Chapter 6 Study Guide: A Tour of the Cell PDF

Chapter 6 Study Guide: A Tour of the Cell Concept 6.1: Biologists use microscopes and biochemistry to study cells 1\. Magnification vs. Resolving Power: Magnification enlarges the image of a specimen. Resolving power is the ability of a microscope to distinguish two points as separate entiti...

Chapter 6 Study Guide: A Tour of the Cell Concept 6.1: Biologists use microscopes and biochemistry to study cells 1\. Magnification vs. Resolving Power: Magnification enlarges the image of a specimen. Resolving power is the ability of a microscope to distinguish two points as separate entities. (High resolving power yields clearer, more detailed images.) 2\. Disadvantage of the Electron Microscope: Samples must be placed in a vacuum and are typically fixed, dehydrated, and sometimes coated with heavy metals, which means you cannot view living cells. 3\. Types of Electron Micrograph Images: Scanning Electron Microscopy (SEM): Provides 3D images of the specimen's surface topography. Transmission Electron Microscopy (TEM): Produces detailed, 2D images of thin sections, revealing internal structures at high resolution. 4\. Smallest Organelles Isolated in Cell Fractionation: Ribosomes are among the smallest organelles separated through high-speed centrifugation. Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions 5\. Prokaryotic Domains: The two domains with prokaryotic cells are Bacteria and Archaea. 6\. DNA Location Difference: In prokaryotes, DNA is located in a region called the nucleoid (not enclosed by a membrane). In eukaryotes, DNA is enclosed within a nucleus. 7\. Labeling Features on a Prokaryotic Cell Diagram: Cell Wall: Rigid structure providing shape and protection. Plasma Membrane: Lipid bilayer regulating material exchange. Bacterial Chromosome: Circular DNA containing genetic information. Nucleoid: Region where the chromosome is located. Ribosomes: Sites of protein synthesis. Flagella: Tail-like structures used for motility. 8\. Why Cells Are So Small: As a cell increases in size, its volume grows faster than its surface area, which limits the rate at which materials can be exchanged with the environment. 9\. Microvilli Function: They greatly increase the surface area of a cell (e.g., intestinal epithelial cells), thereby enhancing absorption. 10\. Surface Area-to-Volume Ratio Comparison and Calculation: Cell A (125 × 1 × 1): Volume: 125 cubic units Surface Area: 2\[(125×1) + (125×1) + (1×1)\] = 2\[125 + 125 + 1\] = 502 square units SA:Volume Ratio: 502/125 ≈ 4.02 Cell B (5 × 5 × 5): Volume: 125 cubic units Surface Area: 6 × (5×5) = 6×25 = 150 square units SA:Volume Ratio: 150/125 = 1.2 Conclusion: The elongated cell (A) has a much higher SA:Volume ratio, which facilitates more efficient exchange of materials. Concept 6.3: The eukaryotic cell's genetic instructions are housed in the nucleus and carried out by the ribosomes 12\. Nuclear Envelope: A double membrane (inner and outer) that encloses the nucleus. Nuclear pores traverse the envelope, allowing molecules (like mRNA) to pass between the nucleus and cytoplasm. 13\. Nuclear Lamina and Nuclear Matrix: Nuclear Lamina: A meshwork of protein filaments (lamins) lining the inner side of the inner nuclear membrane, providing structural support. Nuclear Matrix: A framework of fibers that organizes chromatin and helps maintain the shape of the nucleus. 14\. Components of Chromatin and Condensation: Chromatin consists of DNA and histone proteins. During interphase, chromatin is loosely organized; during cell division (mitosis), it condenses into visible chromosomes. 15\. Nucleoli: Visible during interphase; these are sites where ribosomal RNA is synthesized and ribosomes are assembled. 16\. Function and Components of Ribosomes: Function: Protein synthesis. Components: Composed of ribosomal RNA (rRNA) and proteins; they consist of two subunits (small and large). 17\. Ribosome Types and Their Functions: **Type of Ribosome** **Location** **Product** ---------------------- ---------------------- ---------------------------------------------------------- Free ribosomes Cytosol Proteins that function within the cytosol Bound ribosomes Attached to rough ER Proteins destined for secretion, membranes, or lysosomes Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell 18\. Structures of the Endomembrane System: Nuclear envelope, Endoplasmic reticulum (rough and smooth), Golgi apparatus, Vesicles, Lysosomes, Vacuoles, and the plasma membrane. 