Chapter 5 - Life Processes - Nutrition

Chapter 5
Life Processes

Life Processes:- Life processes are the basic activities and functions that are essential for an organism to stay alive. These include processes like nutrition, respiration, transportation, excretion, growth, reproduction, and response to stimuli. All living organisms carry out these processes to maintain and sustain life.

 

Nutrition:- It is the process by which an organism obtains nutrients from food and utilizes them to obtain energy, for building and repairing its tissues.

Modes of Nutrition

1. Autotrophic nutrition

2. Heterotrophic nutrition

Autotrophic nutrition- The mode of nutrition in which organisms produces their food by themselves such as green plants, green algae, etc is known as autotrophic mode of nutrition.

Photosynthesis

The process by which green plants prepare their food by themselves with the help of carbon dioxide, sunlight and water in presence of chlorophyll known as photosynthesis.


 Reaction:

    
 

 


                                     Sunlight   
 

        Chlorophyll     6CO2 + 12H2O -----------------------à      C6H12O6          + 6H2O + 6O2

 

Site of Photosynthesis: Chloroplast is the site of photosynthesis.

Choloroplast : These are the disc shaped green coloured organelle present in the plant cells(mainly mesophyll cell). They contain a light absorbing green pigment, chlorophyll.

 Q. Draw a cross section of a leaf.


Opening and closing of Stomata

The stomata opens and closed due to the turgidity of water in guard cells. When water absorbs by guard cells, it swells that lead to opening of stomata and when loses water it shrinks, leading to closing of stomata.

Raw materials required for photosynthesis: Carbon dioxide, water and sunlight.

Events in photosynthesis process:

-         Absorption of light energy by chlorophyll.

-         Conversion of light energy to chemical energy and splitting of water into hydrogen and oxygen.

-         Reduction of carbon dioxide to carbohydrates.

 

Activity 5.1 – To Show That Chlorophyll is Necessary for Photosynthesis

Objective:

To prove that chlorophyll is essential for photosynthesis.

Materials Required:

  • A potted plant with variegated leaves (leaves with green and white patches, like a croton or money plant)
  • Alcohol (ethanol)
  • A beaker
  • Test tube
  • Bunsen burner
  • Iodine solution
  • Dropper
  • Water bath

Procedure:

1.     Take a healthy potted plant with variegated leaves.

2.     Keep it in a dark room for 2-3 days to de-starch the leaves (remove stored starch).

3.     Then place the plant in sunlight for 6–8 hours to allow photosynthesis.

4.     Pluck one variegated leaf from the plant.

5.     Boil the leaf in water for a few minutes to kill the cells.

6.     Then boil the leaf in alcohol using a water bath to remove chlorophyll (the leaf becomes pale or white).

7.     Rinse the leaf in warm water to soften it.

8.     Add a few drops of iodine solution on the leaf.

9.     Observe the color change.

Observation:

  • The green areas of the leaf (which had chlorophyll) turn blue-black after adding iodine.
  • The white (non-green) areas do not change color.

Conclusion:

  • Only the green parts of the leaf (which contain chlorophyll) can perform photosynthesis and produce starch.
  • Therefore, chlorophyll is necessary for photosynthesis.

Activity 5.4 – Experimental Setup

Objective:

To demonstrate that carbon dioxide is essential for photosynthesis.

Materials Required:

  • Two wide-mouthed transparent glass jars

  • Two healthy potted plants (same type and size)

  • Potassium hydroxide (KOH) solution

  • Watch glasses (2)

  • Split corks or thread for suspending leaves

  • Bell jars or airtight jars

  • Vaseline (for sealing)

  • Sunlight

Procedure:

  1. Take two healthy potted plants and keep them in a dark room for 2-3 days to de-starch the leaves.

  2. Place each plant inside a separate transparent airtight glass jar.

  3. In Jar A, place a watch glass containing potassium hydroxide (KOH). KOH absorbs carbon dioxide from the air inside the jar.

  4. In Jar B, place a watch glass containing plain water. This jar will act as the control setup.

  5. Ensure that the jars are properly sealed with Vaseline around the edges to make them airtight.

  6. Keep both jars in sunlight for 3–4 hours.

  7. After the exposure period, pluck a leaf from each jar and test it for the presence of starch using iodine solution (boil the leaf in alcohol to decolorize it, then rinse in warm water and test with iodine).

Observations:

Jar         Contents Observation on Leaf after Iodine Test
    A             Potassium hydroxide (absorbs                     CO₂) Leaf does not turn blue-black (no starch present)
                        B Plain water (CO₂ present) Leaf turns blue-black (starch present – photosynthesis occurred)

Conclusion:

  • Photosynthesis did not occur in Jar A because carbon dioxide was removed by potassium hydroxide.

