Eukaryotic Cells
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Questions and Answers

Which of the following characteristics is exclusive to eukaryotic cells and not found in prokaryotic cells?

  • A nucleus surrounded by a complex nuclear membrane. (correct)
  • DNA organized into a single, circular chromosome.
  • Ability to display a wide variety of cell morphologies.
  • Presence of a cytoskeleton for intracellular transport.

A scientist is studying a cell and observes that its DNA is wrapped around proteins called histones. What type of cell is the scientist most likely studying?

  • Bacterial cell
  • Eukaryotic cell (correct)
  • Viral cell
  • Archaeal cell

Which of the following factors can influence the shape of a eukaryotic cell?

  • Absence of membrane-bound organelles.
  • The presence of a nucleoid region.
  • The rigidity of its cell membrane or cell wall. (correct)
  • The lack of a cytoskeleton.

Which of the following is an example of a multicellular eukaryotic organism?

<p>Fungi (A)</p> Signup and view all the answers

What is the primary function of the nucleus in a eukaryotic cell?

<p>To control all activities of the cell and play a role in reproduction and heredity. (D)</p> Signup and view all the answers

Which of the following structures is responsible for holding organelles in place and supporting the transport of intracellular components in eukaryotic cells?

<p>The cytoskeleton. (A)</p> Signup and view all the answers

Compared to prokaryotic cells, how is the DNA organized in eukaryotic cells?

<p>Organized into multiple linear chromosomes. (B)</p> Signup and view all the answers

Which of the following is NOT a membrane-bound organelle commonly found in the cytoplasm of eukaryotic cells?

<p>Nucleoid (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of cilia?

<p>They are typically longer than flagella and fewer in number on a cell. (D)</p> Signup and view all the answers

How do cilia contribute to the function of the mammalian respiratory tract?

<p>They sweep mucus and debris up and out of the lungs. (D)</p> Signup and view all the answers

A protozoan is observed using its cilia. What is the most likely function of these cilia in this organism?

<p>To move food particles into its mouthparts. (D)</p> Signup and view all the answers

What is the primary function of a basal body associated with eukaryotic cilia and flagella?

<p>Anchoring the cilium or flagellum to the cell and organizing microtubule assembly. (B)</p> Signup and view all the answers

Why was azithromycin, rather than amoxicillin, effective in treating Barbara's pneumonia caused specifically by Mycoplasma pneumoniae?

<p>Mycoplasma pneumoniae lacks a cell wall and, therefore, is unaffected by amoxicillin, while azithromycin inhibits bacterial ribosomes. (A)</p> Signup and view all the answers

Based on the information, predict why amoxicillin, which inhibits peptidoglycan synthesis, would be effective against most bacteria but ineffective against Mycoplasma pneumoniae?

<p><em>Mycoplasma pneumoniae</em> does not possess a cell wall containing peptidoglycan. (B)</p> Signup and view all the answers

A new drug is discovered that inhibits the function of basal bodies in eukaryotic cells. What cellular function would be most immediately affected by this drug?

<p>Movement of cilia and flagella. (A)</p> Signup and view all the answers

If a eukaryotic cell's cilia are unable to perform coordinated, rhythmic movements, what is the most likely cause?

<p>A defect in the structure or function of the microtubules within the cilia. (B)</p> Signup and view all the answers

What is the primary function of the micronucleus in Paramecium?

<p>Sexual reproduction (B)</p> Signup and view all the answers

Why is mitosis considered a more complex process than binary fission?

<p>Mitosis involves multiple chromosomes that must be strategically divided. (B)</p> Signup and view all the answers

During which phase of the eukaryotic cell cycle does DNA replication occur?

<p>S phase (B)</p> Signup and view all the answers

What is the main difference between the products of mitosis and meiosis?

<p>Mitosis produces two identical daughter cells; meiosis produces four genetically distinct gametes. (D)</p> Signup and view all the answers

Where does ribosome assembly begin in eukaryotic cells?

<p>Nucleolus (D)</p> Signup and view all the answers

Which of the following is a characteristic of ribosomes found in eukaryotic organelles like mitochondria?

