin dimer promotes microtubule shrinking. o The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.
The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end
Your friend has isolated plasma membranes and reassembled the membranes into small vesicles. Using fluorescently labeled lectin, he sees that some of his vesicles are labeled while others are not. Keep in mind that lectin binds to carbohydrates and cannot permeate membranes. Which population of vesicles has a surface similar to that of a cell? Explain.
The population of vesicles labeled with fluorescent lectin is most likely to have a surface similar to that of the cell. Lectins bind carbohydrates and the cell adds polysaccharides to the noncytosolic portion of membrane proteins. Because the noncytosolic side of a vesicle will eventually become the extracellular surface of the plasma membrane, it is equivalent to the surface of the cell. Lectin is present on "right-side out" vesicles
Which of the following best describes the mechanism by which chromatin remodeling complexes "loosen" the DNA wrapped around the core histones? o They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer. o They chemically modify the DNA, changing the affinity between the histone octamer and the DNA. o They remove histone H1 from the linker DNA adjacent to the core histone octamer. o They chemically modify core histones to alter the affinity between the histone octamer and the DNA.
They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer.
Which of the following statements is not an accurate statement about thymine dimers? o Thymine dimers can cause the DNA replication machinery to stall. o Thymine dimers are covalent links between thymidines on opposite DNA strands. o Prolonged exposure to sunlight causes thymine dimers to form. o Repair proteins recognize thymine dimers as a distortion in the DNA backbone.
Thymine dimers are covalent links between thymidines on opposite DNA strands.
Right or wrong: During translation a new amino acid is added to the N-terminus of the growing peptide chain.
Wrong
Right or wrong: Only one strand of the DNA double helix serves as a template for RNA synthesis.
Wrong
Right or wrong: the equilibrium constant in a chemical reaction changes in the presence of an enzyme.
Wrong
In the membrane of a human red blood cell the ration of the mass of the protein (average molecular weight 50,000) to phospholipid (average molecular weight 800) tO cholesterol (molecular weight 386) is about 2:1:1. How many lipid molecules (phospholipid + cholesterol) are there for every protein molecule? • 0.02 • 21 • 42 • 96 • 192
[(50,000/800) + (50,000/386)]/2= 96
What are oncogenes?
a gene that in certain circumstances can transform a cell into a tumor cell.
The figure below shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood-vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? o a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO o a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP o a muscle cell that has cyclic GMP phosphodiesterase constitutively active o a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO
a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP
By definition, prokaryotic cells do not possess __________. o a nucleus. o replication machinery. o ribosomes. o membrane bilayers.
a nucleus
Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of ________________. o a water molecule. o an amino group. o a carbon atom. o a carboxylic acid group.
a water molecule
True or false: a. After protein separation by SDS-PAGE each band on the gel represents only one protein. b. Isoelectric focusing of proteins separates by size. c. SDS only binds to polar proteins.
a. After protein separation by SDS-PAGE each band on the gel represents only one protein. FALSE b. Isoelectric focusing of proteins separates by size. FALSE c. SDS only binds to polar proteins. FALSE
Which of the following statements is true and which ones are false: a. Gap junctions share plasmamembrane between two adjoining cells. b. Plasmodesmata connect only epidermal cells in a plant body. c. A desmotubulus connects two cells through a plasmodesmata. d. Tight junctions allow the exchange of molecules between two adjoining cells. e. A desmosome provides a highly dynamic structure that allows adjoining cell to move in a coordinated fashion. f. Adherens junctions are coupled to the microfilament system.
a. Gap junctions share plasmamembrane between two adjoining cells. FALSE b. Plasmodesmata connect only epidermal cells in a plant body. FALSE c. A desmotubulus connects two cells through a plasmodesmata. TRUE d. Tight junctions allow the exchange of molecules between two adjoining cells. FALSE e. A desmosome provides a highly dynamic structure that allows adjoining cell to move in a coordinated fashion. FALSE f. Adherens junctions are coupled to the microfilament system. TRUE
Name the different types of cytoskeleton.
actin filaments, microtubules, intermediate filaments
Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called_____________. o active transport. o free diffusion. o facilitated diffusion. o passive transport.
