Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Designer baby wikipedia , lookup
Genetic engineering wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Point mutation wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Year 11 Biology Revision Notes. Module B3 Living and Growing. Molecules of life What’s in a cell? Nucleus – contains genetic information, this is carried on chromosomes Cell membrane – controls movement of substances in and out of the cell Cytoplasm – where many chemical reactions happen Mitochondria – cell respiration is carried out here. Energy is released from glucose in the presence of oxygen. DNA code DNA is found in the nucleus. Forms structures called chromosomes. A section of a chromosome is called a gene. Each gene is a code for making proteins. Our bodies need proteins to grow and make proteins. Everyone has his or her unique DNA code. DNA – double helix; complimentary base pairs (adenine – thymine; cytosine – guanine) Need proteins for: Growth, repairing new cells, building structures such as muscle, bone, skin, hormones, enzymes Genetic code controls how enzymes are made in your cells, enzymes control chemical reactions in the body, and will control your characteristics. 1 Year 11 Biology Revision Notes. Module B3 Living and Growing. History of DNA: 1953 Watson and Crick worked out DNA structure Genes code for proteins. The double stranded DNA helix is in the nucleus, and contains the base code which determines which proteins are made at the ribosomes. The DNA cannot leave the nucleus so it’s base pairs separate and the strand unzips to form two single DNA strands. A copy is made of part of one strand of the DNA, now called the messenger RNA. This single strand leaves the nucleus and goes to the ribosome. The order of bases found in a section of DNA is called the base code with each THREE bases code for an amino acid. At the ribosome the code is read and the correct amino acids are put together in the correct order. The sequence of the amino acids in the protein chain determines the shape that the protein will fold up into. Proteins determine your characteristics- The fact that proteins are folded in a specific way giving them a specific shape, means that they have a particular function. Therefore the genes you inherit determine what types of proteins your body makes and thus control your characteristics Important proteins Collagen vessels - found in skin, bones, tendons, ligaments, and walls of blood Insulin- Is a protein hormone which is prodcued in the pancreas, travels to the liver and muscles where is cuases blood sugar levels to be lowered Haemoglobin- Is a carrier protein in red blood cells which carries oxygen Enzymes – protein catalysts which speed up reactions in the body. Different types of cell make different proteins- all our different types of cell have the same DNA but they make different proteins. This is because they only have the genes switched on which results in the production of specific enzymes (made of protein) e.g. pancreas cells only have genes swtiched on which result in the production of insulin. Some genes do not make proteins but control the switching on or off of other genes. Enzymes Enzymes are biological catalysts – they speed up a biological reaction. 2 Year 11 Biology Revision Notes. Module B3 Living and Growing. Involved in the following reaction: photosynthesis, respiration, protein synthesis Each enzyme is specific to a substrate. Enzymes can join substrate molecules together to make a larger molecule, or can break substrates down into something smaller. (pictures are HT) The substrate molecules are changed into product molecules. Enzyme controlled reactions are affected by pH and temperature. Optimum pH or temperature – the pH / temperature where the reaction works best. Lock and key theory- each enzyme has a unique sequence of amino acids – therefore each enzyme has a different shape. Within this shape is a structure called an active site. Only one type of substrate can fit into the active site, this makes enzymes specific to a reaction. Once the substrate is attached to the active site it is turned into a product. The enzyme is like a lock and the substrate is like the key. Low temperatures and enzymes: Low temperatures mean that the enzyme active site and the substrate have less kinetic energy and so there are less collisions between them the reaction is slower High temperatures and enzymes: There is a double in reaction rate for every 10 degrees Celsius increases as there is more kinetic energy and the substrate collides more frequently with the enzyme active sites. Higher