Topic 4- Bioenergetics

Question 1

What is photosynthesis?

Answer 1

Photosynthesis is the process by which plants make glucose from sunlight

Question 2

Where does photosynthesis take place?

Answer 2

Within chloroplasts in leaf palisade cells. They contain chlorophyll, a pigment which absorbs light energy

Question 3

State the word equation for photosynthesis

Answer 3

Carbon dioxide + water —(light)—> glucose + oxygen

Question 4

State the symbol equation for photosynthesis

Answer 4

CO2 + H2O —> c6H12O6 + O2

Question 5

Is photosynthesis an endothermic or exothermic reaction and why?

Answer 5

It is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light

Question 6

How can you show that a plant gives off oxygen during photosynthesis?

Answer 6

Using a water plant like Elodea

Collect gas bubbles produced during photosynthesis

The gas will relight a glowing splint as it contains oxygen

Question 7

What do you have to do in order to carry out an experiment measuring the oxygen production of a plant?

Answer 7

Pond weed is placed in a test tube full with water

The top is sealed with a bung

A capillary tube also containing water leads into the tube and it is attached to a syringe

A lamp is placed at a measured distance from the tube

As it photosynthesises, oxygen is produced, forming a gas tube in the capillary tube

The distance the bubble has moved is measured using a ruler to calculate the volume of oxygen produced

Question 8

How does temperature affect the rate of photosynthesis?

Answer 8

With an increase in temp, the rate of photosynthesis increases as the kinetic energy of particles is increased.

As the reaction is controlled by enzymes , this trend continues up to a certain temperature until the enzymes begin to denature and the rate of reaction decreases

Question 9

How does light intensity affect the rate of photosynthesis?

Answer 9

For most plants, the higher the light intensity, the faster the rate of reaction

Question 10

How does carbon dioxide concentration affect the rate of photosynthesis?

Answer 10

Carbon dioxide is also needed to make glucose

As the concentration of carbon dioxide increases, the rate of reaction increases

Question 11

How does amount of chlorophyll affect the rate of photosynthesis?

Answer 11

Chlorophyll is a pigment in the leaf that converts light energy to food for the plant and is therefore essential

If, for example, chlorophyll levels are reduced through a magnesium deficiency, then the rate of photosynthesis would decrease

Question 12

Give examples of leaf adaptations which maximise the rate of photosynthesis

Answer 12

Broad leaves - maximise surface area

Thin leaves - short diffusion distance

Guard cells- control opening of stomata for gaseous exchange and prevent water loss

Chlorophyll present - trap light energy

Question 13

What is a limiting factor?

Answer 13

An environmental factor which can restrict the rate of photosynthesis e.g light intensity

Question 14

How can farmers use their knowledge of limiting factors to increase their profits?

Answer 14

They can control temperature, light intensity and CO2 concentration to achieve the fastest possible rate of photosynthesis, leading to a greater yield

Question 15

State 5 uses of the glucose produced during photosynthesis

Answer 15

Respiration

Starch for storage

Cellulose for strength

Amino acid and protein synthesis (combined with nitrates)

Lipids for energy storage in seeds

Question 16

What is aerobic respiration?

Answer 16

An exothermic reaction which glucose reacts with oxygen to release energy which can be used by cells

Question 17

What are the equations for aerobic respiration?

Answer 17

Glucose + Oxygen —> carbon dioxide + water (+ energy)

C6H12O6 + 6O2 —-> 6CO2 + 6H2O

Question 18

Where does aerobic respiration take place?

Answer 18

In the mitochondria

Question 19

Why do organisms require the energy released by respiration?

Answer 19

Synthesis of larger molecules

Muscle contraction

Maintenance of body temperature

Active transport

Question 20

What is anaerobic respiration?

Answer 20

An exothermic reaction in which glucose is broken down to release energy in the absence of oxygen

Question 21

What is the equation for anaerobic respiration?

Answer 21

Glucose —> lactic acid (+energy)

Question 22

Why is anaerobic respiration less efficient than aerobic respiration?

Answer 22

Glucose is not completely broken down, so less energy is transferred

Question 23

Why can anaerobic respiration lead to muscle fatigue?

Answer 23

Lactic acid (product of anaerobic respiration) builds up in muscles, preventing efficient contraction

Question 24

What is fermentation?

Answer 24

A type of anaerobic respiration that occurs in yeast cells

Question 25

What is the equation for fermentation?

Answer 25

Glucose —> ethanol + carbon dioxide (+energy)

Question 26

Why is the fermentation reaction important?

Answer 26

It is used in the production of bread and alcoholic drinks

Question 27

What are the differences between aerobic and anaerobic respiration?

Answer 27

Aerobic requires oxygen ; anaerobic does not

Aerobic produces CO2 and water; anaerobic produces lactic acid or ethanol + CO2

Aerobic transfers a greater amount of energy

Question 28

How do muscles store glucose?

Answer 28

As glycogen

Question 29

What is metabolism?

Answer 29

The sum of all the reactions that take place in a cell or an organism

Question 30

How do cells use the energy transferred by respiration?

Answer 30

To continuously carry out enzyme-controlled processes which lead to the synthesis of new molecules

Question 31

Give examples of metabolic reactions

Answer 31

Glucose into starch/glycogen/cellulose

Glycerol and fatty acids into lipids

Glucose and nitrate ions into amino acids

Photosynthesis

Respiration

Breakdown of excess proteins into urea