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CHAPTER 6: NUTRITION
6.3 Malnutrition6.4 Food digestion
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6.3 Malnutrition
Lack of one or more of the nutrients requiredin the diet to maintain good health will resultin a condition called malnutrition.
Malnutrition can caused by:
a) a reduced intake of nutrients(undernourishment)
b) an inability to use absorbed nutrients
c) the failure to meet a required increase in
nutrient intake d) nutrient losses
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There are three stages to provide
energy in cases of malnutrition. a) the carbohydrates stores in the body are
used.
b) the fat reserved are oxidised. c) proteins in the muscle are broken down.
Finally when protein levels have been
reduced to half their normal value, deathwill occur.
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Nutrient Effect of
deficiency
characteristic
Vitamin B3 Pellagra Dermatitis (skinbecomes red and
inflamed), diarrhoea and
mental disorder.
Vitamin B12 Aneamia Lack of red blood cells
or haemoglobin to
transport oxygen.
Vitamin C Scurvy Bleeding gums, bruised
skin, painful and swallen
joints, weakness.
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Nutrient Effect of deficiency characteristic
Vitamin DCalcium
a) Rickets (children)b) Osteoporosis
(aged adults)
Stunted growth ofbones and teeth,
weak bones
Brittle bones which
are easily brokenIodine a) Goitre (adults)
b) Cretinism
(children)
Enlarged thyroid
glands
Physical and mental
are easily brokenSodium Muscular cramps Sudden and painful
contraction of
muscles.
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Effects of excessive intake of specificnutrients on health.
Nutrient Effect of excessive
intake
characteristic
Carbohydrates
(sugar)
a) Obesity which may
lead to high bloodpressure, diabetes
mellitus, heart
diseases
b) Dental caries
Body weight is more
than 20% of thesuitable body weight
for particular height.
Tooth decay due to the
destruction of teethsenamel by acids which
are produced by
bacteria from
carbohydrate.
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Nutrient Effect of excessive
intake
characteristic
lipids Atherosclerosis (as a result
of saturated animal fats)
The narrowing of arteries
due to saturated fats andcholesterol deposited on the
inner walls of arteries,
thereby reducing the flow of
blood and may eventuallycause blockage in artery.
proteins a) Gout
b) Stones in the kidney
which can damage thekidney
Excessive uric acid deposits
on the joint pain
Uric acid crystalises andforms stones in the kidney.
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Nutrient Effect of excessive
intake
characteristic
Vitamin A Liver damaged The liver fails to
function because livercells die and fibrous
tissues form in the
liver
Mineral
(a)Sodium
a) High blood
pressure
b) Kidney damaged
Fatigue, headache, can
cause bleeding in the
brain (stoke) and
heart failureKidney are overloaded
with the task of
removing excess salts.
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Nutrient Effect of excessive
intake
characteristic
(b) calcium Arteriosclerosis Calcium deposits on
the inner walls of
arteries causing the
arteries to harden andlose their elasticity.
Reduces flow of blood
or forms a blockage.
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Diet-related Diseases The following are examples of heath problems related
to unbalanced diet and the various ways to reduce itsharmful effects and risks.
a) High blood pressure i) excessive intake of food that is rich in saturated
fats and cholesterol leads to atherosclerosis and highblood pressure. The saturated fats and cholesterol are deposited on
the inner wall of arteries. This results inatherosclerosis where the lumen of the arteries t
become smaller and reduced the blood flow. If calcium is deposited and caused walls of the
arteries to harden and lose their elasticity then akind of atherosclerosis called arteriosclerosis isproduced. Hence, blood flow also reduced.
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This causes the heart to pump faster in order toproduce a higher pressure to pump the blood throughthe arteries with smaller lumen. As results, high
pressure is exerted on the arteries, causing anincrease in blood pressure. ii) High blood pressure is also caused by excessive
intake of salts, tea and coffee which can increase therate of heartbeat, thus increasing the blood pressure.
iii) ways to reduce the risk of high blood pressure: Reduced the intake of food which are rich in saturated fats
and cholesterol. Exercise frequently.
Reduce the intake of salts in food as well as tea and coffee. Do not smoke Have enough rest.
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b) Diabetes mellitus
i) Diabetes mellitus is caused by excessiveglucose in the blood and its subsequentexcretion in the urine.
ii) Excessive intake of food rich in sugar
(carbohydrates) can cause diabetes mellitus. iii) obesity can lead to diabetes mellitus.
iv) the risk of diabetes mellitus can bereduced in the following ways: Reduced the intake of food rich in sugar
( carbohydrates)
Exercise frequently.
