ENERO FEBRERO MARZO ABRIL MAYO JUNIO JULIO

CONTENTS 1.0 Introduction 2.0 Objectives 3.0 Main Content

3.1 Carbohydrates 3.2 Proteins

3.3 Lipids

3.4 Nucleic acids 4.0 Conclusion

5.0 Summary

6.0 Tutor-Marked Assignment 7.0 References/Further Reading

1.0 INTRODUCTION

The body needs digested nutrients to provide energy needed to perform functions and amino acids for body building and repairs. The nutrients in various forms are transported as small molecules of complex organic chemicals either as broken down carbohydrates, proteins, lipids and other forms. In this unit you will be introduced to the small molecules of these nutrients in the forms that they are absorbed.

2.0 OBJECTIVES

At the end of this unit, you should be able to:

 describe carbohydrates

 explain the three main classes of carbohydrates

 discuss the major types of proteins

 describe lipids

 describe nucleic acids.

3.0 MAIN CONTENT 3.1 Carbohydrates

Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen atoms. Carbohydrate are made of monosaccharide (simple sugars molecules) linked together. Their function is to provide a key

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source of energy for cells. An example is starch, made of many linked glucose molecules. Carbohydrates are divided into three main classes:

(i) monosaccharides (ii) disaccharides (iii) polysaccharides.

Monosaccharides

Monosaccharides are simple sugar unit with a general formula (CH2O)n.

The ‘n’ ranges between 3 and 9. Monosaccharides are all sweet, small crystalline molecules. They are readily soluble in water and are all reducing sugars. They are classified on the basis of the number of carbon atoms: trioses (3 carbons), tetroses (4 carbon), pentoses (5 carbons). The most common are pentoses and hexoses. Most monosaccharides are metabolic energy sources and serves as building blocks for the synthesis of other macromolecules.

Disaccharides

They are formed when two monosaccharides combine by condensation.

The bonds formed between the two monosaccharides units as a result of condensation is called a glycosidic bond. There are several examples of disaccharide, but the most common are maltose, lactose and sucrose.

Polysaccharides

These are made by joining several monosaccharide units. They function mainly as food and energy stores e.g. starch and glycogen or as structural material e.g. cellulose. They are not sweet, non-crystalline, either slightly or insoluble in water.

3.2 Proteins

Proteins are macromolecules with molecular weight of several thousands. They are compounds containing carbon, hydrogen, oxygen, nitrogen, sulphur. There are two distinct types of protein: (1) Fibrous proteins (2) Globular proteins.

Fibrous Proteins

Fibrous proteins are insoluble in water and are physically tough. This property enables them to play a structural role in a cell. Major examples of fibrous proteins

(a) Collagen: This is found in bones, skin, tendon and cartilage. This is the most abundant protein in invertebrates and it usually contains three very long polypeptide chains, each with about 1,000 amino acids.

(b) Keratin: This is found in the outermost layer of the skin and hair, scales, hooves, nails and the feathers of animals. The main function is to protect the body against the environment.

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(c) Fibrinogen: This is blood plasma protein, responsible for blood clotting. With the action of thrombin, fibrinogen is converted into molecules of insoluble protein called fibrin, which forms a network on the surface of wounds to trap blood cells and form clots.

Globular Proteins

These are proteins that are soluble in water. They have tertiary and sometimes quaternary structures. They are folded into spherical or globular shapes. They include immunoglobulin or antibodies in the blood, enzymes and some hormones, which are important in maintaining the structure of the cytoplasm.

3.3 Lipids

Lipids are non-polar molecules that are not soluble in water. They include fats, phospholipids, steroids, and waxes. Lipids functions are to provide energy and serve an important part in the structure and functioning of cell membranes. Some examples of lipids include butter (saturated fat), cholesterol (steroid) and ear wax (wax).

3.4 Nucleic Acids

Nucleic acids are long chains of smaller molecules called nucleotides.

Nucleic acids mainly serve the purpose of providing the organism with its genetic blueprint and coding. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are two types of nucleic acids.

SAE

a. Differentiate between the three main classes of carbohydrates b. How is fibrous protein different from globular protein

4.0 CONCLUSION

In this unit, we have learnt that carbohydrates made of carbon, hydrogen and oxygen atoms metabolic energy sources and serve as building blocks for the synthesis of other macromolecules. Protein on the other hand are made up of carbon, hydrogen, oxygen, nitrogen, sulphur while lipids are not water soluble materials that include fats, phospholipids, steroids, and waxes. Nucleic acid provides basis for the genetic blueprint and coding of the DNA and RNA.

5.0 SUMMARY

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In this unit, you have learnt that:

a. Carbohydrates are made up of three classes of monosacharides, disaccharides and polysacxharides depending

b. Proteins are mainly two types, fibrous and globular proteins c. Lipids are non-polar molecules, insoluble in water and include

fats, phospholipids, steroids and waxes and examples include saturated fats and cholesterol.

d. Nucleic acids

6.0 TUTOR -MARKED ASSIGNMENT

Please answer the following questions:

7.0 REFERENCES/ FURTHER READING

Fox, S.I. (2012). Human Physiology. (12th ed.). New York: Mc Graw Hill.

Ganong, W.F. (2019). Review of Medical Physiology. (26th ed.). New York: Mc Graw Hill.

Guyton, A.C. & Hall, J.E. (2021). Textbook of Medical Physiology.

(14th ed.). Philadelphia: Harcourt International Edition, W.B.

Saunders.

Sembulingam K & Sembulingam P.(2012). Essential Medical Physiology. (6th ed.). new Delhi: Jaypee Brothers medical Publishers (P) Ltd

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UNIT 4 HOMEOSTASIS