HL Content Statements

• B2.2.4

  Adaptations of the mitochondrion for production of ATP by aerobic cell respiration

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  Include these adaptations: a double membrane with a small volume of intermembrane space, large surface area of cristae and compartmentalization of enzymes and substrates of the Krebs cycle in the matrix.

• B2.2.5

  Adaptations of the chloroplast for photosynthesis

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  Include these adaptations: the large surface area of thylakoid membranes with photosystems, small volumes of fluid inside thylakoids, and compartmentalization of enzymes and substrates of the Calvin cycle in the stroma.

• B2.2.6

  Functional benefits of the double membrane of the nucleus

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  Include the need for pores in the nuclear membrane and for the nucleus membrane to break into vesicles during mitosis and meiosis.
  

• B2.2.7

  Structure and function of free ribosomes and of the rough endoplasmic reticulum

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  Contrast the synthesis by free ribosomes of proteins for retention in the cell with synthesis by membrane- bound ribosomes on the rough endoplasmic reticulum of proteins for transport within the cell and secretion.

• B2.2.8

  Structure and function of the Golgi apparatus

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  Limit to the roles of the Golgi apparatus in processing and secretion of protein.
  

• B2.2.9

  Structure and function of vesicles in cells

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  Include the role of clathrin in the formation of vesicles.

• B2.3.7

  Adaptations to increase surface area-to-volume ratios of cells

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  Include flattening of cells, microvilli and invagination. Use erythrocytes and proximal convoluted tubule cells in the nephron as examples.

• B2.3.8

  Adaptations of type I and type II pneumocytes in alveoli

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  Limit to extreme thinness to reduce distances for diffusion in type I pneumocytes and the presence of many secretory vesicles (lamellar bodies) in the cytoplasm that discharge surfactant to the alveolar lumen in type II pneumocytes. Alveolar epithelium is an example of a tissue where more than one cell type is present, because different adaptations are required for the overall function of the tissue.

• B2.3.9

  Adaptations of cardiac muscle cells and striated muscle fibres

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  Include the presence of contractile myofibrils in both muscle types and hypotheses for these differences: branching (branched or unbranched), and length and numbers of nuclei. Also include a discussion of whether a striated muscle fibre is a cell.

• B2.3.10

  Adaptations of sperm and egg cells

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  Limit to gametes in humans.