Bio

• Mass transport system


  • A network to move through (eg. vessels)
  • A medium for movement (a fluid eg. blood)
  • Controlled direction - to move substances to / from where they are needed (eg. blood is moved along a pressure gradient created by the heart, the direction of flow controlled by valves)
  • Maintenance of speed - (eg. contraction of the heart + elastic recoil of arteries helps to maintain the pressure gradient, thus speed)
• Water


  A polar molecule, due to uneven distribution of charge within the molecule – the hydrogen atoms have a partial positive charge and the oxygen atom has a partial negative charge due to the difference in electronegativity, causing one end of the molecule to be more positive than the other
• Water


  A polar solvent and can be used to transport many biological molecules (as many of them are also polar, thus can be dissolved in water)
• Hydrogen bonding


  Creates cohesion and adhesion, which enables effective transport of water and dissolved substances through xylem vessels
• Hydrogen bonding


  A relatively strong type of bonding, thus causing water to have a high heat specific capacity meaning that a lot of energy is required to change the temperature of water, therefore minimising temperature fluctuations in living things (an important part of homeostasis)
• Arteries


  • Carry oxygenated blood to the body tissues (other than the pulmonary artery)
  • Have a small lumen to maintain high blood pressure
  • Smooth inner endothelial lining (a smooth surface means there's less resistance to blood flow)
  • Thick layer of smooth muscle ( contract and relax to dilate and constrict blood vessels - controlling their diameter) and elastic fibres ( stretch and recoil )
  • Lots of collagen fibres (for strength and support )
• Veins


  • Carry deoxygenated blood to the lungs (except the pulmonary vein)
  • Large lumen (minimises resistance to flow)
  • Thinner layer of muscle and elastic fibres
  • Reduced collagen fibres
  • Valves (to prevent backflow)
• Capillaries


  • Very small (to fit between cells)
  • Narrow Lumen
  • Thin endothelium
  • one cell thick (to maintain short diffusion distance and fit between cells)
• Heart and Cardiac Cycle

  • Four chambers - right and le atria , right and le ventricles
  • Four main blood vessels pulmonary vein (from lungs to le atrium) , aorta (from le ventricle to body), vena cava (from body to right atrium), pulmonary artery (from right ventricle to lungs)
  • Atrioventricular valves - mitral or tricuspid/bicuspid - separate atria from ventricles
  • Semilunar valves - pulmonary/aortic - separate arteries from ventricles
  • Tendinous chords /valve tendons - prevent atrioventricular valves turning inside out due to pressure
  • Septum - muscle and connective tissue - prevents oxygenated/deoxygenated blood mixing
  • Coronary arteries - wrapped around the heart to supply blood to cardiac muscle
  • Cardiac muscle - thicker on the LHS because higher pressure is needed to pump blood further
• Cardiac Cycle


  1. Atrial systole – during atrial systole the atria contract forcing the atrioventricular valves open and blood flows into the ventricles

  2. Ventricular systole – contraction of the ventricles causes the atrioventricular valves to close and semilunar valves to open thus allowing blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery

  3. Cardiac diastole – atria and ventricles relax and pressure inside the heart chambers decreases causing semilunar valves in the aorta and pulmonary arteries close, preventing backflow of blood
• Atherosclerosis


  The hardening of arteries caused by the build-up of fibrous plaque called an atheroma
• Atheroma formation


  1. The endothelium which lines the arteries is damaged, for instance by high cholesterol levels, smoking or high blood pressure

  2. This increases the risk of blood cling in the artery and leads to an inflammatory response causing white blood cells to move into the artery

  3. Over me , white blood cells, cholesterol, calcium salts and fibres build up and harden leading to plaque (atheroma) formation

  4. The build-up of fibrous plaque leads to narrowing of the artery and restricts blood flow thus increasing the blood pressure which in turn damages the endothelial lining and the process is repeated - an example of positive feedback
• Risk factors for atherosclerosis

