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| Question | Answer |
| Why does water have a high specific heat capacity and why is it useful? | Hydrogen bonds restrict movement so large amount of energy needed to increase temperature Provides stable temperature for lakes etc. |
| Why is water's high latent heat of evaporation property useful? | Evaporation uses lots of energy so takes away heat Cooling mechanism, e.g. sweating |
| Why is water a good solvent and why is this property useful? | Water's polarity means polar solutes can be dissolved as water surrounds the solute molecules and keep them apart Useful in metabolic reactions, as most of cytoplasm is made of water |
| Why is water's cohesive property useful? | It makes long, thin water columns strong, which is useful in xylem Creates surface tension so small organisms can 'walk on' water |
| Why does water become less dense as it freezes and why is this useful? | Hydrogen bonds keep water molecules apart in ice Ice floats and insulates the water below so organisms in lakes etc survive in winter |
| What are the functions of proteins? | - structural components - membrane carriers - enzymes - many hormones - antibodies |
| How many types of naturally occurring amino acids are there? | 20 |
| What are essential amino acids and how many are there? | Amino acids that cannot be made in the body There are 8-10 |
| What is the primary structure of a protein? | The sequence of amino acids that form the protein (held together by peptide bonds) |
| What is the secondary structure of a protein? | The coiling and pleating of parts of the polypeptide molecule into an alpha helix or beta pleated sheet (held together by hydrogen bonds) |
| What is the tertiary structure of a protein? | The overall 3D structure of the final polypeptide or protein molecule |
| What bonds hold together the tertiary structure of a protein? | - disulphide bridges (if 2 cysteine molecules) - ionic bonds (charged R groups) - hydrophobic/philic interactions (phobic in centre, pihlic on outside) - hydrogen bonds |
| Give examples of where the tertiary structure of a protein is important | - collagen shaped so strong - enzyme active sites must be complimentary - hormone to fit in receptor |
| Contrast the structures of haemoglobin and collagen | - globular protein // fibrous protein - transport protein // structural protein - soluble in water // insoluble - primary structure made of range of amino acids // ~35% is glycine - 4 polypeptide subunits, 2α and 2β chains // 3 polypeptide chain in helix, 3 helices form rope - haem prosthetic group // none |
| What are the functions of carbohydrates? | - energy source - energy store (e.g. starch) - structure (e.g. cellulose) |
| Are carbohydrates soluble? | Only simple monosaccharides and disaccharides |
| What are the disaccharide and polysaccharide of α glucose? | Disaccharide - maltose Polysaccharide - amylose |
| What is the difference between alpha and beta glucose at C1? | - OH of Alpha is Below - OH of Beta is Above |
| What are the similarities between starch and glycogen? | - energy store - polysaccharide of α-glucose - do not dissolve - free glucose molecules don't dissolve and lower WP - glucose in chains - can be broken easily as weak H bonds, for respiration |
| What are the differences between starch and glycogen? | - store in plants // store in animals - 20% long, straight chained amylose, 80% branched amylopectin // shorter 1,4 chains, more branches of 1,6-glycosidic bonds - not as compact // more compact - form grains // granules in liver and muscle cells |
| What is the structure of cellulose? | - long unbranched chains of β-glucose - every other glucose rotated 180° - 1,4-glycosidic bonds - H bonds between H (on C2 of one) and O (of C6 of glucose below) add strength to every other monomer - form microfibrils --> macrofibrils |
| What are the functions of lipids? | - energy source - energy store (in adipose cells) - cell membranes - insulation - protection - steroid hormones |
| Are lipids soluble? | They are insoluble in water but are soluble in organic solvents (e.g. alcohol) |
| Describe the structure of fatty acids | - carboxylic acid group on end - hydrocarbon chain - varies - single C=C --> mono-unsaturated - more C=C --> poly-unsaturated - C=C changed shape of chain --> pushes apart lipid molecules --> more fluid --> oil |
| What are the differences between a triglyceride and a phospholipid molecule? | Triglyceride - 1 glycerol and 3 fatty acids Phospholipid - 1 glycerol, 2 fatty acid chains, 1 phosphate head |
