Ch 1 - 6 Flashcards

Question

When Griffith injected heat-killed infectious bacteria mixed with live harmless bacteria, he found that the mice died because a) the live harmless bacteria were transformed into infectious bacteria b) the heat-killed infectious bacteria were ablet o kill the mice on their own c) the live harmless bacteria were able to kill the mice on their own d) the heat-killed infectious bacteria were not actually dead

Answer 1

a) the live harmless bacteria were transformed into infectious bacteria Griffith found that heat-killed infectious bacteria alone or live harmless bacteria on their own were NOT able to infect and kill the mice. However, when he mixed the two together, the mice died and an infectious strain of bacteria was found in the blood of the mice. This experiment provided the first strong evidence that genes are made of DNA.

Answer 2

d) phosphodiester bond DNA is a long polymer of nucleotides held together by phosphodiester bonds. This forms a single strand of DNA. The two strands of DNA are held together by hydrogen bonds between the nucleotide bases.

Answer 3

b) base pairing of pyrimidines with purines DNA is made of up two strands where purines bases (2 carbon rings) pair with pyrimidines (1 carbon ring). If purines and purines base-paired, or pyrimidines and pyrimidines base-paired, the helix would be wider or narrower (respectively) along its length due to the different sizes of the base combinations.

Answer 4

d) hydroxyl The hydroxyl group and the phosphate group of neighboring nucleotides bond together during DNA polymerization, which leads to a polarity of the DNA strand. One end has a phosphate group, the other end has an unbound hydroxyl group.

Answer 5

d) the order of nucleotide bases The linear sequence of the nucleotide bases in the DNA molecule is what contains the information for making proteins. This is decoded by other molecules that translate this information to link specific amino acids into proteins.

Answer 6

c) complementary base pairing The complementary base pairing of A with T and G with C suggests that one strand could be used to make a new copy of the other strand. Although the other answers are features of DNA, they do not directly produce a way for the molecule to be copied.

Answer 7

c) telomeres Prokaryotic DNA has the same chemical structure as eukaryotic DNA and is packaged by proteins to fit in the cell. Prokaryotes, however, usually have a single circular chromosome, and therefore no telomeres, which are the specialized sequences at the ends of linear chromosomes.

Answer 8

a) karyotype Scientists can stain chromosomes from a human tissue sample in order to identify all the chromosomes. Identification is done from the staining pattern or by using chromosome sequence-specific fluorescent dyes and can be helpful in identifying abnormalities in the size, number, or sequence rearrangement of chromosomes.

Answer 9

c) 22 pairs of autosomes + 1 X chromsome + 1 Y chromosome Humans typically have 46 chromosomes, 22 pairs of autosomes, and two sex chromosomes. Biological females have a pair of X chromosomes, and biological males have an X chromosome and a Y chromosome.

Answer 10

c) a gene A gene is a segment of DNA that has the instructions for making an RNA or protein. The genome is the total amount of genetic information carried in the complete set of chromosomes in an organism.

Answer 11

c) more complex organisms generally have larger genomes but there are many notable exceptions. More complex organisms have more functions requiring specialized proteins and RNA and thus generally have more genes and larger genomes. However, there are many exceptions to this rule, as many plants and a particular amoeba have much larger genomes than humans.

Answer 12

d) portions of junk sequences are conserved between species and thus may be functional Junk DNA is just a name given to portions of DNA for which the function is currently unknown. Some of these sequences have sequence similarity between species, suggesting they are conserved through evolution and thus may have unique functions.

Answer 13

d) centromeres Centromeres are a sequence of DNA upon which specialized structures are formed to allow the mitotic spindle machinery to attach to each sister chromatid of a duplicated chromosome.

Answer 14

c) to assemble ribosomal RNA and proteins into ribosomes The nucleolus is an organization of chromosomal regions that contain genes for ribosomal RNAs. It is a structure large enough to be seen in the light microscope in the interphase nucleus. These RNAs are transcribed in the nucleolus and are assembled with ribosomal proteins to make ribosomes.

