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A2 Biology > Respiration > Flashcards

Respiration Flashcards

1
Q

Respiration produces what?

A

ATP

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2
Q

What are the 2 types of respiration?

A

Aerobic and anaerobic

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3
Q

What is aerobic respiration?

A

requires oxygen

- produces carbon dioxide, water and much ATP

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4
Q

What is anaerobic respiration?

A
  • takes place in absence of oxygen and produces lactate (in animals) or ethanol and CO2 (in plant and fungi) but only little ATP (in both cases)
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5
Q

Aerobic respiration can be divided into what four stages?

A
  • glycolysis
  • link reaction
  • krebs cycle
  • oxidative phosphorylation
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6
Q

Glycolysis is the initial stage of what?

A

aerobic and anaerobic respiration

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7
Q

What takes place during the process of cellular respiration?

A

formation of ATP from the breakdown of glucose

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8
Q

Where does glycolysis occur?

And briefly state what happens in it

A
  • cytoplasm of all living cells

- a hexose (6C) sugar (usually glucose) is split into 2 molecules of 3-carbon —- PYRUVATE

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9
Q

Describe glycolysis process

A
  1. Glucose is double phosphorylated via 2 ATP molecules
    - becomes glucose phospahte (6C) (after first phosphorylation)
    - becomes hexose biphosphate (6C)
  2. The double phosphorylated molecule (Hexose biphosphate) splits into 2 TP (triosephosphate) molecules
  3. Each TP (3C) oxidised - loses H and transferred to hydrogen-carrier (NAD) to form 2 reduced NAD
  4. enzyme-controlled reactions convert each TP into pyruvate (3C)
    In process, 2 molecules of ATP are regenerated from ADP
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10
Q

In anaerobic respiration pyruvate is converted into what? and why does this have to happen?

A

lactate or ethanol

  • this has to happen to re-oxidise the NAD so that it can be re-used in glycolysis
  • small amount of ATP will still be produced
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11
Q

Respiration equation

A

C6H12O6 + 6O2 –> (equil..) 6H2O + 6CO2 (+energy)

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12
Q

Energy yields from glycolysis

A
  • 2 molecules of ATP (four produced but 2 used in initial phosphorylation of gluocse and so net increase is 2)
  • 2 molecules of reduced NAD
  • 2 molecules of pyruvate
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13
Q

Why is glycolysis indirect evidence for evolution?

A

because it’s a universal feature of every living organism

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14
Q

Briefly - what happens in the link reaction?

A
  • the 3-carbon pyruvate molecules enter into series of reactions which lead to formation of acetylcoenzyme A, a 2-carbon molecule
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15
Q

Reduced NAD also written as?

A

NADH

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16
Q

Is Glycolysis aerobic or anaerobic?

A

doesn’t need oxygen - so it’s an anaerobic process

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17
Q

2 main stages of glycolysis and describe?

A

phosphorylation + oxidation
- ATP used to phosphorylate glucose to triose phosphate (TP)
- TP oxidised, releasing ATP
Overall net gain: 2 ATP and 2 reduced NADand 2 pyruvate molecules

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18
Q

Similarities between aerobic and anaerobic respiration

A

Both produce ATP (anaerobic much less though)

Both start with glycolysis ( but differ afterwards)

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19
Q

Briefly state what happens in Link reaction

A
  • link reaction converts pyruvate to Acetyl Coenzyme A
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20
Q

Where does link reaction occur?

A

mitochondrial matrix

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21
Q

Describe Link reaction process

A

1 pyruvate (3C) is decarboxyled (one C atom removed from pyruvate in the form of CO2)
2 pyruvate oxidised (dehydrogenated) to form acetate(2C) and NAD reduced to form reduced NAD
3 Acetate combined with Coenzyme A (CoA) to form acetyl Coenzyme A (Acetyl CoA)
4 allowing it to enter krebs cycle (NO ATP PRODUCED)

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22
Q

Overall equation of link reaction

A

pyruvate + NAD + CoA –> acetyl CoA + reduced NAD + CO2

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23
Q

How many times does link reaction and krebs cycle occur and why?

A

occurs twice for every glucose molecule because 2 pyruvate molecules are produced in glycolysis

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24
Q

Products from link reaction for each glucose molecule ?

A
  • 2 molecules of acetyl CoA go into krebs cycle
  • 2 CO2 molecules released as waste product of respiration
  • 2 molecules of reduced NAD formed and go into oxidative phosphorylation
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25
Q

Briefly describe what happens in Krebs cycle?

A
  • krebs cycle produces reduced coenzymes and ATP
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26
Q

Krebs cycle takes place where?

A

matrix of mitochondria

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27
Q

Krebs cycle happens how often?

A

once for every pyruvate molecule so twice for every glucose molecule

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28
Q

What are coenzymes?

A
  • not enzymes

- molecules that some enzymes require to function

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29
Q

Role of coenzymes in photosynthesis and respiration?

A

-carry H atoms from 1 molecule to another

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30
Q

Examples of Coenzymes

A

NAD - important throughout respiration
FAD - important in krebs cycle
NADP - important in photosynthesis

31
Q

In respiration what is the most important carrier and why?

