Integument

Question 1

What is collagen?

Answer 1

Collagen is the most abundant protein in the body, providing strength, structure, and support to tissues like skin, bone, cartilage, tendons, and blood vessels.

Question 2

How many types of collagen are there?

Answer 2

There are 28 types of collagen, but Types I, II, III, and IV are the most clinically important.

Question 3

What tissues are associated with Type I collagen?

Answer 3

Type I collagen is found in bone, skin, and tendon.

Question 4

What tissue is associated with Type II collagen?

Answer 4

Type II collagen is found in cartilage.

Question 5

What is Type III collagen associated with?

Answer 5

Type III collagen is associated with reticular fibers in blood vessels and granulation tissue.

Question 6

What is the role of Type IV collagen?

Answer 6

Type IV collagen is found in basement membranes.

Question 7

What are the first steps of collagen synthesis?

Answer 7

1. Transcription & Translation: Collagen genes are transcribed to mRNA and translated into preprocollagen in the rough endoplasmic reticulum.

Question 8

What occurs during hydroxylation in collagen synthesis?

Answer 8

Specific proline and lysine residues are hydroxylated by prolyl and lysyl hydroxylases.

Question 9

What cofactors are required for hydroxylation?

Answer 9

Vitamin C, Iron (Fe²⁺), Oxygen, and α-ketoglutarate.

Question 10

What clinical condition is associated with vitamin C deficiency?

Answer 10

Scurvy, which leads to defective hydroxylation, unstable collagen, bleeding gums, bruising, and poor wound healing.

Question 11

What happens during glycosylation in collagen synthesis?

Answer 11

Hydroxylysine residues are glycosylated, and three α-chains align to form a triple helix, resulting in procollagen.

Question 12

What is procollagen?

Answer 12

Procollagen is the soluble form of collagen that is formed in the rough endoplasmic reticulum.

Question 13

What occurs during the secretion step of collagen synthesis?

Answer 13

Procollagen is packaged into vesicles and transported out of the cell via exocytosis.

Question 14

What happens during the cleavage of procollagen?

Answer 14

Procollagen peptidases remove the N- and C-terminal propeptides to form tropocollagen, the insoluble triple helix form.

Question 15

What clinical condition is associated with defects in procollagen cleavage?

Answer 15

Defects can lead to some types of Ehlers–Danlos syndrome (EDS), especially the classic form.

Question 16

What is the role of lysyl oxidase in collagen synthesis?

Answer 16

Lysyl oxidase oxidizes some lysine/hydroxylysine residues to aldehydes, forming covalent cross-links between tropocollagen molecules.

Question 17

What condition is associated with copper deficiency affecting collagen?

Answer 17

Menkes disease, which leads to weak collagen, brittle hair, growth delay, and neurodegeneration.

Question 18

What is the biochemical defect in Scurvy?

Answer 18

Deficient hydroxylation of proline and lysine due to vitamin C deficiency.

Question 19

What are the symptoms of Scurvy?

Answer 19

Bleeding gums, weak blood vessels, bruising, and poor wound healing.

Question 20

Q3: What causes Menkes disease?

Answer 20

Deficiency in copper → decreased lysyl oxidase activity → poor collagen cross-linking.

Question 21

What are clinical signs of Menkes disease?

Answer 21

Brittle/kinky hair, growth retardation, neurodegeneration, hypotonia.

Question 22

What step of collagen synthesis is affected in Ehlers–Danlos Syndrome (classic type)?

Answer 22

Defective cleavage of procollagen into tropocollagen.

Question 23

What symptoms are seen in classic Ehlers–Danlos syndrome?

Answer 23

Hyperextensible skin, joint hypermobility, atrophic scarring.

Question 24

What gene is mutated in Osteogenesis Imperfecta?

Answer 24

COL1A1 or COL1A2 (Type I collagen).

Question 25

What are symptoms of Osteogenesis Imperfecta?

Answer 25

Brittle bones, frequent fractures, blue sclerae, and hearing loss.

Question 26

What is the mutation in Ehlers–Danlos (vascular type)?

Answer 26

Mutation in COL3A1 (Type III collagen).

Question 27

What are symptoms of vascular Ehlers–Danlos?

Answer 27

Fragile blood vessels, aneurysms, and organ rupture.

Question 28

What collagen is affected in Dystrophic Epidermolysis Bullosa?

Answer 28

Type VII collagen (COL7A1 gene), which forms anchoring fibrils.

Question 29

What symptoms are associated with epidermolysis bullosa

Answer 29

Blistering skin from minor trauma, nail loss, and scarring.

Question 30

What enzyme hydroxylates proline in collagen synthesis?

Answer 30

Prolyl hydroxylase (requires vitamin C, Fe²⁺, O₂, α-ketoglutarate).

Question 31

What enzyme hydroxylates lysine in collagen synthesis?

Answer 31

Lysyl hydroxylase (same cofactors as prolyl hydroxylase)

Question 32

What enzyme removes terminal propeptides from procollagen?

Answer 32

Procollagen peptidase.

Question 33

What enzyme cross-links collagen fibrils?

Answer 33

Lysyl oxidase (requires copper as a cofactor).

Question 34

What are key enzymes in collagen cross-linking not found in keratin synthesis?

