1 Macromolecule class #1: Polysaccharides Monomer = sugars Sugars = small carbohydrate molecules Carbohydrates ~= C n H 2n O n Contain one C=O group and.

1Macromolecule class #1:

Polysaccharides

• Monomer = sugars

• Sugars = small carbohydrate molecules

• Carbohydrates ~= CnH2nOn

• Contain one C=O group and many –OH’s

• Can contain other functional groups as well (carboxyls, amines)

• Most common sugar and monomer is glucose

2

Glucose, straight chain depictions

With numbering

C C

Remember, always 4 bonds to carbon; Often even if not depicted

Abbreviated

3

anomeric carbon

Handout 2-7Haworth view

Fisher view

Chair view

4

1 234567891011

5

anomeric carbon

Handout 2-7Haworth view

Fisher view

Chair view

6

1 23456789

7

anomeric carbon

Handout 2-7Haworth view

Fisher view

Chair view

8

beta-glucose alpha-glucose

These two distinct molecules are 2 different “isomers” of glucose.These two are “steroisomers” differing only in 3-D structure.

9Ball and stick models of glucose

10Alpha glucoseAll the hydroxyls and the –CH2OH are sticking out equatorialExcept for the hydroxyl on the anomeric carbon 1

11

From Handout 2-7

2

5

3

12

From Handout 2-7

4

1

5

3

13

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

Handout 2-8

14

Glucose chair

http://www.scientificpsychic.com/fitness/glucosebdchair.gif

15

Glucose

}Gray = CWhite = HRed = O

Ring oxygen

C6 (-CH2OH)

C5

C1

hydr

oxyl

Alpha or beta?

16Chair depictions (from Googling chair + glucose)

Beta?

Alpha? Chair flip

If you could see my back . .

17

CHOH2

12

3

45

B eta-g lucose

Building a polymer from glucose

CHOH2

12

3

45

B eta-g lucose

OH

H

Alpha

18Polymers 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

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

Dimer formation

19AND: Polymers are broken down by the reverse process,

ADDING a molecule of water between them, known as

HYDROLYSIS

R-O-R + HOH→ R-OH + HO-RHere, dimer hydrolysis

This process does not happen by itself

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

20

CHOH2

12

3

45

B eta-g lucose

Building a polymer from glucose

CHOH2

12

3

45

B eta-g lucose

OH

H

Alpha

21

CHOH2

12

3

45

B eta-g lucose

CHOH2

12

3

45

B eta-g lucose+

22

O

H

H

H

CH OH2HO

HO HO

HH

4

O

H

H

H

CH OH2

HOOH

HO

HH

4

Beta-glucose residueBeta-glucose residue

Cellobiose

Glycosidic bond

Anomeric carbon is always one partner

Beta conformation is now locked in hereAnd ring is locked as a ring(loss of an H is necessary for rxn.)

But not hereGycosidic bond here isequatorial-to-equatorial

23

One is forced to draw strange “elbows” when depicting disaccharides using theHaworth projections

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

24

or glycogen chain

down

out

H

H

Cellulose

Tinker toys

Polysaccharide formation

25

Cellulose

3

6

3

6

26

or glycogen chain

down

out

H

H

Cellulose

More glucoses

27

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

28NucleusCytoplasm

Organelles

Starch granules

29So: structure FUNCTION

30anomeric carbon

anomeric carbon

a-glucosefructose ribose

Handout 2-6

5-membered ring works too

31

C2

glucose galactose mannose

C4

What’s different from glucose here?

Examples of other hexoses

allose

32More sugars:

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

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

Deoxyribose C5H10O5 (like ribose but one OH substituted by an H)

More disaccharides (These do not go further to become polysaccharides):

Lactose = glucose + galactose (milk sugar)

Sucrose = fructose + glucose (table sugar, cane sugar)

33

(Insect exoskeleton)

(Bacterial cell walls)Metabolic intermediate

34

Lipids

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

(so “operationally” defined)

• Heterogeneous class of structures

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

35A steroid

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

Really a small molecule

36

hormone hormone

co-factor, vitamin Membrane component

http://www.fas.org/irp/imint/docs/rst/Sect20/steroids.gif

H2C

37

A fatty acid

Fats

38

A trigyceride (fat)

Ester (functional group, acid + alcohol)}

Handout 2-9 top

39

trans

cis

cis

C C| |

HH

HH| |

| || C C| |

HH|| ||

- 2H

X

Free rotation about single bonds

No free rotationabout double bonds

cis

Solid fats

Oils

Effect of fatty acid structure on physical properties

Free rotation about single bonds

No free rotation about double bonds

C C|

|H

H

||

|

|

X

trans

40

Fatglobule

Nucleus

Adipocyte (fat storage cell)

41

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

If R = H, “phosphatidic acid”

}Handout 2-9

F.A.s can be of different sizes

42

[HO]

[HO]

Handout 2-9

43

R=another alcohol:A phospho-diester

}HO

HO

Handout 2-9

HO –CH2CH2N+H3

(alcohol = ethanolamine)

44HOH

HOH

Phosphate head

2 fatty acid tails each

Biological membranes are phospholipid bilayers

45

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

HydroxylAmineAmideCarboxylCarbonylAldehydeKetoneEster: Carboxylic acid ester

Phosphoester

And:

Glycosidic bondsC=C double bonds (cis and trans)

46

Amino acids (the monomer of proteins)

PROTEINS

R

47

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

48

Equilibrium state of the carboxyl group lies far towards the ionized molecule at pH7

49

+OH- ( -H+)

+H+

Net charge

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

50

Numbering (lettering) amino acids

Alpha-carbon

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

β

γδ

ε

ε-amino group

lysine

51Shown uncharged (as on exams)

52

53Amino acids in 3 dimensions

See ball and stick model

• Asymmetric carbon (4 different groups attached)

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

• L and D forms

From Purves text

54

Mannose

coming out at you

going behind the screen

55

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

56

Parts of a polypeptide chain

57

Without showing the R-groups:

The backbone is monotonous.It is the side chains that provide the varietyHandout 3-3

58“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)