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CHEM 441A+B > Chapter 13: Carbohydrate Structure and Function > Flashcards

Chapter 13: Carbohydrate Structure and Function Flashcards

1
Q

Define Oligosaccharides, polysaccharides, glycoproteins, and proteoglycans.

A

Oligosaccharides:
- Basic sugars that range from 3-20 unbrached and branched sugar residues
Ex. Human milk

Polysaccharides:
- Homo/hetero-polysaccharides, linear, or branched. They are extremely large and serve as structure and fuel for cells
Ex. Starch or Glycogen

Glycoproteins:
- Macromolecules that consist of proteins and sugars used in insertion, secretion, and are targeted by organelle

Proteoglycans:
- Macromoluecule consisting of carbohydrates and found in the matrix of animals or cell wall of bacteria

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2
Q

List the repeating units and glycosidic linkage for polysaccharide.

A

Alpha1->4 linkage and Alpha 1->6 linkage when branching from amylose to glycogen

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3
Q

Describe the two types of glycosidic linkages in glycoconjugates and which amino acids are they linked to.

A
  • There is N linkage and O linkage
  • N linkage occurs through the amine N of Asn (requires Asn-X-Ser/Thr)
  • O linkage occurs through O of Ser or Thr
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4
Q

Why are some blood groups compatible while others are not?

A

Because certain blood types have antibodies in the plasma or antigens on the RBC that means the blood will attack itself if they are not compatible

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5
Q

Describe the composition of peptidoglycan. How antibiotics target it, and the mechanism bacteria use to acquire antibiotic resistance.

A
  • In cell wall of bacteria, composed of GlcNAc and MurNAc(beta1-4) tethered together by peptides
  • Penecillin stops transpeptidase which synthesizes the cell wall. Forms suicide inhibitor bt Ser in Transpeptidase and carbonyl C in Penecillin
  • Bacteria were able to resist penecillin by cleaving the beta-lactam ring
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6
Q

What does an aldose look like?

A
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7
Q

What does a ketose look like?

A
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8
Q

What is the formula for carbohydrates?

A

Cn(H2O)n where N >or= 3

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9
Q

What is the function of carbohydrates?

A
  • Energy source
  • Structural component of cell walls and exoskeleton
  • Informational molecules in cell-cell signaling
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10
Q

What is an oligosaccharide?

A
  • A sugar that ranges from 3-20 unbrached and branched sugar residues

Ex. Human milk derived from lactose
(Lacto-N-tetraose)
(Lacto-N-fucopentaose-1)

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11
Q

How does human milk benefit an infants intestinal tract?

A
  • Prebiotic oligosaccharides (Lacto-N-tetraose) can serve as a growth advantage for bifidobacteria among intestinal bacteria
  • Lacto-N-fucopentaose 1 will bind to receptors on intestinal cells which blocks pathogen bacteria from being able to bind
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12
Q

Why can’t humans digest plant oligosaccharides?

A
  • Humans lack α-galactosidase enzyme needed to hydrolyze the α-1,6 glycosidic bond

Ex. Raffinose, Stachyose, Verbascose

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13
Q

What is beano?

A
  • A preparation of α-galactosidase that can aid in digestion of Oligosaccharides which releases galactose and sucrose
  • Sucrose –Sucrase–> glucose/fructose (in small intestine)
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14
Q

What is a polysaccharide’s structure like?

A

Structure:
Homopolysaccharides, heteropolysacchrides,linear, branched

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15
Q

What is the function of polysaccharides?

A
  • Structural element
    • Cellulose and Chitin
  • Storage of monosaccharides as fuel
    • Starch in plants and glycogen in animals
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16
Q

What is cellulose?

A

An unbranching homopolysaccharide consisting of ~1000 repeating units of disaccharide cellobiose
- Linkage by Beta1- 4 glycosidic bonds
- H bonds b/t cellulose strands
- Component of cell wall
- Most abundant polysaccharide in nature
Ex. Cotton

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17
Q

What is Roughage? What is cellulase?

A
  • Roughage is plant material high in cellulose and it passes through the digestive system without being digested
  • Cellulase is what allows fungi bacteria and protozoa to use wood as a food source
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18
Q

What is chitin?

A

-Linear homopolysaccharide of N-acetyl Glucosamine (contains beta-1,4 glycosidic bonds)
- Found in insects and crustaceans
- Provides strong body frame due to H bonds within polysaccharides

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19
Q

What is starch

A
  • Main storage polysaccharide in plants
  • Two forms:
    • Amylose, linear polymer ~100 α1-4 linked Glc unit
    • Amylopectin α1-4 linked Glc polymer with α1-6 branching every 15-30 residues
  • Starch is important in animal diet because it can be hydrolized by amylase which cleaves α1-4 glycosidic bonds
20
Q

What is the difference between amylose and amylopectin?

