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Bichem > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Carbs overview

A
  • most abundant organic molecules in nature
  • wide range of functions
    - major energy source
    - stores energy
    - cell membrane component for intracellular com.
    - only on outer surface of lipid bi layers
  • structural component
    - in cell walls
    - exoskeleton
    - fibrous cellulose of plant walls
  • (CH2O)n—-ratio C:H:O= 1:2:1
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2
Q

Types of carbohydrates

A
  • based on number of monomers
  • monosaccharides (1 unit)
  • Disaccharides (2 monosaccharide units)
  • oligosaccharides(3-10 monosaccharide units)
  • polysaccharides (more than 10)
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3
Q

Monosaccharide classification

A
  1. according to the number of carbons they contain

2. according to the type of their most oxidized functional group (Aldoses or Ketoses)

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4
Q

Structural Isomers

A

-compounds that have the same chemical formula but different structures (glucose, fructose, mannose)

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5
Q

Epimers

A
  • compounds that differ in configuration around only ONE SPECIFIC CARBON ATOM
  • glucose and galactose
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6
Q

Enantiomers

A
  • pairs of structures that are mirror images to each other.

- D-glucose (naturally occurs in human body) and L-glucose

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7
Q

Monosaccharide cyclization

A
  • 99% of monosaccharide with 5 or more carbons exist in a ring
  • keto or aldehyde group reacts with an alcohol group on same the same sugar
  • creates an anomeric carbon that can exist in alpha or beta form (alpha=hydroxyl group on same sideas O)(beta=opposite side)
  • ENZYMES ARE SPECIFIC TO ONE OF THE ANOMERIC FORMS
  • RINGS ARE MORE STABLE
  • RINGS AND NON RINGS ARE IN EQUILIBRIUM
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8
Q

Disaccharide types of bonds

A

-bonds that link monosaccharides by GLYCOSIDIC bonds.

Naming: geek letter for alpha or beta, numbering is according to connected carbon

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9
Q

Lactose

A

glucose + galactose (Beta 1-4)

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10
Q

Sucrose

A

glucose +fructose (Alpha 1-2)

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11
Q

Maltose

A

Glucose+ glucose (Alpha 1-4)

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12
Q

Reducing Sugar

A
  • all monosaccharides are, but not all disaccharides
  • if the OH group on the anomeric carbon in a ring is NOT linked to another compound by a glycosidic bond, the ring can open
  • then it can act as a reducing agent
  • when they open, more open, and react and open more.
  • you should not find reducing sugars in urine
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13
Q

Glycogen

A
  • highly branched polymer of glucose
  • alpha 1-4 and 1-6 linkage
  • energy storage in liver and muscle cells
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14
Q

Amylose

A
  • form of starch in plants

- unbranched alpha 1-4 glycosidic linkage

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15
Q

Amylopectin

A
  • form of starch in plants
  • branched BUT NOT AS BRANCHED AS GLYCOGEN
  • alpha 1-4 and 1-6 linkage
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16
Q

Cellulose

A
  • unbranched
  • humans can’t digest
  • Beta 1-4 linkage
17
Q

Complex carbohydrates

A

-carbohydrates attached to noncarbohydrate structures
noncarbo structure examples
purines and pyrimidines
Aromatic rings
Proteins
Lipids

18
Q

Complex carbohydrate bonds

A

N-glycosidic link and O-glycosidic link

19
Q

Glycoside hydrolyses

A
  • enzyme for complex carbo digestion

- breaks down glycolytic bonds

20
Q

Salivary alpha amylase

A

Role-breaks large insoluble cab molecules into smaller ones
Specificity-hydrolysis of alpha 1-4 bonds ONLY
Substrates-any carb with 1-4 bonds, starch, glycogen, maltose
Products: short branched and unbranched oligosaccharides
pH-7
MOUTH

21
Q

Pancreatic alpha amylase

A

Role-break down carbs
Specificity- hydrolysis of alpha 1-4 ONLY
substrates-things with 1-4 bonds, starch, glycogen
Products-unbranched oligosaccharides and disaccharides
pH-7

INTESTINAL LUMEN

22
Q

Digestion in the mucosal cells

A
  • all enzymes are transmembrane proteins on luminal surface
  • sucrase-1 protein with 2 subunits. cleave 1-2 in sucrose and 1-6 in isomaltose
  • maltase-1 protein with 2 activities. cleave 1-4 in maltose and 1-4 in dextrins
  • Lactase- cleave 1-4 bonds in lactose
  • Trehalase-cleaves 1-1 bonds in trehalase (mushrooms)
23
Q

Absorption of monosaccharides

A
  • monosaccharides only are sugars absorbed

- absorbed in duodenum and upper jejunum

24
Q

Mechanism of monoasccharide absorption

A

from lumen into cells

  • transporter proteins are highly specific for each monosaccharide
  • sodium-dependent (SGLT-1)-glucose and galactose active transport
  • sodium independent(GLUT-5)-fructose passive transport

From cells into the portal circulation

  • GLUT-2
  • passive transport
  • galactose, glucose, fructose
25
Q

Abnormal degradation of disaccharides

A
  • disaccharides present in large intestines
  • cause osmotic imbalance
  • act as substrates for the intestinal microbiota
  • measure H2 gas in breath to determine amount of carbs not absorbed by the body
26
Q

Lactase Deficiency

A
  • lactose intolerance
  • you don’t have lactase
  • congenital deficiency is rare
  • avoid milk, dumbass
27
Q

Sucrase-isomaltase complex deficiency

A
  • sucrose intolerance
  • autosomal recessive disorder
  • more common in europeans
  • avoid sucrose/ take replacement enzymes
  • do a tolerance test with individual disaccharides

Bichem (9 decks)

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