There is a high concentration of molecule X outside the cell which enters the cell by facilitated diffusion. The results of measuring the concentration of X inside the cell at 30s intervals are shown by the graph. [Figure 15.1] Why does the concentration of X inside the cell remain constant after 150 s? 1 There is no more of X outside the cell. 2 The number of carrier proteins is limiting. 3 There is no net movement of X.

Fig. 6.1 is a transmission electron micrograph of a plant parenchyma cell. [Figure 6.1]

The diagram shows a phospholipid molecule divided into three regions, X, Y and Z. R, in region X, represents a range ...

Which statements about the fluid mosaic model of a membrane are correct? 1 The movement of phospholipids in the memb...

The diagram shows a molecule of three hexose sugars. [Figure shows diagrams of three hexose sugars labelled 1, 2, 3] ...

Which feature of glycogen distinguishes glycogen from starch?

A student wrote four statements about what happens during hydrolysis of a carbohydrate. 1 Disaccharides are formed fr...