Unit 3 Digestion and Absorption

Question 1

What is Digestion?

Answer 1

Digestion is the hydrolysis of large, insoluble organic compounds into small soluble molecules, so that they can be absorbed into the blood. ​

Question 2

Describe the complete digestion of starch

Answer 2

In the mouth;,
Salivary amylase,
Hydrolyses glycosidic bonds in starch to produce maltose;
In the duodenum,
Pancreatic amylase
hydrolyses starch into maltose;
In the ileum maltase hydrolyses maltose into glucose;

Question 3

Describe the complete digestion of proteins

Answer 3

In the stomach;​
Endopeptidase (pepsin);​
hydrolyses internal peptide bonds in proteins;​
To produce smaller polypeptide chains;​
In the duodenum;​
Pancreatic juice contains endo and exopeptidase;
Exopeptidase hydrolyses external peptide bonds in proteins;​
To produce dipeptides and amino acids;
In the ileum;​
Dipeptidase;​
hydrolyses dipeptides;​
Into amino acids;

Question 4

Describe the location of maltase

Answer 4

In the cell membrane of epithelial cells that line the ileum.

Question 5

Name the four enzymes present in the cell membrane of the epithelial cells that line the ileum

Answer 5

dipeptidase
sucrase
lactase
maltase

Question 6

What is the function of bile?

Answer 6

In duodenum;​
Bile salts emulsify fats;​
Increasing surface area;​
for faster digestion by pancreatic lipase;

Question 7

Describe and explain what happens to the pH when lipids are hydrolysed.

Answer 7

Decreases/becomes more acidic;
Because fatty acids are produced and they are weak acids;

Question 8

Describe the complete digestion of lipids.

Answer 8

In duodenum;​
Lipase in Pancreatic juice;​
Hydrolyses the ester bond in triglycerides;​
To produce glycerol and 3 fatty acids;

Question 9

Describe the process of cotransport

Answer 9

1. Sodium ions are actively transported out of the epithelial cells into the blood via the sodium-potassium pump​.
2. maintaining a concentration gradient for sodium ions to diffuse into the epithelial cell from the lumen;
   3.Sodium ions move by facilitated diffusion from the lumen along with glucose by facilitated diffusion via the sodium-glucose co-transporter (symporter).​
3. inside the cell glucose and sodium ions separate
   5.Glucose moves from the epithelial cell into the blood by facilitated diffusion via its carrier protein.

Question 10

Describe how lipids are absorbed

Answer 10

1. Fatty acids and monoglycerides surrounded by phospholipid and bile salts to form micelles;​
2. Fatty acids and monoglycerides diffuse across the membrane;​
3. Triglycerides resynthesized in the SER;​
4. Short chain fatty acids move into blood by diffusion;​
5. Triglycerides surrounded by protein in the golgi body;​
6. Form chylomicrons; ​
7. Diffuse into the lymph vessel/lacteal;​