B2 TOPIC 1 Genes and Enzymes

1. B2 TOPIC 1 Genes and Enzymes

2. Animal Cell Plant Cell Cell membrane –It controls the movement of substances such as oxygen, glucose and carbon dioxide in and out of the cell. Cytoplasm- Contains organelle (tiny structures that do specific jobs) , chemical reactions occur which carry out life processes. Nucleus – contains genetic material DNA and controls activity. Mitochondria – organelles where respiration occurs and where energy is made. Cell wall – contains cellulose to maintain its structure. Large vacuole – a space in the cytoplasm that is filled with cell zap which helps to support the plant by keeping cells rigid. Chloroplast – organelles that contain chlorophyll, a green substance that absorbs sunlight used in photosynthesis. Everything in animal cell is also included in plant cells.

3. Bacteria Chromosomal DNA – controls cell activities and replication. It carries most of genetic information. Plasmids - forms small loops and carries extra information. It contains genes e.g. drug resistance. Flagellum – it’s a long, hair like structure that rotates to allow the bacterium to move.

4. Microscope Total mag = mag of eyepiece X mag of objective lens Low magnification means its a general shape of cell. Magnification = length of image length of specimen

5. DNA – Deoxyribonucleic acid • Breakdown of DNA • Nucleus – contains chromosomes • Chromosome – consist of a string of genes • Genes – carries on instructions • DNA sequence • Base pairs Genes are the actual cods for a protein. Proteins code for all of our characteristic features. Adenine & Thymine Cytosine & Guanine

6. Protein Synthesis • Transcription • DNA in a gene unzips. • One strand of the gene is used as a template. • A complimentary molecule mRNA forms. • mRNA has a base pair called URACIL instead of Thymine. • mRNA then enters the cell into the cytoplasm. • Translation • mRNA attaches/ binds to ribosomes. • The ribosomes reads along the mRNA which decodes the bases in groups of three, known as base triplets or codons. • Each amino acid is attached to tRNA. Each tRNA has a triplet of bases. Proteins are made from amino acids. 20 different amino acids. Each amino acid is made from three bases called a triplet codes or codon. Proteins can be made by joining the amino acids in different ways. The sequence of amino acid is a polypeptide chain, this fold/ forms the proteins.

7. Enzymes Enzymes are catalysts that is found/produced by living things. And they are special proteins that speed up reactions. Catalysts is a substance which INCREASES the speed of a reaction without being CHANGED or USED UP in the reactions. Two types of Enzymes: Builder Enzymes – join small molecules together forming a bigger molecule (substrate) . Breaker Enzymes – break big molecules (substrates) into smaller molecules. Every enzyme has an active site and tis is where the reaction takes place, so it has to be in the same shape for the substrate (molecule) to fit in.

8. Enzyme substrate complex This is when the substrate is locked into the enzyme so it can be catalysed. This is called the “lock and key” mechanism.

9. Enzyme Inhibitors Inhibitors are molecules that decrease the rate of enzyme catalysed reactions. Competitive inhibitors are a similar shape in the enzymes blocking the substrate (molecule), stopping enzymes carrying out its reaction. Non-competitive inhibitors are a different shape to the reactant. It binds to another point on the enzyme, which distorts and changes the shape of the active site and when the actual substrate comes along, it doesn’t fit.

10. Factors that affect enzymes Temperature some temperatures the rate of reaction is faster but when it reaches its optimum (best) the enzyme becomes denatured (substrate no longer fits in active site) because the active site has changed. pH An enzyme is affected by how much acid or alkali is present. If the pH is too high or low the enzyme also because denatured. Substrate concentration The higher the substrate concentration, the faster the reaction will occur. This can only occur at a point and after that the active site becomes full.

11. Human Genome Project Benefits • Predict and Prevent diseases • Develop new and better medicines and treatment • Accurate Diagnosis • Improve Forensic Science The Human Genome Project was a project to identify the 20,000- 25,000 genes in the human body and began in 1990 and took 13 years to complete. Their aims were to find out and know the sequences of 3 billion chemical pairs in the DNA and to store this information in a database. Problems • Increased stress/panic • Discrimination

12. Genetic Engineering Benefits • Take a Human chromosome and take out a useful gene using enzymes. • Take the plasmid out of a bacterium using enzymes • Then you put the useful gene into the plasmid using enzymes • Production of human insulin • Producing more Vitamin A which will reduce VA deficiency (Beta-Carotene is put into normal plants e.g rice) • Increasing crop yield (herbicide) • Produce organisms with desired features quickly • Increase genetic diversity Ethnical Issues • Creation of new life forms and crossing species boundaries • Long-term effects on human health and the environment • Blending of nonhuman animal and human DNA • Unintended personal, social, and cultural consequences

