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10.1.1.1
Molecules for life
Basic nutrients (elements and compounds) for life:
Introduction
Copyright © R. Botha (2011)
Introduction
• Living organisms consist of elements and
compounds that are part of the natural
elements of the earth.
• About 22 of the 92 natural elements are
essential for life.
• Plants and animals have basically the same
consistence although they differ considerably
from one another. They comprise of the same
compounds namely proteins, carbohydrates,
lipids and nucleic acids.
(Introduction)
Most living organisms are comprised of the
following elements:
• hydrogen (H): ± 60%,
• oxygen (O): ± 25%,
• carbon (C): ± 10%,
• nitrogen (N): ± 2%,
• sodium (Na) ± 0.7%, en
• very small quantities of sulphur (S),
phosphorus (P), magnesium (Mg), chlorine
(Cl), iron (Fe), etc.
What is the source of all the different
elements and compounds that living
organisms need?
Nutrients
• Nutrients are all the different material (organic and inorganic:
we will look at the meaning of these words a bit later) that is
essential to maintain the life of organisms.
• Animals do not make their own nutrients, but get their
nutrients from other sources (the food that they eat).
• Plants make their own organic nutrients and get their
inorganic nutrients from the soil by taking it up through their
roots.
• Chemical reactions are constantly taking place in living cells
and the chemical material participating in these reactions are
found in and around the cells.
• Nutrients are the source of these chemical material.
What do you think are the functions of
nutrients in the body?
Quickly discuss it with one another.
Functions of nutrients
Elements and compounds has the following functions as
nutrients in living cells:
• Some elements are building material (structural
components) for important organic molecules of which
the organism comprises.
• Certain compounds and elements are a source of energy
for the processes of life.
• The ions of some elements have an electrical charge that
influences the colloidal properties of the cytoplasm, eg.
the potential to take up water and other materials.
• Co-enzymes, in the form of single ions, have an influence
on the activity of enzymes, vitamins and hormones.
Classification of nutrients
Nutrients
Organic
• Carbohydrates
• Fats and Lipids
• Proteins
• Enzymes
• Vitamins
• Hormones
• Nucleic acids
Inorganic
Mineral elements
Macro elements
Micro elements
For all organisms:
K, Ca, Mg, P, S
For all organisms:
Fe, Mn, Zn, Cu, Co
For animals:
Na, Cl.
For animals:
I, Cr
For plants:
Mo, B, Cl, Na, Ni
Other
• Water
• Carbon dioxide
• Nitrogen containing
compounds
• Oxygen
Inorganic nutrients
• Inorganic material are traditionally seen as
material derived from mineral sources with no
biologic origin.
• We will look at the following inorganic
material:
– mineral elements
– water (H2O)
– carbon dioxide (CO2)
Inorganic nutrients:
Mineral elements
• The original meaning of minerals is material that
naturally occurs in the earth’s crust and is exploited by
mining.
• True minerals are crystalline solids.
• Nutrient mineral elements are those mineral elements
required by living organisms except the four elements
commonly found in all living organisms namely carbon
(C), hydrogen (H), nitrogen (N) en oxygen (O).
Macronutrient mineral elements
• Some mineral elements are required in large
quantities by living organisms (> 200 mg/day).
• These elements are called macronutrient
elements and are mainly required as building
material for compounds such as:
–
–
–
–
–
carbohydrates,
proteins,
nucleic acids,
hormones,
chlorophyll in plants, etc.
Micronutrient mineral elements
• Often only very small quantities of certain
mineral elements are required (< 200
mg/day).
• These mineral elements are called micro
mineral elements, or simply trace elements.
• Trace elements are used in molecules of
certain enzymes, vitamins and hormones.
Think about mineral uptake in plants and
animals.
What do you think is the mechanism of
uptake?
Mineral uptake
• Mineral uptake in plants is mainly via the roots
after which the mineral elements are
transported to the cells by the vascular tissue
of the plant.
• Animals get minerals from the food and fluids
that they eat and drink. The food is then
digested and broken down into simple
compounds and elements.
Biological importance of minerals
• The biological importance of mineral elements
includes the following:
– They are basic components of organic molecules.
– They have an influence on the colloidal state of
the cytoplasm.
– They have an influence on the activity of enzymes.
– They have an influence on the pH of the
protoplasm.
• Mineral deficiencies cause specific deficiency
symptoms in plants and animals.
Let’s look at the functions of minerals in
plants and animals and some of the
deficiency symptoms.