A
  • NAD
  • works with dehydrogenase enzymes that catalyse removal of H atoms from substrates and transfer them to other molecules involved in oxidative phosphorylation
32
Q

Describe the four important roles of the Krebs cycle in cells of organisms

A

1 breaks down macromolecules into smaller ones (pyruvate into CO2)
2 produces H atoms carried by NAD to electron transfer chain and provide energy for oxidative phosphorylation - leads to production of ATP & provides metabolic energy for cell
3 regenerates 4-carbon molecule that combines with acetyl CoA, which would accumulate otherwise
- source of intermediate compounds used by cells in manafacture of other important substances like fatty acids, AAs and chlorophyll

33
Q

Describe the Krebs Cycle Process

A

1 - CoA removed from acetyl CoA (2C) allowing acetyl to combine with oxaloacetate (4C) to form citrate (citric acid) (6C)
- CoA goes back to link reaction to be used again

2 - 6C citrate molecule converted to 5C molecule

  • decarboxylation occurs, CO2 (1C) removed
  • dehydrogenation, H removed to reduce NAD to NADH

3 5C molecule converted to a 4C molecule (OXALOACETATE)

  • decarboxylation and dehydrogenation occur, producing 1 molecule of reduced FAD and 2 of reduced NAD
  • ATP produced by substrate-level phosphorylation
  • citrate now converted to oxaloacetate (4C) - marks end of krebs cycle
34
Q

What is substrate-level phosphorylation?

Occurs in Krebs Cycle

A

-direct transfer of phosphate group from 1 molecule to another

35
Q

What things generally happens to products of krebs cycle?

A
  • some reused, some released and others used for next stage of respiration
36
Q

Products of 1 krebs cycle? (so double these for 1 glucose molecule)

A 
3 x reduced NAD
1 x reduced FAD
2 x CO2
1 x ATP
oxaloacetate (4 Carbon molecule)
37
Q

Where does coenzyme A go after 1 krebs cycle?

A

reused in next link reaction

38
Q

where does oxaloacetate (4C sugar) go after 1 krebs cycle?

A

regenerated for use in next krebs cycle

39
Q

where does CO2 (x2) go after 1 krebs cycle?

A

released as waste product

40
Q

what is ATP used for after 1 krebs cycle?

A

used for energy

41
Q

where does FAD (x1) and reduced NAD (x3) go after 1 krebs cycle?

A

to oxidative phosphorylation

42
Q

Aim of oxidative phosphorylation

A

to make as much ATP as possible

43
Q

What was the point of steps previous to oxidative phosphorylation ?

A
  • to make reduced NAD and reduced FAD for final stage
44
Q

Briefly describe what happens in oxidative phosphorylation?

A

process where energy carried by electrons, from reduced coenzymes (reduced NAD and FAD) is used to make ATP
- involves electron transport chain and chemiosmosis

45
Q

Describe oxidative phosphorylation process (or ETC)

A

1 NADH and FADH become oxidised (H atom splits) releasing H+ (protons) and e- (electrons)
2 electrons enter ETC, moving through electron carriers, losing energy at each carrier. Energy released from this used to move H+ (protons) against conc gradient - from mitochondrial matrix to intermembrane space
3 conc of protons now higher in intermembrane space than mitochondrial matrix - establishing electrochemical gradient (conc of gradient ions)
4 H+ (protons) move down electrochemical gradient (across inter mitochondrial membrane & into mitochondrial matrix) through ATP synthase, catalysing reaction : ADP + Pi –> ATP
5 in mitochondrial matrix (at end of transport chain) oxygen (from blood) acts as a final electron acceptor combining with H+ & electrons to form water
1/2O2 + 2e- + 2H+ —> H2O

46
Q

How does flow of protons in oxidative phosphorylation lead to ATP synthesis?

A
  • flow of H+ (protons) causes a change of shape in protein ATP synthase and leads to ATP synthesis
47
Q

What is chemiosmosis?

A

movement of ions across semi permeable membrane down their electrochemical gradient
e.g. process of ATP production driven by movement of H+ ions in oxidative phosphorylation

48
Q

How does pyruvate enter mitochondrial matrix after glycolysis?

A

active transport

49
Q

In anaerobic respiration pyruvate is converted to what? (refer to notes for equations)

A

ethanol (in plants + yeast) - alcoholic fermentation
lactate (in animal cells & some bacteria) - lactate fermentation
using reduced NAD

50
Q

Benefit of production of ethanol or lactate for biological processes?

A

oxidised NAD is regenerated (in anaerobic respiration) - meaning glycolysis can continue when not much O2 around
- so small amount of ATP still produced to keep some biological processes going

51
Q

Name two respiratory substrates apart from sugars

A

Lipids

Proteins

52
Q

Describe the respiration of lipids

A
  • lipids hydrolysed to glycerol+ fatty acids
  • glycerol phosphorylated & converted to triose phosphate
  • TP enters glycolysis - krebs pathway
  • fatty acid broken down into 2C fragments of carbohydrates which are converted to acetyl coenzyme A - then enters krebs cycle.
53
Q

Why do lipids release x2 energy of same mass of carbohydrate?

