ATP

Question 1

Describe the roles of calcium ions and ATP in the contraction of a myofibril.

Answer 1

• Calcium ions diffuse into myofibrils from sarcoplasmic reticulum
• Calcium ions cause movement of tropomyosin
• Movement causes exposure of the binding sites on the actin
• Myosin heads attach to binding sites on actin
• Hydrolysis of ATP on myosin heads causes myosin heads to bend

Question 2

ATP is an energy source used in many cell processes.

Give two ways in which ATP is a suitable energy source for cells to use.

Answer 2

• Releases energy instantaneously

- Can be rapidly re-synthesised

Question 3

The table contains statements about three biological processes.

Complete the table with a tick if the statement in the first column is true, for each process.

Photosynthesis:

1 ) ATP produced

2 ) Occurs in organelles

3 ) Electron transport chain involved

Anaerobic respiration:

1 ) ATP produced

2 ) Occurs in organelles

3 ) Electron transport chain involved

Aerobic respiration:

1 ) ATP produced

2 ) Occurs in organelles

3 ) Electron transport chain involved

Answer 3

• Photosynthesis; 1, 2 and 3
• Anaerobic respiration; 1
• Aerobic respiration; 1, 2 and 3

Question 4

Write a simple equation to show how ATP is synthesised from ADP.

Answer 4

• ADP + Pi - > ATP

Question 5

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

Answer 5

• Energy is released in small amounts

- Soluble

Question 6

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.

Answer 6

• ATP cannot be stored

- ATP only releases a small amount of energy at a time

Question 7

Describe the part played by the inner membrane of a mitochondrion in producing ATP.

Answer 7

• Electrons are transferred down the electron transport chain
• Provides energy to take protons into the space between membranes
• Energy is used to combine ADP and phosphate

Question 8

A scientist investigated ATP production in a preparation of isolated mitochondria.
He suspended the mitochondria in an isotonic solution and added a suitable respiratory substrate together with ADP and phosphate.
He bubbled oxygen through the preparation.

Why was the solution in which the mitochondria were suspended isotonic?

Answer 8

• Prevent damage to mitochondria caused by osmosis

Question 9

Explain why the scientist did not use glucose as the respiratory substrate.

( A scientist investigated ATP production in a preparation of isolated mitochondria.
He suspended the mitochondria in an isotonic solution and added a suitable respiratory substrate together with ADP and phosphate.
He bubbled oxygen through the preparation. )

Answer 9

• Glucose is broken down during glycolysis in the cytoplasm

- Glucose cannot cross the mitochondrial membrane

Question 10

Explain why the oxygen concentration would change during this investigation.

( A scientist investigated ATP production in a preparation of isolated mitochondria.
He suspended the mitochondria in an isotonic solution and added a suitable respiratory substrate together with ADP and phosphate.
He bubbled oxygen through the preparation. )

Answer 10

• Terminal acceptor

- ( used to make water )

Question 11

The diagram summarises the process of anaerobic respiration in yeast cells.

( From glucose to pyruvate; 2 ATP is converted to 2 ADP + Pi )
( As 2 ADP and Pi made, 2 NAD is converted to 2 reduced NAD )
( As this happens 4 ADP + Pi is converted to 4 ATP )
( Pyruvate is then converted to ethanol )

In anaerobic respiration, what is the net yield of ATP molecules per molecule of glucose?

Answer 11

• 2 molecules

Question 12

Give two advantages of ATP as an energy-storage molecule within a cell.

Answer 12

• Cannot pass out of the cell

- Easily hydrolysed

Question 13

Describe how NAD is regenerated in anaerobic respiration in yeast cells.

( From glucose to pyruvate; 2 ATP is converted to 2 ADP + Pi )
( As 2 ADP and Pi made, 2 NAD is converted to 2 reduced NAD )
( As this happens 4 ADP + Pi is converted to 4 ATP )
( Pyruvate is then converted to ethanol )

Answer 13

• NAD is produced when reduced NAD is used to reduce H ions to pyruvate

Question 14

Mitochondria in muscle cells have more cristae than mitochondria in skin cells.
Explain the advantage of mitochondria in muscle cells having more cristae.

Answer 14

• Larger surface area for the electron transport chain

- More enzymes for ATP production

Question 15

Substance X enters the mitochondrion from the cytoplasm.
Each molecule of substance X has three carbon atoms.

Name substance X.