13. Mitosis – is cell division that makes ordinary human body cells that is produced forgrowth and repair. Nuclei contains two copies of each chromosome. This makes them diploid cells. Human diploid contains 23 chromosomes. Body cells are diploid. Process The chromosomes make copies of themselves in a process called DNA replication. The copies of the chromosomes separate and the cell then divides. This produces two daughter cells, which are genetically identical to each other and to the parent cell. The process is done due to asexual reproduction.

14. Meiosis – is the production of sperm and egg cells (haploid gametes). NOT IDENTICAL Zygotes are diploid, they have two copies of each chromosome. Gametes have 23 chromosomes each and when the gametes combine during reproduction you get 46 chromosomes. Process DNA replication happens. Each chromosome is copied and makes identical copies of themselves. Corresponding chromosomes pair up and then each chromosome has become two chromatids. Second division takes place to separate the chromatids. This produces four haploid daughter cells which each contain only half of the original number of chromosomes. This process is called sexual reproduction.

15. Cloning Process Of Cloning • Take a cell from the adult animal to be cloned and remove the nucleus. • Take an egg cell from surrogate and remove the nucleus – forming an ENUCLEATED egg • Place the adult nucleus into the cell – this is diploid DNA • Give the egg a small electric shock to start mitosis • Implant the embryo into a surrogate mother • Offspring are born as normal but with the donor DNA.

16. Stem Cells They are unspecialised cells ( cells with no function .e.g. Embryo) that can divide to produce more stem cells or different kinds of specialised cells. • Benefits • Able to cure diseases • Able to create specialised cells • Potential to make cures • Issues • Potential to create human life

17. B2 TOPIC 2 Life Processes

18. Respiration – reactions that occur in all livings things in which glucose is broken down to release energy. • Aerobic Respiration – respiration that needs oxygen • Oxygen is used to release energy from molecules such as glucose. The glucose and oxygen are converted into carbon dioxide and water and energy us released for use in the cell, • GLUCOSE + OXYGEN  CARBON DIOXIDE + WATER • Anaerobic Respiration - respiration that doesn’t need oxygen • GLUCOSE  LACTIC ACID • This type of respiration releases less energy than aerobic respiration. Lactic acid is broken down using oxygen into carbon dioxide and water. After exercise the increase of oxygen is needed to break down lactic acid and to release energy for other processes in the cells.

19. Waste diffuse in and out of cells Glucose and oxygen is carried around the body and into the tissues by blood. The blood must carry waste, carbon dioxide away from respiring cells. All these substances move between respiring cells and capillaries by a process called diffusion. Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. The particles diffusion down a concentration gradient. In respiring cells, oxygen and glucose levels fall as they are used up in aerobic respiration so the concentration in the cells are low. The concentration of these substances are higher in the blood , so they diffuse from the capillaries into the cells. At the same time, carbon dioxide levels in the cells are high. This means carbon dioxide diffuses from the cells into the blood, where the concentration is lower. The bigger the difference in concentration, the faster the rate of diffusion.

20. Photosynthesis • Photosynthesis happens in the leaves of all green plants. It happens inside the chloroplast. They contain chlorophyll which absorbs energy in sunlight and uses it to convert carbon dioxide and water into glucose. Oxygen is produced also as a by-product. • CARBON DIOXIDE + WATER  GLUCOSE +OXYGEN • Limiting Factor –A condition in which reduces the amount of photosynthesis that can take place in a plant. • Light Intensity • Concentration of CO2 • Temperature

21. EPOC – Excess Post – exercise Oxygen Consumption Oxygen needed after exercise to break down lactic acid into carbon dioxide and water. LACTIC ACID +OXYGEN  CARBON DIOXIDE +WATER Cardiac output is the volume of blood the heart pumps in one minute – it increases as heart rate increases. CARDIACOUTPUT = HEART RATE X STROKE VOLUME ]

