The response of the human body to tissue damage depends on the types of tissues involved. Epithelial tissue, liver tissue and cardiac muscle tissue each respond differently to damage. • Epithelial tissue of the gas exchange system contains stem cells. • Liver tissue contains cells in a non-dividing state that can enter a cell cycle when stimulated. • Cardiac muscle tissue contains cells that cannot divide at all. Damage is permanent and is associated with scar tissue formation.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.

1. [1] (division that) produces, new / daughter, cells A produces more cells or (so) replaces, damaged / lost / dead, cells ;
2. [1] new / daughter, cells, genetically identical ; A ref. to clone if correct context A genetic information not lost I same number of chromosomes
3. [1] (all) new cells can retain function ; AW
4. [1] cell cycle continuous / continually divide / AW ;
5. [1] (produce cells that) can, differentiate / specialise / described ; A multipotent / pluripotent I totipotent divide to produce a cell that can divide and a cell that differentiates = 2 marks
6. [1] can produce, cells / tissue, that can still function (as before) ;
7. [1] chemicals (released) are cell signalling, molecules / compounds ;
8. [1] liver cells, are target cells ; A liver tissue for liver cells
9. [1] binding of, chemicals / cell signalling molecules, to receptors (of liver cells); R receptor cells
10. [1] ref. to specificity (of receptors) / chemicals complementary to receptors ; if R above, then allow ecf for idea of complementary
11. [1] (specific) response is, cell enters the cell cycle / mitosis / cell division ; A DNA replication
12. [1] AVP ; e.g. idea of communication between cells suggestion of detail following binding, e.g. second messenger activated / enzyme cascade /signal transduction / phosphorylation events / enzyme activation I cascade of reactions