hetertotrophic nutrition

Heterotrophic nutrition

Heterotrophic (Gk. Hetero=different; trophe= nourishment) nutrition: this kind of nutrition is followed by all animals , fungi, some prosists, bacteria and nn green plants. These organisms obtain their food from other plants and animals beacuse they have no chlorophyll to trap solar energy and make their own food. Animals showing heterotrophic nutrition are called heterotrophs.

On the basis of nature of food heterotrophic nutrion is of three types:

1.     saprophytic nutrition

2.     parasitic nutrition

3.     holozoic nutrition

saprophytic nutrition is the mode of nutrition in which heterotrophs get their food from dead and decaying organisms

Saprophytic organisms produce digestive enzyme, these enzyme when released on the food material they breaks down to soluble food . this food in soluble form is absorbed. This method leads to the decay and decomposition of organic food material.

 Saprophytes are mainly bacteria and fungi. Yeast, mushrooms and moulds are saprophytic fungi.yeast feed on sugar solution which helps in its growth. Neottia and monotropa are flowering plants which are saprophyte.

Parasitic mode of nutrition is the phenomenon in which an organism(parasite) lives in or on the body of another organism(host). Parasite absorb the food from the body of their host, in thos process they make damage or even kill their host organism. This phenomenom is called parasitism. This mode of nutrition is showed by non-chlorophyllous plant, viruses and some fungi.

In fungi, mycelium go deep in the host tissue and secrete enzyme. The soli food in host body is converted in soluble form and then absorbed abd assimilated by fungal hyphae. For this purpose, tips of hyphae gets rounded and are called haustoria. Some parasitic bacteria cause diseases in plants and animals, these are pathogens.

Total stem parasite: cuscuta

Partial stem parasite: viscum, loranthus

e.g., puccinia (wheat and barberry plant), roundworms,

ectoparasite e.g., bedbug, head louse,

endoparasite e.g., trypanosome, malarial parasite(intracellular parasite)

taenia, ascaris (coelozoic parasite)or blood fluke, filarial worm (histozoic in body tissue)

green species of euglena, e.g., E.viridis, E.gracilis (autotrophic in light but saprophytic in dark). This dual mode is called myxotrophic nutrition.

Holozoic nutrition is the mode in which digestion is always inside the body, either intercellularly or intracellularly.  Organisms can feed on solid food material. The food may be whole plant animal or their part

Photosynthesis : mechanism

Photosynthesis : mechanism

The process of photosynthesis is divided in two phases:

Dark phase (photochemical reaction)

Light phase (chemical reaction)

Light phase: this reaction phase require light therefore also called photochemical reaction.

First the light energy is absorbed by chlorophyll. This takes place in the grana region. The chlorophyll a pigment traps the visible light in form of quanta or photons (energy). When the chlorophyll molecules are exposed to light they gets exited and emits electrons. Photons are the energy packets emitted by light. This energy is inversely proportional to its wavelength, shorter the wavelength of light higher is the energy of photon.

Light energy is converted into chemical energy and splits water molecule into hydrogen and oxygen. emitted electrons are channelled through electron transport chain in chloroplast. The photons absorbed by chlorophyll  then carries out three function:

i.                    Formation of ATP (Adenosine triphosphate) . ATP is the source of energy used during the during the dark phase of photosynthesis. ATP is formed when ADP (Adenosine diphosphate)  joins a phosphate group.

ADT + Phosphate Gr ----------à ATP

ii.                  Photolysis of water. Decomposition of water with the help of light energy  into hydrogen and oxygen is called photolysis of water

Water + energy -------à Hydrogen + oxygen

This oxygen is by product of photo synthesis.

iii.                Synthesis of NADPH (reduced nicotinamide adenine dinucleotide phosphate). Hydrogen ions released from water  joins with NADP and reduces it to NAPH. This is also used in dark reaction.

Dark phase: this is the light independent phase. It does not need light energy and thus it is completely chemical process. This reaction takes place in stroma region of chloroplast

Carbon-dioxide is reduced to carbohydrate. Carbon dioxide is reduced to glucose by hydrogen in NADPH and energy in ATP. This reaction is also called clavin cycle. Melvin clavin explained this process using radioactive carbon.

