44735
| Pregunta | Respuesta |
| Explain the reason for the lag phase during population growth | This is a period of preperation for growth and enzymes are produced by protein synthesis |
| What is meant by the tem 'carrying capacity'? | The maximum population size that can be supported by the available resources |
| Distinguish between density dependent and density independent factors | Density dependent = the effect depends on the population size Density independant = effect is the same no matter what the population size |
| List three density dependant factors that limit the population growth | Lack of food Toxic waste Predation Parasitism |
| List the properties of an organism used for biological control of a pest | Species highly specific Long term No environmental contamination |
| A parasitic wasp may be used to control whitefly populations in a glasshouse. State two reasons why it would be inappropriate to use both a chemical and biological control method at the same time | Chemicals are non specific and would kill the wasps Waste of money |
| Explain why plants require nitrate | Nitrate is combined with the products of phpotosynthesis to form amino acids which are converted to proteions which are required for growth |
| Give the term for the process of converting ammonium ions to nitrate ions | Nitrification |
| What stage in the nitrogen cycle is this: Dead plants and animals are decomposed into ammonium ions | Putrefaction |
| What is nitrogen fixation? | Ammonia -> nitrites Nitrites -> nitrates |
| Give an example of free living bacteria | Azotobacter |
| What is Rhizobium? | A nitrogen fixing bacteria |
| Which releases more energy, fat or carbohydrate? | Fat |
| What is the difference between an absorption spectrum and action spectrum? | Action spectrum = rate of photosynthesis Absorption spectrum = how much light a particular pigment absorbs at each wavelength |
| Which pigment is found at the reaction centre? | Chlorophyll a |
| What is the source of replacement electrons for photosystem 2? | photolysis of water |
| State two differences between cyclic and non - cyclic photophosphorylation | Cyclic only involves PS1 and the source of electrons is PS1 Non - cyclic involves both photosystems and the souce of electrons is from water INCLUDE BOTH SIDES |
| Why is it essential to regenerate ribulose bisphosphate? | So that it can accept additional C02, otherwise the cycle wouldn't continue |
| Name the three shapes of bacteria | Bacillus = rod shaped Cocci = spherical Spirillium = corkscrew shaped |
| What additional chemical is present in the cell wall of gram negative bacteria? | Lipopolysaccharide |
| What colour would gram negative bacteria stain in the gram stain test? | Red Positive = Purple (P&P) |
| Apart from oxygen, list three other requirements for microbial growth | Suitable temperature Suitable pH Carbon source/glucose Nitrogen source |
| Define a pathogen | a disease causing microbe |
| What assumption is made when counting bacterial colonies? | Each colony developed from a single bacterium |
| By what process does one cell give rise to a colony? | Asexual reproduction |
| State three advantages of using industrial fermenters | - More efficient due to high yield -Carried out at lower temperatures -Rapid rate of growth |
| Why is ammonia included as one of the nutrients in fermentation? | Ammonia contains nitrogen which is needed to synthesise proteins |
| Why is the cooling jacket essential to the process of fermentation? | To prevent overheating which would denature the enzymes |
| Define a secondary metabolite | A chemical which is not necessary for the growth of the fungus and is produced after the exponential phase of growth is completed, when glucose is depleted |
| Name a cell type with a large number of mitochondria | Muscle, liver |
| Where do the following occur: -Glycolysis -Krebs cycle | Cytoplasm Matrix |
| Explain the role of oxygen in the electron transport chain | Oxygen is the final electron acceptor. Without it electrons would accumulate and the reaction would stop |
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