Respiration 3.5.2

Question 1

What is respiration

Answer 1

Respiration is the conversion of chemical energy in substrates (eg, glucose) into chemical energy in ATP.

Question 2

Aerobic

Answer 2

Aerobic respiration requires oxygen and forms the waste products CO2 and H2O.

Question 3

Anaerobic

Answer 3

Anaerobic respiration is in the absence of oxygen forms the waste produces ethanol and CO2 in bacteria and lactic acid in animals.

Question 4

Mitochondria structure

Answer 4

• Site of aerobic respiration within eukaryotic cells.
• Bound by a double membrane structure. Outer membrane is permeable to small molecules and ions. Inner membrane is impermeable to most materials.
• A semi-rigid matrix is enclosed by the inner membrane. The matrix contains many enzymes, DNA and ribosomes.
• Inner membrane is folded into a number of cristae. These increase the surface area to provide lots of space for enzymes and electron carriers.
• The inter membrane space between the 2 membranes is important in maintain proton gradients.

Question 5

Mitochondria labelled

Answer 5

Check word doc

Question 6

Glycolysis

Answer 6

1. Activation - make glucose reactive by phosphorylations using 2ATP - ADP + Pi.
2. Splitting - splits into 2x triose phosphate.
3. Oxidation - e- and p+ are picked up by NAD (coenzyme) (NAD-NADH) (ADP + PI - ATP).
4. Substrate level phosphorylation - phosphate donated to ADP triose phosphate oxidised into pyruvate.

Overall - 2x pyruvate, 2x NADH, 2x ATP

Takes place in the cytoplasm.

Question 7

Link reaction

Answer 7

1. Pyruvate is decarboxylated - removal of CO2.
2. Pyruvate is oxidised, donating electrons to coenzyme NAD.
3. These result in acetyl group that combines with CoA to form acetyl coenzyme A which enters the kerbs cycle.

Overall - 2x CO2, 2x NADH, 2x acetyl-coenzyme

Takes place in the mitochondrial matrix.

Question 8

Link reaction diagram

Answer 8

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Question 9

Krebs cycle

Answer 9

1. Acetyl coenzyme A combines with 4C compound = 6C compound.
2. The 6C compound is decarboxylated releasing CO2. 6C compound also oxidised releasing H2 which are picked up by NAD. This makes 5C compound.
3. 5C decarboxylated releasing CO2 and oxidised, released 3H2 - 2 pairs picked up by NAD and other pair by FAD.
4. 2NAD to 2NADH and FAD to FADH2.
5. ATP made by substrate level phosphorylation.
6. This cycle regenerates 4C compound.
   Overall - 4CO2, 6NADH, 2FADH2, 2ATP

The Krebs cycle can also be called the citric acid cycle.

The Krebs cycle takes place in the mitochondrial matrix.

Question 10

Krebs cycle diagram

Answer 10

Check word doc

Question 11

When is decarboxylated and dehydrogenase enzyme used in respiration? (Glycolysis, Link, Krebs)

Answer 11

Glycolysis - dehydrogenase

Link - dehydrogenase and decarboxylase

Krebs - dehydrogenase and decarboxylase

Question 12

Electron transfer chain

Answer 12

1. Coenzymes NAD and reduced FAD released H+ and e-.
2. The electrons move down ETC in a series of redox reactions that release energy.
3. This energy pumps protons across the inner mitochondrial membrane by AT to the inter membrane space.
4. Proton gradient present in IMM
5. Protons diffuse back into matrix through ATP synthase (ADP + Pi = ATP - oxidative phosphorylation).
6. Oxygen is the final e- acceptor (1/2O2 + 2H+ + 2e-).

Question 13

Electron transfer chain alternative name and explanation of what is is

Answer 13

The electron transport chain is also referred to as oxidative phosphorylation.

A chain of protein complexes embedded in the cristae in which the energy released in the passage of electrons from one molecule to the next is used to produce ATP.

Question 14

Electron transfer chain graph

Answer 14

Check word doc

Question 15

Importance of NAD and FAD

Answer 15

These co-enzymes help enzymes to function by carrying hydrogen atoms from one molecule to another. These hydrogen atoms are donated to the ETChain, allowing for ATP to be made.

• 1 reduced NAD makes 3 ATP
• 1 reduced FAD makes 2 ATP

Question 16

ATP breakdown (how many ATP’s are made in each step)

Answer 16

Glycolysis (8ATP)
Link reaction (6ATP)
Krebs cycle (24ATP)

Overall = 38ATP.

Question 17

NAD and FAD activity investigation

Answer 17

The activity of coenzymes (NAD and FAD) can be investigated using methylene blue. This dye can accept hydrogen atoms so becomes reduced. Reduced methylene blue becomes colourless.

• Add the methylene blue to a suspension containing yeast cells and glucose. The yeast will respire and hydrogen will be produced. The methylene blue picks up the hydrogen and becomes reduced (blue to colourless). Record the time taken for solution to become colourless – determines rate of respiration.

Question 18

Importance of oxygen in respiration

Answer 18

Oxygen is the final electron acceptor. It combines with protons and electrons to form water. Without its role at the end of the chain, the protons and electrons would ‘back up’ and respiration would stop.

Question 19

Cyanide in respiration

Answer 19

Cyanide is a respiration poison and is lethal because it’s a non-competitive inhibitor of the final enzyme in the ETC. This causes protons and electrons to accumulate on the carriers, stopping respiration and killing the organism.

Question 20

Alternative respiratory substrates

Answer 20

Sugars aren’t the only substance that can be used as a respiratory substrate (oxidised to release energy. Both lipids and proteins can, under certain circumstances, be used without first being converted into carbohydrates.

Question 21

Respiration of proteins

Answer 21

Proteins hydrolysed into AA.

Deaminatoon = the removal of amino group to form keto acids.

Can enter in Krebs cycle or as acetyl coA.

Question 22

Respiration Lipids

Answer 22

Hydrolysis of fats to glycerol and fatty acids.

Glycerol converted into TP by phosphorylation and enters glycolysis.

Fatty acids converted into acetyl coA by beta oxidation.

Question 23

Respiratory quotient - anaerobic glucose

Answer 23

Less than 1

Question 24

Respiratory quotient - aerobic carbohydrate

Answer 24

1

Question 25

Respiratory quotient - aerobic protein

Answer 25

Approx 0.9

Question 26

Respiratory quotient - aerobic lipid

Answer 26

Approx 0.7

Question 27

Anaerobic respiration (bacteria)

Answer 27

In bacteria, fungi (yeast), some cells of higher plans such as root cells in waterlogged soils.

• Pyruvate + NADH —> ethanol + CO2 + NAD

Question 28

Anaerobic respiration (animals)

Answer 28

• Pyruvate + NADH —> lactate + NAD

This is most common in muscles during strenuous exercise where O2 is used up quicker than it can be supplied so oxygen debt occurs. At some point the lactate has to be removed from muscle cells by the blood and oxidised back into pyruvate to prevent fatigue.

Pyruvate can then enter the Krebs cycle and be fully oxidised to CO2 and H2O, releasing many more ATP molecules or is converted into glycogen in the liver. This occurs when O2 is available again.