CCEA GCSE BIOLOGY unit 1 notes Essay

4997 Words Feb 14th, 2014 20 Pages

UNIT 1: Photosynthesis

Photosynthesis Word Equation:

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
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Test for Sugar:
Add Benedict’s reagent (10 drops) (blue in colour)
Bring to boil
If sugars are present then colour change occurs
Blue -> green -> yellow -> orange -> brown -> brick red
Test for Protein
Testing for protein : The Biuret Test
Add an equal amount of sodium hydroxide
Add 10 drops of dilute copper sulphate solution
If protein is present:- colour change from blue to violet
If protein is not present:- it remains blue

Test for ascorbic acid (Vitamin C)
Place exactly 1cm of DCPIP solution in a test-tube using a syringe.
Fill a 1cm3 syringe with 0.01% solution of ascorbic acid
Add the ascorbic acid solution to the DCPIP drop by drop until the colour has been removed from the DCPIP

Percentage of Volume of standard ascorbic acid
Ascorbic Acid= solution added in 3 x 0.1 Volume of juice added

The greater the amount of vitamin C there is in the juice, the less juice it will take to decolourise it

The link between health and diet
We should try and have a balanced diet
(being very overweight)
Caused by having a higher energy intake (sugar, starch or fat) than the energy used in exercise.
Heart disease:-
Caused by cholesterol and other fatty substances present in such high levels that they can build up in the walls of arteries.
Over time this leads to a narrowing of the arteries,

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