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2.0: N U T R I T I O N- form two topic

2.0: N U T R I T I O N- form two topic

 

2.0: N U T R I T I O N


Topic outline:

2.1 Concept of nutrition and food nutrients

2.2 Heterotrophic nutrition (nutrition in man)

2.3 Digestive system and digestion

2.4 Nutrition in plant (Autotrophic nutrition)

2.5 Food processing, preservation and storage

 

2.1 Concept of Nutrition and Food Nutrients 

Nutrition –is the process whereby organisms acquire raw materials(nutrients) needed for body activities.  The raw materials (food) used for body activities such as growth, repair, protection and energy. Nutrition stages in animals includes; ingestion, digestion, absorption and assimilation. In plants it involves synthesis.


Importance of nutrition


(i) Provide materials for body growth and development

(ii) Provide materials for body protection against diseases

(iii) Provide materials for repair of body parts

(iv)  Provide materials for body energy

(v) Provide materials for transmission of nerve impulse

 

Modes/types of nutrition

i)   Autotrophic nutrition –is the manufacture of organic food compounds from inorganic materials using chemical or light energy.

 E.g. in green plants, manufacture complex organic  food (eg; glucose C6H12O6) from simple inorganic materials: water and carbon dioxide by using light.

 

Autotrophs –are the organisms that able to manufacture their own complex food molecules from simple inorganic materials.  

E.g. green plants, manufacture their own food by using light energy (photosynthesis).

 

ii)  Heterotrophic nutrition–is the breaking down of manufactured organic food into simpler form that can be absorbed and utilized by cells.

 Heterotrophs –are the organisms that breaking down of already manufactured complex food molecules into smaller absorbable particles.

 E.g. animals.   They are not able to manufacture their own food, but use food manufactured by plants. 

 

Forms of heterotrophic nutrition

i. Holozoic nutrition –taking of complex food substance and converting to simple form.

Types of holozoic nutrition;

a)  Herbivorous –organism feed on plants. Eg; cow

b)  Carnivorous –organism feed on other animals fresh meat. Eg; lion

c)  Omnivorous –organism feed on both plants and meat.

Eg; man

 

ii.          Saprophytic –feeding on dead organic matters. Eg fungi i.e. mushroom.

iii.       Symbiosis –feeding relationship between two species living together.

Types of symbiosis;

a)  Commensalism –feeding relationship between two species whereby one benefit while the other neither benefit nor harmed. Eg; small plants growing on other plants

b)  Mutualism –feeding relationship between two species whereby both benefit. Eg; bacteria and legume plants, bacteria in ruminant digestive system.

 c) Parasitism –feeding relationship between two species whereby one benefit while the other is harmed. Eg; tapeworm in human gut, plasmodium and human etc.

 

 2.2 Heterotrophic Nutrition 


Heterotrophic nutrition–is the breaking down of manufactured organic food into simpler form that can be absorbed and utilized by cells.

 

Types of food substance and their uses in the body

Food nutrients –are organic and inorganic chemical substances present in food stuff. 


Food Function Example of food sources

1. Carbohydrate

- provide body energy

- for structural materials

- cassava

- sugar cane

- maize

- bread

2. Protein

- for growth and repair

- for body protection (immunity)

- provide body energy

- for structural formation

- formation of enzymes, hormones, and other substances

- milk

- legumes, e.g., beans

- egg white

- meat, fish

3. Lipids: fat & oil

- provide body energy

- provide water when respired

- provide insulation, avoid heat loss

- protect organs such as kidney

- for structural materials, e.g., cell membrane

- seeds

- coconut

- butter

- milk

- oils

4. Vitamins

- prevent deficiency diseases

- promote health

- regulate body processes

- fruits, e.g., oranges

- vegetables

- meat, liver

- dairy products

5. Minerals

Ca -strong bones & teeth, conduct nerve impulse Fe -formation of haemoglobin P -part of ATP and nucleic acid, tissues growth Cl -produce hydrochloric acid, water balance, activate enzymes Na, K, Mg –muscle contraction and conduction of nerve impulse

-vegetable -unpolished cereals -egg


Food nutrients –their sources and principal functions               

Balance diet

-is the regular meal containing all necessary food nutrients in a correct proportion.

The components of balance diet are

carbohydrate, protein, lipid, water, mineral salts, vitamins, and roughage.

