Chapter 3 Biology Sixth Edition Raven/Johnson (c) The McGraw-Hill Companies, Inc.

The Chemistry of Carbon Because carbon only has 4 electrons in its outer shell, it can attach to four separate molecules Organic molecules consisting of only C and H are called hydrocarbons. Organic molecules contain C and H

Hydrocarbon chains can have functional groups that cause the macromolecule to behave in a certain way. Carboxyl Group: -COOH  -COO¯ + H +

Making and Breaking Macromolecules Macromolecules (polymers) are formed from smaller building blocks called monomers. Macromolecules are formed by dehydration synthesis (requires energy) Macromolecule bonds are broken by hydrolysis (releases energy in bonds)

Energy must be used to build macromolecules. Energy is released when macromolecules are split.

Four Types of Organic Macromolecules Proteins Nucleic Acids Lipids Carbohydrates

Protein Types and Function Enzyme Catalyst –Facilitate chemical reactions Defense –Body’s hormone and immune system Transport –Specific small molecules and ions Support –Structural roles Motion –Aid in muscle movement Regulation –Intercellular messengers

Protein Building Blocks Proteins are made of linked amino acids Only 20 amino acids available Sequence of amino acids are unique for each protein

C NH 2 COOH HR Structure of Amino Acids (Acidic Group) (R or Functional Group) (Amino Group) (Hydrogen Group)

Five Groups of Amino Acids Nonpolar Polar Aromatic Ionizable Special Structural Property

Contains –CH 2 or –CH 3 Contains –O or only H

Contains carbon ring that has alternating single and double bonds

Contains acids or bases

Special function

Amino acids are linked by peptide bonds: Dehydration synthesis

Primary Structure - Amino Acid Sequence Secondary Structure - Folding due to hydrogen bond Motifs – Characteristic secondary structure (    creates a fold or crease)

Driven into its tertiary structure by hydrophobic reactions with water, disulfide bonds, and other ionic and covalent bonds -remember: some amino acids are nonpolar. Two or more polypeptide chains associate to form a functional protein Domain – structurally independent functional unit subunits

Protein Structure Viewed at Six Levels Amino acid sequence (primary structure) Coils and sheets (secondary structure) Folds or creases (motifs) Three-dimensional shape (tertiary structure) Functional units (domains) Individual polypeptide subunits associated in quaternary structure

Chaperonins – proteins that help other proteins fold correctly

Primary structure determines tertiary structure!

Nucleic Acids Nucleic acids are polymers of nucleotides. Examples include Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA). All nucleotides have: 1.) nitrogenous base 2.) pentose sugar -deoxyribose -ribose 3.) phosphate group

Fig Fig A chemical difference between DNA and RNA Nucleotides (monomer) connected by phosphodiester bonds to form nucleic acid (polymer).

Hydrogen bonds between base pairs gives DNA its characteristic double- helix shape.

Purines always bond with a pyrimidine, and with DNA it is always: A-T; G-C Adenine Guanine Cytosine Thymine Uracil DNA vs RNA: RNA has Uracil instead of Thymine H instead of CH 3

DNA – double stranded, contains thymine, #2 C attached to H RNA – single stranded, contains uracil, #2 C attached to OH

Nucleotide bases also play an important part in other molecules crucial to life: ATP, NAD, and FAD. Adenosine triphosphate

Lipids - triglycerides, phospholipids, steroids Lipids serve as long-term energy stores in cells, form membranes, and serve as hormones and insulation. Lipids contain more energy per gram than any other biological molecule. Lipids are nonpolar, thus they do not dissolve in water (hydrophobic). All lipids are insoluble in water!!

Structure of Triglycerides unsaturated saturated functional group –COOH Fatty Acids: long chains of hydrocarbons with an acidic functional group –COOH Saturated: no double bonds between carbons, “saturated with hydrogen”, higher melting point than unsaturated Unsaturated: has one or more double bonds between carbons Dehydration or

Solids (butter) at room temperature; fatty acids can align close to each other Liquids (corn oil) at room temperature; double bonds prevent fatty acids from aligning close to each other

Phosphate Phospholipids consist of: Glycerol 2 Fatty acids Phosphate group Polar end Non- Polar end

Contains a phosphate group Cellular membranes

Terpenes – long chain lipids; components of many biologically important pigments All steroids characteristically have four carbon rings.

Carbohydrates Carbohydrates contain C, H, and O and serve as quick energy and short-term energy storage. Monomers of carbohydrates are the monosaccharides (simple sugars)

6-Carbon sugars – primary energy storage

Empirical formula for a 6-C sugar: C 6 H 12 O 6 Glucose is metabolized by cellular respiration

Dehydration synthesis – consumes energy Hydrolysis splits the disaccharides and releases energy ‘double sugars’ – important in sugar transport

Your taste buds can taste the difference! Same empirical formula (C 6 H )– different arrangement.

Energy storage for plants Energy storage for animals

Structural polysaccharide – chief component of plant cell walls Modified form of cellulose with a nitrogen group added to the glucose units. Structural building material in insects, many fungi, and certain other organisms.

The End.