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biology > topic 8 - metabolism > Flashcards

topic 8 - metabolism Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is metabolism?

A

sum total of all chemical reactions that occur within an organism in order to maintain life

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2
Q

how are metabolic processes controlled and coordinated?

A

series of enzyme catalyzed reactions

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3
Q

how are metabolic pathways organized and why are they important?

A

allow for greater level of regulation, organized into chains or cycles

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4
Q

what is activation energy? (EA)

A

the certain amount of energy needed for a chemical reaction to proceed

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5
Q

what do enzymes do to the rate of a biochemical reaction?

A

increase the rate of the reaction by lowering the Activation Energy required for the reaction

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6
Q

how do enzymes lower the EA?

A

bind to the substrate and destabilize the bonds of the substrate –> less energy is required to convert it into a product

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7
Q

what is an exergonic reaction?

A

reactants contain more energy than the products, free energy is released into the system

USUALLY CATABOLIC (energy is released from broken bonds)

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8
Q

what is an endergonic reaction?

A

reactants contain less energy than the products, free energy is lost to the system

usually anabolic, as energy is required to synthesize bonds

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9
Q

what is an enzyme inhibitor?

A

molecule that disrupts the normal reaction pathway between an enzyme and a substrate

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10
Q

what are the two types of enzyme inhibition?

A

competitive inhibition

noncompetitive inhibition

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11
Q

what is competitive inhibition

A

molecule other than the substrate binding to the enzyme’s active site

inhibitor is structurally and chemically similar to the substrate

prevents substrate binding, can be reduced by increasing substrate concentration

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12
Q

what is noncompetitive inhibition?

A

molecule binding to an allosteric site

causes a conformational change to the enzyme’s active site

substrate can no longer bind

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13
Q

why is enzyme inhibition necessary?

A

prevents the formation of a product

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14
Q

what is an example of a noncompetitive inhibitor?

A

cyanide

prevents ATP production via aerobic respiration

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15
Q

what is an example of a competitive inhibitor?

A

relenza

treats influenza

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16
Q

what is feedback inhibition? and what is another name for it?

A

end product inhibition
form of negative feedback by which metabolic pathways can be controlled

final product in a series of reactions inhibits an enzyme from an earlier step in the sequence (noncompetitive inhibition)

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17
Q

what is the purpose of feedback inhibition?

A

to ensure product levels are tightly regulated

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18
Q

what is an example of feedback inhibition and how does it work?

A

Inhibition of the pathway that converts threonine to isoleucine (essential amino acid)

steps:
ISOLEUCINE is synthesized in a 5 step process (using 5 enzymes)

threonine is converted into an intermediate compound by an enzyme

isoleucine can bind to an allosteric site on this enzyme

excess production of isoleucine inhibits further synthesis

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19
Q

how can the rate of a reaction be calculated?

A

rate of reaction (s^-1) = 1 / time taken (s)

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20
Q

what are three factors that affect enzyme activity?

A

pH
temperature
substrate concentration

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21
Q

rank the rate of reaction of uninhibited reactions, reactions with a competitive inhibitor, and reactions with a noncompetitive inhibitor from greatest to lowest

A

1/2 = uninhibited + competitive (V max is the same)
3. noncompetitive reaction

as enzyme inhibitors lower reaction rates by reducing levels of uninhibited enzymes

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22
Q

how are inhibitors used in medicine?

A

used to treat infectious diseases by targeting the enzymes involved in pathogenesis

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23
Q

what is rational drug design?

A

computer modelling techniques to invent a compound that functions as an inhibitor

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24
Q

OIL RIG meaning

A

Oxidation is Loss (of electrons)

Reduction is Gain (of electrons)

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25
Q

what is Adenosine triphosphate?

A

ATP, high energy molecule that functions as an immediate power source for cells

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26
Q

why is ATP readily reactive?

A

phosphorylation makes molecules less stable

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27
Q

how is energy released from ATP?

