Original post by mordin1428So, DRAFT unofficial mark scheme (only what I remember, feel free to add and/or correct) Q 1. a) White blood cell has a cell membrane and a nucleus, no cell wallBacterial cell has a cell wall and cell membrane, no nucleusb) I A M , so actual size = image size/magnification, so (image size in mm)x10^3/30000, mine was 2.86 c) evidence for mitochondria - its own looped molecule of DNA, looks similar to bacterial cell d) advantage of mitochondria - aerobic respiration? produces ATP for metabolic processes in the cell, cell growth and repair, active transport etc. Q2a) oxygenated blood away from the heart - aorta, Cdeoxygenated blood to the heart - vena cava, A b) Ventricle has a thicker wall, so a thicker muscle layer. Thicker muscle layer means more forceful contraction and higher blood pressure c) hole between two ventricles - deoxygenated and oxygenated blood mixes, stroke remains the same volume, so instead of a full stroke of oxygenated blood, a mixture of deox. and ox. is pumped into the body --> less oxygen to cellsQ3 a) Ph meter gives a precise value, ph indicator gives a tame b) triglycerides get broken down into glycerol and fatty acids by lipase. Fatty acids lower the ph. c) ph is constant because all triglycerides have been broken down so no more fatty acids formed, so their conversation remains constant --> no change in phd) curve's gotta start from the same ph and decease less rapidly, taking no longer to reach the same ph level as the first curve in the end Q4a) rough endoplasmic reticulum/ribosomeb) not active inside the cell: trypsin is a protease - many vital proteins present within the cell, like channel proteins, that facilitate active transport, structural support etc. - if protease activates within the cell, it can break them down c) peptide bond breaks d) competitive inhibitor=shape similar to substrate - binds to active site - doesn't get broken down, so stays there - enzyme can no longer form E-S complexes - rendered uselessQ5a) Diaphragm relaxes and curves upwards - thorax and lungs collapse inwards and down - less volume in lungs so air pressure rises (above atmospheric) - air moves from area of high pressure to area of low pressure, which is outside of the body b) FEV1 of non-smokers went up by 0.05 after a year, whereas FEV1 of smokers went down by 0.05 after a year. Then FEV1 of non-smokers decreased by 0.12 after the increase and FEV1 of smokers decreased by 0.25 after the first decrease. c) scar tissue formation - loss of lung elasticity tar in cigarettes causes release of proteases - digests elastin, so less recoil and breakdown of alveoli Q6 a) milk treated with lactase to break down lactose b) first thing in the morning - nothing else in digestive tract, so provides a benchmark OR in the morning, not before sleep - can consciously become aware of the symptoms and record them c) dietary guidelines - don't eat any other dairy, foods that will cause bloating or any other symptoms (beans/peas), or lactase supplements the part about conclusions from results I put none of the symptoms are severe or even moderately severe, all of them scoring less than 2, so it may be safe for lactose intolerant people to drink small quantities of milk. Then bloating was more likely to be experienced when drinking untreated milk, whereas diarrhoea - when drinking lactose-free milk. Both untreated and lactose-free milk scored roughly equally on stomach ache. results may be unreliable because the respondents may have been biased about symptoms, not answered truthfully, not a quantitative analysis and no long-term effects studied Q7 a) No receptor protein - virus can't enter cell, so can't replicate and its RNA can't be transcribed, so it can't start harming the cells or make cells produce harmful substances and also is quickly destroyed by white blood cells (phagocytes) if it remains in the blood b) increase in plasma cells: a macrophage presenting antigens meets T-helper cell with a complimentary receptor to that antigen, cytokines activate, among others, B-cells (their proliferation and speciation) and after clonal selection many clone B-plasma cells are produced to produce antibodies to combat the viruses c) plasma transfusion: people who have been recently infected still have specific plasma cells active (that produce antibodies specific to Ebola antigen) and soluble antigens, so a transfusion will introduce those into the sufferer's blood, so that the antigens can bind to Ebola viruses d) high mutation rate=high antigen variability. A vaccine exposes a person to one set of Ebola virus antigens - highly specific antibodies and memory cells formed will only respond/are complementary to the same set of antigens. A new strain of Ebola virus can have completely different antigens, rendering the memory cells useless - primary immune response all over again Q8 a) glucose enters small intestine epithelial cells via facilitated diffusion through a carrier protein by co-transport with sodium. 1 Na+ and 1 glucose have to bind for carrier protein to change shape and release Na+ and glucose inside the cell. A concentration gradient of Na+ has to be maintained since it's facilitated diffusion (passive process). This is achieved by Na+/K+ pump that actively pumps Na+ out of cell (K+ into the cell), so there is always a higher concentration of Na+ outside of the cell, so it binds to a carrier protein again and glucose can enter the cell. b) Plasma membrane=phospholipid bilayer arranged in a fluid mosaic (fluid mosaic makes diffusion possible). Only lipid soluble or very small molecules/atoms (that can be polar) can diffuse across. Oxygen is a small non-charged molecule, so can diffuse down its conc. gradient. Chloride is strongly (negatively) charged and not lipid-soluble, so needs a channel/carrier protein.