Bio 213 (Chapter 4, 8 and 9)

Which of the following statements about DNA and RNA are TRUE? -DNA is polymer of nucleotides, whereas RNA is a polymer of nucleotides. -DNA usually has two polynucleotide strands, whereas RNA usually has one strand. -DNA has deoxyribose sugar, whereas RNA has ribose sugar.

Answer: DNA usually has two polynucleotide strands, whereas RNA usually has one strand. AND -DNA has deoxyribose sugar, whereas RNA has ribose sugar.

What would happen to the value of **delta** G for the reaction in which phosphoenolpyruvate is converted to pyruvate (**delta** G= -23 kJ/mol) when it reaches equilibrium? -**Delta** G would become more negative -**Delta** G would equal 0 -**Delta** G would become positive -**Delta** G would depend on the activity of its enzyme pyruvate kinase.

Answer: -**Delta** G would equal 0

How many CO2 molecules are released per glucose during the citric acid cycle? -2 -3 -4 -5 -6

Answer: -4

Which of the following is FALSE? -ATP is an inhibitor of phosphofructokinase -Citrate activates fatty acid synthase -ADP and NAD+ are inhibitors of isocitrate dehydrogenase -ATP synthase can also act as an ATPase -The F1 unit of ATP synthase rotates to expose active sites for ATP synthesis.

Answer: -ADP and NAD+ are inhibitors of isocitrate dehydrogenase

Why does the electron transport chain have so many steps? Why not use one step as indicated below 2 NADH + 2 H+ + O2 ---> 2 NAD+ + 2H20 -The above reaction is extremely exergonic -Too much energy would be released at once and the cell cannot harvest such energy. -Using many steps will be advantageous because each step will release only a small amount of energy that can be captured by an endergonic reaction -ALL ARE TRUE

Answer: -ALL ARE TRUE

**Bonus** Rotenone is a potent inhibitor of mitochondrial complex I. If you were to treat isolated mitochondria with rotenone, what would you expect to happen to ATP production by oxidative phosphorylation? -ATP production would decrease and electron transport would increase -ATP production would increase and electron transport would decrease -ATP production and electron transport would decrease -ATP production and electron would increase -ATP production would become uncoupled from electron transport

Answer: -ATP production and electron transport would decrease

What is the correct order in which the following molecules would be produced if phosphate ions were removed from ATP one at a time? -ATP, ADP, AMP, adenosine -AMP, ADP, ATP, adenosine -Adenosine, AMP, ADP, and ATP -ATP, AMP, ADP, adenosine

Answer: -ATP, ADP, AMP, adenosine

All of the following statements about energy transformations are true EXCEPT ________ -Entropy (S) is a measure of the disorder in a system. -According to the first law of thermodynamics, when energy is converted from one form to another, the total energy is always more before the conversion than after the conversion. -According to the second law of thermodynamics, when energy is converted from one form to another, some energy is unavailable to do work. -Potential energy is stored energy and can be converted

Answer: -According to the first law of thermodynamics, when energy is converted from one form to another, the total energy is always more before the conversion than after the conversion.

How do enzymes catalyze reactions? -By adding chemical groups to the substrates -by adding charges to the substrates -by orientating the substrates -by inducing strain in the substrates -All ARE TRUE

Answer: -All ARE TRUE

During Jogging....? -Glucose is catabolized to produce energy for leg muscles. -Glucose is made in the liver by anabolism from amino acids and pyruvate -Glycogen in leg muscles and liver is hydrolyzed to produce glucose for energy -Glucose is catabolized to produce energy for heart muscle -All are true

Answer: -All are true

Which of the following is true? -Alcoholic fermentation requires only one enzyme to metabolize pyruvate to ethanol. -Alcohol dehydrogenase catalyzes the conversion of pyruvate to lactate. -Lactate formation occurs in muscle cells only when oxygen levels are high. -Both alcoholic fermentation and lactic acid fermentation regenerate NADD+ which keeps glycolysis going. -Both alcoholic fermentation and lactic acid fermentation produce CO2.

Answer: -Both alcoholic fermentation and lactic acid fermentation regenerate NADD+ which keeps glycolysis going.

Retroviruses such as HIV , have an enzyme that allows them to catalyze DNA synthesis from an RNA template. This evidence supports the hypothesis that....? -RNA itself cannot be a catalyst -Early life consisted of an 'RNA'' world -RNA probably came from an extraterrestrial source. -chemical evolution led to polymerization -DNA polymers from RNA monomers.

Answer: -Early life consisted of an 'RNA'' world

Which of the following is NOT true? -Enzymes can be activated by protein kinases and deactivated by protein phosphatases -Enzymes are permanently changed during the reactions they catalyze. -Every enzyme is most active at a particular pH and temperature -Prosthetic groups are non-amino acid groups bound to an enzyme. -Enzymes can denature when their non-covalent bonds break causing them to lose their tertiary structure.

