Cell: The Unit of Life

Correct Answer: B

1. Ribosomes are small granular structures in cells.
2. They are involved in protein synthesis.
3. They are very tiny and not visible under light microscope.
4. Electron microscope helped in their discovery.
5. They appeared as dense particles.
6. These particles were first observed by George Palade.
7. This discovery was made in 1953.
8. His work was important in cell biology.
9. Ribosomes are now known as protein factories.
10. Thus, George Palade first observed ribosomes.

Correct Answer: B

1. Ribosomes are small structures in the cell.
2. They are made up of RNA and proteins.
3. RNA present is called ribonucleic acid.
4. These components form ribosomal subunits.
5. Ribosomes do not have any surrounding membrane.
6. So they are called non-membrane bound organelles.
7. They can be free in cytoplasm or attached to ER.
8. Their main function is protein synthesis.
9. They read genetic information to make proteins.
10. Thus, ribosomes are made of RNA and proteins and lack membrane.

Correct Answer: B

1. Ribosomes are involved in protein synthesis.
2. They are present in all living cells.
3. Their size differs in different organisms.
4. Eukaryotic cells have larger ribosomes.
5. These are called 80S ribosomes.
6. Prokaryotic cells have smaller ribosomes.
7. These are called 70S ribosomes.
8. The difference is due to their structure.
9. This helps in distinguishing cell types.
10. Thus, eukaryotic ribosomes are 80S and prokaryotic are 70S.

Correct Answer: B

1. Ribosomes are made up of two parts.
2. These parts are called subunits.
3. One subunit is larger in size.
4. The other subunit is smaller.
5. Both subunits join during protein synthesis.
6. They work together to read mRNA.
7. The larger subunit helps in forming peptide bonds.
8. The smaller subunit helps in reading genetic code.
9. After protein synthesis, they separate again.
10. Thus, ribosomes have larger and smaller subunits.

Correct Answer: B

1. Ribosomes are made of two subunits.
2. In eukaryotes, ribosomes are 80S type.
3. These consist of 60S (large) and 40S (small) subunits.
4. In prokaryotes, ribosomes are 70S type.
5. These consist of 50S (large) and 30S (small) subunits.
6. Subunits join during protein synthesis.
7. Each subunit has specific roles.
8. Larger subunit forms peptide bonds.
9. Smaller subunit reads mRNA.
10. Thus, 80S = 60S + 40S and 70S = 50S + 30S.

Correct Answer: B

1. ‘S’ stands for Svedberg unit.
2. It is used to describe ribosomes.
3. It represents sedimentation coefficient.
4. This is measured during centrifugation.
5. It shows how fast particles settle.
6. Faster settling means higher S value.
7. It depends on size of the particle.
8. It also depends on density of the particle.
9. Shape also influences sedimentation rate.
10. Thus, S value indicates density and size indirectly.

Correct Answer: B

1. Ribosomes are important for protein synthesis.
2. They are present in all living cells.
3. Ribosomes are made up of smaller parts.
4. These parts are called subunits.
5. Both 70S and 80S ribosomes have two subunits.
6. One is a larger subunit.
7. The other is a smaller subunit.
8. These subunits join during protein synthesis.
9. After the process, they may separate again.
10. Thus, both types of ribosomes have two subunits.

Correct Answer: B

1. Cells have a supporting internal framework.
2. This framework is made of protein filaments.
3. It includes microtubules, microfilaments and intermediate filaments.
4. These structures form a network in the cytoplasm.
5. This network gives shape to the cell.
6. It helps in movement of cell and organelles.
7. It provides mechanical support.
8. It is involved in cell division.
9. It maintains internal organization.
10. Thus, this network is called cytoskeleton.

Correct Answer: B

1. Cytoskeleton is a network of protein filaments in the cell.
2. It provides mechanical support to the cell.
3. It helps the cell maintain its shape.
4. It allows movement of the cell (motility).
5. It also helps movement of organelles inside the cell.
6. It plays a role in cell division.
7. It keeps internal structures properly arranged.
8. It helps in transport of materials within the cell.
9. It responds to external signals and changes.
10. Thus, cytoskeleton supports, shapes and enables movement of the cell.