Answer 34

Lysyl oxidase (copper-dependent), prolyl/lysyl hydroxylase (vitamin C-dependent).

Question 35

What cells synthesize melanin?

Answer 35

Melanocytes, located in the basal layer of the epidermis.

Question 37

What is the embryological origin of melanocytes?

Answer 37

Neural crest cells.

Question 38

What are the two major types of melanin?

Answer 38

Eumelanin (brown/black) and Pheomelanin (yellow/red).

Question 39

What is the rate-limiting enzyme in melanin synthesis

Answer 39

Tyrosinase

Question 40

What cofactor is essential for tyrosinase activity?

Answer 40

Copper (Cu²⁺)

Question 41

What is the starting molecule in melanin synthesis?

Answer 41

Tyrosine

Question 42

What are the first two reactions catalyzed by tyrosinase?

Answer 42

Tyrosine → DOPA DOPA → Dopaquinone

Question 43

What determines if melanin becomes eumelanin or pheomelanin?

Answer 43

The presence of cysteine promotes pheomelanin formation.

Question 44

What hormone stimulates melanin production via MC1R

Answer 44

α-MSH (Alpha-Melanocyte Stimulating Hormone).

Question 45

What transcriptional pathway is involved in UV-stimulated melanogenesis

Answer 45

UV → p53 → POMC → α-MSH → MC1R → ↑ cAMP → ↑ Tyrosinase

Question 46

What causes the hyperpigmentation in Addison’s disease?

Answer 46

Elevated ACTH, which also stimulates α-MSH, increasing melanin.

Question 47

What disorder is caused by tyrosinase deficiency?

Answer 47

Oculocutaneous albinism (OCA1).

Question 48

What condition results in autoimmune destruction of melanocytes?

Answer 48

Vitiligo

Question 49

What type of melanin is more protective against UV damage?

Answer 49

Eumelanin

Question 50

What skin pigment disorder commonly affects pregnant women?

Answer 50

caused by hormones and sun exposure.

Question 51

What is the gene for elastin synthesis

Answer 51

ELN gene

Question 52

What secretes the fribillin-1

Answer 52

Fibroblast secrete them to form microfribils

Question 53

What is the roll of the lysyl oxidase in elastin synthesis

Answer 53

They oxidize specific lysine residues on tropoelastin which which form cross links with each other

Question 54

What happens after the cross linking of the tropoelastin

Answer 54

Desmosine and iododesmosine are bond are formed which allow elastin to stretch and recoil

Question 55

Name two important biochemical factors involved in intrinsic aging.

Answer 55

Reactive Oxygen Species (ROS) and Advanced Glycation End-Products (AGEs)

Question 56

How do Reactive Oxygen Species (ROS) contribute to skin aging?

Answer 56

They damage DNA, proteins, and lipids, weakening skin structure.

Question 57

What are Advanced Glycation End-Products (AGEs)?

Answer 57

A: Stiff, sticky protein-sugar complexes that damage collagen and elastin.

Question 58

How does UV radiation cause skin damage?

Answer 58

It increases ROS production, breaks down collagen and elastin, and mutates DNA

Question 59

What enzymes are activated by ROS that degrade collagen and elastin

Answer 59

Matrix metalloproteinases (MMPs).

Question 60

What cells secrete tropoelastin into the extracellular matrix

Answer 60

Connective tissue cells (like fibroblasts)

Question 61

Tropoelastin is rich in which hydrophobic amino acids?

Answer 61

Valine, glycine, proline, and alanine

Question 62

Tropoelastin is laid onto which scaffold in the extracellular matrix?

Answer 62

A meshwork of microfibrils made of fibrillin and fibulin.

Question 63

Which enzyme cross-links tropoelastin polypeptide chains

Answer 63

Lysyl oxidase (LOX).

Question 64

What does lysyl oxidase convert lysine into during cross-linking?

Answer 64

Allysine

Question 65

What special cross-links are formed between lysine and allysine from different microfibrils?

Answer 65

Desmosine and isodesmosine.

Question 66

What do desmosine and isodesmosine cross-links create?

Answer 66

A strong, elastic network of elastin fibers and sheets.

Question 67

What glycoprotein do elastin fibers associate with in microfibrils?

Answer 67

Fibrillin

Question 68

Bullous congenital ichthyiosiform erthroderma

Answer 68

K1, K10

Question 69

Ehlers Danlos Syndrome

Answer 69

Mutation of COL5 gene

Question 70

Marfans disease

Answer 70

Mutation of fribillin-1

Question 71

Epidermolysis bullosa simplex

Answer 71

K5, K14

Question 72

Epidermolysis bullosa simplex

Answer 72

Mutation of COL7 gene

Question 73

Ichthyosis bullosa Siemens

Answer 73

K2e

Question 74

Juvenille epithelial corneal dystrophy(Meesman)

Answer 74

K3,K12

Question 75

Pachyonychia congenita

Answer 75

K6, K16

Question 76

Pulmoplantar keratodsis

Answer 76

K9

Question 77

Acts as an anticoagulant and is produced by mast cells

Answer 77

Herapin

Question 78

Plays roles of absorbing shock and is found in the ECM

Answer 78

Chnodrioton-6-sulphate