Nutrition an introduction
Study of the materials that nourish an organism and of the manner in which the
separate components are used for maintenance, repair, growth, and reproduction.
Nutrition is achieved in various ways by different forms of life. Plants that contain
the green pigment chlorophyll can synthesize their food from inorganic
substances in the process called photosynthesis. Organisms such as plants that
can thus manufacture complex organic compounds from simple inorganic
nutrients are termed autotrophic. Organisms that must obtain quot;prefabricatedquot;
organic compounds from their environment are heterotrophic, and these include
the fungi, some other plants, and animals. Heterotrophic plants may be
saprophytic (obtaining nutrients from dead organisms) or parasitic (obtaining
nutrients from living organisms while living on or in them). Heterotrophic animals
may be parasites, herbivores (plant eaters), carnivores (meat eaters), or
omnivores (obtaining nutrition from both plants and animals).
An organism that is able to synthesize its own food is known as autotroph.
Therefore autotroph refers to organisms that are able to synthesize organic
substances from simple organic materials. There are two form of autotroph:
photosynthesis (as in plant and algae) and chemosynthesis (as in bacteria)
Photosynthesis is a process in which organisms (plant and algae) trap/harvest
light energy (in form of sunlight) to form high energy organic compounds from
inorganic substances of low energy value (CO2, minerals (N,P,K) , and water).
Chlorophyll or other light harvesting pigment (bacterio chlorophyll, other acessory
pigments) captured Sun’s energy. In green plant, algae and bacteria the
photosynthetic equation are as follows:
CO2 + H2O Sunlight (CH2O)n + O2
Water is required during photosynthesis and act as hydrogen donor (electron)
Green sulphur bacteria used hydrogen sulphide or other reduced sulphur
compound as hydrogen donor (instead of water) and its pigment is known as
bacteriochlorophyll. Its structure is similar to chlorophyll but much simpler.
Photosynthetic equation for green sulphur bacteria is as follows:
CO2 + 2H2S (CH2O) + 2S +
Organisms that carried out chemosynthesis also used CO2 and H2O while the
energy is obtained from chemical reaction instead of the sun’s energy. Energy is
obtained from oxidation of inorganic element or compounds such as hydrogen,
H2S, Sulphur, Ferrum (II), ammonia and nitrate.
2NH3 + 3O2 à 2HNO2 + 2H2O + Energy
2HNO2 + O2 à 2HNO3 +
All living organisms in this world directly or indirectly depends on photosynthesis.
Photosynthesis manufacture organic carbon and give energy in living organism
and release O2 to the atmosphere, which is crucial to aerobic organism. Human
also relies on photosynthesis for fossil fuel (wood, coal and petroleum product).
The place where photosynthesis takes place plant is chloroplast. Please refer to
the following illustration. If we take a look at leaf cross section, just underneath the
leaf surface (the shiny waxy part) is where the photosynthetic cells situatated. A
closer look at each photosynthetic cell, it contains several chloroplasts. The
number of chloroplast varies from few (if the leave is exposed to strong sunlight)
to many (is the leave is under shady place). If we look further into each
chloroplast we can see that it is actually consist of stacked thylakoid membrane
system (granum) and stroma. Thylakoid contains photosynthetic pigments,
enzymes and electron transport system whereas stroma contain soluable
enzymes and other chemicals such as sugar and organic acid.
In higher plant, there are two types of pigment that is Chlorophyll and carotenoid.
Table 2.1 lists the main photosynthetic pigments, its colour and where it can be
Table 2.1: Main photosynthetic pigment, colours and where it can be found
Pigment types Colour Where it can be found
Chlorophyll a yellow-green All photosynthisizing organism
Chlorophyll b Blue-green
Higher plant and green algae
Chlorophyll c Green
Brown algae and several
Chlorophyll d Green unicellular algae
Bacteriochlorophyll a-d Light blue Several red algae
Carotenoid: Photosynthesizing bacteria
All photosynthesizing organisms
Photosynthetic process ia a complicated process which involved two separate but
complimentary reaction that are light dependent reaction (photochemical reaction)
and enzymematic reaction (light independent reaction).
