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BIOL 204 > Aerobic Respiration > Flashcards

Aerobic Respiration Flashcards

1
Q

What is cellular respiration?

A

The process of breaking down food molecules in cells to release energy, which is then used to synthesize ATP.

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2
Q

Why is ATP important in cells?

A

ATP powers numerous biosynthetic (anabolic) reactions within a cell.

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3
Q

What role does photosynthesis play in cellular respiration?

A

Photosynthesis produces energy-rich carbon compounds and oxygen, which are essential for cellular respiration.

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4
Q

What makes glucose and other fuels energy-rich?

A

They contain many C—H bonds with electrons that are easily removed and used for work.

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5
Q

Why do fats contain more energy per unit weight compared to proteins and carbohydrates?

A

Fats are mostly made up of C—H bonds, which have high potential energy

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6
Q

What are oxidation-reduction (redox) reactions?

A

Reactions where one molecule loses electrons (oxidation) and another gains them (reduction).

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7
Q

What does the mnemonic “OIL RIG” stand for?

A

Oxidation Is Loss, Reduction Is Gain.

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8
Q

How does oxygen’s electronegativity relate to redox reactions?

A

Oxygen is an excellent electron acceptor because of its high electronegativity.

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9
Q

What happens in the combustion of methane with oxygen?

A

Methane is oxidized, losing electrons, and oxygen is reduced, gaining electrons, releasing energy as heat

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10
Q

How is cellular respiration different from burning fuel?

A

Cellular respiration releases energy in a controlled, stepwise manner through enzyme-catalyzed reactions.

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11
Q

What role do dehydrogenases play in cellular respiration?

A

Dehydrogenases facilitate the transfer of electrons from food molecules to energy carriers like NAD+.

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12
Q

How is energy transferred to NADH used in cellular respiration?

A

The energy in NADH is later used to synthesize ATP efficiently.

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13
Q

Why is the stepwise release of energy in cellular respiration beneficial?

A

It allows energy to be harnessed for metabolic processes instead of being lost as heat.

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14
Q

What are the end products of cellular respiration?

A

Water and carbon dioxide

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15
Q

What is the primary goal of cellular respiration?

A

To convert the potential energy stored in food molecules into ATP for metabolic processes.

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16
Q

Why is glucose the primary focus in cellular respiration?

A

Because it utilizes the entire respiratory pathway.

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17
Q

Where does glycolysis occur, and what happens during this phase?

A

Location: Cytosol.
Process: Enzymes break down one glucose molecule into two pyruvate molecules, synthesizing some ATP and NADH.

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18
Q

Where do pyruvate oxidation and the citric acid cycle occur, and what happens during these phases?

A

Location: Mitochondrial matrix (in eukaryotes).

Process: Pyruvate is oxidized to form acetyl-CoA, which is fully oxidized to carbon dioxide in the citric acid cycle, synthesizing additional ATP and NADH.

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19
Q

Where does oxidative phosphorylation occur, and what happens during this phase?

A

Location: Inner mitochondrial membrane (in eukaryotes).

Process: NADH is oxidized, and electrons are passed through the ETC to oxygen, producing water and creating a proton gradient that drives ATP synthesis.

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20
Q

What are the three main phases of cellular respiration?

A

Glycolysis, pyruvate oxidation and citric acid cycle, and oxidative phosphorylation.

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21
Q

What is the mitochondrion, and why is it important?

A

A specialized membrane-bound organelle, often called the “powerhouse of the cell,” because it is the main site of ATP production.

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22
Q

Describe the structure of a mitochondrion.

A

Composed of an outer membrane and an inner membrane, with two main compartments: the intermembrane space and the matrix.

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23
Q

Where do glycolysis and the citric acid cycle occur in archaea and bacteria?

A

Both occur in the cytosol

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24
Q

Where does oxidative phosphorylation occur in archaea and bacteria?

A

On internal membranes.

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25
Q

What is the matrix, and what occurs there?

A

The inner aqueous environment of the mitochondrion where the citric acid cycle occurs.

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26
Q

Is cellular respiration unique to eukaryotes?

A

No, many species of archaea and bacteria also perform cellular respiration through glycolysis and oxidative phosphorylation.

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27
Q

What is glycolysis?

A

Glycolysis is a series of 10 enzyme-catalyzed reactions that break down glucose into two molecules of pyruvate, releasing energy to synthesize NADH and ATP.

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28
Q

Why is glycolysis considered an ancient metabolic process?

A

It is one of the oldest and most fundamental metabolic pathways, found in all three domains of life: Archaea, Bacteria, and Eukarya.

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29
Q

Does glycolysis require oxygen?

A

No, glycolysis does not require oxygen and occurs in the cytosol of all cells.

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30
Q

What happens during the energy investment phase of glycolysis?

