Chapter 4: Cell Respiration

Question 1

cellular respiration

Answer 1

process of extracting energy stored in food (catabolism) and transferring that energy to molecules of ATP

Question 2

complete equation of aerobic respiration

Answer 2

C6H12O6 + 6O2 –> 6CO2 + 6H2O + 38 ATP

Question 3

anaerobic cellular respiration

Answer 3

oxygen is not present

1. glycolysis
2. alcoholic fermentation or lactic acid fermentation

Question 4

aerobic respiration

Answer 4

oxygen is present

1. glycolysis
2. Citric acid cycle (Krebbs cycle)
3. electron transport chain
4. oxidative phosphorylation

Question 5

ATP (adenosine triphosphate)

Answer 5

• adenosine (adenine nucleotide + ribose) and 3
• when one phosphate group is removed from unstbale ATP through hydrolysis, it becomes a stable molecule of ADP (releases energy)
• living organisms need a constant input of energy
• provides energy by transferring phosphates from ATP to another molecule

Question 6

glycolysis

Answer 6

• a ten-step process tat breaks down one molecule of glucose into 2 3-carbon molecules of pyruvate (pyruvic acid)
  -anaerobic process in cytoplasm
  -each step is catalyzed by a different enzyme
  -uses substrate level phosphorylation
  2ATP + 1 Glucose –> 2Pyruvate + 4ATP

Question 7

substrate level phosphorylation

Answer 7

direct enzymatic transfer of phosphate group to ADP that produces a small amount of ATP

Question 8

regulation of ATP production

Answer 8

• through allosteric inhibition
• ex: PFK is allosteric enzyme, inhibits glycolysis when there is enough ATP by binding to the nonactive site (ATP= inhibitor)

Question 9

anaerobes

Answer 9

• faculative anaerobes: tolerate oxygen

- obligate anaerobes: can’t tolerate oxygen in environment

Question 10

fermentation

Answer 10

-catabolic process that can create ATP if there is enough NAD+ (converted from NADH) to accept electrons during glycolysis

Question 11

alcohol fermentation

Answer 11

-process cells convert pyruvate from glycolysis into ethyl alcohol and carbon dioxide
-beer, bread, wine
Pyruvate + NADH –> CO2 + Ethanol + NAD+

Question 12

lactic acid fermentation

Answer 12

• pyruvate is reduced to form lactic acid (lactate)
• yogurt and cheese
• skeletal muscles during exercise

Question 13

Citric Acid Cycle

Answer 13

• in matrix of the mitochondria
• turns twice every molecule of glucose
• generates 1 ATP per turn through substrate level phosphorylation
• most of the chemical energy is transferred to NAD+ and FAD
• reduced coenzymes (NADH and FADH2) shuttle high energy electrons into ETC in cristae membrane

Question 14

Steps of Citric Acid Cycle

Answer 14

1. pyruvate combines with Coenzyme A to form acetyl co-A, producing 2 molecules of NADH (1 NADH per pyruvate)
2. acetyl co-A combines with oxaloacetic acid (OAA) to produce citric acid
3. each cycle of Krebs produces 2 NADH, 1 ATP. 1 FADH2, and CO2

Question 15

Structure of Mitochondria

Answer 15

• enclosed by double membrane
• outer membrane: smooth
• inner membrane (cristae): folded, divides into matrix and outer compartment

Question 16

NAD+ and FAD

Answer 16

• coezymes that are required for normal cell respiration and carry protons or electrons from glycolysis and the Krebs Cycle to the ETC
• specific enzymes facilitate transfer of H atoms from substrate to coenzyme
• oxidized form of NADH (carries 2 electrons and 1 proton) and FADH2

Question 17

electron transport chain

Answer 17

• aerobic respiration in the cristae membrane that couples exergonic flow of electrons to produce one endergonic reaction (pumping of protons against a gradient)
• proton gradient: created when use energy from exergonic reaction to pump protons from matrix to the outer compartment
• makes no ATP but prepares cell for production during chemiosmosis (movement of ions across a selectively permeable membrane, down their electrochemical gradient through ATP synthase)

Question 18

important facts of the electron transport chain

Answer 18

• ETC carries electrons delivered by NAD and FAD from glycolysis and Krebs cycle to oxygen (the final electron acceptor) through a series of redox reactions
• oxygen pulls electron through ETC beacuse it is electronegative
• NADH delivers electrons to a higher energy level in ETC than FADH2 (NADH produces 3 ATP and FADH2 produces 2 ATP)
• ETC consists of cytochromes (used to trace evolutionary relationships because they are present in all aerobes)

Question 19

oxidative phosphorylation

Answer 19

-most of the energy released during cellular respiration through phosphorylation of ADP into ATP by oxidation of carrier molecules NADH and FADH2

Question 20

chemiosmotic theory

Answer 20

• created by Peter Mitchell

- chemiosmosis uses potential energy stored in the form of a proton gradient (H+) due to phosphorylate ADP to ATP

Question 21

important facts of oxidative phosphorylation

Answer 21

• powered by redox reactions of ETC
• protons can’t flow through the membrane, but must go through ATP synthase
• oxygen is the final hydrogen acceptor, combining half an O2 molecule with 2 protons, forming water

Question 22

summary of ATP production

Answer 22

1. substrate level phosphorylation: kinase (enzyme) directly transfers phosphate from substrate to ADP, used during Krebs Cycle and glycolysis, produces small amount ATP
2. oxidative phosphorylation: occurs during chemiosmosis, produces 90% ATP in cellular respiration, NAD and FAD lose protons to ETC which pumps them to the outer compartment, creating a proton gradient that provides energy to convert ADP to ATP
3. glucose –> NADH and FADH2 –> ETC –> cheiososmosis –> ATP
4. aerobic cellular respiration produces about 26-28 ATP
5. each pyruvte molecule enters glycolysis separately (2 pyruvate to one glucose)