Topic 2.9: Photosynthesis

Question 1

Definition of photosynthesis

Answer 1

Process by which cells synthesize organic compounds from inorganic molecules using light energy

Question 2

Chemical equation of photosynthesis

Answer 2

6CO2 + 12H2O + Light => C6H12O2 + 6O2

Question 3

Definition of electromagnetic spectrum

Answer 3

Range of all possible frequencies of electromagnetic radiation

Question 4

Relationship between wavelength and energy

Answer 4

The shorter the wavelength, the greater the energy

Question 5

Wavelength range of visible light

Answer 5

400 – 700 nm

Question 6

Function of chlorophyll

Answer 6

Pigment responsible for the absorption of light and its conversion into chemical energy (ATP)

Question 7

Light absorption and reflection of chlorophyll

Answer 7

a) Absorption of blue and red light most effectively

b) Reflection of green light more than other colors

Question 8

Photosynthesis => Type of reaction

Answer 8

a) Endothermic

b) Anabolic

Question 9

Steps in photosynthesis

Answer 9

a) Light dependent reactions

b) Light independent reactions

Question 10

Purpose of light dependent reactions

Answer 10

Light is converted into chemical energy

Question 11

What happens in light dependent reactions?

Answer 11

a) Light is absorbed by chlorophyll to produce ATP

b) Photolysis of water forms oxygen and hydrogen

Question 12

Purpose of light independent reactions

Answer 12

Carbon compounds are made from chemical energy

Question 13

What happens in light independent reactions?

Answer 13

ATP and hydrogen are fixed with carbon dioxide

Question 14

Definition of chromatography

Answer 14

Experimental technique by which mixtures can be separated

Question 15

Procedure of chromatography

Answer 15

a) A mixture is dissolved in a fluid and passed through a static material
b) The different components of the mixture travel at different speeds, causing them to separate
c) A retardation factor is calculated

Question 16

Consequences of photosynthesis on Earth in Oceans

Answer 16

a) Oxidation of dissolved iron in water

b) Precipitation of iron oxide, creating banded iron formations

Question 17

Consequences of photosynthesis on Earth in Atmosphere

Answer 17

a) Rise in oxygen concentration to 20%

b) Formation of ozone layer, protecting Earth from UV radiation

Question 18

Limiting factors of photosynthesis

Answer 18

a) CO2
b) Light intensity
c) Temperature

Question 19

CO2 as a limiting factor

Answer 19

a) CO2 is involved in the fixation of carbon to form organic molecules
b) Increasing CO2 concentration increases the rate of photosynthesis, until the enzymes involved in the Calvin cycle reach their saturation point and can no longer increase reaction rates.

Question 20

Temperature as a limiting factor

Answer 20

a) Photosynthesis is controlled by enzymes, which are sensitive to temperature fluctuations
b) As temperature increases reaction rate will increase, as reactants have greater kinetic energy and more collisions result
c) Above a certain temperature the rate of photosynthesis will decrease as essential enzymes begin to denature

Question 21

Light intensity as a limiting factor

Answer 21

a) Light is absorbed by chlorophyll, which converts the radiant energy into chemical energy (ATP)
b) As light intensity increases, reaction rate will increase since more chlorophyll are being photoactivated
c) At a certain light intensity photosynthetic rate will plateau, as all available chlorophyll are saturated with light

Question 22

Ways to measure rate of photosynthesis

Answer 22

a) Measuring CO2 uptake
b) Measuring O2 production
c) Measuring Biomass

Question 23

Measuring CO2 uptake

Answer 23

a) CO2 uptake can be measured by placing leaf tissue in an enclosed space with water
b) Water free of dissolved CO2 can be produced by oiling and cooling water
c) CO2 interacts with H2O molecules, producing bicarbonate and H+, which changes the pH
d) Increased uptake of CO2 by the plant will lower the concentration in solution and increase the alkalinity

Question 24

Measuring O2 production

Answer 24

a) O2 production can be measured by submerging a plant in an enclosed water filled space attached to a sealed gas syringe
b) Any oxygen gas produced will bubble out of solution and can be measured by a change in meniscus level on the syringe

Question 25

Measuring biomass

Answer 25

a) Glucose production can be indirectly measured by a change in the plant’s biomass (weight)
b) This requires the plant tissue to be completely dehydrated prior to weighing to ensure the change in biomass represents organic matter and not water content

Question 26

Pigments in plants

Answer 26

Chlorophyll
Carotene
Xanthophyll

Question 27

Definition of limiting factor

Answer 27

Factor nearest its minimum/furthest from its optimum that increasing it while maintaining other factors constant increases reaction rate