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S3 Biology
Unit 1: Cell Biology
Pupil Summary Notes
1. The cell is the basic unit of all living things.
2. Cells have certain structures in common: a membrane, a nucleus, cytoplasm and
mitochondria.
3. In addition plant cells have a cell wall, a central vacuole and chloroplasts.
4. Microscopes are used to see tiny objects like cells more clearly.
5. A light microscope can magnify an object by several 100 times.
6. An electron microscope can magnify an object by several 1000 times.
7. MRS GREN stands for the 7 life processes.
8. Respiration is an energy releasing process.
9. It takes place in all cells (in the mitochondria).
10 The word equation for respiration is:
Glucose + oxygen - energy + water + carbon dioxide.
11.There are 2 chemical tests for carbon dioxide: limewater: turns from clear to
cloudy and bicarbonate indicator turns from red to yellow.
12. Carbohydrates are the main energy providing food group; Proteins are mainly used
for growth and repair; fats can provide a lot of energy or can be stored and used to
insulate the body.
13. Enzymes are biological catalysts, they change the speed of chemical reactions.
14. Enzymes are made from proteins.
15. Some enzymes eg. Amylase and Catalase break down complex chemicals into smaller
ones.
16. Some enzymes eg. Phosphorylase build up large molecules like starch from simpler
ones.
17. Enzymes are sensitive to temperature; high temperatures denature the enzyme
(which means it will no longer work).
18. Enzymes are sensitive to pH. Pepsin prefers a low ph of 2.8; Catalase prefers a
higher ph of 7.
19. Photosynthesis is how plants make food.
20. The word equation for photosynthesis is:
sunlight
Carbon dioxide + water ____________>> glucose + Oxygen
chlorophyll
21. Chlorphyll is essential for photosynthesis because it traps the light energy needed to
start the reaction.
22. Some of the glucose made during photosynthesis is converted to starch and stored by
the plant.
23. Chromosomes and their genes are made from a molecule called DNA.
24. DNA molecules carry the genetic code: a set of instructions that controls
what cells do.
25. DNA is made up of a sugar, a phosphate and a base.
26. There are 4 types of bases: Adenine, Cytosine, Guanine and Thymine.
27. Chromosomes are thread like structures found in the nucleus of cells.
28. Chromosomes contain a string of genes; a gene is a unit of inheritance.
29. Each species has its own unique chromosome number and chromosome
complement.
30. Humans have a chromosome number of 46.
31. Within each species variation exists; this is because each individual has
its own genetic code.
32. Cell division is how an organism makes new cells for growth, development
and repair.
33. Cell division is also known as Mitosis.
34. Cell division begins with each chromosome making an exact copy of it’s
self.
35. After a series of stages in which the chromatids line up and separate, 2
new daughter cells are formed.
36. The new cells are identical to the original cell because they have the
same chromosome complement.
37. Stem cells are basic cells with very special properties.
38. Stem cells are special because they have the potential to turn into any
type of cell.
39. Stem cells can come from an embryo or from the bone marrow of an
adult.
40. Stem cells can be used to treat a number of diseases and medical
conditions e.g. some types of cancer (brain, ovarian, skin, testicular); or
conditions like: Multiple sclerosis, Crohn’s disease, Parkinson’s disease, Heart
damage, Stroke damage.