TOPIC_5._NUTRITION_IN_PLANTS_AND_ANIMALS.pptx

Nutrution in plants and animals biology IGCSE

1. TOPIC .5. NUTRITION IN PLANTS AND ANIMALS

2. Chemicals of life These are chemical organic compounds that constitute the cells, tissues and Organs. The organic compounds are made of carbon, hydrogen and oxygen. A few organic compounds also contain phosphorus, sulphur and Nitrogen. The study of chemical components found in living organisms and the reactions in which they take part is called Biochemistry Such compounds include carbohydrates, Lipids, Proteins, Vitamins Other compounds found in living organisms are described as inorganic eg. mineral salts, water, acids and bases.

3. Carbohydrates Are chemical compounds made up of carbon,hydrogen and Oxygen. The Elements are in the ratio of 1carbon : 2 Hydrogen: 1 Oxygen with a general formula of (CH 2 O) n where "n" is the number of carbon atoms in carbohydrate molecule. Common carbohydrates include starch and sugars.

4. Types of Carbohydrates Monosaccharides Disaccharides Polysaccharides

5. Monosaccharides Are simple carbohydrates with a chemical formula of (CH 2 O) n where n =6 hence the formula is C 6 H 12 O 6 Examples include glucose in the cytoplasm and blood, fructose in fruits and galactose in milk.

6. Properties of Monosaccharides Soluble in water to form sweet solutions. They are crystallisable They are reducing sugars- they reduce copper II Ions in Benedict's solution to red/ brown copper (I) ions. Molecules of monosaccharides link to form complex carbohydrates a process called condensation.

7. Condensation of monosaccharides Monosaccharide + Monosaccharide condensation D isaccharide +water C 6 H 12 O 6 + C 6 H 12 O 6 condensation C 12 H 22 O 11 + H 2 O Glucose + Glucose Maltose + Water Glucose + Fructose Sucrose + Water Glucose + Galactose Lactose + Water The bond that link Monosaccharides molecules is called Glycosidic bond.

8. Functions of Monosaccharides Are oxidised during respiration to produce energy eg. Glucose Form building units of larger carbohydrate when condensed. eg starch in plants and glycogen in animals

9. Disaccharides Carbohydrates formed by linking two monosaccharides through condensation. During condensation of monosaccharides to form disaccharides water molecules are produced. Examples include Sucrose from sugarcane, maltose from cereals eg barley and Lactose in milk. The type of disaccharide formed depends on the monosaccharide unit that enters the compound The bond that holds molecules of monosaccharides and disaccharides is called the Glycosidic bond.

10. Properties of Disaccharides Soluble in water to form sweet solutions They are non- reducing sugars- cannot reduce the copper sulphate in Benedict's solution unless broken to constituent monosaccharides Some are crystals in nature like sucrose when processed. However some disaccharides such as maltose and lactose reduce copper sulphate in Benedict's solution when heated together hence called complex reducing sugars. A Disaccharide can be broken into constituent monosaccharide through a process called hydrolysis in the presence of water. Disaccharides are hydrolysed by enzymes in nature while in the laboratory its achieved by heating with hydrochloric acid.

11. Hydrolysis of Disaccharides Disaccharide + Water hydrolysis Monosaccharide + Monosaccharide C 12 H 22 O 11 + H 2 O C 6 H 12 O 6 + C 6 H 12 O 6 Sucrose + Water Glucose + Fructose Lactose + Water Galactose + Glucose Maltose + Water Glucose + Glucose

12. Functions of disaccharides When Hydrolysed by enzymes into monosaccharides they are used to release energy.

13. Polysaccharides These are complex carbohydrates made up of many monosaccharide molecules. They have a general formula of (C 6 H 10 O 5 ) n where "n" is very large. Examples include: starch, and Cellulose in plants and Glycogen in Animal tissues.

14. Starch. Found in plants Plants rich in starch include Maize, wheat, Potato and Rice Cellulose Exists as a component of the cell wall Has more monosaccharides then starch. Gives the plants cell their definite shape. cellulose molecule may have as many as 14,000 units Glycogen stored carbohydrates in animals tissue Its synthesised from excess glucose Large amounts found in liver and muscle attached to skeleton Fungi also store carbohydrates in form of glycogen Chitin. Structural component of Exoskeleton of arthropods and cell wall of fungal hyphae.

15. Properties of Polysaccharides Insoluble in water. Do not have a sweet taste hence called non sugars Functions of Carbohydrates Source of energy- when oxidised provide energy to the cell Part of structures in plant cells eg cellulose As roughage in humans.

16. 1. Test for Starch Procedure Observation Conclution To 2 ml food solution in a test tube Add three drops of Iodine solution and shake Observe the Colour change Blue black colour observed Starch present

17. Test for Reducing Sugars Procedure Observation Conclusion To 2ml of food substance in a test tube Add 2ml of Benedict's solution and shake Place the test tube in a hot water bath/ heat to boil. for five minutes Observe the colour change Colour changes from blue to green to yellow to Orange/brown / red Reducing sugars present.

