Biology 135 Final

List and describe the different phases of meiosis I and meiosis II. What are the differences between meiosis I and meiosis II?

1. How are the traits of parents transmitted to their offspring? Parents pass genes to their offspring; the genes program cells to make specific enzymes and other proteins, whose cumulative action produces an individual's inherited traits. 2. Explain how asexually reproducing organisms produce offspring that are genetically identical to each other and to their parents. Such organisms reproduce by mitosis, which generates offspring whose genomes are exact copies of the parent's genome (in the absence of mutation) 3. What are somatic cells? Body cells; any cell of a living organism other than the reproductive cells. 4. Homologous chromosomes or homologs are a pair of two chromosomes with the same length, centromere position, and staining pattern in a karyotype. What is the relationship of these two pairs of chromosomes? They carry genes controlling the same inherited materials 5. Why are X and Y chromosomes exceptions to the general pattern of homologous chromosomes? What is the name given to the X and Y chromosomes? Human females have a homologous pair of X chromosomes (XX), but males have one X and one Y chromosome (XY). Only small parts of the X and Y are homologous. Most of the genes carried on the X chromosome do not have counterparts on the tiny Y chromosomes and the Y has genes lacking on the X. These are called the sex chromosomes. 6. What is the name given to all other chromosomes? Autosomes 7. A cat has a diploid chromosome number of 38. How many chromosomes does a cat inherit from each parent? How many chromosomes are present in a cat's gametes? How many chromosomes are present in a cat's somatic cells? 2n=38. So n=19. Therefore, 19 chromosomes are inherited from each parent. Gametes (haploid) have 19 chromosomes. Somatic cells (diploid) have 38. 8. What is the female gamete? What is the male gamete? Are these cells haploid of diploid? What does the fusion of these cells produce? Is the resulting haploid or diploid? Why? Female gamete is egg. Male gamete is sperm. These are haploid cells. The fusion of these cells produces a diploid zygote. It is diploid because it receives the haploid number from both the sperm and the egg. 9. What two things happen in Prophase I that increase genetic variability in offspring? What is the relationship of the chromosomes that participate in this phenomenon? Synapsis and crossing over. During prophase I, replicated homologs pair up and become physically connected along their lengths by a zipper like proteins structure called the synaptonemal complex this is called synapsis. Genetic rearrangement between non-sister chromatids, crossing over, then occurs. 10. At the end of Telophase I and cytokinesis, how many cells have formed? Are these cells haploid or diploid? Two haploid cells; each chromosome still consist of two sister chromatids. 11. At the end of Telophase II and cytokinesis, how many cells have formed? Are these cells haploid or diploid? 4 haploid daughter cells. 12. How are the chromosomes in a cell at metaphase of mitosis similar to and different from the chromosomes in a cell at metaphase II of meiosis II? The chromosomes are similar in that each is composed of two sister chromatids and the individual chromosomes are positioned similarly on the metaphase plate. The chromosome differ in that in a mitotically dividing cell, sister chromatids of each chromosome are genetically identical, but in a meiotically dividing cell, sister chromatids are genetically distinct because of crossing over in meiosis I. Moreover, the chromosomes in metaphase of mitosis can be a diploid set or haploid set, but the chromosomes in metaphase of meiosis II always consist of a haploid set. 13. In what types of organisms do we see genetic variation? Organisms that reproduce sexually 14. List and explain the three mechanisms that contribute to the genetic variation. 1) Independent Assortment: because each homologous pair of 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..... 2n possibilities 2) Crossing Over: production of recombinant chromosomes in prophase I of meiosis 3) Random Fertilization: any sperm with its many possible chromosome combination due to independent assortment, can fuse with any egg with its many possible chromosome combination due to independent assortment.... 2nx2n possibilities 15. The diploid number for fruit flies is 8, while that for grasshoppers is 46. If no crossing over took place, would the genetic variation among offspring from a given pair of parents be greater in fruit flies or grasshoppers? Explain. Without crossing over, independent assortment of chromosomes during meiosis I theoretically can generate 2n possible haploid gametes, and random fertilization can produce 2nx2n possible diploid zygotes. Because the haploid number (n) in grasshoppers is more than that of the 4 in fruit flies, grasshoppers would be expected to have a greater variety of zygotes than fruit flies 16. What is the original source of all different versions of an allele? Mutations in a gene lead to a different versions (alleles) of that gene 17. Under what circumstances would crossing over during meiosis not contribute to genetic variation among daughter cells? Crossing over contributes to genetic variation only when it involves the rearrangement of different alleles. If the segments of the maternal and paternal chromatids that undergo crossing over are genetically identical and thus have the same two alleles for every gene, then the recombinant chromosomes will be genetically equivalent to the parental chromosomes.

Describe the emergent properties of water which are essential for life on earth

1. Solvent properties of water 2. Cohesion and adhesion of water: Water can stick to itself (cohesion) and other molecules (adhesion). 3. Specific heat, heat of vaporization, and density of water: Water has a high heat capacity and heat of vaporization, and ice—solid water—is less dense than liquid water. Cohesion of Water The cohesion of water is the process of hydrogen bonding of water molecules to other water molecules. This property is essential in plants. The evaporation of water from the leaves of a tree, in effect, pulls on the other water molecules through their cohesive hydrogen bonds. This bonding extends to the roots of the tree pulling water directly from the soil. As the water travels up the tree vein the process of adhesion, the hydrogen bonding of water to another molecule, is employed to resist the forces of gravity 4. Frozen Water Expands When water freezes it becomes less dense than it is at its liquid form. This is important to prevent a runaway freezing effect on bodies of water. If water was more dense in solid form it would freeze at the surface and then sink to the bottom. This process repeated would consume all of the bodies of water with ice. Life in an ocean of solid ice would be difficult. However, frozen water is less dense than the liquid form, therefore it floats. Floating ice on bodies of water provide the additional benefit of insulation. The ice layer on the surface insulates the heat of the water below allowing for suitable water temperatures for life.

What is an enzyme? What is an active site of an enzyme? What is an energy barrier (Ea)?

A.enzymes form complexes with their substrates.B.enzymes lower the activation energy for chemical reactions.C.enzymes change the Keq for chemical reactions.D.many enzymes change shape slightly when substrate binds.E.reactions occur at the "active site" of enzymes, where a precise 3D orientation of amino acids is an important feature of catalysis. Enzymes do not: Change the equilibrium constant for a reaction. Keq depends only on the difference in energy level between reactants and products. Change ΔG for a reaction. As shown in the graphs above, enzymes only lower activation energy, but do not change the difference in energy levels between reactants and products. Convert a nonspontaneous reaction into a spontaneous reaction.

What is the cell theory?

All living organisms are composed of one or more cells. The cell is the basic unit of structure and organization in organisms. Cells arise from pre-existing cells.

Know the main cellular functions for each type of organic molecule

Carbohydrates: provide energy to the body, particularly through glucose, a simple sugar. Lipids: Cells store energy for long-term use in the form of lipids called fats. nucleic acids: Make up DNA and RNA Proteins: They do most of the work in cells and are required for the structure, function, and regulation of the body's tissues and organs.

What are the key roles of cell division?

Cellular division has three main functions: (1) the reproduction of an entire unicellular organism, (2) the growth and repair of tissues in multicellular animals, and (3) the formation of gametes (eggs and sperm) for sexual reproduction in multicellular animals

Explain what the process of cytokinesis is and explain how it is different between animal and plant cells.

Cytokinesis occurs in mitosis and meiosis for both plant and animal cells. The ultimate objective is to divide the parent cell into daughter cells. In plants , this occurs when a cell wall forms in between the daughter cells. In animals , this occurs when a cleavage furrow forms.Jul 10, 2017

The genetic code consists of triplet codons; can you explain what that means? What is the common sequence of the start codon? What are the sequences of the three stop codons? Can you explain what the redundancy, universality and unambiguous nature of the genetic code mean?

