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Carbohydrates, Proteins, Fats: An Overview

This introduction to nutrients covers the importance of a balanced diet, including carbohydrates, proteins, and fats. Learn about the structure, functions, classification, and sources of these essential macronutrients for a healthy lifestyle.

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Carbohydrates, Proteins, Fats: An Overview

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  1. Nutrition Introduction to the nutrients

  2. Blanced diet • maintains the homeostasis in the body by supporting the metabolism in the cells • provides the energy needed • contains fibre to aid the function of the gut • the components are: • carbohydrates, proteins, fats, vitamins, minerals, trace elements, dietary fibre (non-starch polysaccharide) and water

  3. Balanced diet

  4. Carbohydrates • dietary carbohydrates originate mainly from plants • mainly sugars and starches • composed of carbon, oxygen and hydrogen • are classified according to the complexity of the molecules from which they are formed • glucose is the main form in which sugar is used by cells

  5. Carbohydrates

  6. Monosaccharide • carbohydrates have to be broken into monosaccharides before they can be absorbed from the alimentary canal • highly soluble in water • the simplest form of carbohydrate • glucose • fructose • lactose

  7. Disaccharide • consists of two monosaccharides joined together • sucrose (table sugar) = glucose + fructose • lactose (milk sugar) = glucose + galactose • maltose (malt sugar) = glucose + glucose • highly soluble in water

  8. Polysaccharide • consists of numerous monosaccharides joined together • may be very large molecules • poorly soluble in water • glycogen is made of numerous glucose units, a means of storing glucose • starch is equivalent storage polysaccharide (to glycogen) in plants

  9. Dietary fibre • non-starch polysaccharide (NSP) • indigestable part of the diet • includes cellulose from plants • important part of a healthy diet

  10. The structure of carbohydrates

  11. Main functions of carbohydrates • provide energy and heat • using carbohydrates saves proteins from being used as a source of energy • act as energy reserves • glycogen (liver and skeletal muscles) • converted into fat and stored in fat depots

  12. Dietary fibre • provides bulk to the diet • slows the digestion rate • stimulates peristalsis • attracts water to faeces • prevents constipation • prevents some gastrointestinal disorders

  13. Dietary fiber

  14. Proteins • made of amino acids joined together in different combinations • composed of carbon, hydrogen, oxygen and nitrogen, some minerals can also be included • 20 amino acids are used as the principal building blocks of protein • may be in the form of animal or vegetable protein

  15. Proteins

  16. Amino acids Essential amino acids (9 in number) • cannot be synthesised in the body but have to be included in the diet Non-essential amino acids (13 in number) • can be synthesised in the body (liver) Most animal proteins have the full range of amino acids (= complete proteins). Vegetable proteins may lack adequate amounts of the essential amino acids.

  17. The structure

  18. Excess protein • If the intake of protein exceeds the need • the nitrogen part will be converted to urea and excreted by the kidneys • the rest will be converted to fat and stored in the fat depots

  19. Functions of proteins • growth and repair of body cells and tissues • carrier molecules (e.g. haemoglobin) • synthesis of enzymes, plasma proteins, antibodies, some hormones • providing energy if needed

  20. Fats • belong to lipids together with phospholipids, fat-soluble vitamins, cholesterol and prostaglandins • composed of carbon, hydrogen and oxygen, but in a different molecular structure from carbohydrates • insoluble in water

  21. Fats

  22. Triglycerides consist of one glycerol and three fatty acid molecules make up the majority of all dietary fats

  23. The classification of fats Saturated fats • solid at room temperature • originate from animal sources Unsaturated fats • fluid at room temperature • usually originate from vegetables or plants Essential fatty acids • 3 of the polyunsaturated fats are considered essential for life (linoleic, linolenic, arachadonic acid)

  24. Cholesterol • a phospholipid • a constiuent of the cell membrain and needed in the production of steroid hormones • can be synthesised by the body (liver) • full-fat dairy products, egg yolk and fatty meat contain cholesterol

  25. Too much cholesterol

  26. The functions of fats • concentrated source of energy and heat • storage of energy • support some organs • storage of fat-soluble vitamins (A, D, E, K) • insulation, reduces heat loss through the skin • constituent of myelin sheat of the nerve cell • formation of steroid hormones of cholesterol

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