temperatures and enzymes- Denaturing enzymes If the shape of an enzyme changes it can no longer catalyse a reaction because the substrate can no longer fit into the active site. The enzyme has become denatured. Enzymes can be denatured by: Extremes of pH High temperatures 3 Year 11 Biology Revision Notes. Module B3 Living and Growing. Proteins and mutations Gene mutation- is a change in a gene which can occur spontaneously (by itself) or by chemicals such as tar in cigarettes, x-rays or UV light (sunlight) HT- a mutation in a gene (a change in a base pair) results in a different protein being made which cannot do its normal job Harmful mutations- cause cells to keep dividing (cancer), different shaped haemoglobin (disease called sickle cell anaemia) Useful mutations – pale skin is a mutation (people all used to have dark skin) and pale skin lets more light to make vitamin D (prevents rickets- soft bone disease) which is useful for people who live in countries where the sun is not strong Neutral mutations (not good or bad)- Tongue rolling is due to a gene mutation Energy and life processes Energy is the ability to do work Plants use light energy to make food and store it Animals eat food containing stored energy Building large molecules from smaller ones- plants make proteins out of long chains of amino acids. Plants join sugar molecules they make in photosynthesis into starch (stored in the plant), whereas animals join sugars to make glycogen (store energy in animals). Fatty acids and glycerol are joined in animals and plants to form lipids. Energy is needed for – muscle contraction or animals to move, and for animals such as birds and mammals to keep their bodies warm. These animals need to eat more food to make heat energy than cold blooded animals such as snakes that get heat from the sun to warm their body up. Energy is released from food by a process in cells called RESPIRATION OXYGEN + GLUCOSE CARBON DIOXIDE + WATER (+ ENERGY) C6H12O6 + 6O2 6CO2 + 6H2O (balance with 666- the sign of the devil) 4 Year 11 Biology Revision Notes. Module B3 Living and Growing. AEROBIC RESPIRATION HAPPENS ALL THE TIME IN PLANTS AND ANIMALS BUT ANAEROBIC RESPIRATION (WITHOUT OXYGEN) ONLY HAPPENS WHEN THE CELLS ARE NOT GETTING ENOUGH OXYGEN Anaerobic respiration Glucose lactic acid (+ a little bit of energy, less than aerobic respiration) Respiratory quotient is calculated RQ = volume of carbon dioxide produced volume of oxygen consumed If the amount of carbon dioxide produced is the same as oxygen used, the RQ value =1. If the cell is not getting enough oxygen, the RQ value will be greater than 1. Rate of respiration increases during exercise as your muscle cells need to get more oxygen and to get rid of more carbon dioxide Respiration is controlled by enzymes so if you warm up before hard exercise, respiration will happen faster. However, if there is increase anaerobic respiration more lactic acid is released, pH goes down and this reduces the rate of respiration muscles get tired and hurt Oxygen debt- when you have exercised using a lot of anaerobic respiration lots of lactic acid is produced. This needs to be broken down by oxygen, so when you finish exercising you carry on breathing hard and fast to supply enough oxygen to break down the lactic acid oxygen debt Blood Comprised of: Plasma – a yellow liquid, adapted to transport dissolved substances such as water, hormones, antibodies and waste products Red blood cells – transport oxygen around the body. Red colour comes from haemoglobin. Oxygen joins to the haemoglobin to form oxyhaemoglobin, which allows it to be transported around the body. They do not have a nucleus – this leaves more room to carry oxygen. They are disc-shaped and have a dent on both sides – this allows them to absorb a lot of oxygen. They are very small so they can carry oxygen to all parts of the body. White blood cells – defend the body against disease. They are adapted to change shape, they can wrap around microbes and engulf them. They can squeeze through capillary walls to reach microbes. Platelets – help to clot the blood if we cut ourselves. 5 Year 11 Biology Revision Notes. Module B3 Living and Growing. Blood vessels Blood is carried around the body in three different blood vessels. Artery – thick muscular and elastic wall to help it withstand high blood pressure as the blood leaves the heart. Vein – large lumen (hole) to help blood flow at low pressure; valves stop blood from flowing the wrong way. Capillary – thin, permeable wall to allow exchange of material with body tissue The Heart Structure Four chambers Two atria – receive blood from the veins Two ventricles – pump blood into arteries Valves – bicuspid, tricuspid, semi-lunar valves – prevent the blood flowing backwards when the heart relaxes and so maintain blood pressure. Four key vessels Right hand side: o vena cava, pulmonary artery Left hand side: o pulmonary vein, aorta Function The heart pumps blood around the body. There are two sides to a heart. 