| Why do organisms in colder climates have more unsaturated fatty acids in their phospholipids? | To ensure that the membranes still remain fluid, even at low temperatures |
| What is the structure of a cholesterol molecule? | 4 carbon-based rings |
| What is the function of cholesterol and how do its properties help this? | - regulate fluidity and strength of membrane - sits between phospholipid tails - small, narrow and hydrophobic - steroid hormones - lipid nature so can pass straight through bilayer |
| What are the effects of excess cholesterol in a) the bile b) the blood | a) sticks together and forms gallstones b) causes atherosclerosis |
| What bonds are formed when building proteins, carbohydrates and lipids? | Proteins - peptide bonds Carbohydrates - glycosidic bonds Lipids - ester bonds |
| Describe how to test for reducing sugars | - Add Benedict's solution - Keep in water bath at 80°C for 3 mins - Blue --> orange-red |
| Describe how to test for non-reducing sugars | - If test for reducing sugars is negative - Boil with HCL - Cool - Neutralise with sodium hydrogencarbonate or sodium carbonate - Repeat reducing sugars test |
| Describe how to test for lipids | - Mix with ethanol to dissolve lipids - Pour into test tube with water - Cloudy white emulsion forms near top |
| Describe how to test for starch | - Add a few drops of iodine solution - Brown --> blue-black |
| Describe how to test for proteins | - Add biuret reagent (NaOH and CuSO4) - Blue --> lilac |
| What are the monomers of nucleic acids and what is there structure? | Nucleotides - made of 1 phosphate group, 1 pentose sugar molecule, one organic nitrogenous base (covalently bonded) |
| What is the sugar molecule in DNA? | Deoxyribose |
| What are purines? | Bases with double ring structure, e.g. adenine, guanine |
| What are pyrimidines? | Bases with a single ring structure, e.g. thymine, uracil, cytosine |
| What are the base pairs? | Adenine - Thymine Guanine - Cytosine |
| How many hydrogen bonds are between A-T? | 2 |
| How many hydrogen bonds are between G-C? | 3 |
| What is the structure of a DNA molecule? | - polynucleotide molecule - sugar-phosphate chain backbone - two antiparallel strands - twist to form double helix - A-T, G-C pairs |
| How does the structure of DNA relate to its function? | - bases form coded sequence to form proteins - information storage - long - large amount of information can be stored - base-pairing rules mean information can be replicated - H bonds allow easy unzipping - information can be copied - double helix - stability |
| How is DNA replicated? | - semi-conservative replication - double helix unwrapped - DNA helicase - H bonds broken to expose bases - free nucleotides in cytoplasm hydrogen bond to exposed bases if complementary with help from DNA polymerase - covalent bonds between phosphate of one nucleotide and sugar of next - exact replica of original |
| How does RNA differ from DNA? | - ribose sugar // deoxyribose sugar - uracil base // thymine base - single-stranded // double-stranded - 3 forms // 1 form |
| What are the three forms of RNA? | - messenger RNA - made as strand complimentary to DNA - ribosomal RNA - found in ribosomes - transfer RNA - carries amino acids to ribosomes |
| Why does DNA have to be transcribed into mRNA? | It is too large to move out of the nucleus to reach the ribosomes for protein synthesis |
| What are the steps for protein synthesis? | - DNA copied into mRNA - mRNA attaches to ribosome - tRNA brings amino acids complementary to sequence - amino acids join by peptide bonds --> specific primary structure |
| Define a gene | A sequence of DNA that codes for a polypeptide |
| What are enzymes? | - globular proteins - specific tertiary structure - biological catalysts for metabolic reactions - specific |
| What are extracellular enzymes? | - enzymes released from cells that make them - catalyse reactions outside cell - onto food in digestive system |
| What are intracellular enzymes? | - found in cytoplasm of cells or on cell membrane - catalyse reactions inside cell |
| How do enzymes affect activation energy? | They reduce activation energy |
| What is the lock-and-key hypothesis? | - enzyme has specific shaped active site - active site is complementary to shape of substrate - substrate fits into enzyme - reaction occurs |