active transport
Which of the following statements about amino acids is true? o Twenty-two amino acids are commonly found in proteins. o Most of the amino acids used in protein biosynthesis have charged side chains. o Amino acids are often linked together to form branched polymers. o All amino acids contain an NH2 and a COOH group
all amino acids contain an NH2 and a COOH group
After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode? o soluble secreted proteins o ER membrane proteins o plasma membrane proteins o all of the above
all of the above
The number of distinct protein species found in humans and other organisms can vastly exceed the number of genes. This is largely due to ______________. o protein degradation. o alternative splicing. o homologous genes. o mutation.
alternative splicing
Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found? o an aquaporin o a sodium channel o a calcium channel o a proton channel
an aquaporin
Select the best option to fill in the blanks of the following statement: Fermentation in yeast is a/an _____________________ process that converts_____________ into carbon dioxide and _____________________. o anaerobic, pyruvate, ethanol o anaerobic, lactate, ethanol o eukaryotic, glyceraldehyde 3-phosphate, ethanol o prokaryotic, lactate, propanol
anaerobic, pyruvate, ethanol
A plasmid______________. o can confer antibiotic resistance to a bacterium. o is a single-stranded circular DNA molecule that can undergo horizontal transfer among bacteria. o is a tool designed in the lab and never found in naturally occurring bacteria. o always becomes part of the bacterial chromosome during transformation.
can confer antibiotic resistance to a bacterium.
Apoptosis differs from necrosis in that necrosis ________________. o requires the reception of an extracellular signal. o causes DNA to fragment. o causes cells to swell and burst, whereas apoptotic cells shrink and condense. o involves a caspase cascade.
causes cells to swell and burst, whereas apoptotic cells shrink and condense.
The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of _____________. o Brownian motion. o heat. o light waves. o chemical bonds.
chemical bonds
The link between bond-forming reactions and membrane transport processes in the mitochondria is called __________________. o chemiosmotic coupling o proton pumping o electron transfer o ATP synthesis
chemiosmotic coupling
What is the fundamental role of cholesterol in biological membranes?
cholesterol is required to build and maintain cell membranes. it regulates membrane fluidity, helps in cell signaling, and structure support
Which of the following molecules is not found in plants? o cellulose o lignin o collagen o pectin
collagen
You want to compare the protein composition within different fractions of cells. How would you proceed?
column chromatography? protein purification
Which of the following steps or processes in aerobic respiration include the production of carbon dioxide? o breakdown of glycogen o glycolysis o conversion of pyruvate to acetyl CoA o oxidative phosphorylation
conversion of pyruvate to acetyl CoA
What makes the plasma membrane asymmetrical?
different composition inside and out of the cell, different components on each side (such as proteins and amphipathic lipid molecules)
The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by ________________. o activating a G protein. o activating a receptor tyrosine kinase. o diffusing into cells and stimulating the cyclase directly. o activating an intracellular protein kinase.
diffusing into cells and stimulating the cyclase directly.
DNA replication is considered semiconservative because____________________________. o after many rounds of DNA replication, the original DNA double helix is still intact. o each daughter DNA molecule consists of two new strands copied from the parent DNA molecule. o each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand. o new DNA strands must be copied from a DNA template.
each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand.
NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional ________ and one additional _____________. This combination can also be referred to as a hydride ion. o protons, electron o electrons, phosphate o hydrogens, electron o electrons, proton
electrons, proton
Signal sequences that direct proteins to the correct compartment are _________. o added to proteins through post-translational modification. o added to a protein by a protein translocator. o encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.
encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.
The second law of thermodynamics states that the disorder in any system is always increasing. In simple terms, you can think about dropping NaCl crystals into a glass of water. The solvation and diffusion of ions is favored because there is an increase in _____________. o pH o entropy o ionic structure o stored energy
entropy
What do detergents do?
example is SDS. disrupt cell membranes by disrupting the lipid barrier surrounding cell by disrupting lipid:lipid, lipid:protein, and protein:protein interactions.