18. Test for non Reducing Sugars Procedure Observation Conclution To 2ml of food substance in a test tube Add 3drops of Hydrochloric acid and shake. Place the mixture in a hot water bath/ heat to boil for five minutes Cool the mixture in cold water. Add sodium hydrogen Carbonate drop by drop until fizzing stops Add 2ml of Benedict's solution to the mixture and place in hot water bath/heat to boil for five minutes Observe colour change Colour changes from blue to green to yellow to brown after hydrolysis. Non reducing sugars present

19. Note Hydrochloric acid was added to split complex carbohydrates to simple sugars by hydrolysis. To hydrolyse non reducing sugars to reducing sugars. Sodium hydrogen carbonate was added to neutralise the acidity in the mixture Green colour- traces of reducing sugars Yellow colour- moderate reducing sugars Red/ Brown/Orange- a lot of reducing sugars

20. Starter Activity You are provided with solution W . Describe how to test for Non reducing sugars .

21. 2. LIPIDS

22. Lipids These are organic compounds of carbon, hydrogen and Oxygen. It has fewer Oxygen atoms compared to carbohydrates. For every one atom of oxygen there are 22 atoms of hydrogen Lipids include fats which are solids and oils which are liquids in nature. Fats are found in animals while oils in plants leaves, fruits and seeds while animals like whales contain oils.

23. The building units of lipids is fatty acids and glycerol . Complex lipids like phospholipids , waxes , steroids and cholesterols are synthesised by condensation of glycerol and fatty acids. that is one glycerol molecule to three fatty acids. Nature of lipids depend on fatty acids it contains since glycerols are the same in all lipids. Molecules of lipids are held by Ester bonds

24. Diagrammatic Representation of fat formation + + + CONDENSATION Glycerol 3 fatty acid molecules Tryglyceride ( Fat)

25. Properties of lipids. Insoluble in water but soluble in organic compounds like alcohol to form emulsions. When heated fats melt to form liquid while oils solidify when subjected to low temperatures They are inert (unreactive) hence stored in tissues of organisms.

26. Functions of Lipids Source of Energy - when completely oxidised in the cells they provide twice as much energy as carbohydrates Source of metabolic water - other than energy they also produce metabolic water when oxidised. a property that enables camels stay for longer time without water by oxidising the fats Structural compounds - form the constituents of plasma membrane, while oils are storage materials in some seeds like groundnuts

27. Heat insulation - Deposited under the skin to form an adipose tissue in animals to insulate the body hence reducing heat loss. Protective compound - Fats deposited around the inner delicate organs like the kidney, the heart provide protection against mechanical injury by absorbing shock.

28. Test for Lipids Test Procedure Observation Conclusion Grease Spot test Rub the food substance on a filter paper removing exess. Hold the paper above a flame taking care no to burn. Hold paper against light. observe what happens to the spot where fat was rubbed parmanent translucet sport formed lipids present Emulsion test To melted (oil/ fat) food substance in atest tube Add 4ml of ethanol and shake thoroughly transfer the content to a test tube half full of water Formation of white emulsions presence of fats or oils Sudan III test To 2ml of food food substance( vegetable oil) in a test tube. Add 4 drops of Sudan iii dye in the test tube and note colour change. Red coloured droplets formed Fats present.

29. 3. PROTEINS

30. 3. Proteins Organic compounds of Carbon, hydrogen and Oxygen, however they also contain Nitrogen and or Phosphorus and Sulphur. Proteins like Haemoglobin contain iron hence referred to as iron containing protein. The building unit of Protein is the Amino acid. There are 20 different amino acids in nature The number of carbon atoms differ from one amino acid to another

31. Amino acids consists of amino group (-NH 2 ) of Nitrogen and Hydrogen hence proteins are referred to as Nitrogenous compounds because of the presence of Nitrogen By condensation two amino form a dipeptide molecule held by peptide bond. When more amino acids condense to a protein chain chain called polypeptide The uniqueness of a particular protein is determined by the type and Sequence of Amino acids it contain.

32. Condensation process Amino acid +Amino acid condensation Dipeptide+water Dipeptide +dipeptide Condensation Polypeptide +Water (more than two amino acids) Amino Acids that are synthesised in the body by the liver are called Non Essential amino acids while while those the body cannot synthesised and are provided in the diet are Essential amino acid. Proteins that contain essential amino acid are called first class protein while those that lack one or more amino acid are called non essential amino acids.

33. Properties of Proteins Most proteins When dissolved in water do not form true solution. particles remain suspended in water called colloidal suspensions. Most proteins are denatured by high temperatures above 40 degrees, acids and bases by changing the chemical and physical properties. Proteins are amphoteric- can react with both acids and bases. Being amphoteric they can combine with non protein substances to form conjugated proteins eg iron in haemoglobin and carbohydrate in mucus.

34. Fuctions of Proteins Structural compounds - Proteins are used to make the framework of living system. eg plasma membrane, keratin in hair, horns and feathers,Collagen in connective tissues and Myosin in muscles. As metabolic Regulators - eg Enzymes - organic catalyst which speed up metabolic reactions, hormones- chemical messengers regulating body processes eg growth. antibodies- provide the body with immunity. As source of Energy - when fully oxidised provide the body with energy. only used to provide energy during starvation. Provide the body with the building blocks for growth and repair of worn out tissues.

35. Test For Proteins Procedure Observation Conclusion To 2ml of food substance/solution in a test tube. Add equal amount of 10% Sodium hydroxide solution and shake. Into the mixture add 1% copper sulphate solution drop by drop shakin after each drop. Observe colour change Purple colour observed Protein present.

