Chapter 6 :

Nutrition

Introduction• Nutrition - process by which

organism obtain energy & nutrient from food

• Need for growth, maintenance & repair of damaged tissues

• Nutrients – substances required for nourishment of an organism

• Types of nutrition is based on how an organism feed for their survival

Types of nutrition

Autotrophic

nutrition

Heterotropic nutrition

Photosynthesis

Chemosynthesis

Holozoic nutrition

Chemoautotrophs

Photoautotrophs

Saprophytism

Parasitism

Saprophytes

Parasite

Autotrophs• Autos : self trophos : feed• Organism which practise autotrophic

nutrition• Synthesis complex organic compound

(food) by their own• Using inorganic substances with the

help of light/chemical energy• By photosynthesis or chemosynthesis

Autotrophs

PhotosynthesisPhotos : light

- Green plants or photoautotroph- Produce organic molecules (food) from CO2 & H2O- Light as a source of energy

ChemosynthesisChemo : chemical

- practise by certain type of bacteria or can be called as chemoautotroph- Produce organic compounds (food) without the help of light- Will oxides inorganic substances such as (hydrogen sulphide or ammonia) to obtain energy

Heterotrophs

• Heteros : other• Cannot synthesis their own nutrition• Organism which practise heterotrophic

nutrition• Obtains energy through the intake &

digestion of organic substances (plant & animal tissues)

• May practise i-holozoic nutrition ii-saprophytism iii-parasitism

i. Holozoic nutrition

• Holo : like zoon : animal• Feed by ingesting solid organic

matter & digest then absorbed it• Eg: human , all animal &

carnivorous plant (capturing & ingesting small insects)

Carnivorous Plants : Venus Flytrap

Carnivorous Plants : Pitcher plant

ii. Saprophytism

• The organism are called as saprophytes, feed on dead & decaying organic matter

• Such as bacteria & fungi

• Digest food externally b4 absorb nutrient

iii. Parasitism• Close association

between 2 organism• Parasite – obtains

nutrient (readily digested food) by living on or in the body of other living organism, host

• Eg : fleas & lice, bacteria, fungi, worms (human alimentary canal)

A cluster of nematodes, the  roundworm of dogs, Toxocara canis

Match the following with correct answer

• Feed on dead & decaying organic matter

• Feed by ingesting solid organic matter & digest then absorbed it

• Obtains nutrient by living on or in the body of host

• Obtains energy through the intake & digestion of organic substances (plant & animal tissues)

• Hetetrophs

• Holozoic nutrition

• Saprophytism

• Parasitism

The Importance of A Balanced DietBalanced diet :

Diet that has all the nutrients in the right amount.

Why it is important: Obtained enough energy Maintain a healthy

body Prevent infection of

disease

Quantity of nutrients depends on

Age

Condition ofHealth

Type ofWork

Sex

Physicals activities

Environment

Body Size

Climate

Balanced diet is a utmost importance to health

• The necessity for a balanced diet in food consumed :

1- Provides energy for all biochemical reaction needed for living. Mammals & birds need energy to maintain body temperature

2- Provides the material needed to build cells & tissues for the growth process

3-To replace damaged & dead cells

* The food in a balanced diet should contain the major nutrients includes carbohydrates, proteins, lipid, mineral salts, vitamins, roughage (dietary fibre) & water (7 classes of food)

* These nutrients must be taken in the correct proprotions to meet the daily requirements of the body

Daily energy requirement• Energy is needed to sustain vital functions – heartbeat,

breathing & maintaining body temperature • It is generated by the oxidation of molecules obtain from

food during cellular respiration• Energy content of food – determined by – burning a known

mass of the food in the presence of oxygen in a bomb calorimeter

• Energy value – the amount of heat generated from the combustion of 1 gram of food

• Unit – joule per gram (J gˉ¹) • 4.2 joules of energy are needed to raise the temperature of

1 g of water by 1°C

• 3 main energy-providing organic molecules are lipids, carbohydrates & proteins

• 1 g of lipid – 37.6 kJ of energy (twice than protein & carbohydrate – almost 18.8 kJ)

• Energy values of proteins = 22.2 kJ gˉ

carbohydrates = 16.7 kJ gˉ¹

Nutrient content in food

• Carbohydrates i. starch ( rice, flour, potatoes &

cereals)

ii. sugar (sugar cane – main

sources)• Proteins meat, fish, egg, milk, cereals• Lipid animals fat, butter, margarine, egg yolk• Others are vitamins, mineral, roughage, water

