Molecules of Life. Molecules of Life Carbohydrates –m–monosaccharides –e–energy supply Proteins –a–amino acids –s–structural components Lipids –f–fatty.

Molecules of Life

Molecules of Life• Carbohydrates

– monosaccharides– energy supply

• Proteins– amino acids– structural components

• Lipids– fatty acids– structural components, energy, hormones

• Nucleic acids– nucleotides– DNA-genetic material

Composition • Most-carbon based• organic compounds • unique to living systems

– with exception of CO2 & carbides

• carbon is necessary for life

• electroneutral– never loses or gains

electrons– always shares or forms

covalent bonds

Covalent Bonding• carbon can form 4

covalent bonds with other elements or with itself– has 4 electrons in

outermost shell• makes each carbon

atom a connecting point from which another molecule can branch in four directions

H |

H--C--H | H

Covalent Bonding• since carbon can bind

to itself• has capacity to

construct endless numbers of carbon skeletons varying in size & branching patterns

Organic Compounds• chain of carbons-carbon

skeleton• branched or unbranched• double or single bonds• straight or arranged in ring

form• each has a unique 3-D shape• properties depend on carbon

skeleton & atoms attached to skeleton

• groups of atoms participating in chemical reactions are functional groups

H | C ||| C | H

Functional Groups• OH- (hydroxyl)• C=O (carbonyl)• COOH (carboxyl)• NH2 (amino)• SH-sulfhydryl

group• PO3 (phosphate) Phosphate group

Classes of Molecules Related to Functional Groups

• COOH & NH2- amino acids

• hydroxyl groups-alcohols• carboxyl groups-

carboxylic acids-acetic acid

• sugars contain both-carbonyl group & several hydroxyl groups

• phosphate groups-nucleic acids

Macromolecules• 4 main classes• consist of many identical or

similar molecular units strung together– monomers

• cells link monomers in anabolic reactions by dehydration synthesis– chemical reaction which

removes water• broken down into monomers by

adding water– catabolic reactions-

hydrolysis

Carbohydrates• composed of C, H & O• 1:2:1 ratio• Formula: (CH2O)n gives formula for

any carbohydrate• may contain nitrogen, phosphate

and/or sulfur• Monomers-monosaccharides

– simple sugars– building blocks for all other

carbohydrates• 2-10 monosaccharides form

oligosaccharide• hundreds- polysaccharide.• hydrophilic

– water loving• larger molecules are less soluble

in water

Glucose

Monosaccharides• simple sugars• single chain or ring of 3-7 carbons• named for number of carbons they

contain• 5 carbons-pentoses• 6 carbons-hexoses• glucose contains 6 carbons-hexose• formula-C6H1206

– most important metabolic fuel in body

– broken downATP + CO2

• fructose-6 carbon monosaccharide• same formula as glucose • fructose & glucose are isomers

– chemical compounds with same molecular formula but with elements arranged in different configurations

• Galactose-isomer of glucose & fructose

Glucose

Galactose

Fructose

Disaccharides• double sugars• covalent bond- between hydroxyl

groups of two simple sugars• physiologically important

disaccharides Sucrose– sugar cane & sugar beets– Glucose + fructosesucrose +

H2O• Lactose-found in milk of mammals

– disaccharide of galactose & glucose

• Maltose– major degradation product of

starch– composed of 2 glucose monomers

• Disaccharides-too large to pass through cell membranes

• must be broken down into constituent parts by hydrolysis

• Sucrose + H20 glucose + fructose.

Polysaccharides• complex carbohydrates• dehydration synthesis reactions add more

monosaccharides polysaccharides• most carbohydrates in nature are in this

form• fairly insoluble

– make perfect storage molecules• Glycogen

– major stored carbohydrate in animal liver & muscle cells

– highly branched at about every 8-10 residues

• Starch– major form of stored carbohydrate in

plants– Structure-identical to glycogen-less

branching at every 20-30 residues• Cellulose

– found in plants– most abundant compound on earth– cannot be digested by humans

Lipids• contain mostly C & H• 1:2 ratio• also contain oxygen

(less than carbohydrates)

