E&T: Digestion and Absorption Flashcards
What are carbohydrates broken down by?
Amylase
Membrane-bound disaccharidases
Amylase
Digestive enzyme that catalyses the conversion of starch into maltose, which involves the hydrolysis of glycosidic bonds in starch.
Where is amylase produced?
By salivary glands and pancrease
Membrane-bound disaccharidases
Enzymes attached to cell membranes of epithelial cells lining the ileum which break down disaccharides into monosaccharides.
Hydrolyses glycosidic bonds.
What is the disaccharidase for:
- maltose?
- sucrose?
- lactose?
- maltase
- sucrase
- lactase
How can monosaccharides be transported across the cell membranes of the ileum epithelial cells?
Via specific transporter proteins
What are lipids broken down by?
Lipase
Bile salts
Lipase
Enzymes that catalyse the breakdown of lipids into monoglycerides and fatty acids.
Hydrolyses ester bonds.
Where are lipases made?
Where do they work?
In pancreas
Work in small intestine
Where are bile salts produced?
Liver
Bile salts
Emulsify lipids - cause them to form small droplets which increases the SA available for lipases to work on
What are proteins broken down by?
Exopeptidases and endopeptidases
Once the lipid has been broken down (bile salts), what happens?
Monoglycerides and fatty acids stick to the bile salt to form micelles
Endopeptidases
Hydrolyse peptide bonds within a protein.
Give an example of an endopeptidase:
Pepsin - released into stomach by cells in stomach lining.
Only works in acidic conditions eg hydrochloric acid in stomach
Exopeptidases
Hydrolyse bonds at the ends of protein molecules - remove single amino acids from proteins.
Dipeptidases
Exopeptidases that work specifically on dipeptides - act to separate the two amino acids by hydrolysising peptide bonds between them.
Where are dipeptidases often located?
Cell-surface membrane of epithelial cells in small intestine
Where are the products of digestion absorbed across?
Ileum epithelium into the bloodstream
How are these monosaccharides absorbed:
- Glucose
- Galactose
- Fructose
- Absorbed by active transport with sodium ions via a co-transporter protein.
- Absorbed the same way as glucose.
- Absorbed via facilitated diffusion through a different transporter protein.
How are glcyerides and fatty acids absorbed?
- Micelles move them towards epithelium.
- As micelles constantly break, they release monoglycerides and fatty acids to be absorbed.
- Lipid-soluble so diffuse directly across epithelial cell membrane.
How are amino acids absorbed?
- Via co-transport.
- Sodium ions actively transported out of ileum epithelial cells into blood.
- Creates sodium ion concentration gradient.
- Sodium ions diffuse from lumen of ileum into epithelial cells via sodium-dependent transporter proteins - carry amino acids with them.
Digestive enzyme that catalyses the conversion of starch into maltose, which involves the hydrolysis of glycosidic bonds in starch.
Amylase
Enzymes attached to cell membranes of epithelial cells lining the ileum which break down disaccharides into monosaccharides.
Hydrolyses glycosidic bonds.
Membrane-bound disaccharidases
Enzymes that catalyse the breakdown of lipids into monoglycerides and fatty acids.
Hydrolyses ester bonds.
Lipase
Emulsify lipids - cause them to form small droplets which increases the SA available for lipases to work on
Bile salts
Hydrolyse peptide bonds within a protein.
Endopeptidases
Hydrolyse bonds at the ends of protein molecules - remove single amino acids from proteins.
Exopeptidases
Exopeptidases that work specifically on dipeptides - act to separate the two amino acids by hydrolysising peptide bonds between them.
Dipeptidases
