Campbell Biology 6, A Tour of the Cell
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Questions and Answers

What is the primary function of a light microscope?

To magnify images by passing visible light through a specimen and glass lenses.

How does the resolution of an electron microscope compare to that of a light microscope?

Electron microscopes have significantly higher resolution due to shorter wavelengths of electrons compared to visible light.

What is the purpose of using heavy metal atoms in Transmission Electron Microscopy (TEM)?

They enhance the density of electrons in certain parts of the cell, improving contrast and detail in imaging.

What is one major disadvantage of using electron microscopes?

<p>Specimens must be dead for preparation, which may introduce artifacts and limits the study of living cells.</p> Signup and view all the answers

Describe the functionality of a Scanning Electron Microscope (SEM).

<p>SEM scans the surface of a sample with an electron beam to create detailed topographical images.</p> Signup and view all the answers

What technique avoids the use of preservatives and allows for viewing specimens in their natural state?

<p>Cryo-Electron Microscopy (Cryo-EM) utilizes low temperatures to preserve the cellular environment.</p> Signup and view all the answers

What is the definition of magnification in microscopy?

<p>Magnification is the ratio of an object's size to its real size.</p> Signup and view all the answers

What is cell fractionation?

<p>Cell fractionation is the process used to separate organelles and subcellular structures from one another.</p> Signup and view all the answers

Why do cells tend to be narrow and elongated rather than cube-shaped?

<p>Cells tend to be narrow and elongated to increase the surface area relative to volume, allowing for more efficient absorption of nutrients and communication.</p> Signup and view all the answers

Explain the difference between prokaryotic and eukaryotic cells regarding DNA organization.

<p>In prokaryotic cells, DNA is concentrated in a non-membrane enclosed region called the nucleoid, whereas eukaryotic cells have DNA enclosed within a double membrane-bound nucleus.</p> Signup and view all the answers

What role do microvilli serve in cells?

<p>Microvilli serve to increase the surface area of cells without significantly increasing their volume, enhancing absorption and secretion processes.</p> Signup and view all the answers

Why is the size of a cell significant for metabolism?

<p>The size of a cell is significant for metabolism because it sets limits on the efficiency of substance exchange and metabolic processes due to the surface area to volume ratio.</p> Signup and view all the answers

What is the function of organelle membranes within eukaryotic cells?

<p>Organelle membranes divide the cell into compartments that provide distinct environments necessary for specific metabolic processes.</p> Signup and view all the answers

How do enzymes embedded in cell membranes assist cellular functions?

<p>Enzymes embedded in cell and organelle membranes facilitate and regulate specific biochemical reactions necessary for cellular processes.</p> Signup and view all the answers

Discuss the significance of the plasma membrane in a cell.

<p>The plasma membrane is vital as it regulates the entry and exit of substances, thus maintaining homeostasis and allowing communication with the external environment.</p> Signup and view all the answers

Why are larger organisms composed of more cells rather than larger cells?

<p>Larger organisms consist of more cells instead of larger cells to maintain a favorable surface area to volume ratio for efficient nutrient exchange and communication.</p> Signup and view all the answers

What is the relationship between cell size and surface area to volume ratio?

<p>As cell size increases, the surface area increases at a slower rate than the volume, leading to a decreased surface area to volume ratio.</p> Signup and view all the answers

Define mycoplasma in the context of cell size.

<p>Mycoplasma are the smallest bacteria cells, ranging in diameter from 0.1 to 1.0 µm, representing the lower limit of cell sizes.</p> Signup and view all the answers

What is the primary role of ribosomes in the cell?

<p>Ribosomes translate mRNA's genetic message into polypeptides, serving as the factories for protein synthesis.</p> Signup and view all the answers

Differentiate between free and bound ribosomes.

<p>Free ribosomes synthesize proteins that function within the cytoplasm, while bound ribosomes create proteins to be inserted into membranes.</p> Signup and view all the answers

What is the endomembrane system, and what is its function?

<p>The endomembrane system includes structures like the nuclear envelope, ER, and Golgi apparatus, and it is involved in protein synthesis, transport, and detoxification.</p> Signup and view all the answers

Describe the difference between smooth ER and rough ER.

<p>Rough ER is studded with ribosomes and is involved in protein synthesis, while smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.</p> Signup and view all the answers

How does the smooth ER contribute to muscle cell contraction?

<p>The smooth ER stores calcium ions, which, when released into the cytosol, trigger muscle contractions.</p> Signup and view all the answers

What role do enzymes in the smooth ER play regarding drug metabolism?

<p>Enzymes in the smooth ER detoxify drugs by attaching a hydroxyl group to make them more water soluble for excretion.</p> Signup and view all the answers

Explain the process of glycoprotein synthesis in the ER.

<p>Glycoproteins are formed in the ER when carbohydrates are covalently bonded to proteins by enzymes in the ER membrane.</p> Signup and view all the answers

What happens to a polypeptide once it is synthesized by the rough ER?

<p>The polypeptide is threaded into the ER lumen through a pore and folds into its functional shape as it enters.</p> Signup and view all the answers

How does the structure of ribosomes aid in their function?

<p>Ribosomes are composed of larger and smaller subunits made of rRNA and proteins, which facilitate the translation of mRNA into proteins.</p> Signup and view all the answers

Identify one key function of vesicles in the endomembrane system.

<p>Vesicles transport molecules between different membranes in the endomembrane system.</p> Signup and view all the answers

Why do cells tend to have a higher surface area to volume ratio as they decrease in size?

<p>Smaller cells have a greater surface area relative to their volume, which facilitates efficient nutrient absorption and waste removal.</p> Signup and view all the answers

What structural features of microvilli contribute to a cell's surface area?

<p>Microvilli are long, narrow projections that increase the surface area without significantly enlarging the cell volume.</p> Signup and view all the answers

How does the nuclear envelope contribute to cellular organization?

<p>The nuclear envelope encloses the nucleus, separating it from the cytoplasm and regulating the entry and exit of materials.</p> Signup and view all the answers

What role does the pore complex play within the nuclear envelope?

<p>The pore complex regulates the transport of molecules, including mRNA, in and out of the nucleus.</p> Signup and view all the answers

Describe the function of histones in the context of DNA organization.

<p>Histones are basic proteins that assist in folding and packing DNA into compact structures known as chromosomes.</p> Signup and view all the answers

What is the role of chromatin when a cell is not dividing?

<p>When not dividing, chromatin appears as a diffuse mass and allows for the accessibility of genetic information.</p> Signup and view all the answers

Explain how the nucleolus is involved in ribosome production.

<p>The nucleolus synthesizes ribosomal RNA (rRNA) and assembles it with proteins to form ribosomal subunits.</p> Signup and view all the answers

What distinguishes free ribosomes from bound ribosomes?

