CO 7

Chapter 7

Photosynthesis

Photosynthetic Organisms

1. *Organic molecules are built by

photosynthesis.

2. Plants use the raw materials:

carbon dioxide and water.

3. Chloroplasts carry out

photosynthesis.

*What is an organic molecule?

Structure of a Leaf

Openings in the leaf allow for the

exchange of gasses. Guard cells

open and close these openings.

Make up the

vessels in

the plant to

transport

water and

food

The Structure of Chloroplasts

Figure 7.2

Photosynthetic Pigments - Pigments found in chlorophyll absorb

various portions of visible light; absorption spectrum.

1. Two major photosynthetic pigments are chlorophyll a and chlorophyll b.

2. Both chlorophylls absorb violet, blue, and red wavelengths best.

3. Most green is reflected back; this is why leaves appear green.

Carotenoids are

yellow-orange

pigments which

absorb light in violet,

blue, and green

regions.

4. When chlorophyll

breaks down in fall,

the yellow-orange

pigments in leaves

are visible.

Absorption Spectrum - spectrophotometer measures the

amount of light that passes through a sample of pigments (like

crushed green leaves)

Action Spectrum - measures the rate of photosynthesis

at different wavelengths of light; measured by the rate

oxygen is produced

In one sentence summarize what this graph says about wavelengths,

color of light, absorption and photosynthesis.

Checkpoint

1. What is the relationship between the absorption spectrum and the

action spectrum?

2. How can we measure the rate of photosynthesis?

3. How is the wavelength of light related to the rate of photosynthesis?

4. A radish plant is grown

using lights of different

colors. Explain the chart.

Photosynthetic Reaction

6CO2 + 6H2O ------> C6H12O6 + 6O2

Two Sets of Reactions in Photosynthesis

1. Light reactions cannot take place unless light is

present. They are the energy-capturing reactions.

a. Water is split

b. ATP and

NADPH are

produced to

power the Calvin

Cycle

c. Oxygen is

released

2. Calvin Cycle Reactions

a. These reactions take

place in the stroma; can

occur in either the light or

the dark.

b. These are synthesis

reactions that use NADPH

and ATP to reduce CO2.

-- and make a

carbohydrate, sugar

The Light Reactions occurs in two systems: Photosystem I

and II - the creation of ATP is a complicated process

You will take a closer look at Photosystem I and Photosystem

II in the Photosystem Coloring Worksheet

Are you still confused? This is pretty

hard to visualize, but through the magic

of technology, we can watch these

processes as animations

McGraw Hill Animation

Forest Biology - The Light Reactions

The Calvin Cycle

- Light Independent Reactions

- The “Dark” Reaction

Occurs in 3 Phases

1. Fixation

2. Reduction

3. Regeneration

Fortunately....

Summary Statements:

What is the purpose of the Calvin

Cycle?

Where does the cell get its energy to

perform these reactions?

What is the final product?

Why is carbon dioxide necessary?

AP Biology no longer requires the

memorization of every step of the Calvin

Cycle, but you should understand the

beginning and the end and what it's

purpose is.

What Factors the Affect Photosynthesis?

1. Light Quality (color)

2. Light intensity

3. Light Period

4. Carbon Dioxide Availability

5. Water Availability

*Design an experiment to test ONE of the above factors*

Rate of Photosynthesis can be measured by the amount of

oxygen released or the amount of CO2 absorbed.

Photosynthesis

Simulation

Waterweed

Simulator

Quick Practice

Quick Practice

thylakoid

O2

stroma

grana

Pg 129b

Light & H2O

O2

CO2

glucose

ATP

NADPH

ADP

NADP

A = photosystem II

B = photosystem I

C = H20

D = Electron Transport Chain

E = ATP Synthase

AB = ATP

AC = phospholipids

AD = light (energy)