Chapter 9 (Notes) Flashcards Preview

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Flashcards in Chapter 9 (Notes) Deck (104):
1

Living cells require energy from

outside sources.

Some animals, such as the chimpanzee, obtain energy be eating plants, and some animals feed on other organisms that eat plants.

2

Energy flows into an ecosystem as

sunlight and leaves as heat.

3

Photosynthesis generates O2 and organic molecules, which

are used in cellular respiration.

4

Cells use chemical energy stored in organic molecules to

regenerate ATP, which powers work.

5

Several processes are central to

cellular respiration and related pathways.

6

The breakdown of organic molecules is

exergonic.

7

Three ways cells make ATP

Fermentation
Aerobic respiration
Anaerobic respiration

8

Fermentation is a

partial degradation of sugars that occurs without O2

(((do this as last resort???)))

9

Aerobic respiration

consumes organic molecules and O2 and yields ATP
(tons of ATP) (need a lot of oxygen)

10

Anaerobic respiration

is similar to aerobic respiration but consumes compounds other than O2.

(doesn't need O2 but makes tons of ATP?)

11

Cellular respiration includes both

aerobic and anaerobic respiration but is often used to refer to aerobic respiration.

12

Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to

trace cellular respiration with the sugar glucose.

13

Chemical equation for Cellular Respiration

C6H12O6 + 6 O2 ---> 6 CO2 + 6 H2O + Energy (ATP + heat)

1 glucose + 6 Oxygen --> 6 molecules of Carbon Dioxide + 6 Water molecules + Energy in the two forms of ATP and Heat.

((2 things in and three things out))


(((glucose is oxidized. Oxygen is reduced(gains electrons))))

14

The transfer of electrons during chemical reactions releases

energy stored in organic molecules.

This released energy is ultimately used to synthesize ATP.

15

Chemical reactions that transfer electrons between reactants are called

oxidation-reduction reactions, or redox reactions.

16

In oxidation,

a substance loses electrons, or is oxidized.

17

In reduction,

a substance gains electrons, or is reduced (the amount of positive charge is reduced)

18

LEO GER

(LEO (the lion) (says) GER)

Oxidation:
L- Loses
E- Electrons
O- Oxidized

Reduction:
G-Gains
E- Electrons
R- Reduced

19

The electron donor is called the

reducing agent.

20

The electron receptor is called the

oxidizing agent.

21

Some redox reactions do not transfer electrons but

change the electron sharing in covalent bonds.

An example is the reaction between methane and O2.
-One way to follow electron movements is to watch the hydrogens.

***Look for hydrogens.
***Things that have hydrogens have a lot of electrons.

22

During cellular respiration, the fuel (such as glucose) is

oxidized, and O2 is reduced.

23

Cellular respiration allows us to break off

energy into small amounts.

((???))

24

Organic molecules that have lots of H (hydrogen) are good fuels because

they have e- (electrons) that can be transferred to oxygen.

This must happen stepwise.
Glucose burning releases 686 kcal/mol glucose.

25

In cellular respiration, glucose and other organic molecules ae

broken down in a series of steps.

26

Electrons from organic compounds are usually first transferred to

NAD+, a coenzyme.

27

As an electron acceptor, NAD+ functions as an

oxidizing agent during cellular respiration.

28

Each NADH (the reduced form of NAD+) represents

stored energy that is tapped to synthesize ATP.

29

NADH passes the electrons to the

electron transport chain.

30

Unlike an uncontrolled reaction, the electron transport chain passes electrons in a

series of steps instead of one explosive reaction.

31

O2 (oxygen) pulls electrons down the electron transport chain in an

energy-yielding tumble.

The energy yielded is used to regenerate ATP.

Food >> NADH >> Electron Transport Chain >> Oxygen (((>> water)))

Most electrons follow this "downhill route" ^^

32

Harvesting of energy from glucose has three stages

1. Glycolysis
2. The Citric Acid Cycle
3. Oxidative Phosphorylation

33

Glycolysis

-breaks down glucose into two molecules of pyruvate.