<p>Free ribosomes are suspended in the cytoplasm, while bound ribosomes are attached to the endoplasmic reticulum or nuclear envelope.</p> Signup and view all the answers

How does the nuclear matrix contribute to nuclear function?

<p>The nuclear matrix provides structural support and helps regulate genetic material within the nucleus.</p> Signup and view all the answers

Why do eukaryotic cells contain internal membranes?

<p>Internal membranes compartmentalize the cell, creating distinct environments for various organelle processes.</p> Signup and view all the answers

In what ways does the structure of biological membranes support their function?

<p>Biological membranes are composed of phospholipids and proteins, which facilitate selective permeability and cellular communication.</p> Signup and view all the answers

What is the significance of the nuclear lamina in cell structure?

<p>The nuclear lamina provides mechanical support to the nucleus and helps maintain its shape.</p> Signup and view all the answers

How do larger organisms manage their cellular needs?

<p>Larger organisms do not have larger cells; instead, they have a greater number of smaller cells to manage cellular functions.</p> Signup and view all the answers

What happens to chromosomes as a cell prepares for division?

<p>As a cell prepares to divide, chromosomes condense and become thick enough to be distinguished under a microscope.</p> Signup and view all the answers

What is the process of separating cellular components using centrifuges called?

<p>Differential centrifugation.</p> Signup and view all the answers

What is one main advantage of electron microscopy over light microscopy?

<p>Electron microscopy has significantly higher resolution.</p> Signup and view all the answers

Describe the primary function of a Scanning Electron Microscope (SEM).

<p>SEM is used to view the topography of a sample.</p> Signup and view all the answers

What role do vacuoles play in the function of plant cells?

<p>Vacuoles in plant cells store inorganic ions, maintain cell pressure, and can contain pigments and poisonous substances to aid in growth and protection.</p> Signup and view all the answers

What limits the size of a cell with regards to metabolism?

<p>The logistics of carrying out metabolism set limits on cell size.</p> Signup and view all the answers

How does the contractile vacuole function in protists?

<p>The contractile vacuole pumps excess water outside the cell to maintain osmotic balance.</p> Signup and view all the answers

What are the main features all cells share?

<p>All cells have a plasma membrane, cytosol, chromosomes, and ribosomes.</p> Signup and view all the answers

What distinguishes Rough ER from Smooth ER?

<p>Rough ER is covered in ribosomes which are involved in protein synthesis, while Smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.</p> Signup and view all the answers

How does the magnification of an object relate to its real size?

<p>Magnification is the ratio of an object's size to its real size.</p> Signup and view all the answers

What is the primary difference between prokaryotic and eukaryotic cells in terms of DNA location?

<p>In eukaryotic cells, DNA is located in a membrane-bound nucleus.</p> Signup and view all the answers

Explain the purpose of lysosomal digestion in relation to food vacuoles.

<p>Food vacuoles are formed by phagocytosis and fuse with lysosomes, where enzymes digest the ingested food.</p> Signup and view all the answers

What is the function of glycoproteins produced in the Rough ER?

<p>Glycoproteins serve various functions including cell-to-cell recognition, signaling, and forming part of the extracellular matrix.</p> Signup and view all the answers

Why do electron microscopes often require specimens to be prepared post-mortem?

<p>Samples must be fixed and often stained to visualize structures.</p> Signup and view all the answers

How do vacuoles contribute to plant protection?

<p>Vacuoles can contain poisonous substances that deter herbivores from eating the plant.</p> Signup and view all the answers

What are cryo-electron microscopes (Cryo-EM) used for?

<p>Cryo-EM allows examination of specimens at low temperatures.</p> Signup and view all the answers

What is the role of the central vacuole in mature plant cells?

<p>The central vacuole stores cell sap, which includes inorganic ions, and aids in maintaining turgor pressure for cell rigidity.</p> Signup and view all the answers

What role does the plasma membrane play in a cell?

<p>The plasma membrane regulates what enters and exits the cell.</p> Signup and view all the answers

How does the surface area of a cell relate to its volume as it increases in size?

<p>Surface area increases proportionally less than volume.</p> Signup and view all the answers

Describe how the endomembrane system is interconnected.

<p>The endomembrane system components are connected through physical contact or the transfer of membrane segments via vesicles.</p> Signup and view all the answers

What is the role of ribosomes within cells?

<p>Ribosomes are responsible for protein synthesis.</p> Signup and view all the answers

What metabolic processes are associated with Smooth ER?

<p>Smooth ER is involved in lipid synthesis, carbohydrate metabolism, detoxification of drugs, and storage of calcium ions.</p> Signup and view all the answers

How does the smooth ER contribute to drug detoxification?

<p>The smooth ER contains enzymes that modify drugs by adding hydroxyl groups, making them more water-soluble and easier to excrete.</p> Signup and view all the answers

What comprises the cytoplasm in eukaryotic cells?

<p>Cytoplasm includes the area between the nucleus and plasma membrane and contains membrane-bound organelles.</p> Signup and view all the answers

Identify the smallest known bacteria and their size range.

<p>Mycoplasma are the smallest bacteria, measuring 0.1 to 1.0 µm in diameter.</p> Signup and view all the answers

What is the significance of a cell's ability to modify membrane composition?

<p>Modifying membrane composition allows the cell to adapt its functions and interactions with its environment as it develops.</p> Signup and view all the answers

What is the significance of contrast in microscopy?

<p>Contrast is the difference between light and dark regions of an image.</p> Signup and view all the answers

In what way do vacuoles assist in attracting pollinators?

<p>Some plant vacuoles contain pigments that change color to attract pollinating insects.</p> Signup and view all the answers

Explain the effect of barbiturates on smooth ER proliferation.

<p>Barbiturates induce the proliferation of smooth ER, increasing the number of detoxifying enzymes and necessitating higher doses for the same effect.</p> Signup and view all the answers

Define the role of the ER lumen.

<p>The ER lumen is the enclosed space within the endoplasmic reticulum where proteins and lipids are processed and modified.</p> Signup and view all the answers

What role do transport vesicles play after proteins leave the ER?

<p>Transport vesicles carry secreted proteins from the ER to the Golgi apparatus for further processing.</p> Signup and view all the answers

How does the rough ER contribute to the formation of membrane proteins?

<p>The rough ER inserts polypeptides destined for membranes directly into its own membrane as they are synthesized.</p> Signup and view all the answers

What is the purpose of the Golgi Apparatus in a cell?

<p>The Golgi Apparatus serves as a warehouse for receiving, processing, and shipping materials within the cell.</p> Signup and view all the answers

Describe the structural directionality of the Golgi apparatus.

