Biological Molecules

Biological Molecules

• Life is carbon-based chemistry • Hydrolysis and Synthesis of Biological Molecules • Carbohydrates • Lipids • Proteins • Nucleic Acids

Life is carbon-based chemistry

•

Organic

is used to describe molecules that have a carbon skeleton and some additional hydrogen atoms • • Life is composed of organic molecules

Inorganic

molecules include carbon dioxide, water and all other non-carbon molecules

Life is carbon-based chemistry

• The tremendous diversity of organic molecules is due to the diverse

functional groups

that attach themselves to common carbon skeletons: • Hydrogen (-H) • Hydroxyl (-OH) • Carboxyl (-COOH) • Amino (-NH 2 ) • Phosphate (-H 2 PO 4 ) • Methyl (-CH 3 )

Hydrolysis and Synthesis of Biological Molecules

• Small organic molecules are used as

subunits

to synthesize longer molecules • The individual subunits are called

monomers

• The longer molecules are called

polymers

Hydrolysis and Synthesis of Biological Molecules

• Monomers are linked to monomers in a chemical process called

dehydration synthesis

• The –H group is removed from one monomer and the –OH group is removed from the second monomer • The two monomers join by forming a covalent bond • The –H group and –OH group bond to form a water molecule

Hydrolysis and Synthesis of Biological Molecules

• Polymers are disassembled into monomers through a process called

hydrolysis

• The polymer splits into monomers • A water molecule splits and releases a –H group and a –OH group • The –H group and –OH group bond to the monomers to complete their structure

Carbohydrates

• Contain carbon, hydrogen and oxygen in the constant ratio of 1:2:1 • Carbohydrates are “hydrates of carbon” • C 1 H 2 0 1 or CH 2 0 • All carbohydrates are either small, simple sugars or polymers of these simple sugars

Carbohydrates

Monosaccharides One sugar Disaccharides molecule Two sugar molecules Polysaccharides Many sugar molecules Glucose Fructose Galactose Sucrose Lactose Maltose Starch Glycogen Cellulose

Lipids

• Lipids contain large regions of H and C atoms joined by non-polar covalent bonds • Non-polar regions are hydrophobic • Lipids are not soluble in water • Three major groups of lipids • (1) oils, fats and waxes • (2) phospholipids • (3) steroids

Oils, Fat and Waxes

• Contain only C, H and O atoms • Composed of one or more fatty acids subunits attached to a glycerol subunit • Are straight chains: do not have ring structures • Function as source of energy

Oils, Fat and Waxes

• Fatty acid chains that have no C=C double bonds are said to be

saturated

with H atoms • Fatty acid chains that have C=C double bonds are said to be

unsaturated

with H atoms • Saturated fatty acid chains are straight • Unsaturated fatty acid chains are kinked

Oils, Fat and Waxes

• Oils are liquid at room temperature because they are unsaturated → kinks • Waxes are solid at room temperature because they are saturated → straight

Phospholipids

• Similar to structure of fats, waxes and oils except one of the three fatty acid chains is replaced by a phosphate group containing a polar functional group • The two fatty acid chains are hydrophobic • The phosphate head (being polar) is hydrophilic • Function as basic component of membranes

Steroids

• Composed of four rings of carbon fused with various functional groups • Steroids are synthesized from cholesterol • Function as hormones and components of animal cell membranes

Proteins

• Proteins are polymers of amino acid subunits • The bond between amino acid subunits is called a peptide bond (formed by dehydration synthesis) • Diversity of proteins is due to diversity of amino acids and the diverse ways amino acids arrange themselves • Proteins function as enzymes, structural components, transport proteins, energy storage, cross-membrane transport, and hormones

Proteins

• Amino acids are composed of a central C atom bonded to four different functional groups: • (1)

amino

group (-NH2) • (2) carboxylic

acid

group (-COOH) • (3) hydrogen group (-H) • (4) variable group (-R)

Proteins

• The –R group creates the diversity of amino acids • Some -R groups are small, others large • Some –R groups are hydrophobic, others hydrophilic • The type of –R group directly affects the structure of the protein

Proteins

• Proteins have four levels of structure • (1) Primary Structure: sequence of amino acids in the linear protein polymer • (2) Secondary Structure: simple repeating pattern created by hydrogen bonding between amino acid subunits • Secondary structure can be either a helix or pleated sheet

Proteins

• (3) Tertiary Structure: complex 3 dimensional shape formed by folding over of secondary structure • Tertiary structure is due to disulfide bridging between neighbouring cysteine amino acids; size of –R group; hydrophobic/hydrophilic interactions

Proteins

• (4) Quaternary Structure: due to joining together of smaller proteins in order to form a larger protein complex

Nucleic Acids

• Nucleic acids are polymers of nucleotide subunits • Nucleotides are composed of three components themselves: • (1) a five C sugar (ribose/deoxyribose) • (2) a phosphate group • (3) a N containing base

Nucleic Acids

• It is the diversity in N containing bases that creates diversity in nucleotides • It is the diversity in sugars that adds to the diversity of nucleic acids

Nucleotides

DNA (deoxyribose sugar) Adenine RNA (ribose sugar) Adenine Thymine Guanine Cytosine Uracil Guanine Cytosine

Nucleic Acids

• Nucleic acids function primarily as the molecules of heredity and the blueprint for protein synthesis (DNA and RNA) • Nucleic acids also act as intracellular messengers (cAMP), coenzymes and energy carrier molecules (ATP)