Macromolecules - Proteins PDF

Proteins Proteins Most diverse and most important molecule in living organisms Functions: 1. Structural (keratin in hair, collagen in ligaments) 2. Storage (casein in mother’s milk) 3. Transport (Haemoglobin!) 4. Hormonal (insulin)… (more functions on the...

Proteins Proteins Most diverse and most important molecule in living organisms Functions: 1. Structural (keratin in hair, collagen in ligaments) 2. Storage (casein in mother’s milk) 3. Transport (Haemoglobin!) 4. Hormonal (insulin)… (more functions on the next slide….)  Proteins Functions (cont’d) 5. Receptors (taste buds) 6. Contractile (actin in muscles) 7. Defensive (fibrin for clotting) 8. Enzymatic (lactase) (sophisticated) structure determines function Has its own unique 3D shape (conformation) Simplest protein = polymer of amino acids (polypeptides) Amino Acids Amphiprotic (posses both acidic: carboxyl, and basic: amino groups). May be polar, nonpolar or charged depending on the R group Sequence determines the final shape (conformation) of protein. Amino Acids There are 20 different R groups, thus 20 different a.a. (amino acids) Of the 20 amino acids that make up proteins, we must consume 9, as we can not make these essential amino acids on our own: trp, met, val, thre, phe, leu, ile, lys, his *** Newly discovered aa include Pyrrolysine & selenocysteine, but act differently then the initial 20 Polypeptide chain Ranges from a few – 1000+ amino acids Amino acids are joined together by peptide bonds (amide bonds) Condensation reaction between amino group and carboxyl group of adjacent amino acids Four Levels of Protein Folding Primary Structure (1o) The sequence of amino acids in a polypeptide chain, which is determined by the nucleotide sequence of a particular gene. Four Levels of Protein Folding Secondary Structure (2o) The folding and coiling of the polypeptide chain as it grows into an β-pleated sheet or α-helix H bond between C=O group and N-H group every 4th amino acid to form alpha helix. When 2 parts of the chain lie parallel forms a beta pleated sheet Four Levels of Protein Folding Tertiary Structure (3o) The polypeptide chain undergoes additional folding due to side chain (R group) interactions. Hydrophobic interaction – hydrophobic regions direct themselves into core of protein Hydrogen bonds – between polar R groups Ionic bonds - between (+) and (-) charged R groups Disulphide bridges- strong covalent bonds between 2 sulfhydryl groups (from cysteine monomers) Four Levels of Protein Folding Quaternary Structure (4o) Two or more polypeptide chains come together, such as in collagen and haemoglobin. Summary: 4 Levels of Protein Folding Functional proteins must be in either the tertiary or quaternary structure to be effective Some more terms Chaperone Proteins - aid a growing polypeptide to fold into tertiary structure Globular Protein – one or more polypeptide chains that take on a rounded shape. Protein Denaturing Temperature and pH changes can cause a protein to unravel (denature). A denatured protein is unable to carry out its biological function. Can be either harmful or beneficial Harmful: Fever Protein denaturation Useful denaturation include: 1. Meats cured by denaturing spoilage bacteria 2. Blanching fruits denatures browning enzymes 3. Temporarily curl/straighten hair (w/ heat) 4. Meats easier to chew when heat is used to denature fibrous proteins (marinate) 5. Fever? Practice! Text: pgs 25-27 (read & cbd) #19-24 pg 28 Worksheet AS -7:45 Protein Structure & Folding https://www.youtube.com/watch?v=hok2hyED9go Nucleic Acids Nucleic acids are found in: DNA (stores hereditary info.) RNA (ribonucleic acid) ATP (molecule of stored energy) nucleotide coenzymes (NAD+, NADP+ and FAD) 🡪 used in energy transformations. DNA and RNA are nucleotide polymers. Remember: Nucleotides consist of a nitrogenous base, a five-carbon sugar and a phosphate group. The nitrogenous bases are: adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). Nucleic Acids Cytosine, thymine and uracil are single-ringed pyrimidines, while adenine and guanine are larger double-ringed purines. In DNA, A bonds with T with 2 hydrogen bonds, and G bonds with C with 3 hydrogen bonds. The two strands are antiparallel (one strand is upside down compared to the other). Purines always bond with a pyramidine. CC (14:08) - Biological Molecules https://www.youtube.com/watch?v=H8WJ2KENlK0&t=495s Finish S. 1.2 & do # 1-2, 4-6, 8-10