22. Leaves – adapted for efficient photosynthesis

23. Epidermis – Outer layer of tissues Cuticle – Waxy protective outer layer of epidermis that prevents water loss on leaves, green stems, and fruits.  The amount of cutin or wax increases with light intensity. Leaf hairs – part of the epidermis Palisade layer – A tightly packed layer of parenchyma tissues filled with chloroplasts for photosynthesis. Chloroplasts – Sub-cellular, photosynthetic structures in leaves and other green tissues.  Chloroplasts contain chlorophyll, a green plant pigment that captures the energy in light and begins the transformation of that energy into sugars. Vascular bundle – Xylem and phloem tissues, commonly known as leaf veins.Xylem transport water and dissolves minerals and Phloem transports sucrose. Spongy mesophyll – Layer of parenchyma tissues loosely arranged to facilitate movement of oxygen, carbon dioxide, and water vapor.  It also may contain some chloroplasts.  Stomata – Natural openings in leaves and herbaceous stems that allow for gas exchange (water vapor, carbon dioxide, and oxygen). Guard cells – Specialized kidney-shaped cells that open and close the stomata.

24. Osmosis- is the movement of water across a partially permeable membrane from a region of high concentration to a region of low concentration. A partially-permeable membrane is a membrane that allows small particles such as water molecules through it, but not larger particles such as sugar molecules and ions from salts. Water concentration A dilute solution has a high water concentration, while a concentrated solution has a low water concentration. For example, when salt is dissolved in water: A little dissolved salt produces a dilute solution with a high water concentration A lot of dissolved salt produces a concentrated solution with a low water concentration.

25. Osmosis in cells In plant cells Plant cells have a strong hard rigid cell wall on the outside of the cell membrane. This stops the cell bursting when it absorbs water by osmosis. As the pressure from the water increases inside the cell, it becomes more rigid. This is useful because plants do not have a skeleton. Instead the leaves and shoots can be supported by the turgor pressure, the pressure of water inside their cells. If plant cells lose too much water by osmosis, they become less rigid. Eventually the cell membrane shrinks away from the cell wall, causing the plant to wilt. In animal cells Osmosis explains how water moves in and out of animal cells through the cell membrane. If water continues to leave a cell it will shrink and become crinkly. If water continues to enter a cell it will eventually burst. These things happen because animal cells are not surrounded by an inelastic cell wall, unlike plant cells. Osmosis in cells In plant cells Plant cells have a strong hard rigid cell wall on the outside of the cell membrane. This stops the cell bursting when it absorbs water by osmosis. As the pressure from the water increases inside the cell, it becomes more rigid. This is useful because plants do not have a skeleton. Instead the leaves and shoots can be supported by the turgor pressure, the pressure of water inside their cells. Water entering the cell by osmosis inflates the cell and makes it rigid If plant cells lose too much water by osmosis, they become less rigid. Eventually the cell membrane shrinks away from the cell wall, causing the plant to wilt. Loss of water makes the cell limp and shrinks the cell membrane away from the cell wall. In animal cells Osmosis explains how water moves in and out of animal cells through the cell membrane. If water continues to leave a cell it will shrink and become crinkly. If water continues to enter a cell it will eventually burst. These things happen because animal cells are not surrounded by an inelastic cell wall, unlike plant cells. Osmosis in cells In plant cells Plant cells have a strong hard rigid cell wall on the outside of the cell membrane. This stops the cell bursting when it absorbs water by osmosis. As the pressure from the water increases inside the cell, it becomes more rigid. This is useful because plants do not have a skeleton. Instead the leaves and shoots can be supported by the turgor pressure, the pressure of water inside their cells. Water entering the cell by osmosis inflates the cell and makes it rigid If plant cells lose too much water by osmosis, they become less rigid. Eventually the cell membrane shrinks away from the cell wall, causing the plant to wilt. Loss of water makes the cell limp and shrinks the cell membrane away from the cell wall. In animal cells Osmosis explains how water moves in and out of animal cells through the cell membrane. If water continues to leave a cell it will shrink and become crinkly. If water continues to enter a cell it will eventually burst. These things happen because animal cells are not surrounded by an inelastic cell wall, unlike plant cells.

26. Root Hair Cell Transpiration The hairs on a root cell gives the plant a larger surface area for absorbing water from the soil. The high concentration from the soil enters the root hair cell by osmosis. Plants can only absorb soluble minerals (those that can dissolve in water). They absorb minerals dissolved in solution from the soil through their root hair cells. However, the concentration of minerals in the soil is very low. So they use the process ACTIVE TRANSPORT. Active Transport uses energy from the respiration to help the plant pull minerals into the root hair against the concentration gradient. Water on the surface of spongy and palisade cells (inside the leaf) evaporates and then diffuses out of the leaf. This is called transpiration. More water is drawn out of the xylem cells inside the leaf to replace what's lost. As the xylem cells make a continuous tube from the leaf, down the stem to the roots, this acts like a drinking straw, producing a flow of water and dissolved minerals from roots to leaves.

