Living things carry out life processes like nutrition, which can occur through autotrophic or heterotrophic means. Autotrophs like plants perform photosynthesis, using chlorophyll, carbon dioxide, water and sunlight to produce their own food in the form of carbohydrates. Heterotrophs obtain nutrition from other organisms and include animals, fungi and saprophytes. Experiments showed only the green parts of variegated leaves produced starch from photosynthesis, and that carbon dioxide is required for photosynthesis to take place. The human digestive system breaks down starch using salivary amylase in the mouth.

1. Life Processes
By Neha R Class 10th

2. Introduction
Living beings are the organisms which show all the characteristics of life i.e.
growth, movement, reproduction, respiration etc.

4. Nutrition refers to all activities included in obtaining the food and its
utilization in the body. Food when taken and digested in the body provides
energy for life activities ,materials for growth and reproduction, resistance
from disease or regulation of body processes. Materials which provide
nutrition to organism are called nutrients carbohydrates, proteins and fats are
the main nutrients.

5. Modes of nutrition

6. Autotrophic nutrition : It is a kind of nutrition in which organism prepares its own food.
E.g. Green plants and some bacteria.
It is the process by which autotrophs take in substances from the outside and convert
them into stored form of energy. This material is taken in the form of carbon dioxide and
water which is converted into carbohydrates in the presence of sunlight and chlorophyll.
The carbohydrates which are not used immediately are stored in the form of starch,
which serves as the internal energy reserve by the plant. A somewhat similar situation is
seen in us where some of the energy derived from the food we eat is stored in our body
in the form of glycogen.
The process of photosynthesis is commonly written as:

7. This means that the reactants, six carbon dioxide molecules and six water
molecules, are converted by light energy captured by chlorophyll (implied by the
arrow) into a sugar molecule and six oxygen molecules, the products
During the process of photosynthesis: The following events occur during the
process :
1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting water molecule
into hydrogen and oxygen.
3. Reduction of carbon dioxide
Carbohydrates.

8. Cross section of a leaf : internally a leaf is comprised of three main parts :
i. Epidermis : It is the outermost one cell thick layer of leaf. It is comprised of
two parts: an upper epidermis which does not contain chloroplasts and a lower
epidermis which contains stomata.
ii. Stomata : stomata are tiny pores present on the surface of the Leaves.
Function of stomata :
Exchange of gases (oxygen and carbon dioxide
Loses large amount of water vapour during the process called Transpiration.
In certain group of plants lie desert plants, stomata remain closed during
day. They take up CO2 at night and produce an Intermediate organic acid which
is acted upon by the energy absorbed by chlorophyll during the day and breaks
up to release of CO2.The CO2 so produced internally is used in photosynthesis
During say when stomata are closed.

9. iii. Guard cells : these are bean shaped cells that frame Stomatal openings. It
contains chloroplast.
➔ Opening and closing of stomatal pores : The opening and closing stomatal
pores are controlled by turgidity of guard cells. When guard cells uptake the
turgidity of guard cells. when guard cells uptake water from surroundings cells,
they swell to become a turgid body. This enlarges the pore in between a causing
stomatal opening.
When water is released, they become flacid. This closes the pore in between
causing stomatal closing.

10. Activity 6.1
Procedure: Activity asks us to put a variegated leaf plant (e.g., Money plant) in
the dark for three days, and in sunlight for a few hours
Observation: Only the green coloured part of the leaf got the blue colour with the
iodine solution while the white portion of the money plant leaf did not get blue
colour.
Inference: Only the green part of the leaf photosynthesize and make starch.

11. Explanation: variegated leaf before and after the experiment. A variegated leaf
contains green as well as a non green part. The green part contains chlorophyll,
while the non green part is devoid of chlorophyll. To begin with the fresh
experiment, we put Leaf in the dark for a few days. Leaf in the dark do not
photosynthesize new starch, and the plant consumes all its previous starch. Now
the leaf is put into the sun. Here chlorophyll inside the chloroplast makes new
starch. A broken leaf can not transport starch to different parts of the body. So this
starch now remains localized to the green area only. We now put the leaf into
boiling alcohol. A boiling solution of alcohol breaks the cell wall and chloroplast.
This breakage washes the chlorophyll into the solution. As a result, leaf loses its
green colour and become colourless. The colourless leaf is easy to stain with
iodine. Now, when we put this colourless leaf into an iodine solution, only the
green part of the leaf turn blue.
Conclusion: In this experiment, we see that only the green part of the leaf turn
blue with iodine. So, we can say only the green part of the leaf photosynthesize
and produce starch. Since the green colour of the leaf is because of chlorophyll,
we can also say that only chlorophyll-containing part of the leaf makes starch.

12. Activity 6.2
Aim : To demonstrate carbon dioxide is essential for photosynthesis and starch
formation.
procedure: Activity 6.2 asks us to test for starch in a plant with iodine, and
compare it with the plant kept with potassium hydroxide.
Observation: Leaf of plant kept without potassium hydroxide turn blue with
iodine solution. The plant with potassium hydroxide does not turn blue.
Explanation: Potassium hydroxide is a highly reactive compound. It reacts with
the carbon dioxide of the bell and forms its carbonate.
KOH + CO2 —————> K2CO3 + H2O
As a result, no carbon dioxide is available for the plant. In the absence of Carbon
dioxide plant is unable to do photosynthesize and form starch. So, iodine does not
turn the leaf blue. The plant kept in bell without Potassium hydroxide can do
photosynthesis and form starch. So, iodine solution here turns the leaf blue.

13. conclusion: This experiment shows that carbon dioxide is necessary for
photosynthesis and starch formation.

14. Heterotrophic Nutrition: It is a kind of nutrition in which an organism takes
food from another organism do not posses the ability to synthesis their own
food. They depend on autotrophs for their food supply directly or indirectly.
E.g. Animals and fungi
There are three types of heterotrophic nutrition:
Holozoic
Nutrition
Saprophytic
Nutrition
Parasitic
Nutrition

16. Nutrition in Amoeba

17. Nutrition in Paramecium
In Paramecium, the food is taken in at a specific spot and is moved to this spot by
the movement of cilia, which cover the entire surface of the cell.

18. Nutrition in Human Beings

20. Activity 6.3
Aim: to see the effect of saliva on starch.
Procedure: Take 1mL starch solution (1%) in each of the test tubes (A and B). Add
1mL saliva to test tube A and leave the both the test tube undisturbed for 20-30
minutes. Now add a few drops of dilute iodine solution to the test tubes.
Observation: Iodine does not turn starch treated with saliva into blue colour.
Explanation: Saliva contains salivary amylase enzyme. It degrades starch into
simple sugar. Iodine does not act on the simple sugar. Hence solution treated
with saliva is not turned blue
Inference: Saliva degrades the starch

21. Reference: i. Class 10 NCERT book
ii. CBSE one for all (Oswaal books)

22. Thank you