Biology B3 GCSE Revision Notes OCR (higher)

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1 Biology B3 GCSE Revision Notes OCR (higher) CELLS AND DNA Cell Membrane - controls movement in and out of cell. Cytoplasm - where chemical reactions take place Mitochondria - respiration happens here Ribosomes - Where proteins are made (proteinsynthesis), attatched to membrane Membrane - attatched to the nucleus Nucleus - controls the cell. Contains Genetic info Gene - Small peice of DNA Protein - Amino acids joined together in the Ribosomes Amino Acids - 3 base pairs (or 6 bases) Allele - Different form of the same gene (eg. Blue/brown/green eyed gene) (b)(b) Chromosones - consist of lots of genes. Base Pairs - (A-T) (G-C) We have 46 chromosones, and an egg cell has 23. DNA Replication

2 Step 1) The Double Helix unzips Step 2) New bases pair up with the exposed bases. Step 3) Enzymes bond the bases together to form COMPLEMENTOR STRANDS. Step 4) Two Identical peices of DNA are formes Proteins Essential amino acids - the ones we get from are diet Transamination - Changing the structure of amino acids (in liver) Triple of base pairs # amino acids # proteins DNA FINGER PRINTING Inks Wrinkles/lines Criminals BLOOD TESTS 1) Isolation 2) Fragmentation 3) Seperation 4) Comparison Isolation - DNA is extracted (blood/semen/hair follicles. Fragmentation - DNA is cut into sections using restriction enzymes

3 Seperation - DNA is seperated using electrolysis Comparison - DNA "fingerprint" is analysed and compared with reference sample. eg. Blood from crime scene. MITOSIS CELL DIVISION (1) Parental Cell begins in Diploid state.(2) Each Indivisual chromosome replicates itself. (3, 4, 5) The Replica seperates from original and goes to opposite poles. Cell division now occurs (6) 2 'Daughter Cells' are made. Genetically identical.

4 MEIOSIS Cells end in Happloid state. Cells are in a Diploid state when in pairs. Cells are in a Happloid state when they are unpaired. When the sperm meets the egg, the chromosome bursts the acromosome (at tip) bursts to break down the eggs cell membrane, by releasing enzymes. Sperm contains lots of mitochondira for respiration, to produce energy. Then the nucleus goes inside the egg. Heart - Pumps blood around the body THE CIRCILATORY SYSTEM

5 Arteries - transports blood away from heart Veins - transports blood to the heart Capillaries - involved in exchanging materials with tissues Human Circulatory = double ciculatory system It has: THE BLOOD transports oxygen and food to cells removes waste product from cells forms part of body's defense mechanism Platelets Plasma White blood cells Red blood cells

6 Red blood Cells contain Haemoglobin Haemoglobin + Oxygen # Oxyhaemoglobin DIFFUSION - Particles move from high to low concetration (net movement) Speading up diffusion -Decrease distance the particles have to travel -Increase the concentration gradient -Increase Surface Area Plants respond to -light -water -gravity PLANT GROWTH A tropism is a growth movement in response to a stimulus A growth movement TOWARDS a stimulus is called a POSITIVE TROPISM A growth movement AWAY FROM a stimulus is called a NEGATIVE TROPISM. Response to sunlight -Towards the sun - Positive Phototropism -Away from sun - Negative Phototropism Response to Gravity -Towards gravity - Positive Geotropism -Away from gravity - Negative Geotropism Response to Water -Towards water - Postive Hydrotropism -Away from water - Negative Hydrotropism Hormones in plants The hormone that controls growth in plants is called AUXIN. Auxin moves away from the sun Cells where the Auxin is present (cells on the side of the plant furthest from the sun) will elongate, causing the plant to bend towards the sun, as the side furthest from the sun'll get longer. ENZYME An enzyme is a chemical that speeds up a reaction. It's a Biological Catalyst.

7 A specific enzyme collides with a substrate in a "lock and key" method: It breaks down the substrate quicker, and the substrate turns into a product. HUMAN GROWTH Stem Cell - an undifferenciated cell -It can become any cell, not yet specialised. -They become tissue cells. For Example, the nerve, blood or skin cells. 5 Main Stages in human life Infancy Childhood Adolescent Adulthood Elder Gestation Periodthe time from fertilisation till birth

8 Growth Problems At birth, weight and head cirfumference is measured -Poor weight gain - could be digestive problems -larger than normal head size - indicates the skull bones have not fused together properly DIABETES Genetic Engineering -transfer of genese from one organism to another leading to having new, wanted characteristics. There are Ethical Issues such as "designer babies" Insulin Production Glucose + Insulin # Glycogen Glycogen + Insulin # Glucose The insulin making gene is cut out of the chromosome using a restriction enymes The individual gene can then be cut out A ring of bacterial DNA (plasmid) is cut open with a different restriction enzyme The human insulin-making gene is then inserted into the bacterial DNA The plasmid is put back into the bacteria, which is allowed to replicate; providing lots of insulin The insuling is then extracted, so it can be injected into humans