Vitamins

• Non-protein organic compounds cannot be synthesized by our body

• Needed in small quantity• Cannot be digested & release no energy• Essential for the maintenance of good

health & efficient metabolism• Defficiency in specific vitamins- lead to

specific disease• 2 groups : i. Fat-soluble vitamins ii. Water-soluble vitamins

2 groups of vitamins Fat-soluble vitamins

- Can be stored in body fat- Eg : Vit A, D, E, K

Water-soluble vitamins

- Can’t be stored in body- Have to be supplied in daily

diet constantly- Eg : Vit B & C- Vit B complex – coenzyme ;

work together with enzyme

Vitamin E

Vitamin D

Vitamin K Vitamin A Vitamin B Vitamin A

Sources of Vitamins, their functions and Deficiency effects

Vitamins Source Function Deficiency effects

A Egg, milk, cod liver oil, cheese, liver, papaya

- Good vision- Healthy skin

- Night blindness- Dry scaly skin

B Egg, milk,liver, yeast and cereal

- Preserves the nervous system

- Beriberi- Pellagra- Insomnia

C Fruits, tomato, green vegetable

- Healthy skin- Absorption of iron

- Anemia- Unhealthy skin- Scurvy

D Egg, margarine, fish oil, milk, cheese

- Absorption of calcium and phosphorus- Strong teeth and bones

- Rickets- Tooth decay

E Milk, egg, palm oil, green vegetable, cereal

- Functions of reproductive system

- Sterility

K Liver, tomato, green vegetabe, spinach

- Blood clothing - Difficulty in blood clothing

Minerals

• Simple organic nutrient obtained through the diet (food or drinks)

• Required in small quantities in the ionic form by the body• Do not provide energy• Vital for the maintenance of good health• Babies require more calcium & phosphorus compared to

adults for building strong bones and teeth• Adolescent girls require more iron than adolescent boys

Mineral element

Source Function Deficiency effect

Calcium Egg yolk, milk, cheese, cereal, green vegetable

- Strong bonesand teeth- Blood clothing

- Rickets- Osteoporosis- Tooth decay

Iron Egg yolk, meat, liver, spinach

- Component of the hemoglobin.

- Anemia- Tiredness

Phosphorus

Egg, milk, fish, green vegetable

- Strong teeth and bones

- Rickets- Muscles cramps- Tooth decay

Macrominerals Microminerals

- Required in large quantities- > than 100 mg per day- Eg : Magnesium, potassium, calcium, phosphorus, chlorine, sodium, sulphur

Phosphorus structural comp ofCalcium bones & teeth

Sodium nerve function & osmoticPotassium balance between body cellChlorine - interstitial fliud

- Required in trace amounts- < than 20 mg per day- have very specific functions- Eg : ferum, iodine, zinc, boron, copper molybdenum

Ferum production of haemoglobin

Iodine in thyroxine hormone

Roughage or dietary fibre

• Dietary fibre – indigestible part of plant food consists of mainly cellulose

• Recommended – 25 50g• Eg : in vegetables, nuts, wholemeal

grains, fruits• Passes out of the alimentary canal

in the faeces without being absorbed or assimilated

• Has high holding capacity & provides bulk to the intestinal content (in large intestine)

• Deficiency - constipation

Water• 70% of body is water• Main participant in biochemical reactions• Requires 2 to 2.5 litres of water daily• Loss from body by perspiration – skin, evaporation – lungs

(breathing), excretion – kidney (urine or faeces)• Failure to replace the water lost - dehydration

Food Drinks Sweat

Urine

Breath Faeces Made in

body Water gained total = 2600 cm³

Water lost total = 2600 cm³

Daily water balance

Functions:

Help in the transportationTo soften foodTo dissolve waste productsTo control the concentrationTo control body temperatureTo give shape to the body

Selection of appropriates balanced diet

Food guide pyramid

Malnutrition • Unbalanced diet in which certain nutrients are

lacking, in excess, or in wrong proportions• Protein deficiency - i. Kwashiorkor ; does not

receive sufficient protein in diet – distended stomach, very thin, suffers from diarrhoea, thin hair, a swelling of the body due to retention of fliud in tissues, flaky skin & stunted growth

- ii. Marasmus ; general wasting of body = protein deficiency + lack of energy-providing nutrients, very thin & wrinkled skin, usually occurs in children aged between 9 to 12

Kwashiorkor

Marasmus

• Vitamin deficiency :

- Vitamin C deficiency ; Scurvy ; swollen, bleeding gums & tooth loss

- Effects of overdoses of vitaminsVitamin Effects

C Gastrointestinal upset

A Hair loss, vomiting, bone ache, joint pain, liver & bone pain

E Kidney damage

D Too much calcium in the blood –interferes with the functions of muscles & heart

tissues

K Liver damage &anemia

B6 Numb feet & poor cordination

B3 (niacin) Flushed face & hands

Liver damage

• Mineral deficiency :

- Shortage of ferum ; anemia

- Limited supply of Vit D, calcium & phosphorus ; rickets

- Lacking in calcium ; osteoporosis – bones

becomes porous & break easily

Excessive intake of :i) carbohydrates & lipids – obesity

cardiovascular disease / diabetis melitus /

cancer

ii) sugar - diabetis melitus

iii) vitamins A – hair lose, bone & joint paint,

loss of appetite, liver damage

iv) vitamin D – overload of calcium in blood &

calcification of soft tissues

v) sodium – high blood pressure , heart

disease, stroke & (kidney

stones) kidney failure

vi) Protein – gout = uric acid forms crystal in the soft tissues of the joints.