ATP and NADPH molecules together are called as assimilatory power.

RuBP  + CO₂  + NADPH  + ATP  ------à   RuBP  +  C₆H₁₂O₆    +  ADP  +  NADP  + Po₄

RuBP : ribulose biphosphate enzyme

RuBP combines with  CO₂ to make carbohydrate and regenerating RuBP.

Diagrammatic representation of photosynthesis mechanism.

  

Significance of photosynthesis

1.     Food . food is synthesized from raw material like carbon-dioxide and water.

2.     Oxygen . oxygen required for respiration and combustion processes are formed as a  by-product of photosynthesis.

3.     Fuels. Fossil fuel lie coal, oil natural gas are forms of stored solar energy synthesized by photosynthesis.

PHOTO-AUTOTROPHIC MODE OF NUTRITION

PHOTO-AUTOTROPHIC MODE OF NUTRITION

Photo-autotropic mode of nutrition or photosynthesis  is the process by which photoautotrophs synthesize food in the presence of sunlight, CO₂ and H₂O. by this method solar energy is trapped by autotrophic organism and converted into food. In this process carbohydrates are synthesized from simple inorganic compounds like carbon dioxide and water in presence of chlorophyll and sunlight.

In plants the unused carbohydrates are stored in form of starch.

In animals unused food is stored in form of glycogen.

Chloroplast

Chloroplasts(G.k  chloros- grass green   plastos-moulded) are the green plastids which help in the synthesis of organic food. These are uniformly distributed in cytoplasm of plant cell.  Chloroplast is found in the upper surface of leaf, thus exposing it to maximum sunlight so that more solar enery is absorbed.

It is covered by a double membranous structure called chloroplast envelope where each membranous structure is a unit of plasma membrane like structure. This membrane can be observed by electron microscope.

Protein matrix present in chloroplast is called matrix or stroma.

Lamellae or thylakoids are a membrane system which run parallel to each other in stroma. There are two types of thyllakoids present in higher plants. Large thylakoid (stroma thylakoid)  extend from one end to other end of chloroplast , small thylakoid (grana thylakoid) are disk shaped and closely placed to each other to form grana. Grana and stroma thylakoid fuse with each other in the region of granum

Photosynthetic pigments

These are the pigments involved in photosynthesis. e.g.  chlorophyll, carotenoid (carotenes and xanthophylls) , anthocyanin, phycobilins (phycocyanin and phycoerythrin)

Chlorophylls are green pigment present in chloroplast and gives green color to plants. These are of seven types . chlorophyll a, b, c, d, e, bacteriochlorophyll and bacterioviridin. These traps solar energy and converts it into chemical energy during photosynthesis.

Carotenoids are lipid and are classified in two groups: carotenes which are orange red in color. Xanthophylls are yellow in color.

Carotenoid absorb light energy and transfer it to chlorophyll a and act as accessory pigment.

Site of photosynthesis

Photosynthesis takes place in chloroplast which contain the pigment chlorophyll. These pigments are therefore available in the green part of plants like leaves , green stem.

Carbon dioxide diffuses in the leaf through stomata present in lower surface of leaf. Chloroplast which is present in the upper surface of leaf captures more sunlight.  Leaf vein brings the water .

Raw material needed during phtotosynthesis

1.     Carbon dioxide – forms 0.32 % of total atmosphere. Provides carbon for carbohydrate formation. Hydrophytic plant use CO₂ dissolved in water

2.     Water – provides hydrogen for carbohydrate foemation. Helps in keeping stomata pores open. Deficiency of water  can cause closing of stomata thus checking CO₂  to enter the leaf.

Solar Energy is trapped in chloroplast and converted into chemical energy. This chemical energy is ATP ( adenosine triphosphate).

Carbohydrate synthesis during photosynthesis

6CO₂ + 6H₂O   ---^{light+chlorophyll}----à C₆H₁₂O₆ + 6O₂

Photosynthesis is the process where light energy is converted in chemical energy. Solar energy is captured by chlorophyll in presence of carbon-dioxide and oxygen and carbohydrate (food) and oxygen are formed. this biochemical  activity of plant uses solar energy to make their food, this carbohydrate undergoes respiration to release energy to be used in various metabolic activities.

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