A

oxidation of lipids produces 2C fragments of carbohydrates & many H atoms

  • H atoms used to produce ATP during oxidative phosphorylation
  • this is why lipids release double the energy of the same mass of carbohydrate
54
Q

Describe the respiration of proteins

A
  • first hydrolysed to AAs - amino group removed (deamination) before entering respiatory pathways (depending on how many C atoms they contain)
  • 3C compounds converted to pyruvate
  • 4C and 5C converted to intermediates in krebs cycle
55
Q

Briefly describe why aerobic respiration can’t take place in the presence of no oxygen?

A
  • neither krebs or ETC can continue because all FAD & NAD will soon be reduced
  • no FAD or NAD available to take up H+ produced during krebs so enzymes stop working
  • leaves only anaerobic process glycolysis as (potential) source of ATP
56
Q

For glycolysis to continue, what must happen?

A
  • its products (pyruvate & hydrogen) must constantly be removed - H must be removed from NADH to regenerate NAD
57
Q

In anaerobic respiration, For gylcolysis to continue, its products must be removed, what will happen if this isn’t the case?

A
  • already tiny supply of NAD in cells will entirely be converted to reduced NAD, leaving no NAD to take up newly produced H from glycolysis so gylcolysis stops
58
Q

How is replenishment of NAD is achieved in glycolysis?

A
  • by pyruvate molecules from glycolysis accepting hydrogen from reduced NAD
  • oxidised NAD produced can then be used in further gylolysis
59
Q

List reasons why aerobic can’t take place without oxygen?

A

1 O2 can’t act as final electron acceptor
2 no/fewer electrons move through ETC
3 H+ not moved against conc gradient (since no energy provided by movement of electrons)
4 No ATP made in oxidative phosphorylation
5 NADH & FADH not oxidised back into FAD & NAD
- therefore NAD & FAD not available to oxidise reactions in krebs cycle
- also link reaction stops because it relies on reduction of NAD to oxidise pyruvate
in absence of O2 very little ATP made.

60
Q

In plants (and microorganisms e.g. yeast) pyruvate is converted to what?

A

ethanol and carbon dioxide

glucose —-> ethanol + carbon dioxide

61
Q

In animals, pyruvate is converted to what?

A

lactate

glucose —-> lactate

62
Q

Why can glycolysis continue in the absence of oxygen?

A
  • allows NADH to be oxidised into NAD

- however net yield of ATP is much less than in aerobic respiration

63
Q

Describe what happens to pyruvate after formed in anaerobic respiration (for fungi & plants)

A

(3C) pyruvate reduced to (2C)ethanol, CO2 released
while NADH is oxidised to NAD
and NAD recycled back to glycolysis

64
Q

Describe what happens to pyruvate after formed in anaerobic respiration (in animals)

A

(3C) pyruvate reduced to (3C)lactate while NADH is simultaneously reduced to lactate
and NAD recycled back to gylcoysis

65
Q

Summary equation of anaerobic respiration in plants

A

pyruvate + reduced NAD —> ethanol + carbon dioxide + oxidised NAD

66
Q

summary equation of anaerobic respiration in animals

A

pyruvate + reduced NAD —> lactate + oxidised NAD

67
Q

Describe what happens during streneous exercise?

A
  • lacatate production in muscles causing muscle cramps
  • oxygen used more rapidly than it’s supplied so oxygen debt occurs

additional info:
when O2 returns it will break down lactate into CO2 and water

68
Q

Why are enzymes affected by lactate in body?

A

causes PH change which affects enzymes

69
Q

give two ways in which aerobic respiration in yeast is similar to anaerobic respiration of glucose in muscle cell

A
  • pyruvate is reduced

- reduced NAD is oxdidised to NAD which are both recycled to glycolysis

70
Q

give two ways in which aerobic respiration in yeast is different to anaerobic respiration of glucose in muscle cell

A
  • production of ethanol as opposed to lactate

- CO2 released by yeast but not muscle cell

71
Q

Describe the energy yields from aerobic and anaerobic respiration

A

substrate-level phosphorylation in glycolysis and krebs cycle: direct transfer of phosphate from a respiratory intermediate to ADP to produce ATP

oxidative phosphorylation in ETC: indirect linking of energy from phosphate to ADP to produce ATP involving energy from H atoms that are carried on NAD and FAD
(cells produce most of ATP this way)

72
Q

Apart from respiration, give three uses of ATP in a liver cell

A

Active transport
Phagocytosis
Mitosis
Synthesis of protein

73
Q

Describe the part played by the inner membrane of a mitochondrion in producing ATP.

A

Electrons transferred down electron transport chain;
Provide energy to take protons into space between membranes.
Protons/H+ pass back through membrane into matrix
Energy used to combine ADP and phosphate/to produce ATP

74
Q

Give two advantages of ATP as an energy-storage molecule within a cell

A

Cannot pass out of cell
Quickly/easily broken down
Stores / releases small amounts of energy

A2 Biology (13 decks)

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