BIOCHEM

Question 1

Most abundant protein in the human body.

Answer 1

Collagen

Question 2

Collagen general function

Answer 2

Organizes and strengthens extracellular matrix.

Question 3

Collagen synthesis and structure

steps inside fibroblasts and where inside of them

Answer 3

1. Synthesis (RER)
2. Hydroxylation (ER)
3. Glycosylation (Golgi)
4. Exocytosis

Question 4

Collagen synthesis and structure steps outside fibroblasts

Answer 4

5. Proteolytic processing 6. Cross-linking

Question 5

Collagen synthesis and structure Synthesis (RER)

Answer 5

Translation of collagen α chains
(preprocollagen)— usually Gly-X-Y polypeptide (X and Y are
proline, hydroxyproline, or hydroxylysine).

Question 6

Collagen synthesis and structure

Hydroxylation (ER)

Answer 6

Hydroxylation of specific proline and lysine

residues (requires vitamin C).

Question 7

Collagen synthesis and structure

Glycosylation of pro-α-chain lysine residues and formation of procollagen (triple helix of three collagen α chains).

Answer 7

Glycosylation (Golgi)

Question 8

Collagen synthesis and structure
Exocytosis of procollagen into extracellular
space.

Answer 8

4. Exocytosis

Question 9

Collagen synthesis and structure

Cleavage of terminal regions of procollagen transforms it into insoluble tropocollagen.

Answer 9

5. Proteolytic processing

Question 10

Collagen synthesis and structure
Reinforcement of many staggered tropocollagen molecules by covalent lysine- hydroxylysine cross-linkage (by lysyl oxidase) to make col- lagen fibrils.

Answer 10

6. Cross-linking

Question 11

Chédiak-Higashi syndrome mech

Answer 11

is due to a microtubule polymerization defect resulting in ↓ phagocytosis

Question 12

Molecular motors
Dynein =
Kinesin =

Answer 12

Molecular motors
Dynein = retrograde.
Kinesin = anterograde.

Question 13

Drugs that act on microtubules:

Answer 13

1. Mebendazole/thiabendazole (antihelminthic)
2. Taxol (anti–breast cancer) 3. Griseofulvin (antifungal) 4. Vincristine/vinblastine (anti-cancer)
3. Colchicine (anti-gout)

Question 14

Vesicular trafficking proteins:

trans-Golgi → lysosomes, plasma membrane → endosomes (receptor-mediated endocytosis).

Answer 14

Clathrin

Question 15

I-cell disease clinical findings

Answer 15

Characterized by coarse facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes. Often fatal in childhood.

Question 16

I-cell disease mech

Answer 16

failure of addition of mannose-6- phosphate to lysosome proteins, enzymes are secreted outside the cell instead of being targeted to the lysosome.

Question 17

what cells are particularly rich in SER.

Answer 17

Liver hepatocytes and steroid hormone–producing cells of the adrenal cortex

Question 18

Osteogenesis imperfecta 4 findings

Answer 18

1. Multiple fractures
2. Blue sclerae
3. Hearing loss (abnormal middle ear bones)
4. Dental imperfections due to lack of dentition

Question 19

Osteogenesis imperfecta worst type and findings

Answer 19

Type II is fatal in utero or in the neonatal period.

Question 20

5 Immunohistochemical stains and associated cell types

Answer 20

Vimentin - Connective tissue
Desmin - Muscle
Cytokeratin - Epithelial cells
Glial fibrillary acid proteins (GFAP) - Neuroglia
Neurofilaments - Neurons

Question 21

Stretchy protein within lungs, large arteries, elastic ligaments.

Answer 21

Elastin

Question 22

Elhers-Danlos syndrome mech and clinical findings

Answer 22

Faulty collagen synthesis (Type III is most frequently affected (resulting in blood vessel instability) causing:

1. Hyperextensible skin
2. Tendency to bleed (easy bruising)
3. Hypermobile joints 4.Associated with berry aneurysms.

Question 23

Collagen Types Type I

Answer 23

(90%)––Bone, Skin, Tendon, dentin, fascia, cornea, late wound repair.

Question 24

Collagen Types Type II

Answer 24

Cartilage (including hyaline), vitreous body, nucleus pulposus.
Type II: carTWOlage.

