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4. Respiration Flashcards

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1
Q

Preparation of mitochondria from liver tissue. Substances added to the preparation and the amount of oxygen was monitored over a period of time. Suggest why the respiratory substrate added was a molecule from the Krebs cycle, not glucose

A

Glycolysis does not take place in the mitochondria (occurs in the cytoplasm)

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2
Q

What is the respiratory quotient (definition)?

A

The ratio of the volume of carbon dioxide evolved to that of oxygen consumed by an organism, tissue, or cell in a given time. (Vol of CO2 emitted/ vol of O2 consumed

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3
Q

Little carbon dioxide emitted after time C (little oxygen remaining). Explain why.

A

Insufficient oxygen left/ all respiratory substrate used / not enough oxygen to act as terminal electron acceptor

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4
Q

When the temperature is raised from 20 to 30 degrees, the cockroach becomes more active and its respiration rate and oxygen consumption increase. What causes the increase in respiration rate?

A

Respiration controlled by enzymes/ increased kinetic energy/ collision rate

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5
Q

The rate of carbon dioxide production by cockroaches is less 72 hours after they were last fed than it is 1 hour after they were fed. Explain why.

A
  • Change of respiratory substrate

- Carbohydrate to fat

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6
Q

Potometer experiment set up with blowfly larvae- sodium hydroxide in experiment 1 to absorb co2. Experiment 2- water used instead of NaOH. Measuring oxygen uptake from how far the bubble moves. Give two reasons why the apparatus was left for ten minutes with the tap open when it was first placed in the water bath.

A
  • Allow ANIMALS to equilibrate
  • Allow for pressure changes in the air in the apparatus
  • Reach respiration rate typical of that temperature
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7
Q

Explain why the bead of liquid moved along the scale in the first experiment when there was NaOH but didn’t when the NaOH was replaced with water in the second experiment

A
  • Exp 1- Oxygen CONSUMED by animals
  • CO2 given out/ CO2 released but absorbed by NaOH
  • Reduction in volume/ pressure
  • Exp 2- O2 consumed= CO2 released/ because respiratory quotient =1
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8
Q

Scientists measured respiration in 3 parts of an ecosystem by measuring CO2 released by

  • plants leaves
  • plants roots and stems
  • non photosynthetic organisms

A student concluded that the plants carry out more respiration than non photosynthetic organisms in the ecosystem. Suggest why the data do not support the conclusion.

A
  • Data only includes heterotrophic soil organisms
  • Doesn’t include animals(above ground)/ non soil organisms
  • Doesn’t take into account anaerobic respiration
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9
Q

Suggest how the rise in the mean rate of photosynthesis could lead to the rise in the
mean rate of respiration in soil under trees.

A
  • Photosynthesis produces sugars
  • Sugars moved to the roots
  • Sugars required for respiration
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10
Q

Suggest why there is a delay between the rise in the mean rate of photosynthesis and
the rise in the mean rate of respiration in the roots.

A

-Takes time to move the sugars to the roots

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11
Q

What are the products of

  • Aerobic respiration
  • Anaerobic respiration
A

-Aerobic
>Carbon dioxide
>Water
>Much ATP

-Anaerobic
>Lactate (in animals)
>Ethanol (in bacteria)
>Carbon dioxide
>Only a little ATP in both cases
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12
Q

Briefly describe what happens in the 4 stages of respiration.

A
  • GLYCOLYSIS- splitting of glucose 6C into two pyruvate molecules 3C
  • LINK REACTION- conversion of pyruvate 3C into carbon dioxide and Acetyl Coenzyme A 2C
  • KREBS CYCLE - introuction of Acetyl Coenzyme into a series of oxidation and reduction reactions that yields a small number of ATP and lots of electrons
  • ELECTRON TRANSPORT CHAIN - synthesis of lots of ATP and water as a by product using electrons produced in the Krebs cycle
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13
Q

Where does glycolysis occur?

A

The cytoplasm of the cell

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14
Q

What are the 4 stages of glycolysis?

