digestion+absorption Flashcards
The action of endopeptidases and exopeptidases can increase the rate of protein digestion.
Describe how. (2 marks)
- Exopeptidases hydrolyse the peptide bonds at the end of a polypeptide.
- Endopeptidases hydrolyse the internal peptide bonds within a polypeptide.
——> This produces smaller polypeptides and peptides increasing the surface area.
—–> Endopeptidases expose more ends for the exopeptidases to work on
Give one name of the body protein that could have resulted in reduced immunity.
Antibodies.
Suggest which type of dietary protein would be better for old men to eat to cause a net gain
of body proteins. Use the information provided to explain your answer. (3 marks)
- Whey because it absorbs quicker
- It still stimulates protein synthesis
- Less breakdown of protein .
Describe the role of enzymes in the digestion of proteins in a mammal. (4 marker)
- Exopeptidases: hydrolyse peptide bonds at the end of the polypeptide chain into dipeptides
- Endopeptidases: hydrolyse internal peptide bonds of the polypeptide chain into smaller polypeptide and 2 amino acids
- membrane bound dipeptidases: hydrolyse dipeptidases into 2 single amino acids using dipeptidases
The food eaten by a rabbit is digested mainly by microorganisms in its caecum. The
caecum is a section of intestine attached between the ileum and the large intestine. The
resulting semi-digested material leaves the anus of a rabbit as soft, caecal droppings. The
rabbit then eats these caecal droppings.
Use this information and Figure 2 to suggest how eating its own caecal droppings helps a
rabbit’s digestion and absorption of dietary protein.
By eating its own caecal droppings, semi-digested material passes through the digestive system a second time which means protein and amino acids digested into the stomach and absorbed into the small intestine. This ensures more proteins are broken down into amino acids to maximise nutrient extraction from food
Suggest and explain why the combined actions of endopeptidases and exopeptidases are
more efficient than exopeptidases on their own.
- Endopeptides hydrolyse internal peptide bonds producing smaller polypeptides. This exposes more free ends for the exopeptidases to act on.
The addition of a respiratory inhibitor stops the absorption of amino acids.
Use the diagram to explain why.
- No active transport of sodium ions
- Sodium ions dont move in and out of the cell
- So there is no diffusion gradient for sodium ions to move with amino acids
Describe the role of the enzymes of the digestive system in the complete breakdown of starch.
Amylase hydrolyses glycosidic bonds in starch producing disaccharide maltose.
Membrane bound disaccharide: Maltose glycosidic bonds hydrolysed by maltase into glucose.
Describe the processes involved in the absorption of the products of starch digestion.
Glucose moves in with sodium into epithelial cells via specific carrier and channel proteins.
Sodium ions will be removed from the epithelial cell through active transport into the blood mantaining a low concentration of sodium ions in the epithelial cells.
Glucose moves into the blood via faciliatated diffusion
