Unit 2 flashcards

C R
Flashcards by , created over 4 years ago

According to OCR Biology Specification (used for summer 2015 exam)

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C R
Created by C R over 4 years ago
Cell Structure
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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