Chapter 7: PHOTOSYNTHESIS

[Pages:22]Chapter 7: PHOTOSYNTHESIS

1. Overview of Photosynthesis 2. The "Light" Reactions 3. The "Dark" Reactions

1. Overview of Photosynthesis

What is Photosynthesis?

The process of converting light energy (kinetic) into energy stored in the covalent bonds of glucose molecules (potential).

6 CO2 + 6 H2O

Light energy

Carbon dioxide

Water PHOTOSYNTHESIS

C6H12O6 + 6 O2

Glucose

Oxygen gas

? carried out by photoautotrophs

? plants, phytoplankton, cyanobacteria (any photosynthetic organism)

? the basis of almost all ecosystems

? all "food energy" ultimately comes from the sun ? source of all atmospheric oxygen (O2)

Photosynthesis vs Respiration

essentially the reverse

of each other

Photosynthesis occurs in Chloroplasts

Leaf

Leaf Cross Section

Mesophyll Cell

CO2 O2

Chloroplast

Chloroplast

The Chloroplast

outer membrane inner membrane

stroma thylakoid

granum

Photosynthesis consists of 2 sets of Reactions

The light-dependent or "Light" Reactions:

Light

H2O

CO2

Chloroplast

NADP+

ADP +P

LIGHT REACTIONS (in thylakoids)

Electrons

ATP NADPH

CALVIN CYCLE (in stroma)

O

Sugar

? convert sunlight energy into chemical energy (stored in ATP & NADPH)

"Dark" Reactions (Calvin cycle):

? use chemical energy from light reactions to make glucose

2. Light-dependent ("Light") Reactions

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