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IB Biology > 8: Metabolism, Cell Respiration & Photosynthesis > Flashcards

8: Metabolism, Cell Respiration & Photosynthesis Flashcards

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1
Q

Define metabolism

A

the sum of all enzyme-catalysed reactions in a cell

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2
Q

What are the 2 types of metabolic pathways + examples

A
  • chain reactions (Glycolysis)
  • cycles (ex: Krebs Cycle)
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3
Q

What is the effect of enzymes on chemical reactions

A

enzymes speed up the rate of reaction by lowering the activation energy

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4
Q

What is an inhibitor

A

a molecule that binds to an enzyme and slows down or stops the enzyme’s function

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5
Q

What are the 2 types of inhibitors

A

competitive and non-competitive

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6
Q

Describe competitive inhibitors

A
  • inhibitor has a similar shape to substrate
  • they bind to the active site
  • substrate cannot bind to the active site because inhibitor is already bound
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7
Q

Describe non-competitive inhibitors

A
  • inhibitor has a different shape to substrate
  • inhibitor binds to an allosteric site which alters the shape of the active site
  • prevents the substrate from binding to active site
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8
Q

How to reduce inhibition for competitive inhibitors

A

increase substrate concentration thereby out-competing the inhibitor

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9
Q

How to reduce inhibition for non-competitive inhibitors

A
  • no solution
    increasing the substrate concentration will have no effect because shape of active site is altered
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10
Q

Give an example of a competitive inhibitor

A
  • rubisco is an enzyme involved in photosynthesis
  • oxygen is a competitive inhibitor and prevents CO2 from binding
  • reactions involved in photosynthesis slow down
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11
Q

Give an example of a non-competitive inhibitor

A
  • cytochrome c oxidase is an enzyme involved in aerobic respiration
  • Cyanide ions are non-competitive inhibitors
  • cytochrome c oxidase cannot carry out its function
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12
Q

What is the purpose of end-product inhibition

A

it helps control metabolic pathways: they regulate the production of the end-product and help prevent the excess of the end-product

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13
Q

Describe end-product inhibition with the use of an example

A
  1. threonine is converted to an intermediate by an enzyme
  2. isoleucine is an end-product of the chain reaction and inhibits the first enzyme in the chain by acting as a non-competitive inhibitor
  3. It binds to an allosteric site + alters shape of active site –> prevents threonine from binding
  4. It prevents the production of excess isoleucine
  5. isoleucine will eventually detach itself from allosteric site + active site reforms + production of isoleucine increase again
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14
Q

What is end-product inhibition an example of

A

negative feedback

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15
Q

How to calculate the rate of reaction

A
  • draw a tangent line at specific time
  • change in the amount of reactants/products over time taken
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16
Q

Draw graph representing competitive and non-competitive inhibitors

A

https://www.khanacademy.org/science/ap-biology/cellular-energetics/environmental-impacts-on-enzyme-function/a/basics-of-enzyme-kinetics-graphs

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17
Q

What is oxidation

A
  • loss of hydrogen
  • loss of electrons
  • gain of oxygen
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18
Q

What is reduction

A
  • gain of hydrogen
  • gain of electrons
  • loss of oxygen
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19
Q

What are the stages of cellular respiration + locations

A
  • glycolysis (cytoplasm)
  • link reaction (matrix of mitochondria)
  • Krebs cycle (matrix of mitochondria)
  • electron transport chain (inner membrane of mitochondria)
  • oxidative phosphorylation and chemiosmosis (inner membrane of mitochondria)
20
Q

What is the equation for cellular respiration

A

C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP

21
Q

What are the main steps in glycolysis

A
  • phosphorylation
  • lysis
  • ATP formation, oxidation of triose phosphates + reduction of NAD
22
Q

Outline glycolysis (phosphorylation)

A

Adding phosphate to glucose with the use of 2 ATP forming a less stable 6-carbon sugar (hexose phosphate)

23
Q

Outline glycolysis (lysis)