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C) Osteoporosis i) osteoporosis occurs due to the lack of
calcium, phosphorus and vitamin D in thediet of an adult.
ii) There is low density of the bone mass
and the bones become thin and brittle,and are easily broken.iii) The risk of contacting osteoporosis can
be reduced in the following ways: intake of food rich in calcium, phosphorus
and vitamin D. Exercise frequently.
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kwashiorkor
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kwashiorkor
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Xerophthalmia
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Beri-beri
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Pellagra
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Anaemia
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Scurvy
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Rickets (children)
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0steoporosis (aged adults)
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Goitre
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Cretinism (children)
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Muscular cramps
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Obesity
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Dental caries
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Atherosclerosis
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CORONARY ARTHEROSCLEROSIS
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Gout
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Stones in kidney
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Liver damage
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Kidney damaged
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Arteriosclerosis
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Test Yourself!!
A. Tick (/) if the statement is true and (x) is false.
1. A diet that has too much or little of a specificnutrient can cause certain health problems.
2. Anaemia is caused by the lack of iron and vitaminB12.
3. Lack of iodine causes goitre and rickets.4. Excessive intake of food that is rich in
carbohydrates and lipids can cause cardiovasculardiseases.
5. High blood pressure and atherosclerosis are causedby excessive sodium and calcium intake respectively.
6. Obesity can lead to diabetes mellitus, heartdiseases and dental caries.
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7. A diet low in saturated fats can causediabetes mellitus, high blood pressureand osteoporosis.
8. Excessive intake of salts, tea andcoffee can cause high blood pressure.
9. Smoking can cause high blood pressure.
10. Osteoporosis can be prevented with
the intake of food rich in calcium,phosphorus and vitamin D.
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B. Match the nutrients with the effects ofdeficiency or excessive intake of the nutrients.
Effects of
deficiency
Nutrient Effects of excessive
intake
Scurvy Calcium High blood
pressure
Constipation Lipids AtherosclerosisAnaemia vitaminB12 obesity
Kwashiorkor Sodium
RicketsVitamin C
Carbohydrates
Fibre
Proteins
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What happen to the food after we eat it?
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Food must be broken down into
simpler substances before it can be
absorbed into the blood and carried to
cells throughout the body.
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6.4 Food Digestion
The process of breaking down large andcomplex substances into simple molecules thatcan be absorbed is called digestion.
Carbohydrates, protein and lipid are digestedin the body into simple substances such asglucose, amino acids, fatty acids and glycerols.
These simple substances can be absorbed bythe cell in the body to carry out metabolicprocess in the cells.
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Digestive SystemDigestive System
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Human Digestive System
The human digestive system comprises of thealimentary canal which starts at the mouthand ends at the anus.
The parts of the human digestive system are:
a) mouth b) oesophagus c) stomach d) duodenum (first part of small intestine) e) ileum (rest of small intestine) f) large intestine ) caecum, colon, rectum)
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Alimentary canal
A series oforgans joined in a long tube from
mouth to the anus.
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Digestion involves both physical andchemical processes.
Physical digestion is the breaking downof food particles by the teeth (chewing)into smaller food particles.
This will increase the surface area ofthe food particles for enzyme reaction.
Physical processes also involves
peristalsis which moves the food particledown the alimentary canal.
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Mechanical digestion
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Chemicaldigestion
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Organs that help in digestion are:
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What is digestion?
Process of ___________________
the _________, complex food molecules
into smaller and __________ molecules.
_____________
Digestion
_____________
Digestion
Larger pieces into
___________ pieces
_________ molecules into
simpler molecules
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Digestive System
____________ Canal Other Organs
M________Pharynx
OesophagusS_________
S_________ intestineL_______ intestine
RectumA_______
TongueS_______ glands
L_______G_____ bladderPancreas
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Identify and labelIdentify and label
the parts ofthe parts of
Digestive SystemDigestive System
a) g)
f)
d)
e)
c)
b) h)
i)
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What is digestion?
Process of breaking down
the large, complex food molecules
into smaller and simpler molecules.
Mechanical
Digestion
Chemical
Digestion
Larger pieces into
Smaller pieces
Complex molecules into
Simpler molecules
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Digestive System
Alimentary Canal Other Organs
MouthPharynx
OesophagusStomach
Small intestineLarge intestineRectumAnus
TongueSalivary glands
LiverGall bladderPancreas
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Answers:
a) Gall bladder
b) Pancreas
c) Large intestine
d) Rectume) Anus
f) Oesophagus
g) Liver
h) Stomach
i) Small intestine
Di sti n f C rb h dr t s Pr t ins nd
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Digestion of Carbohydrates, Proteins and
Lipids
i) Digestion in the mouth Food is chewed by the teeth into small
particles to increase the surface area for theaction of enzymes.
