Lecture Flashcards
Digestion in stomach
Gastric parietal cells release HCL: disrupts protein structure and concerts pepsinogen to pepsin.
Protein sources
- Exogenous: Animal (meat, poultry, fish, dairy products) and plant (gains, legumes, vegetable)
- Endogenous: desquamated mucosal cells and digestive enzymes and glycoproteins
Pepsin function
Cleve’s peptide bonds within and distant from the ends of a polypeptide chain to form large polypeptide and oligopeptides.
Digestion in small intestine
CCK and secretin: synthesized in duodenum in response to acid chyme and trigger pancreatic acrobat cells to secrete bicarbonate, electrolytes, water and digestive proenzymes (trypsinogen, chymitrypsinogen, procarboxypeptidase).
Digestive enzyme activation
- Trypsinogen (enteropeptidase) trypsin
- Procarboxypeotidase (trypsin) carboxypeptidase.
- Chymotrypsinogen (trypsin) chymotrypsin
End products of protein disgestion
Protein to large polypeptides to AA, dipeptides and tripeptides.
Complete protein
Meat, poultry, fish, eggs, milk, cheese, yogurt.
Incomplete protein
Plants, legumes, grains, nuts, seeds, vegetables.
Essential AA
TV TILL PM and histidine
Non essential AA
Also get from diet
Synthesized in vivo if nitrogen sufficient
Met to cyt and phe to tyr
Protein absorption
AA absorbed in proximal small intestine: paracellular transport and AA transporters.
Peptides absorbed via PEPT1: more rapid than AA transporter and primary system for AA absorption.
Supplementation with individual AA
Supplemental free AA may impair the absorption of AA in diet.
RDA
0.8g
Protein in body
Skeletal muscle
50% of protein in body represented by only 4 proteins: myosin, actin, collagen, hemoglobin.
Functions
Major functional and structural component of every cell in the body: enzymes, transport proteins, hair, fingernails, keratin, collagen.
Large part is amino nitrogen.
