PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a...

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Transcript of PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a...

Page 1: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.
Page 2: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

PROTEINS

• C, H, O, N, (S)

• Polymers made from chains of amino acids

• 20 amino acids used

• Linked by a peptide bond

Page 3: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

In addition fibrous proteins (collagen) form structural components in cells and tissues

Page 4: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.
Page 5: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Amino Acids

• Central carbon has attached:– Amine group– Acid group– Functional group (R) – determines nature of amino acid

• R groups fall into 4 categories• Non-polar - only carbons; chains or aromatic rings

(methionine has sulphur)• Uncharged Polar- carbons with amine groups (NH2) or

- hydroxyl groups (OH)• Acidic - carboxylic acid groups (COOH) ionizes to negative

charge COO-

• Basic - terminal amine groups (not next to C=O) ionizes to NH3

+

Page 6: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.
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Peptide bond

• Amino acids joined by a peptide bond

• Condensation reaction between – COOH of 1st amino acid and NH2 of 2nd amino

acid•Chains are called peptides (short)/ polypeptides (longer)•Peptide bond is rigid•Bonds either side can rotate

–Introduces flexibility allowing proteins to take up variety of shapes.

Page 8: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Protein Structure

• 4 levels– Primary– Secondary– Tertiary– Quaternary

Page 9: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

PRIMARY STRUCTURE

• Order in which amino acids are linked together– Written starting at the N (amino) terminus– e.g.

– Arg-Lys-Phe-Glu-Ser-Gly-

– R K F E S G

N C

N terminus

C terminus

Page 10: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

SECONDARY STRUCTURE

• Two possible shapes in the protein chain each stabilised by Hydrogen bonds: -pleated sheet -helix

Page 11: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

-pleated sheet

• Peptide chains arranged side by side• Held together by H-bonds between the two chains• Parallel (chains running same direction)

• N C

• N C

• Antiparallel (chains in opposite directions)• N C

• C N

Page 12: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

-pleated sheet

• Silk– Resistant to stretch (very strong)

Page 13: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

-helix

• Peptide chain coils into a helix– Held by H-bond between N-H group and the

C=O 4 residue away

• 4 residues per turn

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-helix• Hair/Wool (keratin)

– Stretchy (er) -helices coiled together to form a superhelix

– For horn/hoof more disulphide bridges are present (covalent)

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Tertiary Structure

• The overall folded shape of a protein held together by (usually) weak forces.– Hydrogen bonding which doesn’t form secondary

structure– Hydrophobic interactions

• Place non-polar amino acids inside protein• Polar amino acids on surface

– Van der Waals forces– Ionic interactions (strong) – Disulphide bridges (strong)

• Covalent bond between cysteine residuesMyoglobin

Page 16: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.
Page 17: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

• With reference to bonding, explain why enzyme activity decreases as you increase the temperature above the optimum, and as you move pH away from the optimum.

Page 18: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Proteins fold to take up their shape

Shape is determined by primary structure –

order of hydrophobic/ hydrophilic amino acids & relative positions of polar/charged amino acids.

Loss of tertiary structure is called denaturation.

Page 19: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Lysozyme

Proteins are 3D

Page 20: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Primary structure determines tertiary structure

Mutation acid (polar) for non polar changes folding pattern

Page 21: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Prosthetic groups• Some proteins have permanently bound non

protein groups, called prosthetic groups– e.g. myoglobin & haemoglobin bind to a porphyrin

(haem) chelating an Iron atom– e.g. Chlorophyll has a similar prosthetic group

chelating Mg

• The protein without its prosthetic group is called an apoprotein, with its group it is called a holoprotein

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Co-factors/ Co-enzymes

• Other proteins have inorganic ions temporarily bound to them– E.g. copper/ zinc on enzymes

• Others have carbon containing molecules temporarily attached– e.g. Coenzyme A, NAD, FAD

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Quaternary Structure

• Only present if protein has more than one polypeptide chain

• Describes the shape adopted by the interacting polypeptide chains

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Nucleic Acids

• DNA– Deoxyribonucleic Acid

• RNA– Ribonucleic Acid

• Video

Page 28: PROTEINS C, H, O, N, (S) Polymers made from chains of amino acids 20 amino acids used Linked by a peptide bond.

Nucleic Acids

• Summary Knowledge– DNA deoxyribose sugar,– RNA ribose sugar– DNA double stranded (antiparallel)– RNA single stranded– DNA thymine,– RNA uracil– A double (hydrogen) bonds to T (A 2 T)– G triple (hydrogen) bonds to C (G 3 C)– G & A purines (small word, big molecule –A Giant)– C,T & U pyrimidines (big word, small molecule)

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