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Chapter 3 Proteins PROTEINS • A polymer made of the monomers called amino acids • 20 types of amino acids Purpose • Mostly for structure: skin, muscle, fingernails, hair Proteins • -CONTAIN C, H, O, N (always) Contain: -COOH -NH2 group (amino group) -R group What 3 groups make up an amino acid? What is the “R” group? • Variable part of the amino acid • Amino Acid Chart (handout) Amino Acid Chart Amino Acid Examples How do they differ? • alanine • glycine Peptide Bond • Formation of a peptide bond between two amino acids by dehydration synthesis Peptide Bonds: form between amino acids H Protein Bonds • peptide bond = the bond that holds amino acids together in protein molecules • dipeptide = two connected amino acids • polypeptide = 3 or more connected amino acids • So polypeptide = protein = amino acid chain Peptide Bonds: join amino acids Forming/Breaking Peptide Bonds • youtube peptide bond formation (polypeptide) Peptide Bond is a covalent bond • The four-atom functional group -C(=O)NHis called a peptide link. • Between which two functional groups join? (youtube) POLYPEPTIDE (many) Bonds Between amino acids Types of Proteins SSSCDETR • 1. structural- support (collagen, keratin, elastin)-spider silk, hair, skin, fingernails • Spider Silk Protein Youtube • CHEMISTRY OF HAIR: What level of protein folding do you see here? Type of Proteins • 2. Contractilemovement=muscles, flagella • Sliding Myofibril Youtube (2:59) • Youtube flagella and cilia (3:12) • Sperm flagella youtube (34 secs) • Cilia Youtube (11 secs) Types of Proteins • 3. Storage proteins-such as ovalbumin (in eggs), seeds, nuts Type of Proteins • 4. Defensive- antibodies • Antibodies Youtube (2:40) • Specific Immunity Youtube (1 min) • Newly Developed Antibody Youtube (54 seconds) Types of Proteins • 5. Transport - include hemoglobin that carries iron (attract oxygen in red blood cells) • Hemoglobin oxygen Transport Youtube (3:09) • Hemoglobin Youtube (56 seconds) Iron in red Oxygen binds to the iron Types of Proteins 6. Signal - Hormone - chemical messengers (EX: insulin thyroxin) Insulin-Glucose Signaling (4:10) 0 Type of Proteins • 7. Enzymes- speed up chemical reactions • Lactase, Sucrase - • Enzyme Youtube (46 secs) • The Role of Enzymes Youtube (3:35) Type of Proteins • 8. Receptor Proteins • Intercellular communication • Bind to specific proteins (like hormones) -Receptor Protein animation -McGraw-Hill receptor channel sodium channel youtube -Secondary Receptor Protein (48 secs) LEVELS OF FOLDING OF PROTEINS • The function of the protein is determined by its amino acid sequence (R-groups) and its shape DO PROTEIN FOLDNG ACTIVITY • 1. Get an amino acid sheet (colors) • 2. Add carboxyl (L hand) and amino (R. hand) functional groups. R group attaches to your leg. NH2 H H C C COOH R group NH2 COOH R group • 4. Line up the amino acids in order met Lys His Gly Val Ser Leu Asp Cys Glu Cys Gln Asn Thr Ser Pro Trp Phe Val Tyr Levels of Protein Structure Primary structure • is its unique sequence of amino acids • determined by inherited genetic info (DNA) Protein Folding Youtube DO PROTEIN FOLDNG ACTIVITY • 4. Join the amino group and carboxyl groups to form a peptide bond. N COOH NH2 C=O I H R group R group Levels of Protein Structure • Secondary Structure • most protein have segments repeatedly coiled or pleated in patterns • result of H-bonds • Secondary Structure Youtube Note the H-bonds (between -O of carbonyl and -H of amino): coiling and pleating Protein Structure • Tertiary Structure • a. folding on itself • b. hydrophobic • a type of weak bond (disulfide, H-bonds, and ionic bonds) • Cross-links between R-groups Tertiary Folding: disulfide bridges • Disulfide bridges formed between cysteine amino acids • (Look at cysteine’s structure) • Four Levels of Protein Folding Tertiary Level: Determined by R groups Tertiary Structure Youtube Disulfide Bridges • Formed when cysteine’s sulfur join • You Tube Videos Disulfide Bonds Use the Amino Acid Reference Sheet • Select the type of tertiary interaction as • (1) disulfide (2) ionic • (3) H bonds (4) hydrophobic • • • • A. Leucine and valine B. Two cysteines C. Aspartic acid and lysine D. Serine and threonine ANSWERS • Select the type of tertiary interaction as • (1) disulfide (2) ionic • (3) H bonds (4) hydrophobic • • • • A. 4 B. 1 C. 2 D. 3 Leucine and valine Two cysteines Aspartic acid and lysine Serine and threonine Protein Structure • Quaternary Structure • two or more subunits joined into one functional macromolecule • Quarternary Structure youtube (42 secs) Two Basic Shapes of Quaternary Proteins • Fibrous • Strands • Like hair, nails,skin,muscle fibers (meat)insoluble in water • Globular • Blobs like hemoglobin, insulin, hormones, antibodies • Soluble in water Quaternary: combination of other shapes • Protein Folding Youtube (2:28) collagen • Cool Protein Folding (34 secs) • Identify the level of protein structure • 1. Primary 2. Secondary • 3. Tertiary 4. Quaternary • A. Beta pleated sheet • B. Order of amino acids in a protein • C. A protein with two or more peptide chains • D. The shape of a globular protein • E. Disulfide bonds between R groups • • • • • • • • • • Identify the level of protein structure 1. Primary 2. Secondary 3. Tertiary 4. Quaternary ANSWERS 2 Beta pleated sheet 1 Order of amino acids in a protein 4 A protein with two or more peptide chains 3 The shape of a globular protein 3 Disulfide bonds between R groups Denaturation • Disruption of secondary, tertiary and quaternary protein structure by: • heat/organics (Break apart H bonds and disrupt hydrophobic attractions) • acids/ bases (Break H bonds between polar R groups and ionic bonds) • heavy metal ions (React with S-S bonds to form solids) • agitation (Stretches chains until bonds break) NOTE: • Denaturation does not break the primary structure (it just unravels the tertiary structure) • Denaturation of an egg with a strong acid video Protein Extra Credit OPP • Can bring in up to 3 labels (no repeats) for 1 point each with one of each of these protein terms circled: – protein – peptide – amino • 3. Draw out your R group on your colored sheet. • Group the R groups according to: •Nonpolar •Polar •Acidic •Basic FOLDING • 5. Strongest interaction of side groups: between cysteine molecules (disulfide bond -S-S-) (students move to accommodate this bond formation) Near the n-terminus (NH2 or amino end) 6. Slightly weaker ionic interactions: Between acidic and basic side groups N Terminus C terminus • 7. Hydrophobic interactions (weaker) Students clump their methyl group ends together to “Get Away” from the hydrophilic ends 8. AFTER WE HAVE BUILT OUR PROTEIN WE WILL DENATURE IT. (Do not break the peptide bonds.)