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Molecules of Life

� Organic Compounds ¡ Complex Carbohydrates ¡ Lipids ¡ Proteins ¡ Nucleic Acids

What are the molecules of life?

Organic Compounds

Carbon- hydrogen based molecules

From Structure to Function Ø Carbon’s importance to life stems from its versatile bonding behavior

Carbon can make four bonds

Ø Many organic molecules have a backbone: chain of carbon atoms

Ø Carbon can bond to other carbon atoms and to many other elements

Hydrocarbons

Organic molecules containing only carbon and hydrogen Generally nonpolar

Functional Groups

An atom or group of atoms that is attached to the carbon skeleton of the organic molecule and gives it its unique chemical properties

Molecular Formula Structural Formula

Isomers: Molecules with same molecular formula but different molecular structures Arrangement of atoms/ Emergent properties

Glucose: C6H12O6 Fructose: C6H12O6

Molecules of Life: Biological Molecules

All biological systems are based on the same biological molecules The details of those molecules differ among organisms

Ø Monomers: subunits of larger molecules

Ø Polymers: consist of multiple monomers

Ø Cells build polymers from monomers, and break down polymers to release monomers

Simple organic building blocks bonded in different numbers and arrangements form different versions of the molecules of life

Molecules of Life: Organic Macromolecules Essential for Life

Condensation Reactions/ Dehydration Synthesis

The Process by which cells link monomers to form a polymer

Hydrolysis

The process by which macromolecules or polymers are broken down into monomers

Carbohydrates

Monosaccharides/ Simple sugars

Polysaccharides/ Complex carbohydrates/ Long chains

Structure, Energy and Storage C, H, O (1:2:1)

Oligosaccharides/ Short chains

Monomers of carbohydrates

Monosaccharides One sugar

Common monosaccharides have a backbone of five or six carbon atoms

Glucose

In aqueous solutions, many monosaccharides form rings

Glucose

Ø Cells use monosaccharides for cellular fuel Ø Breaking the bonds of sugars releases energy

that can be harnessed to power other cellular processes

Ø Monosaccharides are also used as: Ø Precursors for other molecules Ø Structural materials to build larger molecules

Oligosaccharides

Ø  Oligosaccharides are short chains of covalently bonded monosaccharides

Ø  Disaccharides consist of two monosaccharide monomers

Ø  Examples: Ø  Lactose: composed of glucose + galactose Ø  Sucrose: composed of glucose + fructose

How do disaccharides form?

Polysaccharides

Ø Formed by the process of dehydration synthesis

Ø Chains of hundreds or thousands of monosaccharide monomers § Cellulose § Starch § Glycogen

Ø Main structural component of plants cell wall Ø Tough and insoluble Ø Composed of chains of glucose monomers

stretched side by side and hydrogen-bonded at many —OH groups

Cellulose

Starch Ø Main energy reserve in plants Ø Stored roots, stems, leaves, seeds, and

fruits Ø Composed of a series of glucose

monomers that form a chain that coils up

Glycogen

Ø Main energy reserve in animals

Ø Very abundant in muscle and liver cells

Ø Highly branched chains of glucose monomers

Lipids Ø Very diverse group with diverse functions/ energy, hormones, ….

Ø No typical monomers or polymers

Ø Fats, Phospholipids, Waxes and Steroids Ø Hydrophobic: they do not mix well with water

C, H, O

Many lipids incorporate fatty acids Fatty Acid: Long hydrocarbon chain with a carboxyl group

Lipids

Saturated vs. Unsaturated Fatty Acids

Fats/ Glycerol with one, two or three fatty acids

Triglyceride

Hydrogenated Oils and Trans Fats Ø Created in an industrial process that adds hydrogen to unsaturated

fats (breaking the double bonds) Ø Associated with cardiovascular diseases: Plaque build up within

the walls of blood vessels

Read the labels

Phospholipids/ lipid with a phosphate group

Ø Phospholipids make a bilayer in an aqueous solution

Ø Major component of cell membranes

Waxes Ø Complex, varying mixture of lipids with long

fatty acid tails bonded to alcohols or carbon rings

Ø Molecules pack tightly, so waxes are firm and water-repellent Ø Plants secrete waxes to restrict water loss and

keep out parasites and other pests

Steroids/ no fatty acid tails Carbon skeleton contains four fused rings

Cholesterol/ remodeled

Functional groups attached to the rings define the type of steroid

Proteins Molecular Tools of the Cell

Types of Proteins �  Structural (hair, feathers, spider web) � Contractile (Actin and Myosin in muscles) �  Signal (built in the membrane of nerve cells) � Hormones (Insulin) � Transport (Hemoglobin in red blood cells and

transport proteins embedded in the cell membrane) � Defensive (antibodies) �  Storage (Albumin in egg white to nourish the

embryo) � Enzymes (digestive enzymes to hydrolyze polymers

of food)

Monomers of Proteins: Amino Acids

C, H, O, N

There are 20 amino acids

Amino Acids are linked together to form a polypeptide chain through the process of dehydration synthesis

So what functional groups are always present at the ends of a polypeptide chain?

NH2 COOH

Protein Structure

Ø Unique amino acid sequence specific to each protein

Primary

Protein Structure Secondary polypeptide chain that forms twists and folds/ hydrogen bonds between amine and carboxyl groups

Protein Structure

Ø More folding and coiling of the helices and sheets by interactions between the R groups

Tertiary

Ø It determines the function of the protein

Protein Structure

Ø Association of many polypeptides (subunits)

Quaternary

Globular Proteins Fibrous Proteins

Classes of Proteins Some types of proteins aggregate into much larger structures

Protein’s Specific Shape Determines its Function

Denaturation: Proteins losing their function as a result of losing their specific three dimensional shape/ conformation

Ø Heat, salt and acidity can denature proteins by breaking the hydrogen bonds

Nucleic Acids

C, H, O, N, P

Store and transmit hereditary information

Nitrogenous bases: Adenine Guanine Thymine Cytosine Uracil

Purines

Pyrimidines

A T C G in DNA A U C G in RNA

The Monomers of Nucleic Acids: Nucleotides

Adenosine Triphosphate ATP (a nucleotide)

base (adenine)

phosphate groups

Energy currency of the cell

Nucleic Acids

A nucleic acid polymer is built from its monomers by dehydration synthesis

Nucleic Acids

Ø DNA (Deoxyribonucleic Acid)

Ø RNA (Ribonucleic Acid)

Two main types:

Differences between DNA and RNA DNA

Ø Double Helix

Ø ATCG

Ø Deoxyribose sugar

RNA

Ø Single strand

Ø AUCG

Ø Ribose sugar