Chapter 8

Photosynthesis

I. Photosynthesis

A. Structure of a Chloroplast1. has an inner and an outer membrane. 2. The inner membrane encloses a thick fluid

called stroma.a. Suspended in the stroma are many disk-shaped sacs

called thylakoids. b. The thylakoids are arranged in stacks called grana c. Photosynthesis takes place in the thylakoid

membranes, and in the stroma

3. Chlorophyll is a green pigment in the chloroplast that captures the sunlight to use during photosynthesis

B. Overview of Photosynthesis1. 6CO2 + 6H2O →→→ C6H12O6 + 6O2

2. Occurs in 2 main stagesa. Light reactionb. The Calvin Cycle

3. 1st step of energy flow through an ecosystem

4. It is the ultimate source of all food we eat and air we breathe

II. Light Reactions

A. Light energy and Pigments1. Electromagnetic Spectrum

a. Describes light waves based on their wavelength

b. The visible light are the only wavelengths we can see- ROY G BIV

2. Pigmentsa. Gives a substance colorb. You see color when light shines on a

substance and reflects that visible wavelength back to your eye for you to see.

c. The pigment chlorophyll absorbs red and blue wavelengths very well.

It does not absorb green light.

B. The Light Reactions1. Converts sun light energy into

chemical energyH2O + sunlight → ATP + NADPH + O2

2. Occurs in the membrane of the thylakoid

3. Requires light to begin

4. Steps in light reactions1st step: chlorophyll captures sunlight energy2nd step: “water splitting photosystem”- chloroplasts use the sun’s energy to remove electrons from H2O by “splitting” the water.

(O2 is the waste product and escapes through holes in the leaves called stomata)

3rd step: “NADPH- producing photosystem”- chloroplasts use the H+ and e- to make NADPH and the sun light to make ATP.

The ETS moves e- from the water splitting photosystem to the NADPH producing photosystem.

III. The Calvin Cycle

A. The Calvin Cycle1. Uses the energy from NADPH to make

glucose2. This happens in the stroma3. This does not require light to begin

4. Makes 3- carbon compounds called G3P.

5. The plant cell uses G3P to make glucose

6. Must go through the cycle many times during photosynthesisCO2 + ATP + NADPH → C6H12O6

Task Listpg. 233 picture in notesTest correction & reflection for BOTH Ch. 7 tests! get signed for ThursdayColor & add captions on handoutHW: Read 8.3 & G.R.

IV. Global Impact

A. Carbon Cycle1. Consumers release CO2 into

atmosphere during cellular respiration producers remove CO2

2. Producers remove CO2 from the atmosphere during photosynthesis consumers eat producers

B. Greenhouse Effect1. More CO2 is being put into the

atmosphere than is being removed by producers

2. The excess gasses get trapped in the atmosphere and heated by sunlight.

3. The heated gasses increase the overall temperature of the earth and atmosphere

C. Factors that affect photosynthesis1. Temperature- enzymes work best between 0-35℃2. Light Intensity3. Water Availability 4. pH of soil & water (acid rain)CO2 availability