Email Introduction Have you ever written a secret message to one of your friends? If so, you may have used some kind of code to keep the message hidden. For instance, you may have replaced the letters of the word with numbers or symbols, following a particular set of rules. In order for your friend on the other end to understand the message, he or she would need to know the code and apply the same set of rules, in reverse, to figure out what you had written. As it turns out, decoding messages is also a key step in gene expression, the process in which information from a gene is used to construct a protein (or other functional product). How are the instructions for building a protein encoded in DNA, and how are they deciphered by the cell? In this article, we'll take a closer look at the genetic code, which allows DNA and RNA nucleotide sequences to be translated into the amino acids they represent. Overview: Gene expression and the genetic code Genes that provide instructions for proteins are expressed in a two-step process. In transcription, the DNA sequence of a gene is "rewritten" using RNA nucleotides. In eukaryotes, the RNA must go through additional processing steps to become a messenger RNA, or mRNA. In translation, the sequence of nucleotides in the mRNA is "translated" into a sequence of amino acids in a polypeptide (protein or protein subunit). Cells decode mRNAs by reading their nucleotides in groups of three, called codons. Each codon specifies a particular amino acid, or, in some cases, provides a "stop" signal that ends translation. In addition, the codon AUG has a special role, serving as the start codon where translation begins. The complete set of correspondences between codons and amino acids (or stop signals) is known as the genetic code. [Codon table]Genetic code table. Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons. AUG is the codon for methionine, and is also the start codon. The mRNA sequence is: 5'-AUGAUCUCGUAA-5' Translation involves reading the mRNA nucleotides in groups of three, each of which specifies and amino acid (or provides a stop signal indicating that translation is finished). 3'-AUG AUC UCG UAA-5' AUG \rightarrow→right arrow Methionine AUC \rightarrow→right arrow Isoleucine UCG \rightarrow→right arrow Serine UAA \rightarrow→right arrow "Stop" Polypeptide sequence: (N-terminus) Methionine-Isoleucine-Serine (C-terminus) In the rest of this article, we'll more closely at the genetic code. First, we'll see how it was discovered. Then, we'll look more deeply at its properties, seeing how it can be used to predict the polypeptide encoded by an mRNA. Code crackers: How the genetic code was discovered To crack the genetic code, researchers needed to figure out how sequences of nucleotides in a DNA or RNA molecule could encode the sequence of amino acids in a polypeptide. Why was this a tricky problem? In one of the simplest potential codes, each nucleotide in an DNA or RNA molecule might correspond to one amino acid in a polypeptide. However, this code cannot actually work, because there are 202020 amino acids commonly found in proteins and just 444 nucleotide bases in DNA or RNA. Thus, researchers knew that the code must involve something more complex than a one-to-one matching of nucleotides and amino acids. The triplet hypothesis In the mid-1950s, the physicist George Gamow extended this line of thinking to deduce that the genetic code was likely composed of triplets of nucleotides. That is, he proposed that a group of 333 successive nucleotides in a gene might code for one amino acid in a polypeptide. Gamow's reasoning was that even a doublet code (222 nucleotides per amino acid) would not work, as it would allow for only 161616 ordered groups of nucleotides (4^2424, squared), too few to account for the 202020 standard amino acids used to build proteins. A code based on nucleotide triplets, however, seemed promising: it would provide 646464 unique sequences of nucleotides (4^3434, cubed), more than enough to cover the 202020 amino acids. [More about the math] 16166464 4422 1616 44\cdotdot44=equals 4 \cdot4 = 164, dot, 4, equals, 16 3344 44\cdotdot44\cdotdot44=equals 4 \cdot 4 \cdot 4 =644, dot, 4, dot, 4, equals, 64 Nirenberg, Khorana, and the identification of codons Gamow's triplet hypothesis seemed logical and was widely accepted. However, it had not been experimentally proven, and researchers still did not know which triplets of nucleotides corresponded to which amino acids. The cracking of the genetic code began in 1961, with work from the American biochemist Marshall Nirenberg. For the first time, Nirenberg and his colleagues were able to identify specific nucleotide triplets that corresponded to particular amino acids. Their success relied on two experimental innovations: A way to make artificial mRNA molecules with specific, known sequences. A system to translate mRNAs into polypeptides outside of a cell (a "cell-free" system). Nirenberg's system consisted of cytoplasm from burst E. coli cells, which contains all of the materials needed for translation. First, Nirenberg synthesized an mRNA molecule consisting only of the nucleotide uracil (called poly-U). When he added poly-U mRNA to the cell-free system, he found that the polypeptides made consisted exclusively of the amino acid phenylalanine. Because the only triplet in poly-U mRNA is UUU, Nirenberg concluded that UUU might code for phenylalanine. Using the same approach, he was able to show that poly-C mRNA was translated into polypeptides made exclusively of the amino acid proline, suggesting that the triplet CCC might code for proline. Other researchers, such as the biochemist Har Gobind Khorana at University of Wisconsin, extended Nirenberg's experiment by synthesizing artificial mRNAs with more complex sequences. For instance, in one experiment, Khorana generated a poly-UC (UCUCUCUCUC...) mRNA and added it to a cell-free system similar to Nirenberg's. The poly-UC mRNA that it was translated into polypeptides with an alternating pattern of serine and leucine amino acids. These and other results unambiguously confirmed that the genetic code was based on triplets, or codons. Today, we know that serine is encoded by the codon UCU, while leucine is encoded by CUC. By 1965, using the cell-free system and other techniques, Nirenberg, Khorana, and their colleagues had deciphered the entire genetic code. That is, they had identified the amino acid or "stop" signal corresponding to each one of the 646464 nucleotide codons. For their contributions, Nirenberg and Khorana (along with another genetic code researcher, Robert Holley) received the Nobel Prize in 1968. _Left: Image modified from "Marshall Nirenberg and Heinrich Matthaei," by N. MacVicar (public domain). Right: "Har Gobind Khorana" (public domain)._ Properties of the genetic code As we saw above, the genetic code is based on triplets of nucleotides called codons, which specify individual amino acids in a polypeptide (or "stop" signals at its end). The codons of an mRNA are "read" one by one inside protein-and-RNA structures called ribosomes, starting at the 5' end of the gene and moving towards the 3' end. Let's take a closer look at the genetic code in the context of translation. Types of codons (start, stop, and "normal") Genetic code table. Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons. AUG is the codon for methionine, and is also the start codon. _Image credit: "The genetic code," by OpenStax College, Biology (CC BY 3.0)._ Translation always begins at a start codon, which has the sequence AUG and encodes the amino acid methionine (Met) in most organisms. Thus, every polypeptide typically starts with methionine, although the initial methionine may be snipped off in later processing steps. A start codon is required to begin translation, but the codon AUG can also appear later in the coding sequence of an an mRNA, where it simply specifies the amino acid methionine. Once translation has begun at the start codon, the following codons of the mRNA will be read one by one, in the 5' to 3' direction. As each codon is read, the matching amino acid is added to the C-terminus of the polypeptide. Most of the codons in the genetic code specify amino acids and are read during this phase of translation. [How do you read the codon table?] Translation continues until a stop codon is reached. There are three stop codons in the genetic code, UAA, UAG, and UGA. Unlike start codons, stop codons don't correspond to an amino acid. Instead, they act as "stop" signals, indicating that the polypeptide is complete and causing it to be released from the ribosome. More nucleotides may appear after the stop codon in the mRNA, but will not be translated as part of the polypeptide. Reading frame The start codon is critical because it determines where translation will begin on the mRNA. Most importantly, the position of the start codon determines the reading frame, or how the mRNA sequence is divided up into groups of three nucleotides inside the ribosome. As shown in the diagram below, the same sequence of nucleotides can encode completely different polypeptides depending on the frame in which it's read. The start codon determines which frame is chosen and thus ensures that the correct polypeptide is produced. To see what reading frame is, it's helpful to consider an analogy using words and letters. The following message makes sense to us because we read it in the correct frame (divide it correctly into groups of three letters): MOM AND DAD ARE MAD. If we shift the reading frame by grouping letters into threes starting one position later, however, we get: OMA NDD ADA REM AD. The frameshift results in a message that no longer makes sense. An important point to note here is that the nucleotides in a gene are not physically organized into groups of three. Instead, what constitutes a codon is simply a matter of where the ribosome begins reading, and of what sequence of nucleotides comes after the start codon. Mutations that insert or delete a single nucleotide may alter reading frame, resulting in the production of a "gibberish" protein similar to the scrambled sentence in the example above. One amino acid, many codons As previously mentioned, the genetic code consists of 646464 unique codons. But if there are only 202020 amino acids, what are the other 444444 codons doing? As we saw, a few are stop codons, but most are not. Instead, the genetic code turns out to be a degenerate code, meaning that some amino acids are specified by more than one codon. For example, proline is represented by four different codons (CCU, CCC, CCA, and CCG). If any one of these codons appears in an mRNA, it will cause proline to be added to the polypeptide chain. Most of the amino acids in the genetic code are encoded by at least two codons. In fact, methionine and tryptophan are the only amino acids specified by a single codon. Importantly, the reverse isn't true: each codon specifies just one amino acid or stop signal. Thus, there's no ambiguity (uncertainty) in the genetic code. A particular codon in an mRNA will always be predictably translated into a particular amino acid or stop signal. The genetic code is (nearly) universal With some minor exceptions, all living organisms on Earth use the same genetic code. This means that the codons specifying the 202020 amino acids in your cells are the same as those used by the bacteria inhabiting hydrothermal vents at the bottom of the Pacific Ocean. Even in organisms that don't use the "standard" code, the differences are relatively small, such as a change in the amino acid encoded by a particular codon. A genetic code shared by diverse organisms provides important evidence for the common origin of life on Earth. That is, the many species on Earth today likely evolved from an ancestral organism in which the genetic code was already present. Because the code is essential to the function of cells, it would tend to remain unchanged in species across generations, as individuals with significant changes might be unable to survive. This type of evolutionary process can explain the remarkable similarity of the genetic code across present-day organisms.