 

Importance of balance diet

Ø  Provide materials for body growth and development

Ø  Provide materials for body protection against diseases

Ø  Provide materials for repair of body parts

Ø  Provide materials for body energy

Ø  Provide materials for transmission of nerve impulse

 

Nutritional requirement for different groups of people

Type and amount of food required by the body depend on;

  • ActivityBody
  •  size 
  • Sex 
  • Ageweight  
  • State of health       

a) Expectant mothers and lactating mothers -Require more food with high amount of protein; for growth and development of the foetus and milk production.


b) Young children

-Require balance diet with high amount of protein and vitamin; for growth, protection (immunity) and good health


c) Elderly (old age)

-Require balance diet with high amount of protein and vitamin; for body repair, protection and good health. 

Vitamins –their source and principal functions          

d) Sick e.g. living with HIV/AIDS

-Require balance diet with high amount of protein and vitamin for strong immunity to fight the disease.

 

e) Manual workers (hard workers)

-Require more energy giving food like carbohydrates. 


f) Sedentary workers

-Require food with little amount of lipid and carbohydrates (little energy).

 

Causes of lack of balance diet among Tanzania societies

    Poverty –no money to buy some of the food required for balance diet

    Ignorance –no education of food required and their important functions

    Traditions and taboos –some avoid eating some types of food; e.g. pregnant mother is avoided to eat some kind of foods such as eggs in some societies. 

    Some types of food required are not available in some areas 


Nutritional Deficiencies and Disorders

Malnutrition: -is the condition result from too little food, too much food or food lacking some nutrients.

 

Malnutritiondisorders and diseases include; , Anorexia, Beriberi, Constipation,  Anaemia, Night blindness, Etc. 


Nutritional deficiency diseases and disorder in human 


 2.3 Digestive System and Digestion

Digestion –is the broken down of complex food substance into simple soluble form for absorption in the alimentary canal.

 

Mechanical digestion –food is broken down by teeth (mastication or chewing) and by gut muscles(churning) into small particles.

 

Chemical digestion –food is broken down chemically

by enzymes into simple soluble form for absorption

 

Food taken by organism passes through different stages before it is become usable by the body:-

i) Ingestion –taking in food into alimentary canal ii) Digestion 

iii)  Absorption –diffusion of food nutrients into the body/blood after digestion

iv)  Assimilation –utilization of food nutrients for the

body activities

v)    Egestion (Defecation) –removal of undigested food materials through the anus.

 

The process of  digestion is taking place in the alimentary canal.

 

The Human Digestive System (alimentary canal)

 


Fig. 7.1 The human alimentary canal

 

 

Alimentary canal: Parts and Functions

    Teeth –chew food into small particles (mechanical digestion)

    Tongue –roll food into bolus and push food into oesophagus

    Salivary glands –produces saliva 

    Epiglottis –prevent food from entering the air passage

(trachea)

    Oesophagus –pass food by peristalsis

Peristalsis –is the movement of food into the stomach by contraction of oesophagus muscles

NB: -Person can swallow food while standing on his head upside down because peristalsis is not influenced by gravity.

 


 

                                                                Fig. 2.2 Peristaltic movement of food

 

    Cardiac sphincter –avoid back flow of food from stomach to oesophagus.

    Stomach –muscular chamber to store food, mix food by churning and digest protein

    Pyloric sphincter –control movement of food (chyme) into the duodenum 

    Duodenum –is the first portion of small intestine, liver(gall bladder)  and pancreas are connected to this part.

    Liver –produce bile and store some food products. Bile –it emulsify fat into tiny droplets; it is a greenish yellow fluid produced by the liver and stored in the gall bladder.

    Pancreas –produce pancreatic juice to digest protein, lipid, starch and neutralize the acidic food (chime)

    Ileum –is the coiled long portion of small intestine for digestion and absorption. 

-It contains villi for absorption of end products of food. -Ileum produces intestinal juice which digests all types of food.

    Colon and appendix –absorbs water, salts and some vitamin

 

 

 

Alimentary canal: Digestion

A: Digestion in the mouth

-The food digested in the mouth is starch only

 Saliva –dissolve, digest and lubricate food, and enable person to talk.

Saliva contain: ptyalin enzyme (to digest starch to maltose), water(to dissolve food), mucus (to

 

lubricate food) and minerals ions.

 

B:  Digestion in the stomach

-Food digested in the stomach is protein only Stomach gland produce gastric juice which contain:- hydrochloric acid, mucus and enzymes pepsin and rennin.

 

i.  Hydrochloric acid; -kill bacteria present in food

-provide acidic medium for enzymes activity

-convert complex sugar into simple sugar -activate enzymes; pepsin from pepsinogen and rennin from prorenin 

ii.  Mucus –protect the stomach wall against the corrosive hydrochloric acid and enzymes.