<p>They are the same size as prokaryotic ribosomes. (C)</p> Signup and view all the answers

How do free ribosomes differ from membrane-bound ribosomes in eukaryotic cells?

<p>Free ribosomes synthesize water-soluble proteins. (D)</p> Signup and view all the answers

Why can certain antibiotics that target prokaryotic ribosomes have negative side effects on humans?

<p>Mitochondria in human cells contain prokaryotic ribosomes. (C)</p> Signup and view all the answers

What is the primary function of the endomembrane system in eukaryotic cells?

<p>To synthesize and transport cellular components (D)</p> Signup and view all the answers

Which of the following structures is NOT a component of the endomembrane system?

<p>Mitochondria (D)</p> Signup and view all the answers

What structural feature defines the endoplasmic reticulum (ER)?

<p>Single lipid bilayer (B)</p> Signup and view all the answers

What controls the movement of substances into and out of the nucleus?

<p>Nuclear pores (A)</p> Signup and view all the answers

What is the role of the nuclear lamina?

<p>To determine the shape of the nucleus (A)</p> Signup and view all the answers

Which stage of the mitotic phase involves the physical separation of cytoplasmic components into two daughter cells?

<p>Cytokinesis (C)</p> Signup and view all the answers

What is the outcome of meiosis?

<p>Four genetically distinct gametes (B)</p> Signup and view all the answers

What is the primary distinction between the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER)?

<p>RER is associated with ribosomes and protein synthesis, whereas SER is involved in lipid biosynthesis and detoxification. (A)</p> Signup and view all the answers

How do proteins synthesized in the rough endoplasmic reticulum (RER) typically reach their final destination within or outside the cell?

<p>They are encapsulated in transport vesicles that bud off from the RER. (D)</p> Signup and view all the answers

Which of the following best describes the role of the Golgi apparatus in modifying proteins and lipids?

<p>It adds carbohydrate components to them, forming glycolipids, glycoproteins, or proteoglycans. (D)</p> Signup and view all the answers

What is the primary function of exocytosis in eukaryotic cells?

<p>To release cellular contents, such as proteins, to the cell's exterior. (B)</p> Signup and view all the answers

What distinguishes regulated secretory pathways from constitutive secretory pathways in cells?

<p>Regulated pathways store soluble proteins in secretory vesicles, releasing them only in response to specific signals, while constitutive pathways release them continually. (B)</p> Signup and view all the answers

What is the primary function of lysosomes within eukaryotic cells?

<p>To break down various particles, such as food, damaged organelles, and microorganisms. (D)</p> Signup and view all the answers

How do peroxisomes differ from other organelles of the endomembrane system in their formation?

<p>Peroxisomes form independently in the cytoplasm through the synthesis of peroxin proteins. (B)</p> Signup and view all the answers

What role do peroxisomes and SER play together in cells?

<p>Both play a role in lipid biosynthesis. (D)</p> Signup and view all the answers

What is the role of catalase in peroxisomes?

<p>It degrades hydrogen peroxide into water and oxygen. (A)</p> Signup and view all the answers

What function do glyoxysomes perform in yeast and plant cells?

<p>They produce sugar molecules. (A)</p> Signup and view all the answers

How does the cytoskeleton contribute to the process of exocytosis?

<p>It provides a network over which vesicles can be transported to the plasma membrane. (A)</p> Signup and view all the answers

Which of the following describes the composition of microfilaments in the cytoskeleton?

<p>Intertwined strands of actin monomers. (A)</p> Signup and view all the answers

What is the role of motor proteins, such as myosin, in conjunction with actin filaments?

<p>To effect muscle contraction in animals and amoeboid movement in some eukaryotic microbes. (D)</p> Signup and view all the answers

In ameboid organisms, what role does the gel form of actin play in the ectoplasm?

<p>It creates stability in the ectoplasm to support the formation of pseudopodia. (B)</p> Signup and view all the answers

How are pseudopodia formed in ameboid organisms?

<p>Through the forward flow of soluble actin filaments and gel-sol cycling. (C)</p> Signup and view all the answers

Which of the following is a key difference between eukaryotic and prokaryotic plasma membranes?

