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 common monomers (unity) Arranged in different ways (diversity )

Compare dehydration synthesis with hydrolysis

Carbohydrates Monomers – monosaccharide (usually multiples of CH 2 O like C 6 H 12 O 6 ) –Glucose, fructose, galactose –Glucose most common Stores energy in chemical bonds

Dihydroxyacetone Ribulose Ketoses Aldoses Fructose Glyceraldehyde Ribose Glucose Galactose Hexoses (C 6 H 12 O 6 ) Pentoses (C 5 H 10 O 5 ) Trioses (C 3 H 6 O 3 )

(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 GlucoseFructose Sucrose MaltoseGlucose (a) Dehydration reaction in the synthesis of maltose 1–4 glycosidic linkage 1–2 glycosidic 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 –M–Monomers: one glycerol + 3 fatty acids Triglyceride or triacylglycerol –D–Dehydration synthesis (condensation) –E–Ester linkage –> 3 H 2 O molecules

Explain Ester 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