LIFE PROCESS- PHOTOSYNTHESIS- CLASS X

Life Process: Activities which help to maintain life in an organism

Examples of Life activities: NUTRITION,RESPIRATION , EXCRETION, CIRCULATION, CONTROL AND CO-

ORDINATION,GROWTH AND MOVEMNT, REPRODUCTION

Significance of Nutrition:

maintenance processes are needed �to prevent damage and break-down� need energy � comes

from outside the body of the individual organism� a process to transfer a source of energy from

outside the body of the organism .This is called nutrition.

Different types of nutrition: Depending on the complexity of these carbon sources, different

organisms can use different kinds of nutritional processes.

Simple diffusion will not meet the requirements of all the cells.: When the body size of the organism

increases , the body design becomes more complex. In multi-cellular organisms, all the cells may not be in

direct contact with the surrounding environment.

NUTRITION

ENZYMES/ BIOCATALYSTS: Substances that alter the rate of biochemical reactions in an organism

Autotrophic Nutrition: . It is the process by which autotrophs take insimple inorganic substances like water

and carbon dioxide from the outside and convert them into stored forms ofchemical energy.( carbohydrates)

in the presence of sunlight and chlorophyll.

PHOTOSYNTHESIS

Photosynthesis: ( photo- light, Synthesis- to combine) The process of making food ( complex organic

substances glucose/starch)from simple inorganic materials like carbon dioxide and water by plants in

presence of chlorophyll and sunlight is called photosynthesis.

Raw materials needed for photosynthesis:

1. Carbondioxide ( taken from air through the stomata in leaves)

2. Water ( taken drom soil through roots)

Conditions needed for Photosynthesis:

1. Presence of chlorophyll

2. Presence of sunlight

Products of photosynthesis:

1 Glucose or carbohydrate ( Glucose is later changed to starch) 2 Oxygen

Organs of photosynthesis :

1. Leaves 2. Green parts of plant 3. In desert plants leaf like stem modifications do

photosynthesis

Structure of Leaf is suitable for doing Photosynthesis:

Main parts: 1. Upper epidermis: protective layer, coverred with cuticle

2 Mesophyll : Cells present between upper epidermis and lower epidermis. These cells

carry green pigment called Chlorophyll.Mesophyll is devided into two parts. Upper Palisade and lower

spongy area. More chloroplasts are seen in Palisade tisuue. Cells in the palidsade are columnar and

closely packed. Cells in the spongy tissue are rounded and loosely packed

Chlorophyll: is the green pigment which can absorb solar energy. Chlorophyll cantains

protein and Magnesium. Chlorophyll there are three types Chlorophyll a, Chlorophyll b , chlorophyll c

chlorophyll d and Bacterioclorophyll.

Chlorophyll a and b are common. Chlorophyll can absorb blue and red region of visible light.

3 Conducting tissue: Xylem Present in the vein. Brings water for photosynthesis

2. Lower epidermis: Protective layer in the lower part of the leaf. Stomata are seen in the

lower epidermis. Carbon dioxide is taken through the stomata.

3. Stomata: Tiny openings in the lower part of the leaves. Stomata can be opened and closed

4. Functions of Stomata: 1. Exchange of carbon dioxide and oxygen

2 Transpiration

Opening and closing of stomata: is controlled by guard cells. When the guard cells swell (

become turgid) due to the entry of water, the stomata are opened. When the guard cell shrink (

become flaccid) due to the loss of water , the stomata get closed.

In aquatic palnts, CO2 is obtained from the water which is dissolved in it.

Chlorophyll: is a green pigment which can absorb sunlight for photosynthesis. Chlorophyll

is present in green parts and leaves

Carbohydrate: Substances formed from carbon and hydrogen. Eg: Glucose, Starch

Reaction of photosynthesis: 6 CO2 + 12H2O ���� C6H12O6 + 6H2O+ 6 O2

Events that Occur during photosynthesis:

1. Absorption of light energy by chlorophyll

2. Conversion of light energy into chemical energy. ( Splitting of water molecules into oxygen

and hydrogen- Photolysis)

3. Reduction of carbon dioxide to carbohydrates.

Photosynthesis is completed in two steps:

1. Light Reaction ( Light dependent reaction, splitting of water/ photolysis/

release of hydrogen and oxygen)

2. Dark reaction ( light independent reaction, carbon dioxide is changed into

carbohydrate)

Photosynthesis in desert plants: Desert plants take up carbon dioxide at night and prepare an

intermediate compound ( by dark reaction) which is converted into carbohydrate during day time by

light reaction.

Variegated leaf: Leaf with color other than green are called variegated leaf.

Eg: Croton leaf, Coleus leaf

Destarching : The process of removing the starch present in a plant by keeping it a dark room for 72

hours .

Ganong’s Light Screen is an equipment used to experiment to show that sunkight is essential for

photosynthesis.

KOH: Potassium hydroxide is a substance which can absorb carbon dioxide.

Investigatory Project : Oxygen is evolved during Photosynthesis

Experiment to show that CO2 is essential for photosynthesis

Experiment to show that sunlight is essential for photosynthesis

Experiment to show that chlorophyll is essential for photosynthesis