A

The less stable 6-carbon sugar is split into 2 triose phosphates. The splitting process is known as lysis

24
Q

Outline glycolysis (ATP formation)

A
  • each triose phosphate is oxidised and this forms 2 pyruvates
  • 2NAD gets reduced to 2NADH
  • 4 ATP molecules are produced
25
Q

What are the end products of glycolysis

A
  • a net gain of 2 ATPs
  • 2 pyruvates
  • 2NADH
26
Q

What is special about glycolysis

A

no use of oxygen

27
Q

Outline link reaction

A
  • pyruvate is decarboxylated
  • the C atom is oxidised forming CO2 and forms an acetyl group, thereby reducing NAD into NADH
  • acetyl group binds to coA to form acetyl-CoA
28
Q

What is decarboxylation

A

the removal of the C atom and often the production of carbon dioxide

29
Q

What is phosphorylation

A

the addition of a phosphate, which makes the molecule less stable

30
Q

What are the products of the link reaction

A

acetyl-CoA, NADH, CO2

31
Q

Outline the Krebs cycle

A
  • Acetyl CoA combines with 4-carbon compound to form a 6-carbon compound
  • 6 carbon compound is oxidised and NAD+ is reduced to NADH and it is also decarboxylated and releases CO2
  • The 5-carbon compound is oxidised and decarboxylated to form a 4-carbon compound: CO2 and NADH produced
  • ADP is reduced to ATP. FAD is then reduced and forms FADH2 and NAD+ is reduced to form NADH.
32
Q

What are the products of the Krebs Cycle

A

ATP, 3NADH, 2CO2, FADH2 (for 1 pyruvate)

33
Q

Outline Electron transport chain pt.1

A
  • Electron transport chain performs chemiosmosis
  • Chemiosmosis is when the energy from a proton gradient is used to make ATP
    -NADH supplies electrons to the first carrier in the chain (forming NAD+)
  • FADH2 oxidised also and supplies electrons later in the chain (FAD)
34
Q

What is chemiosmosis

A

when the energy of a proton gradient is used to make ATP

35
Q

Outline the electron transport chain pt.2

A
  • as the electrons move along the chain, energy is released as the electrons are passed along the carrier proteins.
  • this energy is used to pump H+ ions across from the matrix to the intermembrane space of the mitochondria, thereby creating an H+ concentration gradient
36
Q

Outline the electron transport chain pt.3

A
  • Protons (H+) flow down the concentration gradient, from the intermembrane space to the matrix through protein channels called ATP synthase
  • The flow of protons releases energy, which is used by the ATP synthase to produce ATP through phosphorylation
37
Q

Outline the electron transport chain pt.4

A
  • This process is called oxidative phosphorylation because oxygen is the final electron acceptor.
  • Oxygen is reduced by electrons and forms water and the energy released by reducing oxygen to water is used to phosphorylate ADP and generate ATP.
  • each glucose molecule, about 32 molecules of ATP are produced
38
Q

Why is oxygen important in aerobic respiration

A
  • final electron acceptor
  • without O2, NADH and FADH2 will not be able to oxidise and transport electrons
  • ATP will not be produced
39
Q

List the features of mitochondria

A
  • outer membrane
  • inner membrane
  • intermembrane space
  • matrix
40
Q

What are the 2 stages of photosynthesis

A
  • light-dependent reactions
  • light-independent reaction
41
Q

Where do the 2 main stages of photosynthesis take place

A

stroma: light-independent
thylakoid intermembrane space: light-dependent

42
Q

What is the function of the intermembrane space

A

it is small to allow the concentration of H+ to build up quickly

43
Q

What is the function of the cristae

A

it is folded, the cristae increase the surface area for oxidative phosphorylation

44
Q

What are the adaptations of the outer membrane

A
  • impermeable to H+
  • permeable to pyruvate, CO2 and oxygen
45
Q

What structures do the thylakoid membranes have

A
  • Photosystem II
  • ATP synthase
  • Photosystem I
  • electron carriers

IB Biology (11 decks)

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