A

when ATP is hydrolyzed, the energy stored in the terminal phosphte bond is released

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28
Q

what are the two functions of ATP within the cell

A

energy currency of the cell (releases energy when hydrolyzed to ATP)

transfers phosphate group to other organic molecules, rendering them less stable and more reactive

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29
Q

how is ATP synthesized from ADP?

A 
using energy from:
solar energy (photosynthesis converts light energy into chemical energy)

oxidative processes (cell respiration breaks down organic molecules to release chemical energy)

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30
Q

what is cell respiration?

A

controlled release of energy from organic compounds to produce ATP

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31
Q

what is anaerobic respiration?

A

incomplete breakdown of organic molecules for a small yield of ATP (no oxygen)

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32
Q

what is aerobic respiration?

A

complete breakdown of organic molecules for a larger yield of ATP (oxygen is required)

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33
Q

why is the breakdown of organic molecules staggered?

A

activation energy is divided across several steps and released energy is not lost (transferred to activated carrier molecules)

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34
Q

how is the chemical energy from the breaking down of organic molecules due to cell respiration transferred?

A

redox reactions

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35
Q

why are carrier molecules called hydrogen carriers or electron carriers?

A

they gain electrons and protons (H+ ions)

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36
Q

what is the most common hydrogen carrier and what is it reduced to? INCLUDE FORMULA

A

NAD+, reduced to form NADH

NAD+ + 2H+ +2e- –> NADH + H+

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37
Q

what is a type of hydrogen carrier (other than NAD+)

A

FAD

38
Q

where is the electron transport chain?

A

cristae

39
Q

true or false: anaerobic respiration can generate ATP from hydrogen carriers

A

FALSE, only aerobic respiration can generate ATP from hydrogen carriers as process requires oxygen to function

40
Q

what is the first stage of aerobic respiration and what does it do?

A

link reaction, transports pyruvate into the mitochondria

41
Q

what happens during the link reaction?

A
  1. pyruvate transported from cytosol to mitochondrial matrix
  2. pyruvate –> CO2 through decarboxylation
  3. 2C molecule oxidized to produce a reduced carrier
  4. acetyl compound + coenzyme A combine and form acetyl CoA
42
Q

how many times does the link reaction occur per molecule of glucose and why

A

twice, glycolysis splits glucose into two pyruvate molecules

43
Q

what is the second stage of aerobic respiration? where does it occur?

A

The Krebs Cycle, matrix of the mitochondria

44
Q

what is another name for the Krebs Cycle?

A

citric acid cycle. tricarboxylic acid (TCA) cycle

45
Q

what happens during the Krebs Cycle?

A
  1. acetyl CoA combines with a 4C compound
  2. 6C compound is broken down into original 4C (2 molecules of CO2 produced)
  3. multiple oxidation reactions result in the reduction of hydrogen carriers
  4. small yield of ATP (one molecule) via substrate level phosphorylation
46
Q

how many times does the Krebs Cycle occur and why?

A

twice, link reaction produces two molecules of acetyl CoA (one for each pyruvate)

47
Q

what does the Krebs Cycle produce per molecule of glucose?

A

4 x CO2
2 x ATP
6 x NADH + H+
2 x FADH2

48
Q

what is the final stage of aerobic respiration? where does it occur?

A

electron transport chain, inner mitochondrial membrane

49
Q

what is the effect of the structure of the inner membrane

A

arranged into cristae (folds) to increase SA available for transport chain

50
Q

what are the steps of oxidative phosphorylation?

A
  1. proton pumps create an electrochemical gradient (proton motive force)
  2. ATP synthase uses the subsequent diffusion of protons (chemiosmosis) to synthesize ATP
  3. oxygen accepts electrons and protons to form water
51
Q

what happens during proton motive force?

A

carrier moelcules donate electrons to an electron transport chain located on the mitochondrial cristae

electrons lose energy as they are passed along the chain, used to pump H+ ions along the matrix

build up of protons in the intermembrane space creates an electrochemical gradient

52
Q

what is the transmembrane enzyme that returns protons to the matrix?

