Photosynthesis

• Process plants utilise to produce their own food

• Take in: water and carbon dioxide• Produce: oxygen and glucose

(light energy)carbon dioxide + water glucose + oxygen

(chlorophyll)

(light energy)6CO2 + 6H2O C6H12O6 + 6O2

(chlorophyll)

But how does it all happen?

First: look at the leaf structure.....

cuticle

upper epidermis

palisade mesophyll

spongy mesophyll

air pocket

lower epidermis

guard cellstoma

phloem

xylem

cuticle

sunlight

H 2O

Light-dependent reaction: -light energy converted to chemical energy -water split into oxygen and hydrogen

H+

O2CO2

C6H12O6

Light-independent reaction: hydrogen from water and carbon dioxide react to form glucose

(light energy)6CO2 + 6H2O C6H12O6 + 6O2

(chlorophyll)

How do plants use glucose?

• Convert into cellulose for growth• Convert to other sugars to transport to other

parts of the plant• To produce oils and proteins• Convert to starch for temporary storage in the

leaf (on sunny days when photosynthesis rate is very high)

• Convert back into energy via respiration

carbon dioxide + water glucose + oxygen

= respiration!

Conditions Photosynthesis v respiration Overall result

DarkRespiration No photosynthesis

Oxygen taken in Carbon dioxide given out

Dim lightPhotosynthesis rate equals respiration rate

Neither gas is taken in or given out as each cancels the other out

Bright lightPhotosynthesis rate greater than respiration rate

Carbon dioxide taken in Oxygen given out

What determines the rate of a plant’s respiration and photosynthesis?