Lipids and Carbohydrates 4

Question 1

What are reducing sugars?

Answer 1

Glucose and other sugars that can reduce cupric ion Some oxidants such as cupric ion (Cu 2+) can oxidize the carbonyl carbon of sugars to the corresponding acids

Question 2

What are non reducing sugars?

Answer 2

Sugars that don’t react with oxidants

Question 3

What is an anomeric carbon?

Answer 3

The only carbon attached to 2 oxygen atoms that is reactive

Question 4

Name the properties of the anomeric carbon

Answer 4

electrophilic most reactions involving ring forms of sugars take place at this position

Question 5

What are glycosides?

Answer 5

Question 6

What is glycosidic bond?

Answer 6

C-O

Question 7

What is a glycosylic bond?

Answer 7

C-N

Question 8

What kind of sugar does glycosidic bonds make?

Answer 8

Non Reducing sugars but only the open chain forms of the sugar can undergo oxidation by cupric ions

Question 9

Why do glycosidic bonds of sugars become non reducing sugars?

Answer 9

If the anomeric carbon is associated in a glycosidic bond, the sugar can’t open from its ring form to become a linear form

Question 10

What is disaccharide?

Answer 10

2 monosaccharides formed through a glycosidic bond

Question 11

How does a dissacharide formed?

Answer 11

When the anomeric carbon of one sugar (electrophile) reacts with hydroxyl group (nucleophile) of the other

Question 12

What does ß mean in terms of OH orientation?

Answer 12

The OH group on the anomeric carbon is facing “up”

Question 13

What does alpha mean in terms of OH group on the anomeric carbon?

Answer 13

It means that the OH group on the anomeric carbon is facing down

Question 14

How can you make a reducing sugar out of a disaccharide?

Answer 14

If the anomeric C atom of the one sugar and the anomeric OH group of glucose form a glycosidic bond.

Question 15

What is mutarotation?

Answer 15

The converting of the alpha and beta OH groups on the anonomer C atom

Question 16

What is the reducing end?

Answer 16

In disaccharides and polysaccharides, the end of a chain with a free anomeric carbon (not involved in a glycosdic bond)

Question 17

Why are polysaccharides often branched?

Answer 17

Sugars have several OH groups which can act as the nucleophile in forming a glycosidic bond

Question 18

How does polysaccharides differ from each other?

Answer 18

linked to different sugars, length of chains, type of bonds linking units and degree of branching

Question 19

What are the two types of polysccharides?

Answer 19

Homopolysccharides and heteropolysaccharides

Question 20

What are homopolysccharides?

Answer 20

Made from a single type of sugar monomer

Question 21

What are heteropolysaccharides?

Answer 21

Made from two or more kinds of sugar subunits

Question 22

Who first isolated DNA?

Answer 22

Friedrich Miescher called it “Nuclein”

Question 23

What is a nucleotide consist of?

Answer 23

A sugar, a base and a phosphate group

Question 24

What is the sugar phosphate backbone?

Answer 24

The sugars linked together by phosphates form the backbone of nucleic acids

Question 25

What kind of pentoses do nucleic acids have?

Answer 25

2 kinds of pentoses - D-aldoses

Question 26

What are pyrimidines?

Answer 26

1 ring bases of nucleic acids

Question 27

What are purines?

Answer 27

2 ring bases of nucleic acids

Question 28

What is a heterocycle?

Answer 28

Aromatic rings containing non carbon atoms such as N, O and S

Question 29

What are tautomeric forms?

Answer 29

Isomers that differe by the shift of a H atom and a double bond

Question 30

Which are Purine bases?

Answer 30

Adenine and Guanine

Question 31

Which are pyrimidine bases?

Answer 31

Thymine and Cytosine

Question 32

What is a nucleoside?

Answer 32

A sugar and a base WITHOUT the phosphate

Question 33

How is a phosphodiester linkage formed?

Answer 33

A phosphate group bridges between the 5’ OH of one nucleotide unit and the 3’ OH of anohter

Question 34

What is the charge of phosphate groups in the sugar phosphate backbone?

Answer 34

It is completely ionized (in ion form) and negatively charged at pH 7.

Question 35

What is different about RNA?

Answer 35

RNA can be rapidly hyrolyzed under alkaline conditions because of the 2’ hydroxyl of RNA which is absent from DNA

Question 36

What is Chargaff’s rule?

Answer 36

A=T and G=C

Question 37

What is Rosalind Franklin’s contribution to DNA?

Answer 37

She used X-ray diffraction to show that DNA molecules are helical and that they had priodocities along the long axis, a primry one of 3.4 A and a secondary one of 34 A.