Nutrient digestion and absorption 1 Flashcards
List the 6 main dietary constituents
Carbohydrate, fat, protein, vitamins, minerals and water
Name some minerals
Zinc, manganese and salt
Name the 3 monosaccharides
glucose, galactose, fructose
What are disaccharides?
2 monosaccharides linked by a glycosidic bond
How are disaccharides broken down?
By enzymes in the brush border
What are the 3 disaccharides?
Maltose, sucrose and lactose
What are each of the disaccharides made from and what enzyme breaks each down
Maltose = 2 glucose (maltase) sucrose = glucose and fructose (sucrose) lactose = glucose and galactose (lactose)
Can alpha amylase work only on alpha or beta 1,4 glycosidic bonds?
alpha
What are the 2 forms of starch?
alpha amylose and amylopectin
Where are the 2 sites of amylase production?
Pancreas and saliva
What can break down cellulose?
Bacteria only as human do not possess the enzyme cellulase
What 2 of the 3 polysaccharides can be broken down by alpha amylase?
starch and glycogen
What are villi?
Small finger like projections found in the small intestine to increase surface area
What type of epithelium are villi covered in?
Columnar
What is on top of villi which is also known as the brush border?
Microvilli
What are the 2 membranes of the microvilli known as?
Apical and basolateral
What separates each microvilli membrane?
Tight junction complex and attachment proteins
Name the 3 transport mechanisms for the microvilli
Transcellular, paracellular and transport mediated
What is glucose coupled to for absorption?
sodium
What transporter do glucose and sodium enter the microvilli by?
SGLT1
What happens to glucose once it enters the cell?
Accumulates until normal blood glucose level (5mmol/l) and is then delivered to the gut by GLUT2
What pathway does the water that follows take?
Paracellular
What other monosaccharide follows the same process as glucose?
Galcatose
What is the difference for fructose?
Uses GLUT5 instead of SGLT1 and is not coupled to sodium
What is a protein?
Amino acids linked by peptide bonds to form polymers
What number of amino acids form a peptide?
3-10
What is the name of the enzymes generally which act to hydrolyse peptide bonds?
proteases/peptidases
What is an endopeptidase?
Enzyme which hydrolyses the protein in the middle part of the chain
What is an exopeptidase?
Enzyme which hydrolyses the protein at one of the terminal ends - carboxyl and amino
Are amino acids coupled to sodium for transport?
Yes
What transporter do amino acids use?
SAAT1
How do amino acids exit the cell after absorption?
Depends on the class of amino acid
What transporter is used for di/tri peptides?
pepT1
What are the transport of di/tri peptides linked to?
Hydrogen ions
How do di/tripeptides exit the cell?
As peptides or amino acids
What is the hydrogen coupled to in order to leave the cell after the peptide has exited?
sodium via NHE3 transporter
What is the acid microclimate due to?
mucus