 

iii.  Enzymes; pepsin and renin Pepsin –digest protein into peptides

Rennin –solidify milk protein in young mammal. It is to enable the milk protein to stay long in the gut for digestion.

 

 

NB: Pepsin and renin are produced in their inactive forms (pepsinogen and prorenin) to avoid digesting the cells that produce them. They digest proteins; also cells are protein in nature.

 

C: Digestion in the duodenum

Food digested is protein, lipids and starch.  It is the first part where digestion of lipids takes place.

Pancreas is connected to duodenum by pancreatic duct, pancreas produce pancreatic juice.

 

Pancreatic juice contain: 

       Enzymes; 

Lipase –digest lipids to fatty acid and glycerol

Trypsin –digest protein into peptides

Pancreatic amylase –digest starch into maltose  

       Hydrogen carbonate salt –to neutralize the acidic food (chyme) from the stomach.

 

 

D: Digestion in the ileum.

The digestion of all types of food ends in the ileum Ileum produces intestinal juice. 

Intestinal juice contains enzymes 

       Lipase –digest lipids into fatty acids and glycerols

       Maltase –digest maltose into glucose 

       Lactase –digest lactose into glucose and galactose

       Sucrase –digest sucrose into glucose and fructose

       Peptidase (Erepsin) –digest peptides into amino acids



Absorption and fate of end products of digestion  

Absorption mostly takes place at ileum by villli.

       Villi –are the finger like projections in the ileum which increase surface area for absorption of food nutrients

-Amino acids and glucose enter the blood vessels of villi, the glycerol and fatty acids packed as lipoprotein and enter lymph vessel (lacteals) of villi.

                                                         Structure of vill



 Adaptation of the ileum to absorption

  •  It is long –food stay for long time for maximum absorption
  •  It is coiled –food move slowly, take long time for maximum absorption
  • It has numerous villi –to increase surface area for absorption. 
  • It has thin wall –for the food nutrients to diffuse easily   
  • It is well supplied with blood –to transport the absorbed food nutrients.
                                                                                           Ruminant digestive system


                                 



2.4 Nutrition in Plants (Autotrophic nutrition)

–Manufacture of complex organic food molecules from simple inorganic materials using chemical or light energy.

 E.g. Green plants;  manufacture complex organic  food (eg; glucose C6H12O6) from simple inorganic materials:

water and carbon dioxide, by using light.

 

Plants are autotrophs, they manufacture their own food by using sunlight (photosynthesis)  To manufacture food, plants also need mineral salt elements from the soil.

 

Plant mineral nutrients are of two categories;

i) Macro elements –needed by plants in large amount; nitrogen, phosphorus and potassium (N, P, K) ii) Micro elements –needed by plants in small/trace amount. Eg; zinc, copper, manganese  Essential mineral 


Elements in plant and their roles



Photosynthesis 

-is the process by which green plants manufacture their own organic food compounds from inorganic materials using light energy.

 

Site of photosynthesis: photosynthesis take place in the chloroplast.

Chloroplast are found in the green parts of plant ie; leaves


Internal structure of leaf


    Vein –transport materials in leave

    Lamina –green with chlorophyll for photosynthesis

(trap sun light)

    Petiole –attaches leave to stem 



 External structure of leaf


    Cuticle –waxy thin layer to protect and avoid water loss

    Epidermis –thin outer layer to protect inner parts

    Palisade mesophyll –has many chloroplasts to trap sun light for photosynthesis

    Spongy mesophyll –loosely cells layer with air spaces to allow gas to circulate easily

    Stomata –allow gas and water to pass

    Guard cell –with many chloroplasts to control close and opening of stomata. Control amount of water and gas passing in and out.

    Xylem –transport water and mineral salts

    Phloem –transport manufactured food

 

Condition necessary for photosynthesis

i.      Light –provide energy for the process and photolysis

of water.

ii.    Chlorophyll –trap sunlight 

Raw materials for photosynthesis

iii. Carbon dioxide iv. Water –provide hydrogen during photolysis.  -The hydrogen combines with the carbon dioxide to form glucose food.

Photolysis –is the splitting of water molecule by light to produce hydrogen and oxygen. 