Recognize/know what endocytosis and exocytosis are. What are the three types of endocytosis we discussed in class? Understand each one of them and how they differ.

Endocytosis: Endocytosis is the process by which materials move into the cell. There are three types of endocytosis: Endocytosis consists of phagocytosis, pinocytosis, and receptor -mediated endocytosis. ... Phagocytosis is the taking in of large food particles, while pinocytosis takes in liquid particles. Receptor-mediated endocytosis uses special receptor proteins to help carry large particles across the cell membrane. Exocytosis: removes or secretes substances such as hormones or enzymes

similarities and differences between prokaryotic and eukaryotic cells.

Eukaryotic cells contain membrane-bound organelles, including a nucleus. Eukaryotes can be single-celled or multi-celled, such as you, me, plants, fungi, and insects. Bacteria are an example of prokaryotes. Prokaryotic cells do not contain a nucleus or any other membrane-bound organelle.

List and explain chemical and physical factors that affect enzyme function.

Factor 1: Concentration of Enzyme Enzyme Concentration As the concentration of the enzyme is increased, the velocity of the reaction proportionately increases. This property is used for determining the activities of serum enzymes during the diagnosis of diseases. Factor 2: Concentration of Substrate Substrate Enzyme Concentration In the presence of a given amount of enzyme, the rate of enzymatic reaction increases as the substrate concentration increases until a limiting rate is reached, after which further increase in the substrate concentration produces no significant change in the reaction rate. At this point, so much substrate is present that essentially all of the enzyme active sites have substrate bound to them. In other words, the enzyme molecules are saturated with substrate. The excess substrate molecules cannot react until the substrate already bound to the enzymes has reacted and been released (or been released without reacting). Factor 3: Effect of Temperature The protein nature of the enzymes makes them extremely sensitive to thermal changes. Enzyme activity occurs within a narrow range of temperatures compared to ordinary chemical reactions. As you have seen, each enzyme has a certain temperature at which it is more active. This point is called the optimal temperature, which ranges between 37 to 40C°. The enzyme activity gradually lowers as the temperature rises more than the optimal temperature until it reaches a certain temperature at which the enzyme activity stops completely due to the change of its natural composition. On the other hand, if the temperature lowers below the optimal temperature, the enzyme activity lowers until the enzyme reaches a minimum temperature at which the enzyme activity is the least. The enzyme activity stops completely at 0C°, but if the temperature rises again, then the enzyme gets reactivated once more. Enzyme activity and temperature Factor 4: Effect of pH The potential of hydrogen (pH) is the best measurement for determining the concentration of hydrogen ion (H+)in a solution. It also determines whether the liquid is acidic, basic or neutral. Generally, all liquids with a pH below 7 are called acids, whereas liquids with a pH above 7 are called bases or alkalines. Liquids with pH 7 are neutral and equal the acidity of pure water at 25 C°. You can determine pH of any solution using the pH indicators. pH Indicators Enzymes are protein substances that contain acidic carboxylic groups (COOH-) and basic amino groups (NH2). So, the enzymes are affected by changing the pH value. Each enzyme has a pH value that it works at with maximum efficiency called the optimal pH. If the pH is lower or higher than the optimal pH, the enzyme activity decreases until it stops working. For example, pepsin works at a low pH, i.e, it is highly acidic, while trypsin works at a high pH, i.e, it is basic. Most enzymes work at neutral pH 7.4. Enzyme PH activity Factor 5: Effect of Activators Some of the enzymes require certain inorganic metallic cations, like Mg2+, Mn2+, Zn2+, Ca2+, Co2+, Cu2+, Na+, K+ etc., for their optimum activity. Rarely, anions are also needed for enzyme activity, e.g. a chloride ion (CI-) for amylase.

Define the terms gene expression, Transcription, Translation

Gene expression is the process by which the instructions in our DNA are converted into a functional product, such as a protein. ... There are two key steps involved in making a protein, transcription and translation.

List and explain mechanisms which produce genetic variation

Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

Useful terms for Gene Expression

Glossary of terms amino acids - twenty molecules that are the building blocks of proteins. String of amino acids make up protein's primary structure. anticodon - a sequence of three nucleotides on a tRNA molecule that bond to a complementary sequence on an mRNA molecule. The anticodon sequence determines the amino acid that the tRNA carries. codon - a sequence of three nucleotides on a mRNA molecule that encode a specific amino acid complementary - matching, such as between pairs of nucleotides in a DNA molecule DNA - the molecule that stores and encodes an organism's genetic information. DNA is a double helix molecule made up of two twisted strands that are held together by hydrogen bonds between paired nucleotides. The two strands are chemically oriented in opposite directions. enzyme - a type of protein that performs cellular activities hydrogen bond - a weak bond that holds together complementary base pairs in a DNA molecule 9 messenger RNA (mRNA) - a type of RNA that conveys genetic instructions on how to assemble proteins from the cell's DNA to its protein-making machinery. mRNA contains a copy of one or a few genes from a cell's chromosome. nucleotides - the building blocks of DNA and RNA molecules that contain the cell's genetic code. Adenosine, cytidine, guanosine, thymidine, and uridine are all nucleotides. polypeptide chain - the long chain of amino acids that is created during translation. A polypeptide chain becomes a protein when it folds into its final functional shape. protein - a molecular machine that carries out vital tasks in the cell, such as providing structural support, processing nutrients, copying a cell's DNA, and regulating other cellular functions. Proteins are made of long chains of amino acids that fold into complex three-dimensional shapes. Each type protein has a unique amino acid sequence and a specific function in the cell. replication - the process in which a cell's DNA is copied prior to cellular reproduction ribosomal RNA (rRNA) - a type of RNA that assists in the protein-making process. rRNA is found in the cell's ribosomes. ribosome - a molecular machine that coordinates protein assembly. A ribosome consists of two parts, a large and small subunit, which clamp around an mRNA molecule that needs to be translated. A ribosome is composed of several proteins with tightly coiled rRNA wrapped around them. RNA - a polymer made of a single strand of nucleotides. RNA contains the same nucleotides as DNA, with the substitution of uridine for thymidine. stop codon - a three-nucleotide sequence that signals the cell to end protein synthesis during translation transcription - the process in which a cell's DNA is copied into messenger RNA, which is then read by the cell's protein-making machinery. Transcription is a major step in the transfer of information in biology. Transcribe is the verb associated with transcription. transfer RNA (tRNA) - a type of RNA that is folded into a three-dimensional structure. tRNA carries and transfers an amino acid to the polypeptide chain being assembled during translation. translation - the process in which a cell converts genetic information carried in an mRNA molecule into a protein. Translation is a major step in the transfer of information in biology. In this case, translate is the verb associated with translation.

