Form 4 Chapter 6 (b) Nutrition

7/24/2019 Form 4 Chapter 6 (b) Nutrition

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Form 4 Chapter 6 Nutrition (b)

The Human Digestive System

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Protein + water polypeptides

pepsin

Caseinogen casein

Casein polypeptides

rennin

pepsin


Stomach

1. ery little starch digestion and no lipid digestion occur in the stomach.

!. Chemical digestion o# proteins starts"

(a) #astric glands at the stomach epithelium secrete gastric $uice

containing pepsin'rennin' mucusand hydrochloric acid

(b) %epsinhydrolyses proteinsinto peptides

(c) &ennin trans#ormed caseinogen (#ound in mil$) into insoluble

caseinto be hydrolysed by pepsin.

!. *ydrochloric acid

(a) stop the catalysing action o# salivary amylase on carbohydrate

(b) prepare an acidic medium #or pepsin to #unction

(c) $ill all microorganisms

4. +ucus protects the stomach all #rom the digestive actions o# pepsin and

*Cl.,. -he #ood becomes a creamy #luid called chyme(a#ter !, hours).

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Trypsinogen trypsin

enterokinase


Small intestine

1. /mall intestine consists o#

(a) duodenum

(b) 0e0unum

(c) ileum

2. n the duodenum' chime is mi"ed ith bile and pancreatic 0uice.

'. Digestion of proteins"

(a) pancreatic 0uice contains trypsinogen' hich is convertedto trypsin

by enteroinase.

(b) -rypsin can #urther digest protein into small amino acids called

peptides.

(c) repsin (peptidase) completes the hydrolysis o# polypeptides and

peptides to their component amino acids.

4

trypsin

Protein polypeptides

Polypeptides peptidestrypsin

erepsin

Peptides ater amino acids

Polypeptides ater amino acidserepsin


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Sucrose + water glucose + fructosesucrase


Digestion of lipids"

(a) %ile is added into the small intestine hen lipid is present.

(b) %ile brea$s up the lipids into small droplets hich increase the

surface area#or lipase to act on.

(c) *ipase acts on the small droplets o# lipids' hydroly+ing them into

glyceroland fatty acids.

. Digestion of carbohydrates"

(a) %ancreatic amylase hydrolyses starch' glycogen and smaller

polysaccharides to maltose (disaccharide).

(b) Maltasehydrolyses maltose to glucose

(c) *actasehydrolyses lactose to glucose and galactose

(d) Sucrasehydrolyses sucrose to glucose and #ructose

(e) +altase' lactase and sucrase are #ound in the intestinal $uice.

,

lipase3ipids ater glycogen #atty acids

amylase/tarch ater maltose

maltase+altose ater glucose glucose

lactase3actose ater glucose galactose


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Digestion in &uminants and &odents

The Digestive System of a &uminant

1. igestive process

(a) Food mi"ed ith saliva and then digested by symbiotic

microorganisms.

(b) -atty acidand glucoseproduced are absorbed into rumen' then to

the reticulumand form cud.

(c) Cud is regurgitated into the mouth to be reche/ed then re

s/allo/edinto omasumand /ateris absorbed.

(d) t is then passed into the abomasums.

(e) n abomasum' hydrochloric acidand proteaseare secreted to digest

the proteinso# the grass and also o# the microorganisms.

(#) 0hyme#rom abomasums enter small intestine here the rest o# the

digestion continues.

(g) 1bsorptionta$es place in the lo/erhal# o# the small intestine.

(h) n large intestine' /ater' some vitamins and minerals are

absorbed.

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The Digestive System of &at, a &odent

1. -he main structures and organs o# a rat are

(a) ral cavity

(b) /alivary glands

(c) Pharyn"

(d) esophagus

(e) /tomach

(#) /mall intestine (duodenum' 0e0unum' ileum)

(g) Caecum

(h) 3arge intestine (colon' rectum' anus)

2. 7odents have a relatively large caecum containing symbiotic bacteria

that help to digest cellulose' releasing nutrients.

!. 8ll nutrients are absorbed in the small intestine and then #aeces are

removed #or the #irst time.