Why do cells switch to fermentation and how do they benefit from this process?
form waste product and no more energy is produced, help keep harvested energy. (generate energy and reduce power) switch depending on environmental conditions
The manner in which a gene sequence is related to its respective protein sequence is referred to as the _________ code. o protein o genetic o translational o expression
genetic
Which elements are involved in the formation of a nucleosome?
histones
When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________. o neurotransmitter. o hormone. o dissolved gas. o scaffold.
hormone
Both DNA and RNA are synthesized by covalently linking a nucleoside triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together? o ionic interactions o hydrogen bonds o covalent bonds o van der Waals interactions
hydrogen bonds
Which of the following is not a chemical modification commonly found on core histone N-terminal tails? o methylation o hydroxylation o phosphorylation o acetylation
hydroxylation
Where are proteins in the chloroplast synthesized? o in the cytosol o in the chloroplast o on the endoplasmic reticulum o in both the cytosol and the chloroplast
in both the cytosol and the chloroplast
When does DNA replication occur during the cell cycle?
in the S(synthesis) phase of interphase-cell copies DNA
Where does most new membrane synthesis take place in a eukaryotic cell? o in the Golgi apparatus o in the endoplasmic reticulum o in the plasma membrane o in the mitochondria o on ribosomes
in the endoplasmic reticulum
What are introns? Describe briefly their fate during mRNA processing.
introns are non-coding they are spliced out during RNA then splicing then exons are joined together mRNA processing involves splicing of introns.
In anaerobic conditions, skeletal muscle produces _____________. o lactate and CO2. o ethanol and CO2. o lactate only. o ethanol only.
lactate only.
Double covalent bonds are both shorter and stronger than single covalent bonds, but they also limit the geometry of the molecule because they ____________________. o create a new arrangement of electron shells. o change the reactivity of the bonded atoms. o limit the rotation of the bonded atoms. o prevent additional bonds from being formed with the bonded atoms.
limit the rotation of the bonded atoms.
signaling pathway
look up in notes
In principle, a eucaryotic cell can regulate gene expression at any step in the pathway from DNA to the active protein. Which of the controls in A-E correctly correspond to the site of regulation in the Figure x. Decide by matching the NUMBER at the site of control in the figure (number 1-6) to the corresponding NUMBER (1-6) listed in the choices AE.
mRNA degradation control protein activity control RNA processing control RNA transport and localization control transcriptional control translational control
Which amino acid will be on the tRNA that is the first to bind to the A site of the ribosome? o methionine o arginine o cysteine o valine
methionine
The cytoskeleton provides support, structure, motility, and organization, and it forms tracks to direct organelle and vesicle transport. Which of the cytoskeletal elements listed below is the thickest? o actin filaments o microtubules o intermediate filaments o none of the above (all the same thickness)
microtubules
Which of the following organelles has both an outer and an inner membrane? o endoplasmic reticulum o mitochondrion o lysosome o peroxisome
mitochondrion
Glycolysis is an anaerobic process used to catabolize glucose. What does it mean for this process to be anaerobic? o no oxygen is required o no oxidation occurs o it takes place in the lysosome o glucose is broken down by the addition of electrons
no oxygen is required
The __________ __________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum. o plasma membrane o Golgi network o mitochondrial membrane o nuclear envelope
nuclear envelope
Transcription is similar to DNA replication in that ___________________. o an RNA transcript is synthesized discontinuously and the pieces are then joined together. o it uses the same enzyme as that used to synthesize RNA primers during DNA replication. o the newly synthesized RNA remains paired to the template DNA. o nucleotide polymerization occurs only in the 5'-to-3' direction.
nucleotide polymerization occurs only in the 5'-to-3' direction.
Which subatomic particles contribute to the atomic mass for any given element? o protons o protons and neutrons o neutrons o protons and electrons
protons and neutrons
The final metabolite produced by glycolysis is ___________. o acetyl CoA. o pyruvate. o 3-phosphoglycerate. o glyceraldehyde 3-phosphate.
pyruvate
The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. Choose the correct series of biochemical reactions from the options presented here. o replication, transcription, translation o replication, translation, transcription o translation, transcription, replication o translation, replication, transcription
replication, transcription, translation
The classic experiments conducted by Meselson and Stahl demonstrated that DNA replication is accomplished by employing a ________________ mechanism. o continuous o semiconservative o dispersive o conservative
semiconservative
Describe two major outcomes of the citric acid cycle.
serves 2 main purposes: to increase the cells ATP producing potential(by having products) provide the cell with precursors that can be used to build a variety of molecules depending on the cells needs.
