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 "prefabricated" 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).

Autotrophic NutritionAn 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 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

Chlorophyll

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:

Sun light CO2 + 2H2S (CH2O) + 2S +

H2O Bacteriochlorophyll

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ChemosynthesisOrganisms 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. .

Example: Nitrosomonas Bacteria :

2NH3 + 3O2 à 2HNO2 + 2H2O + Energy

Example: Nitrobacter Bacteria

2HNO2 + O2 à 2HNO3 + Tenaga

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PHOTOSYNTHESISAll 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.

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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 found.

Table 2.1: Main photosynthetic pigment, colours and where it can be found

Pigment types Colour Where it can be foundChlorophyll: Chlorophyll a

Chlorophyll b

Chlorophyll c

Chlorophyll d

Bacteriochlorophyll a-d

Carotenoid: Carotene Xanthophyll

yellow-green

Blue-green

Green

Green

Light blue

JinggaYellow

All photosynthisizing organism except bacteria

Higher plant and green algae

Brown algae and several unicellular algae

Several red algae

Photosynthesizing bacteria

All photosynthesizing organisms except bacteria

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Photosynthetic processPhotosynthetic 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

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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 diagram.

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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.

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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 manufactured.

Transportation of photosynthesis end product are through translocation process. Translocation process requires metabolic energy, which can be transported to all direction.

Carbohydrates has many uses such as :

a) As main energy source :In cellular respiration, for example in meristem tissues where glucose is used as energy source.

As energy storage :

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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

mesophyll tissues. 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 ATP.

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 photosynthesisd) Aquatic environment – for aquatic plant and algae

Oxygen source for animal are:a) Atmosphere – terrestrial animal

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b) Aquatic environment – aquatic animal

Udara sebagai sumber oksigen dan kebaikan udara sebagai sumber oksigen

Air as oxygen source and its advantages

Advantages of water as oxgen source

1. Atmospheric oxygen [O2] in air is higher than [O2] in water in the same volume. For terrestrial animal the amount of air volume 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.

1. No dehydration of respiratory surfaceRespiratory organ (gill) are exposed directly to the water.

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2. Viscousity and air densityAtmospheric air viscousity and density are lower than in water making it easier to pass through respiratory chamber. Therefore terrestrial animal use less energy to move air to its respiratory organ compares to its aquatic cousin.

2. Water provide bouyancyFor aquatic animal with gill, the water support the gill structure so that the whole gill structure in contact with water. For some aquatic plant, the air that trap in the body tissue provide support to the plant.

3. Rate of gas diffusionRate of gas diffusion are higher in the air compared to water. For example at 20ºC, oxygen diffuses 300,000 times faster in the air compared to water. Therefore oxygen is distributed more uniform in the atmosphere.

3. Oxygen is taken in pure form Oxygen diffused to gill surface in pure form not as in case of terrestrial animal.

4. Drop in oxygen level when temperature increaseAtmospheric oxygen only drop 8% when temperature raise from 0ºC to 24ºC. This minimal drop has no significant effect on terrestrial animal.

Disadvantage of water as oxygen source

5. Direct oxygen absorbtion from the atmosphere

Terrestrial animal absorb O2 driect from the atmosphere, not through medium or solvant as its aquatic

cousin.

1. Drop in oxygen concentration when temperature raise. [0] Concentration in salt water and freshwater will drop up to 40% when temperature raise from 0ºC to 24ºC. Dissolve oxygen in water will decrease as water temperature increase. During hot sunny day, especially in shallow water, the oxygen will drop to critical level which will kill aquatic animal.

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Disadvantages of air as oxygen source

2. Water viscousity and density are much higher

compared to air. Aquatic animal has to spend more energy to move water to the respiratory surface..

1. Drying of respiratory surface.In order to absorb oxygen from the air, the respiratory surface must be moist. Exposure to air can make respiratory surface dry, therefore animal must maintain moisture level of the respiratory tissue. Respiratory organ are enclosed within the body (lung).

3. Low diffusion rateThe rate of gas diffusion in water is lower than in the air. The oxygen concentration is higher on the surface water and progressively lower with increasing depth.

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)

GILL STRUCTUREBuccal 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.

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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

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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 adjacent cells.

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 SystemInsects 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.

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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. .

The Pathway 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 alveoli

Lung StructureThe posterior end of trachea branched out to form 2 bronchus. Bronchus branched repeatedly to form bronchiole. The internal surface of trachae, bronchus and bronchiole are cilliated. The bronchiole posterior is a sac known as alveolus. Alveolus is

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surrounded with fine blood capillary network and play an important role in gas exchange. The capillary and alveolus is lined with a compact layer of epthelial cell which allows oxygen to enter the blood stream and carbon dioxide expelled from the blood with ease.

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 as glucose.

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 metabolic reaction.

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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:

i) Glycolysisii) Formation of intermediate acetyl CoA compound iii) Crebb cycle/ Citric acid cycleiv) Hydrogen (electron) transport system

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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

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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

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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 water.

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

1. Glycolysisa) Glucosae F 1, 6 dip : 2ATP usedb) 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 cyclea) Citrate a - keto : 2NADH2 : 2 x 3 ATP = 6 ATP produced

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b) a - keto OAA : 4NADH2 : 4 x 3 ATP = 12 ATP producedc) 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

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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.

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3.7Mobilization of substrates for respiration

Carbohydrates

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

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

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oxidized through glycolysis process to generate energy. Fatty acid enters the krebs cycle and hydrogen transport system to produce even more energy!

Protein

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.

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