The presence of food in the mouth triggersthe secretion of saliva by the three pairs ofsalivary glands.
Saliva contains the enzymes which begins thehydrolysis of starch to maltose.
starch + water maltose
Salivary amylase
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Maltose can not be absorbed by the smallintestinal lining, therefore digestive process
occurs further along the alimentary canal toconvert maltose to glucose.
The pH of saliva is 6.5-7.5,suitable for the
action of salivary amylase. The chewed food is rolled by the tongue into a
mass a bolus in preparation for swallowing.
During swallowing, the bolus enters theoesophagus, a muscular tube lined withepithelial cells and mucus glands.
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Mucus lubricates the movement of the
bolus along the oesophagus by peristalsis,a series of wave-like muscularcontractions along the oesophageal wall.
Peristalsis squeezes the bolus down theeoesophagus until it enters the stomach.
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ii) Digestion in the Stomach The epithelial lining of the stomach contains
gastric juice which consists of mucus,hydrochloric acid and the enzymes pepsin andrennin.
The pH of hydrochloric acid in stomacharound 2.0.
Functions of hydrochloric acid: a) To destroy most bacteria that are present in
food.
b) prepares an optimal pH range of acidic mediumfor the action of the enzymes pepsin and rennin.
c) stops the action of salivary amylase.
Digestion of protein begins in the stomach
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Digestion of protein begins in the stomach. Functions of enzymes in gastric juices:
a) the enzyme pepsin hydrolyses proteininto polypeptides.
Protein + water
polypeptides b) The enzyme rennin coagulates milk by
converting the soluble milk protein(caseinogens), into the insoluble casein.
Caseinogen casein
Pepsin
Enzyme rennin
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The food remains in the stomach for three to
four hour. During this period, food is thoroughly churned
and mixed with gastric juice by theperistaltic contractions of the stomach wall.
The stomach content become a semi-fluidcalled chyme.
Relaxation of the pyloric sphincter allows the
chyme to gradually enter the duodenum.
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iii) Digestion in the Small intestine
The small intestine consists of theduodenum, jejunum and the highly coiledileum.
a) Duodenum The duodenum is the first part of the small
intestine. The duodenum does not have glands to
secrete digestive juices. It receives twosecretions from other parts of thedigestive system for digestion.
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The duodenum receives:
a) bile produced by the liver, stored andreleased from the gall bladder.
Pancreatic juice secreted by the pancreas.
Bile is alkaline and does not containenzymes.
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The functions of bile:
a) emulsifies fats by breaking up largeglobules of fats into small fat droplets inorder to increase the surface area for theaction of the enzyme lipase.
b) prepares an alkaline medium for theaction of enzymes.
c) neutralises the acids in the stomach.
Pancreatic juice is also alkaline andcontains three enzymes which are lipase,amylase and trypsin.
Function of the enzymes in pancreatic juice
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Function of the enzymes in pancreatic juice. a) the enzyme lipase hydrolyses fats into glycerol and
fatty acids.
Lipid droplets + water glycerol + fatty acids
b) enzymes amylase hydrolysed starch (undigested inthe mouth) into maltose.
starch + water maltose
c) the enzyme trypsin hydrolyses polypeptide intopeptides.
Polypeptides + water peptides
lipase
Pancreatic amylase
trypsin
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b) Ileum
The rest of the small intestine after theduodenum is the ileum.
The walls of the ileum contain many
intestinal glands which secrete intestinaljuice.
The intestinal juices is alkaline and
contains enzymes to complete thedigestion of peptides and disaccharides.
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Functions of enzymes in intestinal juices:
a) The enzymes erepsin (peptidase)hydrolyses peptide to amino acids. b) the enzyme maltase hydrolyses maltose
to glucose.
The digestion of other disaccharides: a) The enzyme sucrase hydrolyses sucrose
to glucose and fructose b) the enzyme lactase hydrolyses lactose to
glucose and galactose.
h d f h di i
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At the end of the digestion process:
a) All carbohydrates are digested into the
monosaccharides of glucose, fructose andgalactose.
b) proteins are digested into amino acids.
c) lipids are digested into fatty acids andglycerol.
Vitamin and minerals are extremely small andsoluble and need not be digested.
Cellulose cannot be digested in the humanbody as the enzymes cellulase is not producedin the alimentary canal.
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THE ENDSEE YOU ON FRIDAY.