Biology: Membranes, Organelles, and Cell Structure, Exams of Biology

Download Biology: Membranes, Organelles, and Cell Structure and more Exams Biology in PDF only on Docsity! 1 [Date] AQA A LEVEL BIOLOGY Paper1 Exam Latest Update/Graded A+. 1. What is the function of the cell membrane? - Correct answer To control what enters and leaves the cell, acts as a barrier between the cell and its environment. 2. What structural feature of the cell membrane allows substances to enter/leave? - Correct answer Partially permeable 3. What is the fluid mosaic model? - Correct answer States that a membrane is a fluid structure (because phospholipids are constantly moving) with a "mosaic" of various proteins embedded in it 4. Describe the structure and function of phospholipids. - Correct answer Hydrophilic head and hydrophobic tail, arranged in a bilayer (heads face outwards, tails face inwards). Lipid-soluble substances only allowed to pass through. 5. What is the function of cholesterol in the CSM? - Correct answer Make phospholipids pack more closely together, restricting the movement of the phospholipids, making the membrane less fluid/more rigid. 6. What is simple diffusion? - Correct answer The (passive) movement of particles from an area of high concentration to an area of low concentration. 7. What is facilitated diffusion? - Correct answer The passive movement of a large/charged particle down its concentration gradient through a carrier/channel protein. 2 [Date] 8. What is the process of facilitated diffusion using a carrier protein? - Correct answer Large molecule binds to a carrier protein in membrane. 9. Protein changes shape. 10.Protein releases the large molecule on the opposite side of the membrane. 11.What is the process of facilitated diffusion using a channel protein? - Correct answer Channel proteins form pores in membrane. 12.Charged particles can diffuse down their concentration gradients to the opposite side of the membrane. 13.What are the factors affecting simple diffusion? - Correct answer Concentration gradient, thickness of exchange surface and surface area. 14.What are the factors affecting facilitated diffusion? - Correct answer Number of transport proteins and strength of gradient. 15.What is osmosis? - Correct answer Diffusion of water through a partially permeable membrane from an area of high water potential to an area of lower water potential. 16.What are the factors affecting osmosis? - Correct answer Water potential gradient. 17.Thickness of exchange surface. 18.Surface area of exchange surface. 19.Outline a method for RP3 (investigation of osmosis using potato chips). - Correct answer Produce a series of dilutions from 1M sucrose solution (of a variety of different concentrations, 0M, 0.2M, 0.4M, 0.6M, 0.8M, 1M). 20.Use a cork borer to cut potatoes into identically-sized chips. 21.Blot them dry with a paper towel and measure the mass of each using a mass balance. 5 [Date] 54.Golgi vesicle - Correct answer Small fluid-filled sac, produced by g.a. 55.Stores lipids and proteins and transports them out of the cell. 56.Lysosome - Correct answer Round organelle surrounded by a membrane. 57.Contains lysozymes, used to digest invading cells or breakdown worn out components of the cell. 58.Ribosome - Correct answer Small organelle made up of proteins and RNA. 59.Site of protein synthesis. 60.RER - Correct answer Folds and processes proteins that have been made at the ribosomes. 61.SER - Correct answer Synthesises and processes lipids. 62.Cell wall (plants) - Correct answer Usually made of cellulose (chitin, fungi). 63.Support cells and prevents them from changing shape. 64.Cell vacuole (plants) - Correct answer Found in cytoplasm. 65.Contains cell sap. 66.Membrane surrounding this is called the tonoplast. 67.Maintains pressure inside the cell, keeping cell rigid/stops wilting. 68.Prokaryotic cells - Correct answer Smaller and simpler than eukaryotic cells. 69.Plasma membrane - Correct answer Made of lipids and proteins. 70.Controls movement of substances in/out of cell. 71.Cell wall - Correct answer Made of murein (glycoprotein). 6 [Date] 72.Capsule (slime) - Correct answer Protects the bacteria from attack by cells of the immune system. 73.Flagellum - Correct answer Rotates to make the cell move. 74.Viruses - Correct answer Acellular. 75. Invade and reproduce inside the cells of other organisms. 76.What is magnification? - Correct answer How much bigger the image is that the specimen. 77.What is resolution? - Correct answer The ability of the microscope to distinguish between two points that are close together. 78.Light/optical microscopes - Correct answer Uses light. 79.Max resolution of 0.2micrometers 80.Max magnification of x1,500 81.Electron microscopes - Correct answer Use electrons. 82.Vacuum only so no living specimen. 83.Max resolution of 0.0002micrometers 84.Max magnification of x1,500,000 85.TEM - Correct answer Uses electromagnets to focus a beam of electrons through the specimen. 86.Thin specimen only. 87.SEM - Correct answer Scans a beam of electrons across the specimen. 88.3-D image. 89.Can be used on a thick specimen - but lower resolution than TEM. 7 [Date] 90.What is the process of cell fractionation? - Correct answer 1 Homogenisation - Play cells in ice-cold, isotonic, buffer solution and grind up in a blender. 