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Biology OCR AS Level > Respiration > Flashcards

Respiration Flashcards

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1
Q

What is respiration?

A

A process that occurs in living cells to release the energy stored in organic molecules like glucose. The energy released is used to immediately synthesis ATP from ADP and inorganic phosphate.

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2
Q

How is ATP used to drive other biological process?

A

It is hydrolysed back to ADP and inorganic phosphate (Pi) to release the energy stored in it.

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3
Q

What biological processes are driven by ATP?

A 
Active transport
Exocytosis + Endocytosis
Protein synthesis
DNA replication
Cell Division
Movement (of flagella/cilia/undulipodia and vesicles across the cytokeleton by motor proteins)
Activation of chemicals like glucose
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4
Q

What is metabolism?

A

Metabolism refers to all the chemical reactions that take place within living cells of an organism

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5
Q

Metabolic reactions can be:

A

Anabolic or catabolic

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6
Q

Define anabolic reactions?

A

Anabolic reactions are metabolic reactions where large molecules are synthesised from smaller molecules

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7
Q

Define catabolic reactions?

A

Catabolic reactions are metabolic reactions where large molecules are hydrolysed into smaller molecules.

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8
Q

Where does the thermal energy needed to maintain a suitable temperature in the body come from?

A

Some of the energy released in respiration is directly used to provide thermal energy. Hydrolysis of ATP also provides thermal energy.

Suitable temp important to allow enzymes to proceed at optimal rate.

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9
Q

What allows the ions and molecules within cells to move?

A

They use their kinetic energy.

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10
Q

Structure of ATP?

A

ATP is a phosphorylated nucleotide.
It consists of adenosine (a nitrogenous base of adenine) bonded to ribose (a 5C sugar), which is bonded to three phosphate groups.

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11
Q

What is the bond in ATP and where is it located?

A

ATP has a phosphodiester bond connecting the ribose sugar to the first phosphate group.

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12
Q

Draw an ATP molecule.

A

DRAW IT - PAGE 137

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13
Q

ATP is stable so does not break down (ADP + Pi) in solution in cells, however they are are hydrolysed readily by enzyme catalysis. What enzymes catalyses the breakdown of ATP into ADP and Pi?

A

ATP synthase

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14
Q

ATP is HYDROLYSED. So what else must be present, in addition to ATP synthase, for it to be broken down in to ADP?

A

Water must also be present:

ATP + H2O –> ADP + Pi

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15
Q

Can ADP be further hydrolysed to release energy?

A
  • ADP can be further hydrolsed to AMP, which can be further hydrolysed to just adenosine.
  • hydrolysis of ATP –> ADP and hydrolysis of ADP –> AMP release same amount of energy, but hydrolysis of AMP –> adenoise releases less energy.
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16
Q

Structure of Mitochondria?

A
  • Length: 2-5µm
  • Double membrane organelle: Inner + outer phospholipid membrane, seperated by intermembrane space, make up the envelope
  • Outer membrane = smooth
  • Inner membrane = folded to form cristae to provide a large surface area for electron carriers in the ETC & for protein channels associated with ATP synthase enzymes to facilitate proton diffusion
  • Mitochondrial matrix = enclosed by inner membrane, semi-rigid and gel-like, contains ribosomes, mitochondrial DNA and enzymes for link reaction and krebs cycle.
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17
Q

What is the matrix the site of?

A

This is the site of the link reaction and krebs cycle.

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18
Q

What does the matrix contain?

A
  • Enzymes invovled in link reaction and Krebs cycle
  • The coenzymes NAD + FAD
  • Oxaloacetate
  • Mitochondrial DNA and ribosomes
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19
Q

What is mitochondrial DNA used for?

A

Codes for the proteins needed for aerobic respiration. These proteins are then assembled by the ribosomes in the mitochondria.

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20
Q

How are pyruvate molecules brought into the mitochondria?

A

Pyruvate molecules are brought into the mitochondrial matrix across the inner + outer membrane, via specific pyruvate-H+ symport, a type of transport protein, to enter the link reaction.

