Breakdown Of Food Flashcards
What are proteins broken down into?
Amino acids
What are carbohydrates broken down into?
Sugars
What are lipids broken down into?
Glycerol and fatty acids
How s glucose converted to pyruvic acid?
Glycolysis forming glyceraldehyde 3 phosphate which is converted to pyruvic acid
Converted to acetyl coA which enters the krebs cycle
How is starch/glycogen broken down?
Amylase breaks it down into maltose/sucrose/lactose
How is maltose broken down?
By maltose to form glucose
How is sucrose broken down?
By sucrase to form glucose+fructose
How is lactose broken down?
By lactase to for glucose and galactose
How are carbohydrates absorbed?
Na+/glucose transport
Glucose/galactose moves into cell with one Na+
Na+ leaves cell and is exchanged for K+
However, fructose moves in via GLUT5 and leaves via GLUT2
How is fructose absorbed?
Moves in via GLUT5 and out via GLUT2
How are proteins broken down?
Broken down by pepsin and pancreatic proteases
Exogenous proteins -> di and tri peptides
Endogenous proteins -> amino acids
How are di and tri peptides absorbed?
Through PEPT1 then move out of cell not capillary through Na+ independent channels
How are amino acids transported?
Through Na+ dependent or independent channels then into capillary through Na+ independent channels
What produced trypsinogen?
Pancreatic zymogens
What activates trypsinogen to form trypsin?
Enterokinase (brush border)
How are lipids digested?
Large lipid droplet is mixed and bile salts are added forming micelles.
Pancreatic lipase digests them to form fatty acids and monoglycerides
What happens in the endoplasmic reticulum of mucosal cells to fatty acids and monoglycerides?
Triglycerides are synthesised
Chylomicrons are formed
Exocytosis of chylomicrons into lymphatic vessels
What vitamins are fat soluble?
D E A K
How are vitamins absorbed into the small intestine?
Passively
Facilitated by bile and incorporated into chylomicrons
How is vitamin D absorbed?
Absorbed not chylomicrons and vitamin D binding protein
What does the liver convert vitamin D3 into?
25(OH)D which is active
Where does 25(OH)D travel to?
Kidneys where it is converted to 1alpha-25(OH)D
What is the function of vitamin A (retinol)?
Epithelial tissue maintenance, vision
What is the role of vitamin D (cholecalciferol)?
Bone calcification
Parathyroid hormone
What is the role of vitamin E (tocopherol)?
Biological antioxidant
What is the role of vitamin K?
Blood clotting
What happens to B12 in mouth?
Unbound B12 may be absorbed under the tongue
How is B12 absorbed in the stomach?
Enzymes and acid cause protein bound B12 to detach from protein
R protein picks up B12
IF secreted
What happens to B12 in upper small intestine?
R protein releases B12
IF picks up B12
What happens to B12 in lower small intestine?
IF-B12 attaches to IF-B12 receptor on intestinal cell
Some unbound B12 absorbed into intestinal cell through passive diffusion
What happens to B12 in intestinal cell?
B12 attaches to transcobalamin II
What happens to B12 n the blood?
Transcobalamin II carries B12 to the body’s cells where it is used, and to the liver where it is stored on transcobalamin III
Transcobalamin III also circulates in the blood
What happens to B12 in the liver?
B12 is stored and released into the small intestine via the bile
What s the role of vitamin B1 thiamine?
Carbohydrate metabolism
What is the role of vitamin B2 riboflavin?
Hydrogen transfer
What is the role of pyridoxine B6?
Protein metabolism
What is the role of vitamin B3 niacin?
Hydrogen transfer
What is the role of folic acid?
Single carbon metabolism
What is the role of B12 cyanocobalamin?
Red blood cell formation
How is iron absorbed as Heme?
Travels from lumen of intestine through HCP1
Processed by an endosome to form Fe2+
How is dietary iron absorbed?
Converted from Fe3+ to Fe2+ in the lumen of intestine, then travels in via DMT1
How is iron absorbed as ferritin?
Ferritin absorbed and encapsulated in a lysosome then converted to Fe2+