<p>The Golgi apparatus has a cis stack located near the ER and a trans stack that packages materials for transport, differing in thickness and molecular composition.</p> Signup and view all the answers

What modifications can occur to glycoproteins in the Golgi apparatus?

<p>Glycoproteins can have some sugar monomers removed and replaced with others as they are modified in the Golgi apparatus.</p> Signup and view all the answers

Explain how lysosomes prevent self-digestion.

<p>Lysosomes prevent self-digestion by having hydrolytic enzymes contained within a membrane and maintaining an acidic internal environment.</p> Signup and view all the answers

What process do lysosomes use to digest macromolecules?

<p>Lysosomes digest macromolecules through hydrolysis, using hydrolytic enzymes to break down materials.</p> Signup and view all the answers

What is autophagy, and why is it important?

<p>Autophagy is the process where lysosomes break down damaged organelles for recycling, allowing cells to renew and maintain themselves.</p> Signup and view all the answers

How do inherited lysosomal storage diseases affect cell functionality?

<p>Inherited lysosomal storage diseases impair the function of hydrolytic enzymes, leading to a buildup of undigested material in lysosomes.</p> Signup and view all the answers

What is the significance of molecular identification tags in the Golgi apparatus?

<p>Molecular identification tags, such as phosphate groups, help sort materials to their correct destinations within the cell.</p> Signup and view all the answers

What occurs during phagocytosis in macrophages?

<p>During phagocytosis, macrophages engulf bacteria and fuse the resulting food vacuole with lysosomes to digest the bacteria.</p> Signup and view all the answers

How does the Golgi apparatus modify polysaccharides?

<p>The Golgi apparatus manufactures and modifies polysaccharides, including pectins, which are incorporated into plant cell walls.</p> Signup and view all the answers

What process occurs when a transport vesicle exits the trans face of the Golgi?

<p>When a transport vesicle exits the trans face, it carries products that can be incorporated into the plasma membrane or sent to other destinations.</p> Signup and view all the answers

What is the role of the transitional ER in the transport of secretory proteins?

<p>The transitional ER is responsible for packaging secretory proteins into vesicles for transport to the Golgi apparatus.</p> Signup and view all the answers

How does the Golgi apparatus differ structurally from the endoplasmic reticulum?

<p>The Golgi apparatus is made up of flattened membrane sacs called cisternae, whereas the endoplasmic reticulum consists of a network of membranes.</p> Signup and view all the answers

Explain the cisternal maturation model in relation to the Golgi apparatus.

<p>The cisternal maturation model suggests that the cisternae of the Golgi move and mature as they process proteins, transforming from cis to trans.</p> Signup and view all the answers

What mechanisms prevent lysosomes from self-digesting?

<p>Lysosomal enzymes are kept inactive in a neutral pH environment outside the lysosome and are protected by the three-dimensional structure of their proteins.</p> Signup and view all the answers

Define phagocytosis and its significance in the immune system.

<p>Phagocytosis is the process where cells engulf and digest foreign particles, like bacteria, using lysosomes to degrade them.</p> Signup and view all the answers

What is the primary function of lysosomes in eukaryotic cells?

<p>Lysosomes are responsible for hydrolyzing macromolecules and recycling cellular components.</p> Signup and view all the answers

Describe the process by which transport vesicles merge with the Golgi membrane.

<p>Transport vesicles carrying materials from the ER can merge with the cis face of the Golgi apparatus, allowing for the transfer of cargo.</p> Signup and view all the answers

What changes occur to glycoproteins as they move through the Golgi apparatus?

<p>As glycoproteins transit through the Golgi, they undergo modifications, which can include the removal and replacement of sugar monomers.</p> Signup and view all the answers

How does autophagy contribute to cellular homeostasis?

<p>Autophagy allows the cell to recycle damaged organelles and maintain a balance of cellular components by surrounding them with membranes and degrading them in lysosomes.</p> Signup and view all the answers

What is the main difference between the plus end and the minus end of microtubules?

<p>The plus end accumulates and releases tubulins at a higher rate, allowing for faster growth or shrinkage compared to the minus end.</p> Signup and view all the answers

What role do molecular identification tags play in the Golgi apparatus?

<p>Molecular identification tags, such as phosphate groups, help sort materials and direct transport vesicles to their appropriate destinations.</p> Signup and view all the answers

Describe the structure and function of centrioles within the centrosome.

<p>Centrioles are composed of triplet microtubules arranged in a ring, and they play a key role in organizing microtubules during cell division.</p> Signup and view all the answers

What is the importance of lysosomal enzymes functioning best in acidic environments?

<p>Lysosomal enzymes are optimized to work in the acidic environment of lysosomes, enabling effective digestion of macromolecules.</p> Signup and view all the answers

How do dyneins contribute to the movement of cilia and flagella?

<p>Dyneins are motor proteins that create movement by 'walking' along microtubules, causing bending of cilia and flagella.</p> Signup and view all the answers

What pattern of microtubule arrangement is found in most eukaryotic flagella and motile cilia?

<p>The 9+2 pattern, consisting of nine doublets of microtubules surrounding two central microtubules.</p> Signup and view all the answers

Explain how inherited lysosomal storage diseases affect cellular function.

<p>Inherited lysosomal storage diseases result from the impairment of hydrolytic enzymes, leading to the accumulation of undigested materials in lysosomes.</p> Signup and view all the answers

Describe the composition and function of vacuoles in cells.

<p>Vacuoles are large vesicles derived from the ER and Golgi apparatus that store various substances and help maintain turgor pressure in cells.</p> Signup and view all the answers

Explain the primary role of microfilaments in muscle contraction.

<p>Microfilaments, composed of actin, interact with myosin to facilitate muscle contraction through sliding filament mechanisms.</p> Signup and view all the answers

How do intermediate filaments differ from microfilaments in terms of stability?

<p>Intermediate filaments are generally more permanent and do not disassemble easily, providing persistent structural support.</p> Signup and view all the answers

What role does the basal body play in the structure of cilia and flagella?

<p>The basal body anchors the microtubule assembly of cilia and flagella and is structured similarly to a centriole.</p> Signup and view all the answers

Describe the composition and function of plant cell walls.

<p>Plant cell walls are primarily made of cellulose microfibrils and provide structure, protection, and prevent excessive water intake.</p> Signup and view all the answers

What is the significance of the primary cell wall in young plant cells?

<p>The primary cell wall is relatively thin and flexible, allowing for cell growth and expansion in young plant cells.</p> Signup and view all the answers

What is cytoplasmic streaming, and why is it important in plant cells?

