B8 / B9 Photosynthesis And Respiration

Question 1

Why is light needed for photosynthesis?

Answer 1

• transfer energy
• because photosynthesis is an endothermic reaction

Question 2

Balanced equation for photosynthesis

Answer 2

6COtwo + 6HtwoO ——> CsixHtwelveOsix + 6Otwo

Question 3

Describe how a student should make accurate measurements to obtain valid results
for the rate of photosynthesis (pondweed experiment)

Answer 3

• allow pondweed to equilibriate in the light (leave for a few minutes) before measuring
• measure time oxygen/gas is collected for using a timer or stopwatch
• use a measuring cylinder or gas syringe to collect and measure oxygen/gas produced
• repeat all measurements and calculate the mean

Question 4

Respiration in plant and animal cells

Answer 4

• process is identical

Question 5

What is the maximum efficiency of aerobic respiration?

Answer 5

• 40-50%

Question 6

Functions of respiration

Answer 6

• to transport molecules against concentration gradients
• to maintain a constant environment in cells/body temperature
• muscle contraction
• chemical reactions (energy for this)

Question 7

What can respire anaerobically ?

Answer 7

• Yeast

Question 8

Where does the process of anaerobic respiration occur?

Answer 8

• cytoplasm

Question 9

What type of respiration produces more energy per glucose molecule?

Answer 9

• aerobic

Question 10

What is produced when a plant respires anaerobically?

Answer 10

• alcohol and carbon dioxide

Question 11

What is the product of a break down of amino acids?

Answer 11

Urea

Question 12

Why is yeast used to make bread?

Answer 12

Carbon dioxide produced by anaerobic respiration makes the dough rise.

Question 13

What happens to a supreme athlete after exercise?

Answer 13

• Lactic acid is taken to the liver in the blood

Question 14

What type of reaction is respiration?

Answer 14

Exothermic

Question 15

Explain the effect of increasing temperature on the pondweed investigation

Answer 15

• bubbles will increase
• because enzymes will work faster

Question 16

How could you improve the pondweed investigation so temperature does not increase?

Answer 16

• put the tube in a thermostatically controlled water bath
• place a piece of glass between the lamp and tube/pondweed

Question 17

Yeast fermentation practical - explain why more gas was produced when kept at 35 degrees

Answer 17

• 2 degrees is too cold so enzymes are slower fermentation did not occur/was very slow
• enzymes become active at 35 degrees so CO2 is produced