<p>Eukaryotic membranes contain sterols like cholesterol, which are absent in prokaryotic membranes. (A)</p> Signup and view all the answers

How does receptor-mediated endocytosis differ from pinocytosis and phagocytosis?

<p>Receptor-mediated endocytosis is triggered by the binding of specific ligands to cell surface receptors. (B)</p> Signup and view all the answers

Which of the following is a primary function of the extracellular matrix in animal cells?

<p>Maintaining cell shape and providing structural stability in the absence of a cell wall. (C)</p> Signup and view all the answers

Which of the following best describes the arrangement of microtubules in eukaryotic flagella?

<p>Nine parallel pairs of microtubules surrounding two central microtubules (9+2 array). (A)</p> Signup and view all the answers

What is the role of dynein in the function of eukaryotic flagella?

<p>Dynein acts as a motor protein, causing the microtubules to slide past each other and bend the flagellum. (B)</p> Signup and view all the answers

How do mitosomes and hydrogenosomes support the understanding of eukaryotic cell evolution?

<p>They provide evidence that certain eukaryotic cells have lost or modified mitochondria over time. (A)</p> Signup and view all the answers

Which of the following cell wall components is commonly found in fungi?

<p>Chitin (A)</p> Signup and view all the answers

What is the process of exocytosis primarily used for in eukaryotic cells?

<p>Release of waste products and chemical signals to the cell's exterior. (A)</p> Signup and view all the answers

How does the structure of eukaryotic flagella differ functionally from that of prokaryotic flagella?

<p>Eukaryotic flagella move in a whip-like fashion, whereas prokaryotic flagella rotate. (C)</p> Signup and view all the answers

Which components attach both proteoglycans and collagen to transmembrane proteins in the plasma membranes of eukaryotic cells lacking cell walls?

<p>Integrin and fibronectin (A)</p> Signup and view all the answers

How does the presence of specialized lipids, like sphingolipids, contribute to eukaryotic cell membrane function?

<p>By maintaining membrane stability and participating in signal transduction. (A)</p> Signup and view all the answers

A researcher observes a cell engulfing a large bacterium. Which process is the cell utilizing?

<p>Phagocytosis (A)</p> Signup and view all the answers

Which of the following is NOT a typical component of the extracellular matrix?

<p>Cellulose (B)</p> Signup and view all the answers

What is the functional significance of cells secreting a sticky mass of carbohydrates and proteins into the spaces between adjacent cells?

<p>To form an extracellular matrix that provides support and mediates cell interactions. (B)</p> Signup and view all the answers

If a eukaryotic cell suddenly lost its ability to perform exocytosis, which of the following would be the most immediate consequence?

<p>Build-up of waste products within the cell. (A)</p> Signup and view all the answers

Which of the following activities is NOT directly facilitated by the dynamic nature of microfilaments?

<p>Maintaining the fixed position of the nucleus within the cell (C)</p> Signup and view all the answers

How do intermediate filaments differ from microfilaments and microtubules in terms of their composition and function?

<p>Intermediate filaments, made of diverse monomers, primarily provide structural support and maintain cell shape. (C)</p> Signup and view all the answers

What is the role of motor proteins, such as dynein and kinesin, in relation to microtubules?

<p>To transport organelles and vesicles along the microtubule network (A)</p> Signup and view all the answers

What evidence supporting the endosymbiotic theory is found within mitochondria?

<p>The presence of a double membrane, 70S ribosomes and their own bacterial genome. (C)</p> Signup and view all the answers

How do the cristae within mitochondria contribute to the organelle's function?

<p>They increase the surface area available for the electron transport chain. (B)</p> Signup and view all the answers

What is the primary role of the thylakoid membrane system within chloroplasts?

<p>To house chlorophyll and facilitate the light reactions of photosynthesis. (D)</p> Signup and view all the answers

How do hydrogenosomes differ from mitochondria in terms of their function and presence in eukaryotic cells?

