1. B3 Science Revision Liver and muscle cells have large numbers of mitochondria Ribosomes are in the cytoplasm and where protein synthesis happen. Four different bases, A,T,G,C. Proteins are made from lots of amino acids joined together. Each amino acid is coded by the sequence (order) of three bases. For example, GGT. The genetic code needed to make a particular protein is carried from the DNA to the ribosomes by a molecule called mRNA. mRNA from DNA is called transcription Proteins from mRNA is called translation

2. Enzymes Proteins and made from long chains of amino acids Functions include structural (collagen), hormones (insulin), carrier molecules (haemaglobin) & enzymes. Enzymes are biological catalysts which catalyse chemical reactions Enzymes use a lock and key mechanism and will denature which change the the shape of the active site at high PH and high temperatures Gene mutations may lead to the production of different proteins, these mutations can happens spotaneously, by radiation or chemicals

3. Respiration Energy is needed for : Protein synthesis Muscle contraction Control of body temperature in mammals Respiratory quotient (RQ) RQ = carbon dioxide produced ÷ oxygen used Usually RQ = 1. During exercise, the muscle cells respire more than they do at rest. This means: Oxygen and glucose must be delivered to them more quickly Waste carbon dioxide must be removed more quickly Achieved by increasing the breathing rate and heart rate. Aerobic Respiration Glucose + oxygen → carbon dioxide + water C6H12O6 + 6O2→ 6CO2 + 6H2O Anearobic respiration Glucose → lactic acid Metabolic rate Themetabolic rate is the rate at which energy is used by the body. Since aerobic respiration needs oxygen, the rate of oxygen consumption can be used as an estimate of metabolic rate. The rate of respiration is influenced by changes in temperature and pH. This is because enzymes are involved in respiration, and their activity varies with temperature and pH. ATP ATP is a substance that is used as the energy source for many processes in cells. ATP is produced as a result of respiration. For example, one glucose molecule can release enough energy during respiration for the production of: 38 ATP molecules by aerobic respiration 2 ATP molecules by anaerobic respiration

4. Watson and crick best known for discovering DNA however: Rosalind franklin and maurice wilkins used xray crystallograhy to take pictures of the DNA. The pictures showed DNA as two chains wound in a double helix Erwin chargaff discovered there are equal numbers of A and T bases and of G and C bases in DNA

5. Questions What is a section of chromosome called? Explain why muscle cells have lots of mitochondria? Finish the sentence the order of bases in DNA is called the base …….. Why is collagen needed in the artery walls? What other name is used to describe enzymes? Pepsin is an enzyme found in the stomach. It breaks down proteins into amino acids. Draw a diagram to explain why pepsin cannot break down starch. Higher tier need page 13 in the text book

6. Chromosomes in nucleus are copied Chromatids pulled apart Cromosoomes separate Cell divides Mitosis ‘unzipping’ to form single strands New double strands forming by complementary base pairing Unicellular vs multicellular An ameoba, a simple unicellular organism Organisms can consist of one cell to many cells: Simple organisms may be unicellular(consist of one cell) Complex organisms aremulticellular(consist of many cells) There are advantages to being multicellular rather than unicellular. These include allowing: The organism to be larger Cell differentiation (having different types of cells with different functions) The organisms to be more complex

7. B3 Science Revision Produces gametes which are haploid (contain one chromosomes from each pair). Gametes combine to form a diploid zygote Genes on the chromosomes combine to control the characteristics of the zygote. Meiosis ‘unzipping’ to form single strands New double strands forming by complementary base pairing Structure of the sperm Acrosome Nucleus Mitochondria Tail

8. B3 Science Revision Red blood cells have a large surface area to volume ratio, lack a nucleus and contain haemoglobin. Haemoglobin + oxygen oxyhaemoglobin Arteries transport blood away from the heart, they have thick muscular and elastic walls Veins transport blood to the heart, they have a large lumen and contain valves Capillaries exchanging materials with tissues and are therefore permeable Left atrium Left ventricle Right ventricle Vena Cava Valve Right atrium Valve Pulmonary vein Pulmonary artery Aorta Red blood cells: carry oxygen White blood cells: fight disease Platelets: clot the blood Plasma: the liquid that everything travels in the blood

9. 1.what are the three reasons why the body needs to make new cells? 2.Give an advantage of being multicellular 3.Explain how the sperm is adapted for its job 4.Name the 3 parts of the blood and the job that it does 5.Why is plasma a liquid? 6.What is one way a red blood cell is adapted to its job? 7.Explain why the left ventricle has a thicker muscle wall than the right ventricle?

10. Bacteria cell lack a true nucleus, mitochondria and chloroplasts instead they contain a single circular strand of chromosome Stem cells Undifferrentiate dcells that can develop into different cells. Two types: embyonic (obtained from embryos) and Adult (obtained from a human) Plant growthAnimal growth Grows continuously Finite size Restricted to meristems Everywhere Gain height by cell enlargement Gain height by Cell division Cells can differentiate Lose ability to differentiate

11. Genetic engineering Selection of desired characteristics Isolation of genes resposible Insertion of other genes into other programmes Replication of organismas Selective breeding These are the steps in selective breeding: Decide which characteristics are important Choose parents that show these characteristics Select the best offspring from parents to breed the next generation Repeat the process continuously http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/living_growing/new genesrev4.shtml

12. B3 Science Revision Gene therapy: changing a persons genes in an attempt to cure disorders Tissue culture Examples: Genes from carrots and putting them into rice, producing insulin and becoming resistant to herbicides, frost damage or disease to crops. Selective breeding may lead to inbreeding due to a reduction in the gene pool Cloning technique used to produce dolly: Nucleus removed from an egg cell Egg cell nucleus replaced with the nucleus from the udder cell. Egg cell given an electric shock to make it divide Embryo grows into a clone of the sheep from which the udder cell came

14. plants grown from cuttings or tissue culture are clones. advantage - can be sure of the characteristics of the plant since all plants will be genetically identical advantage - it is possible to mass produce plants that may be difficult to grow from seed disadvantage - if plants become susceptible to disease or to change in environmental conditions then all plants will be affected disadvantage - lack of genetic variation.

15. Which part of the cell contains cellulose? Name three structures found in an animal cell and not in a plant cell? Name one characteristic of strawberry plants that is useful to gardeners? Complete the sentence: when a scientist takes ______ from one organism and puts them into another it is called _______ _______ Which organisms are used to make insulin? Why would cloning pigs be useful? how do many plants reproduce? Describe an advantage and a disadvantage of cloning plants?