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The organisms which cannot be seen with our eyes but can only be observed under a microscope are called micro-organisms.

Micro-organisms which are helpful are called useful micro-organisms.

Uses:

1. Micro-organisms present in nodules of leguminous plants, convert atmospheric nitrogen into its compounds and these compounds help to increase the soil fertility and protein content in the soil.

2. Some micro-organisms are useful in process of fermentation, making the food easily digestible and more nutritious. For producing milk products like butter, buttermilk, cheese, paneer, etc.

3. Microbes present in soil, dung etc. decompose garbage and convert into manure of best quality and surrounding is kept clean.

4. Microbes are also useful for sewage disposal. They help in decomposition of organic compounds in it.

5. Microbes are used in production of vaccines.

6. Microbes are also used in processes like tanning of skin, production of ropes and strings, from agave.

7. Some microbes use oil for their growth. Such microbes are used to clear a layer of oil floating on the surface of an ocean or lake formed due to leak or spill.

8. Farm waste, human urine and faeces, wet garbage etc. is collected and used in a biogas plant to produce biogas and fertilizer.

Harmful effects:

1. Disease producing micro-organisms are called pathogens, they are harmful micro-organisms.

2. Fungus grows on moist food, and microbes release enterotoxins into the food. Such toxins spoil the foods. Eating such spoiled food causes food poisoning i.e. loose motions and vomiting.

3. Pathogens may be present in water bodies contaminated with sewage, and dirt from surroundings, in food with flies sitting on it. If such contaminated food or water is consumed, we may fall ill with diseases like amoebiasis, typhoid, cholera, hepatitis, gastro, etc.

4. Pathogens are released in the air by a person having infection of the respiratory, sneezes or coughs. A healthy person may get infected by pathogens on breathing in the same air and contract diseases like common cold, cough, diphtheria, pneumonia, tuberculosis, etc.

5. Microbes that cause diseases like malaria, dengue, elephantiasis, yellow fever, chikunguniya, zike fever etc. gain entry into the human body through the bite of a female mosquito.

Plasma membrane is Fluid structure due to presence of Lipid

(a) Selectively permeable

(d) All of the above

Syncytium: It refers to mass of cells formed by fusion of multiple uninuclear cells and followed by dissolution of the cell membrane. 

Coenocyte: It is a multinucleate cell resulted from multiple nuclear divisions without undergoing cytokinesis.

a. Mitochondria are found in nearly all eukaryotic cells, including plants, animals, fungi, and most unicellular eukaryotes. 

b. Some of the cells have a single large mitochondrion, but frequently a cell has hundreds of mitochondria. 

c. The number of mitochondria correlates with the cell’s level of metabolic activity. 

For e.g. cells that move or contract have proportionally more mitochondria than metabolically less active cells. 

d. However, mature red blood cells in humans lack mitochondria

1. Nucleolus 

2. Chloroplast 

3. Mitochondria 

4. Plasma membrane

1. A: Food vacuole 

B: Golgi complex 

C: Lysosome 

2. Intracellular digestion:

The intracellular digestion is brought about by autophagic vesicle or secondary lysosomes which contain foreign materials brought in by processes like phagocytosis.

E.g. Food vacuole in amoeba or macrophages in human blood that engulf and destroy harmful microbes that enter the body. 

3. Extracellular digestion: 

Extracellular digestion is brought about by release of lysosomal enzymes outside the cell. 

E.g. acrosome, a cap like structure in human sperm is a modified lysosome which contain various enzymes like Hyaluronidase. These enzymes bring about fertilization by dissolving protective layers of ovum.

1. Refrigerator is used to keep food item in healthy condition and to keep them fresh. 

2. If the food items are kept outside, they spoil very fast due to growth of micro-organisms and they make food spoiled and harmful. 

3. The optimum temperature for the growth of micro-organism is 15°C to 35°C. 

4. In refrigerator the temperature is kept very low. So, the food is preserved in refrigerator.

i. False. 

We can’t see cells with naked eyes, can be seen under microscope

ii. True

iii. False. 

Cell wall is present only in plant cell

iv. False. 

Large vacuole is found in plant cell

v. False. 

Tissue is a group of similar cells.

vi. True.

vii. False. 

The basic living unit of an organism is the cell.

viii. False. 

It is nanometer.

ix. False. 

Some micro-organisms can survive in extreme adverse conditions e.g. ocean floor, ice polar region, hot water spring.

x. True

1. Each micro-organism needs a specific environment for growth and reproduction. 

2. Optimum temperature for the growth of micro-organism is 15°C to 35°C. 

3. Normal body temperature of human body is 37°C. At that temperature micro-organism can not grow and cause disease.

i. Cell

ii. cell wall, cell membrane, cytoplasm, cell organelle

iii. chloroplast

iv. Mitochondria

v. cell wall

vi. plasma membrane

vii. nucleus

viii. Swach Bharat Abhiyan

ix. 37°C

x. enterotoxins

i. chloroplasts

ii. fertilizer

iii. chloroplast

iv. micro-organism

v. photosynthesis.

i. Vacuole

ii. Chlorophyll

iii. Cytoplasm

iv. Tissue

v. Vacuole

i. (a) cell

ii. (d) mitochondria

iii. (а) cytoplasm

i. (a) ribosome

ii. (b) cell organelle

iii. (d) cytoplasm

iv. (c) nanometre, (b) micrometre.

v. (a) nerve

vi. (a) plasma membrane

vii. (b) Robert Hooke

viii. (b) Schleiden, (c) Schwann.

ix. (a) cell wall

x. (b) CO₂

1. Plastids are classified according to the pigments present in it. Three main types of plastids are – leucoplasts, chromoplasts and chloroplasts. 

