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Flashcards in Exam 1 Deck (57)
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1
Q

Food

A

Source of building material and energy for building up or renewing body structures

2
Q

Digestion

A

Degradation of nutrient molecules into components simple enough to be absorbed in intestine

3
Q

Absorption

A

Uptake of digested components

4
Q

Protein received

A

diet and endogenous sources

5
Q

Protein from diet

A

70-100 g

6
Q

Protein from endogenous sources

A

35-200 g

7
Q

Endogenous sources for protein

A

enzymes and epithelial cells

8
Q

Amount of protein lost in feces daily

A

6-12 g

9
Q

Endopeptidases

A

cleave internal peptide bonds

10
Q

Exopeptidases

A

cleave one amino acid at a time

11
Q

Exopeptidase subclassifications

A

carboxypeptidase and aminopeptidase

12
Q

Carboxypeptidase

A

cleave the -COOH terminal

13
Q

Aminopeptidase

A

cleave the -NH2 terminal

14
Q

Endopeptidases cut large polypeptides to smaller ____________ which are then acted on by _________

A

oligopeptides; exopeptidases

15
Q

Final products of protein digestion

A

dipeptides/tripeptides and amino acids

16
Q

Stomach

A
  • secretes HCl (pH 1-2)

- pepsinogen and pepsin

17
Q

Pepsinogen

A

secreted by the chief cells in the stomach lining and is activated to pepsin in the acidic environment

18
Q

Pepsin

A

digests protein into large peptide fragments and some free amino acids

19
Q

Pancreas

A
  • produces several proteases: typsin, chymotrypsin, elastase

- large amounts of sodium bicarbonate to neutralize the acid from the stomach to promote pancreatic protease activity

20
Q

Trypsin

A

cleaves proteins at lysine and arginine residues

21
Q

Chymotrypsin

A

cleaves at aromatic amino acids

22
Q

Elastase

A

cleaves at smaller hydrophobic amino acids

23
Q

Membrane-bound enzymes, endopeptidases, dipeptidases, and amino peptidases act on _____ and _____ in the GI tract

A

oligopeptides and dipeptides

24
Q

Oligopeptides and dipeptides are broken down to _____ and _____

A

free amino acids and dipeptides and tripeptides

25
Q

Free amino acids and di and tripeptides are absorbed across the membrane by ______

A

specific carrier-mediated transport

26
Q

Di and tripeptides are absorbed with the help of _____

A

H+-dependent symporters

27
Q

Amino acids are absorbed using _____

A

Na+-dependent transporters

28
Q

Di and tripeptides are further hydrolyzed into ______ inside the _____

A

amino acids; enterocyte (intestinal cell)

29
Q

Endoproducts are carried into the ______

A

portal venous system

30
Q

Aliphatic amino acids

A

saturated hydrocarbon side chains

31
Q

Aromatic amino acids

A

involved in hydrophobic reactions

32
Q

Serin and threonine

A

hydroxyl side groups

33
Q

Asparagine and glutamine

A

amide-bearing side chains and polar

34
Q

Serine, threonine, and asparagine

A

primary sites of linkage of sugars to proteins forming glycoproteins

35
Q

Acidic amino acids

A

carboxylic acids on their side chains

36
Q

Lysine

A

additional amino group at side chain

37
Q

Histidine

A

imidazole ring as the side chain and catalyst in many enzymes

38
Q

Methionine

A

nonpolar methyl group in its side chain

39
Q

Cysteine

A

stabilizes the protein structure and participates in the formation of disulfide bonds with other cysteine residues

40
Q

Cyclic amino acid

A

pyrrolidine ring side chain

41
Q

Amino acids

A

amphoteric molecules (zwitterions)

42
Q

Isoelectric point

A

the point at which the acidic and basic side chains in a protein are balanced and the overall net charge of the protein is zero

43
Q

Basic proteins

A

lysine and arginine

44
Q

Acidic proteins

A

aspartate and glutamate

45
Q

pI

A

pI=pK1+pK2/2

46
Q

Buffers

A

solutions that minimize a change in H+

47
Q

Buffer pair

A

weak acid and weak base

48
Q

Angiotensin

A

peptide hormone that affects blood pressure

49
Q

Proteins contain between _____ and _____ amino acid residues

A

50; 2000

50
Q

Molecular weight can be determined by…

A

mass spectrophotometry

51
Q

Primary Structure

A

linear; charge and polarity

52
Q

Secondary Structure

A

local structure of the polypeptide chain; alpha helix or beta pleated sheet

53
Q

Alpha helix

A
  • rod like structure
  • 3.6 amino acid residues per turn of the helix
  • wind clockwise
  • ribbon, stick, or space-filling models
54
Q

Beta-pleated sheet

A
  • several parallel alpha helixes
  • extended structure
  • carbon-carbon bonds are tetrahedral
  • cannot be planar configuration
55
Q

Tertiary Structure

A
  • folding of the peptide chain
  • three dimensional
  • stabilized by interactions between the side-chain functional groups
56
Q

Tertiary structure stabilization

A
  • covalent disulfide bonds
  • hydorgen bonds
  • salt bridges
  • hydrophobic interactions
57
Q

Quaternary Structure

A
  • interactions between peptide chains
  • assembly of two or more separate peptide chains that are held together by non covalent or covalent interactions
  • tetrameric protein