Proteins

STARTER. You are about to see an animation on protein structureTry and match the following key terms with the definitions given

-primary structure

-secondary structure

-tertiary structure

-quaternary structure

-alpha helix

-beta pleated sheet

Learning ObjectivesEveryone shouldState four functions of proteins, giving a named example of each

Most willOutline the difference between fibrous and globular proteins, with reference to two examples of each protein type.

Some mightExplain the significance of polar and non-polar amino acids. Explain the four levels of protein structure, indicating the significance of each level.

Starter Team ActivityYou have 5 min to complete Steps A and B of Protein modelling handout on your bench in teams

Alina and LuciaAndrea , JP and Natalia

Work in a team BUT complete your own handout INDIVIDUALLY

Learning ObjectivesEveryone shouldState the four levels of protein structure

Most willDescribe the four levels of protein structure, indicating the features of each level.

Some mightExplain how polar and non-polar amino acids determine the folding of a polypeptide to produce a functional protein

Primary structure of a proteinTo simulate a protein, you will make a model of your protein using plasticine beads

Refer to the sequence of 15 amino acids (the colored circles on Step C of your worksheet) Complete Step C first if you havent already using the amino acid chart provided

Arrange beads of the appropriate colors on the pipe cleaner. (substitute yellow for green)

The beads should be approximately evenly spaced the along the pipe cleaner.

Secondary structure of a proteinTwist one half of your protein model around a pencil to make a spiral.

Bend the other half of your protein molecule into a zig-zag shape by making a bend in the opposite direction at each bead.

Make a drawing to show the secondary structure of your protein model (Step D of your worksheet).

Label the alpha helix region and the beta-pleated sheet region on your drawing.Tertiary StructureTwist your protein into a 3-D shape according to the protein folding rules on the chart

Make a drawing to show the tertiary structure of your protein model (Step D of your worksheet).

Note: Do the best you can to make your 2-dimensional drawing look like your 3D model.

Quarternary StructureSome protein chains are attracted to other protein chains.

Work with the other team and try putting your protein model next to their protein model in a way that still follows the rules of protein folding.

Make a drawing to show the quaternary structure of your protein model (Step D of your worksheet).

Plenary Ticket to Exit!Fill out your table without using your notes

Try and incorporate as many key terms from the topic as you can

PLENARYExplain the four levels of protein structure (10)primary structure is sequence / number of amino acids;determined by base sequence in the gene;(largely) determines higher level structures/secondary structure/tertiary structure;

secondary structure is regular repeating patterns;such as alpha/ helix and beta/ (pleated) sheet;determined by H bonds (within chain);

tertiary structure refers to overall 3-D shape;conformation can determine function;tertiary structure determined by R-group interactions / ionic interactions /hydrophobic interactions / disulfide bridges / H-bonds;

quaternary structure is only found in proteins formed from more than one polypeptide;e.g. hemoglobin; (accept other suitable example)Starter sort the statements into your table (q7)

Learning ObjectivesEveryone shouldState four functions of proteins, giving a named example of each

Most willOutline the difference between fibrous and globular proteins, with reference to two examples of each protein type.

Some mightExplain the significance of polar and non-polar amino acids in biological molecules

GROUP ACTIVITY: Using your whiteboards can you draw a diagram to explain how they do this?Now lets try some PPQs (Q9-11)

For question 11.c please change the word CHANNEL to the word MEMBRNEMark scheme9. Describe a polar molecule. Has charge10. In the space below, draw and annotate a simple diagram to explain how polar molecules aid enzyme function.

11. a) The hydrophobic tails of the plasma membrane reject polar molecules: they do not allow them to pass through the membrane into or out of the cell. Define hydrophobic. Lacks an affinity for waterb) Identify labels I to IV as being polar or non-polar.

polarNon polarpolarNon-polarc) Using the diagram, explain the significance of polar molecules in MEMBRANE proteins. (8)membrane is a lipid bi-layer;membrane has hydrophobic interior / lipid hydrophobic tails oriented inward;hydrophilic on cytoplasmic and extracellular side / lipid hydrophilic heads orientedoutward;

polar amino acids are hydrophilic/water soluble/attracted to outside of membrane;non-polar amino acids are hydrophobic/attracted to inside of membrane;integral proteins embedded in the membrane;peripheral proteins associated with surface of membrane;

non-polar amino acids cause proteins to be embedded in membrane;polar amino acids cause parts of proteins to protrude from membrane;transmembrane proteins have both polar and non-polar amino acids;polar amino acids create channels through which (hydrophilic) substances/ionscan diffuse;