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Biochemistry > Biochem Carbs Lecture 1 > Flashcards

Biochem Carbs Lecture 1 Flashcards

1
Q

Sugars, starches, and cellulose are common

These are dietary staples

This is found in the cell walls of plants and has a structural role

A

Carbohydrates

Sugars and starch

Cellulose

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2
Q

What is the general formula for carbohydrates?

A

Cn(H2O)m where n greater than or equal to 3

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3
Q

Name the 2 categories of carbohydrates

Some also contain these 3 elements

A

Polyhydroxy aldehydes or ketones

Nitrogen phosphorous and sulfur

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4
Q

For most simple sugars, m=?

therefore, the empirical formula of simple sugars is

A

m=n

(CH2O)n

C5H10O5= (CH2O)5
C6H12O6= (CH2O)6
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5
Q

These are the simple sugars, with monomer units of more complex carbohydrates

Whats the most abundant one?

A

Monosaccharides

d-glucose (dextrose)

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6
Q

Short chains of monosaccharides joined by _______ bonds, like the disaccharide sucrose (table sugar

A

Glycosidic

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7
Q

Sugar polymers that contain 20+ monosaccharide units, like cellulose

A

Polysaccharides

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8
Q

Sugars that contain an aldehyde group are

Sugars that contain a keto group are

A

Aldoses

Ketoses

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9
Q

3,4,5,6,7 carbon sugars

A

tritose (?), tetrose, pentose, hexose, heptose

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10
Q

Names can be more specific, glucose is an ______ (has an aldehyde carbonyl group and 6 carbons

A

Aldohexose

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11
Q

D or L is assigned to which carbon?

A

The penultimate carbon, the chiral carbon furtherst from the carbonyl carbon

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12
Q

The sugars with the boxes around their names in the handout are the most common in nature. They are all in __ form

A

D form

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13
Q

These are the two most common simple sugars in nature

A

D-glucose D-fructose

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14
Q

D-ribose and 2-deoxy-ribose are components of ___

A

Nucleic acids

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15
Q

Compounds among the D-aldoses and D ketoses corresponding to the same number of atoms are _____ of each other

A

Diasteriomers (non mirror images)

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16
Q

There are ______ stereoisomers where n = number of chiral centers

A

2^n

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17
Q

The aldohexoses have how many carbon centers?

Therefore, how many stereoisomers do they have?

A

4

16 (2^4)

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18
Q

In aqueous solution, aldotetroses and all monosaccharides with 5 or more carbon atoms occur predominately as ___ structures

A

Cyclic

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19
Q

In the formation of the cyclic structures of carbohydrates, the ring structures form as a result of a general reaction between alcohols and aldehydes or ketones to form ___ and ____

A

Hemiacetal, kemiketal

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20
Q

Does hemiacetal/hemiketal formation create a new chiral center?

A

Yes.

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21
Q

With the formation of a new chiral center, two stereoisomeric forms result, what are they?

A

α and β anomers

22
Q

Six membered ring structures are called _____

Five membered ring structures are called

A

Pyranoses

Furanoses

23
Q

The α and β anomers of D glucose interconvert in aqueous solution by

A

Mutarotation

24
Q

A solution of α-D-glucose and β-D-glucose forms an identical equilibrium mixture with identical __ properties

The mixture has about ____ amount of α-D-glucose and _____ of β-D-glucose

Very small amounts of what occur?

A

Chiral

1/3 α, 2/3 β

Open (linear chain) and five membered ring forms

25
Q

Which is more stable, the α or β anomer of glucose?

A

β form

26
Q

When switching between D and L forms of a sugar, do all of the chiral carbons have H and OH switch positions in the fischer projections?

A

Yes! They all do. Not just penultimate carbon

27
Q

Is the pyranose ring planar?

What conformation is it?

A

No.

Chair conformation

28
Q

The β anomer should be more stable in the chair conformation because the C-1 OH group is ___

A

Equatorial (axial in α)

29
Q

In general, substituents in the equatorial positions are less hindered ____ly by neighboring substituents

A

Sterically

30
Q

Monosaccharides can be oxidized by a relatively mild _____ agent.

