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| Frage | Antworten |
| Enzyme Action | > activity depends on flexible/dynamic shape of enzymes > active site on enzyme has an affinity for substrate > there is an induced fit > active site orientates reactants > activation energy is lowered > products have a lower affinity for the active site > substrate and product concentrations affect the rate of reaction |
| Enzyme Inhibition | > competitive inhibition > inhibitor has similar shape to substrate and fits active site > non competitive inhibition > active site is changed so substrate cannot bind |
| Natural Selection | > organisms show genomic variation > natural selection is non random > causes the increase in frequency of certain genetic sequences >these sequences increase chance of survival > individuals with favourable genes survive to reproduce > survivors pass on genes to offspring > disadvantageous genes reduced in frequency/removed from population > mentions of stabilising/disruptive/directional selection > happens over a long time/many generations |
| Genetic Drift | > random increases and decreases in frequency of alleles in a population > particularly in small populations > can come from neutral mutations (free from selection pressure) > can come from founder effect > founders of new populations have genetic sequences not representative of original population |
| Citric Acid Cycle | > if oxygen is available, pyruvate progresses to citric acid cycle > pyruvate is broken down to an acetyl group > acetyl binds to coenzyme A > acetyl coenzyme A + oxaloacetate = citrate > cycle is controlled by enzymes > ATP is generated > CO2 is released > oxaloacetate regenerated > NAD (NADH) and FAD (FADH2) transport H+ ions to the next stage |
| Glycolysis | > glucose is broken down to pyruvate > there is an energy investment phase > 2ATP is used to phosphorylate intermediates > ATP is produced in energy payoff phase > Net gain of 2ATP |
| Differentiation of Stem Cells | > stem cells are unspecialised > they divide > they differentiate into specialised cell types > differentiated cells cannot change > embryonic SCs can become any kind of cell > tissue SCs can only become a limited number of cells > after differentiation a cell can only express certain genes.. > .. only genes that produce proteins characteristic of that cell type |
| Research into stem cells and their Therapeutic Value | > SC research provides information on cell processes > eg. cell division, differentiation > therapeutic use - to repair/replace damaged tissue cells > the research must be regulated |
| Measuring Biodiversity | > you can measure genetic diversity, species diversity and ecosystem diversity > genetic diversity - the number and frequency of alleles/sequences in a population > species diversity is species richness and relative abundance > species richness is the number of different species > relative abundance is the proportion of each species > ecosystem diversity is the number of different/distinct ecosystems |
| Threats to biodiversity | > overexplotation > eg. overfishing/ overhunting/ deforestation > bottleneck effect is loss of genetic variation in small populations/few surviving individuals > removal of keystone species decreases biodiversity > habitat fragments have low species richness/diversity > in habitat fragments edge species outcompete interior species > invasive species can outcompete native / keystone species > invasive species may be free of predators/pathogens/disease (which naturally limit their populations) > human activities cause climate change / global warming |
| Food Security & Population | > food security is the ability of humans to access food of sufficient quality and quantity > increasing population increases the demand/need for food > production/supply is sustainable > does not degrade natural resources/environment on which agriculture depends |
| Factors Affecting Food Production | > depends on photosynthesis > limited by area of land > limiting factors include light intensity, temperature, CO2 concentration > high yield cultivars > pests damage crops/ weeds compete with crops/ diseases kill crops > pesticides/ fungicides/ herbicides can control weeds, pests and disease > increased irrigation/ water availability/ fertilizers increases food production > livestock produce less food per unit area than crops due to energy loss at each trophic level > livestock can be grazed/ raised/ kept on habitats/ land not suitable for crops |
| Phylogenetics | > the use of DNA / genetic sequences > to study the evolutionary relatedness of living organisms > sequence divergence gives estimates of time since lineages diverged > eg divergence of three main domains > used with fossil evidence to determine the main sequence of events in evolution > divergence since a common ancestor > shows genome conservation across lineages |
| Personalised Medicine | > personal genomics is analysis of an individual human genome > medicine suitable for the individual can be worked out > though knowledge of genetic component of susceptibility/likelihood of treatment success |
| Structure of DNA | > double strand of nucleotides / double helix > deoxyribose sugar, phosphate and base > sugar phosphate backbone > complementary base pair A-T of C-G > H bonds between bases > antiparallel structure with deoxyribose and phosphate at 3´ and 5´ends > associated with proteins |
| Replication of DNA | > DNA unwinds into two strands > primer needed to start replication > DNA polymerase adds nucleotides to 3´(deoxyribose) end of strand > DNA polymerase adds nucleotides in one direction > one strand replicated continuously, the other in fragments > fragments joined by ligase |
| Speciation - isolation and mutation | > isolating barriers prevent gene flow > geographical isolation leads to allopatric speciation > behavioural & ecological isolation leads to sympatric speciation > different mutations occur on each side of isolation barrier > some mutations may be favourable |
| Speciation - selection | > description or natural selection > description of sexual selection > disruptive / directional / stabilising > after many generations > new species form > if populations can no longer interbreed to produce fertile young then different species |
| Occurrence of mutant alleles and effects of mutagenic agents | > occurrence is random and at low frequency > mutagenic agents increase rate of mutation > they can be chemicals - mustard gas, benzene > radiation / UV light |
| genetic mutations and their effect on protein structure | > include inversion / substitution / deletion / insertion (any 2) > include other 2 > description of one named mutation in terms of nucleotides > description of another > inversion and substitution are point mutations / only change one codon > deletion and insertion are frame-shift mutations > point mutations change one amino acid > frame shift change all amino acids after the mutation > frame shift cause major changes to protein structure |
| structure of chloroplasts | > double membrane > stroma is liquid-filled > grana are membranes containing pigments |
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