Macromolecules

Chapter 5

All are polymers

Monomer – subunit of polymer

Macromolecule – large organic polymer

Those found in living systems:

Carbohydrates

Lipids

Proteins

Nucleic acids

MUST KNOW for each group

• Monomers

• Type of bond or linkage between monomers

• Examples – in living systems

• Functions – in living systems

Carbohydrates

• C, H, O

• Monomer= Monosaccharide (like glucose)

Lipids

• C, H, O

• Monomer = glycerol and fatty acids

Proteins

• C, H, O, N

• Monomer = Amino Acid

Nucleic Acid

• C, H, O, N, P

• Monomer = Nucleotide

Polymerization reactions

• Condensation (dehydration synthesis)

– Monomers join covalently

– Removal of water molecule

– One monomer loses –0H

– One loses –H

– These join to form water

– Requires energy and catalysts (enzymes)

• Hydrolysis– Breaks covalent bond by addition of water

– Digestive enzymes catalyze hydrolysis

• 40-50 common monomers (unity)

• Arranged in different ways (diversity)

Compare dehydration synthesis with hydrolysis

Carbohydrates

• Monomers – monosaccharide (usually multiples of CH2O like C6H12O6)

–Glucose, fructose, galactose–Glucose most common

• Stores energy in chemical bonds

Dihydroxyacetone

Ribulose

Ket

oses

Ald

oses

Fructose

Glyceraldehyde

Ribose

Glucose Galactose

Hexoses (C6H12O6)Pentoses (C5H10O5)Trioses (C3H6O3)

(a) Linear and ring forms (b) Abbreviated ring structure

Disaccharide

• double sugar (2 monosaccharides)

• Dehydration synthesis –> formula ?

• Glycosidic linkage formed-covalent bond forms by dehydration syn.

• Glucose + glucose = maltose

• Glucose + galactose = lactose

• Glucose + fructose = sucrose

Dehydration Synthesis

(b) Dehydration reaction in the synthesis of sucrose

Glucose Fructose Sucrose

MaltoseGlucoseGlucose

(a) Dehydration reaction in the synthesis of maltose

1–4glycosidic

linkage

1–2glycosidic

linkage

Dehydration synthesis

Polysaccharides

• 100 to 1000 monosaccharides• Functions:• Storage polysaccharides:

– Starch – plants • Stored in plastids (amyloplast)

– Amylose – simplest starch– Animals have enzymes to hydrolyze starch

Amylopectin

• Glycogen – animal storage polysaccharide– Stored in muscles and liver of vertebrates– Provides energy to humans for about a day

Glycogen

• Structural polysaccharides– Cellulose – plant cell wall

• Most abundant organic compound on Earth

– Differs from starch in glycosidic linkage

– Cannot be digested by most organisms

– Exceptions-cows, termites have microorganisms that digest cellulose

Starch and cellulose-how are they different?

• Based on –OH attached to no. 1 carbon

• Starch = alpha configuration, often helical

• Cellulose = beta configuration, straight (glucose “upside down”)

Chitin – structural polysaccharide in animals

• Polymer of amino sugars (has a nitrogen group)

• Exoskeleton of arthropods (insects, spiders, crustaceans, etc.)

• Cell walls of some fungi• Surgical thread

Lipids

• Hydrophobic• Diverse group, not considered

polymers• 1. FATS

– Monomers: one glycerol + 3 fatty acids• Triglyceride or triacylglycerol

– Dehydration synthesis (condensation)– Ester linkage –> 3 H2O molecules

ExplainEster linkage

Characteristics of fats

• Insoluble in water– b/c C-H bonds nonpolar

• Variation due to fatty acid composition– Vary in length

– Vary in number and location of double bonds

Compare fatty acids

Compare saturated and unsaturated fats

• Double bonds ?• At room temperature?• Examples?• Artificial hydrogenation

– Converting unsaturated fatty acids to saturated by adding what?

– peanut butter– Prevents lipids from separating out in liquid

form

Function of fats

• Energy storage – 1g of fat stores twice as much energy as 1g polysaccharide– More compact fuel reservoir

• Cushions vital organs

• Insulates against heat loss

Phospholipid

• Monomers: one glycerol, 2 fatty acids, one phosphate group

• Phosphate negatively charged

• Fatty acid tail – hydrophobic

• Phosphate head – hydrophilic

Phospholipid

Phospholipid and self-assembly into bilayer

Functions

• Cell membranes– Form a bilayer

• Hydrophilic heads to exterior

• Hydrophobic tails to interior

Steroids

• Lipids with 4 fused carbon rings

• Cholesterol – important steroid

– Precursor to sex hormones and bile acids

– Component of cell membranes

– Can contribute to atherosclerosis