Answer: -Enzymes are permanently changed during the retractions they catalyze.

Which of the following is true about the electron transport chain in cellular respiration? -it regenerates NADH from NAD+ -it breaks down Acetyl CoA -it breaks down pyruvate -it increases the number of H+ in the mitochrondrial matrix. -FADH2 is oxidized to FAD

Answer: -FADH2 is oxidized to FAD

_________ is active in all cells, regardless of the presence or the absence of oxygen? -Glycolysis -The citric acid cycle -chemiosmosis -fermentation -pyruvate oxidation

Answer: -Glycolysis

Which of the following is FALSE? -The first molecule formed in the Krebs cycle is citrate -6 NADH molecules are produced per glucose during the citric acid cycle -Glycolysis produces 2 FADH2 molecules -Pyruvate oxidation produces 2 acetyl COA molecules per glucose -Glycolysis produces two pyruvate molecules.

Answer: -Glycolysis produces 2 FADH2 molecules

Identify the true statement. -If a different H+ diffusion channel is inserted in the mitochondrial membrane, ATP synthesis can be uncoupled and energy is lost as heat. -The uncoupling protein thermogenin occurs in human babies and hibernating animals. -Thermogenin is absent in 'brown fat' tissue

Answer: -If a different H+ diffusion channel is inserted in the mitochondrial membrane, ATP synthesis can be uncoupled and energy is lost as heat. -The uncoupling protein thermogenin occurs in human babies and hibernating animals.

Often the active site of an enzyme is much smaller relative to the rest of the enzyme. Which of the following is possible roles of the rest of the macromolecule? -It provides a framework so that the amino acids of the active site are properly positioned in relation to the substrate(s) -It participates in significant changes in protein shape and structure that result in 'induced fit' -It provides binding sites for regulatory molecules.

Answer: -It provides a framework so that the amino acids of the active site are properly positioned in relation to the substrate(s) AND -It provides binding sites for regulatory molecules.

Which of the following is FALSE? -Pyruvate oxidation is catalyzed by the enzyme pyruvate dehydrogenase -In gluconeogensis, glucose is formed from intermediates of the Krebs cycle and glycolysis. -Metabolic pathways share intermediate molecules -Proteins can by hydrolyzed to amino acids and fed into glycolysis or the citric acid cycle -Most catabolic reactions are irreversible

Answer: -Most catabolic reactions are irreversible

**Picture of Malate --> Oxaloacetate** In the above redox reaction..? -NAD+ is oxidizing agent -Malate is reduced to oxaloacetate -Malate is the reducing agent -ALL ARE TRUE

Answer: -NAD+ is oxidizing agent AND -Malate is the reducing agent

Which of the following represents the correct flow of electrons in the mitochondrial membrane? -NADH--> NADH-Q reductase--> cytochrome c reductase--> cytochrome c--> ubiquinone--> cytochrome c oxidase -NADH--> NADH-Q reductase--> ubiquinone--> cytochrome c--> cytochrome c oxidase--> succinate--> dehydrogenase-->cytochrome c reductase --NADH--> NADH-Q reductase--> cytochrome c reductase--> cytochrome c--> ubiquinone--> cytochrome c oxidase --NADH--> NADH-Q reductase--> ubiquinone--> cytochrome c reductase --> cytochrome c --> cytochrome c oxidase

Answer: -NADH--> NADH-Q reductase--> ubiquinone--> cytochrome c reductase --> cytochrome c --> cytochrome c oxidase

Which of the following is FALSE? -GTP is nucleotide used as an energy source in protein synthesis. -A nucleotide is composed of a pentose sugar, a nitrogenous base, and a phosphate group. -Nucleic acids always grow in a 3'-to-5' direction. -The stands that make up a DNA molecule run in opposite directions. -Determining the sequence of bases in DNA helps reveal evolutionary relationships.

Answer: -Nucleic acids always grow in a 3'-to-5' direction.

In the respiratory chain, the final electron acceptor is _________ which is reduced to _________ -CO2, H20 -NAD+, NADH -O2, H2O -FADH2, FAD -O2, glucose

Answer: -O2, H2O

The Miller-Urey experiment lacked which of the following because it was NOT a component of Earth's early atmosphere? -Hydrogen -Ammonia -Water vapor -Oxygen -Methane

Answer: -Oxygen

Which of the following is NOT true? -In DNA and RNA, the 'backbone' is composed of alternating sugar and phosphate groups. -In the polynucleotide chain, sugar and phosphate groups are held together by phosphodiester bonds. -Cytosine, uracil, and thymine are pyrimidines while adenine and guanine are purines. -Purines are single ringed while pyrimidines are double ringed. -In DNA, one strand is held to the other by hydrogen bonds.

