Topic 1

• diffusion (served the needs of small organisms)


  due to the large surface area to volume ratio
• as the size of the organism increases:


  - surface area to volume ratio decreases

  - diffusion distance increases

  - metabolic rate increases
• mass transport system


  consisting of heart and circulation which moves the substances around the body and allows exchange of substances to take place
• features of a mass transport system


  1. a network to move through (e.g vessels)

  2. a medium for movement

  3. controlled direction - to move substances to/from where they are needed

  4. maintenance of speed
• water is 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 is a polar solvent


  can be used to transport many biological molecules

  (as many are also polar so can be dissolved in water)
• hydrogen bonding between water molecules


  creates cohesion and adhesion, which enables effective transport of water and dissolved substances through xylem vessels
• hydrogen bonding is a strong type of bonding


  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
• arteries


  - carry oxygenated blood to the body tissues

  - have a small lumen to maintain high blood pressure

  - smooth inner endothelial lining (less resistance)

  - thick layer of smooth muscle (contract and dilate/constrict blood vessels) and elastic fibres (stretch/recoil)

  - lots of collagen fibres
• veins


  - carry deoxygenated blood to the lungs

  - large lumen (minimised resistance)

  - thinner layer of muscles and elastic fibres

  - valves (prevent back flow)
• capillaries


  - very small (fit between cells)

  - narrow lumen

  - thin endothelium, one cell thick (maintain short diffusion distance)
• 4 chambers of the heart


  - right and left atria

  - right and left ventricles
• 4 main blood vessels


  pulmonary vein (lungs to left atrium)

  pulmonary artery (from right atrium to lungs)

  aorta ( from left ventricle to body)

  vena cava (body to right ventricle)
• atrioventricular valves


  mitral ot 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 oxygenate/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
• atrial systole


  during atrial systole the atria contract forcing the atrioventricular valves open and blood flows into the ventricles
• 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
• cardiac diastole


  atria and ventricles relax and pressure inside the heart chambers decreases causing semilunar valves in the aorta and pulmonary arteries close, prevent back flow of blood
• atherosclerosis is multi-factorial and has both modifiable/non-modifiable risk factors:


  - 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 )
• atherosclerosis can lead to ...


  CVD inclcuding angina, stroke, myocardial infarction and aneurisms
• thrombosis


  - also known as blood clotting, prevents blood loss when a vessel is damaged

  - it also prevents the entry of disease causing microorganisms and provides a framework for repair
• series of reactions that lead to a clot formation:


  - when a blood vessel is damaged, platelets attach to exposed collagen fibres

  -a protein called thromboplastin is released from platelets and this protein triggers the conversion of inactive prothrombin (protein) into active thrombin (enzyme). Calcium ions and vitamin K must be present for the conversion (clotting factors)

  - thrombin catalyses the conversion of soluble fibrinogen into insoluble into insoluble fibrin

  - fibrin forms a network of fibres in which platelets & red blood cells a trapped into a blood clot
• energy balance


  the balance of calories consumed through eating/drinking compared to energy burned through physical activity
• BMI


  - weight (kg) / height (m^2)

  - a value below 18 is underweight whereas a value above 30 is obese
• wait 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 of only carbon, hydrogen and oxygen

  - long chains of sugar units called saccharides

  - monosaccharides (simple sugar monomer)

  - disaccharides (simple sugar monomer )

  - polysaccharides (many monosaccharides )

  - monosaccharides can join together form disaccharides and polysaccharides by glycosidic bonds which are formed in

  condensation reactions (a molecule of water is removed)
• monosaccharides


  - glucose is a monosaccharide containing six atoms in each molecule and it is the main substrate for respiration

  - there are two main isomers found in living organisms: beta glucose (most common in plants) and alpha glucose (most common in animals)

  - ribose is a monosaccharide containing 5 carbon atoms, its a pentose sugar and a component of DNA and RNA
• disaccharides


  - maltose is a disaccharide formed by condensation of two glucose molecules

  - sucrose is a disaccharide formed by condensation of glucose and fructose

  - lactose is a disaccharide formed by condensation of glucose and galactose
• polysaccharides


  - glycogen is the main energy storage molecule in animals and is formed from many molecules of alpha glucose joined together baby 1,4 and 1,6 glycosidic bonds.

  - it has a large number of side branches meaning the molecule can be hydrolysed and energy can be released quickly

  - its is relatively large, but compact, maximising the amount of energy it can store

  - starch stores energy in plants and it is a mixture two polysaccharides called amylose and amylopectin
• amylose


  - amylose is an unbranched chain of glucose molecules joined buy 1,4 glycosidic bonds

  - because of that amylose is coiled

  - because of that it is compact and can store a lot of energy
• amylopectin


  - branched and 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 hydrolysed to release glucose/energy

  - it is not as compact as amylose

  - insoluble
• lipids


  biological molecules which are only soluble in organic solvents such as alcohols
• saturated lipids


  such as those found in animal fats, saturated lipids don't contain any carbon-carbon double bonds
• unsaturated lipids


  can be found in plants - unsaturated lipids contain carbon-carbon bonds double bonds and melt at lower temperatures than saturated fats
• intermolecular forces in unsaturated lipids


  - weaker in unsaturated lipids therefore have a lower melting point

  - double bonds in unsaturated lipids reduce the strength of these intermolecular forces (they create a kink in the hydrocarbon chain, so the molecules cannot pack together as closely)

  - as a result, saturated fats are solid at room temperature and unsaturated lipids are liquid at room temperature
• properties of lipids


  - lipids are waterproof because the fatty tail is hydrophobic

  - very compact and better gram-for-gram energy release than carbohydrates or proteins because more energy is stored in C-O bonds that are hydrolysed

  - lipids are non-polar and insoluble in water therefore are good for storage (don't interfere with water based reactions in cytoplasm)

  - lipids conduct heat slowly therefore provide thermal insulation