Class 9 | Biology
Terms and defintions
- Cell: The cell is the basic structural and functional unit of all living organisms. It is the smallest unit of life. Cells can be classified into two main types: prokaryotic cells and eukaryotic cells.
- Prokaryotic Cells: These are cells that lack a well-defined nucleus and membrane-bound organelles. Bacteria are examples of organisms with prokaryotic cells.
- Eukaryotic Cells: These are cells that have a true nucleus enclosed within a nuclear membrane and membrane-bound organelles. All plants, animals, fungi, and protists consist of eukaryotic cells.
- Cell Membrane (Plasma Membrane): This is a thin, semi-permeable barrier that surrounds the cell. It controls the passage of substances in and out of the cell.
- Nucleus: In eukaryotic cells, the nucleus is the central control center that contains genetic material (DNA) and directs cellular activities.
- Cytoplasm: This is the gel-like substance inside the cell membrane where various cellular processes occur.
- Organelles: Organelles are specialized structures within eukaryotic cells that perform specific functions. Some important organelles include:
- Mitochondria: The powerhouse of the cell; it is responsible for energy production (ATP synthesis).
- Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis.
- Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for transport.
- Ribosomes: Involved in protein synthesis.
- Lysosomes: Contain enzymes for digestion and waste removal.
- Vacuoles (in plant cells): Storage organelles.
- Chloroplasts (in plant cells): Responsible for photosynthesis.
- Cell Wall (in plant cells): Provides structural support and protection.
- Mitosis: A process of cell division in which a single cell divides into two identical daughter cells. It is essential for growth and tissue repair.
- Meiosis: A type of cell division that occurs in reproductive cells (gametes) to produce four non-identical daughter cells with half the number of chromosomes, necessary for sexual reproduction.
- Cell Theory: The cell theory states that all living organisms are composed of cells, cells are the basic unit of life, and all cells come from pre-existing cells.
Quiz
Multiple choice questions
- What is the basic structural and functional unit of all living organisms?
a. Atom
b. Molecule
c. Cell
d. Tissue - Which type of cells lack a well-defined nucleus and membrane-bound organelles?
a. Prokaryotic cells
b. Eukaryotic cells
c. Animal cells
d. Plant cells - Which organelle is known as the “powerhouse of the cell”?
a. Nucleus
b. Mitochondria
c. Endoplasmic reticulum
d. Golgi apparatus - In eukaryotic cells, where is the genetic material (DNA) primarily located?
a. Nucleus
b. Mitochondria
c. Ribosomes
d. Cytoplasm - What is the function of the cell membrane (plasma membrane)?
a. Synthesizing proteins
b. Controlling the passage of substances in and out of the cell
c. Storing genetic information
d. Capturing sunlight for energy - Which type of cell division results in the formation of two identical daughter cells?
a. Meiosis
b. Mitosis
c. Binary fission
d. Budding - Which organelle is responsible for protein synthesis in the cell?
a. Mitochondria
b. Ribosomes
c. Lysosomes
d. Chloroplasts - What is the function of the Golgi apparatus in a cell?
a. Energy production
b. Protein synthesis
c. Modifying, sorting, and packaging of proteins
d. Waste removal - In plant cells, what organelle is responsible for photosynthesis?
a. Nucleus
b. Mitochondria
c. Chloroplasts
d. Lysosomes - Which type of cell division is essential for growth and tissue repair?
a. Mitosis
b. Meiosis
c. Binary fission
d. Budding - Which scientist is credited with formulating the cell theory?
a. Charles Darwin
b. Louis Pasteur
c. Robert Hooke
d. Gregor Mendel - What does the cell theory state about the origin of cells?
a. All cells originate from non-living matter.
b. All cells originate from pre-existing cells.
c. Cells can spontaneously generate under certain conditions.
d. Cells are created by the nucleus. - Which organelle contains enzymes for digestion and waste removal within the cell?
a. Ribosomes
b. Endoplasmic reticulum
c. Golgi apparatus
d. Lysosomes - What is the function of vacuoles in plant cells?
a. Energy production
b. Storage of genetic material
c. Storage of water and nutrients
d. Protein synthesis - What provides structural support and protection to plant cells?
a. Cell membrane
b. Nucleus
c. Cell wall
d. Cytoplasm - Which type of cells have a true nucleus enclosed within a nuclear membrane?
a. Prokaryotic cells
b. Eukaryotic cells
c. Animal cells
d. Bacterial cells - What is the primary function of chloroplasts in plant cells?
a. ATP synthesis
b. Protein synthesis
c. Photosynthesis
d. Waste removal - Which process of cell division is involved in the formation of gametes (reproductive cells)?
a. Mitosis
b. Meiosis
c. Binary fission
d. Budding - In prokaryotic cells, where is the genetic material (DNA) located?
a. Nucleus
b. Cytoplasm
c. Ribosomes
d. Endoplasmic reticulum - Which of the following is not one of the fundamental principles of the cell theory?
a. All living organisms are composed of cells.
b. Cells are the basic unit of life.
c. All cells have a true nucleus.
d. All cells come from pre-existing cells.
Key
- c. Cell
- a. Prokaryotic cells
- b. Mitochondria
- a. Nucleus
- b. Controlling the passage of substances in and out of the cell
- b. Mitosis
- b. Ribosomes
- c. Modifying, sorting, and packaging of proteins
- c. Chloroplasts
- a. Mitosis
- c. Robert Hooke
- b. All cells originate from pre-existing cells.
- d. Lysosomes
- c. Storage of water and nutrients
- c. Cell wall
- b. Eukaryotic cells
- c. Photosynthesis
- b. Meiosis
- b. Cytoplasm
- c. All cells have a true nucleus.
