Photosynthesis: the basis… Mrs.JAckie. State the photosynthesis involves the conversion of light energy into chemical energy Light is converted into chemical.

Photosynthesis: the Photosynthesis: the basis…basis…Mrs.JAckie

State the photosynthesis involves State the photosynthesis involves the conversion of light energy into the conversion of light energy into chemical energychemical energy

Light is converted into chemical energy.

The substances needed for photosynthesis are carbon dioxide and water

In the presence of sunlight and chlorophyll these substances can produced glucose and oxygen

State that white light from the sun State that white light from the sun is composed of a range of is composed of a range of wavelenghts (colors)wavelenghts (colors)The most usual light

for photosynthesis is sunlight

Is white light made of all color together.

Different colors are actually different wavelengths of light.

Chlorophyll is the main Chlorophyll is the main photosynthetic pigmentphotosynthetic pigmentMost plants are greenThe green color is caused by

the presence of the pigment chlorophyll.

It reflects green light and absorbs all other colors.

Different types of chlorophyll exist, each with their own specific absorption spectrum

Outline the differences in Outline the differences in absorption of red, blue and absorption of red, blue and green light by chlorophyllgreen light by chlorophyll

Orange-red light and blue light are mostly absorbed while green light is reflected.

Not all pigments contribute efficiently to photosynthesis

State that light energy is used to State that light energy is used to split water molecules to give split water molecules to give oxygen and to produced ATPoxygen and to produced ATP

During photosynthesis light energy is used to split water molecules (photolysis) into hydrogen ion H+, oxygen and electrons producing ATP.

This is called the light dependent stage.

ATP and hydrogen are used to fix ATP and hydrogen are used to fix carbon dioxide to make organic carbon dioxide to make organic moleculesmolecules

The H+ and ATP produced drive the formation of glucose from CO2

Water is formedThis is called the light

independent stage

Two stages of Two stages of PhotosynthesisPhotosynthesis

12 H2O + light 24H+ + 24electrons 18 ATP + 12 NADPH2

6O2

18ADP + 18Pi12NADP+

Calvin Cycle

6CO2

Used in forming

C6H12O6 + H2OLight Independent Stage

Used in formingLight

dependent

Rate of photosynthesis can me measured Rate of photosynthesis can me measured directly by the production of oxygen or the directly by the production of oxygen or the uptake of CO2 or by the increase of biomassuptake of CO2 or by the increase of biomassIt is possible to allow the carbon

dioxide to interact with water, producing bicarbonate and hydrogen ions.

The acidity of the solution will indicate the amount of CO2

Or it is possible to measure how much oxygen the plant produces over time

Or possible to measure change in organic matter that is the weight of the plant afer dehydration occurs.

Outline the effects of temperature, Outline the effects of temperature, light intensity and carbon dioxide light intensity and carbon dioxide concentration on the rate of concentration on the rate of photosynthesisphotosynthesisTo allow photosynthesis to take

place the following criteria need to be fulfilled◦Presence of chlorophyll◦Light◦Carbon dioxide◦Water◦temperature

Outline the effects of temperature, light Outline the effects of temperature, light intensity and carbon dioxide intensity and carbon dioxide concentration on the rate of concentration on the rate of photosynthesisphotosynthesisIn practical work it is possible to

determine if all the factors are required for photosynthesis by observing◦The glucose during photosynthesis is

turned to starch◦A plant can be destarched by placing it in a

dark cupboard for 2 days◦During the experiment photosynthesis may

or may no take place◦Presence of starch can be tested for in a

simple test involving the use of iodine

Effects of temp, light and Effects of temp, light and CO2CO2Chlorophyll requirement

◦Using a destarched plant with variegated leaves (green and white) and placing it in the light will show that the white parts contain no starch a day later

◦Showing the need for chlorophyll in the process

Effects of …Effects of …Temperature

◦The enzymes involved in photosynthesis have temperature ranges in which they are most effective

◦These vary from enzyme to enzyme

◦The rate is higher at the optimum temperature and lower at both low and high temperature

Effect of….Effect of….CO2 requirement

◦If two destarched plants are placed in the light but covered with a transparent plastic bag, one with soda-lime (NAOH) When the plants are tested for

starch the plant with soda lime will have had no photosynthesis

The other plant will show starch This indicate the need for

photosynthesis