Bioenergetics

Question 1

What is photosynthesis

Answer 1

An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.

Question 2

What part of the plant does photosynthesis occur

Answer 2

The leaves
As they contain chlorophyll which absorbs light energy

Question 3

What is the word equation for photosynthesis

Answer 3

Carbon dioxide + water —> glucose + oxygen

Question 4

What is the chemical formula for glucose

Answer 4

C6H12O6

Question 5

Explain the effect of light intensity on the rate of photosynthesis

Answer 5

As the light intensity increases the rate of photosynthesis increases
This is because the plant has more light energy to carry out the photosynthesis reaction, so the reaction gets faster
If we increase the light intensity and the rate of photosynthesis also increases that tells us that the light intensity was limiting
This tells us photosynthesis was not as fast as it could’ve been because there was not enough light
If we keep increasing the light intensity there comes a point where the rate of photosynthesis no longer increases
This means light intensity is no longer the limiting factor and something else is

Question 6

Explain the effect of co2 levels on the rate of photosynthesis

Answer 6

As we increase the co2 level, the rate of photosynthesis increases
This tells us that co2 is the limiting factor
At a certain point the rate of photosynthesis no longer increases
This tells us co2 is no longer the limiting factor

Question 7

Explain how the amount of chlorophyll in the leaf can affect the rate of photosynthesis

Answer 7

Leaves with less chlorophyll trap less light energy than normal leaves
This means they will have a lower rate of photosynthesis

Question 8

Explain how temperature can affect the rate of photosynthesis

Answer 8

As we increase the temperature the enzymes involved in photosynthesis work faster so the rate increases
If we keep increasing the temperature, the enzymes will denature and the rate of photosynthesis falls

Question 9

Describe how glucose produced in photosynthesis is used

Answer 9

To release energy in respiration which takes place in the mitochondria
To produce the insoluble storage molecule starch. This can be converted back to glucose by the plant when it’s needed .
Used to produce fat or oil for storage
Used to produce cellulose, which strengthens the cell wall
Used to produce amino acids for protein synthesis, in order to produce proteins plants need to use nitrate ions that are absorbed from the soil

Question 10

Explain how greenhouses are used to increase the rate of photosynthesis

Answer 10

Farmers want to increase the rate of photosynthesis as this increases the yield of crops they produce
To do this, farmers light and heat their greenhouses. They also add extra carbon dioxide
The extra cost has to be justified by the increase in yield
Some gardeners use oil burners as these release heat and carbon dioxide at the same time

Question 11

What is respiration

Answer 11

Respiration is an exothermic reaction because it releases energy
Respiration takes place continually in all living cells

Question 12

Aerobic respiration word equation

Answer 12

Glucose + oxygen —> carbon dioxide + water

Question 13

Anaerobic respiration word equation

Answer 13

Glucose —> Lactic acid

Question 14

What’s the difference between anaerobic and aerobic respiration

Answer 14

Anaerobic respiration releases much less energy than aerobic respiration.
This is because in anaerobic respiration the oxidation of glucose is incomplete

Question 15

Anaerobic respiration in plant and yeast cells word equation

Answer 15

Glucose —> ethanol + carbon dioxide

Question 16

What is fermentation

Answer 16

Anaerobic respiration in yeast cells
We use this reaction to produce alcoholic drinks
We also use yeast to make bread, the carbon dioxide produced by fermentation is useful in bread
This creates bubbles in the dough causing the bread to rise

Question 17

Describe what happens in the body during exercise

Answer 17

The body reacts to the increased demand for energy
The heart rate, breathing rate,man’s breath volume increase to supply the muscles with more oxygenated blood.

Question 18

What happens when insufficient oxygen is supplied during exercise

Answer 18

Anaerobic respiration takes places in the muscles
The incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt.
During long periods of vigorous activity, the lactic acid causes the muscles to become fatigued and stop contracting efficiently

Question 19

Describe the process of oxygen debt

Answer 19

Lactic acid is transported out of the muscles by the blood
The lactic acid is then taken to the liver and converted back to glucose in a series of chemical reactions
This process requires oxygen
The oxygen debt is the amount of extra oxygen the body needs after exercise to deal with the accumulated lactic acid.
This is why people breathe rapidly after exercise

Question 20

What is metabolism

Answer 20

Metabolism is the sum of all the reactions in a cell or the body

Question 21

Give examples of metabolic reactions

Answer 21

Conversion of glucose to starch, glycogen to cellulose glucose and nitrate ions react to form amino acids which are used in protein synthesis
1 glycerol molecule reacts with 3 fatty acid molecules to make lipid molecule which is found in the cell membrane
Excess proteins are broken down into urea which is then excreted by the kidneys