Molecules of Life Dr. Anderson GCIT

Cells and Molecules Atoms Molecules Organic Molecules Polymers Carbohydrates Lipids Proteins Nucleic Acids

Molecules Other important molecules to life O2 CO2 Ions Ca, I, Cl-, Fe+, Na+, K+, etc. Why are these important?

Bonding Covalent Bonds Ionic Bonds Electrons are shared between atoms Electrons are “donated” to atoms depending on their electronegativity

Covalent Bonds Covalent bonds are much stronger and difficult to break CAN be manipulated in the body using enzymes, which lower the activation energy needed for chemical reaction to occur Creating bonds (building molecules) – anabolism Breaking bonds (splitting molecules) - catabolism

Molecular Characteristics Polar Covalent – unequal sharing of electrons around the molecule Results in slightly positive or negative “ends” Examples? Non-polar Covalent– equal sharing of electrons around the molecule Equal distribution of charge around the molecule

Ionic Bonds The “donation” of an electron changes the charges between molecules Separation of these charges and their recombination leads to electric charge! How can this happen? Where does this happen in the human body?

Ionic Bond Disassociation In water, ionic bonds can be separated so that the individual ions (atoms) go into solution Examples? NaCl Na+ + Cl-

Organic Molecules Contain carbon Carbohydrates Lipids Proteins

Carbohydrates Made of C, H, and O Sugars Starches Monosaccharides Disaccharides Starches Polymers of sugars Monomer Polymer

Lipids Made of C, H, O How are fats different from carbohydrates? Saturated Unsaturated Triglyceride

Special Lipids Phospholipids Steroids Eicosanoids Make up cell membranes Steroids Hormones, cholesterol Eicosanoids Immune responses, blood clotting, etc.

Proteins Made of H, C, N, O, S Polymers of amino acids Extremely complex!! Examples? Shape dictates function in proteins Can protein molecules change shape?

Primary Structure Simple peptides – simple “string” of amino acids”

Secondary Structure Alpha-helices Beta-pleated sheets Bonds between the “chains” form these structures Beta-pleated sheet

Tertiary Structure Helices and Sheets cause a complex structure Globular proteins What affects the shape?

Quaternary Structure Multiple polypeptide structures combine to form a functional protein

Protein Shape What affects the shape of a protein? What does the shape of a protein affect? “Lock and Key” - enzymes

Enzymes Protein molecules that catalyze chemical reactions Can either synthesize or decompose molecules

Steps in Enzymatic Action 1. The enzyme’s active site bonds with the substrate to make the enzyme-substrate complex 2. Enzyme undergoes internal rearrangements to initiate the reaction 3. Products are formed and released

Examples of Enzymes - Catabolism Often end in “–ase” Lipase Protease Fructase Enzyme Breaks down polymers into monomers to be used by cells in the body! (Catabolism)

Examples of Enzymes - Anabolism Dehydration Synthesis Water is produced when bond is made

Nucleic Acids DNA RNA Proteins The “blueprint of life” – the order of monomers in the DNA molecule is the key DNA and RNA – polymers of sugar, nitrogen bases and phosphates This is the core of to the central dogma of biology DNA RNA Proteins

DNA (Deoxyribonucleic Acid)

RNA Created from DNA Also a polymer Acts as a messenger to encode genetic information for protein synthesis

Important Biological Chemical Reactions Synthesis – combination of smaller molecules or atoms into larger molecules Decomposition – Breaking a large molecule into smaller ones Exchange Reactions – parts of molecules exchanged with others

Synthesis Reaction (Dehydration Synthesis) A + B AB e.g. - Sugar into starch

Decomposition Reaction Hydrolysis – water is used to separate amino acids from proteins (peptides) Protein Ala Lys Arg Phe Trp Leu H2O + enzyme Free amino acid

Exchange Reactions Molecular Partners are “swapped” E.g. Photosynthesis CO2 + H2O C6H12O6 + O2 Solar Energy What is the opposite of this reaction?

What affects chemical reaction rates? Temperature – increases in temperature cause an increase in molecular motion, leading to faster reactions The amount of reactants – reaction can be limited because there are not enough raw materials pH – highly acidic or alkaline (basic) environments can increase or decrease reaction rates, depending on the specific reaction

Example – Enzymes and pH Where is the enzyme activity highest? Where is it lowest? Why?

Temperature Limited Reaction Asymmetrical activity curve Why asymmetrical?

Reactant-Limited Reactions In this example, an enzyme is mixed with the substrate that it breaks down. What is the limiting factor here?

ATP – Rechargeable Cellular Battery Energy is stored in the phosphate bonds of ATP When bonds are broken, (ATP ADP) energy is released When bonds are made (ADP ATP) energy is stored