<p>Hydrogenosomes are found in anaerobic eukaryotes and are the site of anaerobic hydrogen production. (A)</p> Signup and view all the answers

In eukaryotic cells, what distinguishes kinetoplasts from typical mitochondria?

<p>Kinetoplasts contain DNA organized as multiple circular pieces concentrated at one pole. (B)</p> Signup and view all the answers

How does the arrangement of microtubules differ between a centriole and a eukaryotic flagellum?

<p>Centrioles have triplet microtubules, while flagella have a 9+2 arrangement. (A)</p> Signup and view all the answers

What is the functional significance of the dynamic assembly and disassembly of microtubules?

<p>It enables cellular processes such as cell division and intracellular transport. (A)</p> Signup and view all the answers

If a researcher discovers a new eukaryotic cell with a unique organelle containing its own DNA and ribosomes, what evolutionary process likely led to the origin of this organelle?

<p>Endosymbiosis of a prokaryotic cell by a eukaryotic cell. (D)</p> Signup and view all the answers

How does the structural arrangement of grana within chloroplasts maximize photosynthetic efficiency?

<p>By concentrating chlorophyll molecules to capture more light. (B)</p> Signup and view all the answers

What cellular function would be most immediately compromised by a drug that inhibits the polymerization of tubulin?

<p>The proper segregation of chromosomes during cell division. (D)</p> Signup and view all the answers

Desmosomes are protein structures containing desmin and are responsible for what function?

<p>Anchoring cells together in animal tissues and helping them resist external physical forces. (C)</p> Signup and view all the answers

A cell is treated with a drug that disrupts the function of dynein. Which cellular process would be most directly affected?

<p>The movement of vesicles within the cell. (B)</p> Signup and view all the answers

Flashcards

Eukaryotic Organisms

Organisms with cells that contain a nucleus and membrane-bound organelles.

Nucleus

A structure that has a double membrane and houses the cell's DNA.

Organelles

Specialized structures within eukaryotic cells that perform specific functions.

Cytoskeleton

An internal protein network that supports intracellular transport and maintains cell shape.

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Chromosomes

Multiple, linear structures in eukaryotic cell nucleus that contain the cell's DNA.

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Histones

Structures used to package DNA in the nucleus of eukaryotic cells.

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Nuclear Membrane

The membrane enclosing the nucleus in eukaryotic cells.

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Cell morphology

The shape that a particular type of eukaryotic cell has.

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Lumen of the ER

The space within the cisternae of the endoplasmic reticulum.

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Rough Endoplasmic Reticulum (RER)

Endoplasmic reticulum with ribosomes attached; involved in protein synthesis.

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Smooth Endoplasmic Reticulum (SER)

Endoplasmic reticulum without ribosomes; involved in lipid biosynthesis and detoxification.

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Transport Vesicles

Small sacs that bud off from the ER, carrying newly synthesized proteins to the Golgi or plasma membrane.

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Golgi Apparatus

Organelle that modifies and packages proteins and lipids; sorts and ships them to their final destinations.

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Glycolipids/Glycoproteins

Lipids or proteins with carbohydrate chains added in the Golgi apparatus.

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Cis Face (Golgi)

The receiving side of the Golgi apparatus.

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Trans Face (Golgi)

The outgoing side of the Golgi apparatus.

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Exocytosis

Process by which cells release substances to the exterior through vesicles.

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Constitutive Secretory Pathway

Secretion pathway where substances are continually released from the cell.

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Regulated Secretory Pathway

Secretion pathway where substances are stored and released only in response to specific signals.

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Lysosomes

Organelles containing digestive enzymes for breaking down various cellular materials.

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Peroxisomes

Organelles that produce hydrogen peroxide and contain catalase to break it down; involved in lipid biosynthesis.

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Glyoxysomes

Modified peroxisomes in yeasts and plant cells that produce sugar molecules.

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Micronucleus

Small nucleus used for reproduction in some protozoans like Paramecium.

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Macronucleus

Large nucleus that directs cellular metabolism in some protozoans.

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Heterokaryotic Cells

Cells with two nuclei formed transiently during sexual reproduction in fungi.