27. Distribution of Organisms- is where the organism is found. To study the distribution of an organism, you can measure how common an organism is in two sample areas and compare them. Sampling Animals Pooter- it is used to catch small invertebrates through an in let tube by sucking sharply on a second tube connected to the container. Pitfall trap – useful for trapping small animals such as spiders, Beatles and woodlice. Sweep net/ pond net – In areas with long grass sweep net can be used to catch some of the organisms present. A pond net can be used to sample aquatic habitats. Quadrat – they are square frames of known sizes which are placed in random places.

28. B2 TOPIC 3 Organ Systems

29. Evidence for Evolution • Fossils are any trace of plants or animals that lived long ago. • Fossils can be formed in three ways: • From Gradual Replacement by minerals – e.g teeth , shells and bones because they don’t decay quickly. They are replaced by minerals, forming rock like substances shaped like the original hard part. • From casts and impressions – when organisms are buried in soft material this forms a fossil. • From preservation in places where decay doesn’t happen – this is because the conditions aren’t suitable for microbes to work, e.g in glaciers (too cold) , in peat bogs (too acidic) and in amber (no oxygen or moisture) • Fossil record is incomplete and has many gaps because; • Some body parts, like soft tissue, decay away completely • There are some fossils yet to be discovered that might help complete the picture of evolution. • Very few dead plants or animals actually turn into fossils

30. Evidence for evolution • The Pentadactyl Limb • It’s a limb with five digits • You can see it in many species, e.g mammals, reptiles and amphibians • The similarity in bone structure provides evidence that species with a pentadactyl limb have all evolved from a common ancestor that once has the limb.

31. Growth and Development Growth means the increase in size or mass. Size – you can measure its height, width, length or circumference. Wet mass – The mass of an organism depends on how much water it has gained or lost (through drinking water or sweating). The wet mass of the organism is its mass including water in its body – it can vary from day to day. Dry mass – It is the mass of an organims with no water in its body. This doesn’t vary in the same way as wet mass, but you only measure it once the organisms dead. The dead organism is dried out by leaving it in a hot oven over night – then its weighed.

32. Plants and Animals grow and develop due to these processes : • Cell Differentatipm – the process by which a cell changes to become specialised for its job. • Cell division- by mitosis • Cell elongation – where a plant expand, making cells bigger and so making the plant grow. • Growth in Animals • It happens by cell division (mitosis) • When an animal is young, cells divide at a fast rate but when they are an adult most cell division is for repair – the cells divide to repair old or damaged cells. • This also means, in most animals, cell differentiation is lost at an early stage. • Growth in Plants • Plants grow continuously . So they continue to differentiate to develop new parts. • Growth in height is mainly due to cell elongation – cell division happens in the tips of the roots and shoots.

33. Blood • Plasma • Yellow Liquid which transports Red and White blood cells and platelets. • Nutrients such as; glucose and amino acids. They are absorbed from the gut and taken to body cells. • Carbon Dioxide – this is a waste product formed in every cell. It’s transported in the blood to the lungs , where its removed. • Urea- this is a waste product formed in the liver. The blood transports it to the kidneys, where it’s removed. • Hormones – transported from glands to target organs • Antibodies and Antitoxins produced by the white blood cells. • Red Blood Cells • Their job is to carry oxygen from the lungs to all the cells in the body. • They have a biconcave disc, this gives them a large surface area to volume ratio for oxygen to diffuse into and out of the cell. It has no nucleus and makes room for lots of haemoglobin. • Contain a substance called haemoglobin which contains a lot of iron. • In the lungs, haemoglobin combines with oxygen to become oxyhaemoglobin. • Oxyhaemoglobin is transported around the body to the tissues, where the oxygen is then released for aerobic respiration. • The lack of iron can lead to anemia.

34. White Blood Cells • Part of bodys defence against disease. • They can change to eat up unwelcome microogranisms. • They produce antibodies to fight microogransims. • They have a nuclues. • A low white blood cell count could increase the risk of infection where as a high count could mean you have an infection or even leukaemia (cancer of the blood). • Platelets • Ting fragments of cells with no nucleus. • They make clots if you cut or damage blood vessels. • Cloth dries out and forms a scab which stops pathogens getting into the body. • Lack of platelets can cause excessive bleeding or bruising.