<p>Cytoplasmic streaming is the circular flow of cytoplasm that enhances the movement of organelles and materials within plant cells.</p> Signup and view all the answers

How do cilia function as sensory receptors in cells?

<p>Cilia act as signal-receiving antennas, transmitting molecular signals from the environment to the cell's interior.</p> Signup and view all the answers

Explain the role of the middle lamella in plant cells.

<p>The middle lamella is a layer rich in pectin that glues adjacent plant cells together, providing structural cohesion.</p> Signup and view all the answers

What is the relationship between microtubules and organelle movement?

<p>Microtubules form pathways along which motor proteins transport organelles, facilitating their movement within the cell.</p> Signup and view all the answers

What is the main function of the contractile vacuole in unicellular protists?

<p>The contractile vacuole pumps excess water outside of the cell.</p> Signup and view all the answers

How do vacuoles in plants contribute to protection against herbivores?

<p>Plant vacuoles can contain poisonous substances that deter herbivores.</p> Signup and view all the answers

Describe the relationship between mitochondria and cellular respiration.

<p>Mitochondria are the sites of cellular respiration where glucose and oxygen are converted into ATP.</p> Signup and view all the answers

What is the significance of the Endosymbiont Theory?

<p>It explains the origin of mitochondria and chloroplasts as derived from engulfed prokaryotic cells.</p> Signup and view all the answers

What structural feature of mitochondria increases their productivity in ATP production?

<p>The highly folded inner membrane, known as cristae, increases the surface area.</p> Signup and view all the answers

What role do thylakoids play in chloroplasts?

<p>Thylakoids are the sites where the light-dependent reactions of photosynthesis occur.</p> Signup and view all the answers

How do peroxisomes contribute to cellular detoxification?

<p>Peroxisomes transfer hydrogen from various substances into oxygen, forming hydrogen peroxide, which is then detoxified.</p> Signup and view all the answers

What is the function of the central vacuole in mature plant cells?

<p>The central vacuole stores cell sap, which contains inorganic ions and supports cell growth by absorbing water.</p> Signup and view all the answers

What are chromoplasts and their role in plants?

<p>Chromoplasts are pigment-containing organelles that provide yellowish-orange colors to fruits and flowers.</p> Signup and view all the answers

Explain the difference between amyloplasts and chromoplasts.

<p>Amyloplasts store starch, while chromoplasts contain pigments for coloration.</p> Signup and view all the answers

What two compartments are formed by the inner membrane of mitochondria?

<p>The inner membrane divides the mitochondria into the intermembrane space and the mitochondrial matrix.</p> Signup and view all the answers

Why are chloroplasts considered mobile within plant cells?

<p>Chloroplasts can grow, shrink, and reproduce by pinching in two.</p> Signup and view all the answers

What enzymes are found in the mitochondrial matrix, and what is their purpose?

<p>The mitochondrial matrix contains enzymes that catalyze steps of cellular respiration.</p> Signup and view all the answers

What role do centrosomes play in eukaryotic cells?

<p>Centrosomes organize microtubules for the cytoskeleton and anchor a pair of centrioles.</p> Signup and view all the answers

How are cilia and flagella structurally similar?

<p>Both cilia and flagella consist of microtubules arranged in a specific pattern, typically a 9+2 structure.</p> Signup and view all the answers

What is the function of dyneins in cilia and flagella?

<p>Dyneins are motor proteins that facilitate the bending and movement of cilia and flagella.</p> Signup and view all the answers

Describe the difference between nonmotile and motile cilia.

<p>Motile cilia can move and propel substances, while nonmotile cilia typically function as signal-receiving antennas.</p> Signup and view all the answers

What is the 9+0 pattern associated with?

<p>The 9+0 pattern is associated with nonmotile cilia, lacking central microtubules.</p> Signup and view all the answers

What is the primary role of microfilaments in cells?

<p>Microfilaments provide structural support and participate in cell movements.</p> Signup and view all the answers

Explain how the cortex contributes to cell shape.

<p>The cortex is a three-dimensional network of microfilaments that supports and shapes the cell's outer layer.</p> Signup and view all the answers

How do intermediate filaments differ from microfilaments?

<p>Intermediate filaments have larger diameters and provide more permanent structural support compared to microfilaments.</p> Signup and view all the answers

What is cytoplasmic streaming and its significance in plant cells?

<p>Cytoplasmic streaming is the circular flow of cytoplasm that aids in the movement of organelles and materials within plant cells.</p> Signup and view all the answers

What structural arrangement characterizes the basal body?

<p>The basal body has microtubule triplets arranged in a 9+0 pattern.</p> Signup and view all the answers

How do vesicles utilize the cytoskeleton for movement?

<p>Vesicles move along the cytoskeleton using motor proteins that facilitate their transport to specific destinations.</p> Signup and view all the answers

What provides the tension-bearing support in the cytoskeleton?

<p>Microfilaments and intermediate filaments provide tension-bearing support within the cytoskeleton.</p> Signup and view all the answers

How do microtubules contribute to the cell's structure?

<p>Microtubules are hollow rods that resist compression and provide overall structural support to the cell.</p> Signup and view all the answers

Explain the role of the cytoskeleton in cells that lack cell walls.

<p>In cells without cell walls, the cytoskeleton provides shape, support, and facilitates movement.</p> Signup and view all the answers

What role do integrins play in the interaction between cells and the extracellular matrix (ECM)?

<p>Integrins are receptor proteins that span the plasma membrane and facilitate communication between the cytoskeleton and the ECM, influencing cell behavior.</p> Signup and view all the answers

Explain how plasmodesmata function in plant cells.

<p>Plasmodesmata are channels connecting plant cells that allow the passage of water, solutes, proteins, and RNA, ensuring they maintain similar environmental properties.</p> Signup and view all the answers

Describe the structure and function of tight junctions in animal cells.

<p>Tight junctions consist of closely packed plasma membranes that prevent leakage of fluids between cells, thus maintaining barrier integrity.</p> Signup and view all the answers

What are the main components and purpose of desmosomes?

<p>Desmosomes are anchoring junctions that fasten cells into sheets using intermediate filaments, providing strength and stability to tissues.</p> Signup and view all the answers

How does the extracellular matrix (ECM) influence gene activity in cells?

<p>The ECM regulates gene activity by communicating through integrins and other ECM proteins that transmit signals to the cell's nucleus.</p> Signup and view all the answers

What is a gap junction and what is its significance in cell communication?

<p>Gap junctions are protein channels that create cytoplasmic connections between animal cells, allowing ions and small molecules to pass directly between them.</p> Signup and view all the answers

Why might large proteoglycan complexes be crucial for the ECM?

