Biochemistry Lecture 1 Flashcards by Ashley Moss

Which of the following is the primary function of collagen?
a) Enzymatic catalysis
b) Energy storage
c) Structural support
d) Cell signaling

Structural support

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Collagen is predominantly synthesized by which cell type?
a) Osteoclasts
b) Chondrocytes
c) Fibroblasts
d) Epithelial cells

Fibroblasts

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The repeating triplet sequence characteristic of collagen is:
a) Ala-Pro-Gly
b) Gly-Pro-Hyp
c) Ser-Thr-Tyr
d) Cys-Met-Lys

B) Gly-Pro-Hyp

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What modification of proline residues in collagen is essential and vitamin C dependent?
a) Glycosylation
b) Phosphorylation
c) Hydroxylation
d) Methylation

C) Hydroxylation

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The secondary structure of an individual collagen alpha chain is best described as a:
a) Right-handed alpha helix
b) Left-handed helix
c) Beta-pleated sheet
d) Random coil

B) Left handed helix

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The primary structure of an individual collagen alpha chain is best described as a:

Helix with 1000 aa

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Tropocollagen, the basic unit of collagen fibrils, consists of:
a) A single polypeptide chain
b) Two identical polypeptide chains
c) Three identical polypeptide chains
d) Three polypeptide chains forming a right-handed triple helix

D) Three polypeptide chains forming a right-handed triple helix

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Collagen fibrils are formed by the supramolecular assembly of tropocollagen molecules in a:
a) Parallel and aligned arrangement
b) Random and disorganized arrangement
c) Quarter-staggered alignment
d) Anti-parallel arrangement

C) Quarter-staggered alignment

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Cross-linking in collagen fibrils involves covalent bonds formed via:
a) Glycosidic linkages between carbohydrate moieties
b) Disulfide bonds between cysteine residues
c) Reactive aldehydes derived from lysine and hydroxylysine
d) Hydrogen bonds between amino acid side chains

C) Reactive aldehydes derived from lysine and hydroxylysine

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Lysyl oxidase, an enzyme crucial in collagen cross-linking, requires which cofactor?
a) Zinc
b) Iron
c) Copper
d) Magnesium

C) Copper

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The initial intracellular product of collagen biosynthesis is:
a) Tropocollagen
b) Procollagen
c) Preprocollagen
d) Mature collagen fibril

C) Preprocollagen

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What structural feature present in procollagen aids in the formation of the triple helix?
a) Gly-X-Y repeats
b) Hydroxyproline and hydroxylysine residues
c) N- and C-terminal propeptides
d) Disulfide bonds

C) N- and C-terminal propeptides

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The conversion of procollagen to tropocollagen occurs:
a) Within the endoplasmic reticulum
b) Within the Golgi apparatus
c) In the extracellular matrix
d) Within the cytoplasm

C) Extracellular matrix

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Osteogenesis imperfecta is often caused by mutations in genes encoding which type of collagen?
a) Type II
b) Type IV c
C) Type I
d) Type IX

Type I

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A common cause of collagen disorders involves the substitution of glycine in the Gly-X-Y repeat with an amino acid having a larger R group. This typically leads to:
a) Increased collagen strength
b) Disruption of the triple helix
c) Enhanced enzyme resistance
d) Increased solubility of collagen fibers

Disruption of the triple helix

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What is the common cause of collagen disorders?

The substitution of aa for a single glycine.

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Ehlers-Danlos syndrome is a group of disorders characterized by:
a) Increased bone density
b) Decreased skin elasticity
c) Hyperextensibility of the skin and joint hypermobility
d) Impaired blood clotting

Hyperextensibility of the skin and joint hypermobility
Another symptom: abnormal tissue fragility

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Type IV Ehlers-Danlos syndrome, the most serious form, is associated with abnormalities in which collagen type?
a) Type I
b) Type III
c) Type V
d) Type XI

C) Type III

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Type I & II Ehlers-Danlos syndrome is associated with abnormalities in which collagen type?

Type V

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Osteoarthritis is often caused by mutations in genes encoding which type of collagen?
a) Type II
b) Type IV
c) Type I
d) Type IX and type II

Type II and IX

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Alport syndrome primarily affects the structure of collagen in which location?
a) Articular cartilage
b) Dermal connective tissue
c) Renal glomeruli
d) Tendons and ligaments

C) Renal glomeruli

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Alport syndrome primarily affects which collagen type?

Collagen IV

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Scurvy is a condition resulting from a deficiency in vitamin C, which directly impairs:
a) The synthesis of procollagen
b) The cleavage of propeptides from procollagen
c) The hydroxylation of proline and lysine residues in collagen
d) The cross-linking of collagen fibrils

c) The hydroxylation of proline and lysine residues in collagen

Which of the following is a major structural protein found in elastic fibers?
a) Collagen b) Fibrillin c) Elastin d) Fibronectin

Elastin

Unlike collagen, elastin does not contain: a) Glycine as a major component b) Proline residues c) Hydroxylysine residues d) Lysine residues involved in cross-linking

C) Hydroxylysine residues

The unique cross-links found in elastin are called: a) Aldol condensations b) Schiff bases c) Desmosines d) Isopeptides

