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A Level Biology Edexcel A > Biodiversity & Natural Resources > Flashcards

Biodiversity & Natural Resources Flashcards

1
Q

Give the function of the cell wall.

A

Provides strength and support to the cell.

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2
Q

Give the function of chloroplast.

A

Site of photosynthesis.

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3
Q

Give the function of amyloplast.

A

Stores amylopectin/ starch.

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4
Q

Give the function of tonoplast.

A

Seperates the contents of the cytoplasm from the contents of the vacuole.

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5
Q

Give the function of plasmodesmata (singular plasmodesma).

A

Cytoplasmic connections allowing transfer of substances between two adjacent cells.

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6
Q

What is parenchyma.

A

Type of plant tissue found throughout plant.

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7
Q

Compare the differences in structure of animal cells and plant cells.

A
  • Plant cells contain chloroplasts, animal cells do not.
  • Plant cells contain a rigid cellulose cell wall, animal cells do not.
  • Plant cells contain a large central vacuole (permanent), animal cells do not.
  • Animal cells contain centrioles, plant cells do not.
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8
Q

Give the function of cellulose.

A

Structural component of plant cell walls, provide strength and support.

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9
Q

Describe the structure of cellulose.

A

Made of beta glucose joined by 1,4 glycosidic bonds in condensation reactions. Unbranched structure. Every alternate B-glucose in cellulose is inverted.

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10
Q

Describe the structure of a cellulose microfibril.

A
  • Composed of 60-70 (many) cellulose molecules held together by hydrogen bonds.
  • Contains beta glucose joined by 1,4 glycosidic bonds in condensation reactions.
  • Unbranched chain.
  • Every alternate B-glucose in cellulose is inverted.
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11
Q

Describe the structure of xylem vessels.

A
  • Cellulose microfibrils in cell walls
  • Walls thickened with lignin often in rings or spirals to allow for flexibility.
  • Continuous column made of hollow, dead cells, with no end walls and no cell contents
  • Have pits in their walls
  • Vessels have open ends
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12
Q

Describe the structure of phloem.

A
  • Has a cellulose cell wall
  • Sieve tube elements have thin peripheral cytoplasm and very few organelles
  • Have sieve tubes with sieve pores
  • A companion cell is linked to each sieve tube by plasmodesmata
  • living tissue
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13
Q

Describe the structure of sclerenchyma fibres.

A
  • Fibres have cellulose cell walls which are thickly lignified
  • Dead and hollow cells when mature
  • Often have pits in their walls
  • Long, narrow and usually pointed at both ends.
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14
Q

Describe the function of the xylem vessels.

A

Transport of water and dissolved mineral ions from roots to leaves and provide structural support.

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15
Q

Describe the function of the phloem.

A

Transport of organic solutes e.g sucrose from source to sink through translocation.

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16
Q

Describe the function of the sclerenchyma.

A

Provide structural support only.

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17
Q

What are calcium ions needed for?

A

To make calcium pectate needed for forming the middle lamella which holds plant cells togehter. Also has role in membrane permeability.

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18
Q

What are magnesium ions needed for?

A

To make chlorophyll needed for photosynthesis, Also needed in activation of some plant enzymes and nucleic acid synthesis.

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19
Q

What are nitrate ions needed for?

A

To make amino acids needed for the synthesis of proteins for growth. Also needed for chlorophyll, nucleic acids e.g. dna and rna, ATP, growth hormones.

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20
Q

What are phosphate ions needed for?

A

Needed for ATP + ADP (energy transfer), for lipid membranes and nucleic acids.

21
Q

Symptoms of calcium ion deficiency.

A

Young leaves turn a yellow colour and go crinkly. Growing points (top/ bottom) die back, stunted growth.

22
Q

Symptoms of magnesium ion deficiency.

A

Less chlorophyll leads to less photosynthesis so less glucose being made and stunted growth. Yellowing of leaves between veins.

23
Q

Symptoms of nitrate ion deficiency.

A

Older leaves turn yellow and die. Lack of side shoots/ branches (spindly plants). Stunted growth due to lack of enzymes/ proteins.

24
Q

Symptoms of phosphate ion deficiency.

A

Very dark leaves with purple veins. Stunted growth.

25
Q

Explain how the structure of xylem relates to its function.

A
  • Lignin and cellulose microfibrils in walls for strength to prevent vessel collapsing.
  • Lignin in walls also make the xylem vessel stronger and waterproof.
  • Large cross-sectional area allows a larger volume of water to be transported.
  • Pits in the walls allow lateral movement of water between xylem vessels.
  • No end walls forms a cnontinuous dead hollow tube with no cell cytoplasm which reduces resistance to water flow.
  • Lignin in rings/ spirals allow stretching and flexibility as the plant grows.
26
Q

Describe transpiration/ water transport.

A

Water evaporates from surface of leaves by transpiration out through the stomata. This creates a low hydrostatic pressure in leaves which draws water out of the xylem vessels by osmosis. A continuous column of water molecules (transpiration stream) is pulled under tension up the xylem by capillary action. Due to cohesion (H bonding between polar molecules in xylem) and adhesion ( H bonding between water and cellulose in the xylem walls), water moves into roots by osmosis creating a high hydrostatic pressure. Water moves along a hydrostatic pressure from high in roots to low in leaves by mass flow.

27
Q

Describe the uses of water in plants.

A
  • reactant in photosynthesis
  • Polar molecule so is a solvent - surrounds ions and polar molecule, dissolves them and forms hydrogen bonds.
  • Used as a transport medium in transpiration and translocation
  • Used in hydrolysis of bonds
  • Creates turgor pressure to support plants
  • Temperature regulation by evaporation.
  • Surface tension of water
  • Used as medium for chemical reactions e.g in cytoplasm
28
Q

Explain how the structure of phloem relates to its function.

