Biol4 AQA Flashcards

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Nitrogenase catalyses the reduction of nitrogen fixation. The reaction requires 16 molecules of ATP for each molecule of nitrogen that is reduced. Nitrogen gas is the usual substrate for this enzyme. Name the product.
Ammonium.
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Nitrogenase also catalyses reactions involving other substances. Explain what this suggests about the shape of the molecules of these other substances.
The other substances have the same tertiary structure and the active site is complementary to form an enzyme substrate complex.
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Azotobacter is a nitrogen-fixing bacterium. It produces the enzyme nitrogenase. The enzyme only works in the absense of oxygen. Azotobacter has a very high rate of aerobic resp compared with bacteria that don't fix nitrogen. Two advantages of this?
More enzyme can be produced. Reduction of nitrogen to ammonia which can then be used to manufacture amino acids.
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If scientists could transfer the gene that codes for nitrogenase to cereal plants, these cereal plants would be able to fix nitrogen. Explain why they would grow more slowly.
ATP would be being used to form ammonia, so less ATP would be available for growth.
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How do you calculate an estimated population size?
(total no. of 1st sample X total no. of 2nd sample) / no. of marked individuals recaptured
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What does the Hardy-Weinberg principle predict?
The frequencies of the alleles of a particular gene in a population. The proportion of alleles remains the same from generation to generation given five conditions are met.
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What are the five conditions of Hardy-Weinberg?
No mutation, large population, so selection, no migration and population is genetically isolated.
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What are the Hardy-Weinberg equations?
p^2 + 2pq + q^2 = 1 and p + q = 1
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How is net production calculated?
Gross production - respiratory losses
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How else can net production be calculated?
Ingested food - egested - respired / ingested food - ( egested + respired )
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What is nitrification?
1. the oxidation of ammonium ions to nitrite ions. 2. the oxidation of nitrite ions to nitrate ions.
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What are nitrifying bacteria?
Bacteria that obtain their energy from chemical reactions. E.g. oxidation reactions releasing energy or ammonium and nitrite ions. These processes require oxygen.
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Describe the part played by the inner membrane of a mitochondrion in producing ATP.
Electrons pass down the electron transfer chain, which provides energy to take protons into space between membranes, protons then pass back through the membrane. Energy is used to combine ADP and phosphate, to produce ATP.
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What effect do humans have on animals living on the seashore?
Human activity means there are less habitats, as species of seaweed are disturbed. There are fewer niches, and less large animals due to the disturbance. Any small animals tend to be young.
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The Conc of CO2 in the air at different heights above ground in a forest changes over a period of 24hrs. Explain why.
High Conc of CO2 at night. No photosynthesis at night. Plants respire at night. Higher levels have less CO2. Lower levels have more CO2 due to less light for photosynthesis.
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Light-independent reaction - carbon dioxide > triose phosphate. How?
CO2 combines with 5-C RuBP using an enzyme. CO2 & RuBP produce 2 molecules of 3-C GP. ATP & reduced NADP are used to reduce the GP to TP.
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Microorganisms make the carbon in polymers in a dead worm available to cells in a leaf. Describe how.
Microorganisms are saprophytes, which secrete enzymes for digestion. Products of digestion are absorbed and CO2 is taken into leaves through the stomata.
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Equation for a population that stays the same size.
Birth rate + immigration rate = death rate + emigration rate
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Equation for an increasing population size.
Birth rate + immigration rate > death rate + emigration rate
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What is meant by a recessive allele?
An allele which is not expressed in a heterozygous state.
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What is meant by codominant alleles?
Both alleles are equally expressed and dominant.
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Succession occurs in natural ecosystems. Describe and explain how succession occurs.
Colonisation of pioneer species, change in environment, this enables other species to colonise, change in diversity, stability increases and climax community.
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Manages ecosystems such as wheat fields are prone to pest infections. Describe the advantages and disadvantages of using biological control pests.
The control can be specific, only needs to be applied once, and the pests do not develop resistance. However pest isn't removed completely, and it may become a pest itself.
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Changes in ecosystems can lead to speciation. Describe how.
Change in environment, variation due to mutation, reproductive success, allele frequency, geographical isolation and separate gene pools.
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Other cards in this set

Card 2

Front

Nitrogenase also catalyses reactions involving other substances. Explain what this suggests about the shape of the molecules of these other substances.

Back

The other substances have the same tertiary structure and the active site is complementary to form an enzyme substrate complex.

Card 3

Front

Azotobacter is a nitrogen-fixing bacterium. It produces the enzyme nitrogenase. The enzyme only works in the absense of oxygen. Azotobacter has a very high rate of aerobic resp compared with bacteria that don't fix nitrogen. Two advantages of this?

Back

Preview of the front of card 3

Card 4

Front

If scientists could transfer the gene that codes for nitrogenase to cereal plants, these cereal plants would be able to fix nitrogen. Explain why they would grow more slowly.

Back

Preview of the front of card 4

Card 5

Front

How do you calculate an estimated population size?

Back

Preview of the front of card 5
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