Correct Answer: B

1. Cilia and flagella are extensions of the cell surface.
2. They arise from the cell membrane.
3. These structures are thin and long.
4. They look like tiny hairs.
5. Hence they are called hair-like outgrowths.
6. Cilia are short and numerous.
7. Flagella are long and fewer in number.
8. They help in movement of the cell.
9. They also move substances over the cell surface.
10. Thus, cilia and flagella are hair-like outgrowths.

Correct Answer: B

1. Cilia are small hair-like structures on the cell surface.
2. They are present in large numbers.
3. They beat in a coordinated manner.
4. Their movement is like oars in water.
5. This helps in movement of the cell.
6. It can also move fluid around the cell.
7. This function is important in many organisms.
8. For example, they help move mucus in human respiratory tract.
9. Their coordinated action is very efficient.
10. Thus, cilia move the cell or surrounding fluid.

Correct Answer: B

1. Flagella are long, whip-like structures.
2. They extend from the cell surface.
3. They are fewer in number compared to cilia.
4. They move in a wave-like manner.
5. This movement helps the cell to move.
6. They are important in organisms like sperm cells.
7. They provide propulsion in liquid medium.
8. Their structure supports effective movement.
9. They help the organism reach favorable conditions.
10. Thus, flagella are responsible for cell movement.

Correct Answer: B

1. Flagella are structures used for movement.
2. Both prokaryotic and eukaryotic cells can have flagella.
3. They perform similar function of locomotion.
4. However, their internal structure is different.
5. Prokaryotic flagella are simpler in structure.
6. Eukaryotic flagella have complex arrangement of microtubules.
7. They follow a 9+2 arrangement.
8. Prokaryotic flagella lack this arrangement.
9. Their movement mechanism is also different.
10. Thus, they are structurally different.

Correct Answer: B

1. Cilia and flagella are extensions of the cell surface.
2. They originate from the cell membrane.
3. Electron microscope helps in studying their structure.
4. It shows their outer covering clearly.
5. Both cilia and flagella are surrounded by plasma membrane.
6. This membrane is continuous with the cell membrane.
7. It protects the internal structure.
8. It helps in proper functioning of movement.
9. This feature is common in eukaryotic cells.
10. Thus, they are covered with plasma membrane.

Correct Answer: B

1. Cilia and flagella have an internal core structure.
2. This core is called the axoneme.
3. It is present inside the plasma membrane covering.
4. The axoneme contains microtubules.
5. These microtubules are arranged in a specific pattern.
6. They run parallel to the long axis.
7. This arrangement helps in movement.
8. It provides structural support.
9. It enables bending and motion of cilia and flagella.
10. Thus, the core is called axoneme with parallel microtubules.

Correct Answer: B

1. The axoneme is the core of cilia and flagella.
2. It contains microtubules arranged in a specific pattern.
3. There are nine doublets arranged around the edge.
4. These are called peripheral microtubules.
5. In the center, there are two single microtubules.
6. These form the central pair.
7. This arrangement is called 9+2 structure.
8. It is typical of eukaryotic cilia and flagella.
9. This structure helps in movement.
10. Thus, axoneme has nine peripheral doublets and a central pair.

Correct Answer: B

1. The axoneme has a specific microtubule arrangement.
2. There are nine doublets at the periphery.
3. There are two microtubules at the center.
4. This pattern is common in cilia and flagella.
5. It is written as 9+2 arrangement.
6. The number 9 represents peripheral doublets.
7. The number 2 represents central microtubules.
8. This structure helps in movement.
9. It is characteristic of eukaryotic cells.
10. Thus, it is called the 9+2 array.

Correct Answer: B

1. The axoneme has a central pair of microtubules.
2. These central tubules are connected by bridges.
3. They are surrounded by a structure called central sheath.
4. The central sheath provides support.
5. It connects to peripheral microtubules.
6. The connection is through radial spokes.
7. Radial spokes extend from central sheath outward.
8. They attach to each peripheral doublet.
9. This arrangement helps in coordinated movement.
10. Thus, bridges, central sheath and radial spokes are present.

Correct Answer: B

1. Axoneme has a 9+2 microtubule arrangement.
2. There are nine peripheral doublets.
3. Each doublet is connected to the central sheath.
4. This connection is through radial spokes.
5. One radial spoke arises from each doublet.
6. Since there are nine doublets, there are nine spokes.
7. These spokes help in structural support.
8. They also assist in coordinated movement.
9. This arrangement is typical in cilia and flagella.
10. Thus, there are nine radial spokes.