What are the inputs and outputs of glycolysis, TCA cycle, ETS, fermentation and photosynthesis?

Glycolysis. In glycolysis, glucose—a six-carbon sugar—undergoes a series of chemical transformations. In the end, it gets converted into two molecules of pyruvate, a three-carbon organic molecule. In these reactions, ATP is made, and \text{NAD}^+NAD+start text, N, A, D, end text, start superscript, plus, end superscript is converted to \text{NADH}NADHstart text, N, A, D, H, end text. Pyruvate oxidation. Each pyruvate from glycolysis goes into the mitochondrial matrix—the innermost compartment of mitochondria. There, it's converted into a two-carbon molecule bound to Coenzyme A, known as acetyl CoA. Carbon dioxide is released and \text{NADH}NADHstart text, N, A, D, H, end text is generated. Citric acid cycle. The acetyl CoA made in the last step combines with a four-carbon molecule and goes through a cycle of reactions, ultimately regenerating the four-carbon starting molecule. ATP, \text{NADH}NADHstart text, N, A, D, H, end text, and \text{FADH}_2FADH2​start text, F, A, D, H, end text, start subscript, 2, end subscript are produced, and carbon dioxide is released. Oxidative phosphorylation. The \text{NADH}NADHstart text, N, A, D, H, end text and \text{FADH}_2FADH2​start text, F, A, D, H, end text, start subscript, 2, end subscript made in other steps deposit their electrons in the electron transport chain, turning back into their "empty" forms (\text{NAD}^+NAD+start text, N, A, D, end text, start superscript, plus, end superscript and \text{FAD}FADstart text, F, A, D, end text). As electrons move down the chain, energy is released and used to pump protons out of the matrix, forming a gradient. Protons flow back into the matrix through an enzyme called ATP synthase, making ATP. At the end of the electron transport chain, oxygen accepts electrons and takes up protons to form water.

know the difference between the different types of chemical bonds: Non-polar and polar covalent bonds, ionic bond, hydrogen bond and Van Der Waals interactions. Know how they form and be able to order them from strongest to weakest.

Hydrogen bonds : weakest. Ionic bonds : moderate or relatively strong. Covalent bond : strongest. There are two basic types of covalent bonds: polar and non-polar. In a polar covalent bond, the electrons are unequally shared by the atoms. Non-polar covalent bonds form between two atoms of the same element, or between atoms of different elements that share electrons more or less equally. Hydrogen bonds In a polar covalent bond containing hydrogen (e.g., an O-H bond in a water molecule), the hydrogen will have a slight positive charge because the bond electrons are pulled more strongly toward the other element. Ionic bonds are bonds formed between ions with opposite charges. Van Der Waals interactions are weak attractions between molecules. However, unlike hydrogen bonds, they can occur between atoms or molecules of any kind, and they depend on temporary imbalances in electron distribution.

Explain what is RNA splicing? Include these key words in your explanation: pre-mRNA, mRNA, intron, exon, spliceosome.

In RNA splicing, specific parts of the pre-mRNA, called introns are recognized and removed by a protein-and-RNA complex called the spliceosome. ... During splicing, the introns are revmoved from the pre-mRNA, and the exons are stuck together to form a mature mRNA that does not contain the intron sequences.

Explain how the sister chromatids are separated during anaphase and relate that to the role of the mitotic spindle

In mitosis, the cohesion of sister chromatids at the centromere lapses at the end of metaphase, enabling the daughter chromosomes to move apart towards the two poles of the spindle. In meiosis, in contrast, the chromatids remain joined at the centromere at the first anaphase.

Translation occurs in three stages: initiation, elongation and termination; explain what is occurring at each stage. Be thorough.

