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DSE Biology > Chapter 21: Respiration > Flashcards

Chapter 21: Respiration Flashcards

1
Q

Glycolysis

A
  • Site: Cytoplasm
  • Glycolysis is catalysed by enzymes and does not require oxygen
  • 1 molecule of glucose is activated by phosphorylation using 2ATP and broken down to 2 molecules of triose phosphate
  • Each molecule of triose phosphate loses one hydrogen atom to form pyruvate. The energy released during the process is used to form 4 ATP, resulting in a net gain of 2 ATP. The hydrogen atom is accpeted by NAD to form NADH.
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2
Q

Linked reaction

A

Site: Mitochondrial matrix
- Each pyruvate molecule loses one molecule of carbon dioxide and one hydrogen atom
- The hydrogen atom is accepted by NAD to form NADH
- The remaining acetyl group combines with Coenzyme A to form Acetyl-CoA (carries the acetyl group into the Krebs cycle)

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3
Q

Role of Coenzyme A

A
  • carrier molecule
  • carries the acetyl group into the Krebs cycle
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4
Q

What will happen to pyruvate if Krebs cycle is inhibited?

A
  • Pyruvate will not be metabolized
  • However, the rate of glycolysis remains unchanged and the rate of oxidation of TP to pyruvate remains unchanged
  • Hence, pyruvate accumulates
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5
Q

Krebs cycle

A

1. Formation of 6-C compound
Acetyl-CoA combines with another 4-C compound to form a 6-C compound. Coenzyme A is released.

Coenzyme A is regenerated and it can carry other acetyl groups formed from pyruvate in glycolysis into the Krebs cycle.

2. Regeneration of the 4-C compound
The 6-c compound is oxidised stepwise to regenerate the 4-C compound. Each of the reactions is catalysed by a different enzyme.
Each 6-C compound loses:
- 2 carbon dioxide molecules
- 4 hydrogen atoms (accpeted by 3NAD to form 3NADH and FAD to form FADH respectively)
- 1 ATP is directly formed by the energy released from the conversion

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6
Q

Oxidative phosphorylation

A

Site: mitochondrial inner membrane
- NADH and FADH are oxidised to regenerate NAD and FAD by losing hydrogen
- the hydrogen atom dissociates into hydrogen ions and electrons
- the electrons are accepted by electron accpetors and are passed down an ETC
- the electrons take part in redox reactions along the ETC catalysed by enzymes embedded in the inner membrane of mitochondria.
- energy released in the reactions: used to form ATP
- oxygen, final hydrogen and electron acceptor, combines to form water

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7
Q

Significance of oxygen as the final hydrogen and electron acceptor

A

Final hydrogen acceptor
- NAD and FAD can be regenerated
- so they can act as oxidising agent again to accept hydrogen atoms in glycolysis, linked reaction and Krebs cycle again

Final electron acceptor
- the electrons from the oxidation of NADH and FADH can be passed along the ETC
- releasing energy to form ATP again

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8
Q

Explain why the ETC cannot operate under anaerobic conditions.

A
  • Without oxygen, which acts as the final electron acceptor of the ETC, electrons released from the oxidation of NADH and FADH cannot go through the ETC
  • Oxidative phosphorylation stops
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9
Q

Explain why NAD and FAD cannot be regenerated without the presence of oxygen in aerobic respiration

A
  • Without oxygen, which acts as the final electron acceptor of the ETC, electrons released from the oxidation of NADH and FADH cannot go through the ETC
  • Oxidative phosphorylation stops
  • NADH and FADH cannot be reduced
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10
Q

Significance of lactic acid fermentation

A
  • maximum rate of aerobic respiration
  • insufficient oxygen supply for complete oxidation of glucose in muscles
  • lactic acid fermentation provides additional energy in a short period of time
  • muscles can contract more powerfully at a higher rate
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11
Q

Removal of the lactic acid produced

A
  • (20%) Lactic acid is converted into pyruvate and converted toAcetyl-CoA in linked reaction, enters Krebs cycle
  • (80%) Additional amount of energy: convert lactic acid to glycogen for storage
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12
Q

Oxygen debt

A
  • After exercise, breathing rate increases
  • More oxygen, more NAD generated to oxidise lactic acid to pyruvate
  • Additional amount of oxygen required to remove all lactic acid: oxygen debt
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13
Q

