Cell The Unit Of Life Module

Q 1. Animal cells are connected by _______

1. Desmosome
2. Cell wall
3. Cell Membrane
4. Plasmodesmata

Answer – 4, Plasmodesmata
Explanation: Plasmodesmata are thin strands of cytoplasm that connect the cytoplasm of adjacent cells, allowing for the exchange of materials such as proteins and ions. Animal cells are connected by plasmodesmata, while plant cells are connected by desmosomes and a cell wall surrounding them.

Q 2. The rRNA is synthesized by _________

1. Golgi body
2. Nucleus
3. Nucleolus
4. Cytoplasm

Answer – 3, Nucleolus
Explanation: The rRNA is synthesized by the Nucleolus. The Nucleolus is a specialized structure found in the nucleus of eukaryotic cells and is the site for rRNA synthesis. It contains ribosomal proteins and nucleic acids, among other components, and its primary function is to produce ribosomal subunits for protein synthesis.

Q 3. Hammerling Experiment on Acetabularia involves exchanging of

1. Nucleus
2. Cytoplasm
3. Gametes
4. Rhizoid

Answer – 1, Nucleus
Explanation: The Hammerling Experiment, conducted by German biologist Johannes Holtfreter in the 1930s and later expanded upon by Ernst Hammerling, involved exchanging the nucleus between two different species of Acetabularia. This single-celled green algae has a unique appearance, resembling an umbrella or mushroom with a long stalk called a rhizoid anchoring it to the substrate, and a cap-like structure called the capitulum. By transferring the nucleus – which holds genetic information – from one species to another, Hammerling discovered that the Acetabularia cap regenerated according to the donor nucleus’s instructions regardless of its original body form. Such findings demonstrated how pivotal the nucleus is in determining an organism’s development and physical traits and helped further our knowledge of genetics and cell biology.

Q 4. The endomembrane system does not include which of the following?

1. Lysosome
2. Vacuole
3. Golgi complex
4. Peroxisome

Answer – 4, Peroxisome
Explanation: The endomembrane system involves the different membranes that are found in a cell and includes the nucleus, endoplasmic reticulum, Golgi complex, and lysosomes. The peroxisome is an organelle responsible for breaking down fatty acids and other molecules.

Q 5. Centriole takes part in the formation of ________?

1. Nucleus
2. Spindle
3. Cell plate
4. To start cell division

Answer – 2, Spindle
Explanation: Centrioles are small cylindrical structures found in animal cells, composed of microtubules. They play an essential role in cell division, specifically the formation of the spindle apparatus. This is the structure responsible for the separation and sharing out of duplicated chromosomes to two daughter cells. Its complexity is made possible through centrioles working as organizing centers, duplicating themselves before cell division and moving to opposite ends of the cell. There, they connect with spindle fibers which attach to the replicated chromosomes and help pull them apart. Thus, centrioles are indispensable for ensuring that genetic material is accurately distributed during mitosis and meiosis processes.

Q 6. Which of the following cells can divide?

1. red blood cells
2. muscle cells
3. skin cells
4. nerve cells

Answer – 4, Nerve Cells
Explanation: Nerve cells, also known as neurons, are nervous system cells responsible for transmitting electrical signals and communication within the body. Unlike red blood cells, muscle cells, and skin cells, nerve cells cannot divide once they have fully matured.

Nerve cells cannot divide, if any, in the mature nervous system. Once they have reached their mature state, most nerve cells lose the ability to undergo cell division. This lack of division contributes to the challenges of nerve cell regeneration and repair in the central nervous system.

Q 7. Which Organelles serve as major packaging regions for molecules distributed throughout the cell?

1. Vacuole
2. Plastid
3. Mitochondria
4. Golgi bodies

Answer – 4, Golgi bodies
Explanation: Golgi bodies, also known as the Golgi apparatus or complex, are organelles in eukaryotic cells. They play a crucial role in the packaging, processing, and distributing of molecules within the cell.

The Golgi bodies receive molecules, such as proteins and lipids, from the cell’s endoplasmic reticulum (ER). These molecules undergo modification and sorting within the Golgi apparatus. Various enzymes in the Golgi bodies perform chemical transformations, such as adding sugar molecules to proteins to form glycoproteins.

The Golgi bodies consist of flattened membrane sacs called cisternae. Within these cisternae, molecules are sorted and packaged into vesicles. These vesicles can then transport the molecules to their intended destinations, both within the cell and outside of it.

Q 8. Cell theory does not apply to

1. Fungus
2. Algae
3. Virus
4. Bacteria

Answer – 3, Virus
Explanation: The cell theory is a fundamental principle in biology that describes the basic structural and functional unit of all living organisms as the cell. It states that:

1. All living organisms are composed of cells.
2. The cell is the basic unit of structure and organization in organisms.
3. Cells arise from pre-existing cells through cell division.