Introduction Take a moment to look at your hands. The bone, skin, and muscle you see are made up of cells. And each of those cells contains many millions of proteins^11start superscript, 1, end superscript. As a matter of fact, proteins are key molecular "building blocks" for every organism on Earth! How are these proteins made in a cell? For starters, the instructions for making proteins are "written" in a cell's DNA in the form of genes. If that idea is new to you, you may want to check out the section on DNA to RNA to protein (central dogma) before getting into the nitty-gritty of building proteins. Basically, a gene is used to build a protein in a two-step process: Step 1: transcription! Here, the DNA sequence of a gene is "rewritten" in the form of RNA. In eukaryotes like you and me, the RNA is processed (and often has a few bits snipped out of it) to make the final product, called a messenger RNA or mRNA. Step 2: translation! In this stage, the mRNA is "decoded" to build a protein (or a chunk/subunit of a protein) that contains a specific series of amino acids. [What exactly is an "amino acid"?] The central dogma of molecular biology states that information flows from DNA (genes) to mRNA through the process of transcription, and then to proteins through the process of translation. _Image modified from "Central dogma of molecular biochemistry with enzymes," by Daniel Horspool (CC BY-SA 3.0). The modified image is licensed under a CC BY-SA 3.0 license._ In this article, we'll zoom in on translation, getting an overview of the process and the molecules that carry it out. The genetic code During translation, a cell "reads" the information in a messenger RNA (mRNA) and uses it to build a protein. Actually, to be a little more techical, an mRNA doesn't always encode—provide instructions for—a whole protein. Instead, what we can confidently say is that it always encodes a polypeptide, or chain of amino acids. [Wait, what is the difference?] Genetic code table. Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons. AUG is the codon for methionine, and is also the start codon. _Image credit: "The genetic code," by OpenStax College, Biology (CC BY 3.0)._ In an mRNA, the instructions for building a polypeptide are RNA nucleotides (As, Us, Cs, and Gs) read in groups of three. These groups of three are called codons. There are 616161 codons for amino acids, and each of them is "read" to specify a certain amino acid out of the 202020 commonly found in proteins. One codon, AUG, specifies the amino acid methionine and also acts as a start codon to signal the start of protein construction. There are three more codons that do not specify amino acids. These stop codons, UAA, UAG, and UGA, tell the cell when a polypeptide is complete. All together, this collection of codon-amino acid relationships is called the genetic code, because it lets cells "decode" an mRNA into a chain of amino acids. Each mRNA contains a series of codons (nucleotide triplets) that each specifies an amino acid. The correspondence between mRNA codons and amino acids is called the genetic code. 5' AUG - Methionine ACG - Threonine GAG - Glutamate CUU - Leucine CGG - Arginine AGC - Serine UAG - Stop 3' Image modified from "RNA-codons-aminoacids," by Thomas Splettstoesser (CC BY-SA 4.0). The modified image is licensed under a CC BY-SA 4.0 license. Overview of translation How is an mRNA "read" to make a polypeptide? Two types of molecules with key roles in translation are tRNAs and ribosomes. Transfer RNAs (tRNAs) Transfer RNAs, or tRNAs, are molecular "bridges" that connect mRNA codons to the amino acids they encode. One end of each tRNA has a sequence of three nucleotides called an anticodon, which can bind to specific mRNA codons. The other end of the tRNA carries the amino acid specified by the codons. There are many different types of tRNAs. Each type reads one or a few codons and brings the right amino acid matching those codons. Ribosomes are composed of a small and large subunit and have three sites where tRNAs can bind to an mRNA (the A, P, and E sites). Each tRNA vcarries a specific amino acid and binds to an mRNA codon that is complementary to its anticodon. Image modified from "Translation: Figure 3," by OpenStax College, Biology (CC BY 4.0). Ribosomes Ribosomes are the structures where polypeptides (proteins) are built. They are made up of protein and RNA (ribosomal RNA, or rRNA). Each ribosome has two subunits, a large one and a small one, which come together around an mRNA—kind of like the two halves of a hamburger bun coming together around the patty. The ribosome provides a set of handy slots where tRNAs can find their matching codons on the mRNA template and deliver their amino acids. These slots are called the A, P, and E sites. Not only that, but the ribosome also acts as an enzyme, catalyzing the chemical reaction that links amino acids together to make a chain. Want to learn more about the structure and function of tRNAs and ribosomes? Check out the tRNA and ribosomes article! Steps of translation Your cells are making new proteins every second of the day. And each of those proteins must contain the right set of amino acids, linked together in just the right order. That may sound like a challenging task, but luckily, your cells (along with those of other animals, plants, and bacteria) are up to the job. To see how cells make proteins, let's divide translation into three stages: initiation (starting off), elongation (adding on to the protein chain), and termination (finishing up). Getting started: Initiation In initiation, the ribosome assembles around the mRNA to be read and the first tRNA (carrying the amino acid methionine, which matches the start codon, AUG). This setup, called the initiation complex, is needed in order for translation to get started. Extending the chain: Elongation Elongation is the stage where the amino acid chain gets longer. In elongation, the mRNA is read one codon at a time, and the amino acid matching each codon is added to a growing protein chain. Each time a new codon is exposed: A matching tRNA binds to the codon The existing amino acid chain (polypeptide) is linked onto the amino acid of the tRNA via a chemical reaction The mRNA is shifted one codon over in the ribosome, exposing a new codon for reading Elongation has three stages: 1) The anticodon of an incoming tRNA pairs with the mRNA codon exposed in the A site. 2) A peptide bond is formed between the new amino acid (in the A site) and the previously-added amino acid (in the P site), transferring the polypeptide from the P site to the A site. 3) The ribosome moves one codon down on the mRNA. The tRNA in the A site (carrying the polypeptide) shifts to the P site. The tRNA in the P site shifts to the E site and exits the ribosome. Image based on similar diagram in Reece et al.^22squared During elongation, tRNAs move through the A, P, and E sites of the ribosome, as shown above. This process repeats many times as new codons are read and new amino acids are added to the chain. For more details on the steps of elongation, see the stages of translation article. Finishing up: Termination Termination is the stage in which the finished polypeptide chain is released. It begins when a stop codon (UAG, UAA, or UGA) enters the ribosome, triggering a series of events that separate the chain from its tRNA and allow it to drift out of the ribosome. After termination, the polypeptide may still need to fold into the right 3D shape, undergo processing (such as the removal of amino acids), get shipped to the right place in the cell, or combine with other polypeptides before it can do its job as a functional protein.

What are the three stages of transcription? Explain with good detail what happens during each stage; in your explanation include these key words: promotor sequences, start point, transcript unit, termination sequences, RNA polymerase II, transcriptions factors, TATA box, template strand, coding strand, RNA transcript, rate of transcription, direction of transcription, polyadenylation sequence