<p>Large proteoglycan complexes provide structural support and regulate the movement of molecules through the ECM, influencing tissue hydration and resilience.</p> Signup and view all the answers

What is the significance of the cytoplasmic side of integrins in cellular communication?

<p>The cytoplasmic side of integrins binds to microfilaments, which helps transmit signals from the ECM to the cytoskeleton, impacting cell behavior and responses.</p> Signup and view all the answers

What are the two primary functions of mitochondria in eukaryotic cells?

<p>Mitochondria are responsible for cellular respiration and ATP production using oxygen and glucose.</p> Signup and view all the answers

How does the Endosymbiont Theory explain the presence of mitochondria and chloroplasts in eukaryotic cells?

<p>The theory suggests that an early ancestor of eukaryotic cells engulfed prokaryotic cells, leading to the formation of mitochondria and chloroplasts.</p> Signup and view all the answers

What structural feature differentiates mitochondria and chloroplasts from many other organelles?

<p>Both mitochondria and chloroplasts have a double membrane structure.</p> Signup and view all the answers

What is the significance of cristae in the mitochondria?

<p>Cristae increase the surface area of the inner membrane, enhancing ATP production.</p> Signup and view all the answers

What are thylakoids, and what role do they play in chloroplasts?

<p>Thylakoids are stacked, interconnected sacs that house the chlorophyll pigments for photosynthesis.</p> Signup and view all the answers

Explain the function of peroxisomes in plant and animal cells.

<p>Peroxisomes contain enzymes that convert hydrogen peroxide into water and are involved in the breakdown of fatty acids.</p> Signup and view all the answers

What is the primary purpose of the cytoskeleton in eukaryotic cells?

<p>The cytoskeleton provides structural support and shape to the cell and facilitates movement within it.</p> Signup and view all the answers

What are the three main types of fibers in the cytoskeleton?

<p>Microtubules, microfilaments, and intermediate filaments.</p> Signup and view all the answers

How do microtubules contribute to cell division?

<p>Microtubules assist in the separation of chromosomes during cell division.</p> Signup and view all the answers

What compartments are created by the chloroplast membrane, and why is this organization important?

<p>The chloroplast membrane creates the intermembrane space, stroma, and thylakoid space, optimizing energy conversion during photosynthesis.</p> Signup and view all the answers

What is the role of amyloplasts and chromoplasts in plant cells?

<p>Amyloplasts store starch, while chromoplasts provide pigments that give color to fruits and flowers.</p> Signup and view all the answers

How do the shapes of mitochondria and chloroplasts differ from many other cell organelles?

<p>Mitochondria and chloroplasts have dynamic shapes; they can grow, shrink, and reproduce themselves.</p> Signup and view all the answers

In terms of metabolic activity, why do muscle cells contain more mitochondria than other cell types?

<p>Muscle cells require more energy for contraction and movement, hence they have a higher number of mitochondria.</p> Signup and view all the answers

What is the main function of the secondary cell wall in plants?

<p>The secondary cell wall provides additional reinforcement and strength to the plant cell, primarily found in wood.</p> Signup and view all the answers

Describe the role of collagen in the extracellular matrix (ECM).

<p>Collagen forms strong fibers in the ECM and accounts for about 40% of the protein in the human body.</p> Signup and view all the answers

What is a proteoglycan network and its significance?

<p>The proteoglycan network consists of collagen fibers embedded in proteoglycans bonded to polysaccharides, providing structural integrity to the ECM.</p> Signup and view all the answers

Explain the function of integrins in relation to the ECM.

<p>Integrins are receptor proteins that facilitate communication between the cytoskeleton and the ECM, influencing cell behavior.</p> Signup and view all the answers

What connects plant cells through channels, and what is its function?

<p>Plasmodesmata connect plant cells, allowing water, solutes, and small molecules to pass between them.</p> Signup and view all the answers

Distinguish between the three types of cell junctions found in animal cells.

<p>Tight junctions prevent fluid leakage, desmosomes fasten cells into sheets, and gap junctions create channels for communication.</p> Signup and view all the answers

What is the role of the middle lamella in plant cells?

<p>The middle lamella glues adjacent plant cells together and consists primarily of pectins.</p> Signup and view all the answers

How do cell walls differ between primary and secondary types?

<p>The primary cell wall is thin and flexible, while the secondary cell wall is thicker and more reinforced.</p> Signup and view all the answers

Identify the main components of the extracellular matrix.

<p>The ECM is mainly composed of glycoproteins, proteoglycans, and other carbohydrate-containing molecules.</p> Signup and view all the answers

What role do fibronectin and integrins play in cell attachment?

<p>Fibronectin binds to integrins, which are receptor proteins that anchor cells to the ECM.</p> Signup and view all the answers

Explain the significance of desmosomes in muscle cells.

<p>Desmosomes anchor muscle cells together, preventing them from pulling apart during contraction.</p> Signup and view all the answers

How does the ECM influence gene activity in cells?

<p>The ECM can affect gene activity through signaling pathways facilitated by integrins.</p> Signup and view all the answers

Describe the composition of proteoglycan molecules.

<p>Proteoglycans consist of a small core protein with multiple carbohydrate chains covalently bonded to it.</p> Signup and view all the answers

What distinguishes gap junctions from plasmodesmata in plant cells?

<p>Gap junctions are formed by membrane proteins that create pores for communication, unlike plasmodesmata, which are lined with membrane.</p> Signup and view all the answers

Flashcards

Light Microscope (LM)

Uses visible light to magnify a specimen, passing light through a sample and focusing with lenses.

Magnification

Ratio of an object's image size to its actual size.

Resolution

Clarity of an image; minimum distance between two points still seen as separate.

Electron Microscope (EM)

Uses electrons instead of light to magnify images, offering higher resolution than light microscopes.

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Cell Fractionation

Process of separating cell parts (organelles) from one another.

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Transmission Electron Microscope (TEM)

Study internal cell structures by passing electrons through thin slices of specimens.

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Scanning Electron Microscope (SEM)

Examines the surface of a specimen by scanning it with a beam of electrons to create a 3-D view.

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Cryo-Electron Microscopy (Cryo-EM)

Uses low temperatures to examine cells without preservatives, showing cells in their living state.

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Differential Centrifugation

Separating cell components by spinning a mixture of disrupted cells at varying speeds.

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Centrifuge

A machine used to separate substances of different densities by spinning them.

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Pellet

The solid material that settles at the bottom of a tube during centrifugation.

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Light Microscope

A microscope that uses visible light to magnify images.

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Contrast

The difference in brightness between different parts of a sample.

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Electron Microscope

A microscope that uses a beam of electrons to magnify images.

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Cryo-Electron Microscopy

A method that uses freezing to view specimens in their natural state without preserving them, for better analysis.