-Location it occurs: Cytoplasm
-How ATP is made: Substrate-Level Phosphorylation (SLP)

34

The Citric Acid Cycle
(Pyruvate Oxidation)

completes the breakdown of glucose.

-Location it occurs: Matrix Mitochondria
-How ATP is made: Substrate-Level Phosphorylation (SLP)

35

Oxidative Phosphorylation

accounts for most of the ATP synthesis.

-Location it occurs: Inner Membrane of Mitochondria
-How ATP is made: Oxidative Phosphorylation (OP)

36

The process that generates most of the ATP is called

oxidative phosphorylation because it is powered by redox reactions.

37

Oxidative phosphorylation accounts for almost 90% of the

ATP generated by cellular respiration.

38

A smaller amount of ATP is formed in glycolysis and the citric acid cycle by

substrate-level phosphorylation.

39

For each molecule degraded to CO2 and water by respiration, the cell makes up to

32 molecules of ATP.

40

Glycolysis ("splitting of sugar") breaks down glucose into

two molecules of pyruvate.

41

Glycolysis occurs in the cytoplasm and has two major phases

-energy investment phase
-energy payoff phase

42

Glycolysis occurs whether or not

O2 is present.

43

Glycolysis harvests chemical energy by

oxidizing glucose to pyruvate.

44

After pyruvate is oxidized, the citric acid cycle completes the

energy-yielding oxidation of organic molecules.

45

In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the

oxidation of glucose is completed.

46

Before the citric acid cycle can being, pyruvate must be converted to

acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle.

This step is carried out by a multienzyme complex that catalyses three reactions.

47

The citric acid cycle, also called the Krebs cycle, completes the

breakdown of pyruvate to CO2.

48

The citric acid cycle oxidizes organic fuel derived from

pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn.
-2 turns per 1 original glucose molecule.

49

The acetyl group of acetyl CoA joins the citric acid cycle by

combining with oxaloacetate, forming citrate.

50

The next seven steps in the citric acid cycle decompose the citrate back to

oxaloacetate, making the process a cycle.

51

The NADH and FADH2 produced by the citric acid cycle relay electrons extracted from

the food to the electron transport chain.

52

During oxidative phosphorylation,

chemiosmosis couples electron transport to ATP synthesis.

53

Following glycolysis and the citric acid cycle, NADH and FADH2 account for

most of the energy extracted from food.

54

These two electron carriers (NADH and FADH2) donate electrons to the electron transport chain, which

powers ATP synthesis via oxidative phosphorylation.

55

The electron transport chain is in the

inner membrane (cristae) of the mitochondrion.

56

Most of the chain's (electron transport chain) components are proteins, which

exist in multiprotein complexes.

57

The carriers (NADH and FADH2??) alternate reduced and oxidized states as they

accept and donate electrons.

58

Electrons drop in free energy as they go

down the chain and are finally passed to O2, forming H2O.

59

The first proteins have lower affinity for electrons (less electronegative)

the final electron acceptor O2 is very electronegative.

60

Electrons are transferred from NADH or FADH2 to the

electron transport chain.

61

Electrons are passed through a number of proteins including

cytochromes (each with an iron atom) to O2.

62

The electron transport chain generates

no ATP directly.

63

The electron transport chain breaks the large free-energy drop from food to O2 into

smaller steps that release energy in manageable amounts.

64

Chemiosmosis

the energy-coupling mechanism

65

Electron transfer in the electron transport chain causes proteins to

pump H+ from the mitochondrial matrix to the intermembrane space.

H+ then moves back across the membrane, passing through the proton, ATP synthase.

66

ATP synthase uses the

exergonic glow of H+ to drive phosphorylation of ATP.

67

This is an example of chemiosmosis, the use of

energy in a H+ gradient to drive cellular work.

68

The energy stored in a H+ gradient across a membrane couples the

redox reactions of the electron transport chain to ATP synthesis.