Answer 15

a) during mitosis During mitosis, the chromatin structure that packages chromosomes gets even more compact than usual. This is to compress the chromosomes into discrete bodies that are easier to separate and organize.

Answer 16

B Approximately 147 bp DNA is wrapped around a core of eight histone proteins to form a "nucleosome core particle." This is the basic unit of chromatin. The nucleosome is the core particle plus the ~200 bp of linker DNA between core particles.

Answer 17

c) electrostatic interactions Histone proteins are highly positively charged due to their composition from a large number of basic amino acids. This allows them to interact with the negatively charged DNA backbone.

Answer 18

c) it can have different effects depending on the location The addition of methyl groups to modify histone tails can have various effects on the chromatin structure, depending on the histone protein modified and location in the protein. Most importantly, these histone modifications serve as docking sites to recruit different regulatory proteins and do not have a direct effect on the chromatin themselves. Histone-modifying enzymes work in concert with the chromatin-remodeling complexes to condense and relax stretches of chromatin, allowing local chromatin structure to change rapidly according to the needs of the cell.

Answer 19

protein machines that use the energy of ATP hydrolysis to change the position of the DNA wrapped around nucleosomes, rendering the DNA more accessible (or less accessible) to other proteins in the cell. During mitosis, many of the complexes are inactivated, which may help mitotic chromosomes maintain their tightly packed structure.

Answer 20

B) euchromatin Heterochromatin tends to be relatively gene-poor, whereas euchromatin is relatively gene-rich. This is because heterochromatin is so compact that the gene expression machinery cannot access the DNA in chromatin for transcription. The most striking example of the use of heterochromatin to keep genes silences is found in the interphase X chromosomes of female mammals.

Answer 21

a) barrier DNA sequence Heterochromatin spreading can occur when histone-modifying complexes bind to the mark they catalyze and establish the modification in neighboring histones. The modifications that direct the formation of the most common type of heterochromatin include the methylation of lysine 9 in the tail of histone H3. A wave of condensed chromatin propagate along the chromosome until it encounters a barrier sequence. Barrier sequences function to block neighboring histones from the modification activity and stop the spread of heterochromatin.

Answer 22

b) the active genes can become silenced Due to its compact nature, genes in heterochromatin are often inactive because they are not accessible. Heterochromatin can sometimes accidentally spread into regions where it is not meant to and cause silencing of genes in that region. Such inappropriate packaging of genes in heterochromatin can cause diseases like anemia.

Answer 23

c) hydrogen bonds The backbone of the polypeptide consists of uncharged polar covalent bonds. Because the bonds in the backbone are neither charged nor hydrophobic (i.e. nonpolar), hydrophobic forces and electrostatic interactions do not involve the backbone. Hydrogen bonds, however, are formed between atoms in the polar covalent bonds found in both amino acid side chains and in the carboxyl group and amino groups of the polypeptide backbone.

Answer 24

d) 1 Free energy is designated by the letter G. If the free-energy value decreases during protein folding, the reaction is energetically favorable. Proteins generally fold along the most energetically favorable pathway, so the conformation with the lowest free-energy (G) value, 1, is the correct answer.

Answer 25

b) certain proteins easily aggregate with other proteins All proteins can fold on their own without assistance due to the energetically favorable interactions between amino acid side chains and/or the polypeptide backbone. However, the cytoplasm is crowded and some proteins can form favorable interactions with other proteins before they have a chance to fold. These aggregates could impede proper folding.

Answer 26

d) a-helix The hydrogen bonds that form a β-pleated sheet structure occur between the N–H and C=O groups of amino acids in different segments of a single polypeptide chain lying side by side. Amyloid structures are β sheets that interlock with each other through their side chains. The α helices are formed by hydrogen bonds between every fourth amino acid in the primary structure.