• often have N, S & phosphorous

• hydrophobic– do not dissolve in

water• neutral fats,

phospholipids & steroids

Lipid Functions• structural components of

biological membranes– cholesterol, phospholipids &

glycolipids form & maintain intracellular structures

• energy reserves– provide 2X as much energy

as carbohydrates• hormones & vitamins-steroids• lipophilic bile acids

– important for lipid solubilization

Lipids• composed of fatty acids & glycerol (an alcohol)• fatty acids-long-chain hydrocarbon

molecules• hydrocarbon chains make lipids nonpolar

and therefore insoluble in water• fat synthesis involves attaching 3 fatty acid

chains to one glycerol by dehydration synthesis-producing triglycerides

• glycerol is always the same; fatty acid composition varies

• length of neutral fat’s fatty acid chains & degree of saturation determine how solid a fat is at room temperature

• saturated– fatty acids with no carbon to carbon

double bonds• unsaturated

– have double bonds• monounsaturated fats have one

unsaturated bond• polyunsaturated fats have multiple

unsaturated bonds• double bonds make for lower melting points• presence of unsaturated fatty acids makes

fat liquid at room temperature

Hydrolysis of Triglycerides

• Hydrolysis breaks triglycerides

• fatty acid + glycerol

Steroids• large lipid molecules with carbon

skeleton bent into 4 rings• most important one-cholesterol• obtained by absorption from

animal products in diet– meat, cream & egg yolks

• can also be made by the body• absolutely essential for life• component of cell membranes• raw material for Vitamin D, steroid

hormones & bile salt synthesis• needed to make steroid hormones

such as estrogen & testosterone • corticosteroids-essential for life

Proteins• C, H, O, N & small

amounts of S & sometimes phosphorous

• monomer-amino acids• 1-7 amino acids-

peptide• up to 100-polypeptide• more than 100- protein

Proteins• most abundant organic compound in human

body• provide support for cells, tissues & organs

and create a 3-D framework for body• contractile proteins allow for movement via

muscle contractions• transport proteins carry insoluble lipids,

respiratory gases & minerals in blood• serve as buffers; help to prevent dangerous

pH changes• enzymes are proteins important in

metabolic regulation– speed rate of chemical reactions

• protein hormones coordinate, control & influence metabolic activities of nearly every cell

• important for defense• skin, hair, & nails protect underlying tissues

from environment• antibodies protect from disease• clotting proteins protect from from bleeding

out

Amino Acids• 20 amino acids

• (excluding proline) contain carboxylic acid-COOH & amino-NH2 or amine group

• functional groups are attached to same carbon atom

• R group attaches to same carbon • amino acid is distinguished by its particular

R-group• 2 broad classes based upon whether R-

groups-hydrophobic or hydrophilic • hydrophobic repel aqueous environments

– reside predominantly in interior of proteins

• hydrophilic amino acids interact with aqueous environments & often form H-bonds– found predominantly on exterior of

proteins

Protein Structure• each protein

contains unique sequence of amino acids

• four levels of protein structure

• Primary

• Secondary

• Tertiary

• Quaternary

Structure & Function• structure determines function• shape of protein allows it to carry

out specific duties• protein whose job is to fill in a

space (active site) on another molecule-globular in shape

• those that make up muscles or tendons-fibrous

• shapes depend on environmental characteristics– ionic composition, pH &

temperature• non homeostatic change in any of

these will denature protein• denaturation causes protein to

lose shape• loss of shapecannot function

properly

Nucleic Acids• largest, organic molecules in

body• C, H, O, N, & phosphorous• long stretches of nucleotides

– monomer for nucleic acids• provide directions for building

proteins• RNA

– translates DNA code• DNA

– contains genetic information that is inherited from our parents

Nucleic Acids• RNA

–single polynucleotide chain

• DNA–double helix form–two polynucleotide

chains wrapped around one another

Nucleic Acids• exist in mono-, di-, & tri-

phosphorylated forms• often abbreviated to AMP• Mono, Di- & tri-phosphorylated

forms of adenosine are abbreviated AMP, ADP & ATP

• phosphate bonds are high energy bonds– bonds contain energy– broken-yield 7kcals

• ATP ADP + Pi + energy• ATP is energy currency of all

cells