69

The H+ gradient is referred to as a

proton-motive force, emphasizing its capacity to do work.

70

During cellular respiration, most energy flows in this sequence

glucose --> NADH --> electron transport chain --> proton-motive force --> ATP

71

About 34% of the energy in a glucose molecule is transferred to

ATP during cellular respiration, making about 32 ATP.

Several reasons why the number of ATP is not known exactly.

72

Fermentation and Anaerobic respiration enable cells to

produce ATP without the use of oxygen.

73

Most cellular respiration require

O2 to produce ATP.

74

Without O2 as a final electron acceptor,

the electron transport chain will cease to operate.

In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP.

75

Anaerobic respiration uses an

electron transport chain with a final electron acceptor other than O2, for example sulfate.

76

Fermentation uses substrate-level phosphorylation instead of an

electron transport chain to generate ATP.

77

Fermentation consists of

glycolysis plus reactions that generate NAD+, which can be reused by glycolysis.

78

Two common types of Fermentation are

alcohol fermentation
and
lactic acid fermentation.

79

In alcohol fermentation, pyruvate is converted to

ethanol in two steps, with the first releasing CO2.

80

Alcohol fermentation by yeast is used in

brewing, winemaking, and baking.

2 Ethanol, 2 CO2, 2 ATP and 2NAD+ are the products generated from 1 glucose.

81

In lactic acid fermentation, pyruvate is

reduced to NADH, forming lactate as an end product, with no release of CO2.

82

Lactic acid fermentation by some fungi and bacteria is used to

make cheese and yogurt.

83

Human muscle cells use lactic acid fermentation to

generate ATP when O2 is scarce.

1 glucose makes 2ATP, 2 lactate, and 2 NAD+

84

Fermentation, Anaerobic respiration, and Aerobic respiration all use glycolysis (net ATP=2) to oxidize

glucose and harvest chemical energy of food.

85

In fermentation, Anaerobic respiration, and Aerobic respiration, NAD+ is

the oxidizing agent that accepts electrons during glycolysis.

86

The processes have different final electron acceptors:

an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration.

87

Cellular respiration produces 32 ATP per glucose molecule; and

fermentation produces 2 ATP per glucose molecule.

88

Obligate anaerobes carry out

fermentation or anaerobic respiration and cannot survive in the presence of O2.

89

Yeast and many bacteria are facultative anaerobes, meaning that

they can survive using either fermentation or cellular respiration.

90

In a facultative anaerobe, pyruvate is the

fork in the metabolic road that leads to two alternative catabolic routes.

91

Ancient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphere.

Very little O2 was available in the atmosphere until about 2.7 billion years ago, so early prokaryotes likely used only glycolysis to generate ATP.

92

Glycolysis is a very

ancient process.

93

Glycolysis and the Citric Acid Cycle connect to

many other metabolic pathways.

94

Glycolysis and the citric acid cycle are major intersections to

various catabolic and anabolic pathways.

95

Catabolic pathways funnel electrons from many kinds of organic molecules into

cellular respiration.

96

Glycolysis accepts a

wide range of carbohydrates.

97

Proteins must be digested to amino acids; amino groups can feed

glycolysis or the citric acid cycle.

98

Fats are digested to

glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA)

99

Fatty acids are broken down by

beta oxidation and yield acetyl CoA.

100

An oxidized gram of fat produces more than

twice as much ATP as an oxidized gram of carbohydrate.

101

The body uses small molecules to

build other substances.
We don't just eat to get ATP -- portions of our diet go to building up molecules.

These small molecules may come directly from food, from glycolysis, or from the citric acid cycle.

102

Feedback Inhibition is the

most common mechanism for control.
The end product inhibits an enzyme used in the synthesis pathway.

103

If ATP concentration begins to drop, respiration speeds up;

when there is plenty of ATP, respiration slows down.

104

Control of catabolism is based mainly on

regulating the activity of enzymes at strategic points in the catabolic pathway.