With reference to Fig. 1.1, state how you can distinguish a scanning electron micrograph from a transmission electron micrograph.
The estimated length of a microvillus is $1 \, \mu\text{m}$. Describe the method you would use to estimate the magnifications of the images shown in Fig. 1.1.
Active transport uses water-soluble substances such as $\text{Na}^+$ and $\text{K}^+$, and ATP supplies the energy required for their movement through carrier proteins. Outline other features of active transport.
Glucose molecules move into the cell through a membrane protein. Suggest why glucose molecules must be cotransported with $\text{Na}^+$ as they enter the cell through the membrane protein.
Explain how microvilli raise the uptake of glucose into an intestinal epithelial cell.
Stem cells are also found in the wall of the small intestine. These cells divide continuously by mitosis. Suggest and explain why mitosis by stem cells is important in the small intestine.