BY4-Jan2013 Flashcards
Identify the chemical that acts as a photoreceptor in plants.
Photochrome.
The part of the plant that detects changes in day length.
Leaves.
Identify two forms in which nitrogen can be absorbed by plant roots.
Ammonium and nitrate.
Identify the stage in the nitrogen cycle that would be slowed by ploughing and drainage of soils.
Denitrification.
Identify free-living bacteria involved in the fixation of atmospheric nitrogen.
Azotobacter.
State the colour of the bacteria following the application of the counter stain.
Gram +ve = purple
Gram -ve = red
Explain the differences in the appearance of the two types of bacteria when stained with the frame staining technique.
Gram +ve - thick peptidoglycan cell wall. Retains crystal violet stain.
Gram -ve - lipopolysaccharide layer external to peptidoglycan cell wall. Does not retain crystal violet stain. Stains red with counter stain.
What’s the advantage of having the lipopolysaccharide layer to gram -ve bacteria?
Lipopolysaccharide layer protects against some antibiotics.
Suggest why this number in a viable count is likely to be an underestimate of the actual number of bacteria present.
Does not include dead/non-viable bacteria.
Cannot be sure each colony has grown from a single bacterium.
Explain what is meant by the term carrying capacity.
Maximum number of a population that can be sustained by a particular environment.
Describe two density dependant factors and one density independent factors that would affect population growth.
Density dependent:
Nutrient/food, oxygen level, disease, waste products, pH.
Density independent:
Temperature, size of particular environment.
What is interspecfic competition?
Competition for nutrients, space, resources between two different species.
Explain intraspecific competition.
Competition between individuals of the same species.
Explain how interspecfic competition would result in a population decrease.
Competition for the same food source.
Competition for the same niche.
More successful species outcompetes.
Explain the importance of ATP in cells.
ATP needed for active transport and protein synthesis.
Different types of energy can be transferred into a common form.
Only 1 molecule needed to transfer energy to chemical reactions.
Energy can be supplied in small amounts/less energy wasted.
Single bond needed to be broken to release energy.
Explain why ATP is sometime called the universal energy currency.
Used by all organisms.
To provide energy for nearly all biomechanical reactions.
Explain how opening and closing ion channels results in depolarisation of the axon membrane.
Sodium channels open.
Na+ flood into axon.
Inside axon becomes positively charged.
Explain how opening and closing ion channels results in repolarisation of the axon membrane.
Sodium channels close and potassium channels open.
Sudden influx of K+ ions flooding out of axon.
Inside axon becomes negatively charged.
Explain why an action potential was not generated by stimuli 1 to 4.
Threshold potential not reached.
Stimuli not enough to open Na+ ion channels.
‘All or nothing’
Explain what is meant by quaternary structure.
2 or more polypeptide chains.
Bonded together.
To form functional protein.
Name the substance you would expect to find around the outside, covering the axon.
Myelin.
Name the cell that produces the substance myelin.
Schwann cell.
Explain how the substance secreted by these cells and their arrangement along the neurone affect the speed of transmission of a nerve impulse.
Myelin inhibits movement of ions from axon/insulates axon.
Gaps between Schwann cells called nodes of Ranvier.
No myelin present at gaps.
Depolarisation only possible at modes of Ranvier.
Action potential jumps from node to node-saltatory conduction.
Nerve transmission faster.
Where does glycolysis occur?
Cytoplasm.
