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Biology 1610 > Chapter 9: Cellular Respiration and Fermentation > Flashcards

Chapter 9: Cellular Respiration and Fermentation Flashcards

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1
Q

A partial degradation of sugars or other organic fuel that occurs without the use of oxygen.

A

Fermentation

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2
Q

The most efficient catabolic pathway

A

Aerobic respiration

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3
Q

Pathway in which oxygen is consumed as a reactant along with the organic fuel

A

aerobic respiration

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4
Q

T/F the cells of most eukaryotic and many prokaryotic organisms can carry out aerobic respiration.

A

True

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5
Q

a process in some prokaryotes that use substances other than oxygen as reactants in a similar process to aerobic respiration that harvests chemical energy without oxygen

A

anaerobic respiration

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6
Q

the term that includes both aerobic and anaerobic processes

A

cellular respiration

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7
Q

The overall process of aerobic respiration can be summarized by what formula?

A

organic compounds + oxygen –> carbon dioxide + water + energy

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8
Q

Is the breakdown of glucose endergonic or exergonic? Why?

A

exergonic, because there is a free energy change of -686 kcal per mole of glucose decomposed.

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9
Q

T/F catabolic pathways directly move flagellum pump solutes across membranes, polymerize monomers, and perform other cellular work.

A

False

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10
Q

How do the catabolic pathways that decompose glucose and other organic fuels yield energy?

A

The relocation of electrons releases energy stored in organic molecules, and this energy ultimately is used to synthesize ATP.

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11
Q

What are oxidation-reduction reactions?

A

the transfer of electrons from one reactant to another

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12
Q

Oxidation-reduction reactions are called _______ for short.

A

redox reactions

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13
Q

the loss of electrons from one substance

A

oxidation

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14
Q

the addition of electrons to another substance

A

reduction

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15
Q

NOTE**
Adding electrons is called reduction; adding negatively charged electrons to an atom reduces the amount of positive charge of that atom

A

FREEBEE

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16
Q

Given the following reaction, what is being reduced and what is being oxidized?
Na + Cl –> Na+ + Cl-

A

Na becomes oxidized because it loses an electron and Cl becomes reduced because it gains an electron

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17
Q

If we were to generalize the redox reaction with this formula:
Xe- + Y —> X + Ye-
The Xe- would be the reducing agent, it reduces Y, which accepts the donated electron.
The Y, or electron acceptor, would be the oxidizing agent, oxidizing Ye- by removing its electron.

A

FREEBEE

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18
Q

T/F Oxidation and reduction ALWAYS go hand in hand.

A

True

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19
Q

Why is oxygen so potent as an oxidizing agent?

A

Because of its electronegativity

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20
Q

In the following equation, what is being oxidized and what is being reduced?
C6H1206 + 6O2—> 6CO2 + 6H2O + energy

A

C6H12O6 becomes oxidized whereas 6O2 becomes reduced

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21
Q

Loss of hydrogen =

A

oxidation

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22
Q

Addition of hydrogen =

A

Reduction

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23
Q

If energy is released from a fuel all at once, can it be harnessed efficiently for constructive work?

A

No. This is why cellular respiration doesn’t oxidize glucose but rather glucose is broken down in series of steps, each one catalyzed by an enzyme.

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24
Q

At key steps, electrons are stripped from the glucose. As is often the case in oxidation reactions, each electron travels with a proton, thus a hydrogen atom.

A

FREEBEE

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25
Q

Are hydrogen atoms usually directly transferred to oxygen?

A

No, they are usually passed first to an electron carrier, a coenzyme called NAD+.

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26
Q

Why is NAD+ well suited to be an electron carrier?

A

Because it can cycle easily between oxidized (NAD+) and reduced (NADH+)

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27
Q

As an electron acceptor, how does NAD+ function during respiration?

A

As an oxidizing agent.

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28
Q

How does NAD+ trap electrons from glucose and the other organic molecules in food?

A

Enzymes called dehydrogenases remove a pair of hydrogen atoms (2 electrons and protons) from the substrate thereby oxidizing it. The enzyme delivers the 2 electrons along with 1 proton to its coenzyme NAD+. The other proton is released as a hydrogen ion into the surrounding solution. By receiving 2 negatively charged electrons but only 1 positively charged proton, the nicotinamide portion of NAD+ has its charge neutralized when NAD+ is reduced to NADH.

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29
Q

What does NAD+ stand for? And what is it a derivative of?

