the molecular building blocks of life

The The Molecular Molecular Building Building Blocks of LifeBlocks of Life

ObjectivesObjectives

3.2.1 – Distinguish between organic and inorganic compounds.3.2.2 – Recognize the physical differences between the macromolecules that are the building blocks of life.3.2.3 – State the uses for carbohydrates, lipids, nucleic acids, and proteins

The Importance of The Importance of carboncarbonCells are 70-95% water, the remainder is mostly

carbon-based compounds.Proteins, DNA, carbohydrates, & lipids distinguish living matter from inorganic material; all are composed of carbon atoms bonded to each other & to atoms of

other elements, including H, O, N, S, & P (percentages are quite uniform in all life).

oxygen (65 percent); carbon (18 percent); hydrogen (10 percent); nitrogen (3 percent); phosphorus (1 percent); andsulfur (0.2 percent).

Organic chemistryOrganic chemistryOrganic chemistry is the study of carbon

compounds.Produced not only in biological processes, they can also be synthesized by non-living reactions.Organic compounds range from

simple CH4 (below), to complex molecules, like proteins &

DNA (at right).

Organic chemistryOrganic chemistryOrganic compounds contain carbon & hydrogen

together!CH4 – methane, C8H18 – octane, C6H12O6 – glucose

If a carbon compound is not accompanied by hydrogen,

it is considered inorganic.

CO2 – inorganic (no H)

CCl4 – inorganic (no H)

CoCl2 – inorganic (no C)

CaHPO4 – inorganic (no C)

HCl – inorganic (no C)Don’t be fooled!

Atomic carbonAtomic carbonCarbon atoms are the most versatile building

blocks of molecules.With a total of 6 e-, a C atom has 2 in the first shell and 4 in the second shell.Only outer shell elec-

trons are involved in chemical reactions, so

C has 4 e- to share (it makes 4 attachments).

Carbon is tetravalentCarbon is tetravalentCarbon shares 4 electrons.

Note C makes 4 attachments, but H makes only 1.

Carbon is tetravalentCarbon is tetravalentCarbon can bond with itself; there are still

always 4 attachments (4 bonds).Ethylene (-ene signifies a double bond)

Isomers of butyne – (-yne signifies a triple bond); still a total of

four bonds on each carbon atom.

Carbon is tetravalentCarbon is tetravalentThe e- configuration of C lets it form covalent

bonds with many different elements.

In carbon dioxide, one C atom forms 2 double bonds with 2 different O atoms. The structural formula, O = C = O, shows that each atom has completed its valence shells. CO2 is the source for all organic molecules in organisms via the process of photosynthesis.

Carbon is tetravalentCarbon is tetravalentAnother example:

Urea, CO(NH2)2, is a simple organic molecule in which each atom has enough covalent bonds to complete its valence shell.

H needs 1 e-

O needs 2 e-

N needs 3 e-

HydrocarbonsHydrocarbonsHydrocarbons: organic molecules that consist of only

C & H.Hydrocarbons are the major component of petroleum.Petroleum is a fossil fuel because it consists of the partially decomposed remains of organisms that lived millions of years ago.

Carbon-based life formsCarbon-based life formsLife on Earth is based on carbon.

Four types of carbon molecules are building blocks.

CarbohydratesLipidsNucleic acidsProteins

CarbohydratesCarbohydratesFunction: fuel and building material; made of

equal amounts of C+H2O (carbon hydrates). #H = 2x #O.

Monosaccharides (simple sugars).

Ex: glucose

Disaccharides (double sugars). Ex: sucrose

Polysaccharides are long chains of

monosaccharides.Ex: starch

(in flour)

CarbohydratesCarbohydratesMonosaccharides have molecular formulas that

are some multiple of CH2O. Ex: glucose - C6H12O6. (#H = 2x #O)

Most names for sugars end in –ose: glucose, ribose.

Disaccharides form from monosaccharides by dehydration (an H and an OH are removed).

Glucose + glucose produces maltose (and water)

CarbohydratesCarbohydratesPolysaccharides are polymers of hundreds to

thousands of monosaccharides.1) Function in energy storage (used as needed).

