Chapter 3 Nutrition Leaving Certificate Biology Higher Level

Chapter 3: Nutrition Leaving Certificate Biology Higher Level

Function of Food • Food is a complex of chemicals required by a living organism to maintain metabolism and continuity of life

Common Elements in Food – Carbon C – Hydrogen H – Oxygen O – Nitrogen N – Phosphorus P – Sulphur S

Elements in Food as Dissolved Salts • 5 elements present in dissolved salts: – Sodium Na – Magnesium Mg – Calcium Ca – Potassium K – Chlorine Cl

Trace minerals • 3 trace elements (minerals) present in living organisms: minerals – Iron Fe – Copper Cu – Zinc Zn

Biomolecules • Biomolecules are chemicals found in and produced by living organisms • There are 4 major types of biomolecules: – Carbohydrates – Lipids – Proteins – Vitamins

Carbohydrates • C, H, O: Ratio: Cx(H 2 O)y • Three categories: – Monosaccharides – Disaccharides – Polysaccharides (CH 2 O)n

Monosaccharides § Glucose [C 6 H 12 O 6] - a reducing sugar and formed by breakdown of glycogen § Fructose [C 6 H 12 O 6] - a reducing sugar and found in many fruits § Galactose [C 6 H 12 O 6] - a reducing sugar and formed by breakdown of lactose (found in milk)

Disaccharides • Maltose (a reducing sugar) – Found in germinating seeds (e. g. barley) – Glucose + Glucose → Maltose [C 12 H 22 O 11] + H 2 O • Sucrose (NOT a reducing sugar) – Commonly known as table sugar – Glucose + Fructose → Sucrose [C 12 H 22 O 11] + H 2 O • Lactose (a reducing sugar) – Found in milk - some people have lactose-intolerance – Glucose + Galactose → Lactose [C 12 H 22 O 11] + H 2 O

Polysaccharides • Starch (also known as amylose) – Plants store glucose as starch, e. g. potatoes, bananas – Long chains and some branching of glucose molecules making it easy to digest • Cellulose (also known as fibre/roughage) – Found in cell walls and stems of plants such as celery – Composed of many glucose molecules bonded together in long chains making it difficult to digest • Glycogen – Animals store glucose as glycogen in liver and muscles – Glycogen is more branched than starch

Structural and Metabolic roles of Carbohydrates • Structural role: – Cellulose: component of cell walls; keeps plant upright • Metabolic role: – Energy: Mono-, Di-, and Polysaccharides are metabolised to release energy

Lipids • Lipids: consist of the elements C, H, and O, but have fewer O atoms than carbohydrates – Two main categories: • Triglycerides • Phospholipids – Food sources of lipids: • Butter, oils, margarines, cream, olives, animal fat

Triglycerides • Triglycerides: one molecule of glycerol linked to three fatty acid molecules – Fats: solid at room temperature (RT) – Oils: liquids at RT - contain different types of fatty acids than fats Fatty acid 1 Fig. 1: A Triglyceride Glycerol Fatty acid 2 Fatty acid 3

Phospholipids • Phospholipids: one fatty acid replaced by a phosphate Fig. 2: A Phospholipid P Fatty acid 1 Glycerol Fatty acid 2

Structural and Metabolic roles of Lipids • Structural role: – Phospholipids: component of cell membranes of all living cells – Triglycerides: form adipose tissue that surrounds important internal organs and acts as a shock absorber • Metabolic role: – Energy: triglycerides are stored by organisms as a source of energy

Proteins • Proteins consist of elements: C, H, O, N - no particular ratios • Sulfur and phosphorus are also present in some proteins • There are 20 common amino acids found in proteins – Two main categories of protein: • Fibrous proteins - little or no folding (e. g. proteins found in hair, skin & nails) • Globular proteins - lots of folding (e. g. protein hormones, enzymes and antibodies)

Structural and Metabolic roles of Proteins • Structural role: – Skin, nails and hair contain keratin – Muscle composed of actin and myosin – Bone, ligaments and tendons contain collagen • Metabolic role: – Enzymes, antibodies and some hormones are proteins

Vitamins • Complex organic substances needed only in tiny amounts • Share no common chemical characteristics - all chemically unique • Identified by letters based on their chemical structure • A, D, E, and K are fat-soluble vitamins • B-group and C are water-soluble vitamins

1. 3. 6 Structural Role of Biomolecules Vitamins 1. Structural role: – Vitamins do not have any structural role in living organisms

1. 3. 7 Metabolic Role of Biomolecules Vitamins 2. Metabolic role: – Homeostasis and normal metabolism – Note: for the Leaving Certificate you need to know one fat-soluble and one water-soluble vitamin, their functions, and the diseases caused by their deficiency

