AS Biology Unit 1

Plasma membranes
1. Mosaic - a mixture of things
2. Fluid mosaic - called this as componants can move around within the membrane
3. Glycerol and fatty acids combine by condensation to produce triglycerides.
4. The R-group of a fatty acid may be saturated or unsaturated. In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate group
Carbohydrates - Carbon based molecules combined with water. Contain elements C,H and O.
1. The 'standered sugar' - Glucose (C6H12O6)
2. Disaccharides can be formed from a condensation reaction with two monosaccharides
3. Polysaccharides can be broken down by hydrolysis reactions. A disaccharide would become its two constituent monosaccharides
4. Testing for reducing sugars
  1. Heat sugar/food with Benedict's reagent. If a reducing sugar is present, there will be a colour change from blue to brick red.
  2. If Benedict's test fails... Heat a second sample in dilute HCl, neutralise with NaHCO3, then repeat benedicts test.
5. Bonds in biochemistry
  1. Carbohydrates - Glycosidic bond
  2. Lipids - Ester link
  3. Proteins - Peptide bond
6. Unsaturated - contains double bonds between carbons
7. Sucrose is a disaccharide formed by condensation of glucose and fructose. Lactose is a disaccharide formed by condensation of glucose and galactose
8. Monosaccharides are the basic molecular unitsof which carbohydrates are composed
Inhibition of enzymes
1. Inhibitors - chemical that slows down rate of reaction in an enzyme
2. Competitve - competes for active site, non-competitive doesnt compete for active site and binds elsewhere.
3. Non competitive inhibitors bind to the enzyme changing the shape of it, meaning the substrate can no longer fit, stopping it completeing the reaction.
4. Used in industry to slow down reactions and also used in chemistry
Testing for lipids and proteins
1. Buiret test for proteins... Add a small sample of substance to a test tube and crush solid foods. Add distilled water to test tube and a few drops of buiret reagent. If a proteins is present, there will be a colour change from blue to purple.
2. Emulsion test for lipids... Dissolve your sample in approximately 5ml of distilled water and shake. Add roughly the same amount of ethanol and shake again. If a white emulsion Appears, then lipids are present.
Proteins and enzymes
1. Enzymes are specific and only work on 1 molecule/chemical so for each different job a different enzyme is needed.
2. Non competitive inhibitor - not competing for the active site attracts to the enzyme and attaches to stop it doing its job.
3. Catalysis - the acceleration of a chemical reaction by a catalyst.
4. Xray crystallography is a method of figuring out the arrangement of atoms within a crystal
5. Virtually all enzymes are proteins.
6. Induced fit model- When the enzyme and substrate form a complex, structural changes occur so that the active site fits precisely around the substrate. The reaction will take place and the product, being a different shape to the substrate, moves away from the active site. The active site then returns to its original shape.
Antibodies
1. A globular protein syntheesised by B-cells that reacts with an antigen
2. Secreted by lymphocytes and contain 2 heavy chains and 2 light chains
3. They have a hinge region to allow flexibikity and and variable region and constant region
4. Chains are held together by disulhide bridges and it is Y -shaped with 2 active sites
5. Agglutination - the clumping together of antigens by antibkdies. This stops and immobilises viruses and cells.
6. One type of antibody, the T cells, mature after having first migrated from the bone marrow to the thymus gland. The other type, B cells, migrate to and then mature in either the bone marrow or in the foetal liver or spleen. Once mature, they patrol around the blood and body, hunting for foreign antigens. T cells are involved in the cell-mediated response, whilst B cells are involved in the humoral response.
7. Four types of T cells...Killer T cells Helper T cells Suppressor T cells Memory cells
Immune system
1. Phagocytes - non specific white blood cell, engulfs pathogens and/or antigens, once engulfed it destorys them and presents antigens on its surface to activate the rest of the immune system
2. Pathogen - a disease causing organism.
3. On the surface of all cells are antigens.Your body recognises the antigens on your cells as your own so anything with different antigens stimulates an immune response
4. In an immune response, the body will recognise tan antigen as foreign and will attack it. The immune system is made up of cells that work with the body's physical and chemical barriers. It helps stop any pathogen entering your body, and your body becoming infected.