4. -he #aeces are being reeat again because they still contain a lot o#

nutrients and undigested #ood.

,. -here#ore' the #aeces ill enter the alimentary system #or the second time

to be redigested.

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0omparison 2et/een The Digestive %rocess in Humans, &uminants and

&odents

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%roblems of -ood Digestion

3ncomplete Digestion of -ood

1. ncomplete digestion o# #ood causes indigestion.

2. Cause o# indigestion

a) /alloing #ood ithout su##icient cheing

b) ;ating too much

c) nta$e o# too much o# #atty and spicy #ood

d) ;"cessive consumption o# alcohol

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#allstones %reventing the -lo/ of 2ile

1. %ile contains ater' cholesterol' #ats' bile salts' proteins and bilirubin.

2. # the li>uid bile contains too much cholesterol. %ile salts or

bilirubin' it can harden into gallstone.

!. &hen gallstones get stuc$ in any o# the ducts that carry bile #rom the

liver to the small intestine' they bloc the flo/ of bile.

4. t may also bloc$ pancreatic duct causing gallstone pancreatitis.

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12SO&%T3O 1D 1SS3M3*1T3O

1daptations of the Digestive System for 1bsorption

1. 8bsorption o# digested #ood

(a) ta$es place in the small intestine

(b) starts in the duodenumand is completed in the ileum

2. -he adaptations o# the small intestine to absorb digested #ood are

(a) 8 large surface areaith

i. /mall intestine is long

ii. all o# the small intestine is folded in/ards

iii. the inner sur#ace o# the small intestine is covered ith

#ingerli$e pro0ections called villi.

iv. the epithelial cells o# each villus are covered ith microvilli.

(b) the microvilli is onecell thic

(c) a comprehensive net/or of blood capillaries(capillary

netor$) ithin each villus to transport aay absorbed nutrient

molecules all over the body.

(d) the lacteal ithin each villus transports aay #atty acids'

glycerol and oilsoluble vitamins.

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The Structure of 4illus

1. 8 villus is covered ith epithelium. n the middle o# a villus is a mil$y

hite structure called lacteal. -he lacteal is continuous ith lymphatic

vessels.

2. /urrounding each lacteal is a netor$ o# blood capillaries. -he blood

capillaries o# all villi drain into a vein called the hepatic portal vein.

!. &ater @ atersoluble substances such as simple sugars (glucose'

#ructose and galactose)' amino acids, mineral ions vitamin 2 and 0are

absorbed into the blood capillaries. -he hepatic vein then carries these

#ood substances to the liver.

4. Fatty acids and glycerol di##use into the epithelial cells o# villi here they

combine to #orm fat droplets. -he #at droplets are then deposited into the

lacteal' giving it a mil$y appearance.

,. ther lipids such as cholesterol and lipidsoluble vitamins such as

vitamin 1, D, and 5are also deposited into the lacteal.

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1bsorption in the 0olon

1. -he colon

(a) has no digestive activity

(b) has no villi but the epithelium lining o# its mucosa is #or

absorption

2. -he colon absorbs

(a) /ater

(b) vitamins' including biotin' #olic acid' vitamin A' and several %

vitamins produced by bacteria.

(c) electrolytes6mineralsli$e sodium and chloride

!. Nutrients absorbed are transported to the liver via the hepatic portal

vein.

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-uncti

ons of the *iver

1. Functions o# liver

(a) &emove and stores iron and vitamins 1, D, , and 5

(b) Maes plasma protein(albumin' globulin' #ibrinogen' prothrombin

and haemoglobin)

(c) Deto7ifies poisonous substances(e.g. alcohol' drugs' traces o#

insecticides' herbicides and other to"ic chemicals)

(d) Maintain a constant blood glucoselevel at 9?mgB1??ml o# blood

(convert glucose to glycogen or vice versa)

(e) 0onverts amino acids to glucose(hen body runs out o# glucose)

(#) Maintain a constant blood amino acid level(e"cess amino acid is

converted into urea' hile remainder o# amino acid is changed into

carbohydrate)

(g) &egulation of lipids(e"cess lipids are removed #rom the body'

changed into carbohydrates or sent to #at storage sites)

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(h) &emoves haemoglobin molecules that are old or die(haemoglobin

is converted into bile pigments hile the iron is saved up)

(i) %roduce bile

(0) %roduce heat

($) %roduce cholesterol

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1ssimilation of -ood

The %rocess of 1ssimilation in the *iver

1mino 1cids

8mino acids have to pass through the liver be#ore they reach the blood

circulatory system.