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Prokaryotic Cell

A cell lacking a nucleus and membrane-bound organelles.

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Eukaryotic Cell

A cell containing a nucleus and membrane-bound organelles.

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Plasma Membrane

The outer boundary of a cell that controls what enters and exits.

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Surface Area to Volume Ratio

The ratio of a cell's surface area to its volume. A higher ratio means more surface area relative to volume.

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Why are cells small?

Cells need a large surface area to exchange materials (nutrients, waste) with their surroundings. Small cells have a higher surface area to volume ratio, making exchange more efficient.

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Microvilli

Tiny, finger-like projections extending from the cell membrane, increasing surface area without significantly increasing volume.

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Organelle Membranes

Internal membranes within eukaryotic cells that compartmentalize the cell, creating specialized environments for different functions.

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Why are larger organisms not made of larger cells?

Instead of larger individual cells, larger organisms have more cells. This maintains a favorable surface area to volume ratio for efficient exchange.

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Cytoplasm

The jelly-like substance inside a cell, between the nucleus and the plasma membrane.

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Nucleoid

The region in prokaryotic cells where DNA is concentrated, but not enclosed by a membrane.

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Ribosomes

Cellular structures responsible for protein synthesis, composed of rRNA and proteins. They are not membrane-bound, and thus not organelles.

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Free Ribosomes

Ribosomes located in the cytoplasm, responsible for synthesizing proteins that will function within the cytoplasm.

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Bound Ribosomes

Ribosomes attached to the ER or nuclear envelope, involved in producing proteins destined for membranes or export.

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Endomembrane System

Network of membranes that works together to synthesize, modify, package and transport molecules within the cell.

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Vesicles

Small membrane-bound sacs that transport molecules between different parts of the cell.

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Endoplasmic Reticulum (ER)

A network of interconnected membranes that extend throughout the cytoplasm of eukaryotic cells.

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Smooth ER

Lacks ribosomes and is involved in lipid synthesis, carbohydrate metabolism, detoxification, and calcium storage.

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Rough ER

Covered with ribosomes, responsible for synthesizing proteins that will be secreted from the cell or embedded in membranes.

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Glycoproteins

Proteins with carbohydrates covalently attached to them, often involved in cell signaling and recognition.

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ER Lumen

The internal space enclosed by the ER membrane.

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Secretory Protein

A protein destined to be released from the cell.

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Transitional ER

A region of the ER where transport vesicles bud off, carrying secretory proteins to the Golgi apparatus.

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Transport Vesicles

Small, membrane-bound sacs that move materials between compartments.

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Golgi Apparatus

A stack of flattened membrane sacs that modify, sort, and package proteins and lipids.

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Cis Face

The receiving end of the Golgi apparatus, located near the ER.

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Trans Face

The shipping end of the Golgi apparatus, where modified molecules are packaged into vesicles.

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Lysosome

A membrane-bound organelle containing hydrolytic enzymes that digest macromolecules.

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Phagocytosis

The process by which cells engulf large particles or microorganisms.

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Autophagy

A process by which cells break down damaged organelles for recycling.

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Phospholipid Bilayer

The basic structure of biological membranes. Two layers of phospholipid molecules with their hydrophilic heads facing outwards and hydrophobic tails inwards.

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Membrane Proteins

Proteins embedded within the phospholipid bilayer, giving membranes their unique functions. They can act as channels, receptors, enzymes, or anchors.

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Nuclear Envelope

Double membrane surrounding the nucleus, separating it from the cytoplasm. It has pores that allow the passage of molecules between the nucleus and cytoplasm.

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Pore Complex

Intricate structure made of proteins lining each nuclear pore, regulating the transport of substances into and out of the nucleus.

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Nuclear Lamina

Net-like array of protein filaments lining the nuclear envelope (except pores). It provides structural support and helps organize the nucleus.

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Nuclear Matrix

Framework of proteins extending throughout the nuclear interior. It works with the nuclear lamina to regulate genetic material.

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Histones

Basic proteins that bind to DNA and help fold it into compact structures called chromosomes.

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Chromatin

Complex of DNA and its associated proteins, creating the organized structure of chromosomes. It allows for efficient packaging of DNA within the nucleus.

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Vacuole

A large, fluid-filled sac in a cell that stores materials and helps maintain pressure.

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Cisternal Maturation Model

A theory that suggests Golgi cisternae themselves move and mature as they process materials.

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Lysosomal Storage Diseases

Genetic disorders caused by the deficiency of specific lysosomal enzymes, leading to the accumulation of undigested materials.

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Vacuole Function

Vacuoles are membrane-bound sacs within cells that serve various functions, including storage, digestion, and regulation of cell volume.

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Food Vacuole

A food vacuole is formed by phagocytosis, engulfing food particles, and plays a key role in lysosomal digestion.

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Contractile Vacuole

A contractile vacuole, found in some unicellular organisms, pumps excess water out of the cell, maintaining the cell's internal water balance.

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Enzymatic Hydrolysis in Vacuoles

Certain vacuoles in plants and fungi can carry out enzymatic hydrolysis, like lysosomes in animal cells, breaking down molecules using water and enzymes.

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Central Vacuole in Plants

The central vacuole, a large, fluid-filled sac in mature plant cells, is formed by the fusion of smaller vacuoles and plays a crucial role in plant growth and turgor pressure.

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Cell Sap

The fluid inside a central vacuole, called cell sap, contains dissolved inorganic ions, such as potassium and chloride.

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Components of the Endomembrane System

The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, the plasma membrane, and various vesicles and vacuoles.

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Vesicles in the Endomembrane System

Vesicles are small, membrane-bound sacs that transport molecules, secrete substances, digest materials, and regulate pressure within the cell.

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ER Lumen (Cisternal Space)

The ER lumen is the space enclosed by the ER membrane, a separate compartment within the cell.

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Vacuole Selectivity

The vacuole membrane carefully controls which substances enter and leave, resulting in a different chemical environment inside compared to the surrounding cell.

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Food Vacuole Function

Formed by engulfing food particles through phagocytosis, food vacuoles are crucial for lysosomal digestion, breaking down food into usable nutrients.

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Vacuole Hydrolysis

In plants and fungi, vacuoles can break down molecules using enzymes and water (enzymatic hydrolysis), a function shared by lysosomes in animal cells.

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Plant Vacuole Storage

In plants, small vacuoles can store organic compounds like sugars or pigments.

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Plant Vacuole Protection

Plant vacuoles can store poisonous substances, deterring herbivores from eating the plant.

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Plant Vacuole Pigments

Some plant vacuoles contain pigments that attract pollinating insects, helping with plant reproduction.