Desmosines

Fibrillin-1 is a large glycoprotein that serves as a: a) Primary component of mature elastic fibers b) Scaffolding for elastin deposition in microfibrils c) Receptor for collagen on cell surfaces d) Major component of the basal lamina

B) Scaffolding for elastin deposition in microfibrils

Marfan syndrome is caused by a mutation in the gene encoding: a) Elastin b) Collagen type I c) Fibrillin-1 d) Fibronectin

C) Fibrillin -1

Which of the following is the first well-characterized adhesive protein that attaches cells to the ECM? a) Laminin b) Entactin c) Fibronectin d) Integrin

C) Fibronectin

Fibronectin is a dimer of two similar peptides linked by: a) Hydrogen bonds b) Ionic interactions c) Disulfide bonds d) Hydrophobic interactions

C) Disulfide bonds

Cell-surface receptors for fibronectin recognize a specific amino acid sequence: a) Gly-Arg-Gly-Asp b) Arg-Gly-Asp-Ser c) Pro-Hyp-Gly-Pro d) Lys-His-Arg-Lys

b) Arg-Gly-Asp-Ser

Laminin is a major adhesive protein found in: a) Tendons and ligaments b) Articular cartilage c) Basal laminae d) Bone matrix

Basal laminae

Laminin is a heterotrimer composed of: a) Three identical alpha chains b) Two alpha chains and one beta chain c) Alpha, beta, and gamma chains d) Intertwined collagen triple helices

c) Alpha, beta, and gamma chains

Entactin, also known as nidogen, primarily functions as a bridge between: a) Collagen type I and fibronectin b) Elastin and fibrillin c) Collagen type IV and laminin d) Integrins and the cytoskeleton

C) ) Collagen type IV and laminin

Integrins are transmembrane receptors that link the extracellular matrix to the: a) Nucleus b) Endoplasmic reticulum c) Internal cytoskeleton d) Golgi apparatus

Internal cytoskeleton

Integrins are composed of which subunits? a) Two identical alpha subunits b) Two identical beta subunits c) Alpha and beta subunits d) Heavy and light chains

C) Alpha and beta subunits

The increased rigidity and brittleness of aging connective tissue is partly due to: a) Decreased cross-linking of collagen b) Increased synthesis of elastin c) Increased cross-linking of collagen over time d) Reduced degradation of elastin

C) Increased cross- linking of collagen over time

Loss of both elastin and collagen in the skin contributes to which visible sign of aging? a) Increased pigmentation b) Wrinkling c) Increased sebum production d) Thickening of the epidermis

Wrinkling

Williams-Beuren syndrome is associated with deletions in a region of chromosome 7 that includes the gene for: a) Collagen type II b) Fibrillin-1 c) Elastin d) Fibronectin

Elastin (ELN gene)

The extracellular matrix (ECM) plays a role in all of the following except: a) Mechanically connecting cells b) Serving as a template for DNA replication c) Creating filters in organs like the kidney d) Providing pathways for migrating cells

b) Serving as a template for DNA replication

Which of the following properties is characteristic of collagen protein fibers? a) High solubility in aqueous solutions b) Low tensile strength c) High enzyme resistance d) Susceptibility to denaturation at physiological temperatures

c) High enzyme resistance Note- Also.. insoluble, high tensile strength

The triple helical structure is a common feature of all collagen types to some degree. Which type of collagen is completely triple-helical? a) Type IV b) Type II c) Type I d) Type IX

Type I

Hydroxylysine residues in collagen can be further modified by: a) Phosphorylation b) Glycosylation c) Sulfation d) Methylation

B) Glycosylation

The primary defect in Type VI Ehlers-Danlos syndrome involves a deficiency in: a) Procollagen peptidase b) Lysyl oxidase c) Lysyl hydroxylase d) Prolyl hydroxylase

c) Lysyl hydroxylase

The main clinical feature of Alport syndrome is: a) Excessive bruising b) Joint dislocations c) Haematuria d) Impaired wound healing

Haematuria End result - renal disease

Which of the following ECM proteins is known to act as an additional bridge between type IV collagen and laminin? a) Fibronectin b) Fibrillin c) Entactin d) Elastin

Entactin

Laminin is most abundant in which type of extracellular matrix? a) Cartilage matrix b) Bone matrix c) Basal laminae d) Tendon matrix

Basal laminae

The RGD sequence found in fibronectin and entactin is crucial for binding to: a) Heparin sulfate b) Collagen c) Integrins d) Laminin

Integrins

Tumour metastasis can be aided by the breakdown of: a) Elastin fibers b) Collagen in the ECM c) Fibrillin microfibrils d) Glycosaminoglycans

b) Collagen in the ECM

Fibronectin can bind to which of the following ECM macromolecules? a) Elastin b) Fibrillin c) Collagen d) Desmosine

Collagen

The hydrophobic segments in elastin are primarily responsible for its: a) Tensile strength b) Elastic properties c) Glycosylation sites d) Cross-linking

Elastic properties

The Ala- and Lys- a- helical segments in elastin are primarily responsible for:

Cross links between molecules

Name the monomer elastin is synthesized by.

Tropoelastin.

Ehlers Danlos Syndrome is affected by mutations in which type of Collagen?

Type V

The secondary intracellular product of collagen biosynthesis is: a) Tropocollagen b) Procollagen c) Preprocollagen d) Mature collagen fibril

Pro collagen