Chapter 10 Photosynthesis

Photosynthesis

Ps General Equation

Requires:

Question

Does the Oxygen in sugar come from the CO2 or from the H2O ?

Model:

CO2 + 2 H2O ----> CH2O + O2

Proof Used 18O as a tracer.

CO2 + 2 H2O ----> CH2O + O2

CO2 + 2 H2O ----> CH2O + O2

Ps: a redox process

Ps

Light

Too Hot Too Cold

Just Right

Action Spectrum

Comment

In oceans, red light is lost or filtered out early because it has lower energy.

Only blue light which has higher energy can reach the lower depths.

Result

Many deep ocean fish are bright red in color.

Why? They can’t be seen because

there is no red light to reflect their color.

Photosynthesis Pigments

Chlorophylls

Accessory Pigments

Fall Leaf Colors

Chloroplast Structure

Photosystems

Cyclic Photophosphorylation

Noncyclic Photophsphorylation

Light Reaction

Light Reaction

Location –

Function

Light Reaction

Requirements Products

Chemiosmosis Model

Chemiosmosis

Comment

There can be a 3 pH unit difference between the thylakoid space and the stroma.

Dark Reactions

Dark Reaction

Rubisco

C3 Ps

Requirements Products

Photorespiration

Photorespiration

Alternate Ps Methods

1. C4 Ps

2. CAM Ps

C4 Ps

PEP Carboxylase

C4 Ps

C3 Ps vs C4 Ps

Photorespiration

Shade to full sun

High water use

Cool temperatures

Slow to moderate growth rates

Cool season crops

No Photorespiration

Full sun only

Moderate water use

Warm temperatures

Very fast growth rates

Warm season crops

CAM Ps

CAM Ps

CAM plants

Ps:Rs Ratios Reflect a plant’s balance in

making food and using food.1. Ps > Rs, energy available

for growth and reproduction.2. Ps = Rs, no growth, but don’t

die either.3. Ps < Rs, death by starvation

Comments - Ps:Rs

Factors That Affect Ps

1

Importances of Ps

Summary

Know the main Ps equation. Know Light Reaction. Know Dark Reaction. Alternate Ps forms. Ps:Rs ratios.