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IB Biology HL > 8 Metabolism (HL) > Flashcards

8 Metabolism (HL) Flashcards

1
Q

How do enzymes increase the rate of biochemical reaction?

A

Decreasing activation energy

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2
Q

Define exergonic reaction

A

Energy is released
Usually catabolic

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3
Q

Define endergonic reaction

A

Energy is absorbed
Usually anabolic

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4
Q

What are the two types of enzyme inhibition?

A

Competitive and non competitive

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5
Q

Describe competitive inhibition

A

Inhibitor is structurally similar to the substrate and directly binds to the active site

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6
Q

What occurs to the effects of the competitive inhibitor if substrate concentration increases?

A

Effects decrease

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7
Q

Describe non-competitive inhibition

A

Inhibitor binds to an allosteric site and changes the active site shape so the substrate can no longer bind

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8
Q

What occurs to the effects of the non-competitive inhibitor if substrate concentration increases?

A

No change

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9
Q

Give an example of a competitive inhibitor

A

Relenza
Drug which fights influenza by competitively inhibits the enzymes which triggers the release of virions from the infected cell

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10
Q

Give an example of a non-competitive inhibitor

A

Cyanide
Binds to the allosteric site on cytochrome oxidase (carrier molecule in the ETC of respiration)
Therefore ATP is not produced

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11
Q

Describe end-product inhibition

A

Final product inhibits an earlier step via non-competitive inhibition (temporarily inactivates the enzyme)

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12
Q

Which two sources can synthesise ATP from ADP?

A

Solar energy
Oxidative processes

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13
Q

What is the first step in the breakdown of carbohydrates?

A

Glycolysis

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14
Q

Where does glycolysis occur?

A

Cytosol

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15
Q

What happens in glycolysis?

A

Hexose (6C) -> Pyruvate (3C)

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16
Q

What are the 4 steps of glycolysis?

A

Phosphorylation
- 2ATPs phosphorylate the hexose making it more unstable
Lysis
- 6C sugar breaks into 2 triosephosphates (3C)
Oxidation
- H atoms are removed from each 3C (NAD+->NADH + H+) (2x NADH in total)
ATP formation
- 2 ATP molecules are synthesised per 3C molecule to produce pyruvate (4x ATP in total)

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17
Q

What is the net gain of H carrying molecules and ATP in glycolysis per hexose?

A

2 ATP (4 produced, 2 used)
2 (NADH + H+)

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18
Q

What happens after glycolysis in the absence of oxygen?

A

The pyruvate is converted to lactic acid

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19
Q

What happens after glycolysis in the presence of oxygen?

A

The pyruvate is transported to mitochondria for further breakdown

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20
Q

What is the second step of respiration (1st step unique to aerobic respiration)?

A

Links reaction

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21
Q

Where does the links reaction occur?

A

The pyruvate is transported into the mitochondrial matrix at the start of the reaction

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22
Q

What occurs to each pyruvate in the links reaction?

A

Decarboxylation (loss of a CO2)
Loss of 2H for NAD+ -> NADH + H+ creates a 2C which forms an acetyl group
Coenzyme A bonds to the acetyl group -> Acetyl CoA

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23
Q

What is the net gain of H carrying molecules and ATP in the links reaction per hexose?

A

2 (NADH + H+)
(as well as 2CO2)
1 of each per pyruvate

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24
Q

What is the third step of respiration?

A

Krebs cycle

25
Q

Where does the Krebs cycle occur?

A

Mitochondiral matrix

26
Q

What is the starting molecule that the Acetyl CoA binds to at the start of the Krebs cycle?

A

A 4C molecule called oxaloacetate

27
Q

What is formed when oxaloacetate binds with the acetyl group of Acetyl CoA?

A

A 6C compound (citrate)

28
Q

What happens to citrate (in which order) in the Krebs cycle?

A

Loss of 1x CO2 molecule
Loss of 2H (NAD+ -> NADH + H+)
(5C compound produced)
Loss of 2H (NAD+ -> NADH + H+)
Loss of 1x CO2 molecule
(4C compound produced)
1x ATP synthesised
Loss of 2H (FAD+ -> FADH2)
Loss of 2H (NAD+ -> NADH + H+)
Final Product -> Oxaloacetate (4C)

29
Q

What is the net gain of H carrying molecules and ATP in the Krebb’s cycle per hexose?

A

2x ATP
2x FADH2
6x NADH + H+
(4x CO2)
(2 cycles - 1 per pyruvate)

30
Q

What is the fourth and final stage of aerobic respiration?

A

Electron transport chain (oxidative phosphorylation)

31
Q

Where does the electron transport chain in respiration take place?