-he liver synthesi=es plasma proteins#rom amino acids.

Plasma proteins have various #unctions' #or e"ample' blood clotting and

osmoregulation.

&hen a short supply o# glucose and glycogen occurs' the liver converts

amino acids into glucose.

;"cess amino acids connot be stored in the body and are bro$en don in

the liver through a process called deamination.

uring deamination' urea' the common nitrogenous aste product o#

humans' is produced and transported to the $idneys to be e"creted.

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#lucose

lucose in the liver is used #or respiration. 8ccording to the needs o# the

body' e7cess glucose is converted into glycogenand stored in the liver.

&hen the blood sugar level #alls and the body' the stored glycogen is

converted bac$ into glucose.

nce the glycogen store in the liver is #ull' e"cess glucose is converted

into lipids by the liver.

*ipids

3ipids hich enter the heart through the subclavian veins are transported

in the bloodstream to body cells.

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The %rocess of 1ssimilation in the 0ells

1mino acids

8mino acids hich enter the cells are used #or the synthesis of

ne/ protoplasmand the repair of damaged tissues.

-hey are also important building bloc$s in the synthesis o#

en+ymes and hormones.

8mino acids are also used in the synthesis o# proteins o# plasma

membrane.

#lucose

&hen the glucose molecules reach the body cells' they are o"idi=ed

to release energy during cellular respiration.

;nergy is re>uired #or the various chemical processes hich ta$e

place in the cell' #or e"ample' in muscle contraction and synthesis

o# proteins.

;"cess glucose is also stored as glycogen is a longchained

carbohydrate molecule that is insoluble in ater.

*ipids

3ipids such as phospholipids and cholesterol are ma0or components

o# plasma membranes

Fats that are stored around organs act as cushions that protect

organs#rom in0uries.

;"cess #ats are stored in the adipose tissue underneath the s$in as

reserve energy.

&hen the body lac$s glucose' #ats are o"idi=ed to release energy.

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-O&M1T3O O- -10S 1D D-01T3O

0olon

1. -he intestinal contents consist o# a mi"ture o# ater' undigested #ood

substances' dead cells and dead bacteria and indigestible #ibre.

2. +ovement o# undigested materials is helped by peristalsis.

!. -he colon reabsorbs almost :?D o# /ater and minerals into the

bloodstream.

4. -he remaining ill #orm the #aeces.

&ectum

1. -he #aeces pass to the rectum #or temporary storage.

2. 8s the #aeces accumulate' pressure in the rectum increases' causing a

desire to e"pel the #aeces #rom the body.

Defecation

1. -he elimination of faecesis $non as defecation.

2. -he muscles around the anus' the opening o# the rectum ill contract

and e0ect the #aeces via the anus.

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Defecation &elated %roblems

1. -hree most common de#ecation related problems are

(a) constipation

(b) colon cancer

(c) haemorrhoids

2. 0onstipation

Condition here #aeces becomes hard' dry' and di##icult to pass and

boel movements do not happen very o#ten.

!. 0olon cancer

8 type o# cancer that develops in the tissues o# the colon. t is cause

by carcinogens and eating a high #at' lo #ibre diet.

4. Hemorrhoids

Condition here the veins around the anus or loer rectum is

sollen and in#lamed. t can be caused by prolonged constipation or

diarrhoea.

,. The importance of high fibre diets"

(a) prevents constipation' colon cancers and haemorrhoids

(b) stimulates peristalsis

(c) helps in eight control through the Estomach#ull #eeling

(d) reduces heart disease

(e) absorbs and eliminates to"ic substances

(#) regulates glucose absorption #or diabetics(g) prevents cancers o# the colon and o# the rectum

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The &ole of Microorganisms in the 0olon

-he colon plays host to to groups o# bacteria

(a) %ene#icial or Egood bacteria

(b) Pathogenic or Ebad bacteria

2eneficial 2acteria

1. ;"amples o# bene#icial bacteria are Bacteroides, Lactobacillus

acidophilus andEscherichia coli.