Insufficient glucose supply

A
  • rate of glycolysis decreases
  • concentration of pyruvate decreases
    Decrease in ATP production in the following processes —> unable to fulfill the basal level of energy requirement —> cells become dead.
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14
Q

Insufficient oxygen supply

A
  • Rate of regeneration of NAD and FAD decreases
  • Suppress the rate of oxidative
    phosphorylation
  • Suppress the conversion rate from 6-C to 4-C
    Decrease in ATP production in the following processes —> unable to fulfill the basal level of energy requirement —> cells die
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15
Q

Extremely high temperature

A
  • Enzymes become denatured
  • Respiratory rate decreases
    Decrease in ATP production in the following processes —> unable to fulfill the basal level of energy requirement —> cells become dead.
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16
Q

ATP yield per unit mass of glucose

A
  • ATP yield per unit mass of glucose broken down in a mature red blood cell is lower than that in a skeletal muscle cell in aerobic condition. (1)
  • There is no mitochondria in a mature red blood cell. (1)
  • ATP is only produced from glycolysis (anaerobic respiration) in a mature red blood cell. (1)
  • Krebs cycle and oxidative phosphorylation that take place in mitochondria and produce more ATP do not take place in mature red blood cells. (1)
17
Q

Change in amount of 6-C compound and 4-C compound when one suppresses breath under water.

A
  • Oxygen acts as the final electron and hydrogen acceptor.
  • Under an insufficient supply of oxygen, the hydrogen ions and resting electrons will not be received, thus suppressing the regeneration of NAD and FAD.
  • With fewer NAD and FAD, the conversion rate from 6-C compounds to 4-C compounds will be lowered.
  • Thus, 6-C compounds accumulate while the number of 4-C compounds drops.
18
Q

Why do athletes have a smaller increase in lactic acid concentration compared to average people during exercise?

A
  • During exercise, the increase in lactic acid concentration in the blood of athletes is smaller than that of average people.
  • it is because regular training can strengthen the heart muscle or increase the
  • breathing depth, thus the rate of oxygen supply to the body cells increases.
  • Thus it enhances
  • the oxidation of lactic acid in the liver.
19
Q

Short-distance race VS 1500m run - Which one has a lower proportion of energy released by anaerobic respiration? Explain.

A
  • A lower proportion of anaerobic respiration is carried out during long runs. 1500 m race involves a much longer distance of running at a lower speed that lasts for a longer time. (1)
  • 1500 m race does not require a large amount of energy released in a short period of time.
  • Thus the energy demand can be met by a lower proportion of anaerobic respiration
20
Q

https://drive.google.com/drive/my-drive?dmr=1&ec=wgc-drive-globalnav-goto

Suggest how a change in the surrounding environmental temperature may cause the movement of the liquid dye droplet observed in set-up Y.

A

Increase in surrounding environmental temperature increases the temperature of the air inside the boiling tube in set-up Y

which causes the air in the tube to expand/increase the air pressure in the
boiling tube

when the air pressure in the boiling tube become higher than the surrounding atmospheric pressure, the liquid dye droplet in the capillary tube is pushed away from the tube.

21
Q

https://drive.google.com/file/d/1t9JO86zotr_cWTmUqu0hYeqFMAzDdP1K/view?usp=sharing

Errors

A
  1. There may be microorganisms on the grasshopper that also absorbed oxygen in respiration and decrease the air pressure inside the tube in set-up X
  2. The heat released by the grasshopper that also absorb oxygen in respiration may increase the air pressure inside the tube in set-up X
22
Q

2012/II/1biv The average running speed in a marathon is usually much lower than that in a 100 m race.
Explain why it is not possible for marathon runner to run at the same average speed as a 100 m runner
throughout a marathon.

A

Because marathon runners have to run a longer distance than 100 m runners, their muscles need to
sustain contractions for a longer time. (1)
If they run at the speed of 100 m race, the oxygen supply to muscles will be insufficient. (1)
Muscles will carry out anaerobic respiration (1) to produce lactic acid.
As a result, lactic acid accumulates in the muscles (1)
Leading to muscle fatigue (1), i.e. muscles fail to contract any more

DSE Biology (7 decks)

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