IGCSE Cells, Molecules and Digestion Notes

Notes on Cells, Molecules and Digestion for students taking IGCSE Biology with Edexcel

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Cells, Molecules and Digestion
Cells
A simple plant cell has...
- Cell Wall for structure and support around the
cell.
- Cell Membrane controls what goes in and out
of the cell (on the inside of the cell wall)
- Nucleus controls the cell (in the cytoplasm)
- Cytoplasm does the respiration (in the centre
of the cell)
- Chloroplast contains chlorophyll which does
photosynthesis
- Vacuole holds water (in the centre of the cell.
A simple animal cell has...
- Cell Membrane controls what goes in and out of the cell (on the
inside of the cell wall)
- Nucleus controls the cell (in the cytoplasm)
- Cytoplasm does the respiration (in the centre of the cell)
The sequence shows the complexity within an organism
Organelle ­ Cells ­ Tissues ­ Organs ­ Systems ­ Organisms
Food Types
Name what it does ­ where it is found
Fats Energy source/insulation vegetable oils/milk/butter
Protein Growth/repair of tissues meat/fish/nuts
Carbohydrates Energy source sugary and starchy foods
Fibre (cellulose) Improves peristalsis ­ nuts/vegetables
Calcium ­ Hardens bones and teeth milk
Iron ­ Haemoglobin production ­ red meet
Vit A ­ Improves sight ­ fish oils/carrots
Vit C ­ Makes tissues ­ citrus fruits
Vit D ­ Absorbs calcium ­ fish oils/milk
Water ­ Allows cell reactions to take place ­ any drink
Food Tests
Glucose = add benedict's solution = (positive) Brick red
Starch = add iodine solution = (positive) Blue/black
How to modify and improve an experiment
a) To improve accuracy do the experiment at more times/ temperatures
b) To improve reliability repeat experiment and take an average
c) To improve precision use more sensitive equipment
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Enzymes
They are chemicals made by cells
All chemical reactions in the body are controlled by enzymes
Enzymes are catalysts which speed up processes and reactions
They are very specific and can only affect one reaction
Enzymes work quicker when they are warm
They work best at the correct pH
They are not changed or worn out by the reactions they control.
- Carbohydrase/Amylase is made in the pancreas, salivary glands and small intestine.…read more

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The oesophagus contracts behind the food, which pushes it down. This is peristalsis.
It enters the stomach.
3) The stomach adds acid to kill bacteria. The stomach muscles also work to increase
the surface area. Slowly, it is let into the small intestine.
4) In the small intestine, maltase is added, which digests the maltose into glucose.
5) The glucose is now small enough to go through the villi on the small intestine wall. It is
then absorbed into the bloodstream.…read more

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