Topic 6 - 6.1 To 6.6 Photosynthesis

Question 1

What is photosynthesis?

Answer 1

A chemical reaction that takes place inside photosynthesis organisms (eg plants, algae) converting light energy into chemical energy

Question 2

Write the word equation for photosynthesis

Answer 2

Carbon dioxide + water - arrow - glucose + oxygen

Question 3

Write the symbol equation for photosynthesis

Answer 3

6CO(2) + 6H(2)O - C(6)H(12)O(6)+6O(2)

() numbers in brackets are subscript

Question 4

Why is photosynthesis important?

Answer 4

It produces glucose which has a wide range of uses:
Used in respiration to release energy
Converted to starch and stored - broken down to glucose when the plant requires energy
Used to make complex organic molecules which are used for growth, making up an organism’s biomass (transferred through food chains)

Question 5

Where does photosynthesis take place?

Answer 5

Within chloroplasts

Question 6

What type of reaction is photosynthesis?

Answer 6

An endothermic reaction that takes in energy (in the form of light)

Question 7

What is chlorophyll?

Answer 7

A pigment found in chloroplasts that absorbs light

Question 8

Describe the 2 main stage of photosynthesis

Answer 8

Chlorophyll absorbs light energy which is used to split water into oxygen gas (waste product) and hydrogen ions

Carbon dioxide combines with hydrogen ions to form glucose

Question 9

What factors affect the rate of photosynthesis

Answer 9

Temperature
Light intensity
Carbon dioxide concentration

Question 10

What is a limiting factor?

Answer 10

A variable that limits the rate of a particular reaction.

Question 11

Explain how temperature affects the rate of photosynthesis

Answer 11

Higher temperatures provide more KE for enzymes involved in photosynthesis so the rate increases as temperature rises

The optimum temperature is usually 25oC

If the temperature becomes too high (around 45oC) enzymes become denatured and the rate of photosynthesis decreases

Question 12

Draw a graph to show the effect of increasing temperature on the rate of photosynthesis

Question 13

Explain how light intensity affects the rate of photosynthesis.

Answer 13

Rate of photosynthesis is directly proportional to light intensity, therefore as light intensity increases, the rate of photosynthesis increases.

Question 14

Why does the rate of photosynthesis eventually plateau even if light intensity continues to increase? (Higher)

Answer 14

Another factor (temperature or Co2 concentration) becomes limiting.

Question 15

Draw a graph to show the effect of light intensity on the rate of photosynthesis

Question 16

How can the effect of light intensity on the rate of photosynthesis be measured in the lab (2)? Higher

Answer 16

Using a light meter
Using the inverse square law where:
Light intensity x (funny squiggal) 1 over distance 2 (superscript)

Question 17

Why does the rate of photosynthesis decrease as the distance from a light source increases (higher)?

Answer 17

Light intensity is inversely proportional to the square of the distance from the light source. Thus, as the distance increases, light intensity decreases and the rate of photosynthesis decreases.

Question 18

Explain how carbon dioxide concentration affects the rate of photosynthesis

Answer 18

As carbon dioxide concentration increases, the rate of photosynthesis increases

Question 19

Why does the rate of photosynthesis eventually plateau even if CO2 concentration continues to increase? (Higher)

Answer 19

Another factor (temperature or light intensity) becomes limiting.

Question 20

Draw a graph to show the effect of carbon dioxide concentration on the rate of photosynthesis.