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a level biology > Respiration > Flashcards

Respiration Flashcards

1
Q

what is the mitochondria?

A

the power house of the cell, found in all cell types, high numbers in cells with high energy demands

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2
Q

what are the four stages of respiration?

A

glycolysis, link reaction, krebs cycle and oxidative phosphorylation

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3
Q

where does glycolysis take place?

A

in the cytoplasm surrounding the mitochondria

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4
Q

where does the link reaction take place?

A

in the matrix

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5
Q

where does the Krebs cycle take place?

A

in the matrix

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6
Q

where does oxidative phosphorylation take place?

A

in the crista

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7
Q

what is glycolysis?

A

splitting 6C glucose into 2x 3C pyruvates

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8
Q

what type of respiration is glycolysis involved in?

A

aerobic and anaerobic

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9
Q

what is the role of hexokinases?

A

enzymes that carry out the phosphorylation of glucose, forming glucose 6-phospate (G6P), this uses ATP but maintains the concentration gradient for transport of glucose into the cell and stops glucose from leaking out as there is no channel proteins for G6P and it is a charged molecule

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10
Q

what is respiration?

A

a series of reactions in which energy is transferred from organic compounds, such as carbohydrates, to the temporary energy store ATP

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11
Q

what are the two types of respiration?

A

aerobic and anaerobic

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12
Q

what is the overall formula for aerobic respiration?

A

C6H12O6 + 6O2 -> 6CO2 + 6H2O

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13
Q

what are the structural features of the mitochondria?

A

outer membrane, inner membrane, crista, DNA, ribosomes, matrix

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14
Q

what is the first step of glycolysis?

A

activation of glucose by phosphorylation, before splitting, glucose is made more reactive by adding two phosphate molecules, these phosphates are from the hydrolysis of ATP to ADP, which provides the energy to activate glucose and lowers the activation energy needed for the following enzyme controlled reactions

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15
Q

what is the second step of glycolysis?

A

splitting of phosphorylated glucose, glucose -> 2x 3C triose phosphate (TP)

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16
Q

what is the third step of glycolysis?

A

oxidation of TP to pyruvate, hydrogen removed from each TP, hydrogen transferred to NAD+ (hydrogen carrier) forming reduced NAD

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17
Q

what is the fourth step in glycolysis?

A

production of ATP and reduced NAD (NADH), enzymes convert 3C TP to 3C pyruvate, 2 ATPs generated from ADP (net - four made but two spent in the phosphorylation of glucose)

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18
Q

what is the overall net yield of glycolysis?

A

2 ATP (small yield but fast), 2 NADH, 2 pyruvate

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19
Q

is glycolysis aerobic or anaerobic?

A

anaerobic - does not require oxygen

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20
Q

how does glycolysis provide evidence for evolution?

A

carried out by all living things, common ancestry

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21
Q

what are coenzymes?

A

complex organic molecules that are used by enzymes to accept or donate molecules involved in a reaction, often referred to as helper molecules as they carry chemical groups or ions

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22
Q

what is an electron?

A

a negatively charged particle surrounding the nucleus of an atom

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23
Q

what is a proton?

A

a positively charged particle found in the nucleus of an atom

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24
Q

what is the link reaction?

A

converts 3C pyruvate into CO2 and 2C acetlycoenzyme a, takes place in mitochondria matrix, oxidises pyruvate after it is actively transported into the mitochondrial matrix

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25
Q

what is the krebs cycle?

A

acetylcoenzyme a goes through redox reactions that produces ATP and reduced NAD and redced FAD

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26
Q

what happens to pyruvate from glycolysis in aerobic respiration?

A

if oxygen is present 3C pyruvate (C3H4O3) passes into mitochondria, here it is completely oxidised forming CO2, the second stage of aerobic respiration is the link reaction

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27
Q

what happens in the link reaction?

A

pyruvate dehydrogenated and decarboxylated, reducing NAD to NADH, and forming acetate, coenzyme a is combined with acetate to form acetyl coenzyme a, the products (NADH and 2C Acetyl CoA) go to krebs cycle and oxidative phosphorylation

28
Q

why does the link reaction occur twice for every glucose molecule?

A

two pyruvate made for every glucose molecule in glycolysis, the link reaction uses only one pyruvate molecule so the link reaction must happen twice for every glucose that goes through glycolysis, therefore 2 acetyl coenzyme a, 2 Co2 and 2 reduced NAD are produced for every glucose molecule

29
Q

what is the overall equation for one link reaction?

