Digestion and Absorption: Topic 6.1 and part of 6.6

Question 1

List the digestive enzymes produced in the pancreas, and Describe their roles (substrates they act on and products produced).

Answer 1

Amylase - acts on starch and produces maltose
Lipase - acts of triglycerides and produces monoglycerides/fatty acids/glycerol
Endopeptidase (trypsin) - acts on proteins and peptides and produces amino acids

Question 2

State the location where protein BEGINS to be digested and the pH of this environment.

Answer 2

The stomach begins protein digestion and the pH is around 2 in order to denature proteins

Question 3

Outline the methods of transport used to absorb the products of starch, protein, and lipid digestion in the small intestine.

Answer 3

Diffusion: Fatty acids and small non-polar substances easily pass through the hydrophobic cell membranes of epithelial cells through simple diffusion
Osmosis: Water diffuses across epithelial cell membranes in response to the movement of ions and other hydrophilic monomers
Facilitated diffusion: Protein channels within epithelial cell membranes allow passage of hydrophilic food monomers
Active transport: Glucose and amino acids are pumped against their concentration gradients or they are transported with Na ions as those ions are actively pumped across the membrane
Endocytosis: Invagination of the cell membrane to form a vesicle around bulk fluids that must remain intact in the intestinal lumen

Question 4

Explain how the pancreas maintains homeostatic levels of glucose in the blood.

Answer 4

The pancreas uses a negative feedback system to maintain homeostatic levels of glucose in the blood by releasing insulin and glucagon when required. If blood sugar is too high the beta cells in the pancreas will secrete insulin that acts on all cells in the body causing them to take up more glucose. Cellular respiration rates are increased causing an increase in the breakdown of glucose. And glucose uptake and storage by cells decreases the body’s levels. When blood sugar is too high, alpha cells in the pancreas produce glucagon which stimulates liver cells to break down glycogen into glucose, cellular respiration rates are decreased, and glucose is released by hepatocytes into the bloodstream. As glucose levels increase the amount of glucagon production decreases.

Question 5

Explain the causes, symptoms, consequences, and treatment of Type I and Type II diabetes.

Answer 5

Type I
Causes: Early onset, Beta cells damaged or destroyed by body;s own immune system so not enough or no insulin is produced, triggered by various factors not usually genetic
Symptoms: High blood sugar, glucose in urine, increased thirst, hunger, fatigue, weight loss
Treatment: controlled by insulin injections to regulate blood sugar
Type II
Causes: Adult onset, insulin receptors on cells become less sensitive to insulin, related to obesity, genetics, poor diet, lack of exercise, age, ethnicity
Symptoms:High blood sugar, glucose in urine, increased thirst, hunger, fatigue, weight loss

Treatment: Controlled by managing diet and lifestyle

Question 6

State the function of leptin.

Answer 6

Leptin is produced and secreted by cells in adipose tissues to inhibit appetite