Food Digestion• Digestion – the process that breaks down

complex food substances to simpler, soluble molecules small enough to absorb

• Substances required by cells to carry out metabolic processes are :

= glucose (starch) to generate energy= amino acids (protein) to synthesise new proteins= glycerol & fatty acids (lipids) to form plasma membrane

Digestion of carbohydrates, proteins & lipids

Take place in the alimentary canal :* A long, muscular tube extend from the mouth to the anus* Divided into specific regions for different digestive processes take

place* Receive digestive juices (from accessory glands)* Food is broken down in stages till dissolved & absorbed* Indigestible residue expelled through the anus

Digestion breaks down :A- starch into glucoseB-proteins into amino acidC-lipids into glycerol & fatty acid

Digestion• Involves physical & chemical processes

i- Physical digestion :

= breaking up of large pieces of food into smaller pieces by mechanical process

= starts in mouth slicing & chewing action of teeth

= in stomach curning action by the contraction of muscles in the stomach wall

= increases the surface area of the food for chemical digestion

ii- Chemical digestion :

= digestive enzymes break down complex food molecules into smaller molecules which enter the bloodstream to transported to whole body

= involves enzymatic hydrolysis

2. Salivary gland

1. Epiglotis

3. Oesophagus

6. Gall blader

7. Pancreas

4. Liver

8. Large intestine

5. Stomach

9. Small intestine

10. Rectum

The components & functions of the human digestive system

• Teeth – cut, tear & grind food• Tongue – helps swallow food• Salivary glands – release enzymes to break down carbohydrates• Epiglottis – prevents food from entering trachea• Oesophagus – tube connecting mouth to stomach• Stomach – i. mixes food with more enzymes to break down proteins ii. Hydrochloric acid kills bacteria • Small intestine – food substances absorbed into the bloodstream• Large intestine – reabsorption of excess water into the bloodstream• Liver – i. removes toxins from bloodstream ii. regulates food substances iii. converts excess amino acids to urea iv. Produces bile• Gall bladder – stores bile which neutralises stomach acid• Pancreas – secretes enzyme to break down carbohydrate, proteins & fats• Rectum – stores faeces• Anus – removal of faeces

Digestion in the mouth• Digestion start here• Chewing action breaks the food into smaller pieces

– exposes > surface area for enzyme’s reaction• Food in mouth will trigger salivary glands (3 pairs) –

secretes saliva – contains salivary amylase• Tongue – ensure food mixed well with saliva• Salivary amylase – hydrolyse starch into maltose• Thoroughly chewed food rolled into a mass called

bolus – preparation for swallowing• Then, bolus enter the throat pharynx (junction of

alimentary canal & passage of air flows into the lungs) oesophagus

• Epiglottis – a cartilage flap – will closed temporarily the airway to prevent food from entering the trachea

Parotidgland

Sublingualgland

Submaxillarygland

• Mucus lubricates the movement of the bolus along oesophagus by peristalsis (series of wave-like muscular contraction along the oesophageal wall)

• The peristalsis action of the eosophagus wall squeezes the bolus down

• Bolus enter the stomach when the cardiac sphincter relaxes

Salive3 salivary glands-Sublingual gland-Parotid gland-Submaxillary gland

Food

Starch Mouth

Site ofdigestion

Digestivejuices

Digestiveenzymes

Salivary amylase

Enzymatic action

Starch maltose+ water

Salivaryamylase

pH

6.5-7.5

Digestion in the stomach• Stomach – thick wall, sausage-shaped organ, muscular sac with a

highly folded inner wall.• Epithelial lining contains gastric glands secretes gastric juice • Foods stay here for a few hours. It is thoroughly curned & mixed with

gastric juice by the peristaltic contraction of the stomach wall• Gastric juice contains :

i. Hydrochloric acid – a) creates the acidic condition (pH 1.5 - 2.0)

for the optimal reaction of enzyme

b) stops the activity of salivary amylase

c) Helps to kill bacteria in food

ii. Enzymes - a) Pepsin : proteins to polypeptides

b) Rennin : caseinogen to casein • Then, contents of stomach become a semi-fluid called chyme• Chyme enters the duodenum when the pyloric sphincter relax