A
  • Activation of glucose by phosphorylating it using 2 phosphates from ATP. This makes the glucose more reactive and lowers its activation energy
  • Splitting of phosphorylated glucose- each glucose split into 2 triose phosphate molecules
  • Oxidation of triose phosphate- hydrogen is removed from each triose phosphate and transferred to NAD to from NADH (reduced NAD)
  • Production of ATP- enzymes convert the two molecules of triose phosphate into two molecules of pyruvate, in the process regenerating two molecules of ATP from ADP (2 ATP per molecule of pyruvate produced)
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15
Q

What is the net yield from glycolysis?

A
  • 2 molecules of reduced NAD
  • 2 ATP (2 from each conversion of TP to pyruvate - 2 ATP to start glycolysis)
  • Two molecules of pyruvate
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16
Q

Is the process of glycolysis affected by the presence/ absence of oxygen?

A

No, it occurs regardless of whether there is oxygen- therefore it is the starting point for both aerobic and anaerobic respiration

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17
Q

Why is anaerobic necessary for glycolysis to continue?

A

Anaerobic respiration is necessary in order to re oxidise NAD so that glycolysis can continue

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18
Q

Describe how pyruvate is oxidised in the link reaction in order for it to enter the Krebs cycle so it can release its potential energy to form ATP. (Describe the processes in the link reaction)

A
  • Pyruvate is oxidised by removing hydrogen
  • This hydrogen is accepted by NAD to form reduced NAD (later used to produce ATP)
  • Acetyl (2C) combines with Coenzyme A to form Acetylcoenzyme A
  • A carbon dioxide is produced for each pyruvate
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19
Q

What is the overall equation for the processes in the link reaction?

A

Pyruvate + NAD + CoA –> CO2 + AcetylCoA + reduced NAD

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20
Q

Where does the Krebs cycle occur?

A

In the matrix of the mitochondria

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21
Q

Describe the sequence of events that take place in the Krebs cycle.

A
  • Acetyl coenzymeA 2C combines with oxaloacetate (4C) to produce citric acid (6C)
  • Citric acid loses carbon dioxide and hydrogens to form oxaloacetate and a single molecule of ATP is produced as a result of substrate level phosphorylation
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22
Q

What does the Krebs cycle produce per molecule of pyruvate?

A
  • Reduced coenzymes NAD and FAD
  • One molecule of ATP
  • 3 molecules of CO2

This yield is doubled per molecule of glucose as each glucose molecule produces 2 pyruvate molecules.

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23
Q

What are coenzymes and what do they do? Give examples of coenzymes in the Krebs cycle.

A

Molecules that some enzymes require in order to function. In photosyntehsis and respiration, they carry hydrogen atoms from one molecule to another. Examples include:

  • NAD- important in respiration
  • NADP- important in photosynthesis
  • FAD- important in the Krebs cycle
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24
Q

What is the significance of the Krebs cycle? Why does it play an important role in the cells of organisms?

A
  • Breaks down macromolecules into smaller ones eg pyruvate is broken down into carbon dioxide
  • Produces hydrogen atoms that are carried by NAD to the electron transport chain for oxidative phosphorylation which produces ATP
  • Regenerates oxaloacetate 4C which combines with AcetylCoA which would otherwise accumulate
  • It is a source of intermediate compounds used by cells to manufacture substances such as amino acids, fatty acids and chlorophyll.
25
Q

What is the function of NAD in respiration?

A

It works with dehydrogenase enzymes to catalyse the removal of hydrogen from substrates which are then carried by NAD to other molecules such as the hyrogen carriers in the electron transport chain

26
Q

Where does the electron transport chain occur?

A

Cristae

27
Q

Describe the processes that cause ATP to be formed in the electron transport chain.

