9. Respiration

Question 1

What is respiration ?

Answer 1

A series of chemical reactions that convert energy from glucose into ATP.

Question 2

Name 5 uses of energy (ATP) for cellular processes?

Answer 2

• Muscle cell contraction
• Cell division
• Transmission of nerve impulses
• Protein synthesis
• ACTIVE TRANSPORT

Question 3

What does ATP stand for?

Answer 3

Adenosine Tri Phosphate

Question 4

What is ATP made up of ?

Answer 4

1x adenosine + 3 x Inorganic phosphates

Question 5

Why is ATP important?

Answer 5

ATP is the way a cell ‘transfers’ energy from one place to another. The more ATP, the more energy available.

ATP is a very high energy molecule

Energy is releases each time the bond of the 3rd phosphate is broken

Question 6

What are the 2 types of respiration ?

Answer 6

1. Aerobic Respiration
2. Fermentation

Question 7

What is meant by aerobic?

Answer 7

Requires oxygen

Question 8

When will cells follow a fermentation pathway?

Answer 8

When oxygen is absent

Question 9

How many stages does aerobic respiration occur in?

Answer 9

2 stages

Question 10

How many molecules of ATP does aerobic respiration generate in total per molecule of glucose?

Answer 10

38ATP per glucose

2 from stage 1
36 from stage 2

You do not need to remember the exact amount. Stage 1 releases 2 ATP and stage 2 lots!!!

Question 11

What is the equation for aerobic respiration?

Answer 11

glucose+oxygen —–> carbon dioxide+water (+38ATP)

Question 12

What is the organelle involved in aerobic respiration?

Answer 12

mitochondria

Question 13

What is stage 1 of aerobic respiration called?

Answer 13

Stage1: Glycolysis = The breakdown of glucose

Question 14

Where does Stage 1 (glycolysis) of respiration take place?

Answer 14

In the cytoplasm

Question 15

What does stage 1 (glycolysis) of resiration not require?

Answer 15

It doesn’t require oxygen

Question 16

How much ATP is generated during Stage 1(glycolysis)?

Answer 16

2ATP

Question 17

Describe Stage 1 (glycolysis) using a diagram and a word equation?

Answer 17

• The 6 Carbon glucose is split into 2 x 3 carbon molecules called pyruvate, producing 2xATP
• Glucose ——-> Pyruvate + 2ATP
• This is an enzyem dependant reaction

This requires no oxygen and takes place in the cytoplasm

Question 18

What is the second stage of aerobic respiration known as?

Answer 18

Stage 2 is the complete breakdown of pyruvate

Also known as the Kreb’s cycle

Question 19

Where does Stage 2 of respiration take place?

Answer 19

In the Mitochondria

Question 20

What is required for Stage 2 of respiration (Kreb’s cycle) to proceed?

Answer 20

Oxygen must be present

Question 21

How much ATP is generated during Stage 2 of aerobic respiration?

Answer 21

36ATP (18 per pyruvate)

At Nat 5 it is acceptiabe to say lots!

Question 22

Describe Stage 2 of respiration (Kreb’s Cycle) using a diagram and a word equation?What is the equation for Kreb’s cycle?

Answer 22

• If oxygen is present, aerobic respiration takes place, and each pyruvate is broken down to carbon dioxide and water, releasing enough energy to yield a large number of ATP molecules.
• Pyruvate + Oxygen -> carbon dioxide + water + ATP

This takes place in the mitochondria

Question 23

What is the mitochondria?

Answer 23

A organelle which ist he site of aerobic respiration

Question 24

What do cells that need a lots of energy have?

Answer 24

A large number of mitochondria

Question 25

Give examples of cells that have a lots of mitochondria and need lots of energy? (3)

Answer 25

Sperm cells Muscle cells Nerve cells

Question 26

Explain why muscle cells need many mitochondria. (2 marks)

Answer 26

Muscle cells need energy to do mechanical work and respond quickly. Thus a higher number of mitochondria are present in muscle cells to produce many ATP so that they have the energy required for movement.

Question 27

What is the name given to the apparatus which measures the rate of respiration?