 

Therefore; photosynthesis takes place through 2 tages; 

i) Light stage –water split into hydrogen and oxygen by light energy.

ii) Dark reaction(light independent) –the hydrogen combine with carbon dioxide to form glucose food

 

Equation of photosynthesis Word equation:



End products of photosynthesis i) Glucose ii) Oxygen gas iii) Water 

Fate of the end products of photosynthesis

    Glucose is store as starch in plant and some is used during respiration to release energy. Also can be converted into oil or protein.

    Oxygen is used during respiration and the excess is removed out to be used by other organisms.

    Water is used back for photosynthesis, the excess water is removed out during transpiration.

    Some glucose sugar is converted into lipids. Protein is formed by addition of mineral ions from the soil.

 

Importance of photosynthesis

Ø Food production

Ø Energy conversion; it convert light energy from the sun to chemical energy used by organisms

Ø Balance atmospheric gases (carbon dioxide and oxygen)

Ø Produce oxygen used by organism in respiration

 

Factors affecting the rate of photosynthesis

    Light intensity –photosynthesis increase with increase in light intensity to optimum.

    Carbon dioxide concentration

    Temperature –photosynthesis increase with increase in temperature up to optimum. Too much temperature damage leaves chlorophyll and decrease photosynthesis

    Water

 

Examples of plant storage organs;

    Leaves –E.g. onion

    Root –E.g. cassava, carrot, potatoes

    Stem –E.g. sugar cane, yam, 

    Seed and grain –E.g. bean, maize, ground nut

 

Experiments on photosynthesis

1. To test for starch in a leaf Procedures;

    Take a green leaf from a plant in sunlight and dip it in boiling water for 20 seconds

    Remove the leaf from water and dip it in a boiling ethanol using water bath for 2minutes.

    Remove the leaf from ethanol and dip again in the water to soften it and remove the ethanol.

    Add few drops of iodine to the leaf, wash and observe the colour change Observation/Results: The leaf turn blue black, this indicate the presence of starch.

Inference and conclusion

-Therefore during photosynthesis starch is formed.

Questions:

i. Why the leaf dipped in boiling water? ii. Why the leaf dipped in boiling ethanol? iii. Why water bath was used? iv. Why should the leaf from ethanol washed again in the water?

v. Why it was necessary to remove the chlorophyll? vi. Why the leaf washed after adding iodine?

 

Answers:

i. To kill protoplasm ii. To remove chlorophyll (decolourize) iii. Ethanol is flammable, it would catch fire if boiled

directly

iv.   To soften the leaf and remove the ethanol

v.     To seen the colour change properly, (chlorophyll

would mask the colour change)

vi.   To remove excess iodine

 

2. To test the necessity of light in photosynthesis Procedures;

      Fix a piece of hard cardboard on upper and lower surface of leaf in a green plant early in the morning.

      Detach the leaf after several hours and dip it in a boiling water for 20 seconds

      Remove the leaf from water and dip it in a boiling ethanol, use water bath.

      Remove the leaf from ethanol and dip again in the boiling water, or wash.

Add few drops of iodine to the leaf, wash and observe the colour change 


 Set-up to investigate necessity of light for photosynthesis 

 
Observation/Results: The exposed/open parts of the leaf turn blue black, there is starch. The covered part test negative, not turn blue black, there is no starch.

3. To test the necessity of chlorophyll in photosynthesis Procedures;

•    Detach a variegated leaf (leaf with green and non green patches) from a plant in sunlight, and draw it to show the colour pattern

•    Dip it in a boiling water for 20 seconds and then in boiling ethanol for 2minutes,  use water bath.

•    Remove it from ethanol and dip again in the water

•    Add few drops of iodine, wash and observe the colour change

•    Draw the leaf to show the distributions of starch and compare with the first drawing

4. To test whether carbon dioxide is necessary for photosynthesis Procedures;
•  Keep a potted plant in the dark for 12 hours. This will cause the leaves to lack starch

• Insert a shoot into conical flask A containing sodium hydroxide and another shoot in conical flask B

and remove it from the water.

• Insert a glowing splint of wood in the test tube and observe. 

Observation/Results: The glowing splint rekindle (relight), this indicates the presence of oxygen gas.

-During photosynthesis, oxygen gas is produced

Inference and conclusion:

- Therefore, light is necessary for photosynthesis to occur.

Observation/Results: Leaf from conical flask A of sodium hydroxide does not turn blue black, there is no starch because no carbon dioxide.    Leaf from conical flask B turn blue black, there is starch.

Inference and conclusion: 

-Carbon dioxide is necessary for photosynthesis to occur.

