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Biochemistry > Chapter 7: Carbohydrates > Flashcards

Chapter 7: Carbohydrates Flashcards

1
Q

What is the formula of a Carbohydrate?

A

C_n(H2O)_n

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2
Q

What functions do carbohydrates fulfill?

A
  • Energy source and storage
  • Structural component of cell walls and exoskeletons
  • informational molecules in cell-cell signaling
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3
Q

How would you classify a carbohydrate with the following number of carbons?
- 5
- 3
- 4
- 7

A
  • Pentose
  • Triose
  • Tetrose
  • Heptose
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4
Q

Be able to know what an oligosaccharide is:

A

A carbon with more than one sugar
Ex: Disaccharide

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5
Q

How do Constitutional Isomers differ?

A

They differ in the order of attachment of atoms
Ex: Two molecules can have the same formula (C3H6O3) but they aren’t the same due to the way they are arranged

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6
Q

What are Stereoisomers? What other isomers are direct variants of them?

A

Stereoisomers differ in spatial arrangement but are in the same order as each other. The two variants are Enantiomers (Nonsuperimpossable mirror images, D vs L formation) and Diastereomers (Isomers that are not mirror images)

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7
Q

What are epimers and anomers?

A

Epimers are isomers that differ at one of several asymmetric carbon atoms.

Anomers are isomers that differ at a new asymmetric carbon atom formed on ring closure (α vs ß formation)

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8
Q

What is a Ketose? What is an Aldose? How can you change between them?

A

Ketoses are carbohydrates with Ketone functionality, and Aldoses are carbohydrates with Aldehyde Functionality. You can swap between them by using an Enediol Intermediate.

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9
Q

How do you determine in a non-cyclic sugar if it is in D or L conformation?

A

Look at the chiral center furthest away from the carbonyl carbon. If it has the OH group on the right, it is D-formation. If the OH group is on the left, it is in the L-formation.

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10
Q

For a carbon to be chiral what requirements must it meet?

A

It must be attached to four different groups.

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11
Q

Hexose is in which conformation mostly in living organisms?

A

D-conformation

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12
Q

Can epimers also be classified as diastereomers?

A

Yes as Epimers are also not mirror images (be careful on some questions as one of the answers may be “more” correct)

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13
Q

How can you determine the number of stereoisomers a given carbohydrate will have?

A

The # of Stereoisomers = 2^n

n = # of chiral centers

A carbohydrate with 4 chiral centers will have 2^4 stereoisomers which is 16

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14
Q

What are the common carbohydrates in Biochemistry?

A

Ribose - The Standard 5 Carbon Sugar
Hexose - The Standard 6 Carbon Sugar
Galactose - Epimer of Glucose
Mannose - Epimer of Glucose
Fructose - Ketose Form of Glucose

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15
Q

If a chiral molecule has a mirror image isomer what is that called? What if it has a non-mirror image isomer?

A

If it has a mirror image isomer, it is an enantiomer

If it has a non-mirror image isomer, it is a diastereomer

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16
Q

Aldehyde and Ketone Carbons are ________philic

A

Electrophilic

17
Q

When aldehydes are attacked by alcohols, what is formed? What about when ketones are attacked?

A

Hemiacetals

Hemiketals

18
Q

What is the name for six-membered oxygen-containing rings? What about those with five members?

A

Pyranose

Furanose

19
Q

In a cyclic carbohydrate, if the anomeric carbon has an alcohol group pointing down, which form is it in? (Alpha or Beta)

A

It is in the Alpha formation

20
Q

As temperature increases, does the equilibrium shift towards the furanose or pyranose form for cyclization?

A

Equilibrium shifts in the direction of the furanose form, and this causes the sweetness of the solution to decrease.

21
Q

What is mutarotation?

A

Mutarotation is where a carbohydrate in solution inter-converts between the linear form and four cyclic conformation

22
Q

Which sugars are reducing?

A

All sugars with a free anomeric carbon are reducing sugars. This means all monosaccharides are reducing sugars.

23
Q

How are two sugars joined?

A

They are joined via a glycosidic bond between an anomeric carbon and a hydroxyl carbon. This bond (which is an acetal) is more stable and less reactive than the hemiacetal at the second monomer.

24
Q

What are the two types of glycosidic bonds?

A

O-glycosidic bond and N-glycosidic bond

25
Q

What are disaccharides linked by?

A

O-Glycosidic Bonds

26
Q

Which enzymes are responsible for linking monosaccharides?

A

Glycosyltransferases

27
Q

What happens when two sugar molecules are joined together via their anomeric carbons?

A

They become a nonreducing sugar

28
Q

What is the difference between homopolysaccharides and heteropolysaccharides?

A

Homopolysaccharides are all made up of the same monomer subunit while heteropolysaccharides are made up of multiple monomer subunits.

29
Q

Do polysaccharides have a defined molecular weight? Why?

A

No, because they do not have a template to follow to make them

Biochemistry (11 decks)

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