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1Proteins

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Proteins

MultipurposemoleculesAP Biology2clockwise:Rubisco most important protein on the planet?Hemoglobin a red blooded protein :-)Collagen strings you togetherGrowth Hormones working hard in you right now!3Types of questionsRIGHT THERE ( The answer is easy to find and the words used to make the question are also in the answer.)

THINK AND SEARCH ( The answer is in the text or your notes but harder to find. The words to the question and the answer are not in the same sentence.)

AUTHOR AND YOU (Take what the author or teacher tells you and connect it to what you know.)

SYNTHESIS (Take what you have learned and put it together with other ideas and what you know.4Proteins Most structurally & functionally diverse group of biomoleculesFunction:involved in almost everything enzymes (pepsin, polymerase, etc.)structure (keratin, collagen)carriers & transport (membrane channels)receptors & binding (defense: antibodies) contraction (actin & myosin)signaling (hormones: insulin)storage (bean seed proteins)4Storage: beans (seed proteins)Movement: muscle fibersCell surface proteins: labels that ID cell as self vs. foreignAntibodies: recognize the labelsENZYMES!!!!5

ProteinsStructure:monomer = amino acids20 different amino acids polymer = polypeptideprotein can be one or more polypeptide chains folded & bonded togetherlarge & complex moleculescomplex 3-D shape

Rubiscohemoglobingrowthhormones56Amino acidsStructure:central carbon amino groupcarboxyl group (acid)R group (side chain)variable groupconfers unique chemical properties of the amino acidNHHCOH||OR|C|H67Nonpolar amino acids

nonpolar & hydrophobicWhy are these nonpolar & hydrophobic?78Polar amino acidspolar or charged & hydrophilicWhy are these polar & hydrophillic?

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Protein structure & function

hemoglobinFunction depends on structure3-D structure twisted, folded, coiled into unique shape

collagenpepsin9HemoglobinHemoglobin is the protein that makes blood red. It is composed of four protein chains, two alpha chains and two beta chains, each with a ring-like heme group containing an iron atom. Oxygen binds reversibly to these iron atoms and is transported through blood.

PepsinPepsin is the first in a series of enzymes in our digestive system that digest proteins. In the stomach, protein chains bind in the deep active site groove of pepsin, seen in the upper illustration (from PDB entry 5pep), and are broken into smaller pieces. Then, a variety of proteases and peptidases in the intestine finish the job. The small fragments--amino acids and dipeptides--are then absorbed by cells for use as metabolic fuel or construction of new proteins.

Collagen Your Most Plentiful ProteinAbout one quarter of all of the protein in your body is collagen. Collagen is a major structural protein, forming molecular cables that strengthen the tendons and vast, resilient sheets that support the skin and internal organs. Bones and teeth are made by adding mineral crystals to collagen. Collagen provides structure to our bodies, protecting and supporting the softer tissues and connecting them with the skeleton. But, in spite of its critical function in the body, collagen is a relatively simple protein. 10

Primary (1) structureOrder of amino acids in chainamino acid sequence determined by gene (DNA)slight change in amino acid sequence can affect proteins structure & its functioneven just one amino acid change can make all the difference!

lysozyme: enzyme in tears & mucus that kills bacteria10Sickle cell anemia: 1 DNA letter changes 1 amino acid = serious diseaseHemoglobin mutation: bends red blood cells out of shape & they clog your veins.11Sickle cell anemia

11glutamic acid is acidic & polarvaline is non-polar = tries to hide from water of cell by sticking to another hemoglobin molecules.12

Secondary (2) structureLocal foldingfolding along short sections of polypeptideinteraction between adjacent amino acidsH bonds between R groups-helix-pleated sheet12Its a helix or B sheet within a single region. Can have both in one protein but a specific region is one or another13Secondary (2) structure

Lets go to the video tape!(play movie here)1314

Tertiary (3) structureWhole molecule foldingdetermined by interactions between R groupshydrophobic interactionseffect of water in cellanchored by disulfide bridges(H & ionic bonds)Lets go to the video tape!(play movie here)14How the whole thing holds together15Quaternary (4) structureMore than one polypeptide chain joined together only then is it a functional proteinhydrophobic interactionshemoglobincollagen = skin & tendonsLets go to the video tape!(play movie here)

15Structure equals function wonderfully illustrated by proteins

Collagen is just like rope -- enables your skin to be strong and flexible.

16Protein MobileTwo pieces of paper, different color patterns17Result: 5 strips each. Leave one straight, write primary on back and peptide bondThis is your first level of your mobile. All the rest of the strips you will fold/twist. (wait, next slide)18Leaving one strip at the top unfolded,Now twist one set of strips around your finger to form a alpha helix, and another set fan fold to create a pleat.More red colors = alpha helixMore blue colors = beta pleatAll of rest of strips (4 each, fold accordingly)Alpha helixTwist around fingerBeta PleatFan fold19Leave one of each folded, write secondary and peptide on back. All of rest of strips:Wrap around themselves (Tertiary)Alpha helix: match red to yellow or orangeBeta pleat: match blue to green or purple.

Staple. 20Leave on of each wound up to itself as tertiary. Write Polypeptide on each of them. Remaining strips, Glob them together, staple and label Quaternary and proteinStaple bluest part to orangest part21

Protein structure (review)1234aa sequencepeptide bondsR groupsH bondsR groups hydrophobic interactions, disulfide bridgesdeterminedby DNAmultiplepolypeptideshydrophobic interactions21sequence determines structure andstructure determines function.Change the sequence & that changes the structure which changes the function.22Denature a proteinUnfolding a proteindisrupt 3 structure pH salt temperatureunravels or denatures proteindisrupts H bonds, ionic bonds & disulfide bridgesdestroys functionality Some proteins can return to their functional shape after denaturation, many cannot

In Biology,size doesnt matter,SHAPE matters! 22Example: Eggs: Cooking an egg permanently denatures the proteins.Lets build some Proteins!

AP Biology23Any Questions??AP Biology24