Leaving Certificate Agricultural Science

1. Leaving Certificate Agricultural Science Food & Nutrition

2. The Functions of Food • Food supplies the animal with energy for all animal activities. • To provide the materials for growth and repair of cells • To provide materials for production of hormones and enzymes. • To provide raw materials for milk, egg and wool production etc.

3. Food Elements • The six most common elements found in food are Carbon (C), Hydrogen (H), Nitrogen (N) Oxygen (O), Phosphorous (P) and Sulphur (S). • The elements found in dissolved salts include Sodium (Na), Magnesium (Mg), Chlorine (Cl), Potassium (K) and Calcium (Ca). • Trace elements are required in our body in very small amounts and include Iron (Fe), Copper (Cu) and Zinc (Zn). • These elements, when combined in different ratios form larger units called biomolecules.

4. The Major Food Groups (Bio-molecules) • There are five main food groups: • Carbohydrates • Lipids (Fats and Oils) • Protein • Vitamins • Minerals • Water is often considered the sixth food group, due to the huge importance it plays in our bodies.

5. Autotrophic and Heterotrophic • Green plants can make their own food in a process known as PHOTOSYNTHESIS. • Therefore plants are known as autotrophs or autotrophic. • Animals have to ingest their food and cannot make all their food needs. • Animals are known as heterotrophs or heterotrophic.

6. The Food Pyramid • The food pyramid is a diagram illustrating which proportions of food types are required in our everyday diet. • Complex Carbohydrates (Starch and Fibre) are the most important. • While fats and sugars are to be taken in the least amount. • The diagram is shown on the next slide.

8. Carbohydrates • The main sources of carbohydrates in our diet are starches and sugars. • Carbohydrates are made up of Carbon, Hydrogen and Oxygen molecules with the common formula Cx (H2O)x • Carbohydrates are classified by their number of sugar units, called saccharides. • Monosaccharides (1 sugar unit), Disaccharides (2) or Polysaccharides (many).

9. Monosaccharides • Are glucose, fructose and galactose. • All have the formula C6H12O6 but arranged differently. • Sources of monosaccharides are energy drinks, but indirectly through all other sugars.

10. Disaccharides • Contain two sugar units: • Maltose = Glucose + Glucose • Lactose = Glucose + Galactose • Sucrose = Glucose + Fructose

11. Polysaccharides • Starches, Cellulose, Chitin and glycogen etc. • Humans cannot digest cellulose. • However cattle and horses (and other ruminants) can, by a symbiotic relationship with bacteria in their stomachs. • While monosaccharides and di-saccharides provide energy for our bodies, polysaccharides are mainly structural.

12. Testing Food for a Reducing Sugar Benedicts or Fehlings solution is added to the food sample (dissolved if necessary) and placed in a water bath. A brick red colour is a positive result.

13. Testing food for Starch Iodine solution is used to test for starch A blue / black colour is a positive result.

14. Proteins • The main sources are lean meat, egg white, fish, milk, pulse and nuts. • Contain the elements Carbon, Hydrogen, Oxygen and Nitrogen (sometimes Sulphur) • Proteins are made up of units called amino acids. • There are over 80 known amino acids, but only 26 occur in proteins.

15. Proteins (2) • These amino acids form long chains which come together as a protein molecule. • A typical Protein molecule has 500+ amino acids • Some amino acids can be made by our body and these are called non – essential amino acids. • Other amino acids can only be brought into our bodies by ingestion. • These are known as essential amino acids.

16. Proteins (3) • There are no essential amino acids for ruminants. • Proteins are used in the body for growth and repair of cells. • The Biuret Reagent is used to test for the presence of protein in a food sample. • A lilac colour indicates a positive result.

17. Lipids • Sources of fats are obvious – butter, oils, nuts, milk and general fatty foods. • Contain the elements Carbon, Hydrogen and Oxygen but not in any given ratio unlike Carbohydrates. • A unit of fat (called a triglyceride) is made up of one molecule of Glycerol with three fatty acids chemically attached.

18. Role of Fats • Fats provide energy to the body (twice as much as carbohydrates), insulation and contain vitamins (known as Fat Soluble). • Phospholipids are oil like substances but contain a phosphate group instead of one fatty acid. • Phospholipids are important as they form cell membranes.

19. Saturated vs. Unsaturated • Fats can be known as saturated or unsaturated. • Saturated means that as many Hydrogen atoms as possible are attached to the Carbon atoms. • Saturated fats are usually solid at room temperature and are related to heart disease. • Unsaturated fats contain fewer Hydrogen atoms, and contain what are known as double or triple bonds. • They are usually oil at room temperature.

21. Vitamins • Vitamins have many functions in the body. • Vitamins mainly act as co-enzymes, which means they trigger enzymes to work. • Vitamins can be water soluble or fat soluble. • Vitamin C (A water soluble vitamin) • Found in Citrus Fruits • Involved in the absorption of Iron & Respiration • Lack of Vit. C causes Scurvy!! • Vitamin A (A fat soluble vitamin) • Found in the carotene pigment (found in carrots). • Involved in formation of the visual pigments. • Lack of Vit. A causes night blindness.

23. Minerals • Minerals have no energy value but are used in the body for many different reasons • Osmo-regulation (control of water levels) • Acid – Base balance (pH balance) • Formation of enzymes, pigments and hormones. • Triggers or activators in different reactions. • Iron for Haemoglobin in Blood (Anaemia)

24. Role of Water • Water has no energy value but again is essential for all bodily functions • Our bodies are made up of 75% water. • Waters main function is as a medium where other food items are stored and moved. • Of course our blood is made of nearly all water so it is vital that the human body gets 3 – 4 pints of water a day.

25. Structural Role of Biomolecules • Carbohydrates: • Cellulose as a component of Cell Walls • Protein: • Fibrous proteins like Keratin are found in hair and nails. • Myosin is found in muscles. • Lipids: • Phospholipids are a major component of cell membranes.

26. Enzymes • Enzymes are biological catalysts. • They are natural substances, which speed up the breakdown of food substances and other materials. • They work by combining with the substrate forming the enzymes – substrate complex. • The enzymes – substrate complex breaks down and forms the product and releases the enzyme. • The enzyme can then be used again. • Enzymes are very specific and will only work on one substrate. • Enzymes are very important in the breakdown of food in our digestive system. • Enzymes work at specific pH’s. Most at pH 7 but pepsin works only at pH 2 & 3.