Cell Membrane

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Cell Wall

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Nucleus and Chromosomes

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Introduction to Eukaryotic Cells

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Endomembrane System

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Mitochondria

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Ribosomes

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Microbodies

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Centrosomes and Centrioles

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Cytoskeleton

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Cilia and Flagella

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Q: Which of the following options are not a function of ribosomes?(i) It helps in manufacture of protein molecules.(ii) It helps in manufacture of enzymes.(iii) It helps in manufacture of hormones.(iv) It helps in manufacture of starch molecules.

Ribosomes are majorly involved in protein synthesis, as these are the sites of protein synthesis and enzymes. It also synthesizes amino acids which polymerize to form proteins.

Q: Draw a well labelled diagram of nucleus.

The nucleus is considered as the director or controller of the cell. The nucleus is a double membrane-bound organelle. The nuclear envelope consists of two membranes, an outer membrane, and an inner membrane.The nuclear membrane is perforated by apertures known as nuclear pores.Nuclear membranes surround the cytoplasm of nucleus known as nucleoplasm. DNA is present in nucleoplasm in the form of chromatin. When the cell prepares to divide, the chromatin condenses and thickens into chromosomes.Within the nucleus is present a spherical body known as nucleolus which is closely associated with nucleolar organizer region of two or more chromosomes of the set.

Q: Give reasons why mitochondria is called powerhouse of the cell?

Mitochondria are cell organelles present in the eukaryotic cells. They are involved in the cellular respiration. They releases energy from food. They generate energy rich molecules, ATP from cellular respiration which is later used for other process. Hence, mitochondria are called as the powerhouses of the cell.

Q: Name the types of chromosomes based on the position of centromere and draw suitable diagram for each.

The type of chromosomes based on the position of centromere are of the following four types : 1) Metacentric chromosome: centromere in middle forming two equal arms.2) Sub-metacentric chromosome: centromere placed near to one end resulting in one shorter and one long arm.3) Acrocentric chromosome: Centromere placed close to one end forming one extreme short and one extreme long arm.4) Telocentric chromosome: terminally placed centromere.

Q: State the major functions of the following:(a) Plasma membrane (b) Ribosome(c) Lysosome (d) Mitochondria(e) Golgi apparatus (f) Cytoplasm(g) Asters of centrosome (h) Chromosomes(i) Glycogen granule (j) Vacuoles

The functions of the given are :(a) Plasma membrane It separates the content of the cell from its surroundings.It regulates the entry of certain solids and ions into the cell.It maintains the shape of the cell that is the animal cell.(b) RibosomeIts main function is Protein synthesis.(c) Lysosome Intracellular digestion and Destroy foreign substances.When a cell is old or injured this rapidly destroy organelles hence called suicide bags.(e) Golgi apparatusSynthesis and secretion of enzymes, hormones and etc.The formation of acrosome of sperm.(d) MitochondriaRelease of energy form pyruvic acid produced in the cytoplasm in the form of ATP and helps in the Synthesis of respiratory enzymes.(f) CytoplasmDifferent organelle is contained in it perform different functions.All metabolic activities occur in it.Medium of earlier steps of respiration(g) Asters of centrosomePresent in an animal cell and helps during the process of mitosis. (h) ChromosomesChromosomes carry hereditary information or genes.(i) Glycogen granuleStarch glycogen and fat containing granules serve as food for the cell.(j) VacuolesStorage of water and other substances, food pigments and waste products.Give turgidity to the plant cell by pressing against a cell wall.

Q: Which cell organelles are present in both animal and plant cells?

The plant and animal cells are eukaryotic and contain well developed cellular organelles. The cell membrane, cytoplasm, chromosomes, and mitochondria are the structures that are present in both the plant and the animal cells. The cell wall and chloroplast are present only in the plant cell. Thus, the correct answer is option B.

Q: Describe the structure of nucleus.

The nucleus is a sphere-shaped organelle found in eukaryotic cells. It contains the genetic material of the cell in the form of nucleic acids. It is responsible for controlling all activities of the cell. and contains a nuclear membrane, chromosomes, nucleolus and nucleoplasm.

Q: Which of the following is not a function of cytoskeleton in a cell?

Since all options are functions of the cytoskeleton, none of the options is correct.Cytoskeletal structures occur only in eukaryotic cells. They are externally small, fibrous and tubular structures that maintain cell shape and support the organelles. They also help in intracellular transport.

Q: Give reasons why lysosomes are called suicidal bag of the cells.

Lysosomes are called suicidal bags of cells. They contain hydrolytic enzymes. If the cell is damaged, the lysosomes undergo autolysis and burst open. This results in the release of those hydrolytic enzymes. The released enzymes then digest their own cell and ultimately the cell dies. Hence, they are called suicidal bags of the cells.