Ex: starch (plants) & glycogen (in animals’ livers)

2) Function as strong building materials. Ex: cellulose

LipidsLipidsLipids are hydrophobic – don’t mix with water.

In a triglyceride, three fatty acids (same or different) are joined to glycerol. Made of C, H, & O, but the H:O ratio is much greater than 2:1.

LipidsLipidsA saturated fat has no carbon-carbon double bonds, and it is straight. They pack together – solid at room temperature.Unsaturated fats have one or more carbon-carbon

double bonds, and they bend. They can’t get close to each other, so they are liquid at room temperature.

LipidsLipidsSaturated fats come from animal products.

Ex: butter, lardA diet rich in saturated fats may contribute to cardiovascular disease (heart attack, stroke) through plaque deposits in arteries; obesity, diabetes.

LipidsLipidsUnsaturated fats come from plant & fish

products.Ex: olive oil, corn oil, safflower oil, fish oils.Generally considered healthier for the heart.

LipidsLipidsFunctions of lipids

Nutrition: 1g of fat contains twice as much energy as 1g of carbohydrate.Protection: cushions vital organs & insulates them.

This subcutaneous layer is especially thick in whales, seals,

and most other marine

mammals.

LipidsLipidsFunctions of lipids

Phospholipids: major components of cell membranes.

Have two fatty acids attached to glycerol and a phosphate group at the third position.

LipidsLipidsFunctions of lipids

Waxes reduce water loss by plants.Carnauba wax

SteroidsCholesterol is a component in animal cell membrane.Many steroids are hormones.

Nucleic acidsNucleic acidsAll molecules of the body are programmed by a

genetic code in the organism’s DNA, a polymer of nucleic acids.

Nucleic acids store and transmit hereditary in-formation.Made of C, H, O, N, & P.

A nucleic acid

Nucleic acidsNucleic acidsThere are two types of nucleic acid polymers:

Ribonucleic acid (RNA)Single-stranded.Contains adenine,

guanine, cytosine,and uracil.

Sugar is ribose.

Deoxyribonucleic acid (DNA)

Double stranded.Contains adenine, guanine, cytosine, and thymine.Sugar is deoxyribose.

ProteinsProteinsHumans have at least 30,000 different proteins,

each with a unique structure and function.Functions include structural support, storage, transport of materials, intercellular signaling, movement, and defense.Enzymes are one class of proteins that regulate

metabolism by moderating chemical reactions. All proteins are 3 dimensional.All are constructed from the same set of 20 monomers, called amino acids.All are made of C, H, O, and N (2 also contain S).

ProteinsProteinsAmino acids are joined

by dehydration; the resulting covalent bond is called a peptide bond.

Polymers of amino acids are called polypeptides.

ProteinsProteinsA protein’s function depends on

its precise twisting, folding, and coiling into a

unique shape. The order of amino acids

determines what the three-dimensional shape will be.

Folding of a protein occurs spontaneously: an emergent

property resulting from itsspecific molecular order.

ProteinsProteinsIn individuals with sickle cell disease, abnormal

hemoglobins develop because of a single amino acid substitution.

ProteinsProteinsFibrous proteins are long, insoluble molecules .

For movement (muscle fibers);For structure and support.  

Collagen in skin.

Cartilage connects tissues.

Keratin is found in hair, horns, wool, nails, and feathers.

ProteinsProteinsGlobular proteins are soluble and form compact

spheroidal molecules in water.  

Antibodies for immunity.

Enzymes are involved in chemical reactions

- metabolism (enzymes generally end in –

ase).

Transport proteins and receptor proteins in

the cell membrane.

Hemoglobin – transport of oxygen

ProteinsProteinsTransport proteins and receptor proteins in the

cell membrane capture chemicals in the blood and may move them into the cell.

ProteinsProteinsEnzymes catalyze chemical reactions (metabolism).

One enzyme is specific for each chemical reaction.Enzymes convert one substrate (the raw material) into some product.

Ex: sucrase: binds to sucrose and breaks this disac- charide into fruc- tose and glucose.

Enzymes end in –ase.

ProteinsProteinsA protein’s shape can change in response to

changes in pH, salt concentration, temperature. These forces disrupt the bonds that maintain the protein’s shape. This is called denaturation. Then the protein won’t work right!