19\. Endoplasmic Reticulum (ER) Sketch Details: Lumen: The interior space of the ER where protein folding and modification occur. Transport Vesicles: Small membrane-bound carriers that shuttle proteins and lipids between ER, Golgi, and other destinations. Rough ER vs. Smooth ER: Rough ER is studded with ribosomes (protein synthesis); smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification. 20\. Functions of the Smooth ER: Lipid synthesis (phospholipids, steroids) Detoxification of harmful substances (e.g., drugs, alcohol) Storage of calcium ions 21\. Alcohol and Drug Tolerance: Chronic alcohol use induces smooth ER enzyme production, which increases the metabolism (detoxification) of other drugs (like barbiturates), leading to tolerance. 22\. Protein Processing in the ER: As secretory proteins are synthesized by ribosomes on the rough ER, they enter its lumen for proper folding and glycosylation before being packaged into vesicles. 23\. Additional Rough ER Function: It is also involved in the synthesis of membrane-bound proteins. 24\. Golgi Apparatus Functions: Cis face: Receives vesicles from the rough ER. Medial region: Modifies proteins (e.g., glycosylation, phosphorylation). Trans face: Sorts and packages proteins into vesicles for secretion or delivery to other organelles. 25\. Lysosomes: Definition: Membrane-bound vesicles containing hydrolytic enzymes. Contents: Enzymes that function at acidic pH (around pH 5) to digest macromolecules, organelles, and engulfed particles. 26\. Phagocytosis and Lysosomes: Cells such as macrophages engulf large particles or pathogens into a phagosome, which then fuses with lysosomes for degradation. 27\. Autophagy: The process by which cells degrade and recycle their own components by sequestering them in autophagosomes that eventually fuse with lysosomes. 28\. Tay--Sachs Disease: Caused by a deficiency of a lysosomal enzyme (hexosaminidase A), leading to the accumulation of gangliosides (lipid--sugar complexes) in neurons, which ultimately causes cell death. 29\. Types of Vacuoles: Food Vacuoles: Temporary storage for ingested materials in phagocytic cells. Contractile Vacuoles: Expel excess water in freshwater protists. Central Vacuoles (in plants): Large, persistent storage organelles that maintain turgor pressure and store nutrients/waste. 30\. Endomembrane System Coordination (Diagram): Proteins synthesized on the rough ER are packaged into vesicles → transported to the Golgi apparatus for modification and sorting → dispatched in vesicles that fuse with the plasma membrane (for secretion) or with lysosomes (for degradation). Concept 6.5: Mitochondria and chloroplasts change energy from one form to another 31\. Endosymbiont Theory and Supporting Evidence: Theory: Mitochondria and chloroplasts were once free-living prokaryotes that were engulfed by ancestral eukaryotic cells. Evidence: They have double membranes. They contain their own circular DNA similar to bacterial genomes. They reproduce by binary fission and have ribosomes resembling those of bacteria. 32\. Mitochondrion Diagram Labels: Outer Membrane Inner Membrane (folded into cristae to increase surface area) Intermembrane Space Matrix (contains enzymes, mitochondrial DNA, and ribosomes) 33\. Chloroplast Diagram Labels: Outer Membrane Inner Membrane Intermembrane Space Thylakoids (stacked into grana) where light reactions occur Stroma (fluid matrix where the Calvin cycle takes place) 34\. Mitochondria Function: The production of ATP through cellular respiration. 35\. Chloroplast Function: The conversion of light energy to chemical energy via photosynthesis. 36\. Folding of the Inner Mitochondrial Membrane and Thylakoid Function: Both structures increase the available surface area to house electron transport chain proteins, which is critical for ATP synthesis (in mitochondria) and for capturing light energy (in chloroplasts). 37\. Peroxisome Roles: Breakdown of fatty acids by β--oxidation. Detoxification of hydrogen peroxide using the enzyme catalase. 38\. Compartmentalization Advantages: It isolates potentially harmful reactions (e.g., reactive oxygen species in peroxisomes) and creates specialized microenvironments to increase metabolic efficiency. Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell 39\. Cytoskeleton Definition: A dynamic network of protein fibers that maintains cell shape, secures organelles in specific positions, and enables cell movement. 40\. Three Types of Cytoskeletal Fibers: Microfilaments (actin filaments) Intermediate Filaments Microtubules 41\. Functions of the Cytoskeleton: Maintains cell shape and structure. Facilitates cell movement and intracellular transport. Organizes and anchors organelles. 