Photochemical reaction occurs inside thylakoid membrane. This reaction
involved the photoactivation of chlorophyll. When the light energy is absorb by the
chlorophyll, electron is excited and is released from the chlorophyll
light energy à Chlorophyll + + high energy electron.
Chlorophyll a can be divided into dual photosynthesis systems that is photosystem
I (PSI or P700) and photosystem II (PSII or P680). Please refer the following
Energy that is trap in electron will be used to synthesis ATP and NADPH2.
Light independent reaction or enzymatic reaction is also known as Calvin cycle or
C3 cycle which occurs inside stroma. This reaction used the energy from ATP and
the reducing power of NADPH2 (produced during photoactive reaction) to reduce
CO2. All the reaction in stroma is controlled by enzyme.
End product of Calvin Cycle is PGAL (phosphor-glyceraldhyde). PGAL later
turned into other organic compound. Usually the end product of photosynthesis is
turned into organic compound that is easy to transport such as glucose, sucrose,
amino acid, fatty acid and glycerol. From these simple organic compounds more
complex organic compound such as protein, carbohydrate and lipid can be
Transportation of photosynthesis end product are through translocation process.
Translocation process requires metabolic energy, which can be transported to all
Carbohydrates has many uses such as :
As main energy source:
In cellular respiration, for example in meristem tissues where glucose is used
as energy source.
As energy storage :
Carbohydrates are stored in stem (Sago tree), in fruits (papaya) and in roots
(sweet potato). Stored food is in this form as it is not water soluable.
b) As building materials::
Carhohydrates also can be converted into more complex materials such as
polysaccharide compound (cellulose and lignin) to provide durable structure
and new tissues especially in places where new cells develop.
Structure associated to Photosynthesis
Leave is the most important organ in photosynthetic processes. Leave shape and
structure varies according to plant species, where it grows and the surrounding
environment. These is a forms of adaptation to optimize photosynthesis.
1.) Flat and broad leave provide bigger surface area for capturing light energy.
2) Thin leave reduce the light penetration to mesophyll tissues and reduce the
diffusion distance for CO2 from the atmosphere to mesophyll tissues.
3.) The transparency of the epidermis layer facilitates the light to reach the
4.) The location of chloroplast in the mesophyll tissues can change depending on
the amount of light receive to ensure optimum light absorption.
5.) The spongy mesophyll is loosely arrange to facilitate CO2 gas to enter the
cavity and to increase the surface area for absorption of CO2 into the tissues.
6.) The underneath layer of leave contain stomata which is the entry point for CO2
to come in and water vapour to come out.
7.) Leave veins on the leave contains schelerenchyma and collenchyma. This
structure give reinforcement to the leave and to ensure the leave at at
perpendicular angle to receive maximum light.
8.) Xylem in the leave vein transport water and mineral salts while phloem
transport photosynthetic by product to other places that require it.
RESPIRATION IN PLANT AND ANIMAL
Respiration refers to processes where animal or plant cells take and use oxygen,
produce and emit CO2 and convert energy to biologically useful form such as
Main differences between respiration and breathing is breathing is the act of
taking air into the respiratory organ (lung) and expelling air from the lung).
Oxygen source for cellular respiration
Oxygen source for plant are:
a) Atmosphere – oxygen entering the plant through stomata underneath the
leaves or lenticell in stem.
b) Soil- oxygen entering plant through root system
c) Photosynthetic process – plant producing oxygen through photosynthesis
d) Aquatic environment – for aquatic plant and algae
Oxygen source for animal are:
a) Atmosphere – terrestrial animal
b) Aquatic environment – aquatic animal
Udara sebagai sumber oksigen dan kebaikan udara sebagai sumber oksigen
Air as oxygen source and its Advantages of water as oxgen
1. Atmospheric oxygen 1. No dehydration of respiratory
[O2] in air is higher than [O2] in water surface
in the same volume. For terrestrial Respiratory organ (gill) are exposed
animal the amount of air volume directly to the water.
needed to pass through the respiratory .
organ are less compared to the aquatic
animal. The higher [O2] in the
atmosphere enable terrestrial animal to
have higher metabolic rate compared to
the aquatic animal.
