Nutrient Digestion and Absorption I and II Flashcards
What form of carbohydrates are small enough to be absorbed by the small intestine ?
Monosaccharides
Where is the primary area of disaccharide breakdown within the alimentary system ?
The enzymes on the brush border of the small intestine
How is starch broken down in the Alimentary system ?
Hydrolysed by amylase (pancreatic and saliva)
How is cellulose broken down in the alimentary system ?
It cant be broken down, no enzymatic digestion in vertebrates
What is the stored form of glucose within the liver ?
Glycogen
What kind of cells are found within the small intestine ?
Cuboidal cells
What are the 2 layers of the cell within the small intestine ?
Basolateral membrane and the apical membrane
What is found on the upper membrane of the cells within the small intestine ?
The brush border
Which transporter on the apical membrane of the cell transports glucose ?
SGLT1
Which transporter on the basolateral membrane of the cell transports glucose into the bloodstream ?
GLUT-2
What kind of bonds are found in carbohydrates ?
Glycosidic bonds
What kind of bonds are found in proteins ?
Peptide bonds
What do proteases and peptidases do ?
Digest proteins
What do endopeptidases do ?
Digest protein by breaking down the middle of the protein structure
What do exopeptidases do ?
Digest protein by cutting the ends of the protein so it can be broken down
What is the name of the transporter that allows amino acids across the cell barrier ?
SAAT1
Which transporter on the apical border requires a proton coupled process ?
PepT1
Which transporter on the apical border recycles protons and brings in Na ?
NHE3
What is the name of the transporter on RBC that allows Glucose into their cell ?
GLUT-1
What is the name of the transporter that allows Fructose to be absorbed into the small intestine ?
GLUT-5
Where in the Alimentary system are fats broken down ?
The small intestine
What enzyme breaks down fat and what organ secretes this enzyme ?
Lipase and the pancrease
Define emulsification
The breakdown of large lipid droplets into smaller lipid droplets which allows Lipase to act on a larger surface area.
What allows for easier digestion of lipid droplets ?
The decreased size of the droplets creates a larger surface area for lipase to act
Emulsification requires what ?
1: Mechanical disruption of large lipid droplets to small droplets (muscle contractions within the gut)
2: An emulsifying agent
What does an emulsifying agent do ? and give an example of the agent in lipid breakdown
Prevents the small lipid droplets from re-aggregating and becoming large again.
In lipid breakdown the agent is bile salts and phospholipids
Absorption of fat across the cell is enhanced by what ?
Micelles
What are micelles made of ?
bile salts and phospholipids and FA’s and monoglycerides
what components of the original lipid are allowed to cross the cell barrier ?
Fatty acids and monoglycerides
What is the fate of the fat molecules that are absorbed across the cell ?
The FA’s and monoglycerides enter the smooth ER where they are reformed into Triglycerides by enzymes within the smooth ER.
The triglycerides are then coated by an emulsifying agent creating vesicles.
The vesicles are then transported through the cell through the golgi apparatus and exocytosed into the ECF.
What are chylomicrons ?
Extracellular fat droplets
Where do chylomicrons go during the fat absorption process ?
Pass between the endothelial cells into lacteals as they cannot pass through the capillary basal membrane.
Name 4 fat soluble vitamins
A,D,K and E
Name 3 water soluble vitamins
B Group
C Group
Folic Acid
What is vitamin B12 ?
A large charged molecule
How is vitamin B12 absorbed in the Alimentary system ?
Binds to intrinsic factor within the stomach to form a complex which is then absorbed via a specific transport process in the distal ileum
What is the medical term for B12 deficiency ?
Pernicious anaemia
How is iron transported across the brush border ?
Via a transporter known as DMT1 as an H coupled reaction in duodenal enterocytes
What is Ferritin ?
An iron-protein complex and is how iron is stored within cells
How does unbound iron travel in the bloodstream ?
Binds to transferrin