A
  • Hydrogens from glycolysis and the Krebs cycle combine with NAD and FAD (coenzymes)
  • Reduced NAD and FAD donate the electrons of the hydrogens that they are carrying to the first molecule in the electron transport chain
  • This releases protons from the hydrogen atoms which are actively transported across the inner mitochondrial membrane
  • Electrons pass down a chain of electron transport carrier molecules in a series of oxidation and reduction reactions
  • As the electrons pass down the chain, they lose energy which is used to synthesise ATP by combining ADP with Pi (the remaining energy is released in the form of heat)
  • Protons accumulate in the space between the two mitochondrial membranes and diffuse back into the mitochondrial matrix through ATPase which synthesises ATP
  • At the end of the chain, the electrons combine with protons and oxygen (the terminal electron acceptor) to form water
28
Q

Briefly describe the importance of oxygen in the electron transport chain

A
  • It is the terminal electron acceptor and also accepts protons to form water.
  • Without it accepting hydrogen atoms (formed from the combination of the protons and electrons) hydrogen ions and electrons would accumulate and ‘back up’ along the chain and the process of respiration would come to a halt.
29
Q

What happens when oxygen is not available for respiration?

A

The Krebs cycle and the electron transport chain can no longer take place

30
Q

Why can’t the Krebs cycle take place under anaerobic conditions?

A

It requires products from the electron transport chain (which cannot occur in the absence of oxygen)

31
Q

What must be removed in order for glycolysis to continue to occur in anaerobic conditions and why?

A

Pyruvate and hydrogen must be removed for glycolysis to continue- in particular hydrogen must be released from the NADH (reduced NAD) to reform NAD

Otherwise there will be no NAD to accept the hydrogen newly produced by glycolysis

32
Q

How is the replenishment of NAD achieved in glycolysis in anaerobic conditions?

A

Pyruvate accepts the hydrogen from reduced NAD (NADH)

33
Q

What are the two types of anaerobic respiration?

A
  • In plants and microorganisms (eg yeast) pyruvate is converted into ethanol and carbon dioxide
  • In animals, pyruvate is converted into lactate (lactic acid)
34
Q

What is the equation for anaerobic respiration in plants and microorganisms?

A

Reduced NAD + pyruvate –> ethanol + CO2 + NAD

35
Q

What is the equation for anaerobic respiration in animals?

A

Pyruvate + reduced NAD –> lactate + NAD

36
Q

Although glycolysis is an anaerobic process and does not require oxygen, why would glycolysis eventually cease in the absence of oxygen?

A

Reduced NAD would accumulate

37
Q

What happens after anaerobic respiration when oxygen becomes available again?

A

Lactate is oxidised back to pyruvate and can be further oxidised to release energy or converted into glycogen

38
Q

Why in anaerobic respiration can the Krebs cycle and the electron transport chain not occur?

A

Pyruvate is converted into either lactate or ethanol and carbon dioxide so is not available for the Krebs cycle so therefore neither it nor the ETC can occur

39
Q

What happens to the triple phosphate molecules at the end of glycolysis to convert it into pyruvate?

A

Hydrogen is lost from each TP molecule, the triode phosphate is oxidised. The hydrogen passes to NAD to form NADH (reduced NAD). This removal of hydrogen produces pyruvate

40
Q

Describe what happens in the link reaction in terms of addition, release, combination etc of molecules with pyruvate.

A

Pyruvate enters the mitochondrion. Pyruvate is combined with Coenzyme A to form a 2C compound called Acetylcoenzyme A
Carvin dioxide and hydrogen are removed from pyruvate by decarboxylase and dehydrogenase enzymes

41
Q

Describe what is combined with what etc in the Krebs cycle

A 
Acetylcoenzyme A (2C) is combined with oxaloacete (4C) to form a 6C compound.
CO2 is released. The hydrogen removed is passed to NAD and FAD causing them to become reduced NAD and reduced FAD
4C oxaloacetate is regenerated and the cycle starts again
42
Q

How many molecules of ATP generated directly in the Krebs cycle?

A

2

43
Q

Where does the electron transport chain occur?

A

Christae of the mitochondria- inner membrane of the mitochondria

44
Q

Describe anaerobic respiration in yeast.

A

Pyruvate is decarboxylated to produce ethanal. Ethanal accepts the hydrogen from NADH to form ethanol. NAD produced can be reused in glycolysis

45
Q

How many NADH are produced per molecule of glucose?

A

10

46
Q

How many FADH are produced per molecule of glucose?

A

2

47
Q

What is the advantage of having a system of enzyme controlled reactions to transfer energy from food?

A

Allows controlled release of energy in small useful quantities

48
Q

How do the electron carriers in the electron transport chain set up a chemiosmotic gradient?

