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A Level Biology Paper 2 > Cycles > Flashcards

Cycles Flashcards

1
Q

Name some important cycles in biology

A 
Cell cycle
Calvin cycle
Menstrual cycle
Water cycle
Krebs cycle
Nitrogen cycle
Phosphate cycle
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2
Q

Where is nitrogen found

A 
Amino acids
Protein
Nucleic acid
Bases
DNA
RNA
ATP
NAD
NADP
Chlorophyll
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3
Q

What is a carbon sink

A

Takes up and stores carbon for a long time

Peat, coal, limestone, fossil fuels, shells

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4
Q

What is global warming

A

Increase in temperature of Earths surface
Due to increase in greenhouse gases (e.g. CO2)
That trap/reflect heat or infrared waves in the atmosphere
Causing flooding, melting ice caps and hence climate change

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5
Q

What are saprobionts

A

Decomposers that secrete extra-cellular enzymes to hydrolyse organic materials (DNA, RNA, protein)
So they can be absorbed across their cell membranes
Producing ammonium ions

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6
Q

Describe the role of microorganisms in the nitrogen cycle

A

Sabrobionts: Secrete extra-cellular enzymes that hydrolyse organic materials (DNA, protein) into ammonia

Nitrogen Fixing Bacteria: Involved in the reduction of nitrogen gas into ammonia

Denitrifying Bacteria: Involved in converting nitrates into nitrogen gas

Nitrifying Bacteria: Involved in the oxidation of ammonia to nitrites and nitrites to nitrates

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7
Q

Explain nitrification

A

Ammonia oxidised into nitrites then nitrates by nitrifying bacteria
So that the nitrates can be assimilated by active transport through root hair cells
To synthesise DNA, RNA for growth and reproduction

NH3/NH4+ –> NO2- –> NO3-

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8
Q

Examples of some bacteria involved in nitrogen cycle and their role

A

Azobacter: Nitrogen fixing bacteria free living in soil

Rhizobium: Nitrogen fixing bacteria, symbiotic relationship with plants, found in the nodules of legumes and provide ammonium compounds in return for sugar

Nitrobacter: Nitrifying bacteria that convert nitrites into nitrates

Pseudomonas: Denitrifying bacteria found in water logged conditions (low O2) that convert nitrates into nitrogen gas

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9
Q

Explain denitrification

A

Process of converting nitrates to nitrogen gas and nitrates back into nitrites via denitrifying bacteria

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10
Q

Explain nitrogen fixation

A

Process of reducing nitrogen gas to ammonia via nitrogen fixing bacteria

N2 –> NH3/NH4+

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11
Q

How could a farmer make farmland more fertile

A

Add NH3 and NO3- ion fertiliser
Crop rotation with legumes
Aerate the soil by ploughing
Drain the soil (no waterlogging)

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12
Q

How is oxygen inhibition of nitrogenase limited

A

Plants make haemoglobin to remove excess oxygen from rhizobia

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13
Q

How do nitrogen fixing bacteria limit oxygen inhubition of niteogenase

A

High rate of aerobic respiration uses oxygen and keeps concentration low in Azobacter

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14
Q

What is nitrogenase

4

A

OFF SPEC (FOR ESSAY)

Enzyme inside certain microorganisms that splits nitrogen gas by adding hydrogen
Catalyses the fixation of N2 to NH3 inside bacteria
Enzyme is sensitive to oxygen
Plants make haemoglobin to remove excess oxygen from rhizobia

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15
Q

Explain ammonification

A

Idk

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16
Q

Explain decomposition

A

Conversion of nitrogen containing compounds in the soil (e.g. dead organisms and waste) into ammonia/ammonium ions via sapriobionts

17
Q

Where are phosphates found

A 
ATP
DNA
RNA
NADP
RuBP
TP
GP
Phospholipid bilayer
18
Q

What are the 2 types of fertiliser

A

Organic/natural –> Made of waste like manure
Inorganic/artificial –> Manufactured/man-made powders or pellets made in factories containing nitrates, phosphates and potassium ions

19
Q

What is deposition

A

A geological process in which sediments, soil and rocks are added to a landform or land mass

Wind, ice, water and gravity transport eroded sediment which due to loss of kinetic energy is deposited, building up layers of sediment

20
Q

Explain the phosphate cycle

A

Dissolved phosphate ions in oceans, lakes and soil is absorbed by plants
Phosphates enter animals via feeding and digestion of plants
Excretion leads to dissolved phosphate ions in water/soil
Decomposition leads to erosion and phosphates in water/soil
Deposition leads to phosphates in rocks
Erosion and fertilisers lead to dissolved phosphates in water/soil
Sedimentation of dissolved phosphates leads to phosphates in rocks

21
Q

What is the impact of fertilisers

A

Reduced species diversity (plants adapted to soil with high nitrate concentration outcompete other species)
Environmental issues (crops removed mean less decomposition so less nitrates returned to soil. Fertilisers replace this)
Leaching
Eutrophication

22
Q

What is leaching

A

Inorganic fertilisers result in more ions applied to the soil than are taken up by the roots
Ions dissolve in water and are washed from the soil into streams, rivers and lakes

23
Q

What is eutrophication

A

Leaching of NO3- and PO4^3- in water leads to it building up
Plants like algae flourish and absorb the nutrients fo be used in respiration
Algal blooms block sunlight from reaching other plants
Plants die due to lack of photosynthesis and O2 in water is depleted
Decomposition further deoleats O2 through breaking down dead plants (aerobic respiration requires O2)
O2 levels so low that fish and organisms die
Death of ecosystems

24
Q

What are mycorrhizae

A

Fungi that have a symbiotic relationship with plants
Colonise root systems of host plants (nodules)
Have very thin hair like structures (mycelium) to increase the surface area for fungi to fix N2, take up water and ions
Provides these in return for sugar from photosynthesis of the plants (e.g. sucruse)

25
Q

How do microorganisms make carbon in dead organisms available to cells in a leaf

A

Saprobionts secrete hydrolytic extra-cellular enzymes onto dead organisms/tissue for digestion
Absorb products (smaller molecules like amino acids) across their membrane
Respiration by microorganisms produces CO2
CO2 is taken into leaves
Through stomata

26
Q

What is erosion

A

Once rocks have been weakened and broken up by weathering erosion occurs
Rocks and sediments are picked up and moved by ice, water, wind or gravity
Can also have chemical erosion

A Level Biology Paper 2 (16 decks)

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