Bio 110 Chapter 7: Cellular Respiration and Fermentation (Exam 2) (Connect Answers)

Q11: How many ATP and NADH molecules are produced from each molecule of glucose in the citric acid cycle only?

2 ATP, 6 NADH

Net ATP Yield of Glycolysis

2 ATP;

Acetyl CoA

2 C-C

2 Pyruvic Acids

2 C-C-C

Oxaloacetate

2 C-C-C-C

Citric Acid

2 C-C-C-C-C-C

Glycolysis Produces

2 net ATPs 2 NADHs

Q3: Which of the following are the final by-products of glucose oxidation during aerobic cell respiration?

ATP, heat, and carbon dioxide

Produces Citric Acid

Acetyl CoA + Oxaloacetate

Q9: Which compound has the highest free energy and produces the most ATP per molecule when oxidized?

Glucose

Q22: In addition to ATP, what are the end products of glycolysis?

NADH and pyruvate

Q1: In the equation, C6H12O6 + 6O2 → 6CO2 + 6H2O, ATP and heat would be on which side of the reaction?

The products because this is an exergonic reaction.

Q45: Bacteria that produce nitrite ( NO2- ) during anaerobic respiration would use ___ as their final electron acceptor.

NO3-

Does Glycolysis differ in different species?

No, it's nearly identical in every living species;

Does Glycolysis need Oxygen

Not necessarily, it can occur with or without O2;

Glycolysis

Occurs in the cytoplasm and in all organisms in the same manner. Can occur without oxygen. Glucose to 2 Pyruvic Acids.

Loss of electrons Addition of oxygen Loss of hydrogen Exergonic NADH to NAD+ FADH2 to FAD C-OH to C=O

Oxidation

Q10: Cellular respiration produces the most energy in the form of ATP from which of the following? 1. production of lactate 2. glycolysis 3. substrate-level phosphorylation 4. oxidative phosphorylation 5. the citric acid cycle

Oxidative Phosphorylation

Stage 4 of Cellular Respiration

Oxidative Phosphorylation

Cellular Respiration

Process by which living cells get energy from organic molecules;

Q19: During glycolysis, glucose is broken down into

Pyruvate

Q39: The reaction: pyruvate + CoA + NAD+ → acetyl CoA + CO2 + NADH, is catalyzed by pyruvate dehydrogenase. If an inhibitor of this enzyme was added to cells, then ___ levels in the cytoplasm would increase.

Pyruvate

What breaks down the pyruvate?

Pyruvate dehydrogenase Molecule of CO2 removed from each pyruvate Remaining acetyl group attached to CoA to makeacetyl CoA Yield = 1 NADH for each pyruvate

Q38: In the reaction: pyruvate + CoA + NAD+ → acetyl CoA + CO2 + NADH.

Pyruvate is oxidized and NAD+ is reduced.

Does NADH oxidation achieve its full potential?

Rarely, b.c. 1. NADH also used in anabolic pathways 2. H+ gradient used for other purposes

NADH

Reduced form of NAD+

Gain of electrons Loss of oxygen Addition of hydrogen Endergonic NAD+ to NADH FAD to FADH2 C=O to C-OH

Reduction

Q20: The ATP made during glycolysis is generated by

Substrate-level phosphorylation.

Citric Acid Cycle Produces

Takes 10 steps 2 ATPs 8 NADHs 2 FADH_2s

Q21: During the cleavage stage of glycolysis, fructose-1, 6 biphosphate is broken down into

Two molecules of glyceraldehyde-3-phosphate

Aerobic Respiration

Uses Oxygen, release Carbon Dioxide; Mostly, use glucose, but other molecules can be used too.

Q27: If you measure the air a person inhales you observe that the concentrations ______ in the air they exhale.

of O2 falls and CO2 rises

Q25: In the citric acid cycle, malate is oxidized to form

oxaloacetate

Q26: The enzyme responsible for converting pyruvate to acetyl CoA is called

pyruvate dehydrogenase

Q24: In the citric acid cycle, succinate is oxidized to form

Fumarate

Q12: How many net ATP and NADH molecules are produced from one molecule of glucose during glycolysis?

2 ATP, 2 NADH

ATP synthase

1. ATP synthase captures free energy as H+ ions flow through 2. The enzyme converts energy from the proton motive force of the H+ gradient to chemical bond energy in ATP

Other acceptors for E coli.