A

Pyruvate + NAD + CoA -> acetyl CoA + reduced NAD + CO2

30
Q

what are the products of the link reaction for one glucose?

A

2 acetyl coenzyme A (go into the krebs cycle), 2 carbon dioxide (released as a waste product), 2 reduced NAD (go to oxidative phosphorylation)

31
Q

what is the Krebs cycle also known as?

A

the citric acid cycle

32
Q

where does the Krebs cycle take place?

A

in the matrix

33
Q

how many times does the Krebs cycle go round for one glucose molecule?

A

twice as one glucose produces two pyruvate in glycolysis, so there are two link reactions per glucose molecule so two acetyl coenzyme A for Krebs

34
Q

what happens in the Krebs cycle?

A

Acetyl CoA (2C) from LR joins with oxaloacetate (4C) to form citrate (6C), Coenzyme A goes back to the LR to be reused, the 6C citrate loses CO2 (decarboxylation) and hydrogen (dehydrogenation), the hydrogen reduces NAD, and a 5C compound is formed, 5C molecule converted to a 4C molecule through decarboxylation and dehydrogenation, forms reduced NAD, dehydrogenation occurs reducing FAD, ATP is produced in substrate level phosphorylation, dehydrogenation occurs reducing NAD, 4C oxaloacetate then joins with acetyl CoA to restart the cycle

35
Q

what is substrate level phosphorylation?

A

direct phosphorylation of ADP with a phosphate group by using the energy from a coupled reaction

36
Q

what is oxidative phosphorylation?

A

production of ATP from oxidised NADH and FADH

37
Q

what does each Acetyl CoA entering the Krebs cycle result in?

A

2 Co2 molecules, 1 ATP molecule, 3 reduced coenzyme NAD and 1 reduced coenzyme FAD

38
Q

how is reduced NAD formed?

A

NAD + 2H+ = reduced NAD

39
Q

how is reduced FAD formed?

A

FAD + 2H+ = reduced FAD

40
Q

what happens to the majority of potential energy in Krebs?

A

taken away by coenzymes, later converted to ATP in oxidative phosphorylation

41
Q

what are coenzymes?

A

not actually enzymes, molecules required by some enzymes, carry hydrogen atoms between molecules e.g. NAD (respiration), FAD (Krebs), NADP (Photosynthesis)

42
Q

what happens in oxidative phosphorylation?

A

coenzymes NADH and FADH are carrying hydrogen atoms (which importantly have electrons), during oxidative phosphorylation some of the energy of the electrons is conserved in the formation of ATP

43
Q

where does oxidative phosphorylation take place?

A

in the cristae of the mitochondria - enzymes and proteins needed for oxidative phosphorylation are found here

44
Q

what are the steps of the electron transport chain? (oxidative phosphorylation)

A

hydrogen atoms for glycolysis and Krebs join with coenzymes NAD and FAD, reduced NAD and FAD donate the electrons of the hydrogen atoms they are carrying to the first electron transport molecule, electrons pass along the ETC in a series of redox reactions, as the electrons pass along the chain they release energy which causes the active transport of protons across the inner mitochondrial membrane into the inter-membranal space, the protons gather in the area between the mitochondrial membranes, they then diffuse through ATP synthase channels in the inner membrane, phosphorylating ATP, at the end of the chain the electrons combine with protons and oxygen making water, oxygen is the final acceptor of electrons in the ETC

45
Q

what is the theory of oxidative phosphorylation?

A

the chemiosmotic theory

46
Q

what is the step by step approach of oxidative phosphorylation?

A

when a lot of energy is released in one step, a lot is lost as heat (and therefore energy is wasted), if it is released slowly over a number of steps, more energy is available for the use of the organism, this is why NAD and FAD transfer their electrons gradually

47
Q

what are the alternatives to glucose in respiration?

A

lipids and proteins

48
Q

how are lipids used in respiration?

A

hydrolysed into glycerol and fatty acids, glycerol is phosphorylated and converted into TP, TP converted into pyruvate to enter the link reaction and then Krebs, the fatty acids are hydrolysed into 2C fragments which are converted into acetyl coenzyme A which then joins the Krebs cycle, the oxidation of lipids produces a lot of hydrogen atoms which are used to produce ATP during oxidative phosphorylation, this means that lipids release twice as much energy as carbohydrates

49
Q

how are proteins used in respiration?

