GCSE BIOLOGY HIGHER TIER PAPER 1H
COMPREHENSIVE REVISION GUIDE AND
WORKED SOLUTIONS 2026
◉ photosynthesis in plants and algae is.... Answer: an endothermic
reaction
uses light energy to react carbon dioxide and water to produce
glucose and oxygen
◉ how does temperature affect the rate of photosynthesis? Answer:
as the temperature increases, rate of photosynthesis increases as
there is more energy for the chemical reaction to take place
◉ how can temperature become a limiting factor in photosynthesis?
Answer: photosynthesis is an enzyme controlled reaction
if the temperature increases too much, then the enzymes denature
and the rate of reaction will decrease and stop
◉ how does light intensity affect the rate of photosynthesis?
Answer: as light intensity increases, the rate of photosynthesis
increases as more energy is available for the chemical reaction.
,term-6
the plant can use light energy to convert co2 and water into glucose
and oxygen during photosynthesis
◉ how does light intensity become a limiting factor Answer: graph
line plateaus
another factor is limiting the rate of photosynthesis. this could be
carbon dioxide , amount of chlorophyll or temperature.
◉ how does carbon dioxide concentration affect rate of
photosynthesis Answer: carbon dioxide is a reactant in
photosynthesis, it is needed for plants to make glucose.
therefore, the rate of photosynthesis will increase when a plant is
given a higher concentration of carbon dioxide
◉ how can carbon dioxide concentration become a limiting factor?
Answer: graph line plateaus
another factor is limiting the rate of photosynthesis. this could be
carbon dioxide , amount of chlorophyll or temperature.
,◉ describe a method to Investigate the effect of light intensity on the
rate of photosynthesis Answer: place 20 algal balls and the same
volume of indicator solution in each bottle, and replace the screw
tops
check the colour of the indicator against the colour chart and record
the starting ph
if using a hot lamp, place the water tank next to the lamp to control
temperature
use a metre ruler to place the uncovered bottles at specific distances
from the lamp, on opposite sides of the tank
leave the bottles for 1-2 hours
record distance and ph of each bottle
calculate the rate of change in ph per hour for each bottle
draw a graph of results to show distance against rate of change of ph
, ◉ what are the dependent and independent variables of the light
and photosynthesis experiment Answer: IV- the distance from the
light source
DV- the change in the colour of the indicator. this indicates the
amount of co2 present.
◉ what are the control variables of the light and photosynthesis
experiment Answer: number of algal balls
temperature
volume of indicator
brightness of bulb
size of bottle
same species of algae
◉ in the light and photosynthesis experiment, why does the
indicator change with increasing distance from the light source
Answer: it is yellow in more acidic solutions
it is purple in more alkali solutions
carbon dioxide is an acidic gas
the bottle closest to the light will turn purple as more
photosynthesis will occur and more carbon dioxide will be removed
the bottle furthest away will be more yellow as less carbon dioxide
will have been used due to less photosynthesis occurring
COMPREHENSIVE REVISION GUIDE AND
WORKED SOLUTIONS 2026
◉ photosynthesis in plants and algae is.... Answer: an endothermic
reaction
uses light energy to react carbon dioxide and water to produce
glucose and oxygen
◉ how does temperature affect the rate of photosynthesis? Answer:
as the temperature increases, rate of photosynthesis increases as
there is more energy for the chemical reaction to take place
◉ how can temperature become a limiting factor in photosynthesis?
Answer: photosynthesis is an enzyme controlled reaction
if the temperature increases too much, then the enzymes denature
and the rate of reaction will decrease and stop
◉ how does light intensity affect the rate of photosynthesis?
Answer: as light intensity increases, the rate of photosynthesis
increases as more energy is available for the chemical reaction.
,term-6
the plant can use light energy to convert co2 and water into glucose
and oxygen during photosynthesis
◉ how does light intensity become a limiting factor Answer: graph
line plateaus
another factor is limiting the rate of photosynthesis. this could be
carbon dioxide , amount of chlorophyll or temperature.
◉ how does carbon dioxide concentration affect rate of
photosynthesis Answer: carbon dioxide is a reactant in
photosynthesis, it is needed for plants to make glucose.
therefore, the rate of photosynthesis will increase when a plant is
given a higher concentration of carbon dioxide
◉ how can carbon dioxide concentration become a limiting factor?
Answer: graph line plateaus
another factor is limiting the rate of photosynthesis. this could be
carbon dioxide , amount of chlorophyll or temperature.
,◉ describe a method to Investigate the effect of light intensity on the
rate of photosynthesis Answer: place 20 algal balls and the same
volume of indicator solution in each bottle, and replace the screw
tops
check the colour of the indicator against the colour chart and record
the starting ph
if using a hot lamp, place the water tank next to the lamp to control
temperature
use a metre ruler to place the uncovered bottles at specific distances
from the lamp, on opposite sides of the tank
leave the bottles for 1-2 hours
record distance and ph of each bottle
calculate the rate of change in ph per hour for each bottle
draw a graph of results to show distance against rate of change of ph
, ◉ what are the dependent and independent variables of the light
and photosynthesis experiment Answer: IV- the distance from the
light source
DV- the change in the colour of the indicator. this indicates the
amount of co2 present.
◉ what are the control variables of the light and photosynthesis
experiment Answer: number of algal balls
temperature
volume of indicator
brightness of bulb
size of bottle
same species of algae
◉ in the light and photosynthesis experiment, why does the
indicator change with increasing distance from the light source
Answer: it is yellow in more acidic solutions
it is purple in more alkali solutions
carbon dioxide is an acidic gas
the bottle closest to the light will turn purple as more
photosynthesis will occur and more carbon dioxide will be removed
the bottle furthest away will be more yellow as less carbon dioxide
will have been used due to less photosynthesis occurring
