Biological Molecules

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General Characteristics of Biological Molecules

• Carbon based• Interact by means of functional groups• Assembled or disassembled by adding

or removing water

Carbon and Biological Molecules

• Able to form 4 stable bonds• Organic Compounds – contain carbon• Few inorganic compounds contain carbon

C

Functional Groups• Group with distinct chemical properties

• Carbon is skeleton holding groups of atoms

• Chemical reactions within organisms involve transfer of a functional group

• Macromolecules –many functional groups

Changing Molecules• Assembling molecules

– Growth and repair– Producing molecules essential for

chemical reactions to take place

• Disassembling molecules– Digestion – Providing molecules that can enter cells

Assembly: Dehydration Synthesis

• Monomers = building blocks

• Monomers are linked with covalent bonds

• Polymers = chain-like molecules

Dehydration Synthesis• One molecule of

water is removed

• Two monomers are joined– One loses

hydroxyl group– Other loses

hydrogen

Disassembly: Hydrolysis

• Hydrolysis is opposite of dehydration

• Covalent bonds broken with addition of H2O

• Energy in bond is released

Major Classes of Biological Molecules

Carbohydrates• Contain C,H, & O• H:O = 2:1• Primary role is for energy• Breaking bonds releases energy

Glucose

Carbohydrate Example: Glucose

Monosaccharides• Simplest carbohydrates• Individual sugar molecules

Disaccharide• Monosaccharides linked together• Less readily broken during transport

Polysaccharides• Long polymers of sugars• Insoluble• Called complex carbohydrates

Common Polysaccharides

• Starches– Stored energy in

plants

• Glycogen– Animal energy

storage

Some Carbohydrates are Used for Structure

• Cellulose – plant cell wall material• Chitin – in insects, fungi

Lipids• H:O ratio higher

than 2:1

• Not dissolved in water

• Categories of lipids– Oils, fats & waxes– Phospholipids– steroids

Fats• Non-polar & insoluble• Work well for storage• More energy than equivalent

carbohydrates

• Two types of subunits– Glycerol – Fatty acids

Triglyceride• Molecule with 3 fatty acids• Includes most dietary fat

Triglycerides • Saturated – carries as many H as possible

Triglycerides • Unsaturated – double bond replaces H• Polyunsaturated – more than 1 double bond

Differences in Fats & Oils• Polyunsaturated

– Plant oils– Fish oils

• Saturated– Animal fats

• There are exceptions

Waxes• Chemical backbone differs from fats & oils

• One carbon chain

• Water resistant

Phospholipids• Phosphate group replaces a fatty acid • Key component of cell membrane

Steroids• With 4 carbon rings• Important for membranes

Proteins• Transport other molecules• Provide for muscle contraction• Help protect body• Play role in nerve transmission• Control growth• Serve as enzymes• Act as chemical messenger

Protein Structure• Chain of amino acids• Polypeptide bond

Protein Synthesis & Hydrolysis

Protein Levels of Structure• Primary structure = amino acid sequence

• Secondary structure = shape– Coils– Folds

• Tertiary structure = complex shape caused by hydrogen bonds

Protein Function• Dependent upon 3-dimensional structure• Can be degraded by heat

Nucleic Acids• Composed of nucleotides• Stores information

Forms of Nucleic Acid• DNA = deoxyribonucleic acid• RNA = ribonucleic acid

End Chapter 4