A covalent bond between two atoms is formed as a result of the ______________. o sharing of electrons. o loss of electrons from both atoms. o loss of a proton from one atom. o transfer of electrons from one atom to the other.
sharing of electrons
What part of an amino acid contributes to the structure and function of a protein?
side chains
Which of the following chemical groups is not used to construct a DNA molecule? o five-carbon sugar o phosphate o nitrogen-containing base o six-carbon sugar
six-carbon sugar
Where are the lipids for the various membrane systems produced?
smooth ER (ndoplasmic reticulum; lipid particles or mitochondria but more commonly ER)
What is the fate of protein targeting sequences?
spliced and degraded
The process of DNA replication requires that each of the parental DNA strands be used as a ___________________ to produce a duplicate of the opposing strand. o catalyst o competitor o template o copy
template
The process of DNA replication requires that each of the parental DNA strands be used as a ___________________ to produce a duplicate of the opposing strand. o catalyst o competitor o template o copy
template
Progression through the cell cycle requires a cyclin to bind to a Cdk because _________. o the cyclins are the molecules with the enzymatic activity in the complex. o the binding of a cyclin to Cdk is required for Cdk enzymatic activity. o cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle. o without cyclin binding, a cell-cycle checkpoint will be activated.
the binding of a cyclin to Cdk is required for Cdk enzymatic activity.
Which of the following phenomena will be observed if a cell's membrane is pierced? o the membrane reseals o the membrane collapses o a tear is formed o the membrane expands
the membrane reseals
Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference? o unsaturated hydrocarbons o longer hydrocarbon tails o higher levels of sterols o larger head groups
unsaturated hydrocarbons
Cell biologists employ targeted fluorescent dyes or modified fluorescent proteins in both standard fluorescence microscopy and confocal microscopy to observe specific details in the cell. Even though fluorescence permits better visualization, the resolving power is essentially the same as that of a standard light microscope because the resolving power of a microscope is limited by the __________ of light. o absorption o intensity o filtering o wavelength
wavelength
Which factor determines most the resolution of a light microscope: a. Objective b. Ocular c. Wavelength of light d. Stain of specimen
wavelength of light
Describe briefly the difference between euchromatine and heterochromatine.
Describe briefly the difference between euchromatine and heterochromatine.
An aqueous solution contains two amino acids. The concentration of amino acid X is 250 uM and the concentration of amino acid Y is 500 uM. The molecular weight of amino acid X is 120 Da, and the molecular weight of Y is 150 Da. How much of the respective amino acid (in g) is in 500ml of the solution?
Amino acid X: m = 2.5 x 10-4 mol/L * 0.5 L * 120 g/mol m = 0.015 g Amino acid Y: m = 5.0 x 10-4 mol/L * 0.5 L * 150 g/mol m = 0.0375 g
Which of the following statements about apoptosis is true? o Cells that constitutively express Bcl2 will be more prone to undergo apoptosis. o The prodomain of procaspases contains the catalytic activity necessary for procaspase activation. o Bax and Bak promote apoptosis by binding to procaspases in the apoptosome. o Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.
Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria.
What is the primary reason for why this cooling step is necessary? o Cooling the reaction ensures the integrity of the covalent bonds holding the nucleotides together in the DNA strand. o Cooling the reaction gives the DNA polymerase an opportunity to rest from the previous cycle so that it will be ready for the next round of synthesis. o Transcription takes place during the cooling step. o Cooling the reaction brings the temperature down to a level that is compatible with the short primers forming stable hydrogen bonds with the DNA to be amplified.
Cooling the reaction brings the temperature down to a level that is compatible with the short primers forming stable hydrogen bonds with the DNA to be amplified.
Which of the following statements about the cytoskeleton is false? o The cytoskeleton is made up of three types of protein filaments. o The cytoskeleton controls the location of organelles in eukaryotic cells. o Covalent bonds between protein monomers hold together cytoskeletal filaments. o The cytoskeleton of a cell can change in response to the environment.
Covalent bonds between protein monomers hold together cytoskeletal filaments.
What is characteristic for the intrinsic pathway leading to apoptosis?
Cytochrome C accumulates in mitochondira that leads to activation of other protein and causes apoptosis
Which of the following is true for fluorescence microscopy: a. Excitation wavelength is always smaller than the emission wavelength b. Excitation wavelength is always larger than the emission wavelength c. Excitation wavelength and emission wavelength are similar
Excitation wavelength is always smaller than the emission wavelength
True or false: Western blotting is used to detect specific RNA and DNA sequences after separation by gel electrophoresis
False
True or false: You can watch living cells in an electron microscope with high resolution.
False
True or false: During cell division the plant cell dissociates from its cell wall and is divided by a contractile ring made of microfilaments.
