1. Explain the structure and function of the nucleus in a eukaryotic cell.
Answer: The nucleus is a membrane-bound organelle found in eukaryotic cells. It contains the genetic material of the cell, including DNA and RNA, which are responsible for controlling cellular activities and hereditary information. The nucleus is surrounded by a double-layered nuclear envelope that separates it from the cytoplasm. It also contains a nucleolus, which is involved in the synthesis of ribosomes. The nucleus plays a crucial role in regulating gene expression, DNA replication, and cell division.
2. Compare and contrast prokaryotic and eukaryotic cells.
Answer: Prokaryotic cells are simple, single-celled organisms that lack a nucleus and other membrane-bound organelles. They have a cell wall, plasma membrane, and genetic material in the form of circular DNA. Eukaryotic cells, on the other hand, are more complex and found in plants, animals, fungi, and protists. They have a true nucleus and various membrane-bound organelles, such as mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Eukaryotic cells also have linear DNA organized into multiple chromosomes.
3. Describe the structure and function of mitochondria.
Answer: Mitochondria are double-membrane organelles found in eukaryotic cells. They are often referred to as the “powerhouses” of the cell due to their role in producing energy in the form of ATP through cellular respiration. The inner membrane of mitochondria contains numerous folds called cristae, which increase the surface area for ATP synthesis. Mitochondria also contain their own DNA and ribosomes, allowing them to replicate independently within the cell. They play a crucial role in various cellular processes, including metabolism, calcium signaling, and apoptosis.
4. Explain the process of cell division in eukaryotic cells.
Answer: Cell division in eukaryotic cells occurs through a process called mitosis. It involves several distinct phases, including interphase, prophase, metaphase, anaphase, and telophase. During interphase, the cell prepares for division by undergoing DNA replication and synthesizing new organelles. In prophase, the chromatin condenses into visible chromosomes, and the nuclear envelope disintegrates. During metaphase, the chromosomes align along the equator of the cell. In anaphase, the sister chromatids separate and move towards opposite poles of the cell. Finally, in telophase, the nuclear envelope reforms, and the cytoplasm divides, resulting in two daughter cells. Mitosis ensures the proper distribution of genetic material to daughter cells and plays a crucial role in growth, development, and tissue repair.
5. Discuss the role of the endoplasmic reticulum in protein synthesis and lipid metabolism.
Answer: The endoplasmic reticulum (ER) is a network of interconnected membranes found in eukaryotic cells. It can be divided into rough ER and smooth ER. Rough ER is studded with ribosomes and is involved in protein synthesis and modification. It synthesizes proteins destined for secretion or insertion into the cell membrane. Smooth ER lacks ribosomes and is involved in lipid metabolism, including the synthesis of lipids, detoxification of drugs and toxins, and regulation of calcium levels. The ER plays a crucial role in maintaining cellular homeostasis and is interconnected with other organelles, such as the Golgi apparatus and mitochondria.
6. Explain the structure and function of the Golgi apparatus.
Answer: The Golgi apparatus is a stack of flattened membranes found in eukaryotic cells. It consists of several compartments, including the cis-Golgi network, cis-Golgi, medial-Golgi, and trans-Golgi. The Golgi apparatus is involved in the modification, sorting, and packaging of proteins and lipids synthesized in the ER. It receives proteins from the ER in vesicles and modifies them by adding sugars, lipids, or phosphate groups. It then sorts the modified proteins and lipids into vesicles for transport to their final destinations within the cell or for secretion outside the cell. The Golgi apparatus plays a crucial role in maintaining the integrity and functionality of the cell.
7. Discuss the structure and function of lysosomes.
Answer: Lysosomes are membrane-bound organelles found in animal cells. They contain hydrolytic enzymes that break down various macromolecules, including proteins, nucleic acids, lipids, and carbohydrates. Lysosomes are involved in intracellular digestion, recycling of cellular components, and defense against pathogens. They can fuse with other vesicles or organelles to form autophagosomes, which engulf and degrade damaged organelles or intracellular pathogens. Lysosomal enzymes function optimally at an acidic pH, which is maintained by the proton pumps on the lysosomal membrane. Dysfunction of lysosomes can lead to lysosomal storage diseases.
8. Describe the structure and function of the plasma membrane.
Answer: The plasma membrane is a selectively permeable barrier that surrounds the cell and separates its internal environment from the external environment. It consists of a phospholipid bilayer embedded with proteins, cholesterol, and carbohydrates. The phospholipid bilayer provides fluidity and stability to the membrane. Proteins in the membrane serve various functions, including transport of molecules, cell adhesion, signal transduction, and enzymatic activity. Cholesterol helps maintain the fluidity of the membrane, while carbohydrates attached to proteins or lipids form glycoproteins and glycolipids involved in cell recognition and immune response. The plasma membrane plays a crucial role in maintaining cellular homeostasis and regulating the movement of substances into and out of the cell.
9. Discuss the role of microtubules and microfilaments in cell structure and movement.
Answer: Microtubules and microfilaments are components of the cytoskeleton, a network of protein filaments found in eukaryotic cells. Microtubules are hollow tubes composed of the protein tubulin and provide structural support to the cell. They also serve as tracks for the movement of organelles and vesicles within the cell. Microtubules are involved in cell division, cilia and flagella movement, and the formation of spindle fibers. Microfilaments, on the other hand, are thin filaments composed of the protein actin. They are involved in cell shape, muscle contraction, cell motility, and the formation of cellular extensions like microvilli and filopodia. The cytoskeleton plays a crucial role in maintaining cell structure, supporting cellular processes, and facilitating cell movement.
10. Explain the concept of cell signaling and the role of receptors in cellular communication.
Answer: Cell signaling is the process by which cells communicate with each other to coordinate their activities and respond to external stimuli. It involves the binding of signaling molecules, such as hormones or neurotransmitters, to specific receptors on the cell surface or within the cell. Receptors can be membrane-bound or intracellular and can activate various signaling pathways inside the cell. These pathways can lead to changes in gene expression, protein synthesis, enzyme activity, or cell behavior. Cell signaling plays a crucial role in development, immune response, cell growth, and cell differentiation. It ensures the proper functioning and coordination of cells within an organism.