Correct Answer: B

1. The axoneme has nine peripheral microtubule doublets.
2. These doublets are arranged in a circular pattern.
3. They are not independent of each other.
4. They are connected to maintain structure.
5. The connections between them are called linkers.
6. These linkers hold adjacent doublets together.
7. They provide stability to the axoneme.
8. This helps in coordinated movement.
9. Proper linking ensures effective beating motion.
10. Thus, peripheral doublets are interconnected by linkers.

Correct Answer: B

1. Cilia and flagella are cell surface structures.
2. They arise from a base inside the cell.
3. This base is similar to a centriole.
4. Hence it is called centriole-like structure.
5. This structure is known as basal body.
6. Basal bodies help in organizing microtubules.
7. They form the base of cilia and flagella.
8. They provide support and anchoring.
9. This ensures proper structure and movement.
10. Thus, they arise from centriole-like basal bodies.

Correct Answer: B

1. Centrosome is an organelle found in animal cells.
2. It is located near the nucleus.
3. It plays a role in cell division.
4. Centrosome contains two small cylindrical bodies.
5. These structures are called centrioles.
6. They are arranged at right angles to each other.
7. Centrioles help in spindle formation.
8. This is important during mitosis and meiosis.
9. They also help in formation of cilia and flagella.
10. Thus, centrosome contains two centrioles.

Correct Answer: B

1. Centrioles are cylindrical structures in the centrosome.
2. They are not present alone in the cell.
3. Around them, a special material is present.
4. This material is not well defined in shape.
5. Hence it is called amorphous material.
6. It surrounds the centrioles.
7. It is known as pericentriolar material.
8. It helps in microtubule organization.
9. It supports cell division processes.
10. Thus, centrioles are surrounded by amorphous pericentriolar material.

Correct Answer: B

1. Centrosome contains two centrioles.
2. These centrioles are arranged at right angles.
3. This means they lie perpendicular to each other.
4. Each centriole has a special internal structure.
5. This structure looks like a cartwheel.
6. It has a central hub and radiating spokes.
7. Microtubules are arranged in this pattern.
8. This helps in stability and organization.
9. It is important during cell division.
10. Thus, centrioles are perpendicular and cartwheel-like.

Correct Answer: B

1. Centrioles have a specific structural arrangement.
2. They contain fibrils arranged around the periphery.
3. These fibrils are evenly spaced.
4. The number of these fibrils is fixed.
5. There are nine peripheral fibrils.
6. Each fibril is made of tubulin protein.
7. Tubulin forms microtubules in cells.
8. This structure provides stability and shape.
9. It is important for cell division and organization.
10. Thus, centrioles have nine tubulin fibrils.

Correct Answer: B

1. Centrioles have nine peripheral fibrils.
2. These fibrils are arranged in a circular pattern.
3. Each fibril is not single.
4. It is made up of three microtubules.
5. This arrangement is called a triplet.
6. Tubulin protein forms these microtubules.
7. This structure provides strength.
8. It helps in proper functioning during cell division.
9. It maintains centriole stability.
10. Thus, each fibril is a triplet.

Correct Answer: B

1. Centrioles contain nine peripheral triplets.
2. These triplets are arranged in a circular pattern.
3. They are not independent of each other.
4. Adjacent triplets are connected.
5. This connection is called linking.
6. It provides structural stability.
7. It maintains proper shape of the centriole.
8. It helps in microtubule organization.
9. This is important during cell division.
10. Thus, adjacent triplets are linked.

Correct Answer: B

1. Centrioles have a central region in their structure.
2. This central part is proteinaceous in nature.
3. It is called the hub.
4. The hub lies in the proximal region of centriole.
5. It is connected to peripheral triplets.
6. The connection is through radial spokes.
7. These spokes are also made of protein.
8. This arrangement forms a cartwheel structure.
9. It provides stability and organization.
10. Thus, the central part is hub connected by radial spokes.

Correct Answer: B

1. Centrioles are important structures in animal cells.
2. They help in formation of cilia and flagella.
3. They act as the base for these structures.
4. This base is called the basal body.
5. Centrioles also play a role in cell division.
6. They help in forming spindle fibres.
7. These fibres make the spindle apparatus.
8. Spindle apparatus helps in chromosome movement.
9. This process occurs in animal cells.
10. Thus, centrioles form basal bodies and spindle fibres in animal cells.