A

Nicotinamide adenine dinucleotide

It is a derivative of the vitamin Niacin.

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30
Q

T/F Electrons lose very little of their potential energy when they are transferred from glucose to NAD+.

A

True.

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31
Q

Cellular respiration brings H2 and O2 together just like combustion of H2 and O2 that is harnessed to power main engines of the space shuttle. But there are 2 differences, what are they?

A
  1. In cellular respiration, the hydrogen that reacts with oxygen is derived from organic molecules rather than H2.
  2. Instead of occuring in one explosive reaction, respiration uses an electron transport chain to break the fall of the electrons to oxygen into several energy-releasing steps.
32
Q

What does an electron transport chain consist of?

A
  • a number of molecules, mostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells and the plasma membrane of aerobically respiring prokaryotes.
33
Q

Where is the electron transport chain in eukaryotic cells?

A

The inner membrane of the mitochondria

34
Q

Where is the electron transport chain located in prokaryotes that aerobically respire?

A

The plasma membrane

35
Q

Electrons removed from glucose are shuttled by NADH to the higher energy part ( top) of the chain. At the lower energy end (bottom) O2 captures these electrons along with hydrogen nuclei forming water.

A

FREEBEE

36
Q

T/F Anaerobically respiring prokaryotes have an electron acceptor at the end of the chain that is different from O2.

A

True.

37
Q

Electron transfer from NADH to oxygen is an ______ reaction with a free-energy change of -53 kcal/mol.

A

Exergonic

38
Q

Instead of the energy for the electron transport chain being released and wasted in a single explosive step, what actually happens?

A

Electrons cascade down the chain from one carrier molecule to the next in a series of redox reactions, losing a small amount of energy with each step until they finally reach oxygen, the terminal electron acceptor, which has a a great affinity for electrons.

39
Q

What is the terminal electron acceptor and what makes it so good at its job?

A

Oxygen, and its electronegativity makes it more capable of oxidizing.

40
Q

Each “downhill” carrier is more electronegative than, and thus capable of oxidizing, its “uphill” neighbor, with oxygen at the bottom of the chain.

A

FREEBEE

41
Q

Put more simply, oxygen pulls electrons down the chain in an energy-yielding tumble analogous to gravity pulling objects downhill

A

FREEBEE

42
Q

What is the downhill route that most electrons travel in cellular respiration?

A

glucose –> NADH –> electron transport chain –> oxygen.

43
Q

The harvesting of energy from glucose by cellular respiration is a cumulative function of three metabolic stages. What are they?

A
  1. Glycolysis
  2. Pyruvate Oxidation and the Citric Acid Cycle
  3. Oxidative Phosphorylation: Electron Transport and Chemiosmosis
44
Q

What is glycolysis and where does it occur?

A

A process that begins the degradation process by breaking glucose into two molecules of a compound called pyruvate.
This occurs in the cytosol.

45
Q

What happens in pyruvate oxidation?

A

Pyruvate enters the mitochondrion and is oxidized to a compound called Acetyl CoA which then enters the citric acid cycle.

46
Q

What happens in the citric acid cycle?

A

The breakdown of glucose to CO2 is completed.

47
Q

Some of the steps of glycolysis and the citric acid cycle are redox reaction in which dehydrogenases transfer electrons from substrates to NAD+ forming NADH.

A

FREEBEE

48
Q

What happens in the third stage of respiration, the electron transport chain?

A

The electron transport chain accepts electrons (most often via NADH) from the breakdown products of the first two stages and passes these electrons from one molecule to another. At the end of the chain, the electrons are combined with molecule oxygen and hydrogen ions (H+) forming water.

49
Q

The energy released at each step of the chain is stored in a form the mitochondrion can use to make ATP from ADP. This mode of ATP synthesis is called _____ ______.

A

Oxidative Phosphorylation.

50
Q

What is the reasoning behind the name oxidative phosphorylation?

A

It makes sense because it is powered by the redox reaction of the electron transport chain.

51
Q

In eukaryotic cells, what is the location of electron transport and chemiosmosis?

A

The inner membrane of the mitochondrion

52
Q

What are the two processes the together constitute oxidative phosphorylation?

A

Electron transport and chemiosmosis.

53
Q

Oxidative phosphorylation accounts for __% of the ATP generated by respiration.

A

90

54
Q

A smaller amount of ATP is formed directly in a few reactions of glycolysis and the citric acid cycle by a mechanism called ____ _____ ______>

A

Substrate-level phosphorylation.