1. 3. 7 Metabolic Role of Biomolecules • Vitamin A: A – Properties: • Fat-soluble; 2 types: retinol (from animal sources) and carotene (from plant sources); stored in liver – Functions: • Necessary for healthy epithelia tissue: skin, retina (vision); bone growth; energy regulation; antioxidant – Sources: • Animal products: liver, eggs, milk • Fruit and vegetables: carrots, tomatoes, sweet potatoes, apricots – Symptoms of vitamin A deficiency: • Night-blindness • Brain and spinal cord injury in infants

1. 3. 7 Metabolic Role of Biomolecules • Vitamin D: – Properties: • Fat-soluble; 2 types: – D 2 (ergocalciferol - produced by UV action on skin) – D 3 (cholecalciferol - from animal sources) – Functions: • Necessary for proper uptake of calcium, teeth and bone growth and bone mineralisation – Sources: • Main source is sunlight action on skin; cod liver oil – Symptoms of vitamin D deficiency: • Rickets in children • Osteomalacia in adults (more frequent in women)

1. 3. 7 Metabolic Role of Biomolecules • Vitamin E (tocopherol): – Properties: • Fat-soluble; stored in adipose tissue; – Functions: • Antioxidant - protects important biomolecules such as protein and DNA from oxidation (damage) – Sources: • Vegetable oils, leafy green vegetables • Whole grains, wheat germ, milk, eggs, meat, fish – Symptoms of vitamin E deficiency: • Muscle weakness and muscular dystrophy • Sterility in animals • Anaemia in infants

1. 3. 7 Metabolic Role of Biomolecules • Vitamin K: fat-soluble in its natural form – Properties: 3 types: • K 1: fat-soluble; food-based • K 2: fat-soluble; made by bacteria found in the gut • K 3: water-soluble; man-made; 2 -3 times more potent than K 1 and K 2 – Functions: • Blood clotting – Sources: • K 1: liver and green vegetables; K 2: intestinal bacteria – Symptoms of vitamin K deficiency: • Bleeding - inability of wounds to form clots

1. 3. 7 Metabolic Role of Biomolecules • Vitamin B Complex Vitamins: 8 types 1. 2. 3. 4. 5. 6. 7. 8. – Thiamine (Vitamin B 1) Riboflavin (Vitamin B 2) Niacin/Nicotinic acid/Nicotinate (Vitamin B 3) Pyridoxine (Vitamin B 6) Folic acid/Folate Cyanocobalamin (Vitamin B 12) Pantothenic acid/Pantothenate Biotin Functions: • All 8 vitamins of the B group function as coenzymes (activate enzymes) involved in carbohydrate, protein and DNA metabolism

1. 3. 7 Metabolic Role of Biomolecules • Thiamine (Vitamin B 1): – Properties: • Water-soluble – Function: • Coenzyme in carbohydrate metabolism – Sources: • Pork, wheat germ, yeast, black beans, sunflower seeds – Symptoms of vitamin B 1 deficiency: • Beriberi (neurological and cardiovascular abnormalities)

1. 3. 7 Metabolic Role of Biomolecules • Riboflavin (Vitamin B 2): – Properties: • Water-soluble – Function: • Coenzyme in protein metabolism – Sources: • Organ meats, milk, vegetables – Symptoms of vitamin B 2 deficiency: • Ariboflavinosis (lesions in mouth and lips)

1. 3. 7 Metabolic Role of Biomolecules • Niacin/Nicotinic Acid/Nicotinate (Vitamin B 3): – Properties: • Water-soluble – Function: • Coenzyme in carbohydrate metabolism – Sources: • Meat, peanuts, coffee – Symptoms of vitamin B 3 deficiency: • Pellagra (dermatitis; diarrhoea, dementia)

1. 3. 7 Metabolic Role of Biomolecules • Pyridoxine (Vitamin B 6): – Properties: • Water-soluble – Function: • Coenzyme in protein metabolism – Sources: • Pork, liver, bananas, whole grains – Symptoms of vitamin B 6 deficiency: • Extremely rare; no specific term for B 6 deficiency; symptoms include dermatitis and convulsions

1. 3. 7 Metabolic Role of Biomolecules • Folic Acid/Folate: – Properties: • Water soluble – Function: • Necessary for DNA replication & formation of RBCs – Sources: • Liver, green leafy vegetables – Symptoms of Folic Acid deficiency: • Swollen tongue, heart-burn, diarrhoea, fatigue, depression, megaloblastic anaemia, spina bifida (which can be prevented by pregnant women taking folic acid supplements); most common vitamin deficiency