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21
Q

How does the inner and outer membrane of the mitochondria differ?

A
  • Lipid composition of inner membrane is different to that of the outer membrane.
  • The inner membrane is less pearmeable (in fact its impermeable to H+ ions unlike outer membrane) to small ions like H+ than the outer membrane.
  • Folds called cristae in the inner membrane
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22
Q

Why is the inner membrane in close contact with the mitcohondrial matrix?

A

This is so that reduced NAD and FAD can easily deliver hydrogen to the electron transport chain.

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23
Q

What is glycolysis?

A
  • This is the first stage of respiration
  • It occurs in the cell cytoplasm
  • Involves the breakdown of glucose to pyruvate.
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24
Q

Stages of glycoysis

A

1) Glucose (6C) is phosphorylated into 1 hexose bisphosphate (6C) molecule using the 2 inorganic phosphates from the hydrolysis of 2 ATP molecules.
2) The hexose bisphosphate molecule splits up into 2 triose phosphate (3C) molecules.
3) The 2 TP molecules are oxidised into 2 pyruvate (3C) molecules, through dehydrogenation, catlaysed by dehydrogenase enzymes and aided by the coenzyme, NAD. 2NAD molecules accept a hydrogen from each TP to form 2 NADH molecules (reduction). At this stage, 4ADP molecules are phosphorylated into 4ATP molecules.

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25
Q

What is NAD?

A

NAD is a coenzyme that helps dehydrogenase enzymes carry out oxidation reactions.

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26
Q

What is substrate level phosphorylation.

A

Production of ATP from ADP and a phosphate group that has came directly from another molecule (occurs in both glycolysis, 4 molecules of ADP –> ATP, and Krebs cycle)

*How is this different to normal phosphorylation of ADP?

27
Q

For every glucose molecule, the products of glycolysis are:

A
  • Net gain of 2 ATP molecules
  • 2 molecules of NADH
  • 2 molecules of Pyruvate
28
Q

We have already looked at glycolysis, what are the other stages of aerobic respiration that occur after (in order)?

A

1) Glycolysis
2) The link reaction
3) The Krebs Cycle
4) Oxidative phosphorylation

29
Q

h

A

h

30
Q

Where does the link reaction occur?

A

In the mitochondrial matrix.

31
Q

What are the stages of the link reaction?

A

1) The carboxyl group of the 2 pyruvates is removed, decarboxylation, and 2 molecules CO2 is produced.
2) It is then dehydrogenated, and lost hydrogens combines with 2 NAD molecules to form 2 NADH. This leaves behind an acetyl group.
3) The acetyl group combines with coenzyme A to form acetyl CoA.

32
Q

What happens after the link reaction and where does this take place?

A

The coenzyme A carries the acetyl group into the Krebs cycle occurs which also takes place in the matrix.

33
Q

What are the stages of the Krebs cycle?

A

1) The acetyl group is released from acetyl CoA complex and it combines with a 4-carbon compound called oxaloacetate to form a 6-carbon compound, citrate.
2) Citrate is decarboxylated and dehydrogenated to form a 5-carbon compound. At this point, one molecule of CO2 and one of NADH is also formed.
3) This 5C compound is again decarboxylated and dehydrogenated to form a 4C compound with 1 more molecule of CO2 and NADH.
4) This 4C compound then combines temporarily binds and then is released from coenzyme A. At this point, subtrate-level phosphorylation occurs to form one molecule of ATP.
5) The 4C compound is dehydrogenated to form a different 4C compound and FADH.
6) The 4C compound is then rearranged with the help of an isomerase enzyme. It is also dehydrogenated to form a molecule of NADH. The end result is 1 molecule of oxaloacetate which is used again in the cycle.

34
Q

For each molecule of glucose how many turns of the Krebs cycle occurs?

A

For each molcule of glucose, there are 2 turns of the Krebs Cycle.

35
Q

What are the products of the Krebs cycle PER glucose?

A
  • 6 NADH
  • 2 FADH
  • 4 CO2
  • 2 ATP
36
Q

In respiration, glucose is used, however other substances can be respired aerobically. What are these susbtances?

