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Biochemistry, genetics, and metabolism > intro to carbs > Flashcards

intro to carbs Flashcards

1
Q

What is the most abundant molecule in nature?

A

carbohydrates

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2
Q

function of carbs in humans

A
  • significant fraction of dietary calories
  • major energy source
  • storage form of energy (glycogen)
  • cell membrane components that mediate some forms of intercellular communication and retain water
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3
Q

structural component of many organisms

A
  • cell walls of bacteria
  • exoskeleton of insects (chitin)
  • fibrous cellulose of plant cell wall (indigestible)
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4
Q

stoichiometric formula

A

(CH2O)n

consists of carbon and water in ratio of C:H:O= 1:2:1

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5
Q

monosaccharides

A
  • 1 unit
  • simple sugars
  • glucose and fructose
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6
Q

disaccharides

A

-2 monosaccharide units

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7
Q

oligosaccharides

A

3-10 monosaccharide units

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8
Q

polysaccharides

A

more than 10 monosaccharide units

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9
Q

monosaccharide classification

A
  1. according to the number of carbons they contain

2. according to the type of there most oxidized functional group

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10
Q

isomers

A

compounds that have the same chemical formula but different structures

gluctose, fructose, mannose, and galactose are all structural isomers

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11
Q

epimers

A

compounds that differ in the configuration around only one specific carbon atom

glucose and galactose are C-4 epimers
glucose and mannose are C-2

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12
Q

enantiomers

A

pairs of structures that are mirror image to each other

D-glucose and L-glucose

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13
Q

D-glucose

A

found in nature

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14
Q

L-glucose

A

cannot be metabolized

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15
Q

monosaccharides: cyclization

A

> 99% of monosaccharides with 5 or more carbons exist as a ring, in which the aldehyde or kept group has reacted with an alcohol group of the same sugar

creates an anemic carbon (isomer) that can exist in either alpha or beta form

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16
Q

pyranose

A

6 membered ring with 5 carbons and one oxygen

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17
Q

Furanose

A

5 membered ring with 4 carbons and one oxygen

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18
Q

enzyme specificity of anomeric monosaccharides

A

they are specific to one of the anemic forms

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19
Q

Glycosidic bonds

A

bonds that link sugars

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20
Q

Beta gycosidic

A

beta(1-4)

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21
Q

alpha glycosidic

A

alpha(1-4)

alpha (1-6)

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22
Q

lactose

A

glucose + galactose

Beta (1-4)

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23
Q

Sucrose

A

glucose + fructose

alpha (1-2)

24
Q

Maltose

A

glucose + glucose

alpha (1-4)

25
When can the ring on a cyclic mono-disaccharide open?
if the OH group on the anemic carbon of a cyclized sugar is NOT linked to another compound by a glycosidic bond
26
reducing agent
the sugar can act as a reducing agent once the ring opens
27
What can be a reducing sugar?
all monosaccharides but not all disaccharides
28
positive urine test for reducing sugars
indicative of underlying pathology
29
glycogen
highly branched polymer of glucose, alpha 1-4 and alpha 1-6 linkages major energy storage in animal (liver and muscle cells)
30
amylose
polymer of glucose in plants | unbranched; alpha 1-4 glycosidic linkages
31
Amylopectin
polymer of glucose in plants branched; alpha 1-4 and alpha 1-6 glycosidic linkages a little less branched than glycogen
32
cellulose
unbranched glucose polymer in plants beta 1-4 glycosidic linkages humans can't digest
33
complex carbs
carbs attached to non-carb structures such as - purines and pyramidines - aromatic rings (steroids) - proteins (glycoproteins) - lipids (glycolipids)
34
types of bonds by which a sugar may be attached to a non-carb group
- NH2 group = N-glycosidic link (N-linked) | - OH group = O-glycosidic link (O-linked)
35
Where do carbs get digested?
- mouth - intestinal lumen - mucosal lining of the upper jejunum
36
What digestive enzymes break down carbs?
glycoside hydrolases (glycosidases), use a molecule of water
37
Mouth enzymes
salivary alpha-amylase
38
intestinal lumen enzymes
pancreatic alpha-amylase
39
enzyme of the mucosal lining of the upper jejunum
isomaltase, galactosidase, trehalase
40
what two enzymes act the same but are secreted from different tissues?
salivary alpha-amylase and pancreatic alpha-amylase
41
role of salivary alpha amylase
breaks large insoluble carbs into smaller soluble ones
42
specificity of salivary alpha amylase
hydrolysis of alpha 1-4 bonds ONLY
43
substrates of salivary alpha amylase
any carb with alpha 1-4 bonds (starch, glycogen, maltose)
44
salivary alpha amylase products
short branched and unbranched oligosaccharides (dextrins)
45
salivary alpha amylase pH optimum
7. 0 | - inactivated by the acidic pH in stomach within 20 minutes
46
pancreatic alpha amylase role
continues to break down carb molecules into smaller soluble ones
47
pancreatic alpha amylase specificity
hydrolysis of alpha 1-4 bonds ONLY
48
pancreatic alpha amylase substrates
any carb with alpha 1-4 bonds (starch, glycogen, maltose, and smaller dextrin)
49
pancreatic alpha amylase product
shorter branched and unbranched oligosaccharides (dextrin) and disaccharides
50
pancreatic alpha amylase pH optimum
7.0
51
pancreatic alpha amylase and pathology
plasma levels of either pancreatic amylase or total amylase are used as a diagnostic marker for pancreatitis, should not be found in plasma
52
final digestions in the mucosal cells
all enzymes are transmembrane proteins of the brush border on luminal surface of the intestinal mucosal cells
53
sucrase/isomaltase (SI)
1 protein-2 subunits with enzymatic activities - cleaves alpha 1-2 bonds in sucrose - alpha 1-6 bonds (branches) in isolates
54
maltase-glucoamylase (MGA)
1 protein-2 enzymatic activities - cleaves alpha 1-4 bonds in maltose/maltotriose (maltase activity) - alpha 1-4 bonds in dextrins (glucoamylase)
55
lactase
beta 1-4 bonds in lactose (milk sugar) | high expression in infants and gradual decrease with age
56
trehalase
alpha 1-1 bonds in therapies (mushrooms and fungi)
57
What kind of sugars get absorbed?
ONLY MONOSACCHARIDES. in the upper jejunum and duodenum

Biochemistry, genetics, and metabolism (11 decks)

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