| What is the current hypothesis for enzyme action? | - induced-fit hypothesis - as substrate collides with active side, enzyme changes shape slightly - active site fits more closely around substrate - substrate help because oppositely charged groups of substrate and active site near - forms enzyme-product complex - products different shape from substrate - products no longer fit into active site so move away |
| What happens, in general, to the rate of reaction when increasing the temperature? | - increases rate - increased temperature means increased collisions between enzyme and substrate - max rate of reaction at optimum temp |
| What happens when the enzyme is heated to a temperature above its optimum temperature? | - heat causes molecules to vibrate - vibrations break weaker bonds, e.g. hydrogen bonds and ionic bonds - tertiary structure held by the bonds held less in shape - rate decreases - tertiary structure may unravel and enzymes stops completely - irreversible denaturation |
| How does increasing the substrate concentration affect enzyme activity? | - as concentration increases collisions between enzymes and substrate molecules occur more often - more enzyme-substrate complexes form so more product and rate increases - reaction rate reaches maximum - all active sites occupied - no further increase - enzyme concentration is limiting factor |
| How does pH affect enzyme activity? | - pH is measure of H+ concentration - hydrogen and ionic bonds caused by attraction between oppositely charged groups on amino acids - H+ ions interfere with hydrogen and ionic bonds that hold tertiary structure - H+ repelled by positively charged ions, attracted to negatively charged groups - changes active site shape and so rate |
| How does increasing the enzyme concentration? | - as enzyme concentration increases more active sites available - more enzyme-substrate complexes, so more products so rate increases - rate reaches maximum - all substrate molecule occupying enzyme active sites - substrate concentration is limiting factor |
| What are competitive inhibitors? | - similar shape to substrate molecules - can occupy active sites to form enzyme-inhibitor complexes - does not lead to formation of products - substrate molecule cannot enter - reduces number of enzyme-substrate complexes so reaction rate slows |
| What are non-competitive inhibitors? | - attach to enzyme molecule at allosteric site, away from active site - distorts tertiary structure of enzyme - changes shape of active site - substrate no longer fits into active site - enzyme-substrate complexes cannot form - reaction rate decreases - changing substrate concentration has no effect - many are irreversible - effectively denatured |
| Describe the action of a named poison | POTASSIUM CYANIDE - non-competitive inhibitor of cytochrome oxidase found in mitochondria - inhibits cell respiration - reduces use of oxygen - ATP not produced - organism can only respire anaerobically - leads to build up of lactic acid in blood |
| How are enzymes used in ethylene glycol poisoning? | - ethylene glycol found in antifreeze - if ingested broken down in liver by alcohol dehydrogenase enzyme into toxic oxalic acid - ethanol acts as competitive inhibitor - reduces rate of oxalic acid production - ethylene glycol can be excreted harmlessly |
| How are enzymes inhibitors used to treat HIV? | - protease inhibitors - prevent viruses from replicating by inhibiting the activity of protease - new virus coats cannot be built - competitive inhibitors |
| How are inhibitors used to kill microorganisms such as bacteria? | - antibiotics kill or inhibit growth of microorganism - penicillin inhibits a bacterial enzyme which forms cross-links in bacterial cell wall - cell walls not formed - reproduction halted |
| What is the turnover number of an enzyme? | The number of reactions an enzyme molecule can catalyse in one second |
| What are inborn errors of metabolism? | Diseases caused by the lack of a functioning specific enzyme in a metabolic sequence |
| How are the metabolic sequences controlled? | - product of one enzyme-controlled reaction is substrate for next in sequence - acts as non-competitive inhibitor - attaches away from active site, changes active site shape - reactions - metabolic pathways |
| Define a balanced diet | A diet that contains all the nutrients required for health in the appropriate proportions |
| Why is good nutrition required? | - provide better health - stronger immune system - stronger - more productive |
| What are the components of a balanced diet? | - Carbohydrates - energy source - Proteins - growth and repair of muscle - Fats - energy source, cell membranes, waterproofing, absorption of fat-soluble vitamins - Vitamins - chemical processes Minerals - inorganic elements - Water - transporting substances - Fibre - healthy functioning of digestive system |
