Macromolecules: proteins & nucleic acids Building Blocks of Life

PROTEINS Most structurally/functionally diverse macromolecule group Involved in almost everything: enzymes : pepsin, amylase, structure : keratin, collagen carriers & transport : hemoglobin, aquaporin cell communication : insulin, hormones, receptors defense : antibodies movement : actin & myosin storage : seed coat proteins

monomer = amino acids 20 different amino acids polymer = polypeptide amino acids bound together with covalent peptide bonds protein can be one or more polypeptide chains folded & bonded together large & complex 3D molecules hemoglobin H2OH2O Dehydration forms peptide bonds Structure

Amino acids Central C & an H Functional groups: amino group carboxyl group (acid) R group (side chain) Variable; different for each amino acid confers unique chemical properties to each amino acid —N——N— H H C—OH || O R | —C— | H

R group determines molecule charge charge affects polypeptide folding Ex: a point mutation in hemoglobin : > changes the amino acid, > changes the charge > changes the protein shape > deforming the cell R Group

Building proteins Peptide bonds Covalent; via dehydration, Between NH 2 (amine) of one amino acid & COOH (carboxyl) of another C–N bond formed peptide bond dehydration synthesis H2OH2O

Primary (1°) structure Sequence of amino acids in chain amino acid sequence determined by gene (DNA) change in sequence can be a change in charge which can cause change in protein structure and function sequence -> structure -> function

Secondary (2°) structure Folding and coiling along short sections of polypeptide (local folding) H bonding between R groups of adjacent amino acids  -helix  -pleated sheet

Tertiary (3°) structure Interactions between distant amino acids hydrophobic interactions cytoplasm is aqueous; nonpolar amino acids organize away from water H bonds, ionic bonds, disulfide bridges Finally, a Protein

Sulfur containing amino acids disulfide bridges covalent bonds between sulfhydryl groups (SH) stabilizes 3-D structure Keratin protein in hair has many disulfide bridges – keeps its shape

Quaternary (4°) structure 2+ polypeptides bonded and folded together Collagen skin & tendons Hemoglobin Fe containing protein that carries O 2 in blood

Recap: protein structure amino acid sequence peptide bonds 1° determined by DNA R groups H bonds R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3° multiple polypeptides hydrophobic interactions 4° 2°

Protein denaturation Unfolding a protein disrupt bonds & bridges temperature pH salinity alters shape destroys functionality many cannot return to functional shape

Nucleic Acids Information storage

protein DNA The genetic material stores information Genes = template for proteins DNA  RNA  proteins  trait transfers information template for new cells template for next generation to trait

Structure monomer = nucleotide adenine, guanine, thymine, cytosine, uracil Types RNA (ribonucleic acid) single helix, ribose, uracil DNA (deoxyribonucleic acid) double helix, deoxyribose, thymine RNA DNA Examples

Nucleotides 3 parts nitrogen base pentose sugar (5C) ribose in RNA deoxyribose in DNA phosphate (PO 4 ) group I’m the A,T,C,G or U

Types of nucleotides purines double ring N base adenine (A) guanine (G) pyrimidines single ring N base cytosine (C) thymine (T) uracil (U) Purine = AG “Pure silver”

Nucleic acid Dehydration synthesis -> covalent bond aka phosphodiester between hydroxyl & phosphate groups polymer ‘backbone’

Base Pair rule H-bonds between DNA nucleotide N-bases Base-pair rule: purine pairs with pyrimidine A :: T 2 H bonds G ::: C 3 H bonds

Copying the Code o DNA helices are complementary via base-pair rule can replicate entire molecule o To reproduce cell via mitosis o To make gametes via meiosis “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” James Watson & Francis Crick 1953

. o Can build RNA complement aka transcription of genes for eventual translation into protein Copying the Code