A

Two ATP molecules are consumed to phosphorylate glucose, converting it into fructose-1,6-bisphosphate, which is then split into two three-carbon molecules.

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31
Q

What happens during the energy payoff phase of glycolysis?

A

The two three-carbon molecules are further processed to produce four ATP molecules by substrate-level phosphorylation and two NADH molecules.

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32
Q

How does glycolysis result in a net gain of ATP?

A

Although two ATP molecules are consumed in the energy investment phase, four ATP molecules are produced in the energy payoff phase, resulting in a net gain of two ATP molecules

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33
Q

What is substrate-level phosphorylation?

A

It is the process of producing ATP by transferring a phosphate group from a high-energy substrate to ADP, facilitated by specific enzymes.

34
Q

How does carbon retention work in glycolysis?

A

The six-carbon glucose molecule is converted into two three-carbon pyruvate molecules, with no loss of carbon atoms.

35
Q

What do the key concepts of glycolysis highlight?

A

The efficiency and ancient origins of glycolysis, reflecting its crucial role in cellular energy production across all forms of life.

36
Q

What is the goal of pyruvate oxidation and the citric acid cycle?

A

To extract the remaining energy from pyruvate and convert it into ATP and electron carriers like NADH.

37
Q

Where does pyruvate oxidation occur?

A

In the mitochondrial matrix.

38
Q

How does pyruvate reach the mitochondrial matrix?

A

Pyruvate crosses the outer membrane through large pores and requires a specific carrier to cross the inner membrane.

39
Q

What happens during the decarboxylation step of pyruvate oxidation?

A

The carboxyl group (—COO^-) of pyruvate is removed as carbon dioxide.

40
Q

What occurs during the oxidation step of pyruvate oxidation?

A

The remaining two-carbon molecule (acetate) is oxidized, transferring electrons and a proton to NAD^+, forming NADH.

41
Q

What is formed when the acetate group binds to coenzyme A (CoA)?

A

Acetyl-CoA, a high-energy intermediate.

42
Q

What is the structure of the citric acid cycle?

A

It consists of eight enzyme-catalyzed reactions, with seven enzymes soluble in the mitochondrial matrix and one bound to the inner mitochondrial membrane.

43
Q

What is the function of the citric acid cycle?

A

To oxidize acetyl groups to carbon dioxide, generating ATP, NADH, and FADH_2.

44
Q

How are the products of the citric acid cycle doubled?

A

Glycolysis produces two molecules of pyruvate from one glucose molecule, so the products of the citric acid cycle are doubled for the complete oxidation of one glucose molecule.

45
Q

What happens to the carbon atoms originally present in glucose by the end of the citric acid cycle?

A

They have been completely oxidized and released as carbon dioxide.

46
Q

What is the role of the Electron Transport Chain (ETC) and chemiosmosis?

A

To extract the potential energy in NADH and FADH2 and synthesize additional ATP.

47
Q

Where is the respiratory ETC located in eukaryotes?

A

On the inner mitochondrial membrane.

48
Q

Name the four protein complexes in the ETC.

A

Complex I: NADH dehydrogenase
Complex II: Succinate dehydrogenase
Complex III: Cytochrome complex
Complex IV: Cytochrome oxidase.

49
Q

What are the two mobile electron shuttles in the ETC?

A

Ubiquinone and Cytochrome c.

50
Q

What do prosthetic groups do in the ETC?

A

They are redox-active cofactors that alternate between reduced and oxidized states, facilitating electron transport.

51
Q

What drives the electron transport in the ETC?

A

The free energy gradient from high-energy NADH to low-energy O2.

52
Q

How does chemiosmosis power ATP synthesis?

A

By using the energy from the proton gradient created by electron transport to synthesize ATP through ATP synthase.

53
Q

Describe the structure of ATP synthase.

A

It has a basal unit in the inner mitochondrial membrane, connected to a headpiece by a stalk. The basal unit forms a channel for protons, and the headpiece catalyzes ATP formation.

54
Q

What happens when electron transport and ATP generation are uncoupled?

A

The energy is released as heat instead of ATP production, which can be used by some organisms to regulate body temperature.

55
Q

Why is it important to determine the total number of ATP molecules synthesized per glucose molecule?

A

To integrate all parts of the respiratory pathway and calculate the efficiency of energy extraction from glucose.

56
Q

How many ATP molecules are synthesized per NADH and FADH2 during oxidative phosphorylation?

A

Approximately 3 ATP per NADH and 2 ATP per FADH2.

57
Q

What are the total ATP yields from glycolysis, pyruvate oxidation, and the citric acid cycle?

A

Glycolysis: 2 ATP, 2 NADH. Pyruvate oxidation: 2 NADH. Citric acid cycle: 2 ATP, 6 NADH, 2 FADH2.

58
Q

What is the theoretical total ATP yield per glucose molecule?