A

Energy released from electrons used to pump H+ into the intermembrane space. Large difference in concentration of H+ across the membrane and a large electrical difference. Intermembrane space more positive than the matrix

49
Q

What is the effect of lactate build up in the cells of mammals?

A

Enzymes don’t work as efficiently as the pH is reduced (more acidic)
Substrate no longer binds to active site
Glycolysis reactions inhibited

50
Q

Do NADH and FADH use the same proteins in the electron transport chain? Explain.

A

NADH arrives at complex I donating a H+ molecule and reverting back to NAD. H splits and the electron binds briefly to complex I, reducing it. H+ ions pumped into intermembrane space

FADH arrives at complex II, donating it’s hydrogen which splits and the electron binds to complex II, H+ pumped across

51
Q
  • Respiration in an animal*
  • Occurs in the mitochondria
  • Carbon dioxide produced
  • NAD is reduced

Which of the statements above apply for these stages of respiration
>Glycolysis
>Link reaction
>Krebs cycle

Hint: State which statements occur in which stages of respiration

A

Glycolysis:
>NAD is reduced

Link reaction:
>Occurs in mitochondria
>Carbon dioxide produced
>NAD is reduced

Krebs cycle:
>Occurs in mitochondria
>Carbon dioxide produced
>NAD is reduced

52
Q

(2 marks)
Explain why the scientist did not use glucose as the respiratory substrate for an experiment using
isolated mitochondria and used pyruvate instead.

A 
1. Glucose is used/broken down
during glycolysis/in cytoplasm;
2. Glucose cannot cross
mitochondrial membrane(s) /
pyruvate can cross mitochondrial
membrane(s)
53
Q

(3 marks)
Explain how an increase in the iguana’s body temperature affects its oxygen
consumption when it is at rest.

A
  1. (Increased temperature) increases rate of reactions /
    increases kinetic energy / increases metabolism;
  2. More energy/more ATP;
  3. Oxygen consumption linked to respiration;
54
Q 
(3 marks)
Which statements are correct:
-ATP produced
-Occurs in organelles
-Electron transport chain involved

about these 3 processes:

  • Photosynthesis
  • Anaerobic respiration
  • Aerobic respiration
A

Photosynthesis:
>ATP produced
>Occurs in organelles
>Electron transport chain involved

Anaerobic respiration:
>ATP produced
>(Does not occur in an organelle as anaerobic respiration utilises glycolysis which occurs in the cytoplasm)
>(Electron transport chain inhibited as no oxygen to act as terminal electron acceptor)

Aerobic respiration:
>ATP produced
>Occurs in organelles
>Electron transport chain involved

55
Q

(2 marks)
Give two ways in which the properties of ATP make it a suitable source of energy in
biological processes.

A
  1. Energy released in small/suitable amounts;
  2. Soluble;
  3. Involves a single/simple reaction;
56
Q

(2 marks)
Humans synthesise more than their body mass of ATP each day. Explain why it is
necessary for them to synthesise such a large amount of ATP

A
  1. ATP is unstable;
  2. ATP cannot be stored / is an immediate source of energy;
  3. Named process uses ATP ;
  4. ATP only releases a small amount of energy at a time;
57
Q

(2 marks)
A horse was kept in the field from March to October. During the summer months,
the horse was able to eat more than it needed to meet its minimum daily requirements.
Suggest how the horse used the extra nutrients absorbed.

A
  1. Stored as fat/glycogen/biomass;
  2. Used for growth/movement/reproduction / process involved in
    growth/movement/reproduction;
58
Q

(4 marks)
Describe how the carbon dioxide concentrations at ground level and among the leaves would vary in a forest throughout the day.

A 
1. Correct explanation for
differences between day and
night e.g. photosynthesises
only during the daytime / no
photosynthesis/only respiration
at night;
2. Net carbon dioxide uptake
during the day/in light
OR
No carbon dioxide taken up at
night/in dark / carbon dioxide
released at night/in dark;
3. At ground level more
respiration / in leaves more
photosynthesis;
4. Carbon dioxide produced at
ground level/carbon dioxide
taken up in leaves;

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