A
  • Transfer cells for loading sucrose into the sieve tube at the source or unloading at the sink.
  • Sieve tube has sieve plates (end walls) which have sieve pores so fluid can flow through continuously
  • Companion cell with organelles e.g many mitochondria to provide metabolic support for the sieve tube element cells.
  • Peripheral cytoplasm of sieve tube has very few organells (no nucleus) so less resistance to fluid flow.
29
Q

Explain what is meant by translocation.

A

Transport of organic molecules from one part of the plant to another in the phloem by mass transport (can be in both directions).

30
Q

Describe the process of translocation.

A

At the source (leaf) sucrose is produced. Transfer cells actively pump sucrose into phloem sieve tubes against a concentration gradient using energy ATP. There is a high sucrose concentration in sieve tube at the source which draws water into the sieve tube by osmosis from adjacent xylem vessels, increasing the hydrostatic pressure of the loading end of the sieve tube. Fluid in sieve tube flows from high to low hydrostatic pressure by mass transport. Sucrose is actively unloaded in sinks so solute concentration decreases in the sieve tube at the sink. Water moves back into xylem by osmosis, decreasing the hydrostatic pressure.

31
Q

How do bacteria reproduce?

A

By binary fission, type of asexual reproduction which produces two genetically identical cells. Growth is exponential.

32
Q

Describe and explain the conditions required for bacterial growth.

A
  • Optimum temperature for optimum enzyme activity, rate of reaction and growth/ metabolism.
  • Optimum pH for optimum enzyme activity, rate of reaction and growth/ metabolism.
  • Optimum oxygen concentration for respiration to release energy for growth.
  • Optimum concentrations of nutrients e.g. glucose for respiration to release energy and nitrogen for making amino acids to make proteins for growth and DNA.
  • Moisture/ water for cell function e.g. hydrolysis reactions
  • No build up of toxic waste products.
33
Q

Define generation time.

A

How long it takes between new cell forming and cell division.

34
Q

Describe the stages of growth of a bacterial culture.

A
  • Lag phase - no increase in cell numbers, cells adjust to conditions
  • Log/ exponential phase - cell numbers increases steeply, cells divide at the fastest rate possible for the conditions doubling each time.
  • Stationary phase - no change in cell numbers, glucose is depleted, waste products build up, change in pH.
  • Death phase - number of cells decreases, number of cells dying is greater than number of new cells formed.
35
Q

How do you calculate number of bacteria?

A

Bacteria at the end of the growth period = bacteria at the beginning × 2^number of divisions

36
Q

Describe the structure of starch.

A

Composed of alpha glucose joined together by glycosidic bonds in condensation reactions. Made of amylose and amylopectin. Amylose: 1,4 glyosidic bonds, straight chain spiral. Amylopectin: 1,4 and 1,6 glycosidic bonds, branched chain.

37
Q

Describe the uses of starch from seeds.

A
  • Stiffening agents e.g. fabric/ paper.
  • Superabsorbents e.g. for nappies.
  • Starch foam e.g. for packaging
  • Thickening agents e.g. for custard/ wallpaper paste. Starch granules allow water to be absorbed and be thickened.
38
Q

Define sustainable.

A

A resource that can be renewed, so will no run out and is therefore available for future generations.

39
Q

Explain why plastics/ petrol are not sustainable.

A

Plastic/ petrol comes from crude oil which is a finite fossil fuel so is non-renewable and will run out, so will not be available for future generations. Plastics do not degrade.

40
Q

Explain why starch/ plant products are sustainable.

A
  • They are made from plants which are a renewable resource which will not run out as plants can be grown to replace those used, so will be available for future generations.
  • They biodegrade/ decompose more quickly so will not contribute to landfill.
41
Q

Describe Withering’s historic drug testing protocol.

A
  • Potentially useful plant chemical identified
  • Trial on a small group of patients with disease - side effects recorded.
  • Trial on larger group of patients to discover the most effective dosage.
  • Results recorded and published.
42
Q

What are the stages of contemporary drug testing protocol.

A
  • Pre-clinical trials
  • Clinical trials phase 1
  • Clinical trials phase 2
  • Clinical trials phase 3
  • Clinical trials phase 4 (After Licensing)
43
Q

Describe pre-clinical trials.

A

Lab testing on cells/ tissue cultures and animals to assess safety (side effects) and determine if drug is effective against disease.

44
Q

Describe clinical trials phase 1.

A

Small group of health volunteer given drug to look for side effects in humans. Different doses are trialled to find out which one is safe and effective.

45
Q

Describe clinical trials phase 2.

A

Drug is tested on a small group (100-300) volunteer patients who have the disease to determine the effectiveness of drug.

46
Q

Describe clinical trials phase 3.

A

Double blind randomised trial using a larger group of patients (1000-3000) to check for efficacy and side effects. Control group improves validity. Statistical analysis of data to see if drug is effective.

47
Q

Describe clinical trials phase 4 (after licensing).

A

Drug licensed. Data on efficacy and safety continues to be collected/ monitored.

48
Q

Define placebo.

A

An inactive substance which does not contain the drug. Used as a control to compare to the actual drug.

49
Q

Define double-blind trial.

A

Some people are given the drug and some are given placebo (or existing drug) and neither the doctor nor the patient know who has been given the actual drug and who has been given the placebo. Removes bias.

A Level Biology Edexcel A (6 decks)

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