6 Year 11 Biology Revision Notes. Module B3 Living and Growing. The right side pumps blood to the lungs The left side pumps blood to the rest of the body The blood leaves the heart in arteries where the pressure is high. The blood returns to the heart at low pressure in the veins. Double circulation- we are said to have a double circulatory system as blood goes through the heart twice. Once on its way to the lungs, and once before it travels around the body Divide and rule Every day new cells are made. To do this the body carries out cell division. Cells divide whenever the body needs to: Grow Replace worn out cells Repair damaged tissue Inside the nucleus of a human body cell there are 46 chromosomes. Humans have 23 pairs of chromosomes. The chromosomes in a pair look the same and carry similar information. When a cell has pairs of chromosomes it is called a diploid cell. During growth a type of cell division called mitosis makes new cells. The new cells are exact copies and contain 23 pairs of chromosomes. Mitosis 1. Cell resting 2. Each chromosome is copied, the single strand forms double-stranded “X” shape 3. Spindle forms, chromosomes arranged along equator 4. Chromosome single strands move to poles of cell 5. Two genetically identical cells are produced. 7 Year 11 Biology Revision Notes. Module B3 Living and Growing. 6. Human eggs and sperm These are our sex cells or gametes. Gametes join during fertilisation. They are adapted to carry out their jobs. Much larger than the sperm because it contains food for the developing embryo The nucleus of an egg contains genes which hold the instructions to make new cells Egg Sperm Much smaller than the egg Has a tail to help it move Sperm also have a structure called an acrosome – this releases enzymes that digest the cell membrane of an egg and allows the sperm inside. Gametes have half a set of chromosomes called the haploid number. During fertilisation the gametes join to form a zygote. The zygote is diploid and can develop into an embryo (baby). When fertilisation takes place gametes from a male and female join. The resulting offspring have genes from both parents. They are different to their parents – they are new individuals. Reproduction using meiosis results in a lot of genetic variation within a species. Meiosis A special type of cell division that produces gametes. Gametes are made when diploid cells divide by meiosis to produce haploid cells. Meiosis involves two cell divisions. First the chromosomes separate then the chromosomes divide in the same way as mitosis 8 Year 11 Biology Revision Notes. Module B3 Living and Growing. Plant cells Plant cells have the following components: Nucleus –contains the genetic material (chromosomes) Cytoplasm- where cells chemical reactions take place Cell membrane- control what goes in and out of the cell Vacuole – contains cell sap and provides support Cell wall – provides support Chloroplasts – absorb light energy for photosynthesis Animal cells DO NOT have a cell wall, chloroplasts, or vacuoles Animal cell and plant cell growth For a fertilised egg to grow into an embryo and a foetus the cells need to divide and change so they can carry out different jobs. Some cells turn into nerve cells and other cells may turn into bone cells. This is called cell differentiation. The cells of animals and plants cause them to grow in different ways. Plant Animal Most growth is due to cells elongating (growing longer) not dividing Growth is due to cells dividing Cell division only normally occurs at the tips of shoots and roots Cell division occurs all over the body Many cells never lose the ability to differentiate Most animal cells lose the ability to differentiate very early on 9 Year 11 Biology Revision Notes. Module B3 Living and Growing. A few days after an egg is fertilised it contains a group of cells called stem cells. These all have the same simple cell structure. They divide and then differentiate to form all the different specialised cells in the body. As the embryo grows all the specialised cells form tissues and organs. Some stem cells are found in the adult body. Bone marrow contains stem cells that turn into different types of blood cells. Scientists have found ways