Chapter 3: Nutrition

1
Chapter 3 Nutrition

• Leaving Certificate Biology
• Higher Level

2
Function of Food

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

3
Common Elements in Food

• Carbon C
• Hydrogen H
• Oxygen O
• Nitrogen N
• Phosphorus P
• Sulphur S

4
Elements in Food as Dissolved Salts

• 5 elements present in dissolved salts
• Sodium Na
• Magnesium Mg
• Calcium Ca
• Potassium K
• Chlorine Cl

5
Trace minerals

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

6
Biomolecules

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

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Carbohydrates

• C, H, O Ratio Cx(H2O)y
• Three categories
• Monosaccharides
• Disaccharides
• Polysaccharides (CH2O)n

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Monosaccharides

• 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)

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Disaccharides

• 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

10
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

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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

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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

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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

Glycerol
Fatty acid 1
Fig. 1 A Triglyceride
Fatty acid 2
Fatty acid 3
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Phospholipids

• Phospholipids one fatty acid replaced by a
  phosphate

Glycerol
Fatty acid 1
Fig. 2 A Phospholipid
Fatty acid 2
P
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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

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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)

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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

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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

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1.3.6 Structural Role of Biomolecules
Vitamins

• Structural role
• Vitamins do not have any structural role in
  living organisms

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1.3.7 Metabolic Role of Biomolecules
Vitamins

• 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

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1.3.7 Metabolic Role of Biomolecules

• Vitamin 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

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1.3.7 Metabolic Role of Biomolecules

• 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)

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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

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1.3.7 Metabolic Role of Biomolecules

• 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

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1.3.7 Metabolic Role of Biomolecules

• Vitamin B Complex Vitamins 8 types
• Thiamine (Vitamin B1)
• Riboflavin (Vitamin B2)
• Niacin/Nicotinic acid/Nicotinate (Vitamin B3)
• Pyridoxine (Vitamin B6)
• Folic acid/Folate
• Cyanocobalamin (Vitamin B12)
• Pantothenic acid/Pantothenate
• Biotin
• Functions
• All 8 vitamins of the B group function as
  coenzymes (activate enzymes) involved in
  carbohydrate, protein and DNA metabolism

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1.3.7 Metabolic Role of Biomolecules

• 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)

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1.3.7 Metabolic Role of Biomolecules

• Riboflavin (Vitamin B2)
• Properties
• Water-soluble
• Function
• Coenzyme in protein metabolism
• Sources
• Organ meats, milk, vegetables
• Symptoms of vitamin B2 deficiency
• Ariboflavinosis (lesions in mouth and lips)

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1.3.7 Metabolic Role of Biomolecules

• Niacin/Nicotinic Acid/Nicotinate (Vitamin B3)
• Properties
• Water-soluble
• Function
• Coenzyme in carbohydrate metabolism
• Sources
• Meat, peanuts, coffee
• Symptoms of vitamin B3 deficiency
• Pellagra (dermatitis diarrhoea, dementia)

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1.3.7 Metabolic Role of Biomolecules

• Pyridoxine (Vitamin B6)
• Properties
• Water-soluble
• Function
• Coenzyme in protein metabolism
• Sources
• Pork, liver, bananas, whole grains
• Symptoms of vitamin B6 deficiency
• Extremely rare no specific term for B6
  deficiency symptoms include dermatitis and
  convulsions

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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

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1.3.7 Metabolic Role of Biomolecules

• 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
• Symptoms of vitamin B12 deficiency
• Pernicious anaemia (sore tongue, numbness and
  tingling in hands and feet, depression)

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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

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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

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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)

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Minerals

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

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Minerals

• 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

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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

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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

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Mandatory Experimentto conduct qualitative
tests for

1. Starch
2. Fat
3. A Reducing Sugar
4. A Protein

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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

41
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

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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 Benedicts 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

43
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