Digestion of Carbohydrates and Proteins Flashcards
What are the principle dietary nutrients?
- Carbohydrate
- Protein
- Fat
- Vitamins
- Minerals
- Water
What are the 3 monosaccharides?
- Glucose
- Galactose
- Fructose
What are hexose sugars?
Breakdown products of complex CHOs which are absorbed by small intestine
What are disaccharides?
2 monosaccharide linked together by glycosidic bond
How are disaccharides broken down?
Broken down to constituent monomers by brush border enzymes in small intestine
What is lactose composed of?
Glucose and galactose
What is sucrose composed of?
Glucose and fructose
What is maltose composed of?
Glucose and glucose
What enzyme breaks down lactose?
Lactase
What enzyme breaks down sucrose?
Sucrase
What enzyme breaks down maltose?
Maltase
Name 3 polysaccharides.
- Starch
- Cellulose
- Glycogen
What is starch?
Plant storage form of glucose
What is cellulose?
Constituent of plant cell walls
What is glycogen?
Animal storage form of glucose
What is the structure of a-amylase?
Glucose linked in straight chains
What is the structure of amylopectin?
Glucose chains highly branched
What is the structure of starch?
Glucose monomers linked by a-1,4 glycosidic bonds
What breaks down starch?
Amylases
Where are amylases found?
- Saliva
- Pancreas
What is the structure of cellulose?
Unbranched, linear chaind of glucose monomers linked by B-1,4 glycosidic bonds
Why is cellulose known as dietary fibre?
There is no enzymatic digestion in vertebrates
What is the structure of glycogen?
Glucose monomers linked by a-1,4 glycosidic bonds
Where are the disaccharide ‘ases’ expressed?
Brush border
Where is the apical membrane found?
Microvilli
Where is the basolateral membrane found?
Membrane furthest from the lumen
How are the cells in the small intestine joined?
Tight junctions
How can molecules pass form the gut tube into the body?
- Transcellular
- Paracellular
- Vectorial transport
What is the name of the transporter that transports glucose into the cell?
SGLT1
What is the name of the transporter that transports glucose out of the cell?
GLUT-2
Other than glucose what does SGLT1 also recognise?
Galactose
What is the name of the transporter that transports fructose into the cell?
GLUT-5
What is the name of the transporter that transports fructose out of the cell?
GLUT-2
What are proteins?
Polymers of amino acids linked together by peptide bonds
How do proteins differ?
Amino acids used and chain length
What do proteins often undergo?
Post-translational modification
What are small proteins with chains 3-10 amino acids long known as?
Peptides
What are proteases/peptidases?
They are enzymes which hydrolyse peptide bonds and reduce proteins or peptides to amino acids
What does endopeptidase do?
They act on the internal part of a protein to produce 2 smaller peptides
What does exopeptidase do?
They act on the terminal amino acid of a protein to remove 1 amino acid at a time
Where do aminopeptidases act?
At the amine end of a protein
Where do carboxypeptidases act?
At the carboxylic end of a protein
What is the generic amino acid transporter?
SAAT1
What enters the cell along with amino acids?
Sodium
What is the name of the transporter that transports dipeptides?
PepT1
What is transported along side dipeptides?
Hydrogen
What is the name of the transporter that removes hydrogen from the cell?
NHE3
What enters the cell using the NHE3 transporter?
Sodium
What happens to dipeptides once they are in the cell?
They can pass through into the blood
