Biochem

Question 1

Contents of mucus

Answer 1

94% water
5% mucins
various cell molecules, electrolytes, remnants of cells

Question 2

functions of mucins

Answer 2

help lubricate & form a protective physical barrier on epithelial surfaces
High content of NeuAc (N-acetylneuraminic acid) and sulfate residues on mucins gives negative charge.
Dense oligosaccharide chains make them resistant to proteases.
Mask surface antigens -> tumor cells will have increased mucins to mask them from immune surveillance

Question 3

What forms the cross-links in elastin?

Answer 3

desmosines

cross-linking causes it to mature & become insoluble + very stable

Question 4

What occurs in CF to make mucin stickier?

Answer 4

higher sulfation
In CF, mucins have altered solubility and are smaller in size (normally, respiratory mucin is the largest mucin in the body)

Question 5

What does higher concentration of mucin in mucus do?

Answer 5

decreases the pH, making the mucus viscous and stickier.
decreased pH decreases the buffering capacity of mucus making the lung more vulnerable to environmental acid exposure
Mucin has O-glycosidic bonding for attaching and joining sugars to hydroxyl group

Question 6

Mucins expressed in airways

Answer 6

MUC1, MUC4, MUC13

Question 7

mucin that functions as a receptor for pseudomonas

Answer 7

MUC1

Question 8

What increases expression of MUC2? Decreases it?

Answer 8

Increased: bacterial infection
Decreased: dexamethasone

Question 9

enzymes from mast cells that disrupt the epithelial barrier to allow inflammatory mediators to enter the mucosa & cause inflammation in asthma

Answer 9

chymase & tryptase

Question 10

enzyme balanced by alpha1-antitrypsin

Answer 10

elastase

Question 11

source for arachidonic acid and precursors for eicosanoids

Answer 11

glycerophospholipids

Question 12

Main component of surfactant

Answer 12

phosphatidylcholine (DPPC) -> 70-80%

Question 13

what neutralizes ozone?

Answer 13

uric acid in the nasal cavity
GSH
ascorbic acid

Question 14

Functions of NO in the respiratory system

Answer 14

1. bronchodilation (eNOS)
2. signaling molecule for mucin release
3. cilia beat frequency is NO-dependent
4. regulation of the TH1 cells which amplify and prolong the response of TH2 cells in allergic asthma
5. inhibition of smooth muscle proliferation (airway remodeling)

Question 15

What determines the respiratory quotient?

Answer 15

If carbohydrate is the energy source, the RQ of production of CO2 for O2 consumed is 1:1 or 1.
If fat is a higher percentage of the diet, as in western culture, the RQ = 0.8 (what is used in the alveolar air equation as the exchange ratio).