Chapter 3: Nutrition Leaving Certificate Biology Higher Level

Chapter 3: NutritionChapter 3: Nutrition

Leaving Certificate BiologyLeaving Certificate Biology

Higher LevelHigher Level

Function of FoodFunction of Food

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

Common Elements in FoodCommon Elements in Food

– Carbon C

– Hydrogen H

– Oxygen O

– Nitrogen N

– Phosphorus P

– Sulphur S

Elements in Food as Elements in Food as Dissolved SaltsDissolved Salts

• 5 elements present in dissolved salts:

– Sodium Na

– Magnesium Mg

– Calcium Ca

– Potassium K

– Chlorine Cl

Trace mineralsTrace minerals

• 3 trace elements (mineralsminerals) present in living organisms:

– Iron Fe

– Copper Cu

– Zinc Zn

BiomoleculesBiomolecules

• Biomolecules are chemicals found in and produced by living organisms

• There are 4 major types of biomolecules:

– Carbohydrates

– Lipids

– Proteins

– Vitamins

• C, H, O: Ratio: Cx(H2O)y

• Three categories:

– Monosaccharides

– Disaccharides

– Polysaccharides (CH2O)n

CarbohydratesCarbohydrates

MonosaccharidesMonosaccharides

Glucose [C6H12O6] - a reducing sugar and formed by breakdown of glycogen

Fructose [C6H12O6] - a reducing sugar and found in many fruits

Galactose [C6H12O6] - a reducing sugar and formed by breakdown of lactose (found in milk)

DisaccharidesDisaccharides

• Maltose (a reducing sugar)– Found in germinating seeds (e.g. barley)

– Glucose + Glucose → Maltose [C12H22O11] + H2O

• Sucrose (NOT a reducing sugar)– Commonly known as table sugar

– Glucose + Fructose → Sucrose [C12H22O11] + H2O

• Lactose (a reducing sugar)– Found in milk - some people have lactose-intolerance

– Glucose + Galactose → Lactose [C12H22O11] + H2O

PolysaccharidesPolysaccharides

• 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

LipidsLipids

• 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

TriglyceridesTriglycerides

• 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

Glycerol

Fatty acid 1

Fatty acid 2

Fatty acid 3

Fig. 1:A Triglyceride

PhospholipidsPhospholipids

• Phospholipids: one fatty acid replaced by a phosphate

Glycerol

Fatty acid 1

Fatty acid 2

P

Fig. 2:A Phospholipid

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

ProteinsProteins

• 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

VitaminsVitamins

• 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. Structural role:

– Vitamins do not have any structural role in living organisms

1.3.6 Structural Role of Biomolecules1.3.6 Structural Role of Biomolecules

VitaminsVitamins

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 Biomolecules1.3.7 Metabolic Role of Biomolecules

VitaminsVitamins

• Vitamin AVitamin 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


• Vitamin D:– Properties:

• Fat-soluble; 2 types:

– D2 (ergocalciferol - produced by UV action on skin)

– D3 (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)


• 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


• Vitamin K: fat-soluble in its natural form– Properties: 3 types:

• K1: fat-soluble; food-based

• K2: fat-soluble; made by bacteria found in the gut

• K3: water-soluble; man-made; 2-3 times more

potent than K1 and K2

– Functions:• Blood clotting

– Sources:• K1: liver and green vegetables; K2: intestinal bacteria

– Symptoms of vitamin K deficiency:• Bleeding - inability of wounds to form clots


• Vitamin B Complex Vitamins: 8 types1. Thiamine (Vitamin B1)

2. Riboflavin (Vitamin B2)

3. Niacin/Nicotinic acid/Nicotinate (Vitamin B3)

4. Pyridoxine (Vitamin B6)

5. Folic acid/Folate

6. Cyanocobalamin (Vitamin B12)

7. Pantothenic acid/Pantothenate

8. Biotin

– Functions:• All 8 vitamins of the B group function as coenzymes

(activate enzymes) involved in carbohydrate, protein and DNA metabolism


• Thiamine (Vitamin B1):

– Properties:

• Water-soluble

– Function:

• Coenzyme in carbohydrate metabolism

– Sources:

• Pork, wheat germ, yeast, black beans, sunflower seeds

– Symptoms of vitamin B1 deficiency:

• Beriberi (neurological and cardiovascular abnormalities)


• Riboflavin (Vitamin B2):

– Properties:

• Water-soluble

– Function:

• Coenzyme in protein metabolism

– Sources:

• Organ meats, milk, vegetables


• Ariboflavinosis (lesions in mouth and lips)


• Niacin/Nicotinic Acid/Nicotinate (Vitamin B3):

– Properties:

• Water-soluble

– Function:

• Coenzyme in carbohydrate metabolism

– Sources:

• Meat, peanuts, coffee


• Pellagra (dermatitis; diarrhoea, dementia)


• Pyridoxine (Vitamin B6):

– Properties:

• Water-soluble

– Function:

• Coenzyme in protein metabolism

– Sources:

• Pork, liver, bananas, whole grains


• Extremely rare; no specific term for B6 deficiency;

symptoms include dermatitis and convulsions


• 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


• Cyanocobalamin (Vitamin B12):

– Properties:

• Water-soluble; stored in the liver

– Function:

• Necessary for folic acid use in DNA replication

– Sources:

• Meat, fish, shellfish, poultry, milk


• Pernicious anaemia (sore tongue, numbness and

tingling in hands and feet, depression)


• 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


• 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


• 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)


MineralsMinerals

• Plants:– Calcium (Ca):

• Required for the formation of the middle lamella cement that glues neighbouring plant cells together

– Magnesium (Mg)Magnesium (Mg):• Key component of chlorophyll - lack of magnesium

leads to a deficiency of chlorophyll and reduction in photosynthesis

MineralsMinerals

• Animals:– Calcium (Ca):

• Required for 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

1.3.81.3.8 WaterWater• 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 CatabolismAnabolism 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:Mandatory Experiment:to conduct qualitative tests for:to conduct qualitative tests for:

a) Starch

b) Fat

c) A Reducing Sugar

d) A Protein

Title: (a) to test for starchTitle: (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 fatsTitle: (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 sugarTitle: (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 proteinTitle: (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

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Chapter 3: Nutrition Leaving Certificate Biology Higher Level