What is an example of one?

The carbonyl group is oxidized to a ___ group

A

Reducing agent

Ex: Cu(2+)

carboxyl group

31
Q

Sugars like glucose that reduce metal ions are called ____ sugars

A

Reducing sugars

32
Q

_____’s reaction measures the amount of oxidizing agent reduced by a sugar. It can be used to estimate the concentration of glucose in the blood and urine (diabetes test)

What is currently used as amore sensitive measure for blood glucose levels?

A

Fehling’s Reaction

The enzyme glucose oxidase

33
Q

Disaccharides are composed of two ___ covalently linked through a ______ bond

A

monosaccharides

O-glycosidic bond

34
Q

The disaccharide is formed when the ____ OH of one sugared is replaced by the O of an OH group of another sugar

What is eliminated?

What is formed?

A

Anomeric OH group

Water (condensation reaction)

Acetal from a hemiacetal

35
Q

Acetals and ketals of sugars are called ____

A

Glycosides

36
Q
  1. To name disaccharides and oligosaccharides, give the configuration and the ___ C that joins the first monosaccharide unit to the second
  2. Name the nonreducing sugar, insert ____ and ___ to distinguish between 5 and 6 membered rings
  3. Name the second residue. If there is a third residue, describe the second glycosidic bond by the same conventions
A

Anomeric

Furano, Pyrano

37
Q

_____ is a disaccharide of α-D-glucose and β-D-fructose linked by the O from the anomeric C1 of ____ to the anomeric C2 of ____

A

Sucrose

anomeric C1 of glucose to anomeric C2 of fructose

38
Q

Since both of sucrose’s anomeric bonds are involved in glycosidic linkage, sucrose is a ____ sugar, or glycoside

Practice naming structure of sucrose in lecture (slide 16)

A

Nonreducing sugar

39
Q

Maltose is made of two ___ residues

The O-glycosidic linkage occurs between the ____ of one glucose and the ____ of the other

A

D-glucose

C1 and C4

40
Q

Maltose retains one free anomeric carbon, so it is a ______ sugar

The configuration of the anomeric carbon on the glycosidic link is

The glucose residue with the free anomeric carbon
can be

A

Reducing

α

α or β

41
Q

Maltose is (name it)

Using abbreviated nomenclature, it is

A

α-D-glucopyranosyl-(1→4)-D- glucopyranose

Glc(α 1→4)Glc

42
Q

Trehalose is the disaccharide of _____ joined through the ____ anomeric carbons of borth glucose residues

A

D-glucose

C1 anomeric carbons of both

43
Q

Is Trehalose a reducing sugar?

Where does it play a major part?

A

No (no free anomeric C1s

The circulating fluids of insects

44
Q

Most carbohydrates in nature are

This type is made of a single kind of monomer

This type contains two or more different types of monomers

Note: you don’t have to draw the polysaccharides

A

Polysaccharides

Homopolysaccharide

Heteropolysaccharide

45
Q

Polysaccharides used for energy storage are

  • -> in plants
  • –> in animals
A

Starch (in plants)

Glycogen (in animals)

46
Q

Polysaccharides used as structural elements are (in plants and animals)

A

Cellulose (in plants

Chitin and Detran (in animals)

47
Q

This homopolysaccharide is amixture of amylose and amylopectin,

Amylose and amylopectin are polysaccharides of D-glucose joined by α or β ______ and α or β ______ linkages?

A

Starch

α 1→4 and α1→6 linkages

48
Q

This homopolysaccharide is also a polymer of D-glucose, but it is more extensively branched and more compact than starch

A

Glycogen

49
Q

This homopolysaccharide is a polysaccharide of D glucose joined by α or β ____ linkages?

A

β 1→4 linkages

50
Q

Glycogen and starch ingested in the diet are hydrolyzed by ________,

They are enzymes in saliva and intestines that break ___ linkages

A

α-amylases

α1→4 linkages

51
Q

In contrast to glycogen and starch, cellulose is not a digestible food source for people because they do not have enzymes to hydrolyze the ____ linkages between glucose units in cellulose

A

β 1→4

Biochemistry (27 decks)

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