A
  • Fatty acids
  • Glycerol
  • Amino acids
37
Q

How is fatty acids used as a respiratory substrate?

A
  • Fatty acid combines with acetyl CoA using energy from hydolysis of ATP to AMP.
  • The fatty acid-CoA complex enters the mitochondria and is broken down into many acetyl groups each attached to CoA.
  • The conversion of fatty acid-CoA to acetyl-CoA is known as the beta-oxidation pathway and this pathway generates NADH + FADH.
  • This acetyl CoA can then enter the Krebs cycle to continue aerobic respiration.
38
Q

How is glycerol used as a respiratory substrate?

A

Glycerol may be converted to pyruvate which can enter the link reaction

39
Q

How are amino acids used as a respiratory substrate?

A

The amino acids is deaminated (the amino group NH2 group may be removed) to leave behind a keto acid which enters the respiratory pathway as pyruvate, acetyl CoA or a Krebs Cycle acid such as oxaloacetate. This depends on the type of amino acid.

40
Q

By the end of the Krebs cycle what product is made?

A

By the end of the Krebs cycle, glucose has now been made from carbon dioxide.

41
Q

What is the final stage of aerobic respiration and where does it take place?

A

Oxidative phosphorylation which takes place across the inner mitochondrial membrane.

42
Q

What happens in oxidative phosphorylation?

A

1) NADH and FADH are reoxidised when they give their hydrogen atoms to the ETC. This leaves NAD and FAD that return to other stages of respiration.
2) The released hydrogen atoms released then dissociate into protons and electrons.
3) The protons go into solution in the mitochondrial matrix whilst the electrons enter the ETC, where it reduces an Fe3+ iron ion at the centre of the first electron carrier protein before it is re-oxidised. Upon re-oxidation, the electrons move from one electron carrier to the next, releasing energy each time.
5) This energy is used to actively pump protons across the inner mitochondrial membrane into the intermembrane space.
As protons accumulate, a proton gradient forms across the membrane. This generates a chemiosmotic potential or a proton motive force. Protons diffuse down the gradient through channel proteins associated with ATP synthase enzymes. As protons diffuse down the protein channel, conformational change in the ATP synthase enzyme allows ADP and Pi to combine into ATP. This flow of protons is known as chemiosmosis. 6) The formation of ATP in this way is called oxidative phosphorylation.
7) Oxygen is the final electron acceptor as it combines with the electrons leaving the ETC as well the protons diffusing through the channel proteins to produce water.

43
Q

Why won’t the protons that accumulate in the inner membrane space diffuse across the outer mebrane, to outside fo the mitochondria?

A

The outer membrane has a low degree of permeabiity to protons. (Inner membrane is impermeable to protons, which is why the protein channels are required).

44
Q

How many ATP are theoretically produced in oxidative phosphorylation?

A

28 ATP molecules.

Therefore majority of ATP is made in the oxidative phosphorylation stage of aerobic respiration.

45
Q

How many ATP are made theoretically in aerobic respiration in general?

A

32 ATP molecules

46
Q

Why is the theoretical yield of ATP rarely achieved?

A
  • Some ATP is used by the symport transport protein in actively transporting pyruvate into the matrix
  • Some ATP is used in transporting the reduced NAD produced in glycolysis from the cytoplasm to the mitochondria
  • Some protons may leak out through the outer mitochondrial membrane
47
Q

Which of thr four stages of aerobic respiration also occur in anaerobic respiration?

A

Only glycolysis occurs in both aerobic and anaerobic respiration.

48
Q

If oxygen is not present, why does only glycolysis occur and not he other three stages?

A

No oxygen = it cannot act as the final electron acceptor at the end of oxidative phosphorylation = protons diffusing through the channels cannot combine with electrons and oxygen to create water.

  • The concentration of protons in the matrix therefore increases and the proton gradient decreases
  • Oxidative phosphorylation stops
  • NADH and FADH cannot donate their hydrogen atoms to reform NAD and FAD that would be reused in link reaction and Krebs, so these stages also stop.
49
Q

Anaerobic respiration can take two different pathways after the formation of pyruvate. What are they?

