This diagram shows the primary structure of PIG INSULIN, a protein hormone as discovered by Frederick Sanger. He was given a Nobel prize in The primary structure of a protein is the sequence of the Amino Acids in the polypeptide chain (d) explain, with the aid of diagrams, the term primary structure;

Secondary structure describes the way parts of the chain fold. Some chains fold in a repeating spiral: Alpha Helix Some chains fold in a series of zig zags: Beta Pleated Sheets The folding is held in place by hydrogen bonds (e) explain, with the aid of diagrams, the term secondary structure with reference to hydrogen bonding;

Alpha helix Beta pleated sheet (e) explain, with the aid of diagrams, the term secondary structure with reference to hydrogen bonding;

Beta Pleated Sheet The dotted lines are hydrogen bonds which bind the strands together, making this a strong flat fibrous protein. In Silk, these sheets stack together like a pile of corrugated iron. H-bonds between the sheets make silk a very strong structural protein (e) explain, with the aid of diagrams, the term secondary structure with reference to hydrogen bonding;

(f) explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and hydrophilic interactions, disulfide bonds and ionic interactions; (g) explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of haemoglobin; (h) describe, with the aid of diagrams, the structure of a collagen molecule; (i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous protein);

Tertiary Structure describes the shapes which form when the protein chain further folds up on itself. It is held in place by interactions between the amino acid R groups in the polypeptide. Amino acids which are very distant in the primary structure might be close in the tertiary one because of the folding of the chain. (f) explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and hydrophilic interactions, disulfide bonds and ionic interactions;

Disulphide bonds (bridges) Hydrogen bonds Hydrophilic or hydrophobic interactions Ionic bonds (f) explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and hydrophilic interactions, disulfide bonds and ionic interactions; Between 2 cysteine amino acids

hydrophobic amino acids hydrophilic amino acids In a water-based environment hydrophobic amino acids associate together on the inside of globular proteins and hydrophilic amino acids are found on the outside (f) explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and hydrophilic interactions, disulfide bonds and ionic interactions;

GLOBULAR PROTEINS Proteins which fold into a ball are called globular proteins. They tend to be soluble. Eg: haemoglobin, and enzymes FIBROUS PROTEINS Fibrous proteins tend to be insoluble and strong and so they have a structural role for support or protection. Eg: collagen and keratin (hair) (i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous protein);

Denaturation of proteins Some of the interactions responsible for holding a protein in its 3D tertiary structure are weak –Eg hydrogen bonds They are easily broken eg by heat or by acid This is called denaturation

Quaternary structure describes any final adjustments to the molecule before it can become active. For example, pairs of chains may bind together or other inorganic substances may be incorporated into the molecule. (Prosthetic Groups) (g) explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of haemoglobin;

1. Amino acids Basic structure Essential vs non-essential Condensation/hydrolysis –peptide bond 2. Protein structure Primary Secondary  -helix  -sheet Tertiary Disulphide bonds Ionic bonds Hydrogen bonds Hydrophobic/hydrophilic interactions Quarternary Globular vs fibrous 3. Structure related to function Haemoglobin Kind of protein Quarternary structure Collagen Kind of protein Structure of a collagen fibre Proteins

Haemoglobin (g) explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of haemoglobin; A globular protein with a shape that is nearly spherical Made of 4 interlocking polypeptide chains –2 identical pairs, alpha (  and beta ( 

The hydrophilic groups are on the outside and make the protein soluble hydrophobic R groups point inwards, and interact with one another. –These interactions are important in maintaining shape (g) explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of haemoglobin; Haemoglobin

(h) describe, with the aid of diagrams, the structure of a collagen molecule;

A fibrous protein –not folded into a complex 3-D tertiary shape A very important structural protein in animals –Found in skin, bone, cartilage, teeth, tendons, muscles, ligaments, walls of blood vessels –Makes them tough Collagen

Made of 3 identical helical-shaped polypeptides –Not alpha-helix because not so tightly wound The 3 polypeptides are wound around each other (like a rope), to give a triple helix. (h) describe, with the aid of diagrams, the structure of a collagen molecule; Collagen

(h) describe, with the aid of diagrams, the structure of a collagen molecule; The helix is tightly wound due to the presence about every 3rd amino acid of glycine (R=H, so very small) The positions of the 3 polypeptides are staggered so that there is a glycine at every position going along the triple helix The triple helix is held together by hydrogen bonds Collagen Gly AA AA Gly AA Gly AA Gly AA AA Gly AA Gly AA Gly AA AA Gly AA Gly AA

Each triple helix interacts with other collagen molecules lying parallel to it – covalent bonds are formed to cross-link the molecules, forming fibres made of many collagen polypeptides –These bonds are between lysine R groups and give collagen its great strength (h) describe, with the aid of diagrams, the structure of a collagen molecule; Collagen

(h) describe, with the aid of diagrams, the structure of a collagen molecule;

FeatureHaemoglobinCollagen Type of protein Function Number of different polypeptides (i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous protein);

Prep Compare and contrast the structures of collagen and cellulose (8 marks) (i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as an example of a fibrous protein);

Homework Compare and contrast the structures of collagen and cellulose (8 marks) Similarities 1.Polymers 2.Adjacent polymer chains held together by H bonds 3.Formed by condensation reactions 4.Very strong 5.Insoluble in water Differences 5.Cellulose: polysaccharide, collagen: protein (polypeptide) 6.Cellulose: Beta glucose 7.Cellulose =microfibril, 8.associated to form macrofibrils 9.Collagen: Amino acids 10.Collagen =triple helix 11.Collagen =glycine rich 12.Collagen: covalent bonds between polymer chains

Biological molecules Got in lessonGot at homeNeed to work on Done The structures of alpha and beta glucose The formation of glycosidic bonds The structure and function of starch: amylose and amylopectin The structure and function of glycogen The structure and function of cellulose General structure of amino acids Formation/breakage of peptide bonds Primary structure of polypeptides Secondary structure: alpha helix and beta sheet Tertiary structure Quaternary structure: haemoglobin, including links to function Quaternary structure: collagen, including links to function Structure linked to function for triglycerides, phospholipids and cholesterol Using hydrogen bonding to explain properties of water, linking to roles of water in biology Test for reducing sugar Test for non-reducing sugar Quantitative test for glucose using colorimetry Test for protein, lipid and starch Fill in what you have done to show where you think you are