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Central Vacuole

Large, central vacuole in mature plant cells, formed by merging smaller vacuoles, filled with 'cell sap' - a storage of ions like potassium and chloride.

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Central Vacuole and Growth

The expanding central vacuole as it absorbs water helps plant cells grow larger without needing to produce new cytoplasm.

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Mitochondria Function

Mitochondria are the powerhouses of the cell, responsible for cellular respiration, converting glucose and oxygen into ATP (energy).

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Chloroplast Function

Chloroplasts, found in plants and algae, are responsible for photosynthesis, converting sunlight into chemical energy (sugars).

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Endosymbiont Theory

This theory explains the origin of mitochondria and chloroplasts: early eukaryotic cells engulfed prokaryotic cells, which became integrated as organelles.

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Mitochondria and Chloroplast Similarities

Mitochondria and chloroplasts have similar structures: two membranes, suggesting they were once independent bacteria. They also have their own DNA.

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Mitochondria Autonomy

Mitochondria are semi-independent; they can grow, divide, and have their own ribosomes and DNA.

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Mitochondria and Metabolic Activity

The number of mitochondria in a cell corresponds to its metabolic activity. Cells with high energy demands (like muscle cells) have more mitochondria.

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Mitochondria

Organelles responsible for cellular respiration, converting energy from glucose and oxygen into ATP.

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Chloroplasts

Organelles found in plants and algae that carry out photosynthesis, converting light energy into chemical energy.

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What are the two membranes surrounding mitochondria and chloroplasts?

Both mitochondria and chloroplasts have two membranes, an outer membrane and an inner membrane.

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What does the mitochondrial matrix contain?

The mitochondrial matrix is the space enclosed by the inner mitochondrial membrane and contains enzymes, ribosomes, and mitochondrial DNA.

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What is the function of the cristae in the mitochondria?

The cristae are infoldings of the inner mitochondrial membrane that increase surface area, enhancing the efficiency of cellular respiration.

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What are thylakoids and grana in chloroplasts?

Thylakoids are interconnected sacs within chloroplasts, and grana are stacks of thylakoids.

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What is the stroma of a chloroplast?

The stroma is the fluid outside of the thylakoids in chloroplasts, containing chloroplast DNA, enzymes, and other molecules.

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What are peroxisomes?

Single-membrane bound organelles containing enzymes that break down fatty acids and detoxify harmful substances.

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What is a cytoskeleton?

A network of protein fibers within a cell that provides support, shape, and aids in movement.

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What are the three main types of cytoskeletal fibers?

Microtubules (thickest), microfilaments (thinnest), and intermediate filaments (medium size) are the three main types of cytoskeleton fibers.

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What are microtubules made of?

Microtubules are hollow rods made of proteins called tubulins, specifically alpha and beta tubulin.

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How do microtubules grow and shrink?

Microtubules grow by adding tubulin dimers, and shrink by releasing them.

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What are the roles of microtubules in the cell?

Microtubules function in cell division, organelle transport, and maintaining cell shape.

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What are some examples of plastids?

Plastids are organelles found in plant cells, and some examples include chloroplasts (photosynthesis), amyloplasts (starch storage), and chromoplasts (pigmentation).

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Centrosome

A region near the nucleus of many eukaryotic cells that serves as the microtubule organizing center. It contains a pair of centrioles.

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What do centrosomes and centrioles do?

Centrosomes and centrioles play a crucial role in organizing microtubules, which form the cytoskeleton, participate in cell division, and serve as tracks for intracellular transport.

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Flagella

Long, whip-like appendages that enable eukaryotic cells to move. They are made of microtubules.

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Cilia

Short, hair-like appendages that enable movement in eukaryotic cells. They are also made of microtubules.

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9+2 Pattern

Arrangement of microtubules found in most eukaryotic flagella and motile cilia. It consists of nine doublets of microtubules surrounding two single microtubules in the center.

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Basal Body

A structure that anchors the microtubule assembly of cilia and flagella. It is structured similarly to a centriole but lacks a central pair of microtubules.

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Dynein

Motor protein that causes the movement of flagella and cilia. It is attached to each outer doublet of microtubules and uses ATP to shift its position.

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Microfilament

Solid rod made of actin, a globular protein. They form twisted double chains and can create structural networks.

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Cortex

The gel-like, semisolid outer layer of the cell, formed by the three-dimensional network of microfilaments. It provides support and gives the cell its shape.

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Myosin

Motor protein that interacts with actin filaments (microfilaments) to cause muscle cell contraction.

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Amoeboid Movement

Crawling movement in cells, like amoebas and white blood cells, that is powered by myosin contractions.

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Intermediate Filaments

Cytoskeletal fibers with a larger diameter than microfilaments. They are found in some animals and help bear tension.

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What are the key functions of the cytoskeleton?

The cytoskeleton provides structural support for the cell, helps organize and move organelles, enables cell movement, plays a role in cell division, and helps maintain cell shape.

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Proteoglycan Complex

A large complex formed when hundreds of proteoglycan molecules bind noncovalently to a single polysaccharide.

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Fibronectin

An ECM protein that helps attach cells to the ECM by binding to integrin receptors on the cell surface.

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Integrin

A receptor protein embedded in the cell membrane that binds to ECM proteins like fibronectin.

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ECM's Role in Gene Regulation

The ECM can influence the activity of genes in the nucleus, affecting cell behavior.

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Plasmodesmata

Channels connecting plant cells, allowing the passage of water, solutes, proteins, and RNA.

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Tight Junction

A type of cell junction in animals that prevents fluid leakage between cells.

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Gap Junction

A cell junction similar to plasmodesmata, but made of proteins that form channels for communication between cells.

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Plus End

The end of a microtubule where tubulin subunits are added faster, causing it to grow more rapidly.

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Minus End

The end of a microtubule where tubulin subunits are removed faster, causing it to shrink more rapidly.

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Microtubule Function

Microtubules act as tracks for organelles to move within the cell using motor proteins. They also play a crucial role in separating chromosomes during cell division.

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9+2 Structure

The arrangement of microtubules in most motile cilia and flagella: nine doublets of microtubules surrounding two single microtubules in the center.

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Cytoplasmic Streaming

Circular flow of cytoplasm in plant cells, driven by actin-protein interactions.

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Primary Cell Wall

The first cell wall formed by a young plant cell. It is relatively thin and flexible, allowing the cell to grow and change shape.

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Secondary Cell Wall

A thicker and more rigid layer that forms inside the primary cell wall, providing additional strength and support. Wood is mostly composed of secondary cell walls.

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Middle Lamella

A thin layer of pectin between adjacent plant cell walls that acts like glue, holding the cells together.

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Extracellular Matrix (ECM)

A network of proteins and carbohydrates that surrounds animal cells, providing support, adhesion, and communication, but also acting as a scaffold for the cell.

