CHAPTER 3: THE CHEMISTRY OF LIFE

The Structure and Function of Large Biomolecules

Intro Recap

Essential Elements - CHONPS Carbon Hydrogen Oxygen Nitrogen Phosphorus Sulfur

Make up the 4 major molecules in your body Carbs Proteins Lipids Nucleic acids

Macromolecules

Huge molecules made of many smaller molecules and atoms Carbohydrates Proteins Nucleic Acids

Lipids don’t count!

Polymers and Monomers

mono = one Subunits of

polymer

poly = many One polymer is

made up of many monomers bonded together

Monomer Polymer

Sugar

Sugar

Sugar

Sugar

Dehydration Synthesis = Condensation The way that polymers are

assembled Dehydration – water is

removed Synthesis – to make Remove water to make a bond

Fig. 5-2a

Dehydration removes a watermolecule, forming a new bond

Short polymer Unlinked monomer

Longer polymer

Dehydration reaction in the synthesis of a polymer

HO

HO

HO

H2O

H

HH

4321

1 2 3

(a)

Hydrolysis

The way that polymers are broken down (metabolized) Hydro – water Lysis – to cut/break Add water to break a bond

Where does a lot of hydrolysis happen?

Fig. 5-2b

Hydrolysis adds a watermolecule, breaking a bond

Hydrolysis of a polymer

HO

HO HO

H2O

H

H

H321

1 2 3 4

(b)

Carbohydrates

Sugars and their polymers Monosaccharides – one sugar

(building block) Disaccharides – two sugars Polysaccharides – many sugars

Multiple of the unit CH2O Glucose C6H12O6

Sugars

Can be chains or rings (3-7 carbons long) Have a carbonyl group (>C=O) Many hydroxyl groups (–OH)

Ald

oses

Glyceraldehyde

Ribose

Glucose Galactose

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

Fig. 5-4a

(a) Linear and ring forms

Fig. 5-4b

(b) Abbreviated ring structure

Starch – a polymer of glucose Plants store sugars for later use

(inside plastids)

Functions of carbs in animals

Glucose: chemical fuel for respiration (mono)

Lactose: makes up some solutes in milk (di)

Glycogen: glucose storage in liver and muscles (poly)

Functions of carbs in plants

Fructose: found in fruits; make them sweet (mono)

Sucrose: transported through phloem (di)

Cellulose: components of cell walls (poly)

Fig. 5-8

b Glucosemonomer

Cellulosemolecules

Microfibril

Cellulosemicrofibrilsin a plantcell wall

0.5 µm

10 µm

Cell walls

Starch and Cellulose Digestion

Enzymes that digest starch by hydrolyzing linkages can’t hydrolyze linkages in cellulose

Cellulose in human food passes through the digestive tract as insoluble fiber

Chitin – a structural polysaccharide Found in the exoskeleton of arthropods Structural support for the cell walls of

many fungi

Lipids

Hydrophobic – they mix poorly with water

Mostly hydrocarbon regions – nonpolar

Fats - CHO

1 glycerol (alcohol with 3 carbons) + 3 fatty acids (long chain of CH connected to carboxyl)

Fatty acid(palmitic acid)

(a)Dehydration reaction in the synthesis of a fat

Glycerol

Fig. 5-11b

(b)Fat molecule (triacylglycerol)

Ester linkage Esterification

Saturated vs. Unsaturated

have the maximum number of hydrogen atoms possible and no double bonds

have one or more double bonds

Saturated fatty acids Unsaturated fatty acids

Animal vs. Plant

Most animal fats No double bonds

makes the tail flexible They can pack

together tightly Solid at room

temp

Most plant fats (oils) Double bonds

makes them bent Can’t pack together Liquid at room temp

Hydrogenated = added Hs to make them saturated

Saturated Fats Unsaturated Fat

What do fats do?

Too much saturated fat is bad for you Atherosclerosis –

plaques of fat in blood vessels

Hydrogenation forms trans fats – even worse!

Store lots of energy 2x as much as

carbs! Cushions vital

organs Insulates the

body

Bad things Good things

Phospholipids – make up cell membranes

(b)Space-filling model (c)Structural formula Phospholipid symbol

Fatty acids

Hydrophilichead

Hydrophobictails

Choline

Phosphate

Glycerol

Hyd

rop

hob

ic t

ails

Hyd

rop

hilic

head

One fatty acid is replaced by a phosphate

Phospholipid Bilayer – Cell Membrane

Polar Phosphate Heads

Non-Polar Fatty Acid Tails

Steroids

4 fused carbons rings

Hormones – cell to cell signaling (long distance)

Cholesterol – stabilizes cell membranes Made in liver Too much is bad

Other functions of lipids

Protection of vital organs

To insulate the body

They form the myelin sheath around some neurons

Proteins – CHON(S)

Needed for almost everything that happens in your cells/body

Function Example

Enzymes Amylase

Transport Hemoglobin

Movement Actin, myosin

Cell Recognition

Antigens

Channels Membrane Proteins

Structure Collagen, keratin

Hormones Insulin

Protection Antibodies

Polypeptides

Polymers of animo acids Not a protein

– doesn’t have full structure

R groups – ~20 in humans

The R group’s structure determines the property of the amino acid Example: Alanine = CH3

CH3 is nonpolar and so is Alanine

Alanine (Ala or A)

Fig. 5-17a

Nonpolar

Glycine (Gly or G)

Alanine (Ala or A)

Valine (Val or V)

Leucine (Leu or L)

Isoleucine (Ile or I)

Methionine (Met or M)

Phenylalanine (Phe or F)

Tryptophan (Trp or W)

Proline (Pro or P)

Fig. 5-17b

Polar

Asparagine (Asn or N)

Glutamine (Gln or Q)

Serine (Ser or S)

Threonine (Thr or T)

Cysteine (Cys or C)

Tyrosine (Tyr or Y)

Fig. 5-17c

Acidic

Arginine (Arg or R)

Histidine (His or H)

Aspartic acid (Asp or D)

Glutamic acid (Glu or E)

Lysine (Lys or K)

Basic

Electricallycharged

Peptide Bond (“polypeptide”) Made by

dehydration synthesis (condensation)

Nucleic Acids - CHONP

Polymer – nucleic acid Monomer -

nucleotide Hold the

information to make polypeptides (on genes)

Nucleic Acids

Each nucleotide has 3 parts: Nitrogenous

base Sugar Phosphate

group

Sugars

Always 5 carbons: Ribose – RNA

Deoxyribose – DNA

Nitrogenous Bases

Nitrogen containing rings

(c) Nucleoside components: nitrogenous bases

Purines

Guanine (G)Adenine (A)

Cytosine (C) Thymine (T, in DNA)Uracil (U, in RNA)

Nitrogenous basesPyrimidines

Double Helix

DNA strands are complementary A—T C—G

Double Helix

Spiral shape of DNA coil

Held together by H-bonds between bases And van der

Waals attractions