Answer 27

A respirometer

Question 28

Explain why there is a chemical to absorb carbon dioxide. | This experiment measures the respiration rate in germinating peas.

Answer 28

This neutralizes the carbon dioxide and excludes it from affecting the respirometer.

Question 29

Why will the coloured liquid start to rise as respiration occurs in the peas? | This experiment measures the respiration rate in germinating peas.

Answer 29

As germinating peas start to grow, they need more ATP, do cellular respiration more, and consequently consume more oxygen compared to non-germinating peas. This changes the volume of gas in the tube (more space now) which causes the liquid to be sucked up.

Question 31

Describe what fermentation is?

Answer 31

* This is how living cells produce ATP when oxygen is NOT AVAILABLE. * Fermentation is not as efficient as aerobic respiration. It does not produce as much ATP. * The breakdown of each glucose molecule via the fermentation pathway yields only 2 molecules of ATP.

Question 32

Why do organisms need fermentation?

Answer 32

Fermentation is still needed by organisms, for example when the lungs can’t provide enough oxygen during exercise or when a plant is growing in waterlogged soil.

Question 33

Describe fermentation in animal cells with the word equation.

Answer 33

* In animal cells, stage 1 happens as normal, but in the absence of oxygen the pyruvate molecules are converted to LACTATE (incomplete breakdown of glucose) * Word equation: Glucose <--> lactate + 2 ATP * This is reversible meaning if the oxygen debt is repaid lactate can be converted back to puruvate and aerobic respiration could proceed as normal. * Occurs in cytoplasm * Ineffificient 2 ATP are produced from stage 1 only.

Question 34

What effect does a build up of lactate have on muscles?

Answer 34

Makes them feel sore and fatique and eventually cramp

Question 35

Describe fermentation in plant (yeast) cells with the word equation.

Answer 35

* In plant and yeast cells stage 1 happens as normal, but in the absence of oxygen the pyruvate molecules are converted to CARBON DIOXIDE and ETHANOL. (incomplete breakdown of glucose) * Word equation: Glucose --> carbon dioxide + ethanol + 2ATP * This is IRREVERSABLE even if the oxygen became available once ethanol is made, it is permanent and CANNOT be converted back to lactate. * Occurs in cytoplasm * Ineffificient 2 ATP are produced from stage 1 only.

Question 36

Compare aerobic respiration and fermentation in humans. (4 marks)

Answer 36

* Aerobic respiration requires oxygen to take place, fermentation does not require oxygen. * Both processes use glucose to produce ATP but aerobic respiration produces a lot more ATP. * Both processes make pyruvate, this is converted to lactate in fermentation but carbon dioxide and water are produced in aerobic respiration. * Fermentation takes place in the cytoplasm, however, aerobic respiration occurs mainly in the mitochondria.

Question 37

Describe 2 differences between fermentation in plant or yeast cells and animal cells

Answer 37

1. The end product of fermentation in animal cells is lactate for plant or yeast cells the end products are Ethanol and carbon dioxide. 2. Fermentation in animal cells produces lactate but the reaction is reversible, so if the oxygen debt is repaid lactate can ve converted back to pyruvate and enter the aerobic pathway. In plants or yeast once ethanol and Carbon dioxide is made this is irreversable/permanent.

Question 38

Name product S and waste product T. | Look at the diagram which shows fermentation in plant cells.

Answer 38

S = Pyruvate T = Ethanol

Question 39

Identify which of the two stages releases the larger quantity of ATP.

Answer 39

STAGE 1 Releases 2 ATP, Stage 2 yields none.

Question 40

As we know respiration is a series of enzyme controlled steps. What other factor controls the rate of respiration?

Answer 40

Temperature The process of respiration is controlled by specific enzymes so is affected by the temperature of the cell environment.

Question 41

What will happen to the rate of respiration if the temperature of a cell is increased to a very high value?

Answer 41

If the temperature of a cell is increased to a very high value the rate of respiration will decrease. The process of respiration is controlled by enzymes and enzyme activity will decrease to zero as it is DENATURED at very high temperatures.