While the cell theory applies to most living organisms, including plants, animals, fungi, and bacteria, it does not apply to viruses. Viruses are considered non-living entities and are not made up of cells. Instead, viruses comprise genetic material (DNA or RNA) surrounded by a protein coat called a capsid. They cannot carry out vital life processes on their own and require a host cell to replicate and reproduce.

Q 9. Organelles can be separated from the homogenate cell by

1. Autoradiography
2. Differential centrifugation
3. Chromatography
4. X-ray diffraction

Answer – 2, Differential Centrifugation
Explanation: Differential centrifugation is a well-known technique for separating organelles from a homogenate of disrupted cells. The principle involves the use of centrifugal force to take advantage of the different sedimentation rates of the organelles present. It is achieved by successive rounds of centrifugation at increasing speeds; the highest speed isolates the smallest and lightest organelle, while lower speeds separate the larger and denser elements, such as nuclei and cellular debris. Thus, this method allows various organelles such as mitochondria, lysosomes, peroxisomes, and microsomes to be segregated according to their respective size and density.

Q 10. The Middle lamella is mainly composed of

1. Hemicellulose
2. Muramic acid
3. Calcium pectate
4. Phosphoglycerides

Answer – 3, Calcium pectate
Explanation: The middle lamella of plant cells is mainly composed of calcium pectate, a type of pectin made up of galacturonic acid residues. Calcium ions bound to the pectin molecules are crucial for their adhesive properties, allowing them to stick to adjacent cells and help maintain the plant tissue’s integrity. Hemicellulose, muramic acid, and phosphoglycerides are not typically found in the middle lamella. Thus, calcium pectate plays an integral part in keeping plant cells united.

Q 11. Which of the following structures between two adjacent cells is an effective transport pathway?

1. Plasma
2. Endoplasmic reticulum
3. Plastoquinone
4. Plasmodesmata

Answer – 4, Plasmodesmata
Explanation: Plasmodesmata are specialized structures that connect adjacent plant cells, creating channels for the direct exchange of molecules and substances such as water, nutrients, signaling molecules, and even some proteins and RNA. These channels provide an effective pathway for transport and communication between cells, allowing them to coordinate various cellular activities, including nutrient transport, signaling, and defense responses within plant tissues. In contrast, the plasmalemma is just the cell membrane that regulates movement into and out of the cell; the endoplasmic reticulum aids in protein synthesis, modification, and lipid metabolism; while plastoquinones transfer electrons within the thylakoid membrane of chloroplasts. As such, plasmodesmata are uniquely equipped to serve as a transport pathway between adjacent cells.

Q 12. The osmotic expansion of cells maintained in water is mainly regulated by

1. Ribosomes
2. Vacuole
3. chloroplast
4. Mitochondria

Answer – 2, Vacuole
Explanation: The main regulator of the osmotic expansion of cells maintained in water is the vacuole. It uses osmosis to regulate the amount of water and other solutes that enter or exit a cell, maintaining the pressure inside it. The mitochondria and chloroplast also play important roles in this process, but they are not the primary regulators. Ribosomes, on the other hand, are mainly responsible for protein synthesis within the cell.

Q 13. Which of the following is the largest constituent of the membrane of the erythrocyte in human beings and is also responsible for performing most of the functions of the membrane

1. Proteins
2. Lipids
3. Glycolipids
4. Glycoproteins

Answer – 2, Lipids
Explanation: Lipids are the largest constituent of the membrane of the erythrocyte in human beings and are also responsible for performing most of the functions of the membrane. Lipids are composed of triglycerides, cholesterol, phospholipids, and sphingomyelin which form a bilayer that is semi-permeable and acts as a barrier to separate intracellular components from extracellular components. The proteins act mainly as receptors for other molecules, enzymes, or hormones, while lipids aid in controlling diffusion rates and maintaining structural integrity.

Q14. Plastids used in storing proteins are called:

1. Aleuroplasts
2. Elaioplasts
3. Chromoplasts

Answer – 4, Chromoplast
Explanation: The correct answer is Chromoplasts. Plastids are organelles found in plant cells and they are responsible for storing proteins, pigments, lipids, and other molecules. Chromoplasts are specialized plastids responsible for synthesizing and keeping pigments such as chlorophylls and carotenoids that contribute to the color of plants.

Q 15. Who concluded, based on his studies on plant tissues, that the presence of a cell wall is a unique character of plant cells?

1. Mathias Schleiden.
2. Theodore Schwann
3. Rudolph Virchow
4. Robert Hooke

Answer- 1, Mathias Schleiden
Explanation: Mathias Schleiden was the scientist who concluded, based on his studies on plant tissues, that the presence of cell walls is a unique characteristic of plant cells. This was an important discovery in cell biology and laid the foundation for further research into the structure and function of cells.