Answer 15

• Pyruvate

Question 16

In the link reaction substance X is converted to a substance with molecules effectively containing only two carbon atoms.
Describe what happens in this process.

( X = Pyruvate )

Answer 16

• CO2 is formed

- Hydrogen is released

Question 17

The Krebs cycle, which takes place in the matrix, releases hydrogen ions.
These hydrogen ions provide a source of energy for the synthesis of ATP, using coenzymes and carrier proteins in the inner membrane of the mitochondrion.

Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.

Answer 17

• Hydrogen is attached to NAD
• H^+ ions are transferred from coenzyme to coenzyme
• Energy is made available as electrons are passed on

Question 18

When one mole of glucose is burned, 2800 kJ of energy are released.
However, when one mole of glucose is respired aerobically, only 40% of the energy released is incorporated into ATP.
Each mole of glucose respired aerobically produces 38 moles of ATP.

Calculate how much energy is incorporated into each mole of ATP. Show your working.

Answer 18

• 29.47

Question 19

When glucose is respired what happens to the energy which is not
incorporated into ATP?

Answer 19

• Released as heat

Question 20

When one mole of glucose is respired anaerobically, only 2 moles of ATP are produced.
Explain why less energy is released in anaerobic respiration.

Answer 20

• Glucose is only partly broken down

Question 21

At the end of a sprint race, a runner continues to breathe rapidly for some time.
Explain the advantage of this.

Answer 21

• Lactic acid has built up

- Oxygen is used to break down lactate

Question 22

Name the substance that muscles use as their immediate energy source.

Answer 22

• ATP

Question 23

Sports scientists investigated the change in energy sources used during exercise.
They measured the percentage of energy obtained from carbohydrate and the percentage of energy obtained from fat in two groups of athletes.
• Group A exercised at different intensities for the same time.
• Group B exercised at the same intensity for different times.
They calculated the intensity of the exercise as a percentage of VO2 max.
VO2 max is the maximum volume of oxygen the athletes can take in per minute.

The results for Group A are shown in Figure 1 and the results for Group B are shown in Figure 2.

( Figure 1 shows “ Percentage of energy from different sources “ against “ Intensity of exercise / percentage VO2 max… ( Can’t see the rest ) “ )
( Figure 1 has two graphs, one representing “ carbs “ and the other “ fats “ )
( Both line graphs )
( Which don’t start from zero )
( As “ Intensity of exercise “ increases “ Percentage of energy from fats “ is decreasing )
( As “ Intensity of exercise “ increases “ Percentage of energy from carbs “ is increasing )

( Figure 2 shows “ Percentage of energy from different sources “ against “ How long exercise lasted / min “ )
( Figure 2 has two graphs, one representing “ carbs “ and the other “ fats “ )
( Both line graphs )
( Which don’t start from zero )
( Both graphs start from around the same point )
( As the length of time of exercise increases, fats increases with a decreasing gradient )
( As the length of time of exercise increases, carbs decreases with an increasing gradient )
( Overall both graphs look like a “ C “ shape )

Calculate the ratio of the percentage of energy from carbohydrate to the percentage of energy from fat when the intensity of exercise is 70% VO2 max.
Show your working.

Answer 23

• 72 : 28

- = 2.75 : 1

Question 24

A person wishes to lose some body fat by exercising.
What sort of exercise would be most effective?
Use the information in Figures 1 and 2 to explain your answer.

( Figure 1 shows “ Percentage of energy from different sources “ against “ Intensity of exercise / percentage VO2 max… ( Can’t see the rest ) “ )
( Figure 1 has two graphs, one representing “ carbs “ and the other “ fats “ )
( Both line graphs )
( Which don’t start from zero )
( As “ Intensity of exercise “ increases “ Percentage of energy from fats “ is decreasing )
( As “ Intensity of exercise “ increases “ Percentage of energy from carbs “ is increasing )

( Figure 2 shows “ Percentage of energy from different sources “ against “ How long exercise lasted / min “ )
( Figure 2 has two graphs, one representing “ carbs “ and the other “ fats “ )
( Both line graphs )
( Which don’t start from zero )
( Both graphs start from around the same point )
( As the length of time of exercise increases, fats increases with a decreasing gradient )
( As the length of time of exercise increases, carbs decreases with an increasing gradient )
( Overall both graphs look like a “ C “ shape )

Answer 24

• A low intensity of exercise
• At low intensities, mainly fat is used
• Long duration of exercise
• Percentage of fat used increases over time