2.4: Proteins

prior learning & retrieval practice

Essential idea: Proteins have a very wide range of functions in living organisms.

A1: Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk as examples of the range of protein functions.

U7: Living organisms synthesize many different proteins with a wide range of functions.

Guidance:

• The detailed structure of the six proteins selected to illustrate the functions of proteins is not needed.

Exercise 1: Make a presentation on the different types of functions that proteins can have in living things. Use the following proteins as examples: Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk.

You can use the protein data bank below to find out about each of these proteins.

S1: Drawing molecular diagrams to show the formation of a peptide bond.

U1: Amino acids are linked together by condensation to form polypeptides.

Exercise 2: Draw and label a diagram to show two amino acids joining to form a dipeptide. Make sure the peptide bond is clearly labelled.

U2: There are 20 different amino acids in polypeptides synthesized on ribosomes.

U3: Amino acids can be linked together in any sequence giving a huge range of possible polypeptides.

Exercise 3: If a hypothetical protein is 100 amino acids long. How many different ways can amino acids be arranged?

U4: The amino acid sequence of polypeptides is coded for by genes.

U5: A protein may consist of a single polypeptide or more than one polypeptide linked together.

U6: The amino acid sequence determines the three-dimensional conformation of a protein.

Exercise 4: Outline the primary, secondary, tertiary and quaternary structures of proteins

A2: Denaturation of proteins by heat or by deviation of pH from the optimum.

Guidance:

• Egg white or albumin solutions can be used in denaturation experiments.

Exercise 5: Fry an egg, observe the changes in the albumin as it heats up. Place an egg into vinegar and leave for a few weeks. What changes do you observe? Can you explain them using the term denaturation.

U8: Every individual has a unique proteome.

Exercise 6: watch the videos below. What is the proteome?

NoS: Looking for patterns, trends and discrepancies—most but not all organisms assemble proteins from the same amino acids. 

Guidance:

• Students should know that most organisms use the same 20 amino acids in the same genetic code although there are some exceptions. Specific examples could be used for illustration.

Exercise 7: Why do most organisms use the same amino acids to build proteins? Are there any exceptions to this.