Answer 27

c) they consist of stacked b-sheets Amyloid protein structures are β sheets that interlock with each other through their side chains and form stacks. Since they are made from many β sheets, they form strong structures that have many roles in the cell, including the formation of important cellular compartments. However, some amyloid structures, but not all, are abnormal and cause disease. one good role is that amyloid structures make some of the interiors of intracellular condensates. The stacked beta-sheets come together to produce a "hydrogel" that pulls other molecules into the condensate.

Answer 28

a) domain A domain is a sequence of amino acids in a polypeptide chain that adopts a defined folding pattern based on the interactions of the side chains, as well as contributions from the polypeptide backbone molecules. This is distinct from a subunit, which is a term used for a single, complete polypeptide chain that can interact with other subunits to form a larger complex.

Answer 29

d) quaternary The primary structure is the linear order of amino acids in a polypeptide chain. The secondary structure is the formation of organized arrangements to form segments like α helices and β sheets. The tertiary structure is the overall three-dimensional shape of a protein. The quaternary structure is the assembly of multiple folded polypeptide chains into a larger complex.

Answer 30

b) domain \< subunit \< complex A domain is a portion of an amino acid sequence that folds into a three-dimensional structure and is the smallest of the organizational units. A subunit is a single, complete polypeptide chain and may be made up of one or more domains. Two or more subunits can assemble into a complex.

Answer 31

a) many weak noncovalent interactions Covalent interactions are rarely used between protein molecules because they are difficult to break, often requiring an enzyme. Interactions between proteins and their partners need to be reversible but very specific. A specific interaction, but one that is able to be altered, can be achieved through the formation of many weak noncovalent interactions between proteins and their binding partners.

Answer 32

a) covalent bonds between cysteines Using mechanisms such as noncovalent bonds between charged side chains, proteins fold into their final conformation based on their amino acid sequence inside the cell. However, in the harsh environment outside the cell, this structure needs to be stabilized to keep its final form and function. Disulfide bonds are covalent cross-linkages between cysteine groups juxtaposed in the three-dimensional structure, and they act to hold the shape of the protein.

Answer 33

A Unique antigen-binding sites in antibodies are formed by varying the terminal amino acid sequences in the heavy chain and the light chain, which come together into a unique three-dimensional conformation for specific side-chain interactions with the antigen. Since each antibody is made up of two heavy chains and two light chains, there are two antigen-binding sites per antibody.

Answer 34

b) the binding strength of enzyme to substrate Enzyme activity is measured using two values. The first is the rate at which the enzyme converts the substrate to the product, which is called **Vmax**. This value is determined by measuring the rate of product formation in conditions where all enzyme binding sites are occupied by a substrate. The **Michaelis constant** measures the relative binding strength of the enzyme to a substrate, determined by the concentration of substrate at which the enzyme operates at half of its Vmax.

Answer 35

d) enzymes reduce the free energy of the products of the reaction Enzymes lower the activation energy of a reaction by promoting changes in the substrate that will encourage the reaction to occur. This can include changes in shape, alignment of two substrates, or changes in the electron density to encourage bond breakage and formation. Enzymes do not change the overall free energy of the reaction.

Answer 36

a) turn off the synthesis of a product when it is in abundance Feedback inhibition keeps the cell from accumulating unnecessarily large amounts of biological compounds by reversibly inhibiting an enzyme in the biosynthetic pathway for that compound. These mechanisms shut down the enzymes early in the pathway so that wasteful intermediates do not accumulate.

Answer 37

b) inducing a conformational change Once a regulatory molecule or ligand binds to a regulatory site, an allosteric protein undergoes a conformational change that is transmitted to the active site. Inducing the conformational change can change the activity of the enzyme, but it does NOT directly block the active site.