2. Leucoplasts do not contain any photosynthetic pigments they are of various shapes and sizes. 

These are meant for storage of nutrients: 

a. Amyloplasts store starch. 

b. Elaioplasts store oils.

 c. Aleuroplasts store proteins. 

3. Chromoplasts contain pigments like carotene and xanthophyll etc. 

a. They impart yellow, orange or red colour to flowers and fruits. 

b. These plastids are found in the coloured parts of flowers and fruits.

4. Chloroplasts are plastids containing green pigment chlorophyll along with other enzymes that help in production of sugar by photosynthesis. They are present in plants, algae and few protists like Euglena.

1. Plant cells show presence of plasmodesmata which are cytoplasmic bridges between neighbouring cells. 

2. This open channel through the cell wall connects the cytoplasm of adjacent plant cells and allows water, small solutes, and some larger molecules to pass between the cells. In this way, though plants have no circulatory system, plant cells manage intercellular transport.

(c) Mitochondria, chloroplast

1. The bacterial flagellum is an organelle for motility made up of three parts: 

a. The basal body that spans the cell envelope and works as a rotary motor; 

b. The helical fdament that acts as a propeller;

c. The hook that acts as a universal joint connecting these two to transmit motor torque to the propeller. 

2. The motor i.e. basal body drives the rotation of the long, helical filamentous propeller at hundreds of hertz to produce thrust that allows bacteria to swim in liquid environments. Therefore, basal body of bacterial flagella considered as smallest motor in the world.

Smooth endoplasmic reticulum (SER): 

1. Depending on cell type, it helps in synthesis of lipids for e.g. Steroid secreting cells of cortical region of adrenal gland, testes and ovaries. 

2. Smooth endoplasmic reticulum plays a role in detoxification in the liver and storage of calcium ions (muscle cells). 

Rough Endoplasmic Reticulum (RER): 

1. Rough ER is primarily involved in protein synthesis. 

For e.g. Pancreatic cells synthesize the protein insulin in the ER. 

2. These proteins are secreted by ribosomes attached to rough ER and are called secretory proteins. These proteins get wrapped in membrane that buds off from transitional region of ER. Such membrane bound proteins depart from ER as transport vesicles. 

3. Rough ER is also involved in formation of membrane for the cell.

The ER membrane grows in place by addition of membrane proteins and phospholipids to its own membrane. Portions of this expanded membrane are transferred to other components of endomembrane system.

a. Concave mirror is used when low-power objective lenses (useful for examining large specimens or many smaller specimens) or high-power objective lenses (useful for observing fine detail) are used, whereas plane mirror is used when oil immersion objective lens is used. 

b. The amount of light passing on to the specimen from the condenser (which concentrates and controls the light that passes through the specimen) is regulated by using iris diaphragm. 

c. Light is reduced by closing the diaphragm partially for use with dry objectives. 

d. Oil immersion objectives require maximum light and this can be achieved by keeping the iris diaphragm fully open.

a. Magnification is the ratio of an object’s image size to its actual size. 

b. Resolution is a measure of the clarity of the image; it is the minimum distance two points can be separated and still be distinguished as separate points.

1. We will see the expiry date. If the food is kept for a long period of time, it may allow the growth of many microbes which can cause disease or food poisoning. 

2. We will check for any fungal growth, any white or black spots on it.

1. The most important things for a cell are oxygen and glucose. 

2. Cell uses these during process of glycolysis and makes ATP which is energy source.

1. A thick liquid enclosed by cell membrane which surrounds the central nucleus in eukaryotes or nucleoid region in prokaryotes is known as cytoplasm. 

2. The cytoplasm shows presence of minerals, sugars, amino acids, t-RNA, nucleotides, vitamins, proteins and enzymes. 

3. The liquid or semiliquid substance within the nucleus is called the nucleoplasm. 

4. Nucleoplasm shows presence of various substances like nucleic acid, protein molecules, minerals and salts.

1. Glycoproteins are protein molecules modified within the Golgi complex by having a short sugar chain (polysaccharide) attached to them.

2. The polysaccharide part of glycoproteins located on the surfaces of red blood cells acts as the antigen responsible for determining the blood group of an individual. 

3. Different polysaccharide part of glycoproteins act as different type of antigens that determine the blood groups. 

4. Four types of blood groups A, B, AB, and O are recognized on the basis of presence or absence of these antigens.