What is a centromere?
[question] Question. What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes. [/question] [solution] Solution: Centromere is a constriction present on the chromosomes where the chromatids are held together. Chromosomes are divided into four types based on the position of the centromere. (i) Metacentric chromosome The chromosomes in which the c...
Describe the structure of the following with the help of labelled diagrams.
[question] Question. Describe the structure of the following with the help of labelled diagrams. (i) Nucleus (ii) Centrosome [/question] [solution] Solution: (i) Nucleus Nucleus controls all the cellular activities of the cell. It is spherical in shape. It is composed of the following structures: Nuclear membrane: It is a double membrane separating the contents of the nucleus from the cytoplasm. The narrow space between the two membranes is called the perinuclear space. Nuclear membrane has tiny...
Both lysosomes and vacuoles are endomembrane structures,
[question] Question. Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment. [/question] [solution] Solution: Lysosomes are membrane-bound vesicular structures holding a variety of enzymes such as lipases, proteases, and carbohydrases. The purpose of lysosomes is to digest worn out cells. They are involved in the intracellular digestion of foreign food particles and microbes. Sometimes, they also act as suicidal bags. They are involved in th...
What are nuclear pores? State their function.
[question] Question. What are nuclear pores? State their function. [/question] [solution] Solution: Nuclear pores are tiny holes present in the nuclear membrane of the nucleus. They are formed by the fusion of two nuclear membranes. These holes allow specific substances to be transferred into a cell and out from it. They allow molecules such as RNA and proteins to move in both directions, between the nucleus and the cytoplasm. [/solution]...
Cell is the basic unit of life. Discuss in brief.
[question] Question. Cell is the basic unit of life. Discuss in brief. [/question] [solution] Solution: Cells are the basic units of life capable of doing all the required biochemical processes that a normal cell has to do in order to live. The basic needs for the survival of all living organisms are the same. All living organisms need to respire, digest food for obtaining energy, and get rid of metabolic wastes. Cells are capable of performing all the metabolic functions of the body. Hence, cel...
Multicellular organisms have division of labour. Explain.
[question] Question. Multicellular organisms have division of labour. Explain. [/question] [solution] Solution: Multicellular organisms are made up of millions and trillions of cells. All these cells perform specific functions. All the cells specialised for performing similar functions are grouped together as tissues in the body. Hence, a particular function is carried out by a group of cells at a definite place in the body. Similarly, different functions are carried out by different groups of c...
What are the characteristics of prokaryotic cells?
[question] Question. What are the characteristics of prokaryotic cells? [/question] [solution] Solution: Prokaryotic cell is a unicellular organism lacking membrane-bound organelles. The characteristics of prokaryotic cells are as follows: (i) Most of them are unicellular. (ii) They are generally small in size. The size of a prokaryotic cell varies from 0.5 – 5 µm. (iii) The nuclear region of a prokaryotic cell is poorly-defined because of the absence of a nuclear membrane. Hence, a prokaryotic ...
Name two cell-organelles that are double membrane bound.
[question] Question. Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both. [/question] [solution] Solution: Mitochondria and chloroplasts are the two organelles that are double-membrane-bound. Characteristics of the mitochondria Mitochondria are double- membrane-bound structures. The membrane of a mitochondrion is divided into the inner and outer membranes, distinctly divided into t...
How do neutral solutes move across the plasma membrane?
[question] Question. How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane? [/question] [solution] Solution: Plasma membrane is the outermost covering of the cell that separates it from the environment. It regulates the movement of substances into the cell and out from it. It allows the entry of only some substances and prevents the movement of other materials. Hence, the mem...
What is a mesosome in a prokaryotic cell?
[question] Question. What is a mesosome in a prokaryotic cell? Mention the functions that it performs. [/question] [solution] Solution: Mesosome is a convoluted membranous structure formed in a prokaryotic cell by the invagination of the plasma membrane. Its functions are as follows: (1) These extensions help in the synthesis of the cell wall, replication of DNA. They also help in the equal distribution of chromosomes into the daughter cells. (2) It also increases the surface area of the plasma ...
Match the following
[question] Question. [/question] [solution] Solution: [/solution]...
New cells generate from
[question] Question. New cells generate from (a) bacterial fermentation (b) regeneration of old cells (c) pre-existing cells (d) abiotic materials [/question] [solution] Solution: Answer: (c) According to the biogenic theory, new cells can only arise from pre-existing cells. Only complete cells, in favourable conditions, can give rise to new cells. [/solution]...