Answer 38

d) could increase or decrease activity Phosphorylation of amino acid side chains in a protein changes their charge to a negative charge. It could lead to changes in the conformation of the protein, differences in binding to partners, and either increased or decreased activity of an enzyme. Thus, the effects of protein phosphorylation are particular to the protein itself.

Answer 39

a) always activates the protein ## Footnote Proteins in the GTP-binding protein family are always in their active conformation when GTP is bound, in contrast to phosphorylation of a protein, which can activate or inactivate a protein. The hydrolysis of GTP to GDP returns the protein to the inactive state.

Answer 40

c) side chains The chemical modification of phosphorylation and acetylation occurs on the side chain of the amino acid and can affect how proteins interact with other proteins or components of the cell. This effect can occur through the direct alteration of binding sites if the phosphorylation and acetylation occur on an amino acid in a binding site, or through a conformational change that indirectly alters the binding site.

Answer 41

a) the hydrolysis of ATP to ADP caused a conformational change in the protein (A) is the state where no ATP or ADP is bound. The protein is bound to the filament with one of its two filament-binding domains, while the other binding domain is unbound. (B) shows that upon ATP binding, a conformational change moves the unbound domain forward one step to interact with the filament. In (C), ATP is hydrolyzed to ADP, creating a conformational change to release the rear filament-binding domain and bring it forward.

Answer 42

b) high concentrations of interacting proteins and RNA Biochemical subcompartments can form inside of organelles by the aggregation of interacting proteins, RNA, and protein complexes that perform a concerted function. These "intracellular condensates" are simply concentrations of molecules; they are not bound by a membrane, nor are they hydrophobic droplets.

Answer 43

c) affinity chromatography Affinity chromatography separates proteins from one another by using a known molecular interaction with the protein of interest. Gel electrophoresis and mass spectrometry separate protein fragments by size and charge. X-ray crystallography is a method for determining the three-dimensional structure of a protein; it is not used for separation.

Answer 44

d) cryoelectron microscopy Large proteins produce confounding signals on NMR spectra, and large integral membrane complexes are hard to crystallize for x-ray crystallography. Structural studies of large integral membrane protein complex could be performed with cryoelectron microscopy. In this method, the purified protein complex is embedded in ice and a beam of electrons is used to collect projected images in multiple orientations.

Answer 45

c) a structurally related group of proteins A protein family is a set of proteins that have similar primary structures (amino acid sequences) and thus have related three-dimensional structures. If the structure of one member of a protein family is determined, it can be used to make predictions about the structure of other members of the protein family.

Answer 46

a) alpha helix b) both alpha-helix and beta-sheet c) alpha helix d) beta-sheet e) beta-sheet f) alpha-helix and beta-sheet

Answer 47

d) anabolic; catabolic Metabolism is the sum total reactions in a cell, which are of two types. Catabolic reactions are the reactions where cells break down the large molecules in foodstuffs into their constituent building blocks. Anabolic reactions are biosynthetic—they build larger molecules from smaller building blocks.

Answer 48

b) heat Even though living systems produce ordered structures from smaller building blocks, this does not violate the second law of thermodynamics because they still create disorder by releasing energy in the form of heat. Heat is energy in its most disordered form.

Answer 49

d) because photosynthetic organisms produce food molecules using light energy Organic molecules for energy are obtained by animals through their diet, by consuming either plants or animals that eat plants. Plants produce organic molecules using energy from the sun, thus the source of energy from food molecules in plants is ultimately from the sun.

Answer 50

d) produces; water + carbon dioxide; consumes; oxygen + sugars Cellular respiration is the process by which cells break down food molecules for energy, producing water and carbon dioxide as waste products. Photosynthesis uses energy from the sun to make food molecules (sugars) and oxygen.

Answer 51

c) reduction The gain of electrons by a molecule is called reduction; the loss of electrons is called oxidation.