A

Amylose:
- Linear
- 100 units long
- α1-4 glycosidic bond

Amylopectin:
- Branches every 15-30 residues
- α1-4 glycosidic bond

21
Q

What is glycogen?

A
  • Branched Homopolysaccharide of glucose
  • Heavily branched
  • Forms monomer α1-4 linked chains
  • Branch points with α1-6 every 8-12 residues
  • Very large
  • Main storage of polysaccharides in animals (abundant in liver 7-10% weight)
22
Q

What kind of link does amylose form?

A

α1-4 glycosidic linkage

23
Q

How do amylopectin and glycogen bond?

A

α1-6 glycosidic bond in branching amylopectin and glycogen

24
Q

What is a granule?

A
  • Contain enzymes that synthesize and degrade glycogen and starch
25
Q

Why is there many branching points in glycogen and starch?

A

-Glycogen and amylopectin have only one reducing end and many non reducing ends
- Many non reducing ends allows for enzyme processing to occur quickly

26
Q

What is the advantage of storing glucose as starch or glycogen?

A
  • Greatly reduces osmotic pressure from storing it as a monomer
    - Osmotic pressure is proportional to the number of solute molecules in a given volume
27
Q

What is a glycoconjugate?

A
  • Glycoproteins, Proteoglycans, and Glycolipids
  • Important for cell adhesion, molecule recognition, immune response, cell signaling, and tissue development
28
Q

What is a glycoprotein?

A
  • Bulk of macromolecules consist of proteins
  • Transported by membrane vesicle to the plasma membrane
  • Others targeted to cell organelles such as mitochondria or peroxisomes
  • 50% of all human proteins are glycoproteins
29
Q

What are glycosyltransferases?

A

A glycoprotein that covalently links glycans to proteins and lipids

30
Q

What are Glycosidases?

A

A glycoprotein that removes glycans through hydrolysis

31
Q

What is a proteoglycan

A
  • Bulk of macromolecules consist of carbohydrates
  • Found in extra cellular matrix in humans and cell wall in bacteria
32
Q

What are Lectins?

A
  • Glycan proteins that recognize glycan groups on glycoconjugates which play a role in cell signaling and immunity
33
Q

What is CFG notation?

A

A representation of glycoconjugates that simplifies the glycan groups by showing sugar residues as shapes and colors bound to an amino acid

34
Q

Where do proteins attach to glycans?

A

Proteins can attach to either N or O through a process called N-/O-linked glycosylation by attaching to the first carbon

35
Q

What is N-linked glycosylation?

A
  • When the glycan and polypeptide chain bind through an N linked GlcNAc
  • Occurs through Amide N of Asn
  • Prefered consensus via sequence Asn-x-Ser/Thr where X is not proline
36
Q

What is O-linked glycosylation?

A
  • When the glycan and polypeptide chain bind through an O linked GalNAc
    -Occurs through O of Ser or Thr
  • Does not have preferred sequence
  • Often called mucins- protect epithelial cells in Intestinal, urinary, and respiratory
37
Q

What is the difference between the 4 blood types?

A
  • The blood types are determined by the expression of one,both, or neither of the two enzymes α-1,3-N-acetylgalactosaminyltransferase (GTA) or α-1,3-galactosyltransferase (GTB)
38
Q

What enzymes are responsible for blood group expression?

A

Type O:
- Neither GTA or GTB

Type A:
- GTA

Type B:
- GTB

Type AB:
- GTA and GTB

39
Q

What blood transfusions can occur to blood type A

A

RBC acceptor of:
- O, A

Plasma acceptor of:
- A, AB

40
Q

What blood transfusions can occur to blood type B

A

RBC acceptor of:
- O,B

Plasma acceptor of:
- B, AB

41
Q

What blood transfusions can occur to blood type AB

A

RBC acceptor of:
- O, A, B, AB

Plasma acceptor of:
- AB

42
Q

What blood transfusions can occur to blood type O

A

RBC acceptor of:
- O

Plasma acceptor of:
- O, A, B, AB

43
Q

What is peptodoglycan?

A
  • Component of bacterial cell wall
  • Protects against osmotic changes
  • Linear chains of beta1-4linked MurNAc and GlcNAc tethered by short peptides
44
Q

What is penicillin?

A
  • Blocks bacterial cell wall synthesis by inhibiting transpeptidase
  • Forms suicide inhibitor b/t Ser and Carbonyl C
45
Q

How do bacteria develop resistance to antibiotics

A
  • Penecillin-resistant bacteria express enzyme β-lactamase,
    which inactivates penicillin by cleaving the β-lactam ring
46
Q

What is methicillin?

A
  • Blocks transpeptidase without being a substrate for β-lactamase
47
Q

What is MRSA?

A

A bacterial strain that expresses a variant of transpeptidase that cannot be inhibited by antibiotics

CHEM 441A+B (22 decks)

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