b4: bioeneergetics

Question 1

What is the word equation for photosynthesis?

Answer 1

carbon dioxide + water = glucose + oxygen

Question 2

What is the symbol equation for photosynthesis?

Answer 2

6CO2 + 6H2O → C6H12O6 + 6O2.

Question 3

Where does photosynthesis take place?

Answer 3

Chloroplasts

Question 4

Give five ways that plants can use glucose.

Answer 4

• Respiration
• Making cellulose
• Making amino acids
• Storage as oils or fats
• Storage of starch

Question 5

Give four factors that affect the rate of photosynthesis.

Answer 5

• Light levels
• CO2 concentration
• Temperature
• Amount of chlorophyll

Question 6

Draw a graph of light intensity against photosynthesis rate.

Answer 6

(rate increases with light intensity, then plateaus)

Question 7

Draw a graph of carbon dioxide concentration against photosynthesis rate.

Answer 7

(rate increases with CO2 concentration, then plateaus)

Question 8

Draw a graph of temperature against photosynthesis rate.

Answer 8

(rate increases with temperature, then decreases rapidly)

Question 9

Give the method for a practical that investigates the effect of light intensity on rate of photosynthesis

Answer 9

Draw the apparatus: a cutting of Canadian pondweed in a test tube full of water, attached to a capillary tube that is next to a ruler and attached to a syringe at the other end. A light source is placed facing the plant, and a ruler is used to measure the distance between the setup and the lighting.
1. the pondweed is left to photosynthesise for a set amount of time, and as it does, the oxygen released will collect in the capillary tube.
2. The syringe is then used to draw the gas bubble into the capillary tube, where its length can be measured. The length of the bubble is proportional to the volume of oxygen produced.
3. The experiment is repeated twice again, with the light at the same distance away, and the mean volume of oxygen produced is calculated.
4. Then the whole experiment is repeated several times with the light source at different distances from the pondweed.

Question 10

Is photosynthesis an exothermic or endothermic reaction?

Answer 10

Endothermic.

Question 11

Where does the CO2 used in photosynthesis enter the plant?

Answer 11

Through the stomata.

Question 12

How does the water used in photosynthesis enter the plant?

Answer 12

Through the roots

Question 13

What is the inverse square law that links light intensity and distance?

Answer 13

light intensity = 1/distance^2

Question 14

Define respiration.

Answer 14

Respiration is the continuous process of transferring energy from glucose that takes place in living cells.

Question 15

Is respiration exo- or endothermic?

Answer 15

Exothermic.

Question 16

Give three examples of how organisms use the energy transferred by respiration.

Answer 16

• To build larger molecules from smaller ones, e.g proteins from amino acids.
• To allow muscles to contract, for movement
• To maintain body temperature.

Question 17

Define metabolism.

Answer 17

Metabolism is the sum of all the chemical reactions in an organism.

Question 18

What is the word equation for aerobic respiration?

Answer 18

glucose + oxygen = carbon dioxide + water

Question 19

What is the symbol equation for aerobic respiration?

Answer 19

C6H12O2 + 6O2 = 6CO2 + 6H2O

Question 20

What is the word equation for anaerobic respiration in animals?

Answer 20

glucose = lactic acid

Question 21

Why do animals ‘prefer’ aerobic respiration?

Answer 21

• Aerobic respiration releases more energy than anaerobic
• Anaerobic respiration produces lactic acid, which can cause soreness and cramps.

Question 22

Give the word equation for anaerobic respiration in plants/yeast.

Answer 22

glucose = ethanol + carbon dioxide

Question 23

What is anaerobic respiration is yeast cells called?

Answer 23

Fermentation.

Question 24

How does exercise affect the body?

Answer 24

When we exercise, our bodies need to carry out more respiration because the muscles need the energy from it to contract. Because respiration requires oxygen, the breathing rate increases, as does the volume of each breath. This increased amount of oxygen also needs to be pumped around the body, so the heart rate increases in order to do this.
If the exercise is too vigorous, the body struggles to supply oxygen to the muscles quickly enough, so often anaerobic respiration is used instead. Muscle soreness can occur due to lactic acid build-up, which is formed from the incomplete oxidisation of glucose. This causes an oxygen debt.

Question 25

What is an oxygen debt?

Answer 25

An oxygen debt is the amount of extra oxygen your body needs to react with the build up of lactic acid in the muscles and remove it from cells.

Question 26

Where is lactic acid oxidised?

Answer 26

The liver.