36. ENZYMES

37. Enzymes Are protein Organic bio-catalyst produced in the living cell to speed up or slow down chemical reaction in the body. A catalyst - A substance which speed up or slow down chemical ( metabolic) reactions in the body without being used up in the reaction. Metabolic reactions(Metabolism) - Chemical reaction within the body

38. Class Activity 1. Other than carbon, hydrogen and Oxygen, what other elements make up the Proteins.(3mks) 2. Name the building blocks of proteins.(1mk) 3. Give a reason why proteins maybe referred to as Nitrogenous compounds. (1mk) 4. Identify the product formed when two amino acids condense. and when more than two amino acids condense. (2mks) 5. Identify the bond that holds proteins molecules together. (1mk) 6. Name two types of amino acids explaining what they are. (4mks) 7. State four properties of proteins. (4mks) 8. Outline four functions of proteins. (4mks) 9. Under what conditions are proteins used as source of Energy.(1mk)

39. Types of Enzymes Intracellular enzymes - Secreted and used within the cells within the cells which produce them e.g. Respiratory enzymes. Extracellular enzymes - Produced within the cells but used outside the cells that produce them e.g. Digestive Enzymes.

40. Naming of Enzymes Trivial Naming Assigning names based on those who discovered them. such names end in “in” e.g. Pepsin, Trypsin,Ptyalin, Renin . Use of suffix- ase. The suffix are is added to the substrate(type of food) or the reaction catalysed.

41. …. Substrate Enzyme Carbohydrate Carbohydrate Amylose Amylase Sucrose Sucrase Maltose Maltase Lipids Lipase Reactions Enzyme Hydrolysis Hydrolase Oxidation Oxidase Reduction Reductase

42. Properties of Enzymes Protein in Nature Enzymes are substrate specific. Can be used and re-used hence efficient in small amount Not used up in the reactions they catalyse. Enzyme Driven reactions are reversible. A + B C + D

43. Properties of Enzymes Protein in Nature Enzymes are substrate specific. Can be used and re-used hence efficient in small amount Not used up in the reactions they catalyse. Enzyme Driven reactions are reversible. A + B C + D

44. Factors affecting Enzymes controlled reactions (i) Temperature. (ii) pH. (iii) Specificity. (iv) Substrate concentration and Enzyme concentration. (v) Enzyme Co-Factors and Co-enzymes. (vi) Enzyme Inhibitors.

45. Temperature

46. pH Most enzymes work best at pH conditions close to 7(neutral) Some enzymes work best at acidic conditions while others at alkaline conditions Enzyme activity decreases as pH changes from Optimum since unfavourable pH Conditions are created. At extreme pH Conditions enzymes are denatured. this therefore means enzymes are pH specific.

47. pH

48. Substrate concentration and enzyme concentration The rate of Enzyme reaction increases with an increase in substrate concentration since there is adequate substrate to be acted upon by the enzyme. Further increase in substrate does not increase the enzyme activity since the active sites of the enzyme are fully occupied and the number of enzyme molecules become a limiting factor However the reaction can be increased by increasing enzyme concentration.

49. Substrate concentration and Enzyme concentration

50. Graph `

51. Enzyme Co-factors and Co- enzymes . Co- factors are Non proteinous substances which activate the enzyme e.g.. metallic ions like magnesium, iron, copper while others are vitamins. these substances should be provided in small amounts. Co- Enzymes - Organic non protein molecules that work in association with particular enzymes and are mostly derived from vitamins.

52. Enzyme Inhibitors Inhibitors are substances which compete with the normal substrate for enzyme active site i. competitive inhibitors Are chemicals related to the normal substrate by having similar shapes the inhibitors occupies the active site longer than the substrate its effect is not permanent hence can be corrected by increasing substrate concentration

53. ii. Non competitive inhibitors They are non competitive since they don't compete with substrate for the active site but instead combine permanently with enzyme molecules blocking the active site hence the enzymes cannot interact with substrate e.g.. poison like cyanide, mercury e.t.c S pecificity A particular enzyme works on a specific substrate or reaction. e.g. salivary amylase on starch/ amylose Two enzymes cannot work on a given substrate.

54. Enzyme Catalase Enzyme catalase is an enzyme present in tissues plants and animals. Its role is to break down toxic hydrogen peroxide produced in the body during cellular metabolism. it would be dangerous if left to accumulate in the body tissues. The compound hydrogen peroxide is broken to less toxic water and oxygen. Hydrogen peroxide catalase water + oxygen Reduction

55. Nutrition Nutrition is the process by which living things obtain nutrients and assimilate them. The food or nutrients acquired are useful for growth and repair of worn out tissues and metabolic activities e.g. respiration. Modes of Nutrition Autotrophism Heterotrophism.

56. Autotrophism Mode of nutrition where living organisms manufacture their own complex food substances such as carbohydrates from simple substances such as carbon (IV) oxide and water using light or chemical energy. Such organisms that make their own food are called Autotrophs. Where sunlight is energy the process is called photosynthesis. Therefore photosynthesis in the process by which green plants manufacture their own complex food substances from simple substances like carbon (IV) oxide and water in the presence of chlorophyll and sunlight. However Some non green plants make their own food with energy obtained from oxidation of chemical substances. a process called Chemosynthesis.