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Coenocytes

Cells whose nuclei divide but the cytoplasm does not divide creating a multi-nucleated cell.

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Nuclear Envelope

A double membrane structure enclosing the nucleus in eukaryotic cells.

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Nuclear Pores

Large protein complexes in the nuclear envelope that control movement of substances in and out of the nucleus.

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Nuclear Lamina

Meshwork of intermediate filaments inside the nuclear envelope that provides shape and support to the nucleus.

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Mitosis

A form of asexual reproduction in eukaryotic cells that produces two identical daughter cells.

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Eukaryotic Cell Cycle

Ordered series of events for cell growth, DNA replication, and cell division in eukaryotes.

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Interphase

The phase of the cell cycle when the cell grows and replicates its DNA in preparation for division.

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Mitotic Phase

The phase of the cell cycle when the cell divides its nucleus (karyokinesis) and cytoplasm (cytokinesis).

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Karyokinesis

Nuclear division, includes prophase, metaphase, anaphase, and telophase.

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Cytokinesis

Physical separation of the cytoplasm into two daughter cells.

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Meiosis

A type of sexual reproduction that creates four genetically distinct gametes with half the number of chromosomes.

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Pseudopodium

A temporary projection of cytoplasm used by amoeboid cells for movement.

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Cytoplasmic Streaming

Movement or circulation of cytoplasm within a cell.

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Microfilaments

Dynamic filaments that polymerize and depolymerize easily, involved in cell movement and structure.

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Intermediate Filaments

Cytoskeletal filaments that act as cables to maintain cell shape, position organelles, and anchor cells together.

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Microtubules

Cytoskeletal fibers composed of tubulin dimers, forming hollow tubes used for intracellular transport and cell division.

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Mitochondria

Organelles that generate energy through aerobic cellular respiration and have a double membrane.

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Cristae

Invaginations of the inner mitochondrial membrane that increase surface area for biochemical reactions.

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Chloroplasts

Organelles in plant and algal cells where photosynthesis occurs, containing chlorophyll.

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Chloroplast Stroma

The gel-like fluid inside chloroplasts, surrounding the thylakoid system.

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Thylakoid

Membrane sacs within chloroplasts where chlorophyll is found and light reactions occur.

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Grana

Stacks of thylakoids in plant chloroplasts.

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Hydrogenosomes

Organelles in anaerobic eukaryotes that produce hydrogen.

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Kinetoplast

A variation of mitochondria in some eukaryotic pathogens, containing kinetoplast DNA.

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Mitochondrial Matrix

The location of many metabolic enzymes, mitochondrial DNA, and 70S ribosomes.

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Centrosomes

Microtubule-organizing centers that produce the mitotic spindle during cell division.

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Giardia lamblia

Anaerobic parasite with mitosomes instead of mitochondria; causes diarrhea.

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Trichomonas vaginalis

Protozoan parasite with hydrogenosomes, causes vaginitis.

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Sterols

Lipids in eukaryotic membranes that affect fluidity.

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Phagocytosis

Endocytosis involving engulfment of large particles.

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Pinocytosis

Endocytosis of small materials and liquids.

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Receptor-mediated endocytosis

Endocytosis triggered by ligands binding to cell surface receptors.

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Cell Wall Function

Provides cell structure and protection.

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Extracellular Matrix

Provides structural support to cells lacking a cell wall.

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Collagen

Fibrous protein providing strength in the extracellular matrix.

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Fibronectin

Connect extracellular matrix components.

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Integrins

Transmembrane proteins that interact with the extracellular matrix.

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Eukaryotic Flagella

Eukaryotic locomotion structure with a 9+2 array.

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Cilia

External structures similar to flagella; for movement.

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Basal Body

A structure at the base of cilia and flagella that anchors them to the cell.

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Cilia Movement

A rapid, flexible motion used by cilia.

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Cilia in Protozoans

Protozoans use cilia to sweep food into their 'mouth'.

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Cilia Cleaning Lungs

Cells in the respiratory tract use cilia to sweep mucus and debris out of the lungs.

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Azithromycin

An antibiotic that inhibits bacterial ribosomes.