91.2 Filtration - filter the solution through a gauze to separate out any debris. 92.3 Ultracentrifugation - pour the cell fragments into a tube and put the tube into a centrifuge. Spin at a low speed. The heaviest organelles (nucleus) will fall to the bottom and will form the pellets. The rest of the organelles stay suspended in the supernatant. The supernatant is drained off poured into another tube and spun again at a higher speed. The heaviest organelles (mitochondria) will fall to the bottom, forming a pellet. The process repeats. 93.3.4.4 Genetic Diversity and Adaptation - Correct answer 94.What is an allele? - Correct answer Different versions of a gene. 95.What is genetic diversity? - Correct answer The number of different alleles of genes in a species or population. 96.How is genetic diversity increased? - Correct answer Mutations in DNA. 97.Gene flow. 98.What allows natural selection to take place? - Correct answer Genetic diversity. 99.What is a genetic bottleneck? - Correct answer An event that causes a big reduction in a population. 100. What are the effects of a genetic bottleneck? - Correct answer Reduces the number of different alleles in the gene pool so reduces genetic diversity. 101. What is a type of genetic bottleneck? - Correct answer The founder effect. 10 [Date] number of stomata so there are fewer places for water to escape. Waxy waterproof cuticles on leaves and stems to reduce evaporation. 126. What is the structure of the human gas exchange system? - Correct answer Trachea. Bronchi. Bronchioles. Alveoli. (Ribcage, intercostal muscles, diaphragm). 127. What is the process of inspiration? - Correct answer Active process. 128. External intercostal and diaphragm muscles contract. 129. Ribcage moves upwards and outwards diaphragm flattens, volume of thoracic cavity increases. 130. Lung pressure decreases. 131. Air flows down the pressure gradient into the lungs. 132. What is the process of expiration? - Correct answer Passive process. 133. External intercostal and diaphragm muscles relax. 134. Rib cage moves downwards and inwards and diaphragm becomes curved again. 135. Volume of thoracic cavity decreases so air pressure increases. 136. Air is forced down the pressure gradient and out of the lungs. 137. Where does gaseous exchange occur in humans? - Correct answer Alveoli. 138. How are alveoli adapted for gas exchange? - Correct answer Lots of them, large surface area. 139. Epithelium is one cell thick, short diffusion pathway. 140. How does gas exchange take place in the alveoli? - Correct answer Oxygen diffuses out of the alveoli, across the alveolar epithelium and capillary 11 [Date] endothelium, into Hb in the blood. Carbon dioxide diffuses into the alveoli from the blood, and is breathed out. 141. 3.1.4 Proteins - Correct answer 142. What is a protein made up of? - Correct answer Amino acids (monomers). 143. What is the general structure of an amino acid? - Correct answer (NH2) (R) - C - (H)(COOH) 144. How are two amino acids joined? - Correct answer Peptide bond formed by a condensation reaction (molecule of water eliminated). 145. What is the primary structure of a protein? - Correct answer Sequence of amino acids in the polypeptide chain. 146. What is the secondary structure of a protein? - Correct answer Hydrogen bonding forms between amino acids and so make it coil or fold into alpha helix or beta pleated sheet. 147. What is the tertiary structure of a protein? - Correct answer More bonds form (hydrogen and ionic bonds). Forms final 3D structure (for single chain proteins). 148. What is the quaternary structure of a protein? - Correct answer Made up of several different polypeptide chains held together by bonds. 149. What are the different functions of proteins? - Correct answer Structural proteins. Transport proteins. 150. Antibodies. Enzymes. 12 [Date] 151. Outline a method for the biuret test. - Correct answer Add a few drops of NaOH solution to the test sample. Add some copper(||) sulphate solution. If the protein is present the solution turns purple if there is no protein the solution will stay blue. 152. What is an enzyme? - Correct answer A biological catalyst. Catalyses metabolic reactions. 153. How do enzymes work? - Correct answer They lower the activation energy to speed up the rate of reaction. 154. Describe the 'lock and key' model. - Correct answer This is where the substrate fits into the enzyme in the same way the key fits into a lock. 155. Describe the 'induced fit' model. - Correct answer The substrate doesn't only have to be the right shape to fit the active site but also has to make the active site change shape in the right way. 156. Factors affecting enzyme activity: - Correct answer Temperature, pH, enzyme concentration, substrate concentration. 157. How does a competitive inhibitor work? - Correct answer A competitive inhibitor is of similar shape to the substrate, and is complementary to the active site. They attach to the active site before the substrate thus blocking it, but interact weakly so they dont stay permanently - compete for active site. 158. How does a non-competitive inhibitor work? - Correct answer They bind to another binding site other than the active site and alter the shape of the enzyme so the substrate can no longer bind to the active site. 15 [Date] 184. What is haemoglobin made up of? - Correct answer 4 polypeptide chains. 