Macromolecules

Nucleic Acids & Proteins

Objectives for Today

• Nucleic Acids (NA) • DNA • RNA • Proteins NA code for proteins Proteins ‘read’ NA

The Genetic Code

• Every cell in your body, whether it’s a hair cell, a white blood cell or bone cell, contains the EXACT same genome • Genome: the entire genetic sequence of a living organism • So why do cell’s look different? Because they are READING different parts of the book (genome) • The complexity of an organism is based in no way on how long it’s genetic code is

Central Dogma of Biology

Central Dogma of Biology Example

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You work out and your muscles are becoming oxygen deprived (forming lactic acid) You need hemoglobin to help transport oxygen to these muscles via your red blood cells!

Specialized proteins hurry to your DNA and help ‘transcribe’ the hemoglobin gene to take it to another location outside the nucleus The result is a messenger RNA that provides instructions straight from the DNA on how to ‘make’ hemoglobin Other proteins ‘translate’ the mRNA instructions into another form – an actual 3D protein People who have a mutation in the hemoglobin gene have sickle cell anemia 

Sickle Cell Anemia

As recently as 1973, the average lifespan for people with sickle cell disease was only 14 years. Currently, life expectancy for these patients can reach 50 years and over.

Nucleic Acid Structure

• Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA) • All nucleic acids have ‘ends’ defined as 5’ and 3’ that are important in directionality of forming DNA and RNA

DNA

• • • These 5’ and 3’ ends are important during the processes of DNA synthesis & transcription DNA is always built & read 5’ to 3’ by transcriptional machinery DNA is made up of a “sugar phosphate” backbone and the nitrogenous bases that are attached

RNA

• Unlike DNA, most RNA is • single-stranded • MUCH shorter • Very unstable • RNA can fold on itself creating loops and hairpins, especially non-coding RNA

CONCLUSION on Nucleic Acids

• NUCLEIC ACIDS ROCK!

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Nature

vs. Nurture • They are the nature part of who we are!

So what does the genetic code code for?

• PROTEINS!

• Lipids & carbohydrates come from the food we eat or are synthesized in our bodies from precursers • Our DNA codes has roughly 26,000 genes • Less than 3% of our genome actually codes for something…WHAT!?

Importance of Proteins

• • Proteins play many roles in our body • All enzymes are proteins!

• Catalyze chemical reactions • Involved in all steps of metabolic pathways Many hormones are proteins • • Oxytocin Human growth hormone

Monomer of Proteins

• Amino acids • They all have an alpha carbon, an amino group, a carboxylic acid group and a differing ‘side chain’ (R) • There are 20 amino acids • The “R” group gives amino acids their properties • Interactions of R groups determines final protein shape after folding

R-Groups

• The R group of an amino acid can be categorized by chemical properties • Hydrophobic – hate water • hydrophilic - love water • Ionic • The interactions of these R groups determine structure and function of that region of the protein.

Chains of Amino Acids

• Amino acids are held together by peptide bonds • Peptide bonds are formed via a dehydration reaction between the amino group of one AA and the carboxyl group of the adjacent one • Chains of amino acids are called polypeptides • Poly = many

Structures of Polypeptides

• • • • • The structure of a polypeptide determines it’s function Primary structure: the sequence of the amino acids Secondary structure: structures within a short region of the sequence • Alpha helices • Beta sheets Tertiary structure: folding of the protein Quaternary: multiple subunits assembled into final structure

Green Fluorescent Protein

• First isolated from jellyfish and used as a transgenic gene • Used as a reporter gene to study regulatory part’s of DNA

Denaturation of Proteins

• When a protein loses it’s shape, it cannot function anymore  • Heat • Chemicals • pH change • Radiation

Folding of Proteins

• • • • The folding of a protein (determined by R group interactions) is absolutely vital for function Special proteins called chaperone proteins have the sole job of helping proteins fold after they come off the assembly line (on the ribosome) Mis-folded proteins from gene mutations of environmental factors can cause disease Neurological diseases are especially associated with mis-folded proteins • • variant Creutzfeldt-Jakob disease Alzheimer's

Variant Creutzfeldt-Jakob disease (vCJD)

• Human version of mad cow disease (humans cannot get MCD) • • You can get it if you eat the brain or spinal cord of cow with MCD Accumulation of prion proteins in the brain • Hard for body to remove them because of the blood-brain barrier