Answer: -Purines are single ringed while pyrimidines are double ringed.

Which of the following statements about protocells is FALSE? -They many be a reasonable model for the evolution of cells -Small molecules such as sugars and nucleotides cannot pass through them. -They are organized system of parts -Their interiors are separated from their exteriors. -Their interiors can be chemically distinct from their exterior environment

Answer: -Small molecules such as sugars and nucleotides cannot pass through them.

**Picture of Glyceraldehyde 3-phosphate; 1, 3 Bisphosphoglycerate; 3-Phosphoglycerate** Which of the following is FALSE? -The enzyme labeled 'A'm is glyceraldehyde 3-phosphate dehydrogenase -The ATP is produced by oxidative phosphorylation -The enzyme labeled 'B' is phosphoglycerate kinase -NAD+ is reduced by NADH -In the redox reaction catalyzed by enzyme 'A', glyceraldehyde 3-phosphate is oxidized

Answer: -The ATP is produced by oxidative phosphorylation

Which of the following is FALSE? -The cancer drug methotrexate is an irreversible inhibitor of the enzyme that catalyzes a coenzyme for purine formation -In allosteric regulation, the binding of an activator molecule stabilizes the active form of an enzyme. -Inorganic cofactors include ions of zinc, iron, and copper. -Competitive inhibition can be overcome by adding more substrates. -The nerve has DIPF is an irreversible inhibitor of acetylcholinesterase

Answer: -The cancer drug methotrexate is an irreversible inhibitor of the enzyme that catalyzes a coenzyme for purine formation

All of the following are true EXCEPT...? -Gene expression is a combination of translation and transcription. -Ribozymes are RNA molecules. -The central dogma of molecular biology states that the information flow in a cell is from RNA to polypeptide to DNA. -The diversity of DNA molecules lies in the sequence of base pairs. -Base pairing determines the 3-D shape of some RNA molecules.

Answer: -The central dogma of molecular biology states that the information flow in a cell is from RNA to polypeptide to DNA.

**Bonus - Picture of RNA WORLD and first cells** According the figure, which of the following events must have been occurring between the existence of the 'RNA WORLD' and the evolution of the first cells? -The production of oxygen by cyanobacteria -The formation of cell membranes -The prebiotic synthesis of fatty acids -Photosynthesis

Answer: -The formation of cell membranes AND -The prebiotic synthesis of fatty acids

Which of the following statements is true? -The plot of reaction rate versus substrate concentration for allosteric enzymes often displays a sigmoid (S-shaped) curve -All enzymes are allosterically regulated -Allosteric regulators affect substrate binding but do not affect enzyme structure. -Binding of allosteric regulators is nonspecific -Allosteric regulators always bind to the active site, blocking enzyme function.

Answer: -The plot of reaction rate versus substrate concentration for allosteric enzymes often displays a sigmoid (S-shaped) curve

Which of the following statements about ATP is FALSE? -Bioluminescence is an endergonic reaction driven by ATP hydrolysis -The synthesis of ATP is an exergonic reaction -An ATP is consumed within a second of its formation -An active cell needs to produce millions of ATP molecules per second. -ATP is the 'energy currency' in the cell.

Answer: -The synthesis of ATP is an exergonic reaction

Which of the following is true about transition state intermediates? -They have higher free energies than reactants or products -They are unstable -Their free energies are higher than that of the reactants, but lower than that of the products

Answer: -They have higher free energies than reactants or products -They are unstable

An enzyme, which is a component of a metabolic pathway, is allosterically inhibited by the end product of that particular metabolic pathway Which of the following is true? -This an example of feedback inhibition or end-product inhibition -This is an example of positive regulation -The inhibitor acts non- competitively

Answer: -This an example of feedback inhibition or end-product inhibition AND -The inhibitor acts non- competitively

Consider the following double-stranded DNA region; 5' - TGCCAT-3' 3 - ACGGTA-5' If the lower strand is transcribed, which of the following strands will result? -UGCCAU -TGCCAT -TCGGTA -UGCCUA -TCGGUT

Answer: -UGCCAU

An inhibitor that binds non-covalently to the active site is termed a(n) ________ inhibitor, whereas an inhibitor that binds non-covalently to the enzyme-substrate complex is termed a(n) __________ inhibitor. Both methods of inhibition are ______________. -noncompetitive; competitive; allosteric -competitive; uncompetitive; reversible -noncompetitive; uncompetitive; allosteric -uncompetitive; competitive; reversible

Answer: -competitive; uncompetitive; reversible

A DNA molecule is...? -partially replicated but completely transcribed. -completely replicated and completely translated. -partially replicated but completely translated. -completely replicated but partially transcribed. -partially replicated and partially transcribed.

