SIMPLE Photosynthesis

Autotrophs

● Plants & some

other
organisms
that are able
to directly
use sunlight
to produce
food.

Green Plants & Sunlight

● Chlorophyll - the primary light absorbing

pigment found in chloroplasts.
● Absorbs Red and Blue light best
● Reflects green light to make plants appear green

Photosynthesis Reaction

Phases of

Photosynthesis

● 2 Phases

● Light reactions/Light

dependent: “photo” part – traps
sunlight energy [thylakoid]

● Dark reactions/Light

independent: “synthesis” part –
makes glucose by using CO2 &
H2O. [stroma]

Light Reactions

(aka: Light Dependent)

● Light strikes

the
thylakoids &
energy is
transferred
to
ELECTRONS

Thylakoids

Thylakoids

● Thylakoids: compartments that contain

chlorophyll & other pigments

Light Reactions, con’t…

● H2O is broken down in thylakoid.

● Chlorophyll takes hydrogen (H)

electrons from water’s hydrogen
(H) atoms to be used to make ATP.

● Remaining oxygen (O) atoms from

water combine to form O2 gas.

Light Reactions con’t…

●Excited electrons leave the

thylakoid as NADPH (a type

of electron carrier molecule) used
to power the Calvin Cycle
(dark reaction).

● ***NADPH becomes NADP+

when NOT carrying an electron.

Photosynthesis Process

Thylakoid Membranes

Stroma

Dark Reactions

● a.k.a Calvin

Cycle

● a.k.a Light

independent

● Occurs in

stroma.

Dark Reaction

● Carbon dioxide (CO2) is taken in by

plant thru stomata (pores in
leaves).

● CO2 is used to create sugar

(glucose)

Factors that Affect the
Rate of Photosynthesis

● Light Intensity

● Increase light intensity = increase the rate of

photosynthesis to a point & then plateaus (levels
out)

● CO2 concentration

● Once a certain concentration of CO2 is present,

the rate of photosynthesis can’t occur any faster
(plateaus or levels out)

● Temperature

● Unfavorable temps = inactivate certain enzymes

→ rate of photosynthesis slows or stops.
● Temperature can be too hot OR cold.

Factors Affecting the Rate

of Photosynthesis

Photosynthesis Process

Thylakoid Membranes

Stroma