  • Genetics (genetic predisposition to high blood pressure etc.)
  • Age (arteries become less elastic with age)
  • Diet (diet can increase cholesterol)
  • Gender (oestrogen makes arteries more elastic)
  • High blood pressure (can damage endothelium)
  • High cholesterol levels (increases the likelihood of formation of plaque)
  • Smoking (nicotine narrows arteries)
  • Physical inactivity (increases obesity risk)
  • Obesity (increases blood pressure etc.)
• Risk of CVD can be reduced by stopping smoking, regular exercise, reducing consumption of alcohol, dietary changes and maintaining healthy body weight
• Thrombosis


  Also known as blood clotting, prevents blood loss when a blood vessel is damaged, it also prevents the entry of disease causing microorganisms and provides a framework for repair
• Blood clotting


  1. When a blood vessels is damaged, platelets attach to exposed collagen fibres

  2. A protein called thromboplastin is released from platelets and this protein triggers the conversion of inactive prothrombin which is a protein into active thrombin which is an enzyme. In order for the conversion to occur calcium ions and vitamin K must be present. These are known as clotting factors

  3. Thrombin catalyses the conversion of soluble fibrinogen into insoluble fibrin

  4. Fibrin forms a network of fibres in which platelets & red blood cells are trapped to form a blood clot
• Energy balance


  The balance of calories consumed through eating and drinking, compared to calories burned through physical activity
• If a greater number of calories is burned through physical activity than is consumed it leads to weight loss
• If fewer calories are burned than consumed it leads to weight gain
• Ways of determining whether an individual is overweight, underweight or healthy weight

  • BMI is the body mass index which can be calculated by dividing the body mass in kilograms by height in metres squared. The value obtained is then compared to a chart, for instance a value below 18 indicates that the individual is underweight, while a value above 30 indicates the individual is obese
  • Waist-to-hip ratio can be used to determine how likely a person is to get heart disease based on the distribution of fat in the body. A value above 1 suggests a health risk
• Carbohydrates


  Molecules which consist only of carbon, hydrogen and oxygen. They are long chains of sugar units called saccharides
• Types of saccharides


  • Monosaccharide = simple sugar monomer
  • Disaccharide = two monosaccharides
  • Polysaccharide = many monosaccharides
• Formation of disaccharides and polysaccharides

  Monosaccharides can join together to form disaccharides and polysaccharides by glycosidic bonds which are formed in condensation reactions (in which a molecule of water is removed)
• Glucose


  A monosaccharide containing six carbon atoms in each molecule and is the main substrate for respiration
• Isomers of glucose


  • Beta glucose (most common in plants)
  • Alpha glucose (most common in animals)
• Ribose


  A monosaccharide containing five carbon atoms, it is a pentose sugar and a component of DNA and RNA
• Maltose


  A disaccharide formed by condensation of two glucose molecules
• Sucrose


  A disaccharide formed by condensation of glucose & fructose
• Lactose


  A disaccharide formed by condensation of glucose & galactose
• Glycogen


  The main energy storage molecule in animals and is formed from many molecules of alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds
• Glycogen


  It has a large number of side branches meaning that the molecule can be hydrolysed and energy can be released quickly
• Glycogen


  Relatively large, but compact molecule thus maximising the amount of energy it can store
• Starch


  Stores energy in plants and it is a mixture of two polysaccharides called amylose and amylopectin
• Amylose


  An unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, as a result of that amylose is coiled and thus it is a very compact molecule meaning it can store a lot of energy
• Amylopectin


  Branched and is made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds, due to the presence of many side branches it is rapidly digested by enzymes therefore energy is released quickly. It is also a compact molecule, although not as compact as amylose
• Lipids


  Biological molecules which are only soluble in organic solvents such as alcohols
• Types of lipids


  • Saturated lipids such as those found in animal fats – saturated lipids don't contain any carbon-carbon double bonds
  • Unsaturated lipids which can be found in plants – unsaturated lipids contain carbon-carbon double bonds and melt at lower temperatures than saturated fats
• Intermolecular forces


  Weaker in unsaturated lipids and therefore they have a lower melting point
• Double bonds in unsaturated lipids

  Reduce the strength of these intermolecular forces (as they create a 'kink' in the hydrocarbon chain, so molecules cannot pack together as closely)
• As a result, saturated fats are solid at liquid temperature and unsaturated lipids are liquid at room temperature