Secretion of gastric juice in the stomach

Food

Protein Stomach

Site ofdigestion

Digestivejuices

Digestiveenzymes

-Pepsin-Rennin

Enzymatic action

Proteins Polypeptides+ water

pepsin

pH

Around 2.0

Gastric juice contains hydrochloric acid & enzymes

Caseinogen casein+ water

rennin

• Small intestine = duodenum + jejunum + ileum

• Duodenum – 1st part ; receive chyme (stomach) & secretion (gall bladder & pancreas)

• The digestion of starch, protein & lipid takes place here

i) Pancreatic amylase : starch maltose

ii)Trypsin : polypeptides peptides

iii) Lipase : lipids fatty acid & glycerol

Digestion in the small intestine

Starch + water maltose Pancreatic amylase

Polypeptides + water peptides Trypsin

Lipid droplet + water peptides Lipase

Bile

- Alkaline greenish-yellow liquid

- Stored in gall bladder

- Contains no digestive enzyme

- Creates alkaline environment

- Reduce the acidity of chyme

- Emulsify lipids by changing

lipids into tiny droplets

Pancreatic juice

- Contains enzymes pancreatic

amylase, trypsin & lipase

- Optimum pH required is

between 7.1 & 8.2

LIVER PANCREASsecretes

Duodenum

• Ileum - The wall secretes intestinal juice

Intestinal juice

i) contains digestive enzymes for digestion of peptides & disaccharides

ii) Require an alkaline medium for optimum reaction

* End of digestion process:-i- all carbohydrates digested into monosaccharides (glucose, fructose

galactose)

-ii- proteins digested into amino acids

-iii- lipids digested into fatty acid & glycerol

-iv- vitamins & mineral (small & soluble – no need to digest)

-v- Dietary fibre – not digested

Protein digestion

Peptides are digested by erepsin (a peptidase) into amino acids

Peptides + water amino acids erepsin

Carbohydrates digestion

Maltose is digested by maltase into glucose

The digestion of sucrose & lactose

Lactose + water glucose + galactose lactase

Sucrose + water glucose + fructose sucrase

Maltose + water glucose maltase

1) Mouth

  Here in the buccal cavity (mouth) the food is masticated (chewed). The buccal and naval cavity also warm up the air so that it does not interfere with enzyme production. The saliva, which contains Carbohydrase enzymes, changes starch into maltose.  

2) Oesophagus

Next the food travels through the oesophagus or gullet which links the mouth and stomach together. These contract and push food along the gut, this is called peristalsis.

3) Liver

The liver breaks up (emulsifies) fats by storing bile (the bile actually comes from the gall bladder). It is also alkaline which is good for the enzymes by giving them a good pH for them in the small intestine.

4) Stomach

The food then enters your stomach. In your stomach starch, fat and protein are digested by enzymes. Hydrochloric acid is present to kill and neutralise bacteria which gives a low pH for the enzymes to work. Enzymes work perfectly at human body temperature at ice temperature, enzymes become deactivated but above body temperature they become denatured. 

 

Pancreas

The pancreas’s job is to produce three types of enzymes in pancreatic juices:Protease enzymes to digest proteins.Lipase enzymes to digest lipids e.g.. Fats.Carbohydrase enzymes to digest carbohydrates.

The small intestine/ileum produces more enzymes to break up more proteins, fats and carbohydrates. It also absorbs the nutrients through the gut wall and into the blood stream through these ingenious cells, the villi which line the small intestine which are specially designed to absorb food efficiently. This process is a form of diffusion. Diffusion is the process of which a substance, commonly gas, transfers from a state of high concentration to low concentration to create balance.

Small Intestine

Large Intestine (Colon) The large intestine absorbs water and indigestible foods are stored here.

Rectum

Cellulose is often contained in foods. This cannot be digested so it must be egested. It is stored as fasces. Finally it comes of of the anus.

Site of digestion

Gland/organ Digestive juice

Enzymes pH Food class

Mouth Salivary glands saliva Salivary amylase

6.3-6.8

Carbohydrates:

Starch maltose

Stomach Gastric gland Gastric juice Pepsin

Rennin

1.5

1.5

Proteins:

Protein polypeptides

Caseinogen casein

Duodenum Liver

Pancreas

Bile, bile salts

Pancreatic juice

None

Pancreatic amylase

Trypsin

Lipase

7.6-8.6

7.1-8.2

7.1-8.2

7.1-8.2

Emulsification of lipids

Carbohydrates:

Starch maltose

Proteins:

Polypeptides peptides

Lipids:

Lipid droplets fatty acids + glycerol

Ileum Intestinal gland Intestinal juice Maltase

Lactase

Sucrase

Erepsin

7.6

7.6

7.6

7.6

7.6

Disaccharides:

Maltose glu + glu

Lactose glu + galac

Sucrose glu + fruc

Proteins:

Peptides amino acids

Digestive system in ruminants

Digestive system in rodents