The information in the following tables is only
to let you know how important nutrition and
nutrients are. You do NOT have to remember
it for tests and exams!
Minerals: functions in plants and animals
Minerals
Functions and deficiency symptoms
Sodium
(Na+ ions)
Animals: Macroelement; one of the main cations in extracellular fluid;
essential for the co-regulation of ATP with potassium; serves as
conductor of electrical impulses in muscles and nerves. Deficiency
symptoms: cellular dehydration and abnormal blood pressure.
Plants: Trace element; serves as partial substitute for potassium. Bluegreen bacteria require sodium for normal growth and development.
Chlorine
(Cl– ions)
Animals: Macroelement; main anion in extracellular fluid; part of the
hydrochloric acid molecule in the digestive system of some animals
(including humans); electrical activity of cells controlled by Cl– ions
(cellular pump actions). Deficiency symptoms: Pleural inflammation
(pleurisy).
Plants: Trace element; necessary for the oxidation of H2O during
photosynthesis.
(Minerals: functions in plants and animals)
Minerals
Functions and deficiency symptoms
Magnesium
(Mg++
ions)
Animals: Macroelement; important in cell membrane stability, nerve
functions and muscle contractions and in the processing of ATP;
component of bones. Deficiency symptoms: abnormal hart rhythm and
tetany (intense, involuntary contraction of muscles).
Plants: Macroelement; necessary for carbohydrate metabolism and the
synthesis of chlorophyll; important component of the middle lamella of
cell walls and of certain co-enzymes. Deficiency symptoms: chlorosis
(yellowing of leaves).
Calsium
(Ca++ ions)
Animals: Macroelement; necessary for the control of cell membrane
stability, translocation of nerve impulses; muscle tone, healthy heart,
digestion and the clogging of blood; important component of the sceleton.
Deficiency symptoms: tetany and abnormal muscle cramps.
Plants: Macroelement; part of the pectin molecule and therefore
important for the middle lamella of cell walls; influences the selective
permeability of cell membranes and the hydration of protoplasm.
Deficiency symptoms: death of the growing tips. Calsium is absent in some
algae and fungi.
(Minerals: functions in plants and animals)
Minerals
Functions and deficiency symptoms
Potassium
(K+ ions)
Animals: Macroelement; main cation in extracellular fluid; systemic
electrolyte; essential for the co-regulation of ATP with sodium; coconductor of impulses in muscles and nerves. Deficiency symptoms:
muscle weakness and cramps; high blood pressure; arrhythmia; tetany.
Overdose: dehydration and kidney failure; arrhythmia; muscle weakness.
Plants: Macroelement; control osmotic potential of cells, selective
permeability of cell membranes and assimilation (uptake) of CO2 during
photosynthesis.
Iron
(Fe++ of
Fe+++ ions)
Animals: Macroelement; essential for proteins and enzymes; integral part
of the haemaglobin and cytochrome molecule which is essential for the
assimilation and transport of oxygen in the body. Deficiency symptoms:
anaemia.
Plants: Trace element; component of respiratory enzymes; present in the
stroma of the chloroplast; essential co-enzyme during the synthesis of
chlorophyll. Deficiency symptoms: chlorosis; short and thin twigs.
(Minerals: functions in plants and animals)
Minerals
Functions and deficiency symptoms
Nitrogen
(NO3 – ions
or NH4+
ions)
Animals: Macroelement; component of important molecules such as
amino acids and nucleic acids.
Plants: Macroelement; starting point of protein metabolism; component of
amino acids, nucleic acids, chlorophyll, etc. Deficiency symptoms: pale
green leaves; retarded growth. Overdose: dark green leaves; large number
of leaves; underdeveloped root system; inhibition of flowering.
Phosphorus
(PO43–
ions)
Animals and plants: Macroelement; component of nucleotides and nucleic
acids; part of the prosthetic groups of many enzymes; the phosphorus
bonds in many organic molecules are carriers of energy in respiratory
metabolism; essential component of cell membranes and bones;
functional in the regulation of the pH of body fluids in animals. Deficiency
symptoms in plants: stems and leaves turn red or purple.
(Minerals: functions in plants and animals)
Minerals
Functions and deficiency symptoms
Sulphur
(SO42–
ions)
Animals and plants: Macroelement; sulphur ions are essential for the
synthesis of certain important amino acids and proteins; sulphur is also a
component of vitamin B1 and biotin. Deficiency symptoms in plants: young
leaves are pale green.
