Identify the cell labelled Q in Fig. 2.1.
Fluid R is produced from blood in the blood capillary. State and explain one difference between the composition of fluid R and the composition of the blood in the capillary.
The cell surface membranes of the respiring cells help regulate the exchange of substances between the cells of the body and the blood. In the space below, draw a diagram to show the arrangement of phospholipid molecules in the cell surface membrane.
Cholesterol is a molecule present in the cell surface membrane. Describe one role of cholesterol in the cell surface membrane.
Nicotine is one of the substances in tobacco smoke. Nicotine can pass through cell surface membranes and enter the bloodstream. Describe the short-term effects of nicotine on the cardiovascular system.
Nicotine is absorbed from the blood plasma into the cells of the capillary wall. Scientists have suggested that nicotine is moved from the blood plasma into these cells by a co-transporter mechanism. Fig. 2.2 shows how nicotine may move from the blood plasma into a cell. The co-transporter mechanism shown in Fig. 2.2 is different from the co-transporter mechanism that moves sucrose into the cytoplasm of a companion cell in phloem tissue. Outline the similarities and differences between the co-transport of nicotine and the co-transport of sucrose.