False
True or false: Targeting sequences are added posttranslational and remain on the protein throughout its lifecycle.
False
True or false: The material for cellulose microfibrils is delivered to the extracellular matrix of plants by vesicle transport.
False
Which cytoskeletal element is thought to organize the microfibril orientation in plant cells?
Microtubles
Stage 2 of photosynthesis, sometimes referred to as the dark reactions, involves the reduction of CO2 to produce organic compounds such as sucrose. What cofactor is the electron donor for carbon fixation? o H2O o NADH o FADH2 o NADPH
NADPH
Is the number of chromosomes a good indicator for the determination of how closely species are related to each other?
No
In oxidative phosphorylation, ATP production is coupled to the events in the electron-transport chain. What is accomplished in the final electron transfer event in the electron-transport chain? o OH- is oxidized to O2. o Pyruvate is oxidized to CO2. o O2 is reduced to H2O. o NAD+ is reduced to NADH.
O2 is reduced to H2O.
Oxidative phosphorylation is a process that occurs in the __________________ of mitochondria. It requires an electron-transport chain that operates on the highenergy electrons taken from the activated carrier molecules __________________ and __________________ that are produced by glycolysis and the citric acid cycle. These electrons are transferred through a series of molecules, and the energy released during these transfers is used to generate a gradient of __________________, or __________________. Because their concentration is much __________________ outside than inside the mitochondria, the flow of __________________, or __________________, down the concentration gradient is energetically very __________________ and can thus be coupled to the production of ATP from ADP. Thus, oxidative phosphorylation refers to the oxidation of __________________ and__________________ molecules and the phosphorylation of__________________. Without this process, the yield of ATP from each glucose molecule would be __________________ decreased. o ADP GTP NAD+ o ATP H+ NADH o cytosol higher Pi o electrons inner membrane protons o FADH2 lower severely o favorable matrix slightly o glucose moderately unfavorable
Oxidative phosphorylation is a process that occurs in the (inner membrane) of mitochondria. It requires an electron-transport chain that operates on the high energy electrons taken from the activated carrier molecules (NADH) and (FADH2) that are produced by glycolysis and the citric acid cycle. These electrons are transferred through a series of molecules, and the energy released during these transfers is used to generate a gradient of (H+), or (protons). Because their concentration is much (higher) outside than inside the mitochondria, the flow of (H+), or (protons), down the concentration gradient is energetically very (favorable) and can thus be coupled to the production of ATP from ADP. Thus, oxidative phosphorylation refers to the oxidation of (NADH) and (FADH2) molecules and the phosphorylation of (ADP). Without this process, the yield of ATP from each glucose molecule would be (severely) decreased.
Which of the following statements about PCR is false o PCR uses a DNA polymerase from a thermophilic bacterium. o PCR is particularly powerful because after each cycle of replication, there is a linear increase in the amount of DNA available. o For PCR, every round of replication is preceded by the denaturation of the double-stranded DNA molecules. o The PCR will generate a pool of double-stranded DNA molecules, most of which will have DNA from primers at the 5' ends. o PCR involves a heating step, followed by a cooling step, and then DNA synthesis
PCR is particularly powerful because after each cycle of replication, thereis a linear increase in the amount of DNA available.
What is a PCR? Describe the main steps.
PCR- Polymerase Chain Reaction It make copies of pieces of DNA sequence and uses polymerase to do this. The PCR method is extremely sensitive; it can detect a single DNA molecule in a sample. -Denaturation -Annealing -Extension
Which statement is NOT true about the events/conclusions from studies during the mid-1800s surrounding the discovery of cells? o Cells came to be known as the smallest universal building block of living organisms. o Scientists came to the conclusion that new cells can form spontaneously from the remnants of ruptured cells. o Light microscopy was essential in demonstrating the commonalities between plant and animal tissues. o New cells arise from the growth and division of previously existing cells.
Scientists came to the conclusion that new cells can form spontaneously from the remnants of ruptured cells.
RAP (Fluorescence Recovery after Photobleaching) is a technique to measure membrane fluidity. Describe briefly how it works.
Technique for monitoring the kinetic parameters of a protein by analyzing how fluorescent protein molecules move into an area of the cell bleached by a beam of laser light. Then recovering fluorescence by showing that lateral diffusion of membrane proteins has occurred.
