CCEA GCSE BIOLOGY unit 1 notes
BIOLOGY NOTES.
UNIT 1: Photosynthesis
Photosynthesis Word Equation:
Light
Carbon Dioxide + Water Oxygen + Glucose Chlorophyll
How to test a leaf for starch:
1. Dip leaf boiling water for about 1 minute to soften it, stop further chemical changes and make the cell more permeable.
2. Turn off Bunsen burner.
Put the leaf into the half a test-tube of ethanol.
Stand the test-tube in the hot water for a few minutes.
(Takes green chlorophyll out of leaf)
3. Dip the leaf into water. (Softens the leaf)
4. Spread the leaf out on a white tile and cover it with iodine solution.
Leaf at start of experiment:
Green stripes (contain chlorophyll)
White stripes (contains no chlorophyll)
Leaf after iodine added:
Blue/Black (starch contained)
Yellow/Brown (doesn’t contain starch)
Factors affecting the rate of photosynthesis:
There are three main factors affecting the rate of photosynthesis.
Light Intensity
Carbon Dioxide Concentration
Temperature
However as soon as one or more of these factors falls in supplies then the rate of photosynthesis will drop.
The factor which is in shortest supply will be the one which actually limiting the rate of photosynthesis
E.g. If there is a high light intensity and a good supply of food supply of carbon dioxide but the temperature is low, then the rate of photosynthesis is limited by the low temperature.
Carbon Dioxide levels:
Decreased Increased
Purple INDICATOR Yellow Carbon Dioxide Carbon Dioxide
At normal atmospheric levels of carbon dioxide the indicator is orange-red
Indicator = Hydrogen carbonate
To remove carbon dioxide = sodium hydroxide
Maximising the rate of
UNIT 1: Photosynthesis
Photosynthesis Word Equation:
Light
Carbon Dioxide + Water Oxygen + Glucose Chlorophyll
How to test a leaf for starch:
1. Dip leaf boiling water for about 1 minute to soften it, stop further chemical changes and make the cell more permeable.
2. Turn off Bunsen burner.
Put the leaf into the half a test-tube of ethanol.
Stand the test-tube in the hot water for a few minutes.
(Takes green chlorophyll out of leaf)
3. Dip the leaf into water. (Softens the leaf)
4. Spread the leaf out on a white tile and cover it with iodine solution.
Leaf at start of experiment:
Green stripes (contain chlorophyll)
White stripes (contains no chlorophyll)
Leaf after iodine added:
Blue/Black (starch contained)
Yellow/Brown (doesn’t contain starch)
Factors affecting the rate of photosynthesis:
There are three main factors affecting the rate of photosynthesis.
Light Intensity
Carbon Dioxide Concentration
Temperature
However as soon as one or more of these factors falls in supplies then the rate of photosynthesis will drop.
The factor which is in shortest supply will be the one which actually limiting the rate of photosynthesis
E.g. If there is a high light intensity and a good supply of food supply of carbon dioxide but the temperature is low, then the rate of photosynthesis is limited by the low temperature.
Carbon Dioxide levels:
Decreased Increased
Purple INDICATOR Yellow Carbon Dioxide Carbon Dioxide
At normal atmospheric levels of carbon dioxide the indicator is orange-red
Indicator = Hydrogen carbonate
To remove carbon dioxide = sodium hydroxide
Maximising the rate of