57. Plants are described as primary producers by producing fats, proteins and carbohydrates during photosynthesis used by animals directly or indirectly. During photosynthesis Carbon (IV) oxide from the atmosphere is used while Oxygen is given out and released to the atmosphere as a by-product. During respiration plants and animals use oxygen and give out carbon (iv) oxide. At some point the rate of photosynthesis equals the rate of respiration in plants, this point is called the compensation point. Therefore photosynthesis helps to maintain the level of carbon (IV) oxide and Oxygen fairly constant in the atmosphere.

58. External Structure of the leaf

59. A leaf- a flattened organ attached to the stem or branch of a green plant. The leaf has flattened green surface with photosynthetic tissues called Lamina. In dicots simple leaves have thick midrib with veins forming a network while in monocots the veins are parallel. The veins have xylem and phloem which transport substances in the leaf. The leaf is attached to the branch or stem by the petiole .

60. Internal structure of the leaf

61. 1.Cuticle A thin non- cellular, waxy, waterproof and transparent layer that coats the upper and lower surface of the leaf. Adaptations It is waxy and waterproof to reduces excessive water loss The thin non cellular layer coats the upper surface to protects the inner tissues from mechanical damage and entry of disease causing micro- organisms. Being transparent it allows penetration of light for photosynthesis.

62. 2. Epidermis Thin tissue on the upper and lower surfaces of the leaf Epidermal cells lack chloroplast except the the lower epidermis which has guard cells with chloroplast. It secrets the cuticle Protects inner tissues from mechanical damage and entry of disease causing micro- organism.

63. 3. Guard cells They are special bean- shaped green cells of the epidermis. They have differentially thicker inner and thinner outer walls that decrease and increase there curvature to facilitate the opening and closing of the stomata when the osmotic pressure changes. Have numerous Chloroplasts which photosynthesis to produce glucose that raises the osmotic pressure of the adjacent cells leading to opening of the stomata.

64. 4. Palisade Layer A layer of cells beneath the upper epidermis Has numerous chloroplasts to maximise the rate of photosynthesis They are cylindrical in shape and closely packed to enable maximum absorption of light energy. There position and arrangement near the upper epidermis enables them to maximise on light energy absorption. The long axis perpendicular to the surface ensures maximum light absorption.

65. 5. Spongy mesophyll layer A layer of cells between the palisade and lower epidermis. They are irregular in shape and loosely packed with large air spaces to provide communication pathways through which gases diffuse between cells. The cells are aligned with moisture to facilitate uptake of oxygen and release of carbon (iv) oxide. Have fewer chloroplasts hence explaining why the lower surface of the leaf is lighter than upper surface.

66. 6. Leaf Veins Extensive systems of channels that ensures supply of materials to and from the leaf. The vein has vascular bundle with a xylem and phloem tissues. Xylem conduct water and minerals salts to the leaf cells from the roots. Phloem translocate manufactured food from the leaf cells to the rest of the plant.

67. The Chloroplast

68. Test For Starch in a plant leaf

69. To Investigate the gas produced during photosynthesis

70. Disc- shaped double membrane organelles found in the cytoplasm of some plants providing site for photosynthesis. They have an aqueous matrix called stroma which contain enzymes to speed up the process of photosynthesis. Have thylakoid discs of grana that contain chlorophyll pigments trapping light energy for photosynthesis. The chloroplast have ability to move near the leaf surface during dim light to maximise absorption of light energy for photosynthesis and move to the lower side during bright light to minimise bleaching.

71. Summary of the adaptation of the leaf to its photosynthetic function Broad flat Lamina;to provide a large surface area for the absorption of carbon (iv) oxide and sunlight. Thinness of the leaf; allows light and Carbon (iv) oxide to pass through a short distance to reach photosynthetic cells. Presence of stomata; ensures efficient diffusion of Carbon (iv) oxide into the leaf. The cuticle and epidermis are transparent ;to to allow penetration of light to the palisade cells.

72. Palisade cells are located next to the upper epidermis; and contain numerous chloroplast to receive maximum sunlight. Existence of extensive veins ;which have xylem vessels to conduct water to photosynthetic cells and phloem which translocate photosynthetic products to the rest of the plant. Large air spaces in the spongy mesophyll layer; to allow free circulation of gases. Leaf mosaic; minimises overlapping and overshadowing enabling maximum absorption of light energy.

73. The process of Photosynthesis Photosynthesis occurs in the chloroplast using raw materials such as carbon (iv) oxide and water in the presence of light and chlorophyll molecules. Water and carbon(iv) oxide gas undergo a series of enzyme controlled reaction to form carbohydrates(glucose) and oxygen given out as a by product. The glucose formed is used for respiration to produce energy while excess is converted to starch and stored in the plant. The chemical reactions in photosynthesis occurs in two stages that is light and dark stages.

74. light energy and chlorophyl Carbon (iv) oxide + Water Glucose + Oxygen (simple carbohydrate) 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

75. 1. The light stage (Light dependant stage) Occurs at the Grana of the chloroplast. The chlorophyll molecules absorb light energy used to split water molecules into oxygen and hydrogen atoms a process called photolysis of water. The hydrogen produced is enter the dark stage while oxygen is released to the atmosphere or used for respiration. Some of the solar energy absorbed by chlorophyll molecules is used in the formation of energy rich molecule Adenosine Triphosphate(ATP) which together with hydrogen atoms(ions) are used in dark stage.

