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Biology_A-level_Cie

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  1. 1-1-the-microscope-in-cell-studies
    5 主题
  2. 1-2-cells-as-the-basic-units-of-living-organisms
    5 主题
  3. 2-1-testing-for-biological-molecules
    3 主题
  4. 2-2-carbohydrates-and-lipids
    8 主题
  5. 2-3-proteins
    6 主题
  6. 2-4-water
    2 主题
  7. 3-1-mode-of-action-of-enzymes
    5 主题
  8. 3-2-factors-that-affect-enzyme-action
    8 主题
  9. 4-1-fluid-mosaic-membranes
    4 主题
  10. 4-2-movement-into-and-out-of-cells
    12 主题
  11. 5-1-replication-and-division-of-nuclei-and-cells
    6 主题
  12. 5-2-chromosome-behaviour-in-mitosis
    2 主题
  13. 6-1-structure-of-nucleic-acids-and-replication-of-dna
    4 主题
  14. 6-2-protein-synthesis
    5 主题
  15. 7-1-structure-of-transport-tissues
    4 主题
  16. 7-2-transport-mechanisms
    7 主题
  17. 8-1-the-circulatory-system
    7 主题
  18. 8-2-transport-of-oxygen-and-carbon-dioxide
    5 主题
  19. 8-3-the-heart
    4 主题
  20. 9-1-the-gas-exchange-system
    6 主题
  21. 10-1-infectious-diseases
    3 主题
  22. 10-2-antibiotics
    3 主题
  23. 11-1-the-immune-system
    4 主题
  24. 11-2-antibodies-and-vaccination
    6 主题
  25. 12-1-energy
    5 主题
  26. 12-2-respiration
    11 主题
  27. 13-1-photosynthesis-as-an-energy-transfer-process
    8 主题
  28. 13-2-investigation-of-limiting-factors
    2 主题
  29. 14-1-homeostasis-in-mammals
    8 主题
  30. 14-2-homeostasis-in-plants
    3 主题
  31. 15-1-control-and-coordination-in-mammals
    12 主题
  32. 15-2-control-and-coordination-in-plants
    3 主题
  33. 16-1-passage-of-information-from-parents-to-offspring
    5 主题
  34. 16-2-the-roles-of-genes-in-determining-the-phenotype
    7 主题
  35. 16-3-gene-control
    3 主题
  36. 17-1-variation
    4 主题
  37. 17-2-natural-and-artificial-selection
    7 主题
  38. 17-3-evolution
    2 主题
  39. 18-1-classification
    5 主题
  40. 18-2-biodiversity
    7 主题
  41. 18-3-conservation
    6 主题
  42. 19-1-principles-of-genetic-technology
    11 主题
  43. 19-2-genetic-technology-applied-to-medicine
    4 主题
  44. 19-3-genetically-modified-organisms-in-agriculture
    2 主题
  45. 1-1-the-microscope-in-cell-studies
  46. 1-2-cells-as-the-basic-units-of-living-organisms
  47. 2-1-testing-for-biological-molecules
  48. 2-2-carbohydrates-and-lipids
  49. 2-3-proteins
  50. 2-4-water
  51. 3-1-mode-of-action-of-enzymes
  52. 3-2-factors-that-affect-enzyme-action
  53. 4-1-fluid-mosaic-membranes
  54. 4-2-movement-into-and-out-of-cells
  55. 5-1-replication-and-division-of-nuclei-and-cells
  56. 5-2-chromosome-behaviour-in-mitosis
  57. 6-1-structure-of-nucleic-acids-and-replication-of-dna
  58. 6-2-protein-synthesis
  59. 7-1-structure-of-transport-tissues
  60. 7-2-transport-mechanisms
  61. 8-1-the-circulatory-system
  62. 8-2-transport-of-oxygen-and-carbon-dioxide
  63. 8-3-the-heart
  64. 9-1-the-gas-exchange-system
  65. 10-1-infectious-diseases
  66. 10-2-antibiotics
  67. 11-1-the-immune-system
  68. 11-2-antibodies-and-vaccination
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Arteries, veins & capillaries: structures & functions

 Blood vessel

Structure

Explanation

Muscular artery

Thicker tunica media mainly composed of smooth muscle

Able to perform vasoconstriction and vasodilation

Much less elastin than elastic arteries

Cannot stretch and recoil

Narrow lumen

Blood flows under high pressure

Elastic artery

Thinner tunica media (compared to muscular artery) mainly composed of elastin and collagen

Gives artery the ability to stretch in response to each pulse

Relatively few smooth muscle fibres

Cannot perform vasoconstriction or vasodilation

Narrow lumen

Blood flows under high pressure

Vein

One-way valves

Close to prevent the backflow of blood

Wide lumen

Blood pressure is reduced in veins with no surges

Less smooth muscle and elastin

No need for veins to stretch and recoil

Lots of collagen

Increased strength and structure

Capillary

Very small diameter

Blood travels relatively slowly, giving more opportunity for diffusion to occur

Capillaries branch between cells

Substances can diffuse quickly between cells and the blood quickly

Thin walls, no elastic, smooth muscle or collagen

Capillaries can fit between individual cells and diffusion is rapid

Worked Example

The table below shows features of blood vessels.

Which row of the table is correct? 

 

Feature of elastic artery

Feature of muscular artery

Feature of vein

Feature of capillary

A

One-way valves

Wide lumen

Narrow lumen

Very small diameter

B

Relatively few smooth muscle fibres

Tunica media composed of smooth muscle

Lots of collagen

No elastic, smooth muscle or collagen

C

Wide lumen

Lots of collagen

Little elastic

Tunica media composed of collagen

D

One-cell thick

Narrow lumen

Narrow lumen

Lots of elastic

The correct answer is B.

This is because elastic arteries do not contain many smooth muscle fibres and are not able to perform vasoconstriction or vasodilation. In contrast, muscular arteries contain much more smooth muscle. Veins have large amounts of collagen for strength and keeping their shape, while capillaries are only one-cell thick and so do not contain any elastic, smooth muscle or collagen.

Examiner Tips and Tricks

For “Explain” questions, remember to pair a description of a structural feature to an explanation of how it helps the blood vessel to function. For example, “Capillaries are one-cell thick, which enables quick and efficient diffusion of substances.”