2. Functions are

(a) digesting fragments of carbohydrate, protein and lipid that ere

not digested in the small intestine

(b) fermenting cellulose fibresthat ere indigestible in the stomach and

in the small intestine

(c) producing amino acidsand vitamins 5and 2comple7.

(d) producing antibioticthat controls the groth o# pathogenic bacteria

!. /peci#ic e"ample

(a) Escherichia coli #eed on undigested material' producing gases and

vitamins A and %comple" (hich are absorbed by the body).

(b) Lactobacillus acidophilus e"cretes the antibiotic acidophillin'

protecting us against the Ebad bacteria.

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%athogenic 2acteria

1. Pathogenic bacteria o# the large intestine

(a) cause disease that ma$e us sic$

(b) putre#y undigested protein

(c) produce carcinogens

2. Carcinogens increase the ris$ o# contracting colon cancer.

!. ;"amples o# Ebad bacteria are certain strains o# Eschericia coli and

Clostridia' hich produce carcinogens.

The ffect of 1ntibiotics on Microorganisms in the 0olon

1. 8ntibiotics are a group o# drugs commonly ta$en to treat bacterial

in#ections.

2. 8ntibiotics $ill bad bacteria' but good bacteria as ell.

!. # bene#icial bacteria is completely $illed' pathogenic bacteria ill

repopulate the colon rapidly' bringing about an in#ection.

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Health %roblems &elated To ating Habits

1) #astritis

1. astritis is the inflammation of the lining of the stomach /all.

2. -here are various causes o# gastritis

a) rregular meals G hen a person s$ips a certain meal the stomach

ill be empty. -he aciic gastric 0uice produce by the stomach ill

act on the lining o# the stomach instead' gradually corroding it.

/ometimes gastric ulcers are also #ormed.

b) ;"cessive smo$ing

c) 8lcoholism

d) /tress

e) nsu##icient cheing G i# #ood is not cheed properly' the stomach

all ill be burdened to churn #ood more thoroughly to brea$ up

the #ood.

#) Prolonged inta$e o# drugs such as pain$illers.

g) Helicobacter pyloribacteria hich brea$ don the mucus on the

sur#ace o# stomach lining' e"posing the lining to the direct action o#

gastric 0uices.

!. astritis can be treated by antacids. 8ntacids contain alalishich

can neutralise the hydrochloric acid in gastric 0uice.

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2) Obesity

1. &hen a person eats more than the body needs' e"cess #ood ill be stored

in the body as #ats. -his can lead to obesity.

2. 8 person is said to be obese i# hisBher body eight e"ceeds the right

eight #or hisBher height by 2?D or more.

!. %+ (%ody +ass nde") can be calculated using the #olloing #ormula

BMI=masskg

heightm2

8 %+ o# 19., G 24.: is considered ideal. 8 person is said to be obese i#

his %+ is !? or more.

4. besity predisposes a person to various health problems such as high

blood pressure, heart diseasesand disbetes mellitus. *oever' obesity

can be overcome by atching oneHs diet and e"ercising regularly to helpburn o## #at.

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0) 1nore7ia nervosa

1. 8nore"ia nervosa is characterised by the loss of the desire to eat, due to

an obsession of maintaining a slim body. t is more common among

young single #emales.

2. 8n anore"ic intentionally starves hersel# and ill there#ore become

emaciated over time. /he has a lo basal metabolic rate and her

mentruation may stop

!. # untreated' an anore"ic patient may ultimately die of severe

undernourishment and mal#unctioning o# organ systems.

4. -reament consists o# psychological therapy and regulation o# diets.

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D) 2ulimia

1. 3i$e anore"ia nerosa' bulilia typically a##ects young #emales.

!. t is characterised by uncontrollable overeating follo/ed by forced

purgin or vomiting.