1. E. coli uses nitrate (NO3-) under anaerobic conditions 2. Also makes ATP via chemiosmosiseven under aerobic conditions

Name 3 Stages of Glycolysis

1. Energy Investment put 2 ATP; 2. Cleavage 6 carbon --> 2 3-carbons;; 3. Energy Liberation - 2 pyruvate, 2 NADH, 4 ATP;

Besides glucose, other molecules also used for energy: carbohydrates, proteins, fats

1. Enter into glycolysis or citric acid cycle at different points 2. Utilizing the same pathways for breakdown increases efficiency

Fermentation

1. Fermentation is the breakdown of organic molecules without net oxidation 2. Many organisms can only use O2 as final electron acceptor, so under anaerobic conditions, they need a different way to produce ATP, like using glycolysis 3. But glycolysis uses up NAD+ and makes too much NADH under anaerobic conditions (dangerous situation) 4. Muscle cells solve problem by reducing pyruvate into lactate 5. Yeast solve problem by making ethanol 6. Fermentation produces far less ATP than oxidative phosphorylation

4 Metabolic Pathway for Glucose Metabolism

1. Glucolysis; 2. Breakdown of pyruvate; 3. Citric Acid Cycle; 4. Oxidative Phosphorylation;

Oxidative Phosphorylation

1. High energy electrons removed from NADH and FADH2 to make ATP 2. Typically requires oxygen 3. Oxidative process involves electron transport chain 4. Phosphorylation occurs by ATP synthase

Phosphorylation by ATP synthase

1. Lipid bilayer of inner mitochondrial membrane is relatively impermeable to H+ 2. Protons can only pass through ATP synthase 3. Harnesses free energy to synthesize ATP from ADP

Yoshida and Kinosita demonstrated thatthe γ subunit of the ATP synthase spins

1. Masasuke Yoshida, Kazuhiko Kinosita, and colleagues set out to visualize the rotary nature of the ATP synthase 2. They released membrane embedded portion and adhered it to a slide 3. Revealed γ subunit using fluorescence 4. Added ATP to make reaction run backward 5. Rotated counterclockwise to hydrolyze ATP. So it must rotate clockwise to synthesize ATP

NADH oxidation makes mostof the cell's ATP

1. NADH oxidation creates the H+ electrochemical gradient used to synthesize ATP 2. Yield = up to 30-34 ATP molecules / glucose

Oxidation by the Electron Transport Chain (ETC)

1. Protein complexes and small organic molecules embedded in the inner mitochondrial membrane 2. Accept and donate electrons in a linear manner in a series of redox reactions 3. Movement of electrons generates an H+ electrochemical gradient (proton-motive force) 4. This provides energy for the next step -synthesizing ATP

2 Strategies for Anaerobic Respiration

1. Use substance other than O2 as final electron acceptor in electron transport chain 2. Produce ATP only via substrate-level phosphorylation

Initial electron holders into ETC

10 NADHs 2 FADH_2s

Q17: Assuming that the glycerol backbone of a fat molecule can be converted to glyceraldehyde-3-phosphate, an intermediate in glycolysis, how many ATP can be produced from the glycerol backbone of a fat molecule?

18 (educated guess)

Q28: If an athlete is burning glucose only, predict the ratio of oxygen consumed to carbon dioxide that will be produced.

1:1

Max Cellular Respiration efficiency results in how many ATP?

38 ATP

Q7: Which of the following are produced during the citric acid cycle?

ATP, NADH, and FADH2

Q40: When acetyl-CoA containing radioactively labeled carbon atoms is fed to cells, the CO2 produced is not initially radioactive. However, molecules of citrate and oxaloacetate are radioactive. Only after some time has passed will radioactive CO2 released. What is the best explanation for this observation?

Acetyl groups are metabolized directly into CO2.

Q41: In the citric acid cycle, some intermediates are used in other metabolic reactions. Which of the following adaptations would need to be made by a cell in response to this?

Acetyl groups are not metabolized directly into CO2, but enter a cyclical metabolic pathway

Citric Acid Cycle

Acetyl is removed from Acetyl CoA and attached to oxaloacetate to form citrate (aka citric acid); Series of steps releases 2 CO2, 1 ATP, 3 NADH, and1 FADH2; Oxaloacetate is regenerated to start the cycle again;

Q36: In a PET scan a patient is injected with radioactively labeled glucose. Why would cancer cells take up more of the radioactive glucose than surrounding non-cancerous tissues?

Because the produce more enzymes found in glycolysis

Q14: Which of the following statements is TRUE of both aerobic and anaerobic respiration? Both produce either lactic acid or ethanol as a biproduct. Both produce NADH as high-energy intermediates. Both produce NADH as high-energy intermediates and both produce either lactic acid or ethanol as a bioproduct. Both use glycolysis to oxidize glucose to pyruvate and both produce NADH as high-energy intermediates. Both use glycolysis to oxidize glucose to pyruvate.

Both use glycolysis to oxidize glucose to pyruvate and both produce NADH as high-energy intermediates.

Stage 2 of Cellular Respiration

Breakdown of Pyruvate; In eukaryotes, pyruvate is transported into the mitochondrial matrix;

Glucose

C-C-C-C-C-C

Formula for Glucose Metabolism

C6H12O6 +6 O2 --> 6CO2 and 6H2O

Warburg effect

Cancer cells preferentially use glycolysis while decreasing oxidative phosphorylation

Q2: The equation, C6H12O6 + 6O2 →6CO2 + 6H2O (ATP + Heat), describes which of the following processes?

