2.1 Biological macromolecules  (Page 3/4)

The functions of proteins

Proteins have a number of functions in living organisms.

• Structural proteins such as collagen in animal connective tissue and keratin in hair, horns and feather quills, all provide support.
• Storage proteins such as albumin in egg white provide a source of energy. Plants store proteins in their seeds to provide energy for the new growing plant.
• Transport proteins transport other substances in the body. Haemoglobin in the blood for example, is a protein that contains iron. Haemoglobin has an affinity (attraction) for oxygen and so this is how oxygen is transported around the body in the blood.
• Hormonal proteins coordinate the body's activities. Insulin for example, is a hormonal protein that controls the sugar levels in the blood.
• Enzymes are chemical catalysts and speed up chemical reactions. Digestive enzymes such as amylase in your saliva, help to break down polymers in food. Enzymes play an important role in all cellular reactions such as respiration, photosynthesis and many others.

Research project : macromolecules in our daily diet

1. In order to keep our bodies healthy, it is important that we eat a balanced diet with the right amounts of carbohydrates, proteins and fats. Fats are an important source of energy, they provide insulation for the body, and they also provide a protective layer around many vital organs. Our bodies also need certain essential vitamins and minerals. Most food packaging has a label that provides this information. Choose a number of different food items that you eat. Look at the food label for each, and then complete the following table:

   Food	Carbohydrates (%)	Proteins (%)	Fats (%)

   1. Which food type contains the largest proportion of protein?
   2. Which food type contains the largest proportion of carbohydrates?
   3. Which of the food types you have listed would you consider to be the 'healthiest'? Give a reason for your answer.
2. In an effort to lose weight, many people choose to diet . There are many diets on offer, each of which is based on particular theories about how to lose weight most effectively. Look at the list of diets below:
   • Vegetarian diet
   • Low fat diet
   • Atkin's diet
   • Weight Watchers
   For each of these diets, answer the following questions:
   1. What theory of weight loss does each type of diet propose?
   2. What are the benefits of the diet?
   3. What are the potential problems with the diet?

Carbohydrates and proteins

1. Give the structural formula for each of the following:
   1. A polymer chain, consisting of three glucose molecules.
   2. A polypeptide chain, consisting of two molecules of alanine and one molecule of serine.
2. Write balanced equations to show the polymerisation reactions that produce the polymers described above.
3. The following polypeptide is the end product of a polymerisation reaction:

   

   1. Give the structural formula of the monomers that make up the polypeptide.
   2. On the structural formula of the first monomer, label the amino group and the carboxyl group.
   3. What is the chemical formula for the carbon side chain in the second monomer?
   4. Name the bond that forms between the monomers of the polypeptide.