digestion and absorption Flashcards
What occurs during digestion
Large molecules are broken down into smaller ones which can move across cell membranes
Why is the hydrolysis of large biological molecules important in digestion
Because they are broken down into monomers which are easily absorbed from the gut into the blood easily transported around the body for use by the body cells
What is produced during the hydrolysis of carbohydrates?
Carbohydrates + water → disaccharides
What is produced during hydrolysis of disaccharides?
Disaccharides + water → monosaccharides
What is produced during the hydrolysis of fats?
Fats + water → fatty acids + monoglycerides
What is produced during the hydrolysis of proteins?
Proteins + water → amino acids
List the enzymes involved in digestion
- Amylase
- Lipase
- Membrane-bound disaccharidases
- Membrane-bound dipeptidases
Describe the function of amylase
Amylase hydrolyses starch into maltose by hydrolysing glycosidic bonds in starch
Where is amylase produced
Salivary glands and by the pancreas
Where does amylase work in?
Small intestine
Describe the function of membrane-bound disaccharidases
They help to hydrolyze disaccharides into monosaccharides by hydrolyzing glycosidic bonds
Where are membrane-bound disaccharides found?
They are attatched to the cell membrane of epithelial cells lining the ileum
Describe the function of lipase
Catalyses the hydrolysis of lipids into monoglycerides and fatty acids by hydrolysing the ester bonds in lipids
Where is lipase made?
Pancreas
Where does lipase work?
Small intestine
What is the function of bile salts?
Emulsifying lipids to monoglycerides and fatty acids
Where is bile salt produced?
Liver
How are micelles formed?
When the lipid is hydrolysed by lipase, the monoglycerides and fatty acids stick with the bile salts to form micelles
What are proteases?
Enzymes that catalyse the hydrolysis of proteins into amino acids by hydrolysing the peptide bonds between amino acids
What are the types of proteases?
- Endopeptidases
- Exopeptidases
- Dipeptidase
What is the function of endopeptidases?
Hydrolyse peptide bonds in protein between amino acids in the central region into two or more smaller peptides
What is the function of exopeptidases?
Hydrolyses peptide bonds at the ends of protein molecules removing a single amino acid
What is the function of dipeptidases?
They act to separate the 2 amino acids that make up a dipeptide by hydrolyzing the peptide bond between them
Where are dipeptidases found?
In the cell surface membrane of epithelial cells in the small intestine
What happens to the products of digestion?
Products of digestion are absorbed across the ileum epithelium into the bloodstream
Describe what happens to monosaccharides as products of digestion
- Glucose is absorbed by active transport with sodium ions via a co-transporter protein
- Galactose is absorbed by active transport with sodium ions via a co-transporter protein
- Fructose is absorbed via facilitated diffusion through a different transporter protein
Describe what happens to monoglycerides and fatty acids as products of digestion
- Micelles help to move monoglycerides and fatty acids toward the epithelium.
- Because micelles constantly break up and reform they can release monoglycerides and fatty acids, allowing them to be absorbed
- Monoglycerides and fatty acids are lipid-soluble so they can diffuse directly across the epithelial cell membrane
Describe what happens to amino acids as products of digestion
Sodium ions are actively transported out of the epithelial cells to the ileum, they diffuse back into cells through sodium-dependent transporter proteins in epithelial cell membranes carrying amino acids with them