42\. Microtubule Functions: Serve as "tracks" for motor proteins during vesicle and organelle transport. Form the spindle apparatus during cell division. Are the structural core of cilia and flagella. 43\. Role of Centrioles: In animal cells, centrioles (located in the centrosome) help organize microtubules and direct the formation of the mitotic spindle during cell division. 44\. Cilia vs. Flagella: Cilia: Numerous, short, and beat in a coordinated fashion. Found in respiratory epithelial cells (to move mucus) and in the oviduct (to move eggs). Flagella: Typically longer and fewer in number (often a single flagellum per cell). Provide motility in sperm cells via a whip-like motion. 45\. Primary Cilium Function: A single, nonmotile projection found on many animal cells that functions as a sensory organelle (e.g., detecting fluid flow in kidney cells). 46\. Dynein and Ciliary Movement: Dynein motor proteins hydrolyze ATP to generate force, causing adjacent microtubules to slide past each other, which produces the bending motion of cilia. 47\. Microfilament-Driven Movements (Examples): Cytokinesis: Actin-myosin ring contraction during cell division. Muscle Contraction: Interaction of actin with myosin filaments. Cell Motility: Formation of structures such as lamellipodia and filopodia. 48\. Motor Proteins for Microfilaments: Myosins facilitate movement along actin filaments. 49\. Functions of Intermediate Filaments: Provide mechanical strength to cells, maintaining cell shape and stabilizing organelle positions. Concept 6.7: Extracellular components and connections between cells help coordinate cellular activities 50\. Functions of the Cell Wall: Provides structural support and protection. Determines cell shape. Prevents excessive water uptake (in plants). 51\. Composition of the Cell Wall: In plants, it is mainly composed of cellulose (in bacteria, the wall is typically made of peptidoglycan). 52\. Primary Cell Wall: A relatively thin and flexible wall secreted by plant cells during growth. 53\. Middle Lamella: A pectin-rich layer that cements adjacent plant cells together, found between the primary cell walls. 54\. Deposition of the Secondary Cell Wall: After cell growth, some plant cells lay down a thick, rigid secondary cell wall (often containing lignin) interior to the primary wall to provide extra support. 55\. Labeled Plant Cell Diagram (Key Structures): Primary Cell Wall: Outermost layer (flexible). Secondary Cell Wall: Thicker layer in some cells (providing rigidity). Middle Lamella: Pectin-rich substance between cells. Cytosol: The fluid inside the cell. Plasma Membrane: Immediately inside the cell wall. Central Vacuole: Large storage and turgor-maintaining compartment. Plasmodesmata: Channels between plant cells for communication. 56\. Extracellular Matrix (ECM) in Animal Cells: Comprised of proteins (e.g., collagen, elastin) and glycoproteins (e.g., fibronectin, laminin). Provides structural support, facilitates cell adhesion, and enables intercellular communication. Also includes extracellular fluid in the space outside cells. 57\. Intercellular Junctions in Plant Cells: Plasmodesmata: Channels that traverse cell walls, allowing molecules and ions to pass between plant cells. 58\. Intercellular Junctions in Animal Cells: **Junction Type** **Description and Role** ------------------- ------------------------------------------------------------------------------------------ Tight Junctions Seal adjacent cells to prevent leakage of extracellular fluid. Desmosomes Provide strong adhesion between cells, anchoring intermediate filaments. Gap Junctions Allow direct communication by permitting ions and small molecules to pass between cells. 59\. Figure 6.32 (Molecular Machinery) -- Sample Answers: Q1: What is the primary function of the cytoskeleton? A: It maintains cell shape, organizes intracellular components, and facilitates cellular movement. Q2: How do membrane proteins contribute to cell communication? A: They serve as receptors for external signals, initiating intracellular signal transduction pathways. Q3: How does compartmentalization benefit the cell? A: It localizes and concentrates metabolic processes, protects the cell from potentially harmful reactions, and increases overall efficiency. DSM: Observing a fluorescent micrograph cell with intermediate filaments would help you identify the cell as a \_\_\_\_\_\_. Human skin cell Cells are small because\_\_\_\_\_. of the geometric