Photosynthesis

LEARNING OUTCOMES Explain the roles and importance of photosynthesis Describe the process of photosynthesis Question the factors influencing the rate of photosynthesis

Exercise In your group discuss what is required for photosynthesis to take place

Photosynthesis – in outline Photosynthesis = light makes nutrition Photosynthesis takes place in cells containing chloroplasts chloroplasts trap the sun’s energy in chlorophyll This energy is then converted into food for the plant: principally sugars and starch Sunlight Carbon dioxide Water Oxygen Glucose is produced to nourish the plant

The photosynthesis equation The photosynthesis equation is as follows: carbon dioxide + water + energy glucose + oxygen 6CO2 +6H2O + energy C6H12O6 + 6O2

Exercise In your group discuss why you think photosynthesis is important in plant life,

Why photosynthesis is important It provides food for plants for growth and repair Plants in turn provide food for the rest of the food chain Photosynthesis is the only natural process which: uses carbon dioxide and releases oxygen back into the atmosphere

Exercise In your group list what the main ingredients are in the process of photosnthesis

The ingredients of photosynthesis Water. The plant absorbs water from the soil through root hairs – by osmosis Carbon dioxide. The leaf obtains carbon dioxide from the air through pores in the epidermis (the ‘skin’ of the leaf) called stomata – by diffusion Light energy. The cells of the epidermis are transparent to allow sunlight to pass through to the mesophyll cells which contain the chloroplasts.

Ingredients for photosynthesis Sunlight passes through the epidermis to reach the mesophyll cells Water passes from the roots by osmosis Carbon dioxide enters through the stomata by diffusion

The products of photosynthesis The glucose produced by photosynthesis is used in different ways: It may be used by respiration to create energy. It may be converted into starch and stored within the leaf, inside the chloroplasts. It may be converted into sucrose and transported to other parts of the plant. It can then be converted back into glucose, for energy, or starch, for growth or storage. It may be converted into other organic substances such as cellulose (a carbohydrate) or amino acids (proteins).

The rate of photosynthesis Sunlight. As light increases, so does the rate of photosynthesis up to a maximum. A plant cannot photosynthesise in the dark. Temperature. The second stage of photosynthesis is sensitive to temperature: the optimum temperature is 20-30 degrees Celcius. Carbon dioxide. In very warm weather the stomata may close to reduce water loss. When this happens, carbon dioxide cannot enter the leaf and photosynthesis may stop.

Conclusion From todays lesson what are your views in relation to photosynthesis? Will you now look at plants in a different way. Will it help you now identify when a plant is not healthy.

Homework Research the following: Chlorosis Necrosis