Bioenergetics

Question 1

Give three uses of energy released in respiration.

Answer 1

• Body warmth
• Movement/muscle contraction
• Active transport

Question 2

Give three differences of anaerobic and aerobic respiration in humans.

Answer 2

• Anaerobic releases less energy than aerobic
• Aerobic releases water and carbon dioxide whereas anaerobic does not
• Anaerobic produces lactic acid whereas aerobic does not

Question 3

Why does the death of an animal increase carbon dioxide concentration?

Answer 3

Animal is being decomposed by bacteria/microorganisms. The bacteria respires, releasing CO2.

Question 4

Give three examples of metabolism in the human body.

Answer 4

• 1 glycerol + 3 fatty acids -> lipids
• Glucose converted to insoluble glycogen for storage
• Break down of excess proteins into urea which are excreted in urine

Question 5

Give two uses of fermentation in industry processes.

Answer 5

• Brewing (alcohol production)
• Bread making (CO2 makes bread rise)

Question 6

Compare anaerobic respiration in yeast and muscle cells.

Answer 6

• Yeast cells produce ethanol whereas muscle cells produce lactic acid
• Both release small amounts of energy as incomplete breakdown of glucose
• Yeast cells produce CO2 muscle cells don’t

Question 7

Where does fermentation occur?

Answer 7

In plant and yeast cells.

Question 8

Explain the effect of a leaking valve on exercise.

Answer 8

Backflow of blood may occur (oxygenated and deoxygenated blood mixes together) so less oxygenated blood supplied to muscles so less aerobic respiration meaning less energy released so muscles contract less efficiently. May mean anaerobic respiration occurs which builds up lactic acid which is toxic which can cause cramping, less energy released leading to muscle fatigue. Also, oxygen debt may be caused leading to breathlessness.

Question 9

Why can a low oxygen concentration possibly lead to death in small organisms?

Answer 9

More shallow concentration gradient so less oxygen diffuses in meaning less aerobic respiration so less energy released meaning less metabolism, possibly more anaerobic respiration and so a build up of lactic acid which is toxic (and can lead to death).

Question 10

Photosynthesis RPA (light intensity): control variables (3)

Answer 10

• carbon dioxide concentration
• temperature with a water bath
• length and type of pondweed

Question 11

Explain (2) responses to exercise.

Answer 11

• Breathing rate increases so more fresh oxygen in blood and more carbon dioxide removed
• Heart rate increases to increase blood flow to muscles to provide more oxygen and glucose to muscles
  -> increased heart rate and breathing rate means more oxygen and glucose in muscles for more aerobic respiration to release more energy (for more muscle contraction) also lactic acid removed quicker so less likely to build up meaning less likely to have muscle fatigue

Question 12

Explain why exercise cannot be sustained when anaerobic respiration takes place in muscle cells

Answer 12

Muscles become fatigued so cannot contract efficiently as not enough energy is transferred. Build up of lactic acid can cause cramping.

Question 13

Explain why the leaf left in a cupboard with no light for two days did contain glucose but did not contain starch

Answer 13

Starch has been converted to glucose so glucose can be used for respiration but no light for photosynthesis to produce excess glucose for storage.

Question 14

What does reduced blood flow to the heart muscle result in for the body?

Answer 14

Less oxygen and glucose to the heart muscle so less aerobic respiration meaning less energy is released so less muscle contraction. Lactic acid removed slower so muscle fatigue caused and an oxygen debt, resulting in breathlessness.

Question 15

How does a greater muscle mass affect an athlete?

Answer 15

Contract more with efficiency so release more energy so athletes movement is quicker

Question 16

Why is sodium hydrogen carbonate used rather than just water?

Answer 16

Releases carbon dioxide which is needed for the plant to photosynthesise.

Question 17

What happens to a less dense object in water?

Answer 17

It will move upwards (water more easily displaced)

Question 18

Define an oxygen debt and how it is dealt with.

Answer 18

The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells. This is done by transporting lactic acid through the blood from muscle cells to the liver where it is converted back into glucose. Lactic acid can also be oxidised by reacting with oxygen to form CO2 and H20

Question 19

If insufficient oxygen is supplied to muscles anaerobic respiration takes place, what does this lead to?

Answer 19

The incomplete oxidation of glucose means less energy is released so muscles become fatigued and stop contracting efficiently.
A build up of lactic acid is caused, leading to muscle cramping and creates an oxygen debt leading to breathlessness

Question 20

What is the importance of fatty acids and glycerol?

Answer 20

• Synthesis of lipids
• Fatty acids main products as energy stores

Question 21

Give 5 examples of metabolism

Answer 21

• conversion of glucose to starch, glycogen and cellulose
• the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids
• the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins
• respiration
• breakdown of excess proteins to form urea for excretion

Question 22

Explain why farmers should control temperature in greenhouses

Answer 22

Where there is an optimal rate and can maximise profits. Need to ensure respiration rate is lower as reduces rate of photosynthesis and respiration increases with temperature.

Question 23

Why do farmers use greenhouses?

Answer 23

Control LF to maximise yield of crops and rate of photosynthesis to maximise profits

Question 24

Explain why the metabolic rate of a smaller organism is greater than of a larger one

Answer 24

Smaller organism has a larger surface area to volume ratio so heat will be lost quicker. This means more respiration will be required to release energy for warmth and respiration is a part of metabolism.

Question 25

How would you investigate the effect of light intensity on photosynthesis to get a fair test?

Answer 25

• pondweed in water in beaker
  – shining on light on beaker with lamp at measured distance
  from plant with a ruler, vary length in intervals from 10-50cm
  – control: use same pond weed/ length and control temperature with a water bath and CO2 by controlling concentration of sodium hydrogen carbonate
• leave sufficient time at each new light intensity before measurements taken to allow to photosynthesise
• collect gas released and measure volume with a gas syringe
• repeat at each distance and find a mean

Question 26

RPA 5: control variables (for any)

Answer 26

• type of pondweed/ length of pondweed
• volume of water

Question 27

What 2 measurements must be made to calculate rate of photosynthesis?

Answer 27

• volume of gas bubbles
• time