1.2 In mitosis a cell splits to create two
identical copies of the original cell.
1.3 In meiosis cells split to form new cells
with half the usual number of
chromosomes, to produce gametes for
1.3.1 Gametes are sex cells. The male gametes are the sperm, and
the female gametes are the eggs. Gametes contain one set of
genetic information, while body cells contain two sets of
188.8.131.52 Fertilisation is when the male gamete (sperm) and the
female gamate (egg) join
2 Anearobic & Arobic Respiration
2.1 Aerobic respiration is used to help
mammals maintain a constant body
temperature, they do this through the use
of Aerobic Respiration
2.1.1 Aerobic respiration needs oxygen. It is the release of a relatively
large amount of energy in cells by the breakdown of food
substances in the presence of oxygen:
184.108.40.206 word equation: glucose + oxygen → carbon dioxide + water
chemical equation: C6H12O6 + 6O2 → 6CO2 + 6H2O
220.127.116.11.1 Aerobic respiration happens all the time in animals and plants. Note that
respiration is different to breathing (ventilation). Most of the reactions in aerobic
respiration happen inside mitochondria in cells (cells which provide energy)
2.2 Unlike aerobic respiration, Anaerobic
respiration does not need oxygen.. It is
the release of a relatively small
amount of energy in cells by the
breakdown of food substances in the
absence of oxygen.
2.2.1 Anaerobic respiration occurs during hard excersize
18.104.22.168 word equation: glucose-->lactic acid
chemical equation: 6H12O6 → 2C3H6O3
22.214.171.124.1 Glucose is not completely broken down, so much less energy is released than
during aerobic respiration. There is a build-up of lactic acid in the muscles during
vigorous exercise. The lactic acid needs to be oxidised to carbon dioxide and water
126.96.36.199.1.1 This created an oxygen debt, and just like money, debt must be repaid. (This is
why we breathe deeply after exercise)
2.2.2 Anaerobic Respiration also takes place in plants and yeast
188.8.131.52 Anaerobic respiration also happens in plant cells and some microorganisms.
Anaerobic respiration in yeast is used during brewing and bread-making: glucose
→ ethanol + carbon dioxide C6H12O6 → 2C2H5OH + 2C02 Ethanol is the alcohol
found in alcoholic drinks like beer and wine. In bread-making, bubbles of carbon
dioxide gas expand the dough and help the bread rise.
3 The circulatory system
3.1 Also known as the cardiovascular system, your heart, blood
vessels and blood itself are three essential components the
body needs to survive. The circulatory system consists of two
circuits that blood travels through; pulmonary and systemic.
Exercise affects these systems, causing the heart to pump
blood faster around the body, which in turn allows you to
exercise for longer!
3.1.1 The pulmonary circuit carries blood to the lungs to be oxygenated and then
back to the heart. In the lungs, carbon dioxide is removed from the blood, and
oxygen taken up by the haemoglobin in the red blood cells.
3.1.2 The systemic circuit carries blood around the body to deliver the oxygen and
returns de-oxygenated blood to the heart. Blood also carries nutrients and
4 Enzymes, Amino Acids & Proteins
4.1 Proteins are made from long chains of smaller molecules called amino
acids. These long chains are folded into particular shapes. This is
important in relation to how antibodies and enzymes work.
4.1.1 Different proteins The long chains of amino acids fold to give each type of
protein molecule a specific shape. Proteins act as: Structural components
of tissues (such as muscles) Hormones (such as insulin) Antibodies (part
of the body's immune system) Biological catalysts (enzymes)
184.108.40.206 They are shape specific
4.2 Enzymes are biological catalysts. There are optimum
temperatures and pH values at which their activity is
greatest. Enzymes are also proteins. If the shape of an
enzyme changes, it may no longer work (it is said to
have been 'denatured').
4.2.1 There are only about 20 different naturally occurring amino acids. However,
each protein molecule has hundreds, or even thousands, of them joined
together in a unique sequence. This gives each protein its own individual
5.1 A double helix has 4
5.1.1 A goes to T
220.127.116.11 C goes to G
5.2 deoxyribose nucleic acid
5.2.1 Chromosones are made from DNA
18.104.22.168 Genes are short sections of DNA
5.3 Your DNA is the code that
makes you, you!
6.1 The word mutation means a change in the genetic composition of a cell.
Mutations can be divided into two main groups. The first group is gene
mutations. These are chemical changes in the DNA of the cell.
6.1.1 A gene mutation is a change in the order
of bases on a strand of DNA.
6.1.2 Chromosome mutations are due to
change in either the chromosome
structure or the chromosome number of a
7.1 Plants can make identical copies of themselves by asexual
reproduction, for example by tubers and runners. Humans have
been cloning plants for years and have recently started to
develop techniques to clone animals.
7.1.1 Asexual Reproduction involves only one parent
7.1.2 Advantages: Can produce lots of the same
plant, even if the seed is rare
22.214.171.124 Disadvantages: If a disease knocks out one plant, it
will knock all of them out because they are
7.2 However, animal cloning raises ethical
issues about how far humans should
interfere in the production of new life.
8 Stem Cell Research
8.1 Stem Cells can be used to grow any part of a human body
8.2 There are two types of stem cell: Emboyonic and Bone Marrow
8.2.1 Many people disagree with Emboyonic stem research as an embroyo is a living thing
8.3 Can be used to cure Parkinsons, rebuild bones
and body parts, repairing damages immune