1. What are the three cell types found in the pancreas' Islets of Langerhans, and what do they secrete?

• α-cells: secrete glucagon

• β-cells: secrete insulin

• δ-cells: secrete somatostatin

2. Other than insulin and glucagon, which other hormones may influence the serum [glucose]?

There are several, but the most important are:

• Catacholamines: epinephrine and norepinephrine

• Glucocorticoids: most important being cortisol

• Somatotrophin: a pituitary hormone

All of the above increase serum [glucose]. The only hormone that is known to decrease serum [glucose] is insulin.

3. What are the possible metabolic fates for glucose molecules in the body?

• Glycolysis: they may be metabolised by glycolysis and then to the tricarboxylic acid (TCA) cycle following the production of pyruvate

• Storage: as glycogen, through the process of glycogenesis. Most tissues of the body are able to do this

• Protein glycosylation: this is a normal process by which proteins are tagged with glucose molecules. This is by strict enzymatic control

• Protein glycation: this is where proteins are tagged with glucose in the presence of excess circulating [glucose]. It is not enzymatically controlled unlike the above example. An example of this is glycosylated haemoglobin

• Sorbitol formation: this occurs in various tissues when glucose enters the polyol pathway that ultimately leads to the formation of fructose from glucose

4. Where do the body's glucose molecules come from?

• The diet

• Glycogenolysis: following the breakdown of glycogen

• Gluconeogenesis: this is the generation of glucose from non-carbohydrate precursors

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