Diffusion
1. Factors affecting the rate of diffusion... High concentration gradient, short diffusion pathway, moist surface, large surface area
2. Facilitated diffusion - any form of diffusion that requires a protein like helper...
3. Carrier proteins - molecule specific - only take one molecule across
4. Channel proteins - allows any molecule through unless gated.
5. the movement of particles from an area of high concentration to an area of low concentration until the concentrations are equal.
Proteins
1. 2 types - fibrous (structural e.g. Collagen) globular ( functional e.g. Enzymes)
2. Primary - sequence of amino acids in the protein.
3. Secondary - formation of alpha helices or beta sheets.
4. Tertiary - overall 3D shape of the protein.
5. Quaternary - proteins made from more than 1 chain have this structure.
Magnification=Size of image/Actual size of object
1. To get from mm to um x1000
Microscopy
1. Resolution - clearing 2 objects close together so they can be seen as seperates
2. Magnification - an increase in the size of an objects to make it visi le to the human eye
3. Two types of electron microscopes - scanning (shows the outside) and transmission ( see inside details )
4. Scanning - must be in a vacuum so living specimens cant be observed. Is only shown in black and white. Has a lower resolving power than TEM and shows 3D image easily.
5. Transmission - must be in a vacuum so living specimens cant be observed. Image only in black and white. Specimen must be extremely thin and 2D images only.
The Digestive System
1. Mouth
  1. Teeth - Cut, grind and pulverise food, reducing it to smaller particles (buccal), which increases surface area for the action of enzymes.
  2. Tongue - Manoeuvres food for chewing and rolls food into bolus for swallowing
  3. Openings of salivary glands - saliva, pH 6.5, moistens food, mucus sticks bolus together and lubricates it for swallowing. Salivary amylase, if present, starts digestion of starch.
2. Oesophagus - 25cm Long muscular tube connecting buccal cavity and stomach. Bolus of food pushed along the oesophagus by peristaltic waves of muscle contraction.
3. Stomach - stomach lining secrete hydrochloric acid and pepsin. Smooth muscle contracts which mixes austic juice and food to make chyme. Mucus is secreted to protect from digesting yourself.
4. Pancreas - secretes pancreatic juices down the pancreatic duct. Contains alkali salts to help neutralise stomach acid and are full of enzymes.
5. Small intestine - chemical digestion, absorbs nutrients and has gentle peristaltic contractions.
6. Large intestine - absorbs water, stores faeces, has gentle peristaltic contractions and ends at the rectum.
Cardiac cycle
1. Wave of electrical activity spreads out from the SAN across both atria causing them to contract
2. The atrioventricular valve prevent the wave crossing to the ventricles.
3. The wave of electrical activity is allowed to pass through the AVN which lies between the atria
4. The AVN causes a short delay, then conveys a wave of electrical activity between the ventricles along the Bundle of His
5. The Bundle of His conducts the wave through the atrioventricular septum to the base of the ventricles where the bundle braches into smaller fibres.
6. The wave of electrical activity is released from these fibres causing the ventricles to contract quickly from the apex of the heart upwards.
7. Cardiac output=heart rate X stroke volume
Cell Structure
1. Mitochondria - Aerobic respiration. Each has a smooth outer membrane and folded inner membrane.
2. Nucleus - Contains DNA for proteins
3. Smooth Endoplasmic Reticulum - synthesises, stores and transports lipids and carbs
4. Rough Endoplasmic Reticulum - Transports proteins through the cell
5. Golgi Apparatus - Packages proteins before they are sent to destination
6. Lysosome - Makes protein molecules
7. Chloroplast - Contains chlorophyll for photosynthesis
8. Cytoplasm - Contains enzymes that speed up biochemical reactions.
9. Rigid Cell Wall - Made of cellulose to give the cell support
Oral rehydration therapy
1. cholera produces a toxin which causes Na and Cl ions to be released into the lumen, lowering water potential. water diffuses by osmosis across the epethelial cells into the lumen to even water potential but does not get reabsorbed and causes diarrhoea. ORT is given containing salts and water to replace the fluid lost.