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Mycoplasma pneumoniae

A bacterium that lacks a cell wall, making it resistant to some antibiotics.

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Peptidoglycan

A key component of bacterial cell walls targeted by some antibiotics.

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Study Notes

  • Eukaryotic organisms include protozoans, algae, fungi, plants, and animals.
  • Some eukaryotic cells are single-celled microorganisms, while others form multicellular organisms.
  • Eukaryotic cells are characterized by a nucleus enclosed by a nuclear membrane and membrane-bound organelles within the cytoplasm.
  • Organelles like mitochondria, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and peroxisomes are held by the cytoskeleton.
  • The cytoskeleton supports intracellular transport and maintains cell shape.
  • Eukaryotic genomes consist of multiple, rod-shaped chromosomes, unlike the single, circular chromosome in prokaryotes.
  • Eukaryotic cells exhibit diverse morphologies, including spheroid, ovoid, cuboidal, and irregular shapes.
  • A cell's shape is influenced by its function, cytoskeleton, cytoplasm viscosity, and cell membrane or wall rigidity.

Nucleus

  • The nucleus, enclosed by a nuclear membrane, houses the DNA genome in eukaryotic cells.
  • It controls cell activities and is crucial for reproduction and heredity.
  • Eukaryotic DNA is organized into multiple linear chromosomes, condensed by wrapping around histones.
  • Most eukaryotic cells have one nucleus, but some protozoans (e.g., Paramecium) have two, and some fungi form heterokaryotic cells with two nuclei during sexual reproduction.
  • Coenocytes are cells whose nuclei divide without cytoplasmic division.
  • The nuclear envelope consists of two lipid bilayers with unique lipids and proteins.
  • Nuclear pores within the envelope control the movement of substances into and out of the nucleus.
  • The nuclear lamina, a meshwork of intermediate filaments, determines the nucleus's shape and anchors it within the cell.

Reproduction

  • Eukaryotes reproduce asexually through mitosis, producing identical daughter cells.
  • Mitosis is more complex than binary fission in prokaryotes due to multiple chromosomes.
  • The eukaryotic cell cycle includes interphase (G1, S, G2) for growth and DNA replication, and the mitotic phase for cell division.
  • The mitotic phase involves karyokinesis (nuclear division with prophase, prometaphase, metaphase, anaphase, and telophase) and cytokinesis (cytoplasmic separation).
  • Many eukaryotic microorganisms can also reproduce sexually through meiosis.
  • Meiosis involves two nuclear divisions, creating four genetically distinct gametes with half the original chromosome number.
  • Chromosome reduction is essential for fertilization to produce a zygote with a full set of chromosomes.

Ribosomes

  • The nucleolus, a dense region in the nucleus, is where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins.
  • Preribosomal complexes of rRNA and proteins are assembled, then transported to the cytoplasm for completion.
  • Ribosomes in eukaryotic organelles like mitochondria and chloroplasts are 70S, similar to prokaryotic ribosomes.
  • Non-organelle-associated ribosomes in eukaryotic cells are 80S ribosomes, made of a 40S small subunit and a 60S large subunit.
  • Free ribosomes in the cytoplasm synthesize water-soluble proteins.
  • Membrane-bound ribosomes on the rough endoplasmic reticulum make proteins for the cell membrane or export.
  • Antibiotics like cycloheximide target eukaryotic ribosomes, while chloramphenicol targets prokaryotic ribosomes.

Endomembrane system

  • Unique to eukaryotic cells, the endomembrane system is a network of tubules, sacs, and disks that synthesizes and transports cell components.
  • The endomembrane system includes the endoplasmic reticulum, Golgi apparatus, lysosomes, and vesicles.
  • The endoplasmic reticulum (ER) is a network of tubules and cisternae (flattened sacs) with a single lipid bilayer.
  • Rough ER (RER) has ribosomes for protein synthesis, while smooth ER (SER) is involved in lipid synthesis, carbohydrate metabolism, and detoxification.
  • Transport vesicles bud off from the ER to carry proteins to the Golgi apparatus or plasma membrane.
  • Enzymes in the Golgi apparatus modify lipids and proteins, often adding carbohydrates to create glycolipids and glycoproteins.
  • Transport vesicles from the ER fuse with the Golgi apparatus, where proteins are further processed and sent to the plasma membrane or other organelles.
  • Exocytosis is the process by which secretory vesicles release their contents outside the cell.