76. light energy and chlorophyll 2H 2 O 4H + O 2 Water Hydrogen atom + Oxygen

77. 2. Dark stage(Light Independent stage) Involves a series of enzyme controlled reactions in the stroma of the chloroplast. Carbon (iv) oxide combines with hydrogen atoms to form simple carbohydrates. The energy used in the process is provided by ATP from the light stage reaction. The intermediate product [ CH 2 O] n undergoes further reactions to form simple carbohydrates like glucose. In addition to glucose fatty acids and amino acids are also formed in dark stage.

78. Carbon [iv] oxide + Hydrogen simple carbohydrate + water CO 2 + 4[H] [CH 2 O]n + H 2 O

79. To Investigate the presence of starch in the leaf To investigate the presence of starch in the leaf, the leaf should be exposed to light for sometime to allow the process of photosynthesis to take place. Step 1; dip the leaf in boiling water for 3-4 min to kill the protoplasm, denature enzymes to stop further reactions and open starch grains. Step 2; boil the leaf in methylated spirit/ Ethanol to decolorise it or bleach the chlorophyll making it clear to observe colour change.Boiling methylated spirit/ Ethanol should be done indirectly[ hot water bath] to avoid igniting the highly flammable methylated spirit. Step 3; Wash the leaf in hot water to soften it. Step 4; Spread the leaf on a white tile and add iodine solution to test for starch.

80. Factors Affecting the Rate of Photosynthesis 1.Light Intensity Rate of photosynthesis increases with an increase in light intensity as light energy is provided to facilitate the process. At higher light intensity the rate of photosynthesis begins to levels off when the required intensity is attained. However the rate begins to fall at extremely higher light intensity since the chlorophyll molecules are bleached due to high amount of ultra violet light and other factors become limiting .Plants require red and blue wavelength for photosynthesis.

81. 2. Carbon [IV] oxide Concentration Rate of photosynthesis increases with an increase in carbon [iv] oxide concentration since there is adequate supply of the raw material for the formation of the end products. However further increase in the concentration slows down and finally levels off the rate of photosynthesis since other factors and conditions necessary for the process will be limiting.

82. 3. Temperature Photosynthesis being an enzyme controlled reaction is affected by extreme temperature changes above or below optimum. At low temperature the rate of photosynthesis is slow since the enzymes are inactive. At higher temperatures above optimum the rate of photosynthesis falls sharply since the enzymes are denatured hence no chemical reaction. Temperatures should be kept at optimum.

83. 4. Water Water as draw material for the process of photosynthesis should be provided to facilitate formation of carbohydrate and for the activation of enzymes. Lack of water to the plant will slow down the rate of photosynthesis and the plant may eventually die due to inhibition of several metabolic processes. Slight water deficiency leads to closure of stomata thus preventing absorption of carbon [iv] oxide.

84. To Investigate the factors which are necessary for photosynthesis Light Step 1; cover two or more leaves of a potted plant with light proof material. Step 2; place the plant in the dark for 48 hours Step 3; Transfer the potted plant to light for 2-3 hours Step 4; Detach and uncover the leaves and immediately carry out test for starch.

85. Discussion The plant was kept in the dark for 48 hours to ensure all the starch in it is used up. [Destarch] It was then exposed to light to allow photosynthesis to take place. The light proof material [Alluminium foil] prevented light from reaching the leaf.[ reflecting away light for photosynthesis]. The leaves that had been covered tested negative for starch[ no starch present] since photosynthesis did not take place. The uncovered leaves tested positive for starch[ starch present] photosynthesis took place.

86. 2. carbon [IV] oxide Step 1; Keep a potted plant in the dark for 48 hours Step 2; Insert a leaf of the plant in transparent polythene or conical flask with 20% sodium hydroxide and seal the mouth with petroleum jelly. Step 3; Expose the plant to sunlight for 6 hours. Step 4; Detach the enclosed leaf and test for starch for the leaf and the uncovered leaves.

87. Discussion The plant was kept in the dark to destarch the leaf by using all the starch in the leaf. It was the left in light for 6 hours to allow photosynthesis to take place. Sodium hydroxide was used to absorb carbon [iv] oxide in the conical flask. The mouth of the flask was sealed with petroleum jelly to keep it air tight. When tested for starch the covered leaf in the conical flask with sodium hydroxide had no starch since sodium hydroxide absorbed the carbon [iv] oxide needed for photosynthesis to take place. The other leaf without sodium hydroxide or not covered had starch since photosynthesis took place leading to formation of starch.

88. 3. Chlorophyll Chlorophyll is a photosynthetic green colouring matter in the leaf. However some leaves have patches of different colours e.g. yellow, purple and white which lack chlorophyll hence no photosynthetic activities. Such leaves are called variegated leaves.

89. Discussion A variegated leaf is a leaf with patches of other colours which lack chlorophyll. while non variegated leaf has the chlorophyll pigment covering the whole leaf. When tested for starch the patches of various colours tests negative for starch since no photosynthetic activities takes place in them hence no starch formed. Variegated leaves accumulate less food than a non variegated plants since it has less green patches that are unable to trap light energy for photosynthesis. hence accumulate less food compared to non variegated leaf.