Answer 52

b) because it is the most stable form of carbon in our atmosphere Cellular respiration is the breakdown of carbon-containing molecules through oxidation to release energy. Because the most energetically stable form of carbon in the presence of oxygen is carbon dioxide, this is the final end product of respiration.

Answer 53

c) increase in entropy Reactions that are energetically favorable increase the entropy (or disorder) of the universe. This can be through either the release of free energy in different forms, or the release of energy as heat (energy in its most disordered form).

Answer 54

a) lower the activation energy needed to start the reaction ## Footnote Enzymes work by lowering the threshold energy input, called the activation energy, needed to start a reaction.

Answer 55

b) not energetically favorable ## Footnote Reactions that have products with LESS free energy than the reactants will release free energy and create more disorder in the system. These will proceed spontaneously and are energetically favorable. However, when products of a reaction have MORE free energy than the reactants, there is no release of energy, and the reaction is not energetically favorable.

Answer 56

c) zero When equilibrium is reached, the forward and reverse reactions are equal, so there is no net change in the number of reactants and products. The reaction does not proceed forward or backward at this point and ΔG is equal to zero.

Answer 57

c) ΔG⁰ is the free-energy change at standard temperature and concentrations ## Footnote The value of the free-energy change of a reaction, ΔG, is dependent upon the concentration of reactants and products, as well as the temperature of the system. ΔG⁰ is the standard free-energy change at standard temperature and concentrations to allow comparison of different reactions.

Answer 58

d) The amount of product will be higher than the amount of substrate at equilibrium If the equilibrium constant, K, is very high, it means that there is far more of the product X than substrate Y at equilibrium (i.e., when forward and reverse reaction rates are balanced). This corresponds to a free-energy change that is large and negative.

Answer 59

d) Forward reaction A would increase Enzymes lower the activation energy for reactions and thus increase the probability that the energy barrier can be surpassed for the reaction to proceed. They do not change the equilibrium point (the relative levels of reactants and product at equilibrium).

Answer 60

a) they capture energy from energy-releasing reactions and transfer it to other reactions. ## Footnote Activated carriers collect electrons from the oxidation of molecules in catabolic reactions and transfer them to anabolic reactions that require electrons for the reduction of molecules.

Answer 61

b) The removal of the phosphate is energetically favorable ## Footnote The products of the ATP hydrolysis reaction—ADP and free phosphate—are more stable and have a lower free energy. Release of free phosphate is energetically favorable because it relieves the repulsion of the negative charges of the neighboring phosphate groups and the aqueous environment to make hydrogen bonds with the phosphate.

Answer 62

c) a phosphate is first transferred to reactant A–OH to form a high energy intermediate. ## Footnote ATP powers the formation of energetically unfavorable bonds between two molecules by first breaking its own high-energy phosphoanhydride bond and transferring the phosphate to another molecule. This new phosphate linkage can then be broken to power the bond formation between molecules.

Answer 63

d) donating electrons for a reduction reaction NADPH is an activated carrier of electrons that participates in oxidation-reduction reactions. NADPH is produced in reactions in which 2 electrons are removed from a substrate. The oxidized form of the carrier molecule (NADP+) receives these two electrons as a hydrogen atom plus an electron (a hydride ion). NADPH holds its hydride ion in a high-energy linkage; this ion can easily be transferred to other molecules.

Answer 64

d) the oxidized form of NADPH is more stable than the reduced form NADPH carries two high-energy electrons (holds the hydride ion in a high-energy linkage). Losing these electrons in an oxidation reaction is energetically favorable because the oxidized form, NADP+, is more stable than the reduced form (NADPH).

Answer 65

d) NAD+ Cells maintain high concentrations of NAD+ so that it is readily available to accept electrons from the oxidation of food molecules in catabolic reactions. NADPH operates chiefly with enzymes that catalyze anabolic reactions. NADH has a special role as an intermediate in the catabolic reactions that generate ATP through the oxidation of food molecules. Inside the cell, the ratio of NAD+ and NADH is kept high, whereas the ratio of NADP+ and NADPH is kept low. This allows plenty of NAD+ to act as an oxidizing agent and plenty of NADPH to act as a reducing agent.

