INTRODUCTION -:
Q. HOW DO LIVING ORGANISMS STAY ALIVE?
-> Life processes are the fundamental biological activities that are essential for the survival, growth, and reproduction of all living organisms. In simple words, all the activities that help an organism stay alive and keep its body working are called life processes.
FACT: When humans are inactive, such as sleeping, these life processes continue to occur in our body.
Q . WHY ARE LIFE PROCESSES NECESSARY?
-> Every living organism requires energy to perform daily life activities such as movement, growth, repair, reproduction and maintenance of body functions.
FOR EXAMPLE :
1) Plants need energy for photosynthesis and growth.
2) Animals need energy for movement and bodily functions.
-> Mainly, there are four types of life processes: Nutrition, Respiration, Transportation, and Excretion.
-> Nutrition is the process by which an organism obtains energy and raw materials from its environment for growth, repair, and maintenance.
-> The sources of food and energy in the environment can be very different. So, the body breaks down this food and converts it into a common form of energy that cells can use. This happens through many chemical reactions inside the body, especially oxidation-reduction reactions.
-> Many organisms use oxygen from the environment for this process. Taking in oxygen and using it to break down food to release energy is called respiration.
-> In single-celled organisms, there are no special organs for eating, breathing, or removing waste. This is because their entire surface is in direct contact with the environment, so everything happens through that surface.
-> But in multicellular organisms (like humans), different body parts do different jobs. Food and oxygen enter the body at specific places, but every cell needs them. So, the body needs a transport system (like blood circulation) to carry these substances everywhere.
-> When food is broken down using oxygen, it produces waste substances. These wastes can be harmful if they stay in the body, so they must be removed. The process of removing waste from the body is called excretion.
In this post, we will be mainly talking about Nutrition, its types and importance ;
:) NUTRITION:
-> Nutrition is the process by which an organism obtains energy and raw materials from its environment for growth, repair, and maintenance.
-> The mode of nutrition varies greatly across the living world.
(A) AUTOTROPHIC NUTRITION -
->Autotrophs ('self-feeders') synthesise their own organic food from simple inorganic substances. This is the foundation of all food chains, as autotrophs are the primary producers.
- Sub-types:
• Photosynthesis (Photoautotrophs): Use light energy to convert CO2
and H2O into glucose.
Examples: Green plants, algae, cyanobacteria.
• Chemosynthesis (Chemoautotrophs): Use energy from chemical reactions (oxidation of inorganic compounds) to fix carbon.
Examples: Nitrifying bacteria (Nitrosomonas, Nitrobacter), sulphur bacteria.
(B) HETEROTROPHIC NUTRITION -
-> Heterotrophs ('other-feeders') cannot synthesise their own food and depend on other organisms for organic nutrients.
-> This category includes animals, fungi, and most bacteria.
- Sub-types:
• Holozoic- Ingestion of solid food, internal digestion, absorption, assimilation.
Ex: Humans, Amoeba, most animals.
• Saprotrophic- Secretes digestive enzymes onto dead organic matter; absorbs the products.
Ex: Mushrooms, Rhizopus stolonifer (bread mold).
• Parasitic- Lives in/on a host organism, draws nutrition at the host's expense.
Ex: Tapeworm, Plasmodium, Cuscuta (total stem holoparasite).
• Symbiotic- Both organisms benefit from the nutritional relationship.
Ex: Lichens (algae + fungi), legume–Rhizobium (nitrogenous fixer).
# PHOTOSYNTHESIS - The Master Anabolic Reaction
-> Photosynthesis is the biochemical process by which chlorophyll-containing organisms use light energy to convert carbon dioxide and water into glucose and oxygen.
-> Photosynthetic organisms are major contributors to atmospheric oxygen and the entry point of energy into virtually all food webs.
* Overall Equation:-
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ ( in presence of light energy and chlorophyll).
(Carbon dioxide +Water → Glucose + Oxygen), (More scientifically, the oxygen released comes primarily from water, not CO₂.)
-> Site of Photosynthesis: The Chloroplast
• Outer & inner membrane: Envelope enclosing the chloroplast.
• Thylakoids: Flattened membrane sacs stacked into grana; site of the light-dependent reactions.
• Stroma: Fluid-filled matrix surrounding the thylakoids; site of the light-independent reactions (Calvin cycle).
• Pigments: Chlorophyll a (primary), Chlorophyll b, carotenoids (accessory) — absorb light at different wavelengths.
Stage 1 — Light-Dependent Reactions (Thylakoid Membrane)
• Chlorophyll absorbs light (mainly red ~680 nm and blue ~450 nm).
• Water molecules are split by photolysis: 2H₂O → 4H+ + 4e– + O2 (oxygen released as byproduct).
• Excited electrons pass through the electron transport chain (ETC).
• ATP is generated via photophosphorylation (chemiosmosis driven by proton gradient).
• NADP+ is reduced to NADPH — the key reducing agent for the next stage.
Stage 2 — Light-Independent Reactions / Calvin Cycle (Stroma)
• CO2 is fixed by Rubisco onto RuBP (ribulose-1,5-bisphosphate) — the carbon fixation step.
• The 3-carbon product (3-phosphoglycerate, 3-PGA) is reduced using ATP and NADPH.
• Glyceraldehyde-3-phosphate (G3P) is produced — the building block for the glucose and other organic molecules.
•“Three turns of the Calvin cycle fix three CO₂ molecules and produce one net molecule of G3P, while the remaining G3P is used to regenerate RuBP.”
NOTE: For formation of one glucose molecule, six CO₂ molecules are required, producing two net G3P molecules that can contribute to glucose formation.
* Human Digestion (Holozoic Nutrition)
-> Digestion is the breakdown of complex insoluble food molecules into small, soluble molecules that can be absorbed into the bloodstream and used by cells.
->It involves both mechanical (physical) and chemical digestion.
| Organ | Mechanical Action | Enzymes/Secretions | Products |
| Mouth | Chewing (mastication), tongue mixing | Salivary amylase (ptyalin) — digests starch | Maltose, smaller polysaccharides |
| esophagus | Peristalsis moves bolus to stomach | No enzymes; mucus secreted | Bolus transported |
| Stomach | Churning, mixing (chyme formation) | Pepsin (from pepsinogen), gastric lipase, mucus | Protein digestion and produces smaller peptides/peptones |
| Small Intestine (Duodenum) | Segmentation contractions | Pancreatic juice: trypsin, chymotrypsin, pancreatic amylase, lipase. Bile (from liver): emulsifies fats | Fatty acids and monoglycerides are absorbed and reassembled into triglycerides |
| Small Intestine (Ileum) | Peristalsis; villi increase surface area | Intestinal juice (succus entericus): maltase, lactase, sucrase, peptidases, enterokinase | Glucose, amino acids, fatty acids, glycerol |
| Large Intestine | Absorption of water, peristalsis | Gut bacteria; no major digestive enzymes | Water/electrolytes absorbed; faeces formed |
* Absorption:
-> Absorption occurs primarily in the small intestine. The inner surface is highly folded into villi and microvilli (brush border), massively increasing absorptive surface area. Glucose and amino acids are absorbed by active transport into capillaries; fatty acids and glycerol are reassembled into triglycerides and enter lacteals (lymph capillaries) as chylomicrons.
Nutrition is a fundamental life process that enables organisms to obtain, utilise, and transform nutrients into energy and essential biomolecules required for growth, repair, reproduction, and maintenance of life. Understanding the nutrition process not only helps us appreciate the complexity of biological systems but also highlights the importance of maintaining a balanced diet for overall health and well-being.
really amazing
ReplyDeleteThank you for motivating me always .
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