photosynthesis

what is photosynthesis

the process by which plants synthesise glucose using light energy from the sun. light energy is converted into chemical energy.

where does photosynthesis take place

within chloroplasts in leaf palisade cells

state the equation for photosynthesis (word and symbol)

word: carbon dioxide + water →glucose + oxygen

symbol: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

is photosynthesis an endo or exothermic reaction, and why

endo because energy is transferred from the environment to chloroplasts by light

how can you show that a plant gives off oxygen during photosynthesis

using a water plant (eg. Elodea), collect gas bubbles produced during photosynthesis. this gas will relight a glowing splint as it contains oxygen.

give examples of leaf adaptations which maximise the rate of photosynthesis

broad leaves - maximise surface area

thin leaves - short diffusion distance

chlorophyll present - trap light energy

what are the four main factors that affect the rate of photosynthesis

temperature

light intensity

carbon dioxide concentration

amount of chlorophyll

how does temperature affect the rate of photosynthesis

increasing the temperature increases the rate of photosynthesis as the kinetic energy of particles is increased. the rate decreases past a certain temperature as enzymes become denatured

how does light intensity affect the rate of photosynthesis

increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting

how does carbon dioxide concentration affect the rate of photosynthesis

increasing the carbon dioxide concentration increases the rate of photosynthesis (until another factor be limiting) as CO₂

How does the amount of chlorophyll affect the rate of photosynthesis

decreasing the amount of chlorophyll (eg. due to a lack of magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy

what is a limiting factor

an environmental factor which can restrict the rate of photosynthesis eg. light intensity

Explain how you can calculate the rate of

photosynthesis by measuring oxygen

production

Set up bubble potometer apparatus (pondweed in a

sealed tube of water, attached to a capillary tube and a

gas syringe).

Oxygen gas produced causes the bubble in the capillary

tube to move. The distance moved by the bubble is used

to calculate the volume of oxygen produced.

How can farmers use their knowledge of

limiting factors to increase their profits?

(higher)

They can control temperature, light intensity

and CO2 concentration to achieve the fastest

possible rate of photosynthesis, leading to a

greater yield.

State the law which describes the

relationship between the distance of a

light source from a plant and light

intensity (higher)

Inverse square law - light intensity∝1 /

distance2

State 5 uses of the glucose produced

during photosynthesis

● Respiration

● Starch for storage

● Cellulose for strength

● Amino acid and protein synthesis (combined with

nitrates)

● Lipids for energy storage in seeds