Protein Digestion & Protein Turnover

Essential amino acids are from the _____?

diet

Non-essential amino acids are from the _____?

body

Non-essential amino acids are synthesized initially from ______?

glucose

What are the 2 ways non-essential amino acids are synthesized?

1. Glycolysis
2. TCA Cycle

What enzyme hydrolyzes proteins to smaller polypeptides in the stomach?

Pepsin

What enzymes turn the polypeptides into amino acids in the small intestine?

- trypsin
- chymotrysin
- elastase
- carboxypeptidases
- aminopeptidases

Amino acids are absorbed through the _________ and enter the _____?

absorbed through intestinal epithelial cells and enter the blood

The inactive form of digestive protease enzymes are called?

zymogens (-ogen)

Trypsinogen is activated by ________ to form active protease trypsin?

enteropeptidase

Which digestive enzyme plays a key role in activating other pancreatic zymogens?

trypsin

Trypsin cleaves peptide bonds with _______ groups?

carboxyl group

Chymotrypsin favors residues that contain _______ amino acids?

hydrophobic

Elastase cleaves ______?

elastin

Carboxypeptidase A releases ______ amino acids?

hydrophobic

Carboxypeptidase B releases ______ amino acids?

basic

Aminopeptidases is a ______ inhibitor?

trypsin

Absence of the trypsin inhibitor leads to what disease?

pancreatitis

(activation of zymogens --> digestion of intracellular pancreatic proteins)

What 3 transporters are used to absorb amino acids?

1. Na+-dependent carriers
2. ATPase pump
3. Facilitated transporter

Na+-dependent carriers transports _____ & _____ into intestinal epithelial cell?

Na+ & amino acid

ATPase pump lets _____ out of the cell?

NA+

Facilitated transporter lets _____ out of the cell into interstitial fluid?

amino acids

During starvation, the _______ takes up amino acids from the ______ to use as an energy source

facilitated transporter
blood

What is a deficiency of protein in a diet called?

Kwashiorkor

What are some effects of Kwashiorkor?

- muscle wasting
- decreased concentration of plasma proteins
- fluid retention
- permanent effects on growth & mental ability

Protein is a _____?

fuel

If their carbon skeletons can be converted to a precursor of glucose then it's a ______ amino acid?

glucogenic

If their carbon skeletons can be converted directly to acetyl CoA or acetoacetate then it's a ______ amino acid?

ketogenic

What are the products of glucogenic amino acids?

- glucose
- CO2

Glutamate --> _________ --> ________ --> glucose

glutamate --> alpha-ketoglutarate --> malate --> glucose

Glutamate is used for synthesis of what 4 things?

- glutamine
- proline
- ornithine
- arginine

What are the products of ketogenic amino acids?

- acetoacetate
- acetyl CoA

What enzyme synthesizes tyrosine?

Phenylalanine hydroxylase (PAH)

What coenzyme synthesizes tyrosine?

tetrahydro biopterin (BH4)

BH4 & tyrosin hydroxylase are required for synthesis of ________?

catecholamines

BH4 & trypotphan hydroxylase are required for synthesis of _______?

serotonin

Phenylketonuria (PKU) is a disorder resulting from loss of gene coding for _______?

Phenylalanine hydroxylase (PAH)

PKU will (drop/raise) phenylalanine concentration?

raise

What are the symptoms of PKU?

- jerky movements in the arms & legs
- mental retardation
- lighter skin & eyes

Albinism is a defect in ______ metabolism?

tyrosine (tyrosinase deficient)

What are some symptoms of albinism?

- hypopigmentation
- vision defects
- photophobia
- increase risk for skin cancer

Alkaptonuria is a deficiency in ____?

homogentisic acid oxidase

Alkaptonuria will (increase/decrease) homogentisic acid?

increase

What are the symptoms of alkaptonuria?

- early onset of arthritis
- black urine
- black pigment in cartilage & collagenous tissue