REVISION CARDS Biology www.biologyinfo.co.uk Modified 15/02/2015 (PB)
Index Topic 1 2 Microscopes 3 Plant cells 4 Animal cells 5 Bacteria cells 6 Double Helix 7 DNA 8 Genetic engineering 9 Mitosis 10 Meiosis 11 Cloning 12 Protein synthesis 13 Enzymes 14 Lock and Key Topic 2 15 Aerobic respiration 16 Heart rate and Breathing 17 Anaerobic respiration 18 Plant leaves 19 Photosynthesis 20 Roots 21 Ecosystems Topic 3 22 Fossil records 23 Growth 24 Blood 25 Cells, Tissues, Organs 26 Heart 27 Circulatory system 28 Digestive system 29 Digestive enzymes 30 Functional foods
Topic 1 Microscopes Changes in microscope technology, improved lighting, better lenses, digital cameras etc. enable cells to be seen with more clarity and detail than before. Light microscopes allow objects to be magnified up to at least 2,000 times. Eyepiece Objective Total Magnification 10 x 4 x 40 x 10 x 10 x 100 x 10 x 40 x 400 x 10 x 100 x 1000 x The magnification of the eyepiece multiplied by the objective gives the total magnification. 1.4 1.5 3
Topic 1 Plant cell 1.2 Mitochondria: Converts the energy stored in glucose for use in the cell Large Vacuole: Water filled space that stores chemicals that exerts pressure against the walls. Cell wall: Composed of cellulose this provides both protection and structure Nucleus: Controls many functions of the cell and contains the DNA Cytoplasm: Stores chemical and maintains the shape of the cell. Cell membrane: A thin semipermeable membrane that surrounds the cytoplasm Chloroplast: Where photosynthesis takes place. Contains chlorophyll. 4
Topic 1 Animal cell Cytoplasm: Stores chemical and maintains the shape of the cell. 1.3 5
Topic 1 Bacteria cell Chromosomal DNA: carries genes that specify the proteins that make up the organism. Flagella: allow the cell to move 1.1 1.8 Cell wall Plasmid DNA: Non-essential small circles of DNA containing between 5 and 100 genes. DNA can be extracted from many types of cells: Grind a piece of tissue (onion) to break it open. Add salt solution (NaCl) and detergent - these solutions break down and emulsify the fat & proteins that make up a cell membrane. Add alcohol. Because DNA is soluble in water, the alcohol causes DNA to precipitate out of the solution, leaving behind all the cellular components that aren't soluble in alcohol. DNA can then be wound on a stirring rod and pulled from the solution. 6
Topic 1 Double Helix DeoxyriboNucleicAcid and the linking between Adenine and Thymine (A=T), Cytosine and Guanine (C=G) were know to exist years before the discovery by James Watson and Francis Crick. They, based in Cambridge, were in competition with others in America and around the World to determine the 3D structure of the molecule. Maurice Wilkins and Rosalind Franklin in London were using X-ray crystallography to try to determine the shape and structure of DNA. Wilkins shared Franklin s research with Watson and Crick, helping them to make the vital breakthrough. 1.9 1.10(H) The Human Genome Project: An international research project set up at the Sanger Institute to determine the sequence of chemical base pairs that make up human DNA. 7
Topic 1 DNA The DNA molecule consists of two strands coiled to form a double helix. These strands are linked by a series of complementary base pairs joined together by weak hydrogen bonds: i adenine (A) with thymine (T) ii cytosine (C) with guanine (G) 1.6 1.7 A gene is a section of a molecule of DNA that codes for a specific protein 8
Topic 1 Genetic Engineering Genetic engineering involves the removal of a gene from the DNA of one organism and the insertion of that gene into the DNA of another. For example, special bacteria can have a human gene inserted allowing them to manufacture insulin that can be used by Diabetes sufferers. Herbicide resistant crops allow non-specific sprays to be used to control weeds. However, there are concerns that sprays will be used more often, that the weeds too will become resistant and that there will be negative impacts on wild plants and biodiversity of farming. Easy to grow, genetically modified Golden Rice contains beta carotene which helps to reduce vitamin A deficiency and to prevent blindness in children in areas of Asia and Africa. There is though a risk that high dependency on one crop will reduce biodiversity in these areas and some widely respected organisations, such as Greenpeace, are strongly opposed to the introduction of any GM organisms. 1.11 1.12 9
Topic 1 Mitosis Mitosis: results in two daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell. This results in the formation of two genetically identical diploid body cells. Mitosis occurs during growth, repair and asexual reproduction 1.13 1.14 1.17 Cloning is an example of asexual reproduction that produces genetically identical copies 10
Topic 1 Meiosis Meiosis: The production of four daughter cells (genetically different haploid gametes), each with half the number chromosomes At fertilisation, haploid gametes combine to form a diploid zygote 1.15 1.16 11
Topic 1 Cloning 1.18(H) 1.19 1.20 1.21 Remove a diploid nucleus Egg removal Egg Cell Enucleation of egg cell Implant into surrogate Stem cells in the embryo can differentiate into all other types of cells but lose this ability as the animal matures. Electrical stimulation Normal mitosis Stem cells removed Cloning is notoriously difficult and risky, this will improve with time. Advantages: Offspring will all have the same (modified) genetic characteristics. Risks: Increased chance of genes behaving abnormally, increased risk of infection and cancer. Disadvantages: Cloned animals often have enlarged organs. Stem cell research has similar problems and also raises a lot of ethical concerns 12