| What is malnutrition and what is an example? | - caused by an unbalanced diet - obesity - consuming too much energy - excess fat stored in adipose tissues - impairs health |
| What diseases can be caused by obesity? | - cancer - cardiovascular diseases - type 2 diabetes - gallstones - osteoarthritis - hypertension (high BP) |
| What factors in the diet can lead to CHD? | - excess salt - decreases WP --> more water held in blood --> BP increases --> hypertension --> damages lining --> atheromas - fats - saturated is harmful, poly/monounsaturated fats beneficial - cholesterol - LDL harmful |
| What are lipoproteins made of? | - lipids - proteins - cholesterol |
| What are high-density lipoproteins (HDLs)? | - unsat fats, cholesterol and protein - cholesterol from body tissues to liver - liver cells have receptor sites allowing HDLs to bind to cell surface membranes - to make bile or broken down - reduce blood cholesterol levels - unsaturated fats seem to increase activity of LDL receptors so decrease LDL concentration in blood |
| What are low-density lipoproteins (LDLs)? | - sat fats, cholesterol and proteins - carry cholesterol from liver to tissue - tissue cells have receptors sites for LDLs to bind - high blood conc of LDLs causes deposition - sat fats thought to decrease activity of LDL receptors so as blood LDL conc increases less removed from blood |
| How can the diet be made healthier, in relation to cholesterol? | - less saturated animal fats - LDLs - more unsaturated fats - HDLs - more poly/monounsaturated - less LDLs - low-fat diet - reduces overall lipoproteins |
| What is selective breeding? | Where humans select the individual organisms that are allowed to breed according to chosen characteristics |
| What is the process of selective breeding? | - isolation - selecting pair of plants/animals displaying desired characteristics and allow to reproduce - artificial selection - offspring with best combination of characteristics selected - inbreeding - selected allowed to reproduce, over several generations - new marker-assisted selection - section of DNA marked to recognise desired characteristic |
| What traits are selected for plants? | - high yield - disease resistance - pest resistance |
| What traits are selected for animals? | - faster rate of growth - increased productivity - disease resistance |
| How can chemicals boost food production? | - fertilisers - replace minerals in soil, such as nitrate, potassium, to increase rate of growth and size of crop - pesticides - kills pest that reduce yield - fungicide - kills fungi that reduce yield - antibiotics - kills bacteria, reduce spread of disease as could reduce growth |
| What are some examples of the use of microorganisms to make food? | - yoghurt - Lactobacillus bacteria - cheese - Lactobacillus bacteria, Penicillium fungus - bread - yeast - alcohol - yeast - Quorn - fungus |
| What methods are used to prevent food spoilage by microorganisms? | - Salting/ adding sugar - dehydrates any microorganisms as water leaves by osmosis - Pickling - uses an acid pH to kill them by denaturing their enzymes - Freezing - do not kill, retard enzyme activity so reproduction is slow - Cooking/ pasteurising - heat denatures enzymes and other proteins - Irradiation - ionising radiation kills them by disrupting DNA structure - Vacuum wrapping - air excluded so microbes cannot respire aerobically |
| What are the advantages of using microorganisms in food production? | - faster production of protein - production can be increased or decreased for demand - no animal welfare issues - source of protein for vegetarians - protein contains no animal fat or cholesterol |
| What are the disadvantages of using microorganisms in food production? | - people may not want to eat fungal protein or food grown on waste - microorganisms grown in fermenters and need to be isolated from material on which they grow - protein needs to be purified to ensure it is uncontaminated - conditions for useful microorganisms to grow also ideal for pathogenic organisms - does not have taste or texture of traditional protein sources |
| Define health | A state of mental, physical and social well-being, not just the absence of disease |
| Define disease | A departure from good health caused by a malfunction of the mind or body |
| Define a pathogen | An organism that causes disease, e.g. bacteria or fungi |
