Photosynthesis

Bio C5

What is photosynthesis?

-The process by which plants convert light energy into chemical energy to produce food

-Enzyme controlled process

-Equation: 6CO₂ + 6H₂O = C₆H₁₂O₆ + 6O₂

Chloroplasts

-Double membrane

-Outer membrane is permeable to ions, inner is less permeable (transport proteins)

-Inner membrane is folded into thin plates (thylakoids)

-Plates are stacked like coins (granum)

Structure of chloroplast

-Stroma - fluid matrix inside a chloroplast, contains enzymes for the light independent stage

-Grana - stacks of thylakoids —> where light is absorbed & ATP is synthesises during the light dependent stage

Adaptations of chloroplasts:

-Inner membrane transport proteins - control substances entering the stroma

-Many grana —> increase SA

-Photosynthetic pigments - arranged in photostems

-Stroma —> enzymes, starch grains, oil droplets, DNA, ribosomes

What are the stages of photosynthesis?

-Light dependent & light independent/calvin cycle

Light dependent:

-Takes place on the inner membranes of the chloroplast

-Requires light

-Chlorophyll traps light energy & uses it to produce ATP, and to split water into hydrogen ions & oxygen gas

Light independent

-Reactions take place in the fluid matrix of the chloroplast

-ATP made during the light-independent stage provides the energy needed to combine carbon dioxide with hydrogen ions, to produce glucose & water

What factors affect photosynthesis?

-CO2 availability

-Light intensity & wavelength

-Temperature (only in the light-independent reaction)

-Water availability

-Chlorophyll

What is chemosynthesis?

-The process by which food (glucose) is made by bacteria using chemicals as the energy source rather than sunlight

C3 plants:

-Examples: barley, oats, rice, wheat, cotton, eucalyptus

-Fix carbon from CO2 into 3 carbon sugars

-Warmer climates

C4 plants:

-Examples: corn, sugarcane

-Cooler climates

CAM plants:

-Examples: succulents & cacti

-Plants with an adaptation to very arid conditions