Bioenergetics

Question 1

What is the chemical equation for aerobic respiration?
[1 mark]

Answer 1

6O2 + C6H12O6 –> 6H2O + 6CO2

Question 2

Energy is released in respiration.
Give two uses of the energy released in respiration.
[ 2 marks]

Answer 2

• movement / muscle contraction
• keeping warm
• active transport
• building larger molecules

Question 3

Describe two differences in anaerobic and aerobic respiration in humans. Do not refer to oxygen.
[2 marks]

Answer 3

• anaerobic produces lactic
  acid and aerobic does not
• aerobic produces carbon dioxide and anaerobic does not
• aerobic produces water and anaerobic does not
• aerobic occurs (mainly) in the mitochondria and anaerobic does not
• anaerobic releases less energy than aerobic

Question 4

What are the two products of anaerobic respiration in plant cells?
[2 marks]

Answer 4

-Ethanol
-Carbon Dioxide

Question 5

A gardener wants to add compost to the soil to increase his yield of strawberries. The gardener wants to make his own compost.
An airtight compost heap causes anaerobic decay.
Explain why the gardener might be against producing compost using this method. [2 marks]

Answer 5

-methane is produced
-which is a greenhouse gas

Question 6

Some of the leaves from the gardener’s strawberry plant die.
The dead leaves fall off the strawberry plant onto the ground.
The carbon in the dead leaves is recycled through the carbon cycle.
Explain how the carbon is recycled into the growth of new leaves. [6 marks]

Answer 6

-dead leaves are broken down by microorganisms / decomposers / bacteria / fungi

• (microorganisms) respire
  -(and) release the carbon from the leaves as carbon dioxide
  -plants take in the carbon dioxide released to use in photosynthesis to produce glucose

-glucose produced in photosynthesis is used to make amino acids / proteins / cellulose
- (which are) required for the growth of new leaves

Question 7

What conditions increase the rate of decaying?

Answer 7

• (at) higher temperature / hotter
• (had) more oxygen
• (had) more water / moisture
• (contained) more microorganisms (that cause decay)

Question 8

Plants can use the glucose they have made to supply them with energy. Give four other ways in which plants use the glucose they have made.
[4 marks]

Answer 8

-(to make) starch (for storage)
-(to make) fat / oil (for storage)
-(to make) amino acids / proteins / enzymes
-(to make) cellulose / cell walls

Question 9

Plants need energy to make glucose.
How do plants get this energy?
[2 marks]

Answer 9

-Light is trapped
-by chloroplasts (for photosynthesis)

Question 10

Why would oxygen produced by plants cause them to rise to the surface in a liquid?

Answer 10

-Oxygen produced by plant during photosynthesis can create gas bubbles, which create buoyancy and cause the leaves to rise to the surface of the liquid
-Helps plants access sunlight

Question 11

Describe how the products of photosynthesis are used by a plant. [6 marks]

Answer 11

-glucose is the product of photosynthesis
-some glucose is used for respiration by the plant’s cells
-starch is built up and stored in the plant’s cells, including those of storage organs
-starch can be broken down and the glucose used when it is needed, eg for respiration during the germination of seeds
-some glucose is converted into cellulose, used to construct cell walls
-glucose is converted into amino acids, with the help of nitrates absorbed from the soil
-amino acids built into proteins
glucose is converted into lipids, eg used as an energy store in seeds