Digestion 2 Flashcards
what hydrolyses proteins?
enzymes called peptidases
what type of peptidase breaks down large polypeptides into smaller oligopeptides?
endopeptidase
what type of peptidase breaks down oligopeptides into di- and tripeptides and amino acids?
exopeptidases
what is an enterocyte?
cell of the intestinal lining
in what organ does protein digestion begin?
stomach
the stomach secretes ? which causes protein ?
HCl
denaturation
? cells of the gastric mucosa secrete ? - the inactive precursor of pepsin
chief
pepsinogen
pepsinogen is initially activated by ? to form activated pepsin
low pH
what does pepsin do?
digests the target protein into large peptide fragments and amino acids
the digestion of the target protein by pepsin stimulates ? to be released in the duodenum
cholecystokinin (CCK)
acidity of the stomach contents entering the duodenum stimulates the secretion of what peptide hormone?
secretin
secretin stimulate the secretion of ? rich fluid to ? and ? the acid in the duodenum and also stimulates secretion of ? ? and ? intestinal juice
bicarbonate
neutralise
dilute
alkaline bile
alkaline
cholecystokinin cck stimulates the release of ?
by the ?
the main digestive enzymes
pancreas
cholecystokinin causes contraction of the ? and relaxation of the ? promoting entry of ? and ? into the ?
gall bladder
sphincter of Oddi
bile
pancreatic juices
duodenum
pancreatic enzymes that are released as inactive precursors are called?
zymogens
what converts trypsinogen to trypsin?
duodenal enteropeptidases
what controls the activity of trypsin?
an inhibitory peptide
small intestine peptidases at the brush border of enterocytes are membrane bound ?, ? and ?
endopeptidases
dipeptidases
aminopeptidases
the final digestion of peptides occur ? the enterocytes forming ? by ?
inside
amino acids
cytosolic peptidases
how are amino acids transported into the enterocyte and out into the blood
active mechanisms such as Na+ dependant co-porters
Passive diffusion
di and tri-peptides are transported across the brush border of enterocytes by?
H+ dependant co-porter
creating an electrochemical gradient
amino acids leave the enterocyte into the capillary by what transport mechanism?
facilitated diffusion - Na+ independent
most water soluble vitamins are absorbed by?
passive diffusion
fat soluble vitamins are carried in the ? and absorbed by the ?
micelles
enterocytes
water soluble vitamins are?
b vitamins
c
fat soluble vitamins are?
A
D
E
K
the 4 metabolically important forms of B12 are called?
(not essential to know)
cobalamins
cobalamins are generally bound to ? and are required for what?
(not essential to know)
proteins
red blood cell development
Cobalamins are generally bound to 1. They are released from this complex by 2. They are then bound to a glycoprotein called 3. These complexes are degraded by 4 In the duodenum. The free cobalamin then binds to a glycoprotein called 5. The complex is absorbed into the ileum by 6 Which is 7 Dependant. Within the cell the complex dissociates and free B12 binds to 8 Which leaves the cell, enters the 9 And is taken up by the 10 Using receptor mediated 11 For storage.
(not essential to know)
1 proteins
2 pepsin
3 haptocorrin
4 trypsin -> pancreatic proteinases
5 in5trinsic factor (IF)
6 active transport
7 Ca+
8 transcobalamin
9 portal vein
10 liver
11 endocytosis
vitamin D plays a major role in the regulation of ? 2
calcium and phosphorus metabolism
what are the sources of vitamin D? 2
sun by the action of UV radiation
diet associated with fats
vitamin D deficiency leads to ? 3
calcium malabsorption
rickets in children
osteomalacia in adults
how is the active molecule of vitamin D formed?
hydroxylation in the liver and kidney
where is calcium absorbed?
proximal small intestine
Calcium Regulation
Decrease in ionised calcium in plasma stimulates the release of 1. This promotes Ca2+ reabsorption, from kidney and bone, and increase gut absorption via increased production of 2.
- parathyroid hormone
- activated vitamin D3
Increase in ionised calcium in plasma stimulates release of ? which inhibits resorption (lowers serum Ca2+)
calcitonin
the majority of the bodies iron is found in?
haemoglobin and myoglobin
Deitary iron is in the ferric form 1. It is reduced in the GI tract to the ferrous form 2. It is transported into the enterocytes by 3. When erythrocytes (RBC) are are iron rich iron is stored in the enterocytes incorporated into the protein 4. If not iron is transported across the membrane into plasma. Fe2+ is oxidised to Fe3+ by 5. Fe3+ is then bound to 6 in the plasma. Transferrin is taken up in the bone marrow by 7. The iron is then released, reduced to Fe2+ and transported to the 8 for incorporation into 9.
(really not essential to know)
1 Fe3+
2 Fe2+
3 a divalent metal transporter
4 ferritin
5 ferroxidase
6 transferrin
7 erythrocyte precursor cells
8 mitochondria
9 HEME