A

ATP synthase

53
Q

how are de-energized electrons removed from the electron transport chain? what is the byproduct?

A

final electron acceptor (oxygen)

water as a byproduct

54
Q

how many ATP molecules are made from reduced carriers?

A

32

55
Q

what is oxidative phosphorylation?

A

energy stored within the reduced hydrogen carriers is released to synthesize ATP

56
Q

give a quick summary of oxidative phosphorylation

A

Hydrogen carriers donate high energy electrons to the electron transport chain (located on the cristae)

As the electrons move through the chain they lose energy, which is transferred to the electron carriers within the chain

The electron carriers use this energy to pump hydrogen ions from the matrix and into the intermembrane space

The accumulation of H+ ions in the intermembrane space creates an electrochemical gradient (or a proton motive force)

H+ ions return to the matrix via the transmembrane enzyme ATP synthase (this diffusion of ions is called chemiosmosis)

As the ions pass through ATP synthase they trigger a phosphorylation reaction which produces ATP (from ADP + Pi)

The de-energised electrons are removed from the chain by oxygen, allowing new high energy electrons to enter the chain

Oxygen also binds matrix protons to form water – this maintains the hydrogen gradient by removing H+ ions from the matrix

57
Q

what is aerobic respiration

A

breakdown of glucose in the presence of oxygen to produce water and CO2

includes: glycolysis, link reaction, krebs cycle, electron transport chain

58
Q

what are the three MAIN stages of aerobic respiration? what are the products?

A

decarboylation: 6 CO2
oxidation: 10 NADH, 2 FADH2
phosphorylation: 36 ATP

59
Q

products of each type of reaction within aerobic respiration?

A

glycolysis: 2NADH, 2ATP (net, substrate level)

link reaction: 2CO2, 2NADH

krebs cycle: 4CO2, 6NADH, 2FADH2, 2 ATP (substrate level

electron transport chain: 32 ATP (oxidative)

60
Q

how many ATP are consumed in glycolysis?

A

2

61
Q

what is the first step in the controlled breakdown of carbohydrates and where does it occur?

A

glycolysis, cytosol

62
Q

what are the four key events of glycolysis?

A
  1. phosphorylation (hexose is phosphorylated by 2 molecules of ATP)
  2. lysis (6C is split into two 3C sugars)
  3. oxidation (hydrogen is removed from each of the 3C sugars to reduce NAD+ to NADH, two molecules of NADH are produced)
  4. ATP formation (substrate level phosphorylation)
63
Q

is glycolysis aerobic or anaerobic

A

anaerobic

64
Q

what is fermentation?

A

after glycolysis, if oxygen is not present, the pyruvate is not broken down further and no more ATP is produced (incomplete oxidation)

converted into lactic acid (animals) or ethanol and CO2 (plants and yeast)

65
Q

is fermentation reversible?

A

yes

66
Q

what are mitochondria

A

powerhouse of the cell, synthesize lareg amounts of ATP via aerobic respiration

67
Q

how is the structure of a mitochondrion adapted to the function it performs?

A

The inner membrane is folded into cristae to increase the surface area available for the electron transport chain

The intermembrane space is very small (maximises the electrochemical gradient that results from proton accumulation)

The mitochondrial matrix contains suitable enzymes and an appropriate pH for the Krebs cycle to occur

The outer membrane contains the necessary transport proteins for shuttling pyruvate into the mitochondria (link reaction)

68
Q

what is electron tomography?

A

Electron tomography is a technique by which a 3-dimensional image of an internal cellular structure can be generated

Samples are repeatedly imaged at different angles (using a transmission electron microscope) and the images are compiled

69
Q

what is photosynthesis?

A

process by which cells synthesize organic molecules from inorganic molecules in the presence of sunlight

70
Q

what is an example of a photosynthetic pigment?