| What are the 4 types of pathogens? | - bacteria, e.g. cholera, TB - fungi - athlete's foot, ringworm - virus - influenza, HIV/AIDS - protocista - amoeboid, malaria |
| How do bacteria cause disease? | - damaging cells - releasing toxic waste products |
| How do fungi cause disease? | - sends out reproductive hyphae which grow to the surface to release spores |
| How do viruses causes disease? | - invade cells - take over genetic machinery - cause cell to manufacture copies of virus - host cell bursts - new viruses released |
| How do protoctista cause disease? | - enter host cell - feed on the contents as they grow |
| Define parasites | Organisms that live in or on another living thing, causing harm to its host, e.g. tapeworm, headlice |
| What are some common forms of transmission of disease? | - means of a vector - physical contact - droplet infection |
| By which method of transmission is malaria spread by? | - vector transmission - Plasmodium - protozoa - female Anopheles mosquito |
| What is the cycle of malaria parasites from an infected host? | - host with malaria - mosquito sucks Plasmodium gametes into its stomach - gametes fuse and zygotes develop in its stomach - infective stages form and move to mosquito's salivary glands - when mosquito bites uninfected person it injects some saliva as an anticoagulant - saliva contains infective stages - infective stages enter liver in human host where they multiply - move to blood and enter red blood cells, where gametes are produced |
| Apart from the female Anopheles mosquito, how else is the malarial parasite spread? | - unscreened blood transfusions - unsterilised needles - across placenta into unborn child |
| What is the global impact of malaria? | - kills around 3 million people a year - affects around 300 million worldwide - limited to tropical region where mosquitoes can survive - global warming - may soon be able to survive further north |
| What do HIV and AIDS stand for? | Human immunodeficiency virus and acquired immune deficiency syndrome |
| What are the steps of HIV? | - virus enters body and may remain inactive (HIV-positive) - when active attacks and destroys T helper cells - body prone to contracting opportunistic infections |
| How is HIV transmitted? | - exchange of bodily fluid - unprotected sexual intercourse - unscreened blood transfusions - across placenta or during childbirth - mother to child through breast feeding |
| What is the global impact of HIV/AIDS? | - 2005 - 45 million people infected - over half in sub-Saharan Africa - 2005 - 30 million died from HIV/AIDS-related diseases - 5 million people newly infected each year |
| What is tuberculosis caused by and how is it transmitted? | - Mycobacterium tuberculosis and M. bovis bacterium - transmitted by droplet infection - coughs, sneezes etc over long period, e.g. overcrowding, poor ventilation - milk or meat of cattle |
| What is the global impact of TB? | - 1% world newly infected every year and 10-15% go on to develop TB - 2005 - 8.8 million new cases - 2005 - 1.6 million died - up to 30% world may be infected with Mycobacterium |
| What are primary defences and what are some examples? | - defences that attempt to prevent the pathogen from entering the body - skin - physical barrier - keratinised layer of dead cells - mucous membranes - goblet cells and cilia - tear fluid - antibodies |
| What are the two types of phagocytes? | - neutrophils - made in bone marrow, multilobed nucleus, short-lived - macrophages - larger cells, made in bone marrow, travel in blood as monocytes, develop in lymph nodes |
| Describe the process of phagocytosis | - antigens on pathogen recognised as foreign - antibodies attach to antigens - receptors on phagocyte (membrane-bound proteins) bind to antibodies attached to pathogen - phagocyte engulfs pathogen by folding membrane inwards - pathogen trapped inside vacuole called phagosome - lysosomes fuse with phagosome and release lysins enzymes into it - end products absorbed into cytoplasm |
| What are antigens? | Molecules that stimulate an immune response; usually a protein or glycoprotein on plasma membrane |
| What are antibodies? | Protein molecules that can identify and neutralise antigens |
| What are antibodies produced by? | B lymphocytes - plasma cells |
| What is another name for antibodies? | Immunoglobulins |
| What is the structure of an antibody? | - 4 polypeptide chains - held together by disulfide bridges - constant region - antibodies can attach to phagocytic cells - variable region - specific shape, complimentary to shape of antigen - hinge regions - degree of flexibility, allow branches to move further so can attach to more than one antigen |