A

hydrolysed into amino acids, deaminated (amino group removed), they then enter the respiratory pathway at different points depending on their number of carbon atoms, 3C compounds converted to Pyruvate, 4C compounds converted into intermediates in Krebs

50
Q

why is oxygen important in aerobic respiration?

A

it is the final electron acceptor, without it NADH no longer releases hydrogen at the end of the ETC, this creates a backlog of NADH and no NAD being regenerated, without NAD the Krebs cycle, link reaction, and glycolysis cannot happen

51
Q

why must the NADH produced during glycolysis be oxidised back into NAD+?

A

so it can be reused, if NAD+ remained as NADH there would be no carriers to take up the hydrogen atoms released during glycolysis, glycolysis would stop

52
Q

what happens when there is no oxygen?

A

in anaerobic conditions, neither Krebs nor the ETC can continue as all of the coenzymes are reduced, this means there will be no available NAD+ or FAD to take up the hydrogen atoms produced, this will cause the enzymes to stop working, as a result, the only ATP produced would be the net 2 during glycolysis

53
Q

How do we get around anaerobic conditions?

A

NAD+ is replenished by pyruvate, pyruvate accepts hydrogen from NADH, the newly oxidised NAD+ can be reused in glycolysis

54
Q

what is pyruvate converted to in plants and microorganisms? (anaerobic)

A

ethanol and CO2

55
Q

what is pyruvate converted to in animals? (anaerobic)

A

lactate

56
Q

what happens during anaerobic respiration in plants and microorganisms? (bacteria and fungus/yeast)

A

pyruvate is decarboxylated (loses CO2), forms ethanal, ethanal is reduced by H atoms supplied by NADH, this forms ethanol

57
Q

what is the equation for anaerobic respiration in bacteria and fungus/yeast?

A

pyruvate (3C) + NADH (reduced) -> ethanol (2C)+ CO2 (1C) + NAD+ (oxidised)

58
Q

what are the uses of anaerobic respiration in yeast?

A

yeast and the brewing industry, yeast grown anaerobically, ferments natural carbohydrates from plant products into ethanol (alcohol), grapes make wine, barley seeds make beer

59
Q

why does anaerobic respiration happen in animals?

A

occurs in animals to overcome a temporary oxygen shortage, survival advantage (immediately after birth, water with low O2, escape), most common in skeletal muscles

60
Q

what happens during anaerobic respiration in animals?

A

during an oxygen shortage, NADH from glycolysis can accumulate and must be removed, to get rid of it, pyruvate (C3H4O3) takes up 2 hydrogen atoms from the NADH, this forms lactate (C3H6O3), therefore NAD+ is regenerated from NADH by the reduction of pyruvate to lactate, when oxygen is available again the lactate is oxidised back to pyruvate which can be further oxidised to release energy or converted back into glucose

61
Q

what is the equation for anaerobic respiration in animals?

A

Pyruvate (3C) + NADH (reduced) -> lactate (3C) + NAD+ (oxidised)

62
Q

what is the role of lactate dehydrogenase?

A

reduces 2 Pyruvic acid and 2 NADH into 2 lactic acid and 2 NAD+

63
Q

what are the problems associated with lactate?

A

muscle cramps and fatigue, lactate is an acid so causes pH changes that affect enzyme action, it is removed by the blood and taken to the liver where it is converted into glycogen, this regeneration requires a lot of ATP which is produced by aerobic respiration, this regeneration therefore leads to an oxygen debt where the athlete is continuing high level of oxygen consumption (post-exercise oxygen consumption)

64
Q

why is anaerobic respiration important?

A

anaerobic respiration occurs mostly in the muscles when oxygen is being used up quicker than it can be supplied, so an oxygen debt occurs, in the absence of oxygen glycolysis would usually stop as there is a build up of NADH, for glycolysis to continue, reduced NAD+ must be converted back into NAD+, this happens when pyruvate takes up 2 hydrogen atoms from reduced NAD+ to make lactate, lactate causes cramp and fatigue in muscle tissue so this must be removed, it can be oxidised back to pyruvate or it is taken to the liver and converted to glycogen

65
Q

why does oxygen uptake remain higher than normal following exercise?

A

lactate is oxidised back to pyruvate

a level biology (21 decks)

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