Cell respiration

Chemiosmosis

Chemical synthesis of ATP as a result of pushing H + across a membrane

Q23: In the citric acid cycle, the acetyl group is removed from acetyl CoA and attached to oxaloacetate to form

Citrate

Stage 3 of Cellular Respiration

Citric Acid Cycle

NAD+

Coenzyme found living in cells; In metabolism, NAD+ is involved in redox reactions, carrying electrons from one reaction to another. The coenzyme is, therefore, found in two forms in cells: NAD+ is an oxidizing agent - it accepts electrons from other molecules and becomes reduced. This reaction forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD+.

Q13: High-energy electrons from molecules of NADH and FADH2 are transferred to a chain of proteins within the electron transport chain. What is the final protein in the electron transport chain?

Cytochrome c

Q5: Where does glycolysis takes place?

Cytosol

Q33: When heart muscles cells are deprived of oxygen, the heart still pumps. What must the heart cells be able to do?

Derive sufficient energy from fermentation

Q32: Which of the following do yeast produce during fermentation?

Ethanol.

Q46: The conversion of pyruvate to acetyl CoA is irreversible. Predict what would happen to fatty acids as a result of this.

Fatty acids cannot be converted into carbohydrates.

Anaerobic Respiration and Fermentation

For environments that lack oxygen or during oxygen deficient times

Q35: The formation of each pyruvate in glycolysis also produces a net of 2 NADH and 2 ATP. However, each metabolism of glucose produces a net of 4 NADH and 4 ATP. How is this explained?

Glucose is cleaved into two three carbon sugars that are metabolized into pyruvate.

Q4: Which of the following processes will occur in the presence or absence of oxygen?

Glycolysis

Stage 1 of Cellular Respiration

Glycolysis

Cancer and Glycolyc Enzymes

Glycolytic enzymes overexpressed in 80% of all types of cancers; May be due to low oxygen levels inside tumors, with overexpression of glycolysis genes in response;

Q44: Some bacteria can use sulfur instead of oxygen as a final electron acceptor. What would they produce during anaerobic respiration?

H2S

Chemiosmosis

Harnessing the gradient potential into energy to facilitate chemical reactions.

Which part of the mitochondria is acidic?

Inner mitochondrial space

Cancer Cells Usually Exhibit High Levels of Glycolysis

Keep Going - you are doing great!

Q30: Sports physiologists at an Olympic training center wanted to monitor athletes to determine at what point their muscles were functioning anaerobically. They could do this by checking for the buildup of which molecule?

Lactate

Q6: Which occurs only in anaerobic metabolism of glucose?

Lactate fermentation

Q18: Where are the protein complexes associated with the electron transport chain located?

Mitochondrial inner membrane

Q29: Energy released by the electron transport chain is used to pump H+ ions into which location?

Mitochondrial intermembrane space

Q42: When scientists placed ATP Synthase linked to fluorescent actin on a microscope slide and added ATP, the actin could be seen spinning. If the scientists instead added ADP what would happen?

The actin would not spin because it required ATP hydrolysis.

Q43: When scientists placed ATP Synthase linked to fluorescent actin on a microscope slide and added ATP, the actin could be seen spinning counterclockwise. If the experiment could be replicated in a cell going through oxidative phosphorylation what would happen?

The actin would spin clockwise because ATP would be produced instead of hydrolyzed.

Q8: Which of the following statements is true? 1. Electron transport chain and ATP synthase are in the cytosol. 2. The citric acid cycle occurs in the mitochondria matrix. 3. The citric acid cycle occurs in the cytosol. 4. Oxidative phosphorylation occurs in the mitochondria matrix. 5. Glycolysis occurs in the mitochondria inner membrane.

The citric acid cycle occurs in the mitochondria matrix.

Q16: Which of the following statements about the electron transport chain in cell respiration is CORRECT? 1. The loss in free energy of the electron initially donated by NADH is used to transport H+ across the inner mitochondrial membrane against its electrochemical gradient. 2. The ATP synthase generates a H+ gradient across the inner mitochondrial membrane. 3. Electrons move from NADH to a chain of proteins with lower electronegativities. 4. The electron transport chain of proteins uses ATP to pump H+ across the inner mitochondria membrane against its electrochemical gradient. 5. The electron transport chain of proteins contains pores that are leaky to H+.

The loss in free energy of the electron initially donated by NADH is used to transport H+ across the inner mitochondrial membrane against its electrochemical gradient.

Q15: Which would be TRUE if an inhibitor blocked the activity of mitochondrial ATP synthase?

The pH in the space between the mitochondrial membranes would increase.

Q34: If glucose was not phosphorylated in the first few reactions of glycolysis which of the following would occur?

The reactions in glycolysis following the phosphorylation would not be exergonic.

Q37: In a PET scan a patient is injected with radioactively labeled glucose. Cancer cells are often in a hypoxic environment, why would this lead to an increase in glucose uptake?

They rely more on glycolysis which is less efficient than oxidative phosphorylation.

What is the main point of Cellular Respiration?

To make ATP and NADH

Q31: The reaction of ethanol fermentation is: pyruvate + NADH → ethanol + CO2 + NAD+. Why would a yeast need to perform this reaction in the absence of oxygen?

To produce NAD+ allowing glycolysis to continue.