A

38 ATP per glucose molecule.

59
Q

What factors reduce the theoretical ATP yield in cellular respiration?

A

Transport costs, coupling efficiency, and proton-motive force use for other cellular activities.

60
Q

How is the efficiency of cellular respiration calculated?

A

Efficiency = (Energy from ATP / Total Energy from Glucose Oxidation) × 100% ≈ 38%.

61
Q

Besides glucose, what other molecules can be oxidized by cellular respiration?

A

Carbohydrates, fats, and proteins.

62
Q

How do fats and proteins enter the respiratory pathway?

A

Fats: Triglycerides are hydrolyzed into glycerol (enters glycolysis) and fatty acids (enter the citric acid cycle as acetyl-CoA).

Proteins: Amino acids are deaminated and enter as pyruvate, acetyl-CoA, or citric acid cycle intermediates.

63
Q

What is the role of respiratory intermediates in anabolic reactions?

A

They are used to synthesize amino acids, fats, and nucleotides needed for cell function.

64
Q

How is cellular respiration regulated to match ATP generation with cellular energy needs?

A

Through feedback inhibition, where end-products inhibit early pathway enzymes.

65
Q

Which enzyme is key in the regulation of glycolysis and how is it regulated?

A

Phosphofructokinase, inhibited by ATP and activated by ADP. Citrate also regulates this enzyme.

66
Q

Why is feedback inhibition important in cellular respiration?

A

It ensures efficient ATP production and balances energy supply and demand according to the cell’s needs.

67
Q

What is an anaerobe?

A

An organism that does not require oxygen for growth and may even die in its presence, using other molecules as the final electron acceptor.

68
Q

What is anaerobic respiration?

A

A type of respiration that does not use oxygen as the final electron acceptor but uses molecules like sulfate, nitrate, or carbon dioxide to generate ATP in oxygen-lacking environments.

69
Q

What is ATP synthase?

A

An enzyme complex located in the inner mitochondrial membrane (or cell membrane of prokaryotes) that synthesizes ATP from ADP and inorganic phosphate during oxidative phosphorylation using the proton-motive force.

70
Q

What is cellular respiration (aerobic respiration)?

A

A metabolic process in which cells use oxygen to convert biochemical energy from nutrients into ATP, releasing carbon dioxide and water as byproducts.

71
Q

What is chemiosmosis?

The movement of ions, usually protons, across a semipermeable membrane, down their electrochemical gradient, used in cellular respiration to generate ATP via ATP synthase.

A

The movement of ions, usually protons, across a semipermeable membrane, down their electrochemical gradient, used in cellular respiration to generate ATP via ATP synthase.

72
Q

What is the citric acid cycle (Krebs cycle)?

A

A series of enzyme-catalyzed reactions in the mitochondrial matrix that oxidizes acetyl-CoA to carbon dioxide, generating NADH, FADH2, and ATP (or GTP).

73
Q

What is the electron transport chain (ETC)?

A

A series of protein complexes and other molecules in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, pumping protons to create a gradient that drives ATP synthesis.

74
Q

What is a facultative anaerobe?

A

An organism that can grow with or without oxygen, switching between aerobic respiration and anaerobic pathways depending on oxygen availability.

75
Q

What is fermentation?

A

A metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen, regenerating NAD+ from NADH to enable glycolysis to continue producing ATP.

76
Q

What is glycolysis?

A

The first stage of cellular respiration occurring in the cytoplasm, where one molecule of glucose is broken down into two molecules of pyruvate, generating a net gain of 2 ATP and 2 NADH.

77
Q

What is nicotinamide adenine dinucleotide (NAD+)?

A

A coenzyme that functions as an electron carrier in redox reactions, cycling between its oxidized form (NAD+) and reduced form (NADH) during cellular respiration.

78
Q

What is oxidative phosphorylation?

A

The final stage of cellular respiration in the inner mitochondrial membrane, where ATP is synthesized due to electron transfer from NADH and FADH2 to oxygen by the electron transport chain and chemiosmotic process.

79
Q

What is proton-motive force?

A

The force generated across a membrane during electron transport, driving proton movement across the membrane and used to synthesize ATP via ATP synthase.

80
Q

What is pyruvate oxidation?

A

The process in the mitochondrial matrix where pyruvate from glycolysis is converted into acetyl-CoA, producing NADH and releasing carbon dioxide.

81
Q

What is substrate-level phosphorylation?

A

ATP production occurring when an enzyme transfers a phosphate group directly from a substrate molecule to ADP, occurring during glycolysis and the citric acid cycle.

82
Q

What is uncoupling?

A

The process where the proton gradient generated by the electron transport chain is dissipated without ATP production, generating heat instead, which occurs naturally in brown fat cells through uncoupling proteins.

BIOL 204 (6 decks)

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