35. Cells differentiate and become specialised. These specialised cells form tissues, which form organs, which form organ systems. Large multicellular organisms have different systems inside them for exchanging and transporting materials. Tissues (muscle tissue) is a group of similar cells that work together to carry out a particular function. Organs (heart) is a group of different tissues that work together to perform a particular function. Organ system (circulatory system) is a group of organs working together to perform a particular function.

36. Structure of the heart Four chambers : Right and Left Atrium & Right and Left Ventricle. Four blood vessels : Pulmonary artery and Pulmonary vein & Vena cava and Aorta.

37. Flow of blood through the heart The right atrium of the heart receives deoxynated blood from the body (through the vena cava). The deoxynated blood moves through to the right ventricle, which pumps it to the lungs (through the pulmonary artery). The left atrium receives oxygenated blood from the lungs (through the pulmonary vein). The oxygenated blood then moves through to the left ventricle, which pumps it out round the whole body (via the aorta). The left ventricle has a much thicker wall than the right ventricle. This is because it needs more muscle to pump high pressure blood around the whole body instead of the right just pumping it to the lungs. The valves prevent the backflow of blood.

38. Arteries – carry the blood away from the heart under high pressure. • Artery walls are strong and elastic • The walls are thick compared to the size of the lumen. • They contain thick layers of muscle to make them strong. • Capillaries – they are involved in the exchange of materials with the tissues. • They are really tiny. • They carry the blood really close to every cells in the body to exchange substances with them. • They have permeable walls, so substances can diffuse in and out. • They supply food and oxygen, and take away wastes like CO2. • Their walls are usually only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs. • Veins – these carry blood to the heart. • The blood is at lower pressure in the veins so the walls don’t need to be as thick as the artery walls. • They have a bigger lumen to help the blood flow despite the low pressure. • They also have valves to help keep the blood flowing in the right direction.

39. Digestive Enzymes Carbohydrases(e.g amylase) digest starch into sugars Proteases (e.g. pepsin) digest proteins to amino acids Lipase digest fat into fatty acids and glycerol.

41. Mouth • Food is covered in saliva from the salivary glands. • Salivary glands produce amylase enzymes in the saliva which breaks down starch. • Food is chewed to form a bolus (ball of food) before swallowed. • Oesophagus • A tube that takes food from the mouth to the stomach. • It is lined with muscles that contract to help the bolus move along by peristalsis (It is a series of smooth muscle contractions and relaxations moving food in a wave-like manner through the digestive tract) • Liver • Where bile is produced. • Bile neutralises stomach acid and emulsifies fats , separating them into small droplets so the body can use them as nutrients. It also acts an antitoxin that helps the liver to remove toxins out of the body. • Gall Bladder • Where the bile is stored, before it it’s released into the small intestine. • Large Intestine • Where excess water is absorbed from the food.

42. Small Intestine • Produces protease, amylase and lipase enzymes to complete digestion. • To allow absorption of nutrients. • It’s covered in tiny villi. These are microscopic, finger-like protrusions which give the lining of the small intestine a massive surface area for absorption of nutrients to occur across much more quickly into the blood. The microvilli give the inside of the intestine the look and feel of velvet. • They have a single layer of surface cells so that digested food diffuses quickly over a short distance. • Each villus contains a minute blood capillary. When nutrients are absorbed into a microvillus, they enter its blood capillary. This is how nutrients from your food enter your blood which assist to quick absorption. • Stomach • It churns and pummels the food with its muscular walls. • It produces the proteases enzyme, pepsin. • Pancreas • Produces protease, amylase and lipase enzymes. It releases these into the small intestine.

43. Functional Foods are marketed as having health benefits. • Probiotics • They are live bacteria, such as Bifidobacteria and Lactobacillus (a lactic acid bacterium) . These ‘good’ bacteria similar to those found naturally in the gut. • Added to foods such as yogurt, soya milk ang dietary supplements ( e.g. capsules) • It’s said to help keep your digestive system healthy and your immune system strong. • Prebiotics • They are carbohydrates that we can’t digest . e.g oligosaccharides • They occur naturally in foods like leeks, onions and oats. • Prebiotics are a food supply for ‘good’ bacteria that are already in digestive system. • Thought to help growth of good bacteria in the gut. • Plant Stanol Esters • They are chemicals that can lower blood cholesterol and reduce the risk of heart disease • Stanols occur naturally in plants. They are produced commercially by using bacteria to convert sterols into stanols. • Added to spreads and dairy products.