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Collagen

A fibrous protein found in the ECM, forming strong fibers that provide structural support.

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Proteoglycan Network

A complex network of proteoglycan molecules that bind to and entrap collagen fibers in the ECM, creating a gel-like structure.

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Desmosomes

Anchoring junctions that fasten cells together in sheets, providing strong points of attachment.

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What makes wood hard?

Wood is mostly composed of secondary cell walls, which are thicker and more rigid than primary cell walls, providing extra strength and support.

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How do cells communicate?

Cells may have specialized structures like plasmodesmata in plants or gap junctions in animals that allow for the passage of molecules between cells. The ECM can also contribute to signaling.

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What is the function of the ECM?

The ECM provides structural support, allows cells to stick together, helps cells communicate with each other, and can even influence gene activity.

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Study Notes

Concept 6.1: Microscopy and Cell Fractionation

  • Cell walls were first observed on dead oak bark in 1665 using microscopes invented in 1590.
  • Light microscopes (LM) utilize visible light passing through a specimen and glass lenses to magnify images.
  • Magnification is the ratio of an object's size to its actual size.
  • Resolution is the clarity of an image, the minimum distance between two points that can still be distinguished as separate.
  • Contrast is the difference in light and dark regions of an image.
  • Electron microscopes (EM) offer higher resolution than LMs by focusing electron beams onto a specimen.
  • Scanning electron microscopes (SEM) visualize surface topography, while transmission electron microscopes (TEM) study internal structures.
  • Electron microscopy requires specimen preparation that can introduce artifacts (structures not present in living cells).
  • Cryo-electron microscopy (Cryo-EM) uses low temperatures to avoid preservatives, allowing viewing of specimens in their natural state.
  • Cell fractionation separates cellular components using differential centrifugation in a centrifuge.

Concept 6.2: Basic Features of Cells

  • Prokaryotic cells include bacteria and archaea; eukaryotic cells include protists, fungi, animals, and plants.
  • All cells share features like a plasma membrane(cell membrane), cytosol, chromosomes, and ribosomes.
  • In eukaryotic cells, DNA is enclosed in a nucleus, while in prokaryotes, DNA is concentrated in a nucleoid region.
  • Cytoplasm is the region between the nucleus and plasma membrane in eukaryotic cells and is inclusive to prokaryotic cells.
  • Eukaryotic cells are generally larger than prokaryotic cells.
  • Cell size is constrained by metabolic needs; smaller cells have a larger surface-area-to-volume ratio.
  • Microvilli are projections that increase surface area without a significant volume increase.
  • Eukaryotic cells have internal membranes forming organelles.
  • Biological membranes consist mainly of phospholipids and proteins, forming selective barriers.
  • Enzymes are embedded in cell membranes or organelle membranes to facilitate cellular processes.

Concept 6.3: The Nucleus and Ribosomes

  • The nucleus contains most of a cell's genetic material.
  • The nuclear envelope surrounds the nucleus, separating it from the cytoplasm and containing pores.
  • The nuclear lamina supports the nuclear structure.
  • The nuclear matrix provides a framework within the nucleus.
  • Histones are proteins that package DNA into chromatin, condensed into chromosomes during cell division.
  • The nucleolus produces ribosomal RNA (rRNA) and assembles ribosome subunits.
  • Ribosomes are protein-synthesizing structures, not membrane-bound.
  • Free ribosomes reside in the cytoplasm; bound ribosomes are attached to the endoplasmic reticulum or nuclear envelope.

Concept 6.4: The Endomembrane System

  • The endomembrane system consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.
  • Vesicles transport materials between membranes.
  • Smooth ER synthesizes lipids, metabolizes carbohydrates, detoxifies poisons, and stores calcium ions.
  • Rough ER synthesizes secretory proteins and membrane proteins, with ribosomes attached to synthesize proteins.
  • Glycoproteins have carbohydrates attached in the ER.
  • The Golgi apparatus modifies, sorts, and packages proteins and lipids.
  • Lysosomes are sacs containing digestive enzymes, crucial for intracellular digestion.
  • Autophagy is the process of lysosomes breaking down damaged organelles.
  • Vacuoles are large vesicles that carry out various functions, like storage (water, nutrients), digestion, and protection (toxins).

Concept 6.5: Mitochondria, Chloroplasts, and Peroxisomes

  • Mitochondria are sites of cellular respiration, converting glucose and oxygen into ATP.
  • Chloroplasts are sites of photosynthesis, converting solar energy to chemical energy in plants and algae.
  • The endosymbiont theory proposes that mitochondria and chloroplasts evolved from prokaryotic cells engulfed by a larger cell.
  • Mitochondria and chloroplasts have their own DNA and ribosomes similar to prokaryotic cells.
  • Peroxisomes contain enzymes that transfer hydrogen to oxygen, forming hydrogen peroxide, then breaking down into water - Involved in detoxification and fatty acid breakdown.
  • Glyoxysomes are specialized peroxisomes in fat-storing plant cells converting fatty acids to sugars.

Concept 6.6: The Cytoskeleton

  • The cytoskeleton provides support, shape, structure, and transport for organelles.
  • Components include microtubules, microfilaments, and intermediate filaments.
  • Microtubules are hollow tubes made of tubulin dimers and are crucial for cell shape and organelle movement. Centrosomes often organize microtubule formation.
  • Flagella and cilia are microtubule-containing appendages that enable cell motility or move substances over surfaces.
  • Microfilaments, solid rods of actin, give structural support to the cell cortex and contribute to movement (cytoplasmic streaming, amoeboid motion).
  • Intermediate filaments provide structural support and stability, especially in animal cells.

Concept 6.7: Cell Walls and Extracellular Matrix

  • The plant cell wall protects the cell and maintains its shape against turgor pressure.
  • The cell wall is composed primarily of cellulose.
  • Plant cell walls have a primary cell wall and, sometimes, a secondary cell wall for added strength, along with a middle lamella that binds adjacent cells.
  • The extracellular matrix (ECM) in animal cells consists of glycoproteins, like collagen, embedded in a proteoglycan network which affects cell behavior.
  • Integrins, transmembrane proteins, link the ECM to the cytoskeleton, allowing communication between the cell interior and exterior.
  • Plasmodesmata are channels that connect plant cells, permitting communication and transport of substances between them.
  • Animal cells have other junctions, like tight junctions and gap junctions, that fulfill similar functions.

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Explore the fundamentals of microscopy and cell fractionation in this quiz. Dive into the differences between light microscopes and electron microscopes, and understand key concepts like magnification, resolution, and contrast. Test your knowledge of historical discoveries and modern techniques used in cell biology.

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