Questions:

i.   Why the potted plant kept in the dark a day?

ii. What was the role of sodium hydroxide? iii. Why was the mouth of conical flask A containing sodium hydroxide covered with cotton wool?

iv. Why the experiment set up was exposed to the sun

Observation/Results: The green areas turn blue black, there is starch. The non green areas do not turn blue black, no starch.

golour patterns and (b) distribution in a variegated leaf goo

5. To identify the gas produced during

photosynthesis Procedures;

Arrange the apparatus as shown below 
Containing water, cover with cotton wool. 
NB: Sodium hydroxide absorbs/removes carbon dioxide 
Expose the experiment to the sunlight for 6 hours
Test for starch the leaf from conical flask A of sodium hydroxide,
and then the leaf from conical flask B of water 


  • Expose the experiment to the sunlight until the water in the test tube has been completely displaced
  • Cover the test tube mouth with your thumb finger

 

 

2.5 Food processing, preservation and

storage

Food processing 

-are the processes of treating food to make it good, safe and stay for a long time.

 

Food preservation –process of adding preservatives

chemicals to the food to prevent deterioration (decay)

 

Preservatives –chemical that stop food deterioration by preventing life and activities of microorganism. Examples of preservatives are:-  salts, sugar, honey, sulphur dioxide, organic acids etc.

 

Importance of food processing and preservation

Ø Prolong life of the food

Ø Prevent food decay and spoilt

Ø Keep reserve for the future

Ø Preserve natural state of the food 

  

Methods of food processing and preservation


                   Natural methods


      Smoking –applying smoke to the food, the carbon monoxide kills destructive organisms.

Examples:- for food such as fish, meat, cassava, seeds

 

      Drying –remove water from the food prevent life of microorganisms, organisms cannot live without water. 

Examples:-for food such as cassava, meat, fish, cereals, seeds, vegetables

 

      Salting –adding much salt to the food increase concentration to prevent life of microorganisms by osmosis.

Examples:- for food like meat, fish

 

      Boiling –high temperature kill microorganisms

 

      Pickling –putting food in preservative like honey. Eg; for food like meat

 

                  Modern methods

    Freezing –keeping food at very low temperature, microorganism are not active at very low temperature.

Examples:-for food like meat, fish, vegetables

 

    Canning and bottling –food is heated to kill microorganisms and sealed in airtight can or bottle to avoid oxygen, organisms cannot live without oxygen.  Examples:- for food like fruits, drinks, fish, tomatoes,

meat

 

    Additives –chemical preservatives are added to the food to prevent growth and life of microorganisms. The preservatives are like salt, sugar, sulphur dioxide, organic acids etc.

Examples:- for food such as meat, fish, drinks etc. 

    Pasteurizing (Heating) –Overheating the food to above 600C for several minutes to destroy microorganisms and their enzymes.

Example:- for milk

    Refrigeration –keeping food at low temperature, avoid activities and life of microorganisms. Eg; fruits, vegetables

 

Differences between traditional and modern methods of food processing and preservation




 

 Properties of food substances

Carbohydrates 

-Compound of carbon, hydrogen and oxygen

Types

i) Monosaccharide (simple sugars) –composed of single molecule. E.g; glucose and fructose ii) Disaccharides (complex sugar) –formed by condensation of two monosaccharide molecules.  E.g; sucrose (from sugar cane), maltose, and lactose (from milk) iii) Polysaccharides (complex sugar) –formed by condensation of large number of monosaccharides. E.g.

Starch, cellulose

 

Lipids 

-Compound of carbon, hydrogen and oxygen. More hydrogen than carbohydrate, but lower oxygen content.

Lipids are polymers made of monomers; faty acids and glycerols.

Ø Insoluble in water, soluble in organic solvent

Ø Fat is solid at room temperature while oil is liquid at room temperature

Ø In paper cause it to become translucent

                      

In water, oil form red ring with Sudan III, leaving the water clear

Ø Oil react with osmic acid and turn black

Protein 

-Compound of carbon, hydrogen, oxygen and nitrogen; some contain sulphur and phosphorus as well.

Proteins are polymers made of monomers called amino acids. 

Ø Proteins are insoluble in water

Ø React with Million’s reagent to form purple/reddish colour

Ø React with sodium hydroxide and copper sulphate to produce a violet colour. This is called Biuret test.

 Vitamins

Formed by combination of glucose and some mineral elements. 

Most vitamin are synthesized by autotrophs (green plant), mammals can synthesize vitamin A and D.

 

Water soluble vitamins are C and B, and the rest are fatty soluble (A, D, E and K) 




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