Digestion and Absorption

Question 1

Where does protein digestion begein?

Answer 1

In the stomach, pepsin and pepsinogen break down proteins.

Question 2

The roles of hydrochloric acid in the stomach

Answer 2

Hydrochloric acid lowers the pH of the stomach which denatures proteins

Question 3

Outline the hormonal and nervous mechanisms that control the secretion, content, and volume of gastric juice

Answer 3

1. The sight and smell of food triggers a response in the brain (the medulla) which sends impulses to the gastric glands in the stomach to release gastric juice
2. When food enters the stomach stretch receptors detect it
3. Stretch receptors send impulses to brain, the brain then sends a signal to the stomach to trigger gastrin secretion into the bloodstream, which causes the stomach to secrete HCl
4. Gastrin causes the sustained release of gastric juices
5. If the pH becomes too low gastrin is inhibited by hormones
6. Once digested food (chyme) passes into the small intestine, the duodenum then releases CCK hormones to stimulate the pancreas to release pancreatic juices

Question 4

Where does most chemical digestion happen?

Answer 4

In the small intestine

Question 5

Explain the role of the pancreas in digestion

Answer 5

1. Enzymes catalyze/speed up chemical reactions and lower the activation energy needed
2. Digestive enzymes are released into the gut from exocrine glands and breakdown larger molecules
3. Enzymes allow reactions to occur at body temperature
4. Amylase breaks down starch into sugars
5. Lipase breaks lipids into fatty acids

Question 6

General function and structure of villi

Answer 6

1. Folded inner epithelial layer increases surface area for absorption
2. Sealed membrane with tight junctions contain microvilli
3. The Lumen is lined with villi
4. Contain membrane channel proteins to aid in absorption

Question 7

List and explain the different forms of transport used by the small intestine to absorb nutrients

Answer 7

1. Diffusion - fatty acids pass through hydrophobic membranes
2. Osmosis - Water diffuses across epithelial membrane
3. Facilitated Diffusion - Protein channels allow passage of hydrophilic food molecules
4. Active transport - Glucose and amino acids pumped against a concentration gradient
5. Endocytosis - cell membrane forms a vesicle around large molecules

Question 8

Outline the role of the large intestine and explain why lignin and cellulose are not digested in the human body

Answer 8

1. Main function is the absorption of water
2. Secretes mucus
3. Moves undigested food products
4. Materials that are not absorbed are egested
5. Cellulose and lignin are not digested by the human body because humans do not possess the enzymes to break them down

Question 9

Outline the roles of fiber in the diet

Answer 9

1. Helps to clean out old/damaged intestinal cells
2. Provides bulk to keep materials moving
3. Decreases constipation
4. Helps maintain bowel health

Question 10

Outline the cause, consequences, and treatment for stomach ulcers and know the name of the bacteria that causes them

Answer 10

-Stomach ulcers are caused by a bacteria called Helicobacter Pylori

Causes:
-H. Pylori survives the acidic conditions of the stomach by penetrating the mucus lining
-Secretes urease to increase pH and neutralize gastric acids
-Causes inflammation which causes damage to stomach lining

Consequences:
-May lead to stomach wall damage, and can lead to stomach cancers

Treatments:
-Treated with antibiotics and PPI’s