185. One haem group per chain, contains iron ion. 186. How many oxygen molecules can hemoglobin carry? - Correct answer 4 187. Haemoglobin has a ____ affinity for oxygen - Correct answer High. 188. What does haemoglobin form when it binds to oxygen? - Correct answer Oxyhaemoglobin. 189. What is the equation for the reaction between Hb and O2? - Correct answer Hb + 4O2 —> HbO8 190. What does 'partial pressure of oxygen' (pO2) mean? - Correct answer A measure of oxygen concentration. 191. Greater concentration -> higher pO2 192. What happens when there's a high pO2? - Correct answer Oxygen loads onto haemoglobin to form oxyhaemoglobin. 193. What happens when there's a low pO2? - Correct answer Oxyhaemoglobin unloads it's oxygen. 194. How is oxyhaemoglobin formed in the lungs? - Correct answer Oxygen enters blood capillaries at alveoli. Alveoli have high pO2 so oxygen loads onto haemoglobin to form oxyhaemoglobin. 16 [Date] 195. What happens to oxyhaemoglobin when cells respire? - Correct answer Cells use oxygen, lowers pO2. Red blood cells deliver oxyhaemoglobin to respiring tissues, unloads oxygen. 196. Evaluate the function of haemoglobin. - Correct answer In lungs, high pO2, so haemoglobin binds with oxygen to form oxyhaemoglobin (high affinity for oxygen in lungs). 197. At respiring cells (using up oxygen), lower pO2, so oxyhaemoglobin unloads oxygen at cells (low affinity for oxygen). 198. What does the Bohr effect cause? - Correct answer A shift in curve towards right. 199. What happens to pCO2 when cells are respiring? - Correct answer Increases. 200. How does haemoglobin differ at high altitudes? - Correct answer Haemoglobin has higher affinity for oxygen. 201. What is the general pattern of blood circulation in a mammal? - Correct answer Right side of heart: 202. Heart, pulmonary artery, lungs, pulmonary vein, heart. Back to left side. 203. Left side: 204. Heart, aorta, body (renal artery, renal vein) vena cava, heart. Back to right side. 205. Which two words describe the mammalian circulatory system? - Correct answer Closed, double. 206. What is the function of the coronary arteries? - Correct answer Supply oxygenated blood to the heart muscle. 17 [Date] 207. How does the structure of the heart relate to its function? - Correct answer AV valves, prevent backflow of blood from ventricles to atria. 208. SL valves, prevent backflow of blood from arteries to ventricles. 209. Left has thicker muscular wall, generates high blood pressure for blood to travel around body. 210. Right has thinner muscular wall, generates lower blood pressure, blood travels to lungs, high blood pressure would damage alveoli. 211. Describe the structure and function of arteries. - Correct answer Carry blood from heart to rest of body. 212. Thick muscle layer, to maintain high pressure & contracts to move blood along. 213. Elastic tissue layer, to stretch and recoil. 214. Smooth endothelium, to reduce friction. 215. Narrow lumen, to increase pressure. 216. Describe the structure and function of arterioles. - Correct answer Division of arteries to smaller vessels, direct blood flow to capillaries. 217. Thicker muscle layer than arteries. 218. Constrict to reduce blood flow (narrows lumen). 219. Dilate to increase blood flow (widens lumen). 220. Describe the structure and function of veins. - Correct answer Take deoxygenated blood back to heart under low pressure (except for pulmonary vein). 221. Wider lumen, little muscle/elastic tissue. 222. Contain valves to stop backflow of blood. 223. Contraction of skeletal muscles maintains blood flow in veins. 20 [Date] 248. What are some adaptations of the phloem? - Correct answer Sieve tube elements have no nucleus and few organelles. Companion cells carry out living functions for the sieve cells. 249. What is translocation? - Correct answer The movement of solutes to where they're needed in a plant. Moves solutes form source (high conc) to sink (low conc). 250. Explain the mass flow hypothesis. - Correct answer 1 translocation, at the source, high conc of solute, active transport of solutes from companion cells to sieve tube elements, wp lowered in sieve tube elements so water enters by osmosis from xylem/companion cells, pressure increases inside ste at source end. 251. 2 at the sink, low conc of solute, solutes removed to be used up, wp increases inside sieve tube so water leaves by osmosis, pressure decreases inside sieve tube elements. 252. 3 mass flow, pressure gradient from source to sink, solutes pushed from source to sink, solutes used/stored at sink. 253. 3.4.6 Biodiversity - Correct answer 254. Define biodiversity. - Correct answer The variety of living organisms in an area. 255. What is a habitat? - Correct answer Place where an organism lives. 256. What is a community? - Correct answer All the populations of different species in a habitat. 257. How is biodiversity reduced? - Correct answer Agricultural practices. 21 [Date] 258. Name some agricultural practices. - Correct answer Woodland clearance. 259. Hedgerow removal. 260. Pesticides. 261. Herbicides. 262. Monoculture.