4.2 Overview of Photosynthesis

Season 3: Respiration, Photosynthesis,

and Fermentation

Episode 1: Function of the Chloroplast

Objective: Describe the chloroplasts' role in

photosynthesis and what is produced.

4.2 Overview of Photosynthesis

KEY CONCEPT

The overall process of photosynthesis produces

sugars that store chemical energy.

4.2 Overview of Photosynthesis

Gamma

raysX-rays UV Infrared

Micro-

waves

Radio

waves

Visible light

Wavelength (nm)

Why are plants green?

• Different wavelengths of visible light are seen by the

human eye as different colors

4.2 Overview of Photosynthesis

• Pigments absorb

certain wavelengths

of light and reflect

others.

4.2 Overview of Photosynthesis

• What color of light do

green plants use for

photosynthesis???

4.2 Overview of Photosynthesis

• Plant cells contain

the photosynthetic

pigment chlorophyll

• Found in chloroplasts

4.2 Overview of Photosynthesis

The chemical energy used for most cell processes is

carried by ATP.

• Molecules in food store chemical energy in their bonds.

• Photosynthesis creates sugars that is later used to

make ATP.

Starch molecule

Glucose molecule

4.2 Overview of Photosynthesis

Photosynthesis occurs in the chloroplast.

• The chloroplast is made of

two parts.

– Thylakoids: Like

stacks of pancakes

– Stroma: the syrup you

put on those yummy

pancakes

chloroplast

stroma

grana (thylakoids)

4.2 Overview of Photosynthesis

• The light-dependent reactions capture sunlight.

– Uses water and sunlight, creates ATP

– Occurs in the thylakoid membrane

Photosynthesis has two main steps.

4.2 Overview of Photosynthesis

• The light-independent (Calvin cycle) reactions make

sugars.

– Uses carbon dioxide and ATP, creates glucose

– Occurs in the stroma

4.2 Overview of Photosynthesis

• The equation for the overall process is:

6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6

granum (stack of thylakoids)

thylakoid

1 six-carbon sugar

6H2O

6CO2

6O2

chloroplast1

2

43

energy

stroma (fluid outside the thylakoids)

4.2 Overview of Photosynthesis

4.2 Overview of Photosynthesis

• Pg. 104

• Fill in the blanks

• Color and give a written description of photosynthesis and

function of chloroplast

• 15 min.

4.2 Overview of Photosynthesis

• Draw two circles

• Make a wet mount with elodea leaf

• Start with low power, focus and then move to medium and

high. Draw a picture for each.

• Label and include magnification

4.2 Overview of Photosynthesis

• Around how many chloroplasts were in one leaf cell?

Now estimate around how many leaf cells were in the

entire leaf you observed, keeping in mind that the leaf is

three cell layers thick. Based on these two estimations,

predict how many chloroplasts would be in the picture of

the elodea plant that is on the front of this page. SHOW

ALL YOUR MATH!

• Chloroplasts are responsible for harvesting light energy

and transferring this energy to a usable form: sugar.

Consider your estimation of the number of chloroplasts in

the elodea plant. In relative terms, what does your

estimation tell you about the amount of energy a single

chloroplast can make? (Do you think it makes a lot of

energy?) Explain why plants have so many leaves