Key points: Transcription is the process in which a gene's DNA sequence is copied (transcribed) to make an RNA molecule. RNA polymerase is the main transcription enzyme. Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins). RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule. Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished. Introduction What makes death cap mushrooms deadly? These mushrooms get their lethal effects by producing one specific toxin, which attaches to a crucial enzyme in the human body: RNA polymerase.^11start superscript, 1, end superscript Photograph of Amanita phalloides (death cap) mushrooms. _Image modified from "Amanita phalloides," by Archenzo (CC BY-SA 3.0). The modified image is licensed under a CC BY-SA 3.0 license._ RNA polymerase is crucial because it carries out transcription, the process of copying DNA (deoxyribonucleic acid, the genetic material) into RNA (ribonucleic acid, a similar but more short-lived molecule). Transcription is an essential step in using the information from genes in our DNA to make proteins. Proteins are the key molecules that give cells structure and keep them running. Blocking transcription with mushroom toxin causes liver failure and death, because no new RNAs—and thus, no new proteins—can be made.^22squared Transcription is essential to life, and understanding how it works is important to human health. Let's take a closer look at what happens during transcription. Transcription overview Transcription is the first step of gene expression. During this process, the DNA sequence of a gene is copied into RNA. Before transcription can take place, the DNA double helix must unwind near the gene that is getting transcribed. The region of opened-up DNA is called a transcription bubble. In transcription, a region of DNA opens up. One strand, the template strand, serves as a template for synthesis of a complementary RNA transcript. The other strand, the coding strand, is identical to the RNA transcript in sequence, except that it has uracil (U) bases in place of thymine (T) bases. Example: Coding strand: 5'-ATGATCTCGTAA-3' Template strand: 3'-TACTAGAGCATT-5' RNA transcript: 5'-AUGAUCUCGUAA-3' In translation, the RNA transcript is read to produce a polypeptide. Example: RNA transcript: 5'-AUG AUC UCG UAA-3' Polypeptide: (N-terminus) Met - Ile - Ser - [STOP] (C-terminus) Transcription uses one of the two exposed DNA strands as a template; this strand is called the template strand. The RNA product is complementary to the template strand and is almost identical to the other DNA strand, called the nontemplate (or coding) strand. However, there is one important difference: in the newly made RNA, all of the T nucleotides are replaced with U nucleotides. The site on the DNA from which the first RNA nucleotide is transcribed is called the +1+1plus, 1 site, or the initiation site. Nucleotides that come before the initiation site are given negative numbers and said to be upstream. Nucleotides that come after the initiation site are marked with positive numbers and said to be downstream. If the gene that's transcribed encodes a protein (which many genes do), the RNA molecule will be read to make a protein in a process called translation. [Are there steps between transcription and translation?] RNA polymerase RNA polymerases are enzymes that transcribe DNA into RNA. Using a DNA template, RNA polymerase builds a new RNA molecule through base pairing. For instance, if there is a G in the DNA template, RNA polymerase will add a C to the new, growing RNA strand. RNA polymerase synthesizes an RNA strand complementary to a template DNA strand. It synthesizes the RNA strand in the 5' to 3' direction, while reading the template DNA strand in the 3' to 5' direction. The template DNA strand and RNA strand are antiparallel. RNA transcript: 5'-UGGUAGU...-3' (dots indicate where nucleotides are still being added at 3' end) DNA template: 3'-ACCATCAGTC-5' RNA polymerase always builds a new RNA strand in the 5' to 3' direction. That is, it can only add RNA nucleotides (A, U, C, or G) to the 3' end of the strand. [What do 5' and 3' mean?] RNA polymerases are large enzymes with multiple subunits, even in simple organisms like bacteria. In addition, humans and other eukaryotes have three different kinds of RNA polymerases: I, II, and III. Each one specializes in transcribing certain classes of genes. Transcription initiation To begin transcribing a gene, RNA polymerase binds to the DNA of the gene at a region called the promoter. Basically, the promoter tells the polymerase where to "sit down" on the DNA and begin transcribing. The promoter region comes before (and slightly overlaps with) the transcribed region whose transcription it specifies. It contains recognition sites for RNA polymerase or its helper proteins to bind to. The DNA opens up in the promoter region so that RNA polymerase can begin transcription. Each gene (or, in bacteria, each group of genes transcribed together) has its own promoter. A promoter contains DNA sequences that let RNA polymerase or its helper proteins attach to the DNA. Once the transcription bubble has formed, the polymerase can start transcribing. Promoters in bacteria To get a better sense of how a promoter works, let's look an example from bacteria. A typical bacterial promoter contains two important DNA sequences, the -101010 and -353535 elements. RNA polymerase recognizes and binds directly to these sequences. The sequences position the polymerase in the right spot to start transcribing a target gene, and they also make sure it's pointing in the right direction. [How?]-3535-1010 Once the RNA polymerase has bound, it can open up the DNA and get to work. DNA opening occurs at the -101010 element, where the strands are easy to separate due to the many As and Ts (which bind to each other using just two hydrogen bonds, rather than the three hydrogen bonds of Gs and Cs). Bacterial promoter. The promoter lies at the start of the transcribed region, encompassing the DNA before it and slightly overlapping with the transcriptional start site. The promoter contains two elements, the -35 element and the -10 element. The -35 element is centered about 35 nucleotides upstream of (before) the transcriptional start site (+1), while the -10 element is centered about 10 nucleotides before the transcriptional start site. In this particular example, the sequence of the -35 element (on the coding strand) is 5'-TTGACG-3', while the sequence of the -10 element (on the coding strand) is 5'-TATAAT-3'. The RNA polymerase has regions that specifically bind to the -10 and -35 elements. The -101010 and the -353535 elements get their names because they come 353535 and 101010 nucleotides before the initiation site (+1+1plus, 1 in the DNA). The minus signs just mean that they are before, not after, the initiation site. Promoters in humans In eukaryotes like humans, the main RNA polymerase in your cells does not attach directly to promoters like bacterial RNA polymerase. Instead, helper proteins called basal (general) transcription factors bind to the promoter first, helping the RNA polymerase in your cells get a foothold on the DNA. Many eukaryotic promoters have a sequence called a TATA box. The TATA box plays a role much like that of the -101010 element in bacteria. It's recognized by one of the general transcription factors, allowing other transcription factors and eventually RNA polymerase to bind. It also contains lots of As and Ts, which make it easy to pull the strands of DNA apart. The promoter of a eukaryotic gene is shown. The promoter lies upstream of and slightly overlaps with the transcriptional start site (+1). It contains a TATA box, which has a sequence (on the coding strand) of 5'-TATAAA-3'. The first eukaryotic general transcription factor binds to the TATA box. Then, other general transcription factors bind. Finally, RNA polymerase II and some additional transcription factors bind to the promoter. Elongation Once RNA polymerase is in position at the promoter, the next step of transcription—elongation—can begin. Basically, elongation is the stage when the RNA strand gets longer, thanks to the addition of new nucleotides. During elongation, RNA polymerase "walks" along one strand of DNA, known as the template strand, in the 3' to 5' direction. For each nucleotide in the template, RNA polymerase adds a matching (complementary) RNA nucleotide to the 3' end of the RNA strand. [See the chemical reaction] Polymerization reaction in which a RNA nucleotide triphosphate is added to the existing RNA strand. The RNA nucleotide triphosphate has a series of three phosphate groups attached to it. The innermost phoosphate group reacts with the 3' hydroxyl on the nucleotide at the end of the existing strand, forming a phosphodiester bond that attaches the new nucleotide to the end of the chain. A pyrophosphate (molecule consisting of two phosphate groups) is lost in this process, and is later cleaved into two individual inorganic phosphates. In general, this reaction will occur only when an incoming nucleotide is complementary to the next exposed nucleotide in the DNA strand that serves as a template for RNA synthesis. The RNA strand looks similar to DNA, except that it contains the base uracil in place of thymine and has ribose sugars (which have a hydroxyl group on the 2' carbon) in place of deoxyribose sugars. RNA polymerase synthesizes an RNA transcript complementary to the DNA template strand in the 5' to 3' direction. It moves forward along the template strand in the 3' to 5' direction, opening the DNA double helix as it goes. The synthesized RNA only remains bound to the template strand for a short while, then exits the polymerase as a dangling string, allowing the DNA to close back up and form a double helix. In this example, the sequences of the coding strand, template strand, and RNA transcript are: Coding strand: 5' - ATGATCTCGTAA-3' Template strand: 3'-TACTAGAGCATT-5' RNA: 5'-AUGAUC...-3' (the dots indicate where nucleotides are still being added to the RNA strand at its 3' end) The RNA transcript is nearly identical to the non-template, or coding, strand of DNA. However, RNA strands have the base uracil (U) in place of thymine (T), as well as a slightly different sugar in the nucleotide. So, as we can see in the diagram above, each T of the coding strand is replaced with a U in the RNA transcript. [See a diagram of the bases] DNA nucleotide: lacks a hydroxyl group on the 2' carbon of the sugar (i.e., sugar is deoxyribose). Bears a thymine base that has a methyl group attached to its ring. RNA nucleotide: has a hydroxyl group on the 2' carbon of the sugar (i.e., sugar is ribose). Bears a uracil base that is very similar in structure to thymine, but does not have a methyl group attached to the ring. ^3cubed The picture below shows DNA being transcribed by many RNA polymerases at the same time, each with an RNA "tail" trailing behind it. The polymerases near the start of the gene have short RNA tails, which get longer and longer as the polymerase transcribes more of the gene. In the microscope image shown here, a gene is being transcribed by many RNA polymerases at once. The RNA chains are shortest near the beginning of the gene, and they become longer as the polymerases move towards the end of the gene. This pattern creates a kind of wedge-shaped structure made by the RNA transcripts fanning out from the DNA of the gene. _Image modified from "Transcription label en," by Dr. Hans-Heinrich Trepte (CC BY-SA 3.0). The modified image is licensed under a CC BY-SA 3.0 license._ Transcription termination RNA polymerase will keep transcribing until it gets signals to stop. The process of ending transcription is called termination, and it happens once the polymerase transcribes a sequence of DNA known as a terminator. Termination in bacteria There are two major termination strategies found in bacteria: Rho-dependent and Rho-independent. In Rho-dependent termination, the RNA contains a binding site for a protein called Rho factor. Rho factor binds to this sequence and starts "climbing" up the transcript towards RNA polymerase. Rho-dependent termination. The terminator is a region of DNA that includes the sequence that codes for the Rho binding site in the mRNA, as well as the actual transcription stop point (which is a sequence that causes the RNA polymerase to pause so that Rho can catch up to it). Rho binds to the Rho binding site in the mRNA and climbs up the RNA transcript, in the 5' to 3' direction, towards the transcription bubble where the polymerase is. When it catches up to the polymerase, it will cause the transcript to be released, ending transcription. When it catches up with the polymerase at the transcription bubble, Rho pulls the RNA transcript and the template DNA strand apart, releasing the RNA molecule and ending transcription. Another sequence found later in the DNA, called the transcription stop point, causes RNA polymerase to pause and thus helps Rho catch up.^44start superscript, 4, end superscript Rho-independent termination depends on specific sequences in the DNA template strand. As the RNA polymerase approaches the end of the gene being transcribed, it hits a region rich in C and G nucleotides. The RNA transcribed from this region folds back on itself, and the complementary C and G nucleotides bind together. The result is a stable hairpin that causes the polymerase to stall. Rho-independent termination. The terminator DNA sequence encodes a region of RNA that folds back on itself to form a hairpin. The hairpin is followed by a series of U nucleotides in the RNA (not pictured). The hairpin causes the polymerase to stall, and the weak base pairing between the A nucleotides of the DNA template and the U nucleotides of the RNA transcript allows the transcript to separate from the template, ending transcription. In a terminator, the hairpin is followed by a stretch of U nucleotides in the RNA, which match up with A nucleotides in the template DNA. The complementary U-A region of the RNA transcript forms only a weak interaction with the template DNA. This, coupled with the stalled polymerase, produces enough instability for the enzyme to fall off and liberate the new RNA transcript. [Transcription termination in eukaryotes] 500500-2,2, comma000000^5start superscript, 5, end superscript^6start superscript, 6, end superscript What happens to the RNA transcript? After termination, transcription is finished. An RNA transcript that is ready to be used in translation is called a messenger RNA (mRNA). In bacteria, RNA transcripts are ready to be translated right after transcription. In fact, they're actually ready a little sooner than that: translation may start while transcription is still going on! In the diagram below, mRNAs are being transcribed from several different genes. Although transcription is still in progress, ribosomes have attached each mRNA and begun to translate it into protein. When an mRNA is being translated by multiple ribosomes, the mRNA and ribosomes together are said to form a polyribosome. Illustration shows mRNAs being transcribed off of genes. Ribosomes attach to the mRNAs before transcription is done and begin making protein. Image modified from "Prokaryotic transcription: Figure 3, by OpenStax College, Biology, CC BY 4.0. Why can transcription and translation happen simultaneously for an mRNA in bacteria? One reason is that these processes occur in the same 5' to 3' direction. That means one can follow or "chase" another that's still occurring. Also, in bacteria, there are no internal membrane compartments to separate transcription from translation. The picture is different in the cells of humans and other eukaryotes. That's because transcription happens in the nucleus of human cells, while translation happens in the cytosol. Also, in eukaryotes, RNA molecules need to go through special processing steps before translation. That means translation can't start until transcription and RNA processing are fully finished. You can learn more about these steps in the transcription and RNA processing video.