relationships between surface and volume Which of the following is present in a prokaryotic cell? Ribosomes Cell motility, which includes changes both in cell location and in the movement of cell parts, requires interactions of the cytoskeleton \_\_\_\_\_\_\_\_\_. with motor proteins Animal cells have unique organelles called \_\_\_\_\_\_\_ that are composed of structures called\_\_\_\_\_\_. centrosomes; centrioles Which of the following is false in respect to cells\' chromosomes? Chromosomes are only visible as a cell is about to divide. Microfilaments function in cell motility including \_\_\_\_\_\_. muscle contraction, amoeboid movement, and cytoplasmic streaming in plants The network of fibers that organizes structures and activities in a cell \_\_\_\_\_. Is the cytoskeleton Evidence that supports the prokaryotic origins of mitochondria and chloroplasts are all of the following except \_\_\_\_\_\_. that mitochondria and chloroplasts have multiple copies of linear DNA molecules associated with their inner membranes The organelle that is a plant cell\'s compartment for the storage of inorganic ions such as potassium and chloride is the \_\_\_\_\_. Central vacuole Cilia and flagella move due to the interaction of the cytoskeleton with which of the following? Motor proteins Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why? The intestinal cells are bound together by tight junctions. In terms of cellular function, what is the most important difference between prokaryotic and eukaryotic cells? Eukaryotic cells are compartmentalized, which allows for specialization. The extracellular matrix of the animal cell has all of the following molecular components except \_\_\_\_\_\_\_\_\_\_. A Middle lamella Bacterial cells are prokaryotic. Unlike a typical eukaryotic cell they\_\_\_\_\_\_\_\_. have no membrane-bounded organelles in their cytoplasm You would expect a cell with an extensive Golgi apparatus to \_\_\_\_\_\_\_. secrete a lot of protein Which statement about the cytoskeleton is true? Components of the cytoskeleton often mediate the movement of organelles within the cytoplasm. \_\_\_\_\_\_\_ are membrane-bound metabolic compartments that specialize in the production of hydrogen peroxide (H2O2) and its conversion to water. Peroxisomes The walls of plant cells are largely composed of polysaccharides and proteins that are synthesized \_\_\_\_\_\_\_. in the rough endoplasmic reticulum and in the Golgi apparatus Which of the following groups is primarily involved in synthesizing molecules needed by the cell? Ribosomes, rough endoplasmic reticulum, and smooth endoplasmic reticulum Dye injected into a plant cell might be able to enter an adjacent cell through \_\_\_\_\_. Plasmodesmata What is the functional connection between the nucleolus, nuclear pores, and the nuclear membrane? Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores. A substance moving from outside the cell into the cytoplasm must pass through\_\_\_\_\_\_\_. The plasma membrane The endosymbiont theory explains the origins of \_\_\_\_\_\_\_. mitochondria and chloroplasts The endoplasmic reticulum is part of the endomembrane system, which also includes the \_\_\_\_\_\_. nuclear envelope, the Golgi apparatus, lysosomes, and vesicles Cell junctions in plant cells are called \_\_\_\_\_\_\_, and communicating junctions in animal cells are called \_\_\_\_\_\_\_\_. plasmodesmata; gap junctions The region of a bacterial cell that contains the genetic material is called the \_\_\_\_\_\_\_. Nucleoid The function of the rough endoplasmic reticulum (RER) is \_\_\_\_\_\_. to synthesize proteins that are secreted as glycoproteins Basal bodies are most closely associated with which of the following cell components? Cilia A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized\_\_\_\_\_\_. in the rough endoplasmic reticulum 1. Which structure is part of the endomembrane system? A. Mitochondrion B. Golgi apparatus (correct) C. Chloroplast D. Centrosome 2. Which structure is common to plant and animal cells? A. Chloroplast B. Central vacuole C. Mitochondrion (correct) D. Centriole 3. Which of the following is present in a prokaryotic cell? A. Mitochondrion B. Ribosome (correct) C. Nuclear envelope D. Chloroplast 4. Cyanide binds to at least one molecule involved in producing ATP. In a cell exposed to cyanide, most of the cyanide will be in A. Mitochondria (correct) B. Ribosomes C. Peroxisomes D. Lysosomes 5. Which would be the best for studying lysosomes? A. Muscle cell B. Never cell C. Bacterial cell D. Phagocytic white blood cell (correct)