90. Discussion During photosynthesis oxygen gas is produced. it was important to use a sub merged plant [water plant] since its adapted to aquatic environment hence quick and positive result obtained The sodium hydrogen carbonate was used to increase the supply of carbon [iv] oxide for photosynthesis

91. Heterotrophism Mode of nutrition that involves taking in complex food materials such as carbohydrates, proteins and fats obtained plants and other animals, Hence described as Heterotrophs. Heterotrophic modes of nutrition. Holozoic - Mode of nutrition where solid complex materials are ingested, digested and assimilated. Saprophytism- Organisms obtain nutrients from dead organic matter. hence decomposition. Parasitism - An association where one organism the parasite, feeds on or obtain nutrients from the tissues of another organism the host. Symbiosis - An association where two organisms live together and mutually benefit from each other.

92. Dentition This is the description of type of teeth, their arrangement and specialisation. Some of this animals have four different shape, size and type of teeth [ Incisors, Canines, Pre-molars and Molars. hence described as heterodonts. While others have teeth of the same size, type and shape hence called homodonts. These teeth occupy specific position in the jaws.

93. Incisors Flat chisel shaped teeth with sharp ridged edges for cutting and biting food They have one root for anchorage on jaw bone during biting.

94. Canines Conical shaped with pointed tips modified to seize the prey and tear the flesh. They have one root for anchorage on the jaw bone during tearing of flesh.

95. Pre-Molars and Molars Pre- molars have two roots while Molars have three roots. Both have broad surfaces Ridged with cusps on their crown for crushing and grinding of food.

96. Pre- molar Molar

97. Dental Formula This describes the number, type and position of teeth in the jaws of mammals. The teeth recorded represents half the teeth in the upper and lower jaws abbreviated as i for incisors, c for canine, pm for pre-molars and m for molars. Dentition determines the mode of feeding e.g.. Herbivores, Carnivores and Omnivores.

98. Herbivores Animals which feed exclusively on vegetation. They are grouped as Grazers which feed on grass e.g.,cows, donkeys,zebras etc and Browsers feeding on shrubs and herbs e.g. goats giraffe and antelopes.

99. Adaptation of herbivores to there modes of feeding Lack upper incisors and canines but instead have a horny pad against which grass is pressed and cut by lower incisors. Have a long tongue that assist in cutting, turning of grass and moving food during grinding. They have a gap in the lower jaw that separate the canines and pre molars called diastema to create space for turning of grass by the tongue. The teeth have an open enamel in the crown to allow continuous growth to replace worn out surface due to grinding. Open crown with cusps to provide a large surface for grinding vegetation.

100. Diagram Horny pad Diastema

101. Carnivores. Animals which feed exclusively on flesh. most of which are hunters. Such animals have well developed leg muscles for faster movement. Adaptation of carnivores to there mode of feeding . Strong jaws and sharp teeth to grasp the prey. Incisors rare chisel shaped and closely fitted to seize the prey. Canines are long conical and curved to hold, kill and tear the prey. Pre- Molars and Molars are small except for special pre- molars in the lower and upper jaws modified into carnassial teeth which have smooth sides and sharp edges to slice through flesh and crush bones. Jaws are attached to powerful muscles that move jaws up and down by snapping.

102. Diagram

103. Omnivores Animals which feed on both vegetation and flesh. They produce teeth in two sets. Milk teeth - the first set produced and lost between the age of 6 - 12 years. during which 20 teeth are produced. Permanent teeth . teeth produced to replace the milk teeth and an adult has a total of 32 permanent teeth. Adaptation of Omnivores to there mode of feeding.

104. Diagram i

105. Human skull and dentition h lower jaw upper jaw

106. Structure of a Tooth. Externally a tooth has three regions. the Crown above the gum, the root in the jaw and the neck between crown and root. The crown is covered by a hard non living layer called enamel made of calcium phosphate and carbonate. enamel is a protective covering of the tooth and forms surface for biting and grinding of food.

107. The root is composed of dentine with living cells. Within the dentine is pulp cavity with nerves and blood vessels The blood vessels provide nutrients to the living tissues in the dentine and remove waste products The nerves detect heat, cold and pain. The root is fixed in the jaw bone by cement surrounded by fibres.

108. Dental Diseases Tooth decay and most diseases is greatly caused by sugars and starch eaten which become logged between the teeth and teeth cavities, where they are broken down by micro- organisms as food hence giving out acids as waste products. The acids react with enamel and dentine causing them to dissolve hence a hollow area of decayed part is formed. The hollow continues into the pulp cavity affecting the nerves and a lot of pain is felt. There are two main dental diseases

109. Dental Carries Caused by lack of hard food Too much sweet of sugary food Lack of calcium in the diet Lack of vitamin D Lack of cleaning the teeth and general ill health.Hence tooth decay.

110. 2.Periodontal Disease A disease that causes the gum to become soft and flabby so that they may not support the teeth. Couses Lack of vitamin A and C Lack of message of the gum Lack of cleaning of gum

111. Types of periodontal disease Pyorrhoea- A condition where the teeth become loose due to infection of the fibre holding the teeth in the sockets Can be avoided by eating balanced diet, regular brushing of teeth to encourage blood circulation and removing food particles Gingivities - Characterised by the reddening of the gum, bleeding and the presence of pus in the gum.