A

Cristae (inner mitochondrial membrane folds)

32
Q

What are the three steps of oxidative phosphorylation (resp ETC)?

A

Generating a proton motive force
ATP Synthesis vis chemiosmosis
Reduction of oxygen

33
Q

Describe the process of generating a proton motive force (resp ETC)

A

Hydrogen carriers are oxidised and release high energy electrons (e-) and protons (H+)
e- are transferred to the ETC
e- pass through the chain and lose energy as they do which pumps H+ from the matrix
H+ accumulates in the intermembrane space (electrochemical gradient)

34
Q

Describe ATP synthesis via chemiosmosis as a step of the respiration ETC

A

H+ ions will diffuse back into the matrix (chemiosmosis) which is facilitated by ATP synthase thus triggering the synthesis of ATP

35
Q

Describe the reduction of oxygen as a step of the respiration ETC

A

O2, H+ and the de-energised e- are lost through water synthesis

36
Q

What is the yield of one hexose sugar in the electron transport chain?

A

32 ATP

37
Q

What is the final yield of aerobic respiration of one hexose?

A

6x CO2
10x NADH
2x FADH2
36x ATP

38
Q

Where does the light dependent part of photosynthesis occur?

A

Thylakoid

39
Q

Where does the light independent part of photosynthesis occur?

A

Stroma

40
Q

What are the three steps of light dependent photosynthesis?

A

Excitation of photosystems
Photophosphorylation
Reduction of NADP+ and photolysis of water

41
Q

Describe excitation of photosystems as a step of light dependent photosynthesis

A

Photosystem pigments in the thylakoid membrane absorb light and electrons in them become excited
The excited electrons are transferred to carrier molecules in the thylakoid membrane

42
Q

What wavelength does PSI absorb?

A

700nm

43
Q

What wavelength does PSII absorb?

A

680nm

44
Q

Describe (non-cyclic) Photophosphorylation as a step of light dependent photosynthesis

A

Excited e- from PSII are transferred through the membrane and lose energy as they do, translocating H+ ions into the thylakoid
Chemiosmosis occurs as the H+ ions return to the stroma via ATP synthase, synthesising ATP (from ADP + Pi)
Deenergised e- from PSII are taken up by PSI

45
Q

Describe the reduction of NAD+ and photolysis of water as a step of light dependent photosynthesis

A

Excited e- from PSI may be transferred to a carrier molecule to reduce NADP -> NADH (for the light independent reaction)
Electrons lost from PSII are replaced via photolysis of water (H+ used in chemiosmosis and O is a byproduct)

46
Q

Describe the reduction of NAD+ and photolysis of water as a step of light dependent photosynthesis

A

Excited e- from PSI may be transferred to a carrier molecule to reduce NADP -> NADH (for the light independent reaction)
Electrons lost from PSII are replaced via photolysis of water (H+ used in chemiosmosis and O is a by-product)

47
Q

Describe cyclic photophosphorylation

A

Involves only PSI and no reduction on NADP+
e- cause chemiosmosis from PSI but re-enter PSI and are re-energised

48
Q

Where does the Calvin cycle occur?

A

Stroma

49
Q

What are the three steps of the Calvin cycle?

A

Carbon fixation
Reduction of GP
Regeneration of RuBP

50
Q

What is the initial (and final) molecule in the Calvin cycle?

A

RuBP (5C)

51
Q

Describe carbon fixation as a part of the Calvin cycle?

A

RuBP carboxylase catalyses 3RuBP+3CO2-> 3(6C) compound-> 6x GP (3C)

52
Q

What does GP stand for (photosynthesis)?

A

Glycerate - 3- phosphate

53
Q

Describe reduction of GP as a part of the Calvin cycle?

A

6(ATP-> ADP + Pi) and 6(NADPH->NADP+ + H+) converts 6GP to 6TP (3C)

54
Q

What does TP stand for (photosynthesis)?

A

Triose phosphate

55
Q

Describe Regeneration of RuBP as a part of the Calvin cycle?

A

1 out of 6TPs is removed to produce half a sugar
3(ATP -> ADP + Pi) converts The other 5TP into 3x RuBP

56
Q

How many RuBP are involved in each Calvin cycle?

A

3
(2 cycles per glucose)

57
Q

How many Calvin cycles are required for a full sugar to be synthesised?

A

2

58
Q

How many CO2 are needed to produce a full sugar in the Calvin cycle?

A

6

59
Q

Describe a chloroplast

A

Stroma (central cavity)
Thylakoids - flattened dinks with high SA:Vol
Grana - Thylakoids in stacks to increase SA:Vol
Lamella - connect and separate granum

IB Biology HL (35 decks)

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