Chapter 4

•Photosynthesis

• Photosynthesis is the process by which certain organisms use light energy• To make sugar and oxygen gas from carbon dioxide and water

• What does it need? (Input)• What does it make? (Output)

Lightenergy

PHOTOSYNTHESIS

6 CO2 6+ H2O

Carbon dioxide Water

C6H12O6 6+ O2

Glucose Oxygen gas

Trophic Roles• Autotrophs

Producers of the biosphere:

• produce organic molecules from CO2 & inorganic raw materials

• Heterotrophs consumers

Learning Target

1. Describe Oxidation & Reduction reactions

REDOX Reactions

LEO th

e Lio

n Say

s GER

OIL RIG

REDOX Reactions

• Oxidation• When a compound loses electrons

• Reduction• When a compound gains electrons

• CO2 + H2O + energy → C6H12O6 + O2

• CO2 is reduced to form glucose• Water is oxidized to form O2

OIL

RIG

•Photosynthesis is a redox process, as is cellular respiration

• In photosynthesis• H2O is oxidized and CO2 is reduced

Figure 7.4A, B Reduction

Oxidation

6 O2 6 H2O

Reduction

Oxidation

6 O26 CO2 6 H2O C6H12O6

C6H12O6 6 CO2

Learning Check

• If H2O is losing electrons than it is being reduced/oxidized

• Co2 is being reduced/oxidized, which means it is gaining/losing electrons.

Photosynthesis Overview

• Light reactions• Depend on light• Occur in Thylakoid

Membrane

• Light Independent (“Dark”) reactions

• Does NOT need light• Occurs in the Stroma