anomeric carbon

1

anomeric carbon

2

3

4

Flat ring (Haworth projection) just gives the relative positions of the H and OH at each carbon, one is “above” the other. But it does not tell the positions of the groups relative to the plane of the ring (up, down or out)

Relationship between Haworth (flat ring) depiction and chair-form

5Polymers are built by removing a molecule of water

between them, known as dehydration, or condensation.

R-OH + HO-R

→ R-O-R + HOHThis process does not happen by itself

(It is NOT like glucose ring formation)

Rather, like virtually all of the reactions in a cell,

it requires the aid of a CATALYST

Dimer formation

6AND: Polymers are broken down by the reverse process, ADDING a molecule of water between them, known as

DIMER HYDROLYSIS

R-O-R + HOH→ R-OH + HO-R

This process does not happen by itself

Rather, like virtually all of the reaction in a cell, it requires the aid of a CATALYST

7

CHOH2

12

3

45

B eta-g lucose

Building a polymer from glucose

8

CHOH2

12

3

45

B eta-g lucose

CHOH2

12

3

45

B eta-g lucose

9

Glycosidic bondAnomeric carbon is always one partner

Beta conformation is now locked in here But not here

C4 = equatorial out (always in glucose)

C1 = equatorial out (in beta glucose)

The two glucose molecules are connected in a ~straight line in cellobose

O

H

H

H

CHOH2HO

HO HO

HH

4

O

H

H

H

CHOH2

HO

OHHO

HH

4

Beta-glucose residue “Beta”-glucose residue

Cellobiosewith right-hand glucose shown as beta

10

Glycosidic bondAnomeric carbon is always one partner

Alpha conformation of –OH is now locked in here

But not here

C4 = equatorial out (always in glucose)

C1 = axial down (in alpha glucose)

O

H

H

H

CHOH2HO

HO HO

H

H

4

O

H

H

H

CHOH2

HO

OH

HO

H

H

4

Alpha-glucose residue

“Beta”-glucose residue

Maltosewith right-hand glucose shown as beta

The two glucose molecules are connected with an angle between them in maltose

11

One is forced to draw strange “elbows” when depicting disaccharides using theHaworth projections. Such elbows do not exist in reality.

(here the C1 OH is “above” and the C4 OH is “below”Whereas we just saw in actuality that they are both equatorial in beta glucose)

Equatorial bond is above the H

Equatorial bond is below the H

12

Tinker toys

Starch or glycogen chain

down

out

H

H

CelluloseTinker toys

13

4-1

4-1

4-1

4-1

4-14-1

6-14-1 4-1

4-14-1

Branches at carbon 6 hydroxylBranching compact structureStarch or glycogen granules, A storage form of glucose for energy

Branching in starch

C6

14NucleusCytoplasm

Organelles

Starch granules

15

or glycogen chain

down

out

H

H

Cellulose

16Cellulose

Cell wall of green algae

17anomeric carbon

anomeric carbon

fructose riboseglucose glucose

From handout 2-6

18

More sugars:

Mannose C6H12O6 (different arrangement of OH’s and H’s)

Galactose C6H12O6 (different arrangement of OH’s and H’s)

Deoxyribose C5H10O4 (like ribose but C2’s OH substituted by an H)

More disaccharides

Lactose = b-1-glucose to C4 of galactose (milk sugar)

Sucrose = b-2-fructose to C1- a-1-glucose (table sugar, cane sugar)

19

(Insect exoskeleton)

(Bacterial cell walls)Metabolic intermediate

20Lipids

• Soluble in organic solvents (like octane, a hydrocarbon)

• Heterogeneous class of structures

• Not very polymer-like (in terms of covalently bonded structures)

21

A steroid

(Abbreviation convention: Always 4 bonds to carbon. Bonds to H not shown.)

22

A fatty acid

Fats

23

A trigyceride (fat)

Ester (functional group, acid + alcohol)}

24

trans

cis

cis

C C| |

HH

HH| |

| || C C| |

HH|| ||

- 2H

X

Free rotation about single bonds

No free rotationabout double bonds

C C|

|H

H

||

|

|

X

trans

cis

Solid fats

Oils

Effect of fatty acid structure on physical properties

25

Fatglobule

Nucleus

Adipocyte (fat storage cell)

26

R=H: a phosphoester(phosphoric acid + alcohol)

In this case: phosphatidic acid

}Handout 2-10

27

[HO]

[HO]

Handout 2-10

28

R=another alcohol:A phospho-diester

}HO

HO

Handout 2-10

HO –CH2CH2N+H3

(alcohol = ethanolamine)

29HOH

HOH

Phosphate head

2 fatty acid tails each

Biological membranes are phospholipid bilayers

30

Incidentally, note the functional groups we have met so far:

HydroxylAmineAmideCarboxylCarbonylAldehydeKetoneEster: Carboxylic acid ester

Phosphoester

And:

Glycosidic bondsC=C double bonds (cis and trans)

31

Amino acids (the monomer of proteins)

PROTEINS

32

At pH 7, ,most amino acids are zwitterions(charged but electrically neutral)

33

34

+OH- ( -H+)

+H+

Net charge

50-50 charged-uncharged at ~ pH9 (=the pK)50-50 charged-uncharged at ~ pH2.5 (=the pK)

35

Numbering (lettering) amino acids

Alpha-carbon

Alpha-carboxyl (attached to the α-carbon)Alpha-amino

β

γδ

ε

ε-amino group

36Amino acid examples

Molecular weights 75 – 203

(MW)

Glycine (gly) Side chain = H Smallest (75)

Aspartic acid

(asp, aspartate) One – charge

β-carboxyl:

-CH2-COOH

Tryptophan (trp) 5+6 membered rings

Hydrophobic, largest (203)

Lysine (lys) One + charge ε-amino

Alanine (ala) One carbon (methyl group)

-CH3

Arginine

(arg, guanido group)

One + charge -(NH-C (NH2)NH2)+,

37

38Shown uncharged (as on exams)

39

40

Amino acids in 3 dimensions

• Asymmetric carbon (4 different groups attached)

• Stereoisomers• Rotate polarized light• Optical isomers • Non-superimposable• Mirror images

• L and D forms

From Purves text

41

Mannose

42

Condensation of amino acids to form a polypeptide(must be catalyzed)

43

Parts of a polypeptide chain

44

Handout 3-3

(Without showing the R-groups)

The backbone is monotonous It is the side chains that provide the variety

The backbone is monotonous

45

“Polypeptides” vs. “proteins”

• Polypeptide = amino acids connected in a linear chain (polymer)

• Protein = a polypeptide or several associated polypeptides (discussed later)

• Often used synonymously

• Peptide (as opposed to polypeptide) is smaller, even 2 AAs (dipeptide)