| How do antibodies work? | - Neutralisation - blocks binding sites of pathogen to host cells - Agglutination - large antibody with many Y-shaped molecules attached, many variable region for binding to many pathogens, group too large to enter host cell |
| Define immune response | The specific response to a pathogen, which involves that action of lymphocytes and the production of antibodies |
| How does the secondary response compare to the primary response? | - faster and more antibodies produced - memory cells remain in blood after primary infection |
| Where are B lymphocytes made? | In the bone marrow |
| Where are T lymphocytes made and where do they mature? | Made in the bone marrow Mature in thymus gland |
| What can T lymphocytes differentiate into? | - T helper - release cytokines stimulating B cells to develop, stimulate phagocytosis - T killer - attack and kill infected body cells - T memory - remain in blood |
| What can B cells differentiate into? | - Effector/plasma cells - manufacture and release antibodies - B memory - remain and act as immunological memory |
| What are the steps in a specific immune response to a pathogen? | - pathogen engulfed and partially digested by macrophages - macrophage becomes antigen-presenting cell - clonal selection of specific T- and B-lymphocytes - clonal expansion of specific T cells - T cells differentiate - T-helper cells release cytokines which activate further macrophage activity and activate B cells - T-memory remain in body - T-killer - find infected body cells, attach and secrete hydrogen peroxide to kill - clonal expansion of specific B cells - some become plasma cells that manufacture and release antibodies - B-memory cells - immunological memory in body |
| What is a vaccination? | The deliberate exposure to antigenic material, which activates the immune system to make an immune response and provide immunity |
| What are vaccinations made of? | - attenuated (weak) pathogen - dead version of pathogen - free antigens - toxins from pathogen |
| What is herd immunity? | - vaccinating most people in a community - disease becomes rare - even those not vaccinated unlikely to get as no one to get disease from |
| What is natural immunity? | Immunity gained in the normal course of living processes |
| What is artificial immunity? | Immunity gained by deliberate exposure to antibodies or antigens |
| What is active immunity? | When the immune system makes its own antibodies |
| What is passive immunity? | When the antibodies are made by a different organism |
| Compare the advantages and disadvantages of active and passive immunity | LT protection // ST protection takes time // immediate memory cells formed// no memory cells |
| Give an example of natural active immunity? | antibodies formed due to infection |
| Give an example of natural passive immunity | antibodies provided via placenta or breast milk |
| Give an example of artificial active immunity | antibodies made as result of vaccination |
| Give an example of artificial passive immunity | antibodies made by another individual, e.g. tetanus vaccine |
| How does smoking affect the cardiovascular system? | - atherosclerosis - coronary heart disease - stroke |
| What is atherosclerosis? | The deposition of fatty substances in the walls of the arteries |
| What substances are found in atheromas? | - fibres - dead blood cells - platelets - cholesterol |
| How does smoking cause atherosclerosis? | - CO damages endothelium of arteries - phagocytes encourage growth of smooth muscle and fatty substances deposition - nicotine increases blood pressure - damage - atheromas form plaque, stick into lumen, reduces lumen size, reduces blood flow |
| What is CHD? | A disease of the heart caused by the malfunction of the coronary arteries |
| How does smoking cause CHD? | - nicotine makes platelets sticky - increase chances of thrombus forming - CO bind irreversibly with haemoglobin - reduces amount of oxygen taken to muscles such as heart |
| What is a stroke? | The death of part of the brain due to a lack of blood flow to that part of the brain and subsequent oxygen deficiency |
| How does smoking cause stroke? | - nicotine makes platelets sticky - increases risk of blood clots - thrombus blocks small artery leading to brain - CO binds with haemoglobin - reduces amount of oxygen - hemorrhage of artery leading to brain |
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