of making stem cells develop into other specialised cells in the hope of replacing damaged cells. Ethically this can cause problems. People may object to stem cell research because it can involve human embryos. Scientists use embryo stem cells because they are easier to grow than adult stem cells. Human growth There are five main stages: 1. Infancy (rapid growth) 2. Childhood (slow steady rate) 3. Adolescence (puberty)- rapid growth 4. Adulthood (maturity)falls to zero New genes for old Selective breeding Choose the animals and plants with the best characteristic and breed them to produce offspring that have those characteristics. The selection and breeding process needs to be repeated for a number of generations. This process could be used to breed cows that produce a lot of milk, chickens that lay more eggs, crops that are resistant to certain diseases, crops that are resistant to flood/drought Transferring genes Scientists can take genes from one organism and put them into a different organism. These changes are called genetic engineering or genetic modification (GM) How genetic engineering works 1. Select the characteristic 2. Identify and isolate the gene 3. Insert the gene into the chromosome of a different organism 10 Year 11 Biology Revision Notes. Module B3 Living and Growing. 4. Replicate (copy) the gene in the organism and produce the protein. Enzymes are used to cut a gene out of an original chromosome and put it into a new chromosome. Examples: Insulin – a bacterium called E coli has been genetically engineered to make human insulin. Vitamin A rice – rice is the main diet for many people living in Asian countries, it does not contain vitamin A which is needed to prevent night blindness. Scientists have added the gene to make betacarotene from carrots to the rice plants. Humans eating the rice can then convert the beta-carotene into vitamin A. Some people are opposed to GM due to ethical reasons and have concerns of “playing God “with nature. Cloning Clones are genetically identical. They have the same DNA as the original animal or plant. Identical twins are natural clones – they have the same DNA. Types of cloning: Embryo transplantation Sperm is collected from the prize bull; a prize cow is artificially inseminated with the sperm. When the fertilised egg divides into an eight-cell embryo it is collected and split into four two-celled embryos. Each embryo is implanted into a surrogate cow where it grows into a calf. All the calves will be genetically identical to each other but not to their parents. Nuclear transfer Egg cell taken from sheep A and the nucleus is removed. 11 Year 11 Biology Revision Notes. Module B3 Living and Growing. An udder cell is taken from sheep B and the nucleus is removed. The nucleus from sheep B is put into the egg cell of sheep A. The egg cell is put into a sheep to grow. The cell grows into a clone of sheep B (where the nucleus containing the genetic information came from) The importance of cloning Organ supply for humans Cloning of human embryos to provide stem cells Risks Low success rate Moral / ethical issues Complications / early death of clones Benefits Cloned pigs could make up a shortage in transplant organs Diseases could be cured using embryonic stem cells Asexual reproduction in plants Plants that can do it naturally: Potato plants – tuber Strawberries – runner Spider plants – plantlets Strawberry plants has long runners and at the end baby plants grow (genetically identical to the parents plantas there is only one parent) 12 Year 11 Biology Revision Notes. Module B3 Living and Growing. New plants from old How? – take cuttings. You cut off a stem or a root from a plant and put it into soil and it will grow into an identical plant to the one you cut it from Advantages of cloning plants All the plants are genetically identical Cloning is quite. a quick process in comparison to growing plants from seeds Cloning enables growers to produce plants that are difficult to grow from seed such as bananas Disadvantages The plants are all genetically identical. If the environment changes or a disease breaks out it is unlikely any of the plants will survive. Cloning plants over the years has resulted in very little genetic variation Tissue culture Plants can be cloned using tissue culture. This must be carried out using aseptic technique 1. Plants with desired characteristics are chosen 2. A large number of small pieces of tissue are taken from the parent plant 3. They are put into sterile test tubes that contain the growth medium 4. The tissue pieces are left in suitable conditions to grow into plants 13