Chemical digestion Flashcards
(54 cards)
Where does the digestion of carbs begin and what is the pH?
- mouth: salivary amylase
- 6.75 - 7
What happens to salivary amylase in the stomach?
inactivates because of stomach acid
Where is most starch reduced to maltose?
in small intestine by pancreatic amylase
Which enzymes in the small intestine complete carbohydrate digestion?
- dextranase
- glucoamylase
- maltase
- sucrase
- lactase
What are the main sources of protein in the diet?
- dietary proteins (125g/day)
- enzymes proteins (15-25 g/ day)
- protein (15-25 g/day)
What do these proteolytic enzymes break protein down into?
free amino acids and some di- and tripeptides
What does pepsin break down in protein digestion?
pepsin cleaves peptide bonds
- tyrosine and phenylalanine
What proteolytic enzymes are involved in protein digestion in the small intestine?
- pancreatic trypsin
- chymotrypsin
- carboxypeptidase
- aminopeptidase
- dipeptidase
What enzymes from the pancreas digest nucleic acids?
RNAase and DNAase
Where does significant lipid digestion occur and what emulsifies it?
the small intestine
What enzymes break down triglycerides in lipids?
pancreatic lipase
What enters the large intestine at the end of the ileum?
some water, indigestible food materials (cellulose) and million of bacteria enter via the ileocecal valve
What are the products of triglyceride digestion?
fatty acids and glycerol/ 2 mono glycerides
How much food, drink and GI secretion enter the GI tract daily?
10L, but only 0.5 - 1 L reaches large intestine
What are the final products of nucleic acid digestion?
free bases, pentose sugars and phosphate ions
What do pancreatic nucleases break RNA and DNA into?
nucleotides
What enzymes in the small intestine further break down nucleotides?
nucleosidases and phosphatases
What are the final products of nucleic acid digestion absorbed?
absorbed through villi into the blood
What does it imply that mast digestion and absorption are complete by the time chyme reaches the ileum?
to recycle bile salts via portal circulation to the liver
How are glucose and galactose absorbed?
through common protein carriers using active transport linked to Na+
How does fructose and monosaccharides move into cells
by facilitated diffusion (no ATP required)
How are amino acids absorbed?
using several types of amino acids carriers, with secondary active transport linked to Na+
How are di- and tripeptides absorbed?
actively transported into epithelial cells, then digested into single amino acids in the cytoplasm
Why can infants sometime absorb whole proteins?
their intestinal mucosa is immature, lacking certain cellular structures
- can contribute to allergies