B1 Topic 1 Protein synthesis Transcription: mrna is produced in the nucleus, it carries complimentary genetic information from the DNA to the ribosome. The mrna carries specific triplets of bases (codons) that code for specific amino acids. Translation: trna carries these amino acids to the ribosome where the amino acids link to form polypeptides in an order decided by the mrna (or ultimately the base order of the DNA). The order of bases in a section of DNA therefore decides the order of amino acids in the protein. Each protein has its own specific number and sequence of amino acids, resulting ultimately in different-shaped molecules that have different functions, including enzymes. trna 1.22 1.23(H) 1.24 1.25 Gene mutations change the DNA base sequence, these mutations can be harmful, beneficial or neither. 13
Topic 1 Enzymes Enzymes are biological catalysts that catalyse chemical reactions occurring inside and outside living cells: In protein synthesis, enzymes catalyse the production of amino acids, the joining of amino acids to form peptides and finally proteins. In DNA replication, enzymes are involved in the unwinding of the DNA, the breaking up of the strands, replication of new strands and the joining together / rewinding of the new DNA 1.26 1.27 Pepsin catalyses the break down of food proteins in the stomach and has to operate in an acid environment (ph 2) whilst Trypsin, which also catalyses the break down of proteins, works in the alkalinity of the intestine (ph8). 14
Topic 1 Lock and key Enzymes are highly specific for a particular substrate molecule. The lock and key hypothesis is a good analogy for the way that the active site on the enzyme molecule works. The enzyme can be denatured, this results in a change of shape of the active site, meaning that it no longer works effectively. Changes can be caused by low substrate concentrations, high (or low) temperature and changes in ph. 1.28 1.29 1.30 1.31 1.32 15
Topic 2 Aerobic Respiration The human circulatory system facilitates respiration: glucose and oxygen diffuse from capillaries into respiring cells carbon dioxide diffuses from respiring cells into capillaries Respiration: A process used by all living organisms that releases the energy in organic molecules. Can be represented by the following word equation: Osmosis: The movement of water molecules from an area of higher concentration of water to an area of lower concentration of water through a partially permeable membrane 2.1 2.2 2.3 2.4 16
Topic 2 Heart rate & Breathing Exercise increases both breathing rate and heart rate. The volume of blood pumped per minute (cardiac output of the heart) is calculated from the stroke volume (output of the left ventricle) x heart rate (pulse) Exercise increases the need for energy / additional glucose and oxygen in the body. Breathing increases to rid the body of the carbon dioxide produced by respiration and to provide more oxygen. Heart rate will increase to provide the extra food and oxygen needed. 2.5 2.6 2.7 2.12 Recovery time is also known as the amount of time it takes the human body to repay an oxygen debt. A person in poor physical shape will require much more recovery time to keep exercising. 17
Topic 2 Anaerobic respiration Anaerobic respiration releases energy from glucose: During vigorous exercise, muscle cells may not receive sufficient oxygen for their energy requirements and so start to respire anaerobically. Lactic acid builds up Aerobic respiration releases approximately 16 x more energy than anaerobic respiration. 2.8 2.9 2.10 2.11 A build-up of lactic acid requires extra oxygen to break it down. This is called excess post-exercise oxygen consumption or EPOC (formerly known as oxygen debt) 18
Topic 2 Plant leaves Leaves are adapted for photosynthesis: They have a large surface area to capture light. Chlorophyll in chloroplasts absorb sunlight. Stomata in the underside of the leaf allow gas exchange (carbon dioxide, oxygen and water vapour) Photosynthesis uses light energy to produce glucose: 2.13 2.14 (You only need to know the word equation) 19
Topic 2 Photosynthesis There are various limiting factors that affect the rate of photosynthesis: Light Carbon Dioxide Temperature The loss of water vapour from leaves drives transpiration 2.15 2.16 2.17 2.18 Xylem vessels transport water and minerals in one direction from the roots to the rest of the plant. Movement is facilitated by the negative pressure created by the replacement of water lost through transpiration. Phloem translocates sugars from photosynthesis to storage organs due to hydrostatic / diffusion pressure created in cells. Minerals are taken up in the roots by active transport 20
Topic 2 Roots Water passes from an area of high concentration to the next cell (low water concentration) by osmosis. In this way water continues to move along the cells of the root up the xylem to the leaf. All the time water is moving to areas of lower water concentration Osmosis can be investigated using various sugar solutions and discs or chips of potato 2.19 2.20 2.21 2.22 Root hairs have a large surface area. The cell membrane acts as a partially permeable membrane (the cell wall is fully permeable) and, because the cell sap inside the vacuole is a concentrated solution, water passes from the soil into the root hair cell by osmosis. 21