Zinc
(Zn++ ions)
Animals and plants: Trace element; component of many enzymes involved
in cell metabolism.
Plants: Component of growth hormones and the co-enzymes involved in
photosynthesis. Deficiency symptoms: dots on stems; short nodes.
Iodine
(I– ions)
Animals: Trace element; part of the thyroxine molecule which controls
important metabolic cellular functions. Deficiency symptoms: enlarged
thyroid gland (goiter).
Manganese
(Mn++
ions)
Animals and plants: Trace element; necessary for nitrogen reduction; cofactor in the functioning of certain enzymes; co-enzyme in cellular
respiration reactions.
(Minerals: functions in plants and animals)
Minerals
Functions and deficiency symptoms
Borium
(B)
Plants: Some plants require borium as a trace element; influences the
development of meristematic tissue; plays an important role in the
development of the pollen tube and the translocation of sugar. Deficiency
symptoms: causes heart rot in sugar beet and other similar crops.
Molibdenium Trace element for some bacteria where it is essential for the fixation of
(Mo)
atmospheric nitrogen and the assimilation of nitrate and is a component of
several enzymes.
Cobalt
(Co++ ions)
A component of vitamin B12 and trace amounts are found in blue green
bacteria.
(Minerals: functions in plants and animals)
Minerals
Functions and deficiency symptoms
Copper
(C++ en
C+++
ions)
Animals and plants: Trace element; essential component of several redox
enzymes; a component of haemocyanis in some animals; an oxidation
catalyst for several mitochondric reactions in plants and animals; essential
for photosynthesis in plants. Deficiency symptoms in plants: wilting of
young leaves and a low crop yield.
Chromium
(Cr+++
ions)
Essential trace element for normal sugar and fat metabolism because
chromium enhances the activity of insulin; present in the entire body with
the highest concentrations in the liver, kidneys, spleen and bones.
Deficiency symptoms: anxiety; fatigue, glucose intolerance, insufficient
amino acid metabolism; higher risk for arteriosclerosis.
Certain other trace elements are required in plants. Their functions probably include coenzymes in metabolic reactions and integral components of certain enzymes. These
minerals include: aluminium, silicon, vanadium, fluorine and selenium.
Bemesting van plante
• Ons het in die vorige tabel gesien dat minerale
elemente verskeie funksies in plante het, en daarom
baie belangrike voedingstowwe is.
• Grond is dikwels arm aan minerale en boere en
tuiniers moet dan hierdie minerale aanvul deur
bemestingstowwe (kunsmis).
• Die bemesting van plante is baie kompleks en
daarom is dit nodig dat boere ‘n goeie kennis van die
samestelling van die grond asook die behoeftes van
die oesgewasse het wat hulle verbou.
Bemesting van plante: Stikstof (N) as voorbeeld
• In die vorige tabel het ons gesien dat stikstof
baie belangrik is vir plante, want dit is ‘n:
– ‘n Makro-element en die beginpunt van
proteïenmetabolisme;
– ‘n komponent van aminosure, nukleïensure,
chlorifl, ens.
• Molekulêre stikstof (N2) kan egter nie direk
deur plante opgeneem word nie. Die stikstof
moet dus in ‘n ander vorm aan plante
beskikbaar gestel word.
Bemesting van plante: Stikstof (N) as voorbeeld
• Ammonium (NH4+) en nitraat (NO3-) kan wel
deur plante opgeneem word en is beide goeie
bronne van stikstof vir plante.
• Kunsmis soos KAN (Kalksteen ammoniumnitraat) word dikwels gebruik om stikstof in
die grond aan te vul sodat plante beter groei.
• Ons het ook in die boonste tabel gesien dat
die tekortsimptome van stikstof vertraagde
groei en vergeling van blare (chlorose) by
plante is.
Bemesting van plante: Stikstof (N) as voorbeeld
• Kunsmis soos KAN word dus gebruik om
vertraagde groei en vergeling van blare te
behandel deur ‘n ekstra bron van stikstof aan
plante beskikbaar te stel.
Vergeling van blare
a.g.v. stikstortekort
Vertraagde groei by koring a.g.v. stikstoftekort
Bemesting van plante: Stikstof (N) as voorbeeld
• Die toediening van kunsmis het dikwels nadelige uitwerking vir die
omgewing.
• Oortollige kunsmis word weggewas (deur besproeiing en reën) en belang
sodoende in riviere, damme en mere.