Define: metabolism, metabolic pathways, catabolism, anabolism, energy, kinetic energy, thermal energy, potential energy, chemical energy

Kinetic energy is the energy associated with objects in motion. Potential energy is the type of energy associated with an object's potential to do work. Chemical energy is the type of energy released from the breakdown of chemical bonds and can be harnessed for metabolic processes. metabolism: the complete set of chemical reactions that occur in living cells bioenergetics: the study of the energy transformations that take place in living organisms energy: the capacity to do work Anabolism (building molecules) Catabolism (breaking down molecules)

Know the general organization of the plasma membrane.

Like all other cellular membranes, the plasma membrane consists of both lipids and proteins. The fundamental structure of the membrane is the phospholipid bilayer, which forms a stable barrier between two aqueous compartments. In the case of the plasma membrane, these compartments are the inside and the outside of the cell. Proteins embedded within the phospholipid bilayer carry out the specific functions of the plasma membrane, including selective transport of molecules and cell-cell recognition.

Be able to list similarities and differences between mitosis and meiosis

Meiosis has two rounds of genetic separation and cellular division while mitosis only has one of each. In meiosis homologous chromosomes separate leading to daughter cells that are not genetically identical. In mitosis the daughter cells are identical to the parent as well as to each other.

Know the main components of the cytoskeleton: microtubules (tubulin polymers), Microfilaments (different protein subunits), Microfilaments (the subunit is actin).

Microfilaments Microfilaments are fine, thread-like protein fibers, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin, which is the most abundant cellular protein. Microfilaments' association with the protein myosin is responsible for muscle contraction. Microfilaments can also carry out cellular movements including gliding, contraction, and cytokinesis. Microtubules Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein tubulin--these subunits are termed alpha and beta. Microtubules act as a scaffold to determine cell shape, and provide a set of "tracks" for cell organelles and vesicles to move on. Microtubules also form the spindle fibers for separating chromosomes during mitosis. When arranged in geometric patterns inside flagella and cilia, they are used for locomotion. Intermediate Filaments Intermediate filaments are about 10 nm diameter and provide tensile strength for the cell.

monomer/basic units for each type of organic molecule and their general characteristics

Molecule Monomer carbohydrates-monosaccharides proteins-amino acids nucleic acids- nucleotides Lipids- Glyceral

the four types of organic molecules that make up all living cells

Nucleic Acids. Proteins. Carbohydrates. Lipids.

The scientific method follows a set of steps: What are those steps?

Observation, State the problem, Form a hypothesis, Experiment/design the experiment, Results/DataAnalysis

What are the seven characteristics that are used when "defining" the living world?

Order, Regulation, Growth, Adaption, Reproduction, Homeostasis, Energy Processing

What are the organelles found within the cell and what are their respective functions?

Organelle Function Factory partNucleusDNA StorageRoom where the blueprints are keptMitochondrionEnergy productionPowerplantSmooth Endoplasmic Reticulum (SER)Lipid production; DetoxificationAccessory production - makes decorations for the toy, etc.Rough Endoplasmic Reticulum (RER)Protein production; in particular for export out of the cell Primary production line - makes the toys Golgi apparatus Protein modification and export Shipping department PeroxisomeLipid Destruction; contains oxidative enzymesSecurity and waste removal LysosomeProtein destruction Recycling and security

There are different levels of organization in the living world: cells, organelles, organ system, Organisms, Populations, Communities, Ecosystems and Biosphere. Do you understand the difference(s) between these different levels? If yes, define them and list differences between them.

Organelles: (Example: nucleus), Cells, Tissue (Human Skin), Organs, Organ systems, Organism (Example: A pine tree), Population: (Example: Pine trees in a forest), Communities: (Example: All living things in a the same forest), Ecosystem: (Example: Includes the pine trees and say the soil) Biosphere: Encompasses all the ecosystems on earth

Know the difference between Oxidation and Reduction

Oxidation occurs when a reactant loses electrons during the reaction. Reduction occurs when a reactant gains electrons during the reaction. This often occurs when metals are reacted with acid.Oct 2, 2019

There are two types of transport proteins; give their name and explain how they are different. What is passive transport and what is active transport? What is diffusion? What is osmosis? Concentration gradient? Isotonic, hypertonic, hypotonic solutions?

Proteins which form channels may be utilized to enable the transport of water and other hydrophilic molecules; these channels are often gated to regulate transport rate.In facilitated transport, hydrophilic molecules bind to a "carrier" protein; this is a form of passive transport.In active transport, hydrophilic molecules also bind to a carrier protein, but energy is utilized to transport the molecules against their concentration gradient; in some cases, indirect energy sources are used. The ability of an extracellular solution to make water move into or out of a cell by osmosis is know as its tonicity. A solution's tonicity is related to its osmolarity, which is the total concentration of all solutes in the solution. A solution with low osmolarity has fewer solute particles per liter of solution, while a solution with high osmolarity has more solute particles per liter of solution. When solutions of different osmolarities are separated by a membrane permeable to water, but not to solute, water will move from the side with lower osmolarity to the side with higher osmolarity. Three terms—hypotonic, isotonic, and hypertonic—are used to compare the osmolarity of a cell to the osmolarity of the extracellular fluid around it. Note: When we use these terms, we are considering only solutes that cannot cross the membrane. If the extracellular fluid has lower osmolarity than the fluid inside the cell, it's said to be hypotonic—hypo means less than—to the cell, and the net flow of water will be into the cell. In the reverse case, if the extracellular fluid has a higher osmolarity than the cell's cytoplasm, it's said to be hypertonic—hyper means greater than—to the cell, and water will move out of the cell to the region of higher solute concentration. In an isotonic solution—iso means the same—the extracellular fluid has the same osmolarity as the cell, and there will be no net movement of water into or out of the cell.

What is the name of the enzyme responsible for transcription?

RNA polymerase Transcription involves synthesis of an mRNA molecule from the DNA template. The enzyme responsible is RNA polymerase. Translation requires an mRNA molecule, a supply of charged tRNAs (tRNA molecules with their associated amino acids), and ribosomes (composed of rRNA and ribosomal proteins).