Answer 66

a) unfavorable; favorable ## Footnote Condensation reactions reduce the disorder in the universe and are energetically unfavorable. Hydrolysis reactions increase the disorder in the universe and are energetically favorable.

Answer 67

a) between carbon-based molecules ## Footnote The chemistry of living things follows all the same chemical and physical laws of the chemistry that occurs in the nonliving world. The difference is that the chemical compounds of life are mostly carbon-based polymers that undergo complex reactions in an aqueous environment.

Answer 68

a) salt ## Footnote Atoms are the simplest form of an element that still retain the properties of that element. When multiple atoms come together, it is called a molecule, but when those bonds are solely ionic bonds, it is often called a salt.

Answer 69

8 The atomic number is the number of protons in the nucleus of an atom. For an atom to remain electrically neutral, the number of electrons is equal to the number of protons. Thus oxygen, with an atomic number of 8, has 8 electrons.

Answer 70

18 Glucose has a molecular weight of 180 g/mole, which means that dissolving this mass of glucose in a liter would give a 1 M solution. Because 100 mM is 0.1 M, it is 1/10 of the concentration. Using 1/10 of the molecular weight (18 g) in the same volume would give a 1/10 concentration, thus a 0.1 M or 100 mM solution.

Answer 71

4 Carbon has four electrons in its outer shell and it needs eight to fill it. To fill its outer shell, carbon can share electrons with four different atoms, forming four bonds.

Answer 72

b) be highly soluble in water ## Footnote Polar covalent bonds are formed when two atoms unequally share an electron, forming partial positive and partial negative charges at either end of the bond. Water also has partial positive and negative charges, and thus will easily interact with other molecules’ partial charges, thus making it soluble.

Answer 73

accept Bases accept protons in water, removing a proton from a water molecule. If the hydrogen atoms in water are more attracted to the electronegative atom of a base, they can be stripped off as a proton.

Answer 74

d) weaker; less Ionic bonds are weak bonds commonly found in salts that form ions in aqueous solution. Because the cell environment is primarily aqueous, ionic bonds are dissociated by interaction with water.

Answer 75

d) methyl groups (–CH₃) Bonds between carbon and hydrogen are nonpolar and molecules with mostly nonpolar bonds are hydrophobic. Bonds between H and electronegative atoms like O and N are polar and tend to impart hydrophilic characteristics.

Answer 76

a) both directions ## Footnote To form cell membranes, phospholipids form a bilayer, with the fatty acid tails facing each other. Thus, one layer has the fatty acid tails facing inward and the other layer has the fatty acid tails facing outward.

Answer 77

Unsaturated fatty acids have double bonds in their hydrocarbon chains, and so have kinks in them; these keep them further apart. Thus, membranes made from unsaturated fatty acids are more fluid because they cannot pack as closely together as saturated fatty acids, which have no double bonds and are straighter.

Answer 78

b) phosphate group(s) ## Footnote A nucleotide is a sugar (either ribose or deoxyribose), attached to a nitrogen-containing base, and one or more phosphate groups. A nucleoside simply lacks any phosphate groups.

Answer 79

RNA uses the sugar ribose, which has a 2′ and a 3′ −OH, whereas DNA uses the sugar deoxyribose, which only has a 2′ −OH. This leads to fundamental differences in the self-replication and stability of these molecules.

Answer 80

d) ultracentrifugation Scientists at first did not believe that molecules could be as large as hemoglobin, and thought they were a lot of smaller molecules held together in close association. Separating molecules by size in ultracentrifugation allowed scientists to see if macromolecules were just one molecule of a large size, or many small molecules.

