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Biochem 2 (CHEM 441B) > Ch. 13 > Flashcards

Ch. 13 Flashcards

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1
Q

What are glycans?

A

Synonym for carbohydrate
- Class of molecules with the formula (CH2O)n where n is greater than 2

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2
Q

What is glycobiology?

A

Study of the biological functions of glycans

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3
Q

What are the 3 major groups of carbohydrates?

A
  1. Simple sugars
  2. Polysaccharides
  3. Glycoconjugates
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4
Q

What are simple sugars?

A

Monosaccharides, disaccharides, and oligosaccharides

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5
Q

What do simple sugars often function as?

A

Metabolic intermediates in energy conversion pathways

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6
Q

What are polysaccharides?

A

Glucose homopolymers or disaccharide heteropolymers
- 1 of the 2 sugars is a hexosamine

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7
Q

What are glycoconjugates?

A

Protein or lipid with covalently linked glycans
- Role in cellular communication

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8
Q

What do glycoconjugates have a role in?

A

Cellular communication

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9
Q

What are glycotransferases?

A

Enzymes that catalyze the ADDITION of glycan units to proteins and lipids to form glycoconjugates

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10
Q

What are glycosidases?

A

Enzymes that catalyze that REMOVAL of glycan units from glycoconjugates

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11
Q

What are 4 the glycobiology principles?

A

Glycan…
1. Biochemistry
2. Biosynthesis
3. Diversity
4. Recognition

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12
Q

What is a glycosidic bond?

A

Bond that joins a carbohydrate to another molecule

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13
Q

What is an anomeric carbon?

A

The carbonyl carbon in the acyclic form of a carbohydrate

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14
Q

What are oligosaccharides?

A

Simple sugars that range from 3 to 20 branched and unbranched sugar residues

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15
Q

What examples of oligosaccharides?

A
  • Lacto-N-tetraose
  • Stachyose
  • Raffinose
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16
Q

How do we know that related oligosaccharides are derived from the same disaccharide?

A

Because of the biochemical characterization of oligosaccharides in human breast milk and the raffinose series of plant oligosaccharides

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17
Q

What is the common disaccharide of human breast milk oligosaccharides?

A

Lactose

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18
Q

What is the common disaccharide of raffinose-related oligosaccharides?

A

Sucrose

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19
Q

What happens when some people eat foods high in raffinose-type oligosaccharides?

A

Can lead to GI discomfort because humans don’t have the enzyme (α-galactosidase) that breaks it down

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20
Q

How do polysaccharides differ from each other?

A
  • ID of recurring monosaccharide units
  • Length of chain
  • Degree of branching
  • Type of bonds linking the units
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21
Q

What are homopolysaccharides?

A

Made of 1 type of monosaccharide

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22
Q

What are heteropolysaccharides?

A

Made of more than 1 type of monosaccharide

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23
Q

What are the storage forms of glucose?

A

Starch and glycogen

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24
Q

What does starch contain?

A

Amylose, amylopectin, and other polysaccharides

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25
Q

What is amylose?

A

An α(1⟶4) linear form of starch (unbranched)

26
Q

What is amylopectin?

A

An α(1⟶6)–branched form of starch
- it also has α(1–>4) linkages in the straight part

27
Q

Compare and contrast glycogen and amylopectin.

A

Similar structure but glycogen is more branched

28
Q

What is glycogen?

A

Storage polysaccharide in animal cells

29
Q

Where is glycogen abundant?

A

In the liver

30
Q

What are glycoproteins?

A

Major class of glycoconjugates characterized by glycans covalently linked to protein molecules

31
Q

What are glycolipids?

A

Major class of glycoconjugates characterized by glycans covalently linked to lipid molecules

32
Q

What are proteoglycans?

A

Type of protein glycoconjugate where most of the macromolecule consists of carbohydrates

TL;DR - More carb than protein

33
Q

What is peptidoglycan?

A

Bacterial proteoglycan made of peptide-linked chains of repeating hexosamines; the major component of bacterial cell walls

34
Q

What are the functions of proteoglycans?

A
  • Protein binding activites
  • Regulate signal transduction
  • Facilitate cell migration
35
Q

What are the two classes of proteoglycans?

A
  1. Cell surface
  2. Extracellular matrix
36
Q

What are N-linked oligosaccharides?

A

Linkage of short chains of glycans to the amide nitrogen atom in the side chain of asparagine in a glycoprotein

37
Q

What are O-linked oligosaccharides?

A

Linkage of short chains of glycans to the oxygen atom in the side chain of serine or threonine in a glycoprotein

38
Q

What are mucins?

A

O-linked glycoproteins that are secreted and bound to the cell surface
- Aid in maintenance of mucosal barriers around epithelial cells

39
Q

What amino acids do carbohydrates link to in glycoproteins?

A
  • Asparagine (N-linked)
  • Serine or threonine (O-linked)
40
Q

Where are oligosaccharides added to proteins in cells?

A

Added to newly synthesized proteins in the ER and are elaborated in the Golgi complex

41
Q

Why are oligosaccharides added to proteins in cells?

A
  • Destination labels
  • Increase solubility of proteins
  • Quality control
  • Negative charge cluster protects proteins from proteolytic degradation
42
Q

List biomedical examples of glycoconjugates.

A
  • Macular corneal dystrophy
  • Bacterial cell walls
  • Blood groups and glycotransferases
43
Q

What determines ABO blood types?

A

Variant glycosyltransferases

44
Q

What are ABO blood groups?

A

System for typing blood based on presence of GalNAc and/or galactose bound to O antigen of glycoproteins and glycolipids on surface of RBCs

45
Q

What is type O blood?

A

Neither GTA nor GTB enzymes present

46
Q

What is type A blood?

A

Only GTA enzyme

47
Q

What is type B blood?

A

Only GTB enzyme

48
Q

What is type AB blood?

A

Both GTA and GTB enzymes present

49
Q

What do β-lactam antibiotics target?

A

Peptidoglycan synthesis

50
Q

What is Gram-positive bacteria?

A

Have a thick peptidoglycan layer that retains the Gram stain

51
Q

What is Gram-negative bacteria?

A

Have a thin peptidoglycan layer that does not retain the Gram stain

52
Q

What color are gram-positive vs gram-negative bacteria after staining?

A

Gram-positive: dark purple
Gram-negative: pink-red

53
Q

What does the thick layer of peptidoglycan contain?

A

Lipotechoic acid (negatively charged polymer of ribitol phosphate or glycerol phosphate)
- Structural support

54
Q

Which type of bacteria has LPS?

A

Gram-negative (outer membrane)

55
Q

What is an endotoxin?

A

LPS in outer membrane of Gram-negative bacteria that becomes toxic to the host after the bacteria have lysed

56
Q

How does penicillin work?

A

Blocks bacterial cell wall biosynthesis by inhibiting the enzyme transpeptidase

57
Q

What makes some bacteria resistant to penicillin?

A

They produce an enzyme called β-lactamase, which inactivates penicllin by hydrolyzing the β-lactam ring in penicillin

58
Q

What causes macular corneal dystrophy?

A

Defect in the enzyme that sulfates keratan
- Cornea become opaque due to decreased sulfation of keratan

59
Q

What is the role of keratan sulfate?

A
  • Help maintain a hydrated environment
  • Functional role in promoting structural organization
60
Q

What is the structure of glucose?

A
61
Q

What is the structure of GlcNac?

A

Biochem 2 (CHEM 441B) (23 decks)

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