Carbohydrates-sugarsMade of C, H,OCarb = Carbon hydrate = water Carbohydrate =

carbon + water general formula = C H2O 1-2-1 ratio of C to H to O

ribose C5H10O5

glucose C6H12O6

sucrose C12H22O11

many carbohydrate names end in -ose

More carbohydrate basicsMonomer: monosaccharide – one sugarFunctions of carbohydrates:

Energy for metabolism (glucose)Short term energy storage (glycogen/starch)Structure: plants – cell wall animals –

exoskeletonSource of carbon for other moleculesCell surface markers – cell identification

Monosaccharide: Simple SugarsMonosaccharides like glucose are the main

source of energy in living things

Disaccharides - 2 sugars2 monosaccharides linked together by

dehydration synthesis - form a glycosidic bond Examples: Sucrose – Table Sugar

glucose + fructose Lactose – Milk Sugar glucose + galactose

Polysaccharides-Many SugarsPolysaccharides are polymers composed of

large numbers of monosaccharides. - the monosaccharides are joined by

dehydration synthesis Used for short term energy storage and structure

Energy Storage PolysaccharidesStarch

polymer made up of glucose monomers

Stores glucose in plants

Chloroplast Starch

1 m

Starch: a plant polysaccharide

GlycogenPolymer of glucose monomersIs the major storage form of glucose in animalsStored in liver and muscleMore highly branched than starch – contains more stored energy

Mitochondria Glycogen granules

0.5 m

Glycogen: an animal polysaccharide

Glycogen

Starch and Glycogen are Easily Broken Apart by HydrolysisAllows the stored glucose to be easily used

Structural PolysaccharidesCellulose

Is a polymer of glucose – connected in a straight unbranched chain

Multiple strands of cellulose are held together by hydrogen bonds – makes a rigid structure

Is a major component of the tough walls that enclose plant cells

Plant cells

0.5 m

Cell walls

Cellulose microfibrils in a plant cell wall

Microfibril

CH2OH

CH2OH

OH

OH

OO

OHO

CH2OHO

OOH

OCH2OH OH

OH OHO

O

CH2OH

OO

OH

CH2OH

OO

OH

O

O

CH2OHOH

CH2OHOHOOH OH OH OH

O

OH OH

CH2OH

CH2OH

OHO

OH CH2OH

OO

OH CH2OH

OH

Glucose monomer

O

O

O

O

O

O

Parallel cellulose molecules areheld together by hydrogenbonds between hydroxyl

groups attached to carbonatoms 3 and 6.

About 80 cellulosemolecules associate

to form a microfibril, themain architectural unitof the plant cell wall.

A cellulose moleculeis an unbranched glucose polymer.

OH

OH

O

OOH

Cellulosemolecules

Figure 5.8

Cellulose is difficult to digestAnimals can’t break the bonds between the

glucose molecules –dietary fiberAnimals that eat plants have bacteria in their

stomachs that can break the bonds of cellulose- allow their hosts to digest plants

Figure 5.9

Chitin, another important structural polysaccharide Is a polymer of a form of glucose with

an attached functional groupIs found in the exoskeleton of

arthropods

Figure 5.10 A–C

(a) The structure of the chitin monomer.

O

CH2OH

OHHH OH

H

NH

CCH3

O

H

H

(b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emergingin adult form.

(c) Chitin is used to make a strong and flexible surgical

thread that decomposes after the wound or incision heals.

OH

Other Uses for CarbohydratesCell surface markers – carbohydrates

attached to parts on the cell membrane where they act to identify the cell

ABO blood groups are identified by carbohydrates on their surface