Answer 81

b) share the same basic chemistry

Answer 82

d) proteins

Answer 83

a) scanning electron microscopy ## Footnote Of all the microscopy techniques listed, electron microscopy provides the most high-resolution and detailed images. Scanning electron microscopy examines the outer surface of cell structures and gives a 3-D image.

Answer 84

b) fluorescence microscopy Light microscopy, which also includes fluorescence microscopy, can be used to view living cells. Electron microscopy requires cell fixation and extensive preparation of the samples, which kills the cells.

Answer 85

d) their DNA sequences Archaea and bacteria are similar in size and cell appearance under a microscope, but they differ significantly in their genome sequences. Because they are both prokaryotes, they lack a nucleus and any organelles.

Answer 86

a) house the DNA in a separate cell compartment ## Footnote DNA, in the form of chromosomes, is stored in the nucleus. Keeping the DNA separate from other cell components helps eukaryotic cells regulate access to genetic information.

Answer 87

a) folded; a large surface area for staging energy production processes ## Footnote In mitochondria, the outer membrane is smooth, while the inner membrane is highly folded and convoluted. The proteins that are responsible for energy production via respiration are found in the inner membrane.

Answer 88

d) peroxisomes contain hydrogen peroxide Both peroxisomes and lysosomes are small organelles that break down materials, but lysosomes generally digest biomolecules like proteins so that the building blocks can be reused. Peroxisomes deactivate toxic materials, often using hydrogen peroxide.

Answer 89

microtubules – chromosome segregation intermediate filaments – strength support actin filaments – cell movement Microtubules form the mitotic spindle that functions in the accurate chromosome segregation, intermediate filaments have a primary function of providing strength and support to the cell, and actin filaments are involved in dynamic processes such as cell motility.

Answer 90

b) microtubules form tracks for movement of cell components ## Footnote While plant cells are immobile, actin filaments and microtubules still play a major role in the movement of organelles and cell components within the cell. Intermediate filaments are not found in the cytoplasm of plant cells.

Answer 91

DNA Replication The rules behind the process of DNA replication (as well as transcription and translation) were determined by experiments with the bacterial model organism E. coli. These simple prokaryotes are single-celled and do not have a cell cycle or mitosis, thus are best for studies of the most evolutionarily conserved cell processes.

Answer 92

b) many of the genes involved in the development of the fruit fly are also found in humans ## Footnote Fruit flies have been studied for over a century, and their complex body plan can be manipulated genetically to uncover which genes govern the development of which parts. Many of these genes have direct counterparts in the human genome.

Answer 93

b) plants have more genes that were duplicated during evolution ## Footnote Plants have genes that were duplicated during evolution, and thus their protein-coding gene number is higher. Repeated noncoding sequences cannot explain this observation, since these do not get counted in the number of protein-coding genes.

Answer 94

They they evolved from a common ancestral gene

Answer 95

a) can be used to regulate gene activity ## Footnote The genome of a complex organism is made up of protein-coding genes, sequences that encode functional RNAs, and regulatory sequences used to finely tune gene activity. Other DNA noncoding sequences seem to be unimportant to the cell, but we might just not understand their function yet.

Answer 96

A free-living, nonphotosynthetic, single-celled, motile eukaryote

Answer 97

Activated carrier that donates the carbon atoms in its readily transferable acetyl group to many metabolic reactions, including the citric acid cycle and fatty acid biosynthesis; the acetyl group is linked to coenzyme A (CoA) by a thioester bond that releases a large amount of energy when hydrolyzed.

Answer 98

The maximum rate of an enzymatic reaction, reached when the active sites of all of the enzyme molecules in a sample are fully occupied by substrates

Answer 99

The maximum number of substrate molecules that an enzyme can convert into product per second.

Answer 100

The concentration of substrate at which an enzyme works at half its maximum velocity; serves as a measure of how tightly the substrate is bound.

Answer 101

Protein with multiple binding sites for other macromolecules, holding them in a way that speeds up their functional interactions.