Which of the following statements about the carbohydrate coating of the cell surface is false? o It is not usually found on the cytosolic side of the membrane. o It can play a role in cell-cell adhesion. o The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain. o Specific oligosaccharides can be involved in cell-cell recognition.
The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain.
Indicate whether the statements below are true or false. o A disaccharide consists of a sugar covalently linked to another molecule such as an amino acid or a nucleotide. o The hydroxyl groups on monosaccharides are reaction hotspots and can be replaced by other functional groups to produce derivatives of the original sugar. o The presence of double bonds in the hydrocarbon tail of a fatty acid does not greatly influence its structure. o Glycerol is a three-carbon compound that connects the fatty acid tails with the polar head group in phospholipids.
o A disaccharide consists of a sugar covalently linked to another molecule such as an amino acid or a nucleotide. FALSE o The hydroxyl groups on monosaccharides are reaction hotspots and can be replaced by other functional groups to produce derivatives of the original sugar. TRUE o The presence of double bonds in the hydrocarbon tail of a fatty acid does not greatly influence its structure. FALSE o Glycerol is a three-carbon compound that connects the fatty acid tails with the polar head group in phospholipids. TRUE
Indicate whether the following statements are true or false. o Membrane components in the cell are made in the endoplasmic reticulum. o The Golgi apparatus is made up of a series of membrane-enclosed compartments through which materials destined for secretion must pass. o Lysosomes are small organelles where fatty acid synthesis occurs.
o Membrane components in the cell are made in the endoplasmic reticulum. TRUE o The Golgi apparatus is made up of a series of membrane-enclosed compartments through which materials destined for secretion must pass. TRUE o Lysosomes are small organelles where fatty acid synthesis occurs. FALSE
Match the target of the G protein with the appropriate signaling outcome. o adenylyl cyclase ________ o ion channels _________ o phospholipase C _________ A. cleavage of inositol phospholipids B. increase in cAMP levels C. changes in membrane potential
o adenylyl cyclase B. increase in cAMP levels o ion channels C. changes in membrane potential o phospholipase C A. cleavage of inositol phospholipids
action potential
o effect of a depolarizing stimulus o resting membrane potential o threshold potential o action potential
Name the membrane-enclosed compartments in a eukaryotic cell where each of the functions listed below takes place. o photosynthesis o transcription o oxidative phosphorylation o modification of secreted proteins o degradation of worn-out organelles o new membrane synthesis o breakdown of lipids and toxic molecules
o photosynthesis= chloroplast o transcription= nucleus (additionally can occur in the mt/chloroplast) o oxidative phosphorylation= mitochondria o modification of secreted proteins= golgi apparatus o degradation of worn-out organelles= lysosomes o new membrane synthesis= smooth ER o breakdown of lipids and toxic molecules= peroxisomes
What is the difference between oxidation and reduction?
ox-loss of electrons red-gain of electrons
Your body extracts energy from the food you ingest by catalyzing reactions that essentially "burn" the food molecules in a stepwise fashion. What is another way to describe this process? o reduction o oxidation o dehydration o solvation
oxidation
Which of the following expressions accurately describes the calculation of pH? o pH = -log10[H+] o pH = log10[H+] o pH = -log2[H+] o pH = -log10[OH-]
pH = -log10[H+]
Describe a method to study ion channel activity.
patch clamp:study of single/multiple ion channels in cells
The phosphorylation of a protein is typically associated with a change in activity, the assembly of a protein complex, or the triggering of a downstream signaling cascade. The addition of ubiquitin, a small polypeptide, is another type of covalent modification that can affect the protein function. Ubiquitylation often results in ______________. o membrane association. o protein degradation. o protein secretion. o nuclear translocation.
protein degradation
What is a common feature of all proteins in living cells?
protein folds, bind to other molecules
What type of macromolecule helps package DNA in eukaryotic chromosomes? o lipids o carbohydrates o proteins o RNA
proteins
In a DNA double helix, _____________________. o the two DNA strands are identical. o purines pair with purines. o thymine pairs with cytosine. o the two DNA strands run antiparallel.
the two DNA strands run antiparallel.
DNA can be introduced into bacteria by a mechanism called____________. o transcription. o ligation. o replication. o transformation.
transformation
Proteins that are fully translated in the cytosol do not end up in _______. o the cytosol. o the mitochondria. o the interior of the nucleus. o transport vesicles.
transport vesicles