!. ut o# #ear o# being overeight' a bulimic patient ho has been binging

may induce voiting by digging into her throat or by ta$ing purgatives.

%ulimia can cause undernourishment. t can aso lead to $idney and liver

problem and hormonal imbalance.

4. /tress and depression are among the underlying #actors. -hus' the

treatment o# bulimia includes medical treatment coupled ith

counselling.

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%hotosynthesis

1) Macronutrients and Micronutrients for %lants

+acronutrients

Mineral

elements

-unctions ffects of deficiency

Carbon

*ydrogen

"ygen

-hese elements are the components are the

components o# carbohydrates in plants

"ygen is needed #or respiration

/tunted groth (de#iciency is

rare)

Nitrogen For the synthesis o# proteins

For building protoplasm

For the synthesis o# chlorophyll

For the synthesis o# nucleic acids

Ielloing o# leaves

(chlorosis)

+agnesium For the synthesis o# chlorophyll

8ctivates respiratory en=ymes

Chlorosis

eath o# parts o# or entire

lea#

Phosphorus For the synthesis o# proteins' 8-P and

nucleic acids

Needed #or cell division

For groth and maturation

For ripening o# #ruits

ar$ green leaves ith red

spots

/tunted groth and slo

maturation

/lo #ruit ripening

Potassium Needed #or the synthesis o# proteins and

starch

/timulates cell division

8ctivates en=ymes

Chlorosis

eath o# lea# margin and tip

/tunted groth

/o#t stem

/ulphur For the synthesis o# proteins and nucleic

acids

For cell division

Pale leaves

3eaves #all o## easily

/tunted root groth

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+icronutrientsMineral

elements

-unctions ffects of deficiency

%oron Needed #or carbohydrate metabolism

For normal cell division in meristems

*elps in the translocation o# sugars in

plants

/tunted and abnormal

groth eath o# shoot tips

Curled leaves hich

brea$ easily

Copper 8s a component o# en=ymes in

photosynthesis and respiration

Needed #or nitrogen metabolism

Needed #or #loer #ormation

/tunted and abnormal

groth

eath o# shoot tips

%ron spots on youngleaves

Ferum For the synthesis o# chlorophyll

8s a component o# respiratory en=yme

Chlorosis in regions in

beteen veins o# young

+anganese 8ctivates en=ymes in photosynthesis and

respiration

3eaves ith yello

patches

+olybdenum Needed #or the synthesis o# amino acids

nvolved in nitrogen #i"ation

Chlorosis in regions

beteen the veins #ormature leaves

/lightly stunted groth

Jinc Needed #or carbohydrate metabolism

For the synthesis o# au"in hich is

needed #or plant groth

/tunted groth

+ottled leaves

3eaves ith yello

patches

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2) 1daptation of leaf for optimal photosynthesis

1. -he arrangement o# leaves on a plant ensures minimal overlapping' so that each lea#

can receive sunlight. /uch an arrangement is called a leaf mosaic.

2. 3eaves are usually hori+ontal and broad#or ma"imum light absorption. -his

provides leaves ith a large surface area#or the absorption o# sunlight and carbon

dio"ide.

!. 3eaves are also typically thin. -his allos sunlight and carbon dio"ide to reach every

mesophyll cell in the lea# easily.

4. -he internal structure o# a dicot lea# is as shon.

,. -here are openings called stomataon the epidermis' especially the loer epidermis./tomata allo gases to enter the lea# since the cuticleis impermeable to gases. -he

opening and closing o# stomata are controlled by a pair o# guard cells.

6. n dicot leaves' the mesophyll is divided into palisade mesophyll and spongy

mesophyll.

a. -he palisade mesophylllies 0ust belo the upper epidermis. t receives plenty o#

sunlight. Cells o# the palisade mesophyll are rich in chloroplasts. -hey are

cylindrical and are closely pac$ed vertically to enable them to absorb ma"imum

sunlight.

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b. -he spongy mesophylllies beneath the palisade mesophyll and receive less

sunlight as light has to pass through the palisade mesophyll #irst. -hus' cells o#

the spongy mesophyll contain #eer chloroplasts. -he spongy mesophyll cells are

spherical and loosely arranged ith intercellular spaces in beteen them.

