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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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The two forms of glucose

  • The most well-known carbohydrate monomer is glucose

  • Glucose has the molecular formula C6H12O6

  • Glucose is the most common monosaccharide and is of central importance to most forms of life

  • There are different types of monosaccharide formed from molecules with varying numbers of carbon atom, for example:

    • Trioses (3C) e.g. glyceraldehyde

    • Pentoses (5C) e.g. ribose

    • Hexoses (6C) e.g. glucose

  • Glucose exists in two structurally different forms – alpha (α) glucose and beta (β) glucose and is therefore known as an isomer

    • This structural variety results in different functions between carbohydrates

Diagram showing the straight chain and ring structures of alpha and beta glucose, highlighting carbonyl and hydroxyl groups, with labels on positions.
Straight chain and ring structural formula of alpha & beta glucose

  • Different polysaccharides are formed from the two isomers of glucose

Polysaccharide

Alpha Glucose

Beta Glucose

Starch

✓

X

Glycogen

✓

X

Cellulose

X

✓

Examiner Tips and Tricks

You must be able to recognise and draw the isomer rings of α and β glucose.

Biological molecules: key terms

  • The key molecules that are required to build structures that enable organisms to function are:

    • Carbohydrates

    • Proteins

    • Lipids

    • Nucleic Acids

    • Water

Diagram comparing lipids, showing triglyceride components, and nucleic acids, illustrating DNA with nucleotides, phosphate, sugar, and bases.
Diagram showing inorganic water and organic molecules, including proteins and carbohydrates, with examples of biological molecules in living organisms.
The key biological molecules for living organisms

  • Carbohydrates, proteins, lipids and nucleic acids contain the elements carbon (C) and hydrogen (H) making them organic compounds

  • Carbon atoms are key to the organic compounds because:

    • Each carbon atom can form four covalent bonds – this makes the compounds very stable (as covalent bonds are so strong they require a large input of energy to break them)

    • Carbon atoms can form covalent bonds with oxygen, nitrogen and sulfur

    • Carbon atoms can bond to form straight chains, branched chains or rings

  • Carbon compounds can form small single subunits called monomers, that bond with many repeating subunits to form large molecules called polymers, by a process called polymerisation

  • Macromolecules are very large molecules

    • That contain 1000 or more atoms therefore having a high molecular mass

    • Polymers can be macromolecules, however not all macromolecules are polymers as the subunits of polymers have to be the same repeating units

Carbohydrates

  • Carbohydrates are one of the main carbon-based compounds in living organisms

  • All molecules in this group contain C, H and O

  • As H and O atoms are always present in the ratio of 2:1 (e.g. water H2O, which is where ‘hydrate’ comes from) they can be represented by the formula Cx (H2O)y

  • The three types of carbohydrates are monosaccharides, disaccharides and polysaccharides

Types of carbohydrate table

 

Monosaccharide

Disaccharide

Polysaccharide

Definition

A single sugar monomer, all of which are reducing sugars

A sugar formed from two monosaccharides joined by a glycosidic bond in a condensation reaction

A polymer formed by many monosaccharides joined by a glycosidic bond in a condensation reaction

Examples

Glyceraldehyde (3C)

Ribose (5C)

Glucose (6C)

Maltose (α glucose + α glucose)

Sucrose (α glucose + fructose)

Lactose (α glucose + β galactose)

Cellulose (monomer is β glucose)

Starch (monomer is α glucose)

Glycogen (monomer is α glucose)

Function

Energy in respiration

Building blocks of polymers

Sugar in germinating seeds (maltose)

Mammal milk sugar (lactose)

Sugar stored in cane sugar (sucrose)

Energy storage (plants – starch; animals – glycogen)

Structural cell wall (cellulose)

Examiner Tips and Tricks

When discussing monomers and polymers, give the definition but also name specific examples e.g. nucleic acids – the monomer is a nucleotide.

You need to be able to define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide.