Chapter 3

Life’s Chemistry

Carbon- life on earth – major molecule that make up living systems

Bonds with four other atoms – variety of shapes and functions.

Living cells use C to make complicated molecules.

Organic molecule- hydrocarbons.

The function of carbon molecule changes – functional groups added to carbon skeleton.

Functional groups- atoms or groups of atoms which add functions by combining O,P,S & N to large carbon skeletons.

Major Organic Molecules (Life depends)Molecules that contain carbon in

combination with hydrogen. Four major groups:• carbohydrates• lipids• proteins• nucleic acids

How do humans acquire these molecules?

Cells use molecules – to maintain life

Polymers: large biologically important molecules are constructed by bonding smaller molecules (monomers)

• Dehydration synthesis – the process of building polymers

• Hydrolysis - the process of breaking down polymers

Polymers expand properties of monomers

1. Carbohydrates • contain C, H & O [1:2:1]• function to store energy & provide support

• building blocks (monomers) are monosaccharides

Eg. Sugar & starch

Carbon forms – infinite variety of molecules

Functional groups- molecules that add function to other molecules

Major molecules- carbohydrates, lipids, proteins and nucleic acids

Large biological molecules- polymers-different properties than the unit monomers

Polymers – made through dehydration synthesis and recycled through hydrolysis.

Monosaccharides • simple sugars containing 3 - 7

carbons.• C, H, O ratio is 1:2:1

Disaccharides • simple sugars composed of 2

monosaccharides linked together by dehydration synthesis.

Other common disaccharides: maltose (seed sugar) & lactose (milk sugar).

OligosaccharidesModerately sized- for identification

and forming complex structures.Glycoproteins, glycolipds- on cell

suface- immunity protecting animal’s body from infection

Polysaccharides • complex carbohydrates made up of

hundreds of monomers linked by dehydration synthesis.

Eg. Cellulose, chitin, starch and glycogen.

Differ by orientation of bond that link monomers.

Carbohydrates- formula (CH2O)n. Most common – GLUCOSE

Oligosaccharides- identity molecules.

Polymers of glucose form complex carbohydrates such as starch.

Changing the arrangement of monomers and modifying glucose produce different characteristics for starch, cellulose and chitin.

2. Lipids • contain C, H, O [ C >> O]• do not dissolve in water but in

organic solvents• Vital to life• Hydrophobic-major component of

membrane• Within cells form compartments,

separating one aqueous environment from another

Triglycerides (fats)composed of glycerol linked to 3 fatty acid chains by dehydration synthesis.

Fatty acids – long hydrocarbons up to 36 carbon atoms with an acidic functional group.

Fatty acids can be saturated or unsaturated

function to cushion organs, as insulation & in long-term energy storage (adipose tissue).

Combine to form more complex lipids.

Phospholipids• lipid bonded to a phosphate group• major component of cell

membranes• Enzymes replace one of the fatty

acids in a TG with phosphate.

Sterols• lipids that have 4 interconnected

carbon ringsEx. Vitamin D, cortisone, estrogen &

cholesterol

Cholesterol-vital for cells- maintain fluidity of cell membranes

Synthesized in liver

Waxes• fatty acids combined with hydrocarbons• help waterproof fur, feathers, leaves &

fruits• Jojoba oil- shampoos – liquid wax.

Attaching fatty acids to glycerol- produce-fats (TG) or membrane components (PL).

Sterols – lipids- based on an interconnecting ring structure. Eg: cholesterol and sex hormones.

Cholesterol- vital to cells.

3. Proteins• contain C, H, O, N, (S)• monomers are amino acids• Differ from carbohydrates and lipids.• Proteins- control all life’s

activities.• Proteins – blood to clot, muscles to

contract, oxygen to reach tissues.• Enzymes – poteins- allow

biochemical reactions to proceed fast- sustain life.

• Structural proteins – bone and hair.

Amino acid: central C tom bonded to 4 different functional components.

Proteins have a 3-dimensional shape (conformation):

• primary (1o) structure - amino acid sequence of polypeptide chain

• secondary (2o) structure - coiling & folding produced by hydrogen bonds

• tertiary (3o) structure - shape created by interactions between R groups

• quarternary (4o) structure - shape created by interactions between two or more polypeptides

A change to the shape of a protein causes denaturation.

Examples:• antibodies• hemoglobin• insulin & glucagon• keratin• fibrin & thrombin• spider silk (strongest natural fiber

known)• enzymes (maltase, pepsin, lipase)

Enzyme mechanism of action• Enzymes can be used to join

substrates or break apart substrates.

• The shape of the enzymes active site is critical to proper functioning.

Proteins- provide majority of life’s function.

20 aa forms the basis of all proteins

Final conformation of a protein- levels of interactions between components of polypeptide.

Changes in temp, pH or ions in environment of a protein will denature the shape and function.

4. Nucleic Acids • contain C, H, O, N, P• monomers are nucleotides

DNA (deoxyribonucleic acid)• 5-carbon sugar is

deoxyribose• nitrogenous bases

are A, G, C & T• double-stranded

helix held together by hydrogen bonds

• is the genetic material

RNA (ribonucleic acid)• 5-carbon sugar is

ribose• nitrogenous bases

are A, G, C & U• single-stranded• enables

information in DNA to be expressed

Nucleis acids- polymers of nucleotides.

Nucleotides- A, C, T, G and U.

DNA & RNA use different bases.

DNA stores information in the sequence of its nucleotides.

Genetic code- same all life on Earth.

Gene- sequence of nucleotides- having information for an entire protein.

ATP- key energy carrier.