Lysosomes & Peroxisomes

  • Lysosomes, discovered by Christian de Duve, are membrane-bound organelles containing digestive enzymes.
  • They break down particles, damaged organelles, and cellular debris, compartmentalizing digestive enzymes.
  • Peroxisomes, also discovered by Christian de Duve, are membrane-bound organelles that form independently in the cytoplasm.
  • They produce hydrogen peroxide to break down molecules and contain catalase to degrade hydrogen peroxide.
  • Peroxisomes play a role in lipid biosynthesis.
  • Glyoxysomes (in yeasts and plant cells) and glycosomes (in trypanosomes) are specialized peroxisomes with specific metabolic functions.

Cytoskeleton

  • Eukaryotic cells have a cytoskeleton composed of microfilaments, intermediate filaments, and microtubules.
  • This network provides structural support, facilitates transport, and anchors organelles.
  • Microfilaments are composed of two intertwined strands of actin that work with motor proteins for muscle contraction and amoeboid movement.
  • Intermediate filaments are cables that maintain the position of the nucleus and anchor cells together in animal tissues, maintaing cell structure.
  • Microtubules are hollow tubes made of tubulin dimers that move organelles, form eukaryotic flagella and cilia, and participate in cell division.
  • Mitotic spindles during cell division are produced by centrosomes which contains a pair of centrioles arranged at right angles to each other.

Mitochondria & Chloroplasts

  • Mitochondria, where aerobic cellular respiration occurs, have their own genome and 70S ribosomes supporting the endosymbiotic theory.
  • Each mitochondrion has two lipid membranes, with the inner membrane containing the electron transport chain.
  • The mitochondrial matrix contains metabolic enzymes, mitochondrial DNA, and 70S ribosomes.
  • Cristae, invaginations of the inner membrane, increase surface area for biochemical reactions.
  • Plant and algal cells contain chloroplasts, where photosynthesis occurs.
  • Chloroplasts have outer, inner, and thylakoid membrane systems, with chlorophyll in the thylakoid system where light reactions occur.
  • Thylakoids are arranged in grana in most plant chloroplasts.

Other Organelles

  • Hydrogenosomes in anaerobic eukaryotes produce hydrogen.
  • Kinetoplasts, a variation of mitochondria, are found in some eukaryotic pathogens.
  • Some protozoan parasites, like Giardia lamblia and Trichomonas vaginalis, have modified or absent organelles.
  • G. lamblia lacks mitochondria but has mitosomes, while T. vaginalis has hydrogenosomes.

Cell Membranes

  • Eukaryotic plasma membranes are composed of a phospholipid bilayer with embedded proteins, similar to prokaryotic membranes.
  • Eukaryotic membranes contain sterols like cholesterol for membrane fluidity and specialized lipids like sphingolipids for membrane stability.
  • Eukaryotic cells perform endocytosis, including phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis.

Walls & ECM

  • Some eukaryotic cells have cell walls made of cellulose, silica, chitin, or other materials for structural stability and protection.
  • Animal cells and some protozoans produce an extracellular matrix (ECM) of carbohydrates and proteins for structural support.
  • The ECM consists of proteoglycans, fibrous proteins like collagen, and fibronectin proteins attached to integrin proteins.
  • The ECM allows cells to withstand external stresses and transmits signals.

External Structures

  • Eukaryotic flagella are flexible whips with a 9+2 array of microtubules, using dynein motor proteins for movement.
  • Cilia are shorter structures with a 9+2 array, using a rapid waving motion for motility and sweeping particles.
  • Basal bodies anchor cilia and flagella to the cell.

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Questions about the characteristics, components, and functions of eukaryotic cells. Includes the nucleus, organelles, DNA organization, cell shape, and the role of cilia.

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