5. /tomata and all the spaces in the spongy mesophyll #orm a ventilation system hich

allos gaseous e"change to occur beteen the lea# and the surrounding air.

9. -he midrib and veins also contain vascular tissues' namely "ylem and phloem.

a. 8ylem t transports /ater and mineralsto the mesophyll cells #or

photosynthesis.

b. %hloemG t transports the products of photosynthesis#rom the leaves to all

parts o# the plant

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0) 1daptation of plants from different habitats to carry out photosynthesis

Type of

habitat

7ample of

plant

Distribution of stomata Distribution of chloroplasts

-errestrial

habitat ith

su##icient

ater supply

*ibiscus /tomata #ound mostly on the loer

epidermis hich is shaded #rom

direct sunglight.

-his allos the plant to absorb

carbon dio"ide ithout losing too

much ater

+ost chloroplasts are #ound

in the palisade mesophyll #or

ma"imum light absorption.

/pongy mesophyll has

chloroplasts too' but less than

polisade mesophyll as it

receives less light compared

to palisade mesophyll

Floating on

ater

&ater lily /tomata are #ound on the upper

epidermis as loer epidermis is in

ater.

3eaves are broad and hence have a

larger number o# stomata.

-he upper epidermis is covered ith

a thic$ culticle to prevent loss o#

ater #rom epidermal cells

+ost chloroplasts are #ound

in the palisade mesophyll'

and less in the spongy

mesophyll

-otal

immersion in

ater

Hydrilla No stomata on leaves

3eaves have no cuticle as the plant is

in ater and there is no ris$ o#

ater loss

aseous e"change can occur

throughout the lea# sur#ace. *ence

there is no need #or stomata

Chloroplasts are evenly

distributed among the cells in

the leaves.

Chloroplasts are also #ound in

the stems #or additional light

absorption

ry areas such

as deserts

Cactus +ost o# the leaves are modi#ied to

#orm thorns to reduce loss o# ater

+ost o# the stomata are #ound on the

stem. -he stem is covered ith a

thic$ cuticle.

+any desert plants have sun$en

stomata to reduce the loss o# ater

by transpiration.

esert plants open their stomata at

night to absorb carbon dio"ide and

store it in the plant. uring the

day' they close their stomata and

use the stored carbon di"iode #or

photosynthesis.

Chloroplasts are #ound in the

cells o# the stem.

Chloroplasts are also #ound on

green thorns

/ome desert plants have a #e

leaves. n these leaves' the

chloroplasts are distributed

mainly in the palisade

mesophyll and less in the

spongy mesophyll.

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The Mechanism of %hotosynthesis

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The &ate of %hotosynthesis throughout the Day

1. &hen the sun rises' light intensity and the temperature o# the surroundings gradually

increase' pea$s at midday and gradually decrease until sunset.

2. enerally throughout the day' the rate o# photosynthesis is

(a) much higher on hot sunny day (8) than cool cloudy day (%)(b) because o# a higher rate o# en=yme reaction (due to the higher temperature) and a

higher light intensity (re>uired #or the light reaction)

!. n the morning' both graph 8 and % increase in the rate o# photosynthesis.

4. -hen' both gradually slo don and the ma"imum is reach sometime a#ter sunrise.

,. -he ma"imum rates are constant beteen late morning' midday and early a#ternoon.

9. -he ma"imum rate o# photosynthesis #or 8 may be caused by either o# these limiting

#actors temperature, light intensity and 0O!concentration.

5. For %' the limiting #actor is either temperature or light intensity.

9. 8 #e hours be#ore sunset' the rates o# photosynthesis o# 8 and % gradually drop' then

decrease rapidly and ending gradually until a#ter sunset (K).

:. -he portion 8indicates that the dar reactiono# photosynthesis is still ta$ing place'

although there is no more sunlight.

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3ncreasing the %roductivity of 0rops

1. Countries hich e"periencing #our seasons' light intensity and temperature that are

not constant a##ecting the crop production in these countries.