• Te veel voedingstowwe in die water verooksaak die oormatige groei van
mikro-organismes (bakterieë en alge) in die water.
• Die oormatige groei van mikro-organismes verwyder suurstof uit die water
en skei baie koolstofdioksied in die water uit.
• Die waterdiere (visse, krappe, insekte, ens.) het dan te min suurstof om te
oorleef en vrek. Die oormatige koolstofdioksied is ook giftig vir die
waterdiere.
• Die totale ekostelsel in die riviere en damme word sodoende versteur.
• Hierdie verskynsel staan bekend as die verryking van water deur kunsmis,
of eutrofikasie.
Bemesting van plante: Stikstof (N) as voorbeeld
• ‘n Beter manier om stikstof (en enige ander
minerale voedingstof) aan plante toe te dien,
is dus deur natuurlikebemestingstowwe soos
kompos en beesmis.
• Die kompos en beesmis bevat ook baie
ammonial en nitraat asook ureum, aminosure
en nukleotiede, wat alles goeie bronne van
stikstof vir plante is.
Water, koolstofdioksied, suurstof en stikstof is
alles anorganiese verbindings en elemente
wat ‘n baie belangrike rol in lewe speel.
Kom ons kyk heel eerste na water.
Anorganiese voedingstowwe:
Water (H2O)
Water is die grootste komponent van lewende
organismes.
• Water is ‘n integrale deel en die grootste
komponent van alle vorms van lewe
• Water is die verspreidingsmedium van die
protoplasma.
• Water tree op as oplosmiddel vir en as
noodsaaklike reagens in metaboliese prosesse.
(Water)
• Water is sentraal in fotosintese en
selrespirasie.
• Water is sentraal in suur-basis neutraliteit en
ensiemreaksies.
• Water is ‘n hoofkomponent van die omgewing
van alle lewende organismes, veral akwatiese
organismes.
(Water)
Fisiese en chemiese eienskappe wat water geskik
maak om lewe te onderhou:
1. Water is ‘n kleurlose, geurlose, smaaklose
vloeistof met die allotropiese vorms van ys
(vaste stof) en stoom (gas).
2. Die watermolekuul is effens polêr wat maak dat
stowwe met ‘n lading (ione) in water kan oplos.
3. Waterstofbindings (kragte tussen
watermolekules) is verantwoordelik vir die
oppervlakspanning en kapillariteit van water.
(Water)
4. Water het ‘n hoë
–
–
–
kookpunt
smeltpunt
spesifieke hitte van verdamping.
5. Dit verskil van die meeste ander vloeistowwe in
dié opsig dat die soliede vorm nl. ys minder dig
is as die vloeistofvorm. Ys dryf dus op water.
6. Water is ‘n swak geleier van hitte.
7. Suiwer water is neutraal met ‘n pH van 7.
As ons die woord koolsuurgas of koolstofdioksied (CO2) hoor, dan sien ons ‘n klomp
uitroeptekens en dink ons net aan een dink:
AARDVERWARMING.
Tog is lewe nie moontlik sonder
koolstofdioksied nie. Hoekom?
Anorganiese voedingstowwe:
Koolstofdioksied (CO2)
• Koolstofdioksied maak ongeveer 0,03% van die
atmosfeer uit.
• Hoë konsentrasies koolstofdioksied in die atmosfeer is
toksies en selfs dodelik vir mense en die meeste diere.
• Koolstofdioksied is die belangrikste anorganiese bron
van koolstof en koolstof is die hoof boustof van
molekules vir lewe.
• Tydens fotosintese in groen plante word
koolstofdioksied gebruik om komplekse organiese
molekules soos koolhidrate, proteïene, lipiede,
nukleïensure, ens. te vorm.
(Koolstofdioksied)
• Hierdie organiese molekules is noodsaaklike
boublokke en bronne van energie vir alle
vorms van lewe.
• Tydens selrespirasie word hierdie komplekse
verbindings afgebreek en water en
koolstofdioksied word weer in die atmosfeer
vrygestel.
• Koolstofdioksied los maklik op in die klam
oppervlakke van plantselle en word dus maklik
deur plante direk uit die atmosfeer opgeneem.
Anorganiese voedingstowwe:
Suurstof (O2)
• Suurstof beslaan ongeveer 25% van die
atmosfeer.
• Die meeste lewende organismes benodig
suurstof tydens selrespirasie (aërobiese
respirasie) om bruikbare energie uit
voedingstowwe te verkry.
