1. What is the cell theory and why is the cell considered the basic unit of life?
Answer: The cell theory states that all living organisms are composed of cells, cells are the basic unit of structure and function in living organisms, and all cells come from pre-existing cells. The cell is considered the basic unit of life because it is the smallest unit that can perform all life processes.
2. Describe the structure of a prokaryotic cell.
Answer: Prokaryotic cells lack a true nucleus and membrane-bound organelles. They have a cell membrane, a cell wall, cytoplasm, ribosomes, and genetic material (DNA) that is not enclosed in a nuclear envelope.
3. What are the main differences between prokaryotic and eukaryotic cells?
Answer: Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus and membrane-bound organelles. Prokaryotic cells are generally smaller and simpler, while eukaryotic cells are larger and more complex.
4. How do plant cells differ from animal cells?
Answer: Plant cells have a cell wall, chloroplasts, and a large central vacuole, which are not present in animal cells. Animal cells have centrioles and lysosomes, which are not typically found in plant cells.
5. What is the structure and function of the cell envelope?
Answer: The cell envelope consists of the cell membrane, cell wall, and, in some bacteria, an outer membrane. It protects the cell, maintains its shape, and regulates the movement of substances in and out of the cell.
6. Explain the structure and function of the cell membrane.
Answer: The cell membrane is a phospholipid bilayer with embedded proteins. It regulates the movement of substances into and out of the cell, provides structural support, and facilitates communication and signaling between cells.
7. What is the role of the cell wall in plant cells?
Answer: The cell wall provides structural support, protection, and rigidity to plant cells. It also helps maintain cell shape and prevents excessive water uptake.
8. Describe the structure and function of the endoplasmic reticulum.
Answer: The endoplasmic reticulum (ER) is a network of membranous tubules and sacs. The rough ER has ribosomes and is involved in protein synthesis, while the smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.
9. What is the function of Golgi bodies in the cell?
Answer: Golgi bodies (or Golgi apparatus) modify, sort, and package proteins and lipids for storage or transport out of the cell.
10. Explain the role of lysosomes in cellular function.
Answer: Lysosomes contain digestive enzymes that break down waste materials, cellular debris, and foreign invaders like bacteria.
11. What are vacuoles, and what is their function in plant cells?
Answer: Vacuoles are large, membrane-bound sacs that store nutrients, waste products, and help maintain turgor pressure in plant cells.
12. Describe the structure and function of mitochondria.
Answer: Mitochondria have a double membrane with the inner membrane folded into cristae. They are the powerhouses of the cell, generating ATP through cellular respiration.
13. What is the role of ribosomes in the cell?
Answer: Ribosomes are the sites of protein synthesis, translating genetic information from mRNA to build proteins.
14. Explain the structure and function of plastids in plant cells.
Answer: Plastids are double-membrane organelles involved in the synthesis and storage of food. Chloroplasts, a type of plastid, contain chlorophyll and perform photosynthesis.
15. What are microbodies, and what functions do they perform?
Answer: Microbodies, such as peroxisomes and glyoxysomes, contain enzymes for specific metabolic reactions, including the breakdown of fatty acids and detoxification of hydrogen peroxide.
16. Describe the cytoskeleton and its functions.
Answer: The cytoskeleton is a network of protein filaments and tubules that provides structural support, facilitates cell movement, and helps organize cell division and intracellular transport.
17. What are cilia and flagella, and what is their function?
Answer: Cilia and flagella are hair-like structures that protrude from the cell surface. They are involved in cell movement and the movement of substances along the cell surface.
18. Describe the structure and function of the nucleus.
Answer: The nucleus is a membrane-bound organelle that contains the cell’s genetic material (DNA). It controls cellular activities by regulating gene expression.
19. What are the chemical constituents of living cells?
Answer: The chemical constituents of living cells include biomolecules such as proteins, carbohydrates, lipids, and nucleic acids, which perform various structural, functional, and regulatory roles in the cell.
20. Explain the process and significance of cell division.
Answer: Cell division involves the cell cycle, which includes mitosis and meiosis. Mitosis results in two genetically identical daughter cells, important for growth and repair, while meiosis produces four genetically diverse gametes, crucial for sexual reproduction.