2. Viscousity and air density 2. Water provide bouyancy
Atmospheric air viscousity and density For aquatic animal with gill, the water
are lower than in water making it easier support the gill structure so that the
to pass through respiratory chamber. whole gill structure in contact with
Therefore terrestrial animal use less water. For some aquatic plant, the air
energy to move air to its respiratory that trap in the body tissue provide
organ compares to its aquatic cousin. support to the plant.
3. Rate of gas diffusion 3. Oxygen is taken in pure form
Rate of gas diffusion are higher in the Oxygen diffused to gill surface in pure
air compared to water. For example at form not as in case of terrestrial animal.
20ºC, oxygen diffuses 300,000 times
faster in the air compared to water.
Therefore oxygen is distributed more
uniform in the atmosphere.
4. Drop in oxygen level when Disadvantage of water as oxygen
temperature increase source
Atmospheric oxygen only drop 8%
when temperature raise from 0ºC to
24ºC. This minimal drop has no
significant effect on terrestrial animal.
1. Drop in oxygen concentration
when temperature raise.
 Concentration in salt water and
5. Direct oxygen absorbtion from the freshwater will drop up to 40% when
atmosphere temperature raise from 0ºC to 24ºC.
Terrestrial animal absorb O2 driect from Dissolve oxygen in water will
the atmosphere, not through medium or decrease as water temperature
solvant as its aquatic cousin. increase. During hot sunny day,
especially in shallow water, the
oxygen will drop to critical level
which will kill aquatic animal.
2. Water viscousity and density are
Disadvantages of air as oxygen compared to air.
source Aquatic animal has to spend more
energy to move water to the respiratory
1. Drying of respiratory surface. 3. Low diffusion rate
In order to absorb oxygen from the air, The rate of gas diffusion in water is
the respiratory surface must be moist. lower than in the air. The oxygen
Exposure to air can make respiratory concentration is higher on the surface
surface dry, therefore animal must water and progressively lower with
maintain moisture level of the increasing depth.
respiratory tissue. Respiratory organ
are enclosed within the body (lung).
2. Oxygen in the air is not pure.
In term of abundance, air contain 78%
nitrogen gas, followed by oxygen about
21%, CO2, and other gas.
BONY FISH RESPIRATORY SYSTEM (THE GILL)
Buccal chamber of teleost fish connect to the aquatic surrounding through mouth
and gill opening. Gills are protected by the operculum. There are 4 gill arches that
support gill filament and and blood vessel. The anterior gill arch are equiped with
gill rakers to filter debris and protect the delicate gill filaments at the posterior end.
The gill filaments is the structure where oxygen is absorb from the water. To
increase the surface area of breathing structure and increase oxygen absorption
efficiency, each gill filament has gill lamella. This gill lamella is a thin layer of
epithelial cells, which is rich in blood capillaries to absorb, dissolve oxygen.
Blood are supplied to the gill arch through afferent artery (carrying deoxygenated
blood). The artery than branch out, pass through gill filament and gill lamella. The
oxygen than enter the blood capillary and the oxygenated blood is distributed
throughout the fish body through efferent arterial system.
INSECT RESPIRATORY SYSTEM
Insect thorax and abdomen have lateral pores on both side. This pore is called
spiracle which allows air from outside to enter the trachial tube system. Spiracle is
equiped with valve or tiny hairs to prevent excessive evaporation. Tracheal tube is
reinforced with chitin.
