Digestion

Digestion

The hydrolysis of large, insolvable molecules into smaller molecules that can be absorbed across the cell membrane.

Where are lipids digested

Small intestine

Bile

Greenish fluid produced by the liver made up of important digestive chemicals:

• Mineral salts

• Bile salts

Mineral salts

Eg. Sodium hydrogen carbonate

Neutralise stomach acid to provide neutral ph for enzymes in the small intestine

Bile salts

Lipids are emulsified by bile salts into tiny droplets increasing surface area for lipase (enzyme) to act on

How are lipids digested

Lipase hydrolyses the ester bonds between monoglycerides and fatty acids

Describe the process involved in the absorption and transport of digested lipid molecules from the ileum into the lymph vessels

1. Micelles contain bile salts and fatty acids / monoglycerides

2. Make fatty acids / monoglycerides more soluble in water

3. Fatty acids \ monoglycerides absorbed by diffusion

4. Triglycerides reformed in cells

5. Vesicles move to cell membrane / exocytosis

Enzymes involved in the digestion of proteins and their roles

Endopeptidases - hydrolyse peptide bonds within a polypeptide

Exopeptidase’s - break bonds between specific amino acids at the end of a polypeptide

Dipeptidases - break dipeptides into amino acids

Explain how sodium ions are involved in co-transport

Sodium ion are actively transported out of the into the lumen creating a diffusion gradient

The sodium ions then move back into the cell by facilitated diffusion and the glucose molecules are carried with it

Then glucose and sodium ions pass through the cell and into the blood by facilitated diffusion

What does salivary amylase break down starch into

Maltose

What does pancreatic amylase do

Hydrolyses any remaining polysaccharides into maltose