Nutrient Digestion 1 (Carbohydrates and Proteins) Flashcards
What are the 6 main principal dietary constituents?
Carbohydrate Protein Fat Vitamins Minerals Water
What are the 3 hexose sugars?
Glucose
Galactose
Fructose
What absorbs monosaccharides?
Small intestine
What are disaccharides?
2 monosaccharides linked together by glycosidic bond
What happens to disaccharides?
Broken down to constituent monomers by brush border enzymes in small intestine
What is lactose?
Glucose + galactose
What is sucrose?
Glucose + fructose
What is maltose?
Glucose + glucose
What is starch?
Plant storage form of glucose
What is alpha-amylose?
Glucose linked in straight chains
What is amylopectin?
Glucose monomers linked by alpha-1,4 glycosidic bods - hydrolysed by amylases (saliva, pancreas)
What is cellulose?
Constituent of plant cell walls
Unbranched, linear chains of glucose monomers linked by beta-1,4 glycosidic bonds
Why can’t vertebrates use cellulase to break down beta-1,4 glycosidic bonds?
Vertebrates cannot produce cellulase which is the only enzyme that can break down beta-1,4 glycosidic bonds
Vertebrates can only digest through bacteria
What is glycogen?
Animal storage form of glucose
Glucose monomers linked by alpha-1,4 glycosidic bonds
What do you need in order to absorb glucose?
Sodium
What is SGLT1?
Transporter that has a binding site for Na and a binding site for glucose but they need to bind simultaneously to cause a conformational change
What is GLUT2?
Expressed in epithelial cells - facilitated diffusion process since glucose cannot move out of the cell on its own
What happens after sodium and glucose move into the cell?
Glucose moves into the blood (via GLUT2)
Na–> blood, potassium moves into cell (via Na-K pump) which creates an osmotic gradient allowing water to travel from lumen –> blood
How does fructose move through cells?
Fructose moves from lumen into cell via GLUT-5 and moves into blood via GLUT-2
Na not required
What are proteins?
Polymers of amino acids linked together by peptide bonds with large variations in length
What are small proteins classed as and what are they called?
3-10 amino acids in length
Called peptides
What are the enzymes called that hydrolyse peptide bonds and reduce proteins/peptides to amino acids?
Proteases or peptidases
How does an amino acid move through a cell?
Needs a symporter to pull amino acid into cell
SAAT1 has binding sites for Na and amino acid which binds to both simultaneously which causes a conformational change
Creates water absorption effect due to Na moving onto Na-K pump
Describe the process of di/tri-peptides moving into cell?
Process which takes peptides instead of full amino acid
H and the dipeptide both move into the cell via PepT1
H moves back out the cell at the same time Na moves in via NHE3
Involves Na-K pump
What is it called when a H ion is involved?
Proton motive force
What is NHE3?
Sodium hydrogen exchanger
Takes Na in and H ion out and acidifies it