Topic 2 Ecosystems Pooters: Using the tube, airborne insects are drawn into the container. Thermometer: Measures temperature. Pond nets: Used to dip for insects in ponds 2.23 Sweep nets: Waved through shrubs, these will collect larger insects Pitfall traps: Used to collect insects and small animals. All can be used to investigate the relationship between organisms and their environment. Light meter: Used to measure the intensity of light incident on surfaces. Quadrats: Sample a select area randomly in a larger area ph meter: To measure acidity / alkalinity of water and soil. 22
Topic 3 Fossil record Fossils that can be dated show clear evidence of evolution. There is still much to be found and some things, like soft tissue are rarely found, hence there are gaps in the fossil record: The pentadactyl limb, with 5 fingers, is common to most four limbed creatures - humans, mammals, birds, dinosaurs, other reptiles and amphibians. It is seen as evidence of a common ancestry. Darwin noted this in his Origin of Species. 3.1 3.2 3.3(H) 23
Topic 3 Growth Growth is an increase in size, length and mass of an organism Plants grow mainly by cell enlargement / elongation and can often grow continuously. Many plant cells are able differentiate. Growth data is often expressed in terms of percentile charts: 3.4 3.5 3.6 3.7 As animals grow, the number of cells tend to increase, cells divide and change from embryonic stem cells to become more specialised cell types which then loose the ability to differentiate. Animals tend to grow to a maximum size. 24
Topic 3 Blood Red blood cells: Have a unique shape for their function which is carrying oxygen and carbon dioxide around the body, White blood cells: Also called leucocytes, these play an important role in the immune system and help protect against disease 3.8 Platelets: Contain proteins on their surface that allow them to stick together and fill breaks in a blood vessel. Plasma: A watery liquid that suspends red blood cells, white blood cells and platelets. Also transports dissolved gases, proteins, nutrients and waste products. 25
Topic 3 Cells, tissues, organs Organs: Heart, lungs, liver etc. 3.9 A group of cells working together is defined as a tissue and several tissues working together comprise an organ. An organ system would be a group of organs working together such as the cardiovascular or digestive systems. Tissue: For example muscle cells 26
Topic 3 Heart Valves in the heart help ensure that the blood only flows in one direction. The right atrium and ventricle pump deoxygenated blood through the pulmonary artery to the lungs where oxygenated blood returns through the pulmonary vein (veins take blood to the heart) 3.10 The left atrium and ventricle (which has a thicker muscular wall than the right) pump oxygenated blood out through the aorta around the body. Deoxygenated blood returns through the inferior and superior vena cava 27
Topic 3 Circulatory system The circulatory system transports substances around the body: Arteries transport blood away from the heart Veins transport blood to the heart Capillaries exchange materials with tissues 3.11 28
Topic 3 Digestive system The mouth breaks up food and starts the digestive process. The oesophagus transports food and fluid, after being swallowed, from the mouth to the stomach which churns the food and releases acids and enzymes to break it down. Most digestion and absorption occurs in the small intestine and finally food passes via peristalsis into the large intestine where the faeces are formed. Peristalsis: The muscular wall behind a bolus of food in the alimentary canal contracts and in front it relaxes. The resulting wave forces food down the oesophagus. 3.12 3.13 3.15(H) Mouth Liver Gall bladder Large Intestine (Colon) The pancreas aids digestion and regulates blood sugar. The liver produces bile which is held in the gallbladder. When released into the small intestine, bile neutralises stomach acid and emulsifies /helps to breakdown fats. Oesophagus Stomach Pancreas Small intestine 29
Topic 3 Digestive enzymes Villi in the small intestine, with their large surface area, single layer of cells and capillary network, allow efficient absorption of the soluble products of digestion. Enzymes play an important role in digestion: Lipase digests fats to fatty acids and glycerol Proteases, including pepsin, digest proteins to amino acids Carbohydrases, including amylase, which digest starch to simple sugars 3.14 3.16(H) 3.17 Rates of reaction can be investigated by changing the concentrations of digestive enzymes, using models such as visking tubing. 30
Topic 3 Functional foods Probiotics contain Bifidobacteria and Lactobacillus (lactic acid bacteria), such as Activia and Yakult, are live bacteria and yeasts, usually described as friendly bacteria. Whilst these have some resistance to stomach acid and anti-bacterial properties, there is limited evidence to support the claims made by these foods they are not medicines. Prebiotic oligosaccharides are simple sugars found in plants like beans and vegetables. They are reported to stimulate the growth of bacteria that are beneficial to the well-being of the body. Plant stanol esters, found naturally in fruits, vegetables, nuts, seeds, cereals, and vegetable oils are known to help block the absorption of cholesterol in the blood. 3.18 31
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