2. -here#ore' they use the $noledge o# ho the #actors a##ect the rate o# photosynthesis.

*ence' greenhousesare introduced.

!. t can prevent damage brought about by strong inds' rain and hailstorms.

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Technology :sed in -ood %roduction

1) Direct seeding for rice

1. /eed are son directly into the paddy #ield using special drills. No transplanting

is needed later on.

2. -he advantages o# direct seeding includei. 3ess damage to the paddy plants as the method does not involve

transplanting.

ii. /horter maturation time' alloing planting o# more than one crop in a

year.

iii. /aves labour and the cost o# production.

2) Hydroponics and aeroponics

1. *ydroponics and aeroponics are to methods are to methods o# planting

ithout using soil. -hey are usually used #or groing vegetables.

2. n hydroponics' the plants are placed in special containers' ith their roots

immersed in a culture solution to provide all the macro and micronutrient needed

by the plants.

!. -he plants are supported by sand or pebbles in the containers. -he culture

solution in the containers is replenished constantly as minerals are gradually

depleted by the plants and must be aerated to supply o"ygen #or plant roots to

respire.

4. n the aeroponics' the vegetables are supported by some #rameor$ ith their rootssuspended in midair in an enclosed chamber.

,. -he e"posed roots are sprayed ith complete culture solution and ater alternately

#rom time to time. -he complete culture solution provides all the mineral nutrients

needed by the plants.

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6. -he advantages o# hydroponics and aeroponics are

a) No soil or land is needed

b) /pacesaving since the vegetable can be planted close together.

c) -emperature' light intensity and pests can be easily monitored and controlled.

d) egetables are provided ith all the mineral nutrients they need. *ence' they are

li$ely to produce better yield.

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0) Selectively 2reeding

1. /elective breeding is a method o# producing good crop plants or farm animals by

crossing parent plants or animals of desirable characteristics.

2. esirable characteristics include high yield' shorter maturation time' resistance to

pests and diseases' and higher nutritional value.!. 8n e"ample o# selective breeding o# crop plant is seen in the breeding o# oil palm.

4. n oil palm' desirable characteristics include a thic$ mesocarp and big $ernel (oilrich

parts o# the #ruit)' and a thin shell (hich ma$es crac$ing easier).

,. -heDuraoil palm #ruit has a thin mesocarp (undesirable)' a big $ernel (desirable) and

a thic$ shell (undesirable). n the other hand' thePisiferaoil palm #ruit hasa thic$

mesocarp (desirable)' thin shell (desirable) but a small $ernel (undesirable).

6. -he to varieties ere success#ully crossed to produce a ne and ideal variety called

the Tenera. -he Teneraoil palm #ruit has a thic$ mesocarp' a thin shell and a big

$ernel.

D) Tissue culture

1. n this techni>ue' plant cells or tissues are stimulated to divide mitotically to form

entire crop plants(clones) hich are identical to the parent plant.

2. 8ll the plants produced by tissue culture are identical to one another and to the parentplant because they are the result o# mitosis.

) #enetic engineering

1. enetic engineering is a techni>ue hereby a gene /hich codes for a certain

desirable characteristic is inserted into the D1 of organisms, so that it possesses

that desirable characteristic.For e"ample' a gene hich codes #or resistance to

diseases can be inserted into the N8 o# a crop plant so that it ill become resistant

to diseases. ther desired good characteristics include high yield and short maturationtime.

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2. enetic engineering has success#ully produced a variety o# heat hich contains

high>uality proteins' soy beans hich contain all essential amino acids' and Egolden

rice hich is rich in betacarotene.

!. enetically engineered organisms (organisms hich have received #oreign genes) are

$non as transgenic organisms. Foods produced by means o# genetic engineering arecalled geneticallymodi#ied #ood (+F).

-) 2iological control

1. %iological control is the control of pests by using their natural enemies or

predators. For e"ample' rats in oil palm estates can be controlled by rearing ols or

sna$es to eat them. %iological control does not pollute the environment. t is also cost

e##ective.

4!


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Technological Development in -ood %rocessing

1) The necessity for food processing

1. Food processing means physically andBor chemically treating #ood and altering their

natural state.