Answer: -completely replicated but partially transcribed.

In catabolic reactions.... -complex molecules are synthesized from simpler molecules -an input of energy is required. -complex molecules are broken down to simpler molecules. -energy is released

Answer: -complex molecules are broken down to simpler molecules. AND -energy is released

Choose from the list below the correct numbers of ATP molecules released per glucose molecule by glycolysis (gly), the citric acid cycle (CAC), and oxidative phosporylation (OP), and fermentation (fer). -gly 2 (net); CAC 2; OP 28; fer 2 -gly 1 (net); CAC 3; OP 2; fer 0 -gly 2 (net); CAC 4; OP 32; fer 4 -gly 4 (net); CAC 30; OP 4; fer 32

Answer: -gly 2 (net); CAC 2; OP 28; fer 2

Oxygen can cause damage to cellular components because...? -it is very poor electron acceptor -incomplete electron transfer to oxygen, can form toxic intermediates -it makes the cell more acidic -its oxidation forms too much water and will burst the cell

Answer: -incomplete electron transfer to oxygen, can form toxic intermediates

If **Delta G** of a chemical reaction is negative and the change in entropy is positive, you can conclude that the reaction... -requires energy. -is endergonic -is exergonic -decrease the entropy in the system -decreases the disorder in the system.

Answer: -is exergonic

Which of the following is a group of enzymes that is important in allowing organisms to adapt to changes in their environment? -coenzymes -abzymes -isozymes -effectors -activators

Answer: -isozymes

Enzymes increase the rate of the reaction by...? -changing the final equilibrium -increasing the change in free energy -lowering the activation energy -decreasing the change in free energy -increasing the activation energy

Answer: -lowering the activation energy

Compared to fermentation, the aerobic pathways of glucose metabolism produce...? -more ATP -pyruvate -less CO2 -fewer protons for pumping in the mitochondria -less ATP

Answer: -more ATP

In order to determine if a reaction is at 'saturation', you would add __________ and determine if the reaction rate _________. -ATP; increases -more substrate; increases -a competitive inhibitor; decreases -a downstream product; decreases -a noncompetitive inhibitor; decreases

Answer: -more substrate; increases

The main control point of glycolysis is the glycolytic enzyme -phosphofructokinase -ATP synthase -oxaloacetate convertase -lactate dehydrogenase -citrate synthase

Answer: -phosphofructokinase

The statement "enzymes are highly specific" means that specific.... -enzymes are found din specific cells -reactions involving specific substrates are catalyzed by specific enzymes. -enzymes require specific concentrations of substrates. -concentrations of substrates work with specific enzymes. -all enzymes are found only in one specific type of organelle.

Answer: -reactions involving specific substrates are catalyzed by specific enzymes.

In eukaryotes.... -glycolysis occurs inside the mitochondria -the conversion of pyruvate to CO2 occurs in the mitochondria -the conversion of pyruvate to lactate occurs inside the mitochondrion -the respiratory chain enzymes are found at the plasma membrane -the citric acid cycle enzymes are found in the cytoplasm. e

Answer: -the conversion of pyruvate to CO2 occurs in the mitochondria

For a COUPLED reaction which has a net negative *delta*G (-*delta* G) value, which of the following is true? -both reactions need to be exergonic -both reactions need to endergonic -the exergonic reaction needs to release more energy than the endergonic reaction requires. -both reactions need to have the same *delta*G -the *delta* G of the endergonic reaction needs to be more negative than the *delta* G of the exergonic reaction.

Answer: -the exergonic reaction needs to release more energy than the endergonic reaction requires.

In eukaryotic chemiosmosis, a proton-motive force allows protons to move through ATP synthase which couples this movement with ATP synthesis. The protons are moving from... -the outside of the cell to the cytosol -the mitochondrial matrix to the intermembrane space -the cytoplasm to the mitochondrial matrix -the mitochondrial intermembrane space to the matrix -the cytoplasm to the mitochondrial intermembrane space

Answer: -the mitochondrial intermembrane space to the matrix

Which of the following is TRUE? -The sum total of all the chemical reactions in a biological system at a given time is called metabolism. -In biological systems, the total energy is called enthalpy. -A concentration gradient represents potential energy -Free energy (G) is the energy available to do work. -All are true

Answer: ALL ARE TRUE

In the 1990's evidence of cells in rocks 3.5 billion years old was found in Australia. Which of the following is true? -The cells were probably cyanobacteria. -The cells would perform photosynthesis. -The photosynthetic ratio of carbon isotopes (13C.: 12C) was found in the fossils -All are true

Answer: ALL ARE TRUE -The cells were probably cyanobacteria. -The cells would perform photosynthesis. -The photosynthetic ratio of carbon isotopes (13C.: 12C) was found in the fossils