PhotosynthesisPhotosynthesis is a process whereby green plants manufacture their own food.

Materials used during the process of photosynthesis are: water, sunlight and carbon dioxide.

The by-products are: oxygen and sugars.

Photosynthesis can be summarized in the following equation:

6 CO2 + 12H2O+ Light energy

C6H12O6 + 6 O2 + 6H2O

(glucose)

Who or what photosynthesizes?Photoautotrophs can photosynthesize.Includes: green plants, algae, cyanobacteria and green

protists

The importance of photosynthesisTo provide nutrients and oxygen for heterotrophs.Heterotrophs are dependent on autotrophs, because

they cannot produce their own food.Auto means self: troph means feedingThus plants are self-feeding organisms meaning that

they make their own food.

RAW MATERIALS OF PHOTOSYNTHESIS

• The raw materials of photosynthesis are:

water, carbon dioxide and sunlight.

Where in the plants does photosynthesis occur? Photosynthesis occurs in the chloroplasts of

plant cells. The chloroplasts are mainly concentrated in the

mesophyll cells of leaves. Chloroplast contain chlorophyll – green pigment

that absorbs sunlight. Chlorophyll fill the space in the thylakoid

membrane.

Chloroplast structure

HOW RAW MATERIALS REACH THE CHLOROPLASTS Water is absorbed through the root hair into the

xylem of the roots, into the xylem of the stem, through the xylem of the leaves into the mesophyll cells and finally into the chloroplasts.

Carbon dioxide diffuses from the atmosphere through the stomata, into the intercellular airspaces in the leaves, and finally into the chloroplasts of the mesophyll cells.

The chlorophyll and other pigments in the thylakoid membrane absorb the solar energy to drive photosynthesis

The function of the stomata in photosynthesis

A stomata is a pore that is found on the leave.

It plays a vital role in the gaseous exchange;

Carbon dioxide diffuses from the atmosphere

through the stomata into the leave.

Oxygen diffuses from the leaves through the

stomata into the atmosphere.

Factors that that causes a change in the rate of photosynthesis

Light, concentration of carbon dioxide and temperature.

With light: less sun= less photosynthesis,

More sun= more photosynthesis. This is because there is a 'light

dependant reaction' as part of photosynthesis, and therefore

photosynthesis can only happen when there is enough sunlight. The

more the carbon dioxide, the faster the rate of photosynthesis.

Increasing the temperature increases the rate of photosynthesis. This is because there are enzymes in the process of photosynthesis.

Enzymes activity increases with an increase in rate of the temperature (up to a point, when it is too hot for the enzymes to work).

The importance of photosynthesis A review o Photosynthesis produce oxygen into the

atmosphere .o Plants store excess sugar as starch in

roots, tubers, seeds, and fruits.o Plants produce food by through the

process of photosynthesis.

References Williamson, J. (2011). Unit 6: Photosynthesis (Process of food

production by plants) PowerPoint Slides. Johannesburg:University of Johannesburg.

http://wiki.answers.com/Q/What_is_the_function_of_stomata_in_the_leaf ( Accessed on 15 October 2012)