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chapter 12 Flashcards

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AP® Biology flashcards
1
Q

Why do we need ATP (energy)?

A

● Anabolic reactions e.g. synthesis of DNA and
proteins
● Active transport
● Movement
● Homeostasis

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2
Q

Why is ATP used for energy?

A

● ATP is tri-phosphorylated. The removal of each
phosphate releases energy.

● ATP is easily hydrolysed and water-soluble (easy
to transport), making it a useful source of energy.

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3
Q

Name the four main stages of aerobic respiration and state where they occur.

A

● Glycolysis - cytosol
● Link reaction - mitochondrial matrix
● Krebs cycle - mitochondrial matrix
● Electron transport chain - inner mitochondrial
membrane

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4
Q

Outline the stages of glycolysis.

A
  1. Glucose (hexose sugar) phosphorylated to hexose
    bisphosphate by 2× ATP
  2. Hexose bisphosphate splits into 2× triose phosphate (TP)
  3. 2 molecules of TP oxidised to 2× pyruvate
    Net gain of 2× reduced NAD (NADH) and 2× ATP per glucose.
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5
Q

Draw a flowchart to explain glycolysis.

A

https://ibb.co/8PnX31L

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6
Q

How does pyruvate from glycolysis enter the mitochondria?

A

Via active transport (oxygen is required)

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7
Q

What happens during the link reaction?

A
  1. Oxidative decarboxylation and dehydrogenation of
    pyruvate to form acetate

Net gain of CO2 and 2× reduced NAD

  1. Acetate combines with coenzyme A (CoA) to form
    acetyl coenzyme A
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8
Q

Draw a flowchart to summarise the link reaction.

A

https://ibb.co/8MhdZwx

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9
Q

Define “substrate level phosphorylation”.

A

The synthesis of ATP by the transfer of a
phosphate group from a phosphorylated
intermediate to ADP.

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10
Q

What happens in the Krebs cycle?

A

Series of redox reactions that produces:
● ATP by substrate-level phosphorylation
● Reduced coenzymes
● CO2 from decarboxylation

Begins when the acetyl group from Acetyl CoA (2C) reacts with oxaloacetate (4C).The cycle regenerates oxaloacetate.

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11
Q

Draw a diagram to explain the Krebs cycle.

A

https://ibb.co/P66Bfcc

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12
Q

What is the electron transfer chain (ETC)?

A

● Series of carrier proteins embedded in the
membrane of the cristae of mitochondria

● Produces ATP through oxidative
phosphorylation via chemiosmosis during
aerobic respiration

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13
Q

What happens in the electron transfer chain (ETC)?

A

● Electrons released from reduced NAD and FAD
undergo successive redox reactions
● The energy released is coupled to maintaining the
proton gradient or is released as heat
● Oxygen acts as the final electron acceptor

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14
Q

How does chemiosmosis produce ATP during aerobic respiration?

A

Some energy released from the ETC is coupled to the active transport of H+ ions (protons) from the mitochondrial matrix into the intermembrane space.

H+ ions move down their concentration gradient into the mitochondrial matrix via the channel protein ATP synthase.

ATP synthase catalyses ADP + Pi → ATP

Note: chemiosmosis also occurs in photosynthesis in chloroplasts.

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15
Q

Draw a diagram to represent the ETC and chemiosmosis.

A

https://ibb.co/jM7QYsd

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16
Q

State the role of oxygen in the electron transfer chain.

A

Final electron acceptor:

O2 + 4H+ + 4e- → 2H2O

17
Q

Name the stages in respiration that produce ATP by substrate-level phosphorylation.

A

● Glycolysis (anaerobic)
● Krebs cycle (aerobic)

18
Q

What is the respiratory quotient? Write the equation.

A

Ratio of CO2 produced to O2consumed.

RQ = CO2/O2

19
Q

What is the RQ of carbohydrates, lipids and proteins?

A

● Carbohydrates: 1
● Lipids: 0.7-0.72
● Proteins: 0.8-0.9

20
Q

What could an RQ of greater than 1indicate?

A

● May indicate the conversion of carbohydrates to lipids

● RQ in anaerobic respiration is ∞

21
Q

Why do different respiratory substrates have different relative energy values?

A

Depends on the number of hydrogens in
the structure which are oxidised to water
e.g. the number of hydrogens is greater
in fatty acids than carbohydrates.

22
Q

Outline anaerobic respiration in muscle cells.

A

● Only glycolysis continues
● Reduced NAD (product of glycolysis) transfers
the H to pyruvate, forming lactic acid and
regenerating NAD
● Catalysed by enzyme lactate dehydrogenase

23
Q

Draw a flowchart to show how lactic acid is produced during anaerobic respiration in muscle cells.

A

https://ibb.co/jM7QYsd

24
Q

Outline anaerobic respiration in plants and microorganisms.

A

● Only glycolysis continues
● Pyruvate is decarboxylated to form ethanal
● Ethanal accepts a H from reduced NAD making ethanol. NAD
regenerated for glycolysis
● Less ATP is produced than in aerobic respiration

25
Q

Draw a flowchart to show how ethanol is produced during anaerobic respiration in plants and microorganisms.

A

https://ibb.co/BCJMNQh

26
Q

Name two types of molecules that can be used as alternative respiratory substrates.

A

● (amino acids from) proteins
● (glycerol and fatty acids from) lipids

27
Q

Compare the efficiency of aerobic and anaerobic respiration.

A

Hydrolysis of 1 mole glucose produces 2880 kJ. 1 molecule ATP produces 30.6 kJ. In aerobic respiration 32 ATP are gained whereas in anaerobic 2 ATP are gained.

● Aerobic efficiency= [(32 × 30.6)/2800] × 100 = 34%
● Anaerobic efficiency= [(2 × 30.6)/2800] × 100 = 2.1%
● Aerobic respiration is = 34/2.1= 16.2× more efficient than anaerobic

28
Q

Define oxygen debt and oxygen deficit.

A

● Oxygen debt (also referred to as Excess Post-Exercise
Oxygen Consumption or EPOC) is the amount of additional O2 needed after exercise to return body systems to their previous state

● Oxygen deficit is the volume of O2 required during exercise minus volume of O2 obtained

29
Q

How is rice adapted for growth in a low oxygen environment?

A

● Rapid growth maintains flowering parts above water line allowing gas
exchange through the leaves
● Aerenchyma in stem allows gases to move to submerged parts of the
plant
● Hydrophobic coating on leaves maintains air film around plant
● Root cells produce alcohol dehydrogenase to offset ethanol toxicity from
anaerobic respiration

30
Q

How can DCPIP be used to measure respiration in yeast?

A

To establish the chemiosmotic gradient, H+ is pumped out of the matrix. H+ reduces DCPIP producing a
colour change from blue to colourless. The rate at
which this change takes place allows us to measure
the rate of respiration in yeast.

31
Q

Define the term “respirometer”.

A

A device used to determine respiration
rate in living organisms by measuring the
change in volume of oxygen or carbon
dioxide.

32
Q

How could a student calculate the rate of respiration using a respirometer?

A

volume of O2 produced or CO2 consumed/ time × mass of sample

volume = distance moved by coloured drop ×
(0.5 × capillary tube diameter)2 × π

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