What are valence electrons? What does it mean when we say that Carbon is "tetravalent"? how does that characteristic contribute to its importance in organic molecules

Tetra-valency of Carbon This basically means that carbon has four valence electrons (outer electrons that are available for forming bonds with other atoms). Because of this arrangement within the atom's orbits, carbon is called tetravalent.

What are cofactors? What are enzyme inhibitors? What is the difference between competitive and non-competitive inhibitors?

The competitive inhibitor binds to the active site and prevents the substrate from binding there. The noncompetitive inhibitor binds to a different site on the enzyme; it doesn't block substrate binding, but it causes other changes in the enzyme so that it can no longer catalyze the reaction efficiently.

Understand how polar and non-polar bonds relate to hydrophilic and hydrophobic substances

The final type of interaction occurs between neutral hydrophobic, or water-fearing, molecules. Because polar molecules are generally water soluble, they are referred to as being hydrophilic, or water-loving.

What are the five unifying themes in biology? Can you explain each one of them using your own words and with examples?

The five central themes of biology are structure and function of cells, interactions between organisms, homeostasis, reproduction and genetics, and evolution.

Why is the plasma membrane important for cellular function? List and explain different functions played by the plasma membrane proteins. List and explain different functions played by glycolipids and glycoproteins

The fluid mosaic model describes the plasma membrane structure as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates. The principal components of the plasma membrane are lipids ( phospholipids and cholesterol), proteins, and carbohydrates. The plasma membrane protects intracellular components from the extracellular environment. The plasma membrane mediates cellular processes by regulating the materials that enter and exit the cell. The plasma membrane carries markers that allow cells to recognize one another and can transmit signals to other cells via receptors. The plasma membrane is a fluid combination of phospholipids, cholesterol, and proteins. Carbohydrates attached to lipids (glycolipids) and to proteins (glycoproteins) extend from the outward-facing surface of the membrane. Carbohydrates are the third major component of plasma membranes. They are always found on the exterior surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids). These carbohydrate chains may consist of 2-60 monosaccharide units and can be either straight or branched. Along with peripheral proteins, carbohydrates form specialized sites on the cell surface that allow cells to recognize each other. This recognition function is very important to cells, as it allows the immune system to differentiate between body cells (called "self") and foreign cells or tissues (called "non-self"). Similar types of glycoproteins and glycolipids are found on the surfaces of viruses and may change frequently, preventing immune cells from recognizing and attacking them. These carbohydrates on the exterior surface of the cell—the carbohydrate components of both glycoproteins and glycolipids—are collectively referred to as the glycocalyx (meaning "sugar coating"). The glycocalyx is highly hydrophilic and attracts large amounts of water to the surface of the cell. This aids in the interaction of the cell with its watery environment and in the cell's ability to obtain substances dissolved in the water.

Describe how the mitotic spindle is formed and what is made of.

The mitotic spindle begins to form. The spindle is a structure made of microtubules, strong fibers that are part of the cell's "skeleton." Its job is to organize the chromosomes and move them around during mitosis. The spindle grows between the centrosomes as they move apart.

What is selective permeability? Which molecules can freely cross the plasma membrane, and which can't?

The plasma membrane is selectively permeable; hydrophobic molecules and small polar molecules can diffuse through the lipid layer, but ions and large polar molecules cannot. Integral membrane proteins enable ions and large polar molecules to pass through the membrane by passive or active transport.

RNA processing: What kind of modifications are applied to the pre-mRNA molecules? What are the roles of these modifications?

The pre-mRNA has to go through some modifications to become a mature mRNA molecule that can leave the nucleus and be translated. These include splicing, capping, and addition of a poly-A tail, all of which can potentially be regulated - sped up, slowed down, or altered to result in a different product.

How does the organization of the water molecule lead to the different properties of water? Some key words to think of: covalent polar bond; partial charges; hydrogen bonding

Water owes these unique properties to the polarity of its molecules and, specifically, to their ability to form hydrogen bonds with each other and with other molecules. Water as a Solvent The polarity of the water molecule make water a great solvent. Ionic compounds can be dissolved in water because of the negative charge of the oxygen atom and the positive charge of the hydrogen atoms. The water molecules surround the oppositely charged ions as a result of attraction to their polar charges. The water molecules create a hydration shell that separates the ions and the compound is dissolved. There are other nonionic polar molecules that can be dissolved in water. Water, as a solvent, is the essential substance in nearly all life functions. 4. The Moderation of Temperature by Water A brief explanation of kinetic energy is important to the topic of moderation of temperature. Kinetic energy is the energy of motion. In a body of water the molecules of water are always moving. This movement of the molecules is kinetic

List all the phases of the cell cycle and explain what's happening at each phase to the centrosomes, chromosomes, nuclear envelope, mitotic spindle and the rest of the apparatus involved in cell division

anaphase: the stage of mitosis during which sister chromatids are separated from each other cell cycle: the ordered sequence of events that a cell passes through between one cell division and the next cell cycle checkpoints: mechanisms that monitor the preparedness of a eukaryotic cell to advance through the various cell cycle stages cell plate: a structure formed during plant-cell cytokinesis by Golgi vesicles fusing at the metaphase plate; will ultimately lead to formation of a cell wall to separate the two daughter cells centriole: a paired rod-like structure constructed of microtubules at the center of each animal cell centrosome cleavage furrow: a constriction formed by the actin ring during animal-cell cytokinesis that leads to cytoplasmic division cytokinesis: the division of the cytoplasm following mitosis to form two daughter cells G0 phase: a cell-cycle phase distinct from the G1 phase of interphase; a cell in G0 is not preparing to divide G1 phase: (also, first gap) a cell-cycle phase; first phase of interphase centered on cell growth during mitosis G2 phase: (also, second gap) a cell-cycle phase; third phase of interphase where the cell undergoes the final preparations for mitosis interphase: the period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases; the interim between two consecutive cell divisions kinetochore: a protein structure in the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase metaphase plate: the equatorial plane midway between two poles of a cell where the chromosomes align during metaphase metaphase: the stage of mitosis during which chromosomes are lined up at the metaphase plate mitosis: the period of the cell cycle at which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase mitotic phase: the period of the cell cycle when duplicated chromosomes are distributed into two nuclei and the cytoplasmic contents are divided; includes mitosis and cytokinesis mitotic spindle: the microtubule apparatus that orchestrates the movement of chromosomes during mitosis prometaphase: the stage of mitosis during which mitotic spindle fibers attach to kinetochores prophase: the stage of mitosis during which chromosomes condense and the mitotic spindle begins to form quiescent: describes a cell that is performing normal cell functions and has not initiated preparations for cell division S phase: the second, or synthesis phase, of interphase during which DNA replication occurs telophase: the stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by new nuclear envelopes

How is the genetic material organized in chromosomes before, during and after cell division? How are chromosomes distributed during eukaryotic cell division?

ng interphase (1), chromatin is in its least condensed state and appears loosely distributed throughout the nucleus. Chromatin condensation begins during prophase (2) and chromosomes become visible. Chromosomes remain condensed throughout the various stages of mitosis (2-5).

What are the molecular components involved in Translation? Explain the overall role and structure of each one of them. Be thorough.

nucleotides - the building blocks of DNA and RNA molecules that contain the cell's genetic code. Adenosine, cytidine, guanosine, thymidine, and uridine are all nucleotides. polypeptide chain - the long chain of amino acids that is created during translation.

What is a messenger RNA? What is a primary transcript?

primary transcript is the single-stranded ribonucleic acid (RNA) product synthesized by transcription of DNA, and processed to yield various mature RNA products such as mRNAs, tRNAs, and rRNAs. The primary transcripts designated to be mRNAs are modified in preparation for translation.