  • Photosynthesis did occur in Jar B because carbon dioxide was available.

  • This shows that carbon dioxide is essential for photosynthesis.


2. Heterotrophic nutrition- The mode of nutrition in which organisms depend on other organisms for food is known as heterotrophic mode of nutrition. E.g – Human, animals, Insectivorous plants, etc.

Types :

-         Holozoic nutrition: The type of nutrition in which complex food molecules are taken in the form of solid or  liquid and broken down into simpler and soluble molecules called as holozoic nutrition. Eg – Amoeba, animals, human, etc.

It is divided into : Herbivores (plant eaters), Carnivores (meat eaters), and omnivores (both plant and meat eaters)

-         Saprotrophic nutrition: The type of nutrition in which organisms feed on dead and decayed organic matters is known as saprotrophic nutrition. Eg. – Fungi like bread moulds, mushroom, etc.

-         Parasitic nutrition: The type of nutrition in which organisms(parasites) lives either on or inside the body of other organism(host) to obtain their nutrition without killing them is known as parasitic nutrition. E.g- Leech, tapeworm, plants like cuscuta, etc.

Nutrition in Amoeba

Amoeba is a unicellular organism that obtains its food through a process called holozoic nutrition. This process involves the following steps:

  1. Ingestion:
    Amoeba captures food particles (like tiny plants or animals) using its finger-like projections called pseudopodia. The pseudopodia surround the food and form a food vacuole inside the cell.
  2. Digestion:
    Enzymes are secreted into the food vacuole, which break down the food into simpler, soluble substances.
  3. Absorption:
    The digested food is absorbed into the cytoplasm and used for energy, growth, and repair.
  4. Assimilation:
    The absorbed nutrients are used by the cell for its various life processes.
  5. Egestion:
    The undigested waste is moved to the surface of the cell and thrown out of the body.

 

Conclusion:

Amoeba shows a simple but efficient method of nutrition. It captures food, digests it, and removes waste—all within a single cell.

Q. Draw a diagram to show nutrition in Amoeba.

-          Nutrition in Human Beings

            The human digestive system comprises of alimentary canal and associated glands. Alimentary canal is the long tube extending from mouth to the anus. The glands associated with it are – Salivary glands, gastric glands, liver and pancreas.

Q. Draw the diagram of human digestive system.

 

Organ                                                                        Functions

-         Mouth (Buccal cavity) ---------------à    Take in the whole food

-         Teeth                               ---------------à    Chewing and grinding of food

-         Tongue                                  ---------------à          Tasting + rolling + Swallowing/pushing of the food

-         Salivary Gland                     ---------------à Located in and around the mouth, face, and neck secrete Saliva containing  salivary amylase. Salivary amylase convert Starch to sugar.

-         Oesophagus                         ---------------à Taking food from mouth to the stomach by peristaltic movement.

(Peristaltic movement: It is a wave of contraction behind the food and expansion in the region containing food that occurs in the alimentary canal.)

-         Stomach                                ---------------à Gastric glands secretes gastric juices.

Gastric juices are as follows:

 1. Pepsin :   Enzymes that breakdown protein

2. HCL :          Makes medium acidic, kill bacteria that enters stomach along with food and helps in breakdown of food into smaller molecules.

3. Mucus:     Protects the inner lining of the stomach.

 

-         Small intestine –

a) It releases intestinal enzymes that helps in breaking down complex food molecules into smaller, absorbable units i.e

Carbohydrate to Glucose

Fats to fatty acid and Glycerol

Proteins to Amino Acids

            b) It consists of finger like projections known as Villi which helps in absorption of food into the blood.

            c) It receives secretion from Liver and Pancreas

                        Liver – releases bile juice which helps in emulsification of fats.

                        Pancreas – It releases Amylase, Trypsin and Lipase enzymes.

                                    i. Amylase – It helps in breakdown of carbohydrate to sugar.

                                    ii. Trypsin – It convert proteins to peptones

                                    iii. Lipase – It converts fats to fatty acid and glycerol

Note :1. Small Intestine is the longest part of the alimentary canal. The length of the small intestine differs in all organisms depending upon their food habits e.g herbivores have longer small intestine to facilitate cellulose digestion but carnivores have shorter small intestine as meat is easily digestible.

            2. The inner lining of small intestine has numerous finger-like projections called Villi, which increases the surface area for absorption. The small intestine is the site of complete digestion of food.

-         Large Intestine : It absorbs excess water from the waste products.

-         Anus : Through it waste products removes out from the body


 

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