Biology OCR, B4

What do the basic processes of life carried out by all living things depend on?
chemical reactions within cells that require energy released by respiration
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What is photosynthesis?
a series of chemical reactions that use energy from sunlight to build large food molecules in plant cells and some microorganisms
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What is respiration?
a series of chemical reactions that release energy by breaking down large food molecules in all living cells
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What are enzymes?
proteins that speed up chemical reactions
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What do cells make enzymes according to?
the instructions carried in the genes
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What is the lock and key model?
molecules have to be the correct shape to fit into the active site of the enzyme and for the reaction to take place
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What do enzymes need to work at their optimum?
a specific, constant temperature. If the temperature is too high the enzymes permanently stop working (denature)
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What is enzyme activity at different temperatures a balance between?
increased rates of reaction as temperature increases and changes to the active site at higher temperatures, including denaturing
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Apart from temperature, what else does an enzyme need to work at its optimum?
a specific pH
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What affect does pH have on enzyme activity?
if pH levels are not right, the shape of the active site is irreversibly changed. Therefore the molecule can't fit and the reaction can't take place
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What is the word equation for photosynthesis?
o carbon dioxide + water ==light energy==> glucose + oxygen
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What is the symbol equation for photosynthesis?
o 6CO2 + 6H2O ==light energy==> C6H12O6 + 6O2
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What are the three main stages of photosynthesis?
light energy is absorbed by the green chemical chlorophyll. Energy used to bring about the reaction between carbon dioxide and water to produce glucose. Oxygen produced as a waste product
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What may glucose be used for?
may be converted into chemicals needed for growth of plant cells (e.g. cellulose, protein and chlorophyll). Converted into starch for storage. Used in respiration to release energy
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What are minerals taken up by plant roots used for?
to make some chemicals needed by cells, including nitrogen from nitrates to make proteins
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What is diffusion?
the passive overall movement of molecules from a region of their higher concentration to a region of their lower concentration
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What is an example of diffusion in plants?
during photosynthesis, the movement of oxygen and carbon dioxide in and out of leaves is an example of diffusion
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What is osmosis?
the overall movement of water from a dilute to a more concentrated solution through a partially permeable membrane
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How does the movement of water into plant roots occur?
by osmosis
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What is active transport?
the overall movement of chemicals across a cell membrane, against the concentration gradient, requiring energy from respiration
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When is active transport used?
in the absorption of nitrates by plant roots
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What factors may limit the rate of photosynthesis?
temperature, carbon dioxide levels and light intensity
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What techniques are used to investigate the effect of light on plants?
using a light meter to measure light levels, using an identification key to identify plants and using a quadrat to get a random sample
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How do you take a transect?
a transect is a random section of an area (e.g. a line) to represent the entire area. A quadrat is placed at even intervals along the transect line to randomly sample an area
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What do all living organisms need for some chemical reactions in cells, including chemical reactions involved involved in: movement, synthesis of large molecules and active transport
the need energy released by respiration
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What does the synthesis of large molecules include?
synthesis of polymers required by plant cells such as starch and cellulose from glucose in plant cells. Synthesis of amino acids from glucose and nitrates, and then proteins from amino acids in plant, animal and microbial cells
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Where does aerobic respiration take place and what does it require?
takes place in animal and plant cells and some microorganisms. Requires oxygen
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What is the word equation of aerobic respiration?
o glucose + oxygen ==> carbon dioxide + water (+ energy released)
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What is the symbol equation for aerobic respiration?
o C6H12O6 + 6O2 ==> 6CO2 + 6H2O
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When does anaerobic respiration take place?
in conditions of low oxygen or absence of oxygen in animal, plant and some microbial cells
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What are example of conditions for anaerobic respiration?
plant roots in waterlogged soil, bacteria in puncture wounds and human cells during vigorous exercise
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What is the word equation for anaerobic respiration in animal cells and some bacteria?
o glucose ==> lactic acid (+ energy released)
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What is the word equation for anaerobic respiration in plant cells and some microorganisms including yeast?
o glucose ==> ethanol + carbon dioxide (+ energy released)
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Why is aerobic respiration more effective than anaerobic respiration?
aerobic respiration releases more energy per glucose molecule than anaerobic respiration
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What are examples of the applications of anaerobic respiration of microorganisms?
can be used in sewage farms to break down sewage to release methane and produce biogas. In yeast used to breaking to make the dough rise and in alcohol production during fermentation
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Other cards in this set

Card 2


What is photosynthesis?


a series of chemical reactions that use energy from sunlight to build large food molecules in plant cells and some microorganisms

Card 3


What is respiration?


Preview of the front of card 3

Card 4


What are enzymes?


Preview of the front of card 4

Card 5


What do cells make enzymes according to?


Preview of the front of card 5
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