Gas diffuse into the tissue inside the thin walled trachial tube network known as
trachiol. Trachiol has numerous tiny end which connect into the cell or in
between cells. Trachiols are permeable to liquid and gas. The end of the trachiol
is immersed with cellular liquid where the absorb oxygen is passed on to the
A unique feature of insect respiratory system is it does not require blood as in
other animals. Oxygen is directly supplied to the tissues through a network of air
tube. In most insects, diffusion is the main means of oxygen supply. In certain
aquatic insects, part of the trachial system has air sac, which also serve as
bounyancy and body balance.
The importance of Trachial System
Insects tracheal system is advantageous in that O2 and CO2 can diffuse 10,000
times faster in the air dan absorption in the water and blood. This is one of the
reason why insects is very successful.
HUMAN RESPIRATOTY SYSTEM
Structures in human respiratory system includes nose, pharynx, larynx, trachaea
and lung in thorax. Intercoastal muscle and diaphragm are responsible for the
respiratory movement. .
Air enters the nostrils where it is heated up and moisten while dusts are
filtered out by nasal hairs and nasal mucous
The air than passes through the nasopharynx,
the oral pharynx
through the glottis
into the trachea which is coveren with mucous layer and cillia and enter
into the right and left bronchi, which branches and rebranches into
bronchioles, each of which terminates in a cluster of
out to form
role in gas
lined with a
Once the oxygen is in the cells by various system (gill, spiracle, lung), cellular
respiration can take place to generate energy.
AEROBIC CELLULAR RESPIRATION
Aerobic cellular respiration is a process where oxygen is used in chemical
reaction in living cell, which release energy from stored organic compound such
Energy that is stored in food is too big for the cell is it is all release at once.
Because of that the organic compound are oxidised by stages in a series of
chemical reaction. Each stage will release enough energy to continue the
When the food (organic compound) is broben down, some of the energy liberated
is stored in form of adenosin triphosphate (ATP). The last bond between two-
phosphate molecules is the high-energy bond. The last phosphate molecules can
be released immediately, thus releasing the energy from the chemical bond and
producing adenosin diphosphate (ADP). Adenosin diphosphate imediately
combine with another phosphate molecule to form another ATP. This process
(formation of high energy bond between phosphate molecules) requires energy,
which is supplied by the oxidation of food. Energy released from the oxidation of
food is stored in form of high-energy bond.
ATP is small and easily soluable molecules. It will diffuse from where it is
produced to where it is needed, for example muscle tissue for movement, to
membrane for active transport and to ribosome for protein synthesis.
Cellular aerobic transport consist of four stages:
ii) Formation of intermediate acetyl CoA compound
iii) Crebb cycle/ Citric acid cycle
iv) Hydrogen (electron) transport system
Step 1. Glycolysis
Glycolysis occur inside the cell (in cytoplasma), outside mitochondrion and does
not require oxygen. (Six carbon sugar – hexose) is broken down to two pyruvic
acids molecule (3 carbon sugar).
Step 2. Formation of intermediate acetyl-CoA compound
This reaction occurs inside mitochondrion. Pyruvic acid enter mitochondrion and
activated by coenzyme A to form acetyl CoA (2C compound).
Step 3. Krebs Cycle (Citric acid cycle)
The fuel consumed in the krebs cycle is a 2-carbon compound called lactic acid
which is bonded to carrier molecule called coenzyme A. The krebs cycle finishes
extracting the molecules of sugar by breaking the acetic acid molecules ( two per
glucose) all the way down to CO2. The cycle uses some of this energy to make
ATP by the direct method. Krebs cycle also captures much more energy in the
form of NADH and a second electron carrier, FADH2. Electron transport then
converts NADG and FADH2 energy to ATP energy.
3.5.4 Hydrogen (electron) Transport System
Hydrogen acceptor takes hydrogen atom removed during hydrogenation,
than reduced. Hydrogen atom than taken by the second acceptor, which is
also reduced while the first acceptor is oxidized again. During the transfer
enough energy is liberated to synthesis ATP. Oxidation-reduction
processes are repeated until hydrogen atom combined qith oxygen to form
The two primary acceptor are nucleotide, NAD and FAD. The third acceptor
is cytochrome while thr fourth acceptor is cytochrome oxidase. Cytochrome
oxidase release the hydrogen to oxygen to form water.