112. Dental Hygiene Proper care of the teeth require; Regular cleaning or brushing of teeth after every meal. Avoid eating to much sugary food. Eating hard foods, for example raw carrots, cassava, yams and sugar cane. This helps to remove the soft materials from the gums and teeth. It also helps to exercise the teeth. Eating diet rich in calcium, phosphate and vitamins A, C and D. Teeth should be used for their proper purpose. A regular visit to the dentist.

113. Lesson objectives By the end of the lesson the learner should be able to : Outline the components of the digestive system in animals. Describe digestion in the Mouth. Describe the Swallowing process.

114. Digestive System in Animals The system is made up the Alimentary canal [ Digestive tract] and associated with organs such as Liver and the Pancreas.. Other than Digestion and Absorption, the other functions of the digestive system are Ingestion and Egestion. The tract leads from the mouth to the Anus. It consists of Oesophagus, Stomach, Small intestine, [ duodenum and ileum] and Large Intestine.[ caecum,appendix,colon and rectum].

115. The digestive tract of various animals is different depending on the food eaten e.g. Carnivores have relatively short digestive tract with reduced and functionless caecum and appendix since protein which is the bulk of there diet is digested in the gut while Ruminant herbivores such as cows have four chambered stomach to increase the surface area for digestion of cellulose which take time.

116. Gut wall

117. Food Processing along the Digestive tract Complex food molecules like carbohydrates, proteins and fats must be broken down into simpler and soluble molecules before they are absorbed. The break down of the complex food molecules into simpler soluble molecules that can be absorbed into the body is called Digestion Small molecules like vitamins, mineral salts and water are directly absorbed into the blood stream without undergoing digestion. Along the digestive tract, digestion occurs in the following regions, mouth, stomach,duodenum,and ilium.

118. Digestion in the Mouth Food is introduced into the mouth a process called ingestion. The food is mechanically broken down by the help of the teeth by chewing and grinding a process called Mastication which reduces the food to smaller particles to increase the surface area of Enzymatic action and for easy swallowing During mastication the food is moistened and mixed with saliva from the salivary glands located in the mouth.

119. Salivary Glands Sublingual salivary gland- beneath the tongue Sub- mandibuler salivary gland- under jaws Parotid salivary gland- in the cheeks in front of the ears. The saliva produced is a mixture of water, mucus and enzyme Ptyalin or Salivary amylase. The mixture is alkaline due to the presence of bicarbonate ions hence provide suitable medium for the enzymatic activity. Water acts as a solvent and moistens the food while mucus sticks the food into a bolus and lubricates the food and the lining of the mouth.

120. The enzyme digests starch into maltose. The swallowing process The tongue rolls the food into small round masses called boluses and pushes the bolus into the pharynx [back of the mouth]. The soft palate is raised to open the gullet and close the nasal cavity while the epiglottis relaxes to close the wind pipe or trachea and the food the passes into the oesophagus or gullet lined by circular and longitudinal muscles. The rhythmic contraction and relaxation of the muscles facilitates the movement of food along the gullet to the stomach a process called Peristalsis.

121. Peristalsis p

122. Digestion in the Stomach The bolus enter the stomach through a valve called cardiac sphincter. The thick longitudinal and circular muscles that contract and relax enhances churning [the mixing of food] resulting into formation of fluid called chyme. The introduction of food in the stomach stimulates the the secretion of hormone gastrin which stimulate production of gastric juice from gastric glands from the stomach walls

123. Content of Gastric Juice Pepsinogen - Activated to pepsin enzyme which breaks down proteins into peptides. Renin enzyme - Digest protein caseinogen in milk to casein [curd] Hydrochloric Acid - Provides an acidic medium for optimum activities of the enzymes. the acid also kills germs present in the food. Mucus- Prevents the corrosion of the stomach walls by the acid.

124. Digestion in the Duodenum The chyme enters the duodenum through the pyloric sphincter which allows small quantities of chyme to pass at a time. The duodenum receives secretions from the following organs.

125. The liver - has cells which secrete bile into gall bladder which then releases the bile into duodenum through bile duct. The Pancr eas - Lies below the stomach, it secretes hormone secretin and secretion of Digestive juices. The arrival of food in the Duodenum stimulates secretion of hormone secretin from the pancreas which stimulates secretion of pancreatic juice into the duodenum and cholecystokinin from the duodenal wall which stimulates the secretion of bile from the gall bladder.

126. Content of pancreatic juice Pancreatic amylase - speeds up breakdown of remaining starch to maltose. Trypsin - Produced in its inactive form trypsinogen, it digests proteins into peptides Pancreatic lipase - digests lipids into fatty acids and glycerol Sodium Hydrogen Carbonat e- Neutralises the acidic chyme and creates a suitable alkaline medium pancreatic and intestinal enzymes

127. Content of Bile Bile contains two bile salts; Sodium glycocholate and Sodium taurocholate. Roles of the bile salts. Help in breakdown of fats into tiny fat droplets to increase the surface area for digestion a process called Emulsification Provide an alkaline medium for enzymatic activity. Neutralise the acidic chyme from the stomach

128. Illustration of Emulsification e

129. Digestion in the Ilium This is the lowest part of the small intestine and the longest part of the alimentary canal Its inner walls is lined by secretory glands some of which secrets mucus and others secrets intestinal juice or sacks entries Arrival of the food in the Ilium stimulates secretion of intestinal juice.