A

chlorophyll

71
Q

what does the conversion of light energy into chemical energy require

A

energy transfer molecules (electron carriers) + ATP

72
Q

how is the structure of a chloroplast adapted to the function it performs?

A

Granum are made up of stacks of thylakoids to increase the surface area available for the electron transport chain

The thylakoid lumen is very small (maximises the electrochemical gradient that results from proton accumulation)

The stroma contains suitable enzymes and an appropriate pH for the Calvin cycle to occur (light independent reactions)

73
Q

what are the two stages of photosynthesis?

A

light dependent reaction

light independent reaction

74
Q

steps of light dependent reactions (IN THREE SIMPLE STEPS)

A
  1. light is absorbed by chlorophyll (releases energized electrons used to produce ATP)
  2. electrons are donated to carriers
  3. electrons lost from chlorophyll are replaced by water, themn split to produce O and H
75
Q

where do light independent reactions occur?

A

fluid filled interior of the chloroplast called the stroma

76
Q

where do light dependent reactions occur

A

intermembrane space of membranous discs called thylakoids

77
Q

steps of light independent reactions (general, 2 steps)

A
  1. ATP + hydrogen/electrons are transferred to stroma

2. hydrogen/electrons combine with CO2 to form complex organic compounds (energy comes from ATP)

78
Q

what happens in non-cyclic photophosphorylation?

A
  1. chlorophyll in PSI and PSII absorb light, triggering the release of energized electrons
  2. electrons from PSI reduce NADP
  3. electrons from PSII move through an ETC before replacing the electrons from PS I
  4. ETC produces ATP (photophosphorylation)
  5. electrons lost from PS II are replaced by water
79
Q

what is photoactivation

A

chlorophyll in PS I and PSII absorb light which triggers the release of energized electrons

80
Q

what happens in cyclic photophosphorylation?

A
  1. only chlorophyll in PS I are activated by light
  2. electrons move through ETC before returning to their original location
  3. ETC produces ATP
  4. does not produce NADPH
81
Q

can cyclic photophosphorylation produce organic molecules

A

no

82
Q

maximal absorption wavelength of PS I? what about PS II?

A

PS I = 700 nm

PS II = 680 nm

83
Q

what is photophosphorylation

A

the production of ATP by light dependent reactions

84
Q

how are cyclic and noncyclic photophosphorylation different?

A 
cyclic:
only PS I
water is not required
oxygen is not evolved
NADPH is not synthesized 
produces ADDITIONAL ATP
noncyclic
PS I and PS II
photolysis of water is required
oxygen is evolved
NADPH is synthesized
products can be used for light independent rxns
85
Q

what are the steps of light independent reactions?

A
  1. carbon fixation
  2. reduction of GP
  3. regeneration of RuBP
86
Q

what are light independent reactions known as?

A

calvin cycle

87
Q

what happens in carbon fixation?

A
  • Rubisco catalyzes the carboxylation of RuBP (attaches CO2 molecule)
  • 6C compound breaks into two 3C copmounds (glycerate-3-phosphate, GP)
  • one cycle = 3 molecules of RuBP + 3 molecules of CO2 –> 6 molecules of GP
88
Q

what happens during the reduction of GP?

A
  • GP is phosphorylated by ATP and reduced by NADPH
  • GP molecule is converted into TP (triose phosphate)
  • one cycle requires six of each molecule
89
Q

what happens during the regeneration of RuBP?

A
  • one molecule of TP forms half a sugar
  • remaining TP molecules reform RuBP
  • regeneration of RuBP requires energy derived from the hydrolysis of ATP
90
Q

what was the lollipop experiment

A

radioactive C-14 was added to a lollipop apparatus with green algae

different carbon compounds were identified using chromatography and autoradiography

Calvin Cycle was shown

91
Q

what are chloroplasts

A

solar energy plants of a cell (convert light energy into chemical energy)

92
Q

what type of issue possesses chloroplasts

A

photosynthetic tissue (leaves, not roots of plants)

biology (11 decks)

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