55
Q

How is the substrate-level type of ATP synthesis different than oxidative phosphorylation?

A

This mode of ATP synthesis occurs when an enzyme transfers a phosphate group from a substrate molecule to ADP, rather than adding an inorganic phosphate to ADP as in oxidative phosphorylation.
***NOTE: Substrate molecule here refers to an organic molecule generated as an intermediate during the catabolism of glucose.

56
Q

When you withdraw a relatively large sum of money from an ATM machine, it is not delivered to you in a single bill of larger denomination. Instead, a number of smaller denomination bills are dispensed that you can spend more easily. In cellular respiration, what is this analogous to?

A

ATP production. For each molecule of glucose degrade to carbon dioxide and water by respiration, the cell makes up about 32 molecules of ATP. Respiration cashes in the large denomination of energy banked in a singled molecule of glucose for the small change of many molecules of ATP, which is more practical for the cell to spend on its work.

57
Q

Compare and contrast aerobic and anaerobic respiration.

A

Both processes include glycolysis, the citric acid cycle, and oxidative phosphorylation. In aerobic respiration, the final electron acceptor is molecular oxygen (O2). In anaerobic respiration, the final electron acceptor is a different substance.

58
Q

If the following redox reactions occurred, what compound would be oxidized? Reduced?
C4H6O5 + NAD+ –> C4H4O5 + NADH + H+

A

C4H6O5 would be oxidized and NAD+ would be reduced.

59
Q

The world glycolysis literally means what?

A

Sugar splitting.

60
Q

What happens during glycolysis?

A

Glucose, a six carbon sugar, is split into two three-carbon sugars. These smaller sugars are then oxidized and their remaining atoms rearranged to form two molecules of pyruvate.
(Pyruvate is the ionized form of pyruvic acid)

61
Q

Glycolysis can be divided into two phases, what are they?

A

The energy investment phase and the energy payoff phase.

62
Q

During the energy investment phase, the cell _____ ATP.

A

spends

63
Q

During the energy payoff phase, the cell _____ ATP.

A

produces

64
Q

How is the investment of ATP during the energy investment phase of glycolysis repaid?

A

During the energy payoff phase when ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH by electrons released from the oxidation of glucose.

65
Q

What is the net energy yield from glycolysis per glucose molecule?

A

2 ATP

2 NADH

66
Q

How many steps are involved in the glycolytic pathway?

A

10.

67
Q

All of the carbon originally present in glucose is accounted for in the two molecules of pyruvate;
no carbon is released as CO2 during glycolysis.

A

FREEBEE

68
Q

T/F Glycolysis occurs whether or not O2 is present.

A

True

69
Q

What happens if O2 IS present during Glycolysis?

A

The chemical energy stored in pyruvate and NADH can be extracted by pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation.

70
Q

Remember: Glucose –> G3P –> Pyruvate

A

FREEBEE

71
Q

Glycolysis releases less than a quarter of the chemical energy in glucose that can be harvested by cells; most of the energy remains stockpiled in the two molecules of pyruvate. When O2 is present, the pyruvate in eukaryotic cells enters a mitochondrion, where the oxidation of glucose is completed.

A

FREEBEE

72
Q

Where is the oxidation of glucose completed in eukaryotic cells?

A

Mitochondrion.

73
Q

In aerobic respiring prokaryotic cells, where does the oxidation of glucose occur?

A

The cytosol

74
Q

Upon entering the mitochondrion via active transport, pyruvate is first converted to a compound called ____ ___.

A

acetyl coenzyme A or acetyl CoA

75
Q

The step that links glycolysis and the citric acid cycle is called _____ _____.

A

Pyruvate oxidation.

76
Q

Pyruvate Oxidation is carried out by a multienzyme complex that catalyzes three reactions. What are they?

A
  1. Pyruvate’s carboxyl group (_COO-), which is already fully oxidized and thus has little chemical energy, is removed and given off as a molecule of CO2.
    * **NOTE: this is the first step in which CO2 is released during respiration.
  2. The remaining two-carbon fragment is oxidized forming acetate. The extracted electrons are transferred to NAD+, storing energy in the form of NADH.
  3. CoA is attached via sulfur to the acetate, forming acetyl CoA.
77
Q

The reaction of acetyl CoA to yield lower-energy products is a highly ____ process.

A

Exergonic

Biology 1610 (4 decks)

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