Everytime hydrogen atom is transported from NAD to oxygen, three ATP
molecules is produced, however if hydrogen is transported via FAD only
two ATP molecule is produced.
ATP formation process through hydrogen transport system occurred inside
the mitochondria also known as oxidative phosphorylation
Amount of ATP produced during aerobe respiration
a) Glucosae F 1, 6 dip : 2ATP used
b) PGAL Pyruvate : 2 x 2 ATP = 4 ATP produced
: 2NADH2 : 2 x 3 ATP = 6 ATP produced
II Pyruvate Acetyl CoA : 2NADH2 : 2 x 3 ATP = 6 ATP produced
III Krebs cycle
a) Citrate a - keto : 2NADH2 : 2 x 3 ATP = 6 ATP produced
b) a - keto OAA : 4NADH2 : 4 x 3 ATP = 12 ATP produced
c) OAA Citrate: 2FADH2 : 2 x 2 ATP = 4 ATP produced
: 2 x 1ATP = 2 ATP produced
NET ATP PRODUCED DURING CELLULAR
RESPIRATION = 40 – 2 = 38 ATP (36ATP)
Full energy content for one glucose molecule is approximately 2830 kj.
Energy content for one ATP molecule is approximately 34 kj. Therefore
energy liberated from one glucose molecule through aerobe respiration is
34 x 38 kj or 1292 kj. Aerobic respiration efficiency is approximately
(1292/2830)x 100 =45.6%
3.6 Anaerobe respiration
Anaerobe respiration occurred in absent of oxygen. In anaerobe
respiration, most of the energy source comes from hydrogen transport
system. For hydrogen transfer to take place, oxygen is required to accept
hydrogen atom from the last part of the hydrogen transport system
In anaerobe respiration, NAD takes hydrogen atom produced from
glycolysis. However in absent of oxygen, pyruvate becomes the last
hydrogen acceptor where it takes hydrogen atom received by NAD.
Pyruvate is not converted to carbon dioxide and water and water but
converted to ethanol or lactic acid.
Ethanol is the product of anaerobe respiration for plant and lactic acid is
the product produced in animal. Anaerobe bacteria produced either ethanol
or lactic acid depending on species.
Since the breakdown of sugar is incomplete, less energy is produced.
Energy is still stored in ethanol or lactic acid. IN animal, this energy can still
be liberated by converting lactic acid to pyruvate and then oxidized through
krebs cycle in the presence of oxygen. Ethanol cannot be converted to
carbohydrate or breakdown further even in the presence of oxygen,
therefore it becomes toxic to plant. That is the reason why plant can only
undergoes anaerobic respiration for short duration. Respiration should
revert to aerobic respiration to enable plant to survive.
Only two ATP molecules were liberated during anaerobic respiration
compared to 38 in aerobic respiration.
3.7 Mobilization of substrates for respiration
Carbohydrate is the main substrate for respiration. Usual carbohydrate in nutrition
are starch, lactose and sucrose. Starch and other big molecule carbohydrate are
hydrolyzed into smaller molecules until monosaccharides is formed. All
carbohydrates that reached the cells are in form of glucose. Inside the cell,
glucose is oxidized to supply most of the energy requirement.
Lipid can be used as an alternative to carbohydrate for respiration. Lipid is stored I
liver. Lipase enzyme breaks down lipid into fatty acid and glycerol. Glycerol is
oxidized through glycolysis process to generate energy. Fatty acid enters the
krebs cycle and hydrogen transport system to produce even more energy!
Protein is also used as substrate especially in carnivorous animal and those
where the main diet consist of protein. Protein eaten is converted into amino acid.
Each amino acid groups is deaminated where amino group is removed to form
ammonia, urea and uric acid and then excreted. Carbon compound left behind
that is keto acid enter the main respiration pathway either glicolysis, pyruvic acid
or krebs cycle.