• Beide plante en diere verkry suurstof direk uit
die omgewing (atmosfeer of opgelos in water).
(Suurstof)
• Fotosinterende organismes (hoofsaaklik groen
plante en alge) stel in die daglig voortdurend
suurstof in die omgewing (atmosfeer of water)
vry deur fotosintese.
• Drie anorganiese verbindings wat suurstof
bevat nl. water (H2O), koolstofdioksied (CO2)
en molekulêre suurstof (O2) is deurentyd in
sirkulasie tussen die eksterne omgewing en
lewende organismes deur die prosesse van
fotosintese, respirasie en transpirasie.
Anorganiese voedingstowwe:
Stikstofbevattende verbindings
• Stikstofbevattende verbindings is basiese
boublokke in lewende organismes.
• Stikstof is 'n integrale deel van aminosure en
nukleïensure.
• Molekulêre stikstof in die atmosfeer kan nie
direk deur plante of diere gebruik word nie,
maar moet omgeskakel word in 'n ander vorm
of “gefikseer” word voordat dit gebruik kan
word.
(Stikstofbevattende verbindings)
• Reënwater besit dikwels groot hoeveelhede
ammonium (NH4+) en nitraat (NO3-) wat 'n gevolg is van
stikstofaksies deur weerlig.
• Rhizobium is ‘n bakterie wat simbioties in wortels van
sekere plante lewe en kan stikstof fikseer wat dan
beskikbaar is vir die plante.
• Herbivore (plantvreters) gebruik stikstofbevattende
aminosure uit plante as oorsprong van alle
stikstofhoudende verbindings en karnivore
(vleisvreters) kry hulle stikstof hoofsaaklik uit die
proteïene in die vleis wat hulle eet.
Organiese voedingstowwe
• Organiese verbindings is koolstofverbindings wat
koolstof en waterstof bevat maar bevat ook
dikwels suurstof, stikstof, ens.
• Die unieke eienskappe van koolstof (C) is
verantwoordelik vir die groot aantal en groot
variasie in organiese verbindings.
• Daar is meer as 3 miljoen organiese molekules
bekend en feitlik alle verbindings wat vanaf
lewende organismes verkry word, is organiese
verbindings.
Koolstof (C) vorm die basis van molekules in
alle organismes.
Kom ons kyk in van nader na hierdie
merkwaardige element.
Koolstof (C): Boustof van alle organiese
verbindings
• Koolstof het ‘n kovalente bindingsvermoë en
kan bind aan ander koolstofatome en niemetale soos waterstof, suurstof of stikstof.
• Hierdie bindings kan enkel, dubbel of trippel
wees.
• Koolstofatome wat bind kan ‘n lang ketting
vorm soos in vetsure, ‘n vertakte ketting soos
in aminosure, of ringe soos in purine van
nukleïensure.
Voorbeelde van verskillende vorms van
koolstofbindings
Ketting bv. propaan
Ring bv. adenien
Vertakte ketting bv.
isopentaan
Kombinasie van ‘n ring en ‘n ketting bv. ATP
Voorbeelde van organiese verbindings met enkel- dubbel- en trippelbindings
Enkelbinding bv. etaan
Dubbelbinding bv. etileen
Trippelbinding bv. asetileen
Belangrike chemiese eienskappe van koolstof vir
lewe
1. Koolstof is ‘n relatiewe klein atoom met ‘n lae
atoommmassa.
2. Koolstof het die vermoë om vier sterk, stabiele
kovalente bindings te vorm.
3. Dit het die vermoë om koolstof tot koolstof bindings
te vorm en kan dus lang "koolstofgeraamtes” met
ring- en/of kettingstrukture vorm.
4. Koolstof het die vermoë om veelvuldige kovalente
bindings met ander koolstof-, suurstof- en
stikstofatome te vorm.
(Belangrike chemiese eienskappe van koolstof vir lewe)
• Die bogenoemde eienskappe is verantwoordelik
vir die groot verskeidenheid van moontlike
organiese molekules.
• Variasie kom hoofsaaklik op die volgende
maniere voor:
– grootte, wat bepaal word deur die aantal
koolstofatome in die geraamte;
– chemie, wat bepaal word deur die elemente en
chemiese groepe wat aan die koolstof-atome geheg is,
en hoe versadig die koolstofgeraamte is;
– vorm, wat bepaal word deur geometrie wat ‘n gevolg
is van die hoeke tussen die bindings.