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MC Biochem 1 > Chpt 11- Carbohydrates > Flashcards

Chpt 11- Carbohydrates Flashcards

1
Q

Carbohydrates Definition

A
  • an aldehyde or ketone derivative of a polyhydroxyl compound (having more than one hydroxyl group)
  • Old def-hydrate of carbon (CH2O)n
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2
Q

Counting Saccharides

A 
Saccharide=Sugars (-ose)
3 Carbons- trios
4 Carbons- Tetrose
5 Carbons- Pentose
6 Carbons- Hexose
7 Carbons- Heptose
8 Carbons- Octose
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3
Q

Function of Carbohydrates

A
  • energy source (glucose or sucrose)
  • energy storage molecules (starch in plants, glycogen in animals
  • structural components (DNA and RNA)
  • Cell signaling molecule
  • Cell to cell recognition (Glycosylation of proteins and other biomolecules)
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4
Q

Isomer

A

Molecules with identical molecular formulas but different structural formulas

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5
Q

Enantiomer

A
  • Differ in configuration around one chiral carbon
  • mirror images
  • D or L (living systems contain D)
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6
Q

Epimer

A
  • one of two optical isomers that differ from each other only in the configuration about one asymmetric carbon aton
  • during cyclization
  • alpha or beta
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7
Q

Diasteromer

A

-one of two or more optical isomers of a component that are not enantiomers (possible due to multiple asymmetric carbons)

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8
Q

Different ways of Classifying Carbohydrates

A
  1. Classified by repeating Structural element
  2. Monosaccharides are classified as Aldose or Ketose
  3. Cyclized Monosaccharides are classified as Alpha or Beta
  4. Monosaccharides are classifies as Furanose and Pyranose
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9
Q

Classification of Carbohydrates:

Repeating Structural element

A
  • Monosaccharide (one)
  • disaccharide (two)
  • Oligosaccharide (more than 9)
  • polysaccharide (ALOT)
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10
Q

Classification of Carbohydrates:

Monosaccharides as Aldose and Ketose

A

Aldose-contains an aldehyde group

Ketose-contains a ketone group

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11
Q

D-Aldoses and D-ketoses you need to know:

A

D-Aldoses: (-ose)

1) D-Glyceraldehyde (3 Carbons)
2) D-erythrose (4 Carbons also D-ketoses)
3) D-ribose (5 Carbons and also D-ketose)
4) D-glucose (6 carbons)
5) D-mannose (6 carbons)
6) D- galactose (6 carbons)

D-Ketoses (-ulose)

1) Dihydroxyacetone (3 Carbons)
2) D-erythrulose (4 carbons also D-Aldose)
3) D-ribulose (5 carbons also D-Aldose)
4) D-fructose (6 carbons)

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12
Q

Classifying Carbohydrates:

Cyclized Monosaccharides are classified as Alpha or Beta

A

> 5 carbons cyclize into ring form
-in vivo <1% exist in linear form

Cyclization produces anomeric carbon-new chiral carbon

Alpha HYDROGEN Above
Beta HYDROGEN Below

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13
Q

Hemiacetal

A

formed by reacting aldehyde with an alcohol

5-membered ring (furanose)

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14
Q

Hemiketal

A

formed by reacting ketone with an alcohol

6 membered ring (Pyranose)

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15
Q

Classifying Carbohydrates:

Monosaccharides are classified as Furanose and Pyranose

A

Furanose- 5 membered ring
Pyranose- 6 membered ring
*Fructose can form both Furanose and Pyranose rings

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16
Q

Cyclic Conformations of 6 membered ring

A

Chair conformation is more stable than boat conformations due to steric hindrance

  • Axial-nearly perpendicular to the average plane of the ring (stick straight up or down)
  • Equatorial- atoms nearly parallel to the average plane of the ring (stick slightly up or down)
  • Furanose rings assume envelope form
  • C-2 or C-3 out of plane on the same side as C-5
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17
Q

Monosaccharides Mofications

A
  • Hydroxylation- O glycosidic bonds
  • Amine groups attach through N linked glycosidic bonds
  • Phosphorylated (PO32) ***
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18
Q

Phosphorylation of Carbohydrates

A

Key metabolic intermediates
Sugars become negatively charges (anionic)
-“Locks” the intermediates into the cell or other membrane bound compartment
-activates the intermediate

19
Q

Reducing vs NonReducing Sugars

A

Reducing sugars have a free aldehyde group or are capable of forming an aldehyde through ring opening, isomerization, or tautomerization
-some ketone groups may through tautomerization be reducing

20
Q

Tests for reducing sugars

A

Benedicts Reagent (CuSO4/Citrate)

Fehling’s Solution (CuSO4/tartrate)
-reducing sugars reduce copper (II) to copper (I). The produce, copper (I) oxidize, forms a red precipitate

Tollen’s Test (silver mirror test)
Tollen’s reagent precipitates silver metal when exposed to free aldehydes

21
Q

Glycosidic Bonds

A
  • Connects monosaccharides into: dimers, trimers, oligosaccharides, or polysaccharides
  • Condensation (dehydration) reaction
  • Two orientations: alpha or Beta
22
Q

What are the disaccharides we need to know?