2. rehydration therapy contains... water- to rehydrate tissues, sodium- to replace lost sodium ions, glucose- to stimulate the uptake of sodium ions and provide energy, potassium - to replace lost potassium ions and stimulate appetite, and other electrolytes - such as chloride & citrate ions to help prevent electrolyte imbalance.
Vaccinations
1. immunity - the resisting of infection
2. Passive immunity - giving antibodies to an individual. This is short lasting as once they are denatured they are gone e.g. anti venom. These are not stimulated to make memory cells.
3. Active immunity - Stimulating an immune response in a person so that memory cells are produced. These are long lasting and this is a vaccination.
4. Vaccination - Injecting someone with a substance to stimulate active immunity.
5. Herd immunity - If a large enough proportion are vaccinated, then those that aren't are still protected.
Diseases
1. Fibrosis- : The transport of chloride ions and water by the cells in the airways, lungs and gut is disrupted. This causes thick mucus to line the lungs and ducts in the gut. Because the thick mucus is not shifted easily, it is more likely that a sufferer will pick up a bacterial infection
2. Asthema - fluid and mucus collects in the airways, blocking the smaller ones. Muscles in the trachea, bronchi and bronchiole walls contract, and breathing becomes difficult
3. Emphysema-Due to constant infection, phagocytes are attracted to the lungs where they release elastase - an enzyme that breaks down the elastin in the alveoli walls, to enable them to reach the surface where the bacteria are. Without adequate elastin, the alveoli cannot stretch, so they recoil and many burst. Large air spaces appear, reducing the surface area for gas exchange and making sufferers breath more rapidly. As it progresses, patients become breathless and wheezy - they may need a constant supply of oxygen to stay alive.
4. Tuberculosis - The cause of tuberculosis is the bacterium Mycobacterium tuberculosis. Infected water droplets ejected by a sneeze or cough from a person with the active pulmonary infection, are inhaled by another person who breathes in and retains the bacterial cells.
Gas exchange in fish
1. Gills have numerous folds that give them a very large surface area. The rows of gills are called gill lamellae. The folds are kept supported and moist by the water that is continually pumped through the mouth and over the gills.
2. Fish also have an efficient transport system within the lamellae which maintains the concentration gradient across the lamellae. The arrangement of water flowing past the gills in the opposite direction to the blood is called countercurrent flow and this means that they can extract oxygen at 3 times the rate a human can.
Lifestyles and risk
1. Smoking
  1. Nicotine-This drug is absorbed readily into the blood and stimulates the nervous system to reduce the diameter of arterioles and the adrenal glands to release adrenaline. This increases heart rate and blood pressure and decreases the blood supply to the
  2. Carbon monoxide- A gas that diffuses across the alveoli into the blood and onto the red blood cells, combining with haemoglobin to form carboxyhaemoglobin. This stops the haemoglobin from becoming fully saturated.
  3. Tar - a mixture of aromatic substances, which settles on the airway linings and stimulates changes that may lead to obstructive lung disease and lung cancer.
  4. Smoking increases the concentration of blood cholesterol, which increases the risk or having heart doesease or a stroke
2. Risk - the probability that an event will occur and have a hazardous result
Osmosis
1. Osmosis is a form of diffusion in which water moves from a solution of higher water potential to a solution of lower water potential through a partially permeable membrane
2. Isotonic- Occurs when an equal solute concentration exists inside and outside the cell.
Gas exchange in the lungs
1. Lots of alveoli are supplied with gases via the trachea, splitting into two bronchi and lots of bronchioles connected to the outside by the mouth and nose.
2. The alveoli provide a large surface area through which gases can diffuse. these gases diffuse a short distance from the alveolus and the blood as the lining of the lung and the capillary are only one cell thick.
3. There is a large blood supply, which allows for oxygen to be carried away to the cells as soon as it has diffused into the blood.
4. Ventilation movement also helps maintain a concentration gradient as air is regularly moving in and out of the lungs.

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AS Biology Unit 1

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