Macromolecules Part 3 Proteins

Proteins!

Functions of Proteins Structural support Storage Transport Cellular communications Movement Defense against foreign substances

Proteins Monomer: amino acids Polymer: polypeptide chains (proteins) Amine (NH2) and carboxyl (COOH) groups attached to carbon Only thing different is side chain…R-group Polymer: polypeptide chains (proteins) Link between monomers is called: polypeptide bond Made by a dehydration reaction (between amine group of one aa and carboxyl group of another aa) STRUCTURE of A.A. Amino group on one end (-NH2) Carboxyl group on one end (COOH) Hydrogen R-group/side chain (changes)-------- ALANINE Proteins account for more than 50% of the dry mass of most cells

Polypeptide bonds DEHYDRATION!!!

Some famous proteins… Essential components of cell membranes Oxygen-carrying pigment hemoglobin (hemoglobin) Antibodies which attack and destroy invading microorganisms

Protein Structure the association of the polypeptide chains Primary structure 1’ Order of amino acids in a polypeptide chain Secondary structure 2’ Polypeptide chain folds because of interactions between amino acids HYDROGEN BONDING Tertiary Structure 3’ Gives proteins 3-D shape VERY IMPORTANT to function of protein Beta pleated sheets and alpha helices fold based on interactions between R-groups of a.a. Hydrogen bonds, polar/non-polar interactions, acid/base interactions, disulfide bonds, van der Waals forces Quaternary Structure 4’ the association of the polypeptide chains some proteins contain more than one polypeptide chain Each polypeptide chain in the protein is called a subunit Two or more subunits come together for a specific function HEMOGLOBIN On Red blood cells Its shape allows RBCs to carry oxygen all around your body!

Primary Structure Sequence of AA in a long polypeptide chain AA= letters of alphabet Sequence of AA= arrangement of letters to make words HUGE amount of different primary structures Changing ONE AA is polypeptide chain GREATLY changes the properties of the polypeptide chain and PROTEIN

Three possible 2o structures Determined by order R-groups No particular arrangement Alpha helix Polypeptide chains that coil tightly Beta pleated sheet Looser, straighter shape created by hydrogen bonds Secondary Structure The order of AA in polypeptide chain determine interactions between functional groups of AA Functional groups interact via HYDROGEN BONDS Attraction between oxygen in the –CO end of one AA and the hydrogen in the –NH end of another AA H-bond easily broken Change pH and change Temperature

Tertiary Structure Secondary structure gets coiled and folded Precise 3D shape Folding is determined by interactions between R-groups Hydrogen bonds Tryptophan Arginine Asparigine Disulphide bonds Between 2 cystine molecules Ionic bonds b/t R groups containing amine and carboxyl groups Hydrophobic interactions b/t R groups that are non-polar (hydrophobic)

Quaternary Structure Proteins are made up of multiple polypeptide chains, sometimes with an inorganic component (for example, a haem group in haemoglogin) Prosthetic Group (inorganic component of protein) These proteins will only be able to function if all subunits are present Made by same bonds found in tertiary structure Interactions between R-groups Hydrogen bonds Tryptophan Arginine Asparigine Disulphide bonds Between 2 cystine molecules Ionic bonds b/t R groups containing amine and carboxyl groups Hydrophobic interactions b/t R groups that are non-polar (hydrophobic)

Denaturation Unraveling/unfolding of protein Why would this be a problem? When protein loses its 3-D shape and thus its specific function Caused by: Unfavorable changes in pH, temperature or other environmental condition Disrupts the interactions between side chains and causes loss of shape Examples: Frying an egg Straightening your hair

Why do you think we can compare it to this? Enzymes! Why do you think we can compare it to this?

ENZYMES!!! A special type of protein…??? In order for a protein to work at its SPECIFIC JOB, it must have….??? Because an enzyme is a protein, it MUST have….??? Can any key unlock the door to your house??? Can any substrate/reactant fit into a specific enzyme? How many different enzymes do we have???

Proteins Biological catalysts that speed up the rate of chemical reactions They help make products faster! Never used up! “Matchmaker” ENZYMES!!!

Enzymes in Action Enzymes speed up chemical reactions that take place in cells They DECREASE ACTIVATION ENRGY The energy needed to get the reaction started (or energy needed to start making product)

break up hydrogen peroxide Catal-ASE is an enzyme that helps break up hydrogen peroxide

Proteins: Enzymes What is a chemical reaction? Do they happen on their own? If we stare at the piece of paper, are we going to be able to make the oxygen molecules in the air collide with the cellulose in the paper? What do we need to do? What are reactants? What are products?

Factors that Effect the Rate of Reactions Temperature Hot Breaks bonds that give proteins its tertiary structure DENATURES Cold Slow down chemical reaction (formation of enzyme substrate complex) pH Acids and bases produce OH- and H+ ions too many ions are present, the enzyme may be denatured (twisted and pulled so out of shape that it can no longer function) Inhibitors Non-competitive react with portions of the active site, changing of its shape Allosteric Inhibitors Change shape of the enzyme Attach to regulatory site (not active site) and change the shape of the entire enzyme (specifically the active site) Competitive look like substrate, bind to active site, but do not make the intended product

Examples of endothermic reactions: Melting of ice absorbs energy Dissolving ammonium nitrate in water( the essence of commercial cold packs) PHOTOSYNTHESIS Examples of exothermic reactions: Digestion of food releases energy (CELL RESPIRATION) All combustion reactions (fires) C + O2 CO2 + E Adding an alkali metal to water 2 Na + 2 H2O 2 NaOH + H2 + E Condensation of water Explosion of bombs

Endothermic Reactions the reactants have less potential energy than do the products. Energy must be input in order to raise the particles up to the higher energy level. Energy + A + B --> AB

Exothermic Reactions the reactants have more potential energy than the products have. The extra energy is released to the surroundings.   A + B --> AB + Energy

Enzymes Substrate Molecule/compound that attaches to enzyme Catalyst Anything that speeds up the rate of a reaction by lowering the ACTIVATION ENERGY Activ. E: energy required for a chem. Rxn to start making products used to regulate the rate (speed) of chemical reactions Protein that helps speed up a reaction that occurs in a biological system Name of enzymes end in –ASE all enzymes are proteins, but not all proteins are enzymes each chemical reaction in an organism requires its own specific enzyme enzymes are never changed by their reactions! Substrate Molecule/compound that attaches to enzyme Active Site Specific location on enzyme for substrate to attach Where the enzymatic reaction occurs Enzyme-substrate complex When substrate binds to active site of enzyme Products molecules produced at the end of an enzymatic reaction

Acetylcholinesterase catalyzes the breakdown of the neurotransmitter acetylcholine at several types of synapses as well as at the neuromuscular junction — the specialized synapse that triggers the contraction of skeletal muscle. One molecule of acetylcholinesterase breaks down 25,000 molecules of acetylcholine each second makes possible the rapid "resetting" of the synapse for transmission of another nerve impulse.

Lock and Key Model

Class work! Label Each box! 2. 3. 4. 1. 5.

6. Class Work! Label Boxes! 7. 8. 9. 10.