2. -here is necessity to process #ood.a) -o prevent spoilage and astage o# #ood.

b) -o ma$e #ood last longer so that it can be transported over long distances.

c) -o ensure that #ood is available the hole year round.

d) -o prevent #ood poisoning caused by consumption o# spoil #ood.

e) -o ma$e #ood more attractive to consumers and hence increase its commercial

value.

#) -o diversi#y the users o# #ood. For e"ample' mil$ can be made into cheese'

yoghurt' butter and chocolateL hile soy bean can be made into beancurd' soya

bean poder and soy sauce.

2) Methods used in food processing

Methods Techni;ue to prevent food spoilage 0an be used on

0ooing High temperaturein coo$ing ills microorganisms

and denatures en+ymesneeded to brea$ don #ood.

Foods should be coo$ed thoroughly to ensure all the

microorganisms in them are $illed

+eat' #ish

:sing salt,

sugar orvinegar

-he addition o# sugar or salt gives rise to a

hypertonic solution. 8ny microorganisms present inthe #ood /ill lose /ater to the hypertonic solution

by osmosisand die o# dehydration. inegar contains

acetic acid. ts lo/ pHcan $ill microorganisms that

may be present in #ood.

Salt"Fish' eggs and

vegetablesSugar"Fruits

4inegar"nion and ginger

-ermentation Ieats is added to #ood to cause #ermentation' hich

produces ethanol that $ills other microorganisms.

-apioca' soya beans

Drying &hen #ood is dried' the microorganisms in it are

either $illed or ill #orm spores hich are inactive.

rying can be don under the hot sun or through

mechanical means li$e in an oven.

Drying by hot sun"

anchovies' shrimps and

s>uids

Drying by oven"mil$ and

#lour

%asteuri+ation +il$ is either heated at a temperature o# 6!oC #or !?

minutes' or 52oC #or 1, seconds' #olloed by

immediate cooling. Pasteuri=ation is better than

boiling because it helps preserve the nutrients in

mil' pasteuri=ed mil$ has a limited lifespanor

shel#li#e. Pasteuri=ed #oods can be $ept #or about a

ee$ in a re#rigerator.

+il$' yoghurt and #ruit

0uices.

0anning n the canning process' #ood is #irst sterili=ed at ahigh temperature o# 121oC under high pressure and

+eat' #ish' #ruits andvegetables

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then sealed. -he high temperature ills

microorganismsand destroys their spores. *ence'

canned #oods have a long shel#li#e o# up to three

years

&efrigeration 3o temperatures ma$e microorganisms hich can

cause #ood spoilage to be inactive

+eat' #ish and #ruits

3rradiation Food is e"posed to ioni=ing radiation to destroy any

microorganism or insects that may be present in the

#ood. rradiation damages the D1o#

microorganisms and insects' preventing

proliferation. t also helps delay the ripening o#

#ruits' reducing spoilage during transportation.

Fruits

:ltraheat

treatment

+il$ is heated to an ultrahigh temperature o# 1!2oC

or higher #or 2 seconds. 1ll the microorganisms as/ell as their spores are illed.


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0) The effects of processed food on health

1. Food processing methods such as ultraheat treatment and canning can decrease the

nutritional valueo# #ood since vitamins and some other nutrients in the #ood are

destroyed by high temperature.

2. 8dditives used in #ood processing can be harmful to healthas shon by manylaboratory tests. Nitrates and nitrites that are used in bacon' ham and sausages have

been #ound to be carcinogenic.

!. ;ating too much o# #oods preserved in salt or sugar can lead to high blood pressure

and diabetes mellitus.

4. %*8 has been #ound to raise blood cholesterol level' leading to cardiovascular

diseases.t has also been #ound to produce tumors in rats.

,. -he coloring tartra=ine' used in so#t drin$s has been #ound to induce allergic

reactionssuch as asthma and rhinitis. /unset Iello' used in biscuits' has been #ound

to damage idneys and adrenal glandsin some animals.

6. Monosodium glutamatehas been associated ith headaches' asthma and chest pain.

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Form 4 Chapter 6 (b) Nutrition

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