130. Content of Intestinal Juice Maltase - s peeds up breakdown of maltose to glucose Sucrase - speeds up break down of sucrose to glucose and fructose. Maltase and sucrase completes the digestion of carbohydrates. Peptidase - break down peptides into amino acids Lipase - breaks down lipids into fatty acids and glycerol.

131. Digestion is completed at the Ilium resulting to the formation of watery emulsion of food called chyle containing soluble products of digestion ready for absorption. The canal is lined by epithelial membrane that contain goblet cells secreting mucus. Role of the Mucus Allows the free movement of food materials. Coats the wall of the alimentary canal protecting it being digested by enzymes.

132. Note Enzyme Pepsin and Trypsin are produced in there inactive forms Pepsinogen and Trypsinogen to prevent. Digestion of the walls of the gut. To prevent the digestion of the glands that produce them.

133. Absorption The process by which the soluble end products of digestion diffuse into the cellar lining of the villi into the bloodstream. Absorption of Alcohol, some water, soluble vitamins B and C, water soluble fats take place in the stomach. Adaptation of the Ilium to its function. It is long to provide a large surface area for absorption. It is narrow to bring digested food into close contact with the walls for easier absorption Highly coiled to slow down movement of food to allows more time for absorption and digestion to take place and also increases the surface area of digestion and absorption. Has a thin layer of cell through which digested food diffuses Inner membrane of Ilium has large number of villi and microvilli to increase the surface area of absorption of end products of digestion. Has a dense network of capillaries in the villi into which amino acids, sugar, vitamins, mineral salts some fatty acids and glycerol are absorbed. The presence of lacteals in the villi for absorption of fatty acids and glycerols.

134. Absorption process Amino acids and Glucose pass through the epithelial of the villi and capillary wall by active transport into the blood stream. The capillaries drain into the hepatic portal vain where the amino acids and glucose are carried to the liver before being allowed to join the circulation. Fatty acids and glycerol are absorbed in the lacteals of the villi which drain in the lymphatic vessels then to the circulatory system which is then distributed to all parts of the body.

135. A villus v

136. Assimilation This is the incorporation of the end products of digestion into the cell metabolism Glucose oxidised to release energy during respiration and excess is stored in form of glycogen or as fats underneath the skin. Fatty acids and Glyceral- oxidised to release energy. however most fats combine with glycerol to form neutral fats stored under the skin to insulate the body. Amino acids are used in the synthesis of proteins for general body growth and repair of worn out tissues. may be used to provide energy during starvation. Egestion This is the removal of undigested and indigestible solid substances from the body through the anus.

137. The Caecum and Appendix Caecum and Appendix have no function in human being however in herbivores they contain large number of bacteria which secrets enzyme cellulase that digest cellulose to glucose. The Bacteria and herbivores exist in a symbiotic relationship some of the glucose is used by bacteria while some assimilated by the herbivores.

138. Roughage This is the fibrous and cellulose materials that make up plants. Most mammals lacks the enzyme to digest roughages hence not fully digested e.g. in human beings. In some mammals its digested by help of micro organisms that produce enzyme cellulase to digest since they naturally lacks the enzyme. Roughages provide grip for peristalsis hence lack of roughages results in slow movement of food leading to constipation. [ adds bulk to food for peristalsis to take place.] Water It makes unto 65- 70% of the total body weight Its a universal solvent Cooling the organism Providing a media of transport Facilitating hydrolysis Activation of enzymes

139. Vitamins Organic chemical compounds that are essential for a healthy body. They are obtained fresh fruits and vegetables while are synthesised in the body by activities of micro organisms in the gut e.g. Vitamin K. Lack of vitamins in the diet results in the breakdown of normal body activities and produce deficiency diseases.

140. Test for vitamin C[ascobic acid] t Test Procedure Observation Conclusion Ascorbic acid Put 2ml of DCPIP in a test tube.
Add food solution drop by drop shaking after each drop. Observe and record observation. DCPIP decolorised ascorbic acid present

141. Mineral Salts These are inorganic compounds containing elements useful for body metabolism. Some of these elements are required in small amounts hence called macro-nutrients while others are required in small amounts thus called micro-nutrients or trace elements.

142. Element Source Function in the body Disease deficiency .

143. Factors Determining energy requirements in human beings Basal Metabolic Rate - This is the energy required to maintain normal body functions such as breathing,heartbeat, circulation, body temperature and other body reactions at rest. Its about 760kJ per day. Occupation - Involves all the activities one does. the more manual activities one does the more energy is demanded to maintain the process hence more energy giving food is needed unlike office workers who do less manual work. Age - Young people have more actively dividing cells and are physically active hence require more energy than adults who have less dividing cells and are less active. Body size - Small organisms which have a large surface area to volume ratio lose a lot of energy in form of heat hence require more energy giving food. Big organism which have small surface area to volume ratio lose less heat energy hence less energy required compared to small organisms Sex - Masculine males require more energy than fat females since they have more muscles than fat.