A

Maltose
Lactose
Sucrose

23
Q

Maltose

A

Disaccharide
(alpha-D-glucopyranosyl-1,4-alpha-D-glucopyranose)
Glucose alpha-1,4-Glucose

Breakdown produce to glycogen/starch

24
Q

Lactose

A

Disaccharide
(B-D-galactopyranosyl-1,4-alpha-D-glucopyranose)
Galactose B-1,4-Glucose

Mammals milk sugar

25
Q

Sucrose

A

Disaccharide
(alpha-D-Glucopyranosyl-1,2-B-D-fructofuranoside)
Glucose alpha 1,2 fructose

table sugar

26
Q

Polysaccharides we need to know for class?

A

Glycogen
Starch
Cellulose

27
Q

Glycogen

A

Polysaccharide
Monomer-Glucose
Bond-connect alpha-1,4- with alpha 1,6 branches
Function-animal energy (glucose) storage and stored in liver and muscle

28
Q

Starch

A

Polysacchardie
Monomer- glucose
Bond-connected alpha-1,4 with alpha 1,6 branches
Function: Plant energy (glucose) storage

29
Q

Cellulose

A

Polysaccharide
Monomore-glucose
Bond: connected B-1,4 linear polymer of glucose
function: plant structural fiber

30
Q

Structure of Glycogen and Starch

A

Both are branched polymers of glucose connected by alpha 1,4 glycosidic bonds with alpha 1,6 branches

Glycogen has more branches than starch

31
Q

Proteoglycans

A

are glycosolated proteins that serve as joint lubricants and structural components in connective tissue

32
Q

Glycosaminoglycans

A

are the carbohydrate component of proteoglycans

-repeating disaccharides of amino sugars

33
Q

Mucopolysaccharidoses

A

diseases caused by the inability to degrade glycosaminoglycans (carbohydrate component of proteolglycans)

Skeletal deformities and reduced life expectancy

34
Q

Osteoarthritis

A

Disease caused by breakdown of proteoglycans

35
Q

Glycosyltransferases

A 
class of enzymes that catalyzes the formation of glycosidic bonds
-use sugar nucleotide intermediates

the genes for specific glycosyltransferases are inherited in the Mendelian Pattern

36
Q

ABO blood types

A

due to different carbohydrates on the surface of RCBs

O antigen group is foundation

  • contain four carbohydrates (fucose, 2 copies of Galactose, N-actetylglucosamine)
  • modified to form A and B antigens

A antigen
-added N-acteylgalactosamine

B antigen
-added galactose

37
Q

Proteins Modification in relation to carbohydrates

A

Proteins are modified by Attachment of carbohydrates

1) N linked carbohydrates are attached to the R group of asparagine
2) O linked carbohydrates are attached to the R group of Serine or Threonine

For both:
-Glycosylation sites identified by consenses sequences
Asn-X-Ser or Asn-X-Thr, where X can’t be proline

38
Q

N-linked Oligosaccharides

A

Extensive modification leads to vast array of molecular shapes

39
Q

EPO

A

Erythropoietin
Function-stimulates the production of RBCs
-Glycoprotein hormone; secreted kidney

Structure:

  • 165 amino acids
  • 3 N-linked groups
  • 1 O-linked Group

Uses:

  • Treats anemia cancer patients
  • Performance enhancement by athletes (Lance Armstrong)
40
Q

Cellular Localization:
N-linked Carbohydrates
Glycoproteins
O-linked carbohydrates

A

N-linked carbohydrates:

  • are attached/modified in thee lumen of the Endoplasmic Reticulum
  • are modified in the lumen of the golgi

Glycoproteins:
-are usually found on cell surface

O-linked carbohydrates:
-are attached in Golgi and cytoplasm

41
Q

N Linked Carbohydrates Synthesization

A

are synthesized as a performed unit and transferred to newly synthesized proteins
-assembled on a Dolichol phosphate in Lumen of ER

42
Q

Lectins:

Function and Structure

A

specific carbohydrate binging proteins

Legere (to select)
Function- cell to cell interaction
Structure: classified based on:
amino acid homology and biochemical properties

43
Q

Digestion of Carbohydrates

A

1) Mouth
Mastification mixes salivary alpha amylase with dietary starch
2) Stomach
digestion halts (inhibits alpha amylase) due to low PH
3) small intestine
-acid neutralized by bicarbonate (from pancreas)
-alpha amylase (from pancreas-continues digestion)
4) Mucosal lining of upper jejunum
-Disaccharidases, oligosaccharidases-isomaltase, maltase, sucrase
-secreted by luminal side of the brush border of intestinal mucosal cells

MC Biochem 1 (30 decks)

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