A

Fungi and Plants use the ethanol fermentation pathway during anaerobic respiration whilst animals use the lactate fermentation pathway.

50
Q

What happens in the ethanol fermentation pathway?

A

1) Glycolysis occurs as normal, forming 2 ATP molecules.
2) The pyruvate produced in glycolysis is decarboxylated and converted into ethanal. This releases CO2 and the reaction is catalysed by pyruvate decarboxylase.
3) The ethanal is then reduced to ethanol, by combining with hydrogens released from the NADH molecules made during glycolysis. The enzyme ethanol dehydrogenase catalyses this.
4) The NAD produced can now be reused in glycolysis by accepting more H atoms from TP.

51
Q

What happens in the lactate fermentation pathway?

A

1) Glycolysis occurs as normal
2) Pyruvate formed during glycolysis reduced to lactate by accepting a Hydrogen atoms released from NADH made during glycolysis. Lactate dehydrogenase catalyses this.
4) The NAD produced can reused in glycolysis by accepting H atoms from TP.

52
Q

What happens to the produced Lactate?

A

It moves out of the cells into the blood stream where it is carried to the liver. When more oxygen is available, the lactate may be converted into pyruvate which enters the link reaction, or it may be reduced to glucose and glycogen. Lactate is acidic and therefore must be converted into another compound.

53
Q

Does either pathway (lactate or ethanol fermentation) produce ATP by occurring?

A

These pathways do not produce any ATP themselves HOWEVER, they allow glycolysis to occur repeatedly by recelcyling the NAD molecules so that glucose molecule can continuosly enter glycolysis to produce2 net molecules of ATP.

54
Q

What is a respiratory substrate?

A

A respiratory substrate is an organic substance. that can be oxidised by respiration to release energy and make ATP.

55
Q

What is the main respiratory substrate?

A

Glucose

*Some animals only use glucose to respire.

56
Q

How is glucose stored in animals?

How is glucose stored in plants?

A

Glucose is stored as glycogen in animmals

Glucose is stored as starch in plants

57
Q

How are carbohydrates converted to glucose for use as a respiratory substrate?

A

Starch/glycogen is hydrolysed to a dissacharide which is hydrolysed to a monosaccharide. The monosaccharide can then be changed to glucose (if it isnt already) using isomerase enzymes.

58
Q

How are lipids converted to fatty acids and glycerol for use as a respiratory substrate?

A

Triglycerides (a lipid) is hydrolysed into glycerol and fatty acids using lipase enzymes.

59
Q

How are proteins converted to amino acids for use as a respiratory substrate?

A

Proteins are hydrolysed into amino acids using protease enzymes.

60
Q

What is the relationship between amount of hydrogens in respiratory substrate and the amount of ATP produced.

A

The more hydrogen atoms there are in a molecule of a respiratory substrate, the more ATP can be generated per molecule of substrate. This is because there are more hydrogen ions/protons available for chemiosmosis in oxidative phosphorylation, to produce ATP.

61
Q

However, eventhough more hydrogens mean more ATP what else must there be more of?

A

More oxygen because more oxygen is needed to act as the final electron acceptor and form water

62
Q

The respiratory quotient, is the ratio of CO2 produced to O2 consumed. How to calculate respiratory quotient?

A

RQ = CO2 produced/O2 consumed

  • If given equation you divide the number of molecules of CO2 made/numbber of molecules of O2 consumed, so for glucose using the equation would be 6/6 = 1 = RQ value.
  • ratio so no units, but the numerator and denominator must have the same units
63
Q

What does an RQ value greater than 1 mean?

A

A value above 1 indicates aerobic respiration is taking place.

64
Q

What is the RQ for lipids proteins and carbohydrates USUALLY (not always)?

A 
Carbohydrates = 1
Proteins = 0.8-0.9
Lipids = 0.7

Biology OCR AS Level (10 decks)

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