Cell Organelles

Question What is the function of the **nucleus**? tap to flip ↻ Answer The nucleus contains the cell's genetic material (DNA) and controls cell activities such as growth, metabolism, and reproduction. Question Describe the structure of the **nucleus**. tap to flip ↻ Answer It is surrounded by a double membrane called the **nuclear envelope**, which has pores. Inside is the **nucleolus** and chromatin (DNA + proteins). Question What is the role of the **nucleolus**? tap to flip ↻ Answer The nucleolus is a dense region inside the nucleus where **ribosomes** are synthesized. Question What is the function of **ribosomes**? tap to flip ↻ Answer Ribosomes are the site of **protein synthesis** (translation). They assemble amino acids into polypeptides. Question Where are **ribosomes** found in a cell? tap to flip ↻ Answer They are found free in the cytoplasm or attached to the **rough endoplasmic reticulum**. Question What is the function of the **endoplasmic reticulum (ER)**? tap to flip ↻ Answer The ER is involved in **transport** of materials within the cell, **protein synthesis** (rough ER), and **lipid synthesis** (smooth ER). Question How do **rough ER** and **smooth ER** differ? tap to flip ↻ Answer **Rough ER** has ribosomes attached and makes proteins; **smooth ER** lacks ribosomes and makes lipids and detoxifies substances. Question What is the function of the **Golgi apparatus**? tap to flip ↻ Answer The Golgi apparatus modifies, sorts, and packages proteins and lipids for transport or secretion. Question Describe the structure of the **Golgi apparatus**. tap to flip ↻ Answer It consists of flattened, stacked membrane sacs called **cisternae** and associated vesicles. Question What is the function of **lysosomes**? tap to flip ↻ Answer Lysosomes contain digestive enzymes that break down waste materials, cellular debris, and foreign substances. Question Why are **lysosomes** called 'suicide bags'? tap to flip ↻ Answer Because if a lysosome ruptures, its enzymes can digest the cell itself (autolysis). Question What is the function of **mitochondria**? tap to flip ↻ Answer Mitochondria are the site of **cellular respiration**, producing ATP, the cell's energy currency. Question Describe the structure of a **mitochondrion**. tap to flip ↻ Answer It has a double membrane; the inner membrane is folded into **cristae**, increasing surface area. The interior is the **matrix**. Question What is the function of **chloroplasts**? tap to flip ↻ Answer Chloroplasts carry out **photosynthesis**, converting light energy into chemical energy (glucose). Question What is the structure of a **chloroplast**? tap to flip ↻ Answer It has a double membrane, internal stacks of **thylakoids** (grana), and a fluid **stroma** containing enzymes and DNA. Question What is the function of **vacuoles**? tap to flip ↻ Answer Vacuoles store water, nutrients, and waste; in plant cells, the large central vacuole maintains **turgor pressure**. Question How does the **central vacuole** in plant cells differ from vacuoles in animal cells? tap to flip ↻ Answer Plant cells typically have one large central vacuole; animal cells have small, temporary vacuoles. Question What is the function of the **cell membrane**? tap to flip ↻ Answer The cell membrane regulates the movement of substances into and out of the cell (selective permeability). Question What is the **fluid mosaic model** of the cell membrane? tap to flip ↻ Answer It describes the membrane as a fluid phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates that move laterally. Question What is the function of the **cell wall**? tap to flip ↻ Answer The cell wall provides structural support, protection, and shape to plant cells, fungi, and some bacteria. Question What is the main component of the **plant cell wall**? tap to flip ↻ Answer **Cellulose** is the primary structural polysaccharide in plant cell walls. Question What is the function of **cytoskeleton**? tap to flip ↻ Answer The cytoskeleton provides shape, support, and movement of cell parts; it includes microtubules, microfilaments, and intermediate filaments. Question What are **centrioles** and what is their role? tap to flip ↻ Answer Centrioles are cylindrical organelles that help organize microtubules during cell division (spindle formation). Question Which organelles are found in plant cells but not in animal cells? tap to flip ↻ Answer **Chloroplasts**, a large **central vacuole**, and a **cell wall**. Question Which organelles are found in animal cells but not in plant cells? tap to flip ↻ Answer **Centrioles** (typically) and **lysosomes** (though plant cells may have similar functions). Question What is the function of **peroxisomes**? tap to flip ↻ Answer Peroxisomes break down fatty acids and detoxify harmful substances, producing hydrogen peroxide which they then neutralize. Question What is the role of **vesicles** in a cell? tap to flip ↻ Answer Vesicles transport materials between organelles and to/from the cell membrane. Question How does the **nuclear envelope** control movement? tap to flip ↻ Answer The nuclear envelope has **nuclear pores** that regulate the transport of molecules (like RNA and proteins) between the nucleus and cytoplasm. Question What is the **endomembrane system**? tap to flip ↻ Answer It is a network of membranes including the nuclear envelope, ER, Golgi, lysosomes, and vesicles that work together in protein and lipid synthesis and transport. Question What is the function of **chromatin**? tap to flip ↻ Answer Chromatin is the complex of DNA and proteins (histones) that packages DNA into a compact form within the nucleus. Question What is the difference between **prokaryotic** and **eukaryotic** cells regarding organelles? tap to flip ↻ Answer Prokaryotic cells lack membrane-bound organelles (no nucleus, mitochondria, ER, etc.); eukaryotic cells have them. Question Which organelle is responsible for **ATP production**? tap to flip ↻ Answer **Mitochondria** produce ATP through cellular respiration. Question What is the function of **thylakoids**? tap to flip ↻ Answer Thylakoids are membrane sacs inside chloroplasts where the light-dependent reactions of photosynthesis occur. Question What is the **stroma**? tap to flip ↻ Answer The stroma is the fluid-filled space inside a chloroplast surrounding the thylakoids; it is the site of the Calvin cycle (light-independent reactions). Question What is the role of **cristae** in mitochondria? tap to flip ↻ Answer Cristae are folds of the inner mitochondrial membrane that increase surface area for ATP production. Question What is the function of the **Golgi apparatus** in secretion? tap to flip ↻ Answer It packages proteins into vesicles that fuse with the cell membrane, releasing contents outside the cell (exocytosis). Question What is **autophagy**? tap to flip ↻ Answer Autophagy is the process by which lysosomes digest the cell's own damaged organelles and macromolecules. Question What is the function of **microvilli**? tap to flip ↻ Answer Microvilli are finger-like projections of the cell membrane that increase surface area for absorption. Question Which organelle is known as the **'brain' of the cell**? tap to flip ↻ Answer The **nucleus** is often called the brain of the cell because it controls cell activities. Question What is the function of **flagella** and **cilia**? tap to flip ↻ Answer They are hair-like structures that aid in cell movement or move substances across the cell surface.