Section 5, Chapter 2Organic molecules

Proteins

Proteins have many functions:

Proteins provide structural material.

They are a source of energy.

Some act as chemical messengers (hormones, neurotransmitters).

Many proteins are receptors.

Most enzymes are proteins.

Synthesis reaction involving an enzyme

Enzymes catalyze reactions (increases rate), but are not consumed by the reaction (reusable).

Proteins: enzymes

Proteins: amino acids

All amino acids consists of:An amino group (-NH2)

A Carboxyl Group (-COOH)

A single Carbon atom

An “R” group (R = rest of the molecule)1 of 20 possible “R” groups = determines amino acid

Amino group Carboxyl group

R groupAmino Acid

20 amino acids determined by 20 possible “R” groups

Peptide BondsAmino Acids are joined by peptide bonds

Dipeptide = 2 amino acids joined by peptide bond

Polypeptide = several amino acids joined by peptide bond

Peptide bond (red) joins two amino acids.

Dipeptide: two amino acids joined together

Polypeptide: several amino acids joined together

Primary structure is the amino acid sequence of a polypeptide chain

A protein’s shape, or conformation, determines its function. Therefore, it’s important to understand a protein’s shape at 4 levels.

4 Levels of Protein Structure

Secondary Structure Shapes within local regions of polypeptides Includes coils (alpha helix) & folds (pleated sheets) Secondary structures are stabilized by Hydrogen bonding.

Red dots indicatehydrogen bonding

4 Levels of protein structure

Tertiary Structure• includes the three-dimensional folding of a polypeptide

•The tertiary structure is the highest level for proteins consisting of just one polypeptide.

4 Levels of protein structure

Quaternary Structure• The quaternary structure is the three-dimensional shape of proteins consisting of two or more polypeptides

4 Levels of protein structure

Hemoglobin = protein with 4 polypeptide chains

Example of a protein

4 Levels of protein structure

ConformationComplex 3 dimensional fold of a protein

Conformation determines a protein’s function

DenatureTreatment that alters the shape of a protein to make it nonfunctional

Heat, pH changes, radiation, certain chemicals may denature proteins

Protein Structure

Deoxyribonucleic Acid (DNA)Double stranded polynucleotide

Ribonucleic Acid (RNA)Single-stranded polynucleotide

Nucleic acids: overview

Nucleic AcidsIncludes DNA and RNAGenetic informationConsists of monomers, called nucleotides

RNAContains the sugar ribose (ribonucleic acid)RNA is a single-stranded nucleic acid.Transcribes DNA for protein synthesisRNA also may act as an enzyme

DNADNA contains a sugar, called deoxyribose (deoxyribonucleic acid)Double-stranded helixEncodes genetic information for protein synthesis.

NucleotidesNucleotides are the monomers of Nucleic Acids

3 Components of a Nucleotide5 Carbon Sugar (S)Nitrogenous Base (B)Phosphate Group (P)

RNASugar = ribose

DNASugar = deoxyribose

RNASingle polynucleotide strand

DNA

2 polynucleotide strands stabilized by Hydrogen bonds Strands are anti-parallel

H bonds

Antiparallel

Summary of organic compounds

end of section 5, chapter 2