1. 3. 7 Metabolic Role of Biomolecules • Cyanocobalamin (Vitamin B 12): – Properties: • Water-soluble; stored in the liver – Function: • Necessary for folic acid use in DNA replication – Sources: • Meat, fish, shellfish, poultry, milk – Symptoms of vitamin B 12 deficiency: • Pernicious anaemia (sore tongue, numbness and tingling in hands and feet, depression)

1. 3. 7 Metabolic Role of Biomolecules • Pantothenic Acid/Pantothenate: – Properties: • Water-soluble – Functions: • Coenzyme in carbohydrate, lipid and protein metabolism – Sources: • Liver, egg yolk, milk, brussels sprouts – Symptoms of Pantothenic Acid deficiency: • Extremely rare - has only occurred under experimental conditions; has no specific term

1. 3. 7 Metabolic Role of Biomolecules • Biotin: – Properties: • Water-soluble – Functions: • Coenzyme in lipid, protein, and DNA synthesis – Sources: • Intestinal bacteria can synthesise biotin, liver, meat egg yolk, tomatoes – Symptom of Biotin deficiency: • Dermatitis

1. 3. 7 Metabolic Role of Biomolecules • Ascorbic Acid/Ascorbate (Vitamin C): – Properties: • Water-soluble; most animals can manufacture their own vitamin C - however, primates cannot – Functions: • Formation of collagen - maintenance of skin, gums, cartilage, bones, blood vessels and wound healing; antioxidant; facilitates iron absorption – Sources: • Citrus fruits, green peppers, tomatoes – Symptoms of vitamin C deficiency: • Scurvy (tender, sore gums that bleed very easily; delayed wound healing)

Minerals • Plants: – Calcium (Ca): • Required for the formation of the middle lamella cement that glues neighbouring plant cells together – Magnesium (Mg): (Mg) • Key component of chlorophyll - lack of magnesium leads to a deficiency of chlorophyll and reduction in photosynthesis

Minerals • Animals: – Calcium (Ca): • Required formation of teeth • Growth and maintenance of bone – Iron (Fe): • Key component of haemoglobin - deficiency of iron leads to lack of haemoglobin, resulting in anaemia - tiredness and fatigue

1. 3. 8 Water • Water is vital to life as we know it… – It makes up 70 - 95% of cell mass – It is an excellent solvent in which all biochemical reactions occur – It participates in chemical reactions - e. g. photosynthesis, respiration and digestion – Carries substances around the body of animals and plants – Carries substances into and out of cells – Good absorber of heat energy

Anabolism and Catabolism • Anabolism is the building up of large biomolecules from smaller molecules using energy – e. g. photosynthesis and protein synthesis • Catabolism is the breaking down of large biomolecules into smaller molecules with the release of energy – e. g. respiration and digestion

Mandatory Experiment: to conduct qualitative tests for: a) b) c) d) Starch Fat A Reducing Sugar A Protein

Title: (a) to test for starch • Apparatus/Chemicals: – Record the names of everything you use in the experiment • Method: – – Label test tubes: A and B Add 2 ml starch solution to test tube A Add 2 ml of water to test tube B Add a few drops of iodine solution to both test tubes and mix – Observe any colour changes and repeat experiment • Results: – Test tube A: red-yellow → blue-black – Test tube B: no colour change

Title: (b) to test for fats • Apparatus/Chemicals: – Record the names of everything you use in the experiment • Method: – Label two pieces of brown paper A and B – Drop a few drops of water onto brown paper A (control) – Rub some butter onto brown paper B (test) – Place both pieces of brown paper onto a radiator to dry – Repeat experiment • Results: – Brown paper A: not translucent – Brown paper B: translucent

Title: (c) to test for a reducing sugar • Apparatus/Chemicals: – Record the names of everything you use in the experiment • Method: – – – Label test tubes: A and B Add 2 ml glucose solution to test tube A Add 2 ml of water to test tube B Add 2 ml of Benedict’s reagent to each test tube and mix Observe any colour changes and repeat experiment • Results: – Test tube A: blue → brick red – Test tube B: no colour change

Title: (d) to test for a protein • Apparatus/Chemicals: – Record the names of everything you use in the experiment • Method: – – – Label test tubes: A and B Add 2 ml diluted milk to test tube A Add 2 ml of water to test tube B Add 2 ml of sodium hydroxide to each test tube Add a few drops of copper sulfate solution to both test tubes and mix – Observe any colour changes and repeat experiment • Results: – Test tube A: blue → violet – Test tube B: no colour change