Question 25

Collagen Types Type III (Reticulin)

Answer 25

skin, blood vessels, uterus, fetal tissue, granulation tissue.

Question 26

Collagen Types Type IV

Answer 26

Basement membrane or basal lamina. | Type IV: Under the floor (basement membrane)

Question 27

Cilia structure

Answer 27

9 + + 2 arrangement of microtubules. Dynein is an ATPase that links peripheral 9 doublets and causes bending of cilium by differential sliding of doublets.

Question 28

Microtubule structure

Answer 28

Cylindrical structure 24 nm in diameter and of variable length. A helical array of polymerized dimers of α- and β-tubulin (13 per circumference). Each dimer has 2 GTP bound.

Question 29

Microtubule functions

Answer 29

has 2 GTP bound. Incorporated into flagella, cilia, | mitotic spindles.Microtubules are also involved in slow axoplasmic transport in neurons.

Question 30

Vesicular trafficking proteins: | Anterograde, RER → cis-Golgi.

Answer 30

COP II

Question 31

Vesicular trafficking proteins: Retrograde, | Golgi → ER.

Answer 31

COP I

Question 32

6 Functions of Golgi apparatus

Answer 32

1. Distribution center of proteins and lipids from ER to the plasma membrane, lysosomes, and secretory vesicles 2. Modifies N-oligosaccharides 3. Adds O-oligosaccharides 4. Addition of mannose-6- phosphate 5. Proteoglycan assembly 6. Sulfation

Question 33

α1-antitrypsin inhibits

Answer 33

elastase

Question 34

Elastin structure

Answer 34

Rich in proline and lysine, nonhydroxylated forms.

Question 35

Fetal alcohol syndrome worst window

Answer 35

3–8 weeks

Question 36

Plasma membrane wrt cholesterol

Answer 36

High cholesterol or long saturated fatty acid content → increased melting temperature and decreased fluidity.

Question 37

Kartagener’s syndrome mech and clinical findings

Answer 37

Immotile cilia due to a dynein arm defect. Results in male and female infertility (sperm immotile), bronchiectasis, and recurrent sinusitis (bacteria and particles not pushed out); associated with situs inversus.

Question 38

what cells are particularly rich in RER.

Answer 38

Mucus-secreting goblet cells of the small intestine and antibody-secreting plasma cells

Question 39

SER is the site of

Answer 39

steroid synthesis and detoxification | of drugs and poisons.

Question 40

RER is the site of

Answer 40

synthesis of secretory (exported) proteins and of N-linked oligosaccharide addition to many proteins.

Question 41

Checkpoints control transitions between phases. Regulated by

Answer 41

cyclins, cdks, and tumor suppressors.

Question 42

Cell cycle phases | Labile cells what and examples

Answer 42

Never go to G0, divide rapidly with a short G1. | Bone marrow, gut epithelium, skin, hair follicles.

Question 43

Cell cycle phases Stable cells what and examples

Answer 43

Enter G1 from G0 when stimulated. | Hepatocytes, lymphocytes.

Question 44

Cell cycle phases | Permanent cells what and examples

Answer 44

Remain in G0, regenerate from stem cells. | Never go to G0, divide rapidly with a short G1.

Question 45

Cell cycle phases shortest phase

Answer 45

Mitosis

Question 46

Posttranslational modifications Proteasomal degradation

Answer 46

Attachment of ubiquitin to defective proteins to tag them for breakdown.

Question 47

Posttranslational modifications Covalent alterations

Answer 47

Phosphorylation, glycosylation, and hydroxylation.

Question 48

Plasma membrane composition with %'s

Answer 48

Asymmetric fluid bilayer. Contains cholesterol (~50%), phospholipids (~50%), sphingolipids, glycolipids, and proteins.

Question 49

Ouabain mech

Answer 49

inhibits Na+-K+ATPase by binding to K+ site.

Question 50

Na+-K+ATPase location and orientation

Answer 50

Na+-K+ATPase is located in the plasma membrane | with ATP site on cytoplasmic side. For each ATP consumed, 3 Na+ go out and 2 K+ come in.

Question 51

Elastin what and where

Answer 51

Stretchy protein within lungs, large arteries, elastic ligaments.

Question 52

Marfan’s syndrome is caused by a defect in?

Answer 52

fibrillin.

Question 53

Elastin wrt diseases

Answer 53

Emphysema can be caused by excess elastase activity