Introduction to Eukaryotic Cells
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Introduction to Eukaryotic Cells

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Questions and Answers

What is the primary function of the plasma membrane?

  • To store genetic information
  • To produce energy
  • To separate the external and internal environments of the cell (correct)
  • To digest cellular waste

    • Eukaryotic cells are the only type of cells that possess membranous organelles.

    True

    How many different types of cells exist in the human body?

    approximately 200

    The __________ is a jelly-like fluid that fills the space between organelles in a cell.

    <p>cytoplasm</p> Signup and view all the answers

    Match the organelle type with its primary function:

    <p>Mitochondrion = Produces energy Ribosome = Protein synthesis Centrioles = Organizes microtubules Nucleus = Stores genetic information</p> Signup and view all the answers

    Which of the following structures is made primarily of actin and myosin?

    <p>Cytoskeleton</p> Signup and view all the answers

    Microtubules are static and do not change in composition during cellular processes.

    <p>False</p> Signup and view all the answers

    What is the role of the cytoskeleton in a cell?

    <p>To shape, stabilize, and move cells and their internal structures.</p> Signup and view all the answers

    What is the role of the sodium-potassium (Na+-K+) pump in animal cells?

    <p>To move Na+ out and K+ into the cell, using ATP.</p> Signup and view all the answers

    Secondary active transporters move solutes against their concentration gradient without the use of ATP.

    <p>False</p> Signup and view all the answers

    What is the mechanism called when a cell engulfs a large particle and internalizes it into a vesicle?

    <p>phagocytosis</p> Signup and view all the answers

    Water moves through aquaporins across the plasma membrane, facilitating diffusion_.

    <p>facilitated</p> Signup and view all the answers

    Match the types of solutions with their effects on a red blood cell:

    <p>Isotonic = No net water movement Hypertonic = Cell shrinks (crenates) Hypotonic = Cell swells Intravenous (IV) fluids = Must be isotonic to blood</p> Signup and view all the answers

    What is the primary function of cilia in cells?

    <p>Propel cells through fluid</p> Signup and view all the answers

    The centrosome contains long microtubules called centrioles.

    <p>False</p> Signup and view all the answers

    What are the small holes in the nuclear envelope that allow for the exit of mRNAs?

    <p>nuclear pores</p> Signup and view all the answers

    Ribosomes are assembled in the ____________.

    <p>nucleolus</p> Signup and view all the answers

    What is the main function of the smooth endoplasmic reticulum?

    <p>Manufacture lipids</p> Signup and view all the answers

    The Golgi complex is responsible for breaking down cellular molecules.

    <p>False</p> Signup and view all the answers

    The ____________ is all of the DNA in an organism.

    <p>genome</p> Signup and view all the answers

    Match the organelle with its primary function:

    <p>Lysosome = Breaks down cellular waste Nucleus = Stores genetic information Rough ER = Synthesizes proteins Peroxisome = Detoxifies harmful substances</p> Signup and view all the answers

    What type of RNA is bound by ribosomal subunits during translation?

    <p>mRNA</p> Signup and view all the answers

    What disease results from defective lysosomes?

    <p>Tay-Sachs disease</p> Signup and view all the answers

    What is the primary function of mitochondria in cells?

    <p>Processing of energy</p> Signup and view all the answers

    Mitochondria contain their own DNA and replicate independently of the nuclear genome.

    <p>True</p> Signup and view all the answers

    Identify the structure formed by the extensive folding of the inner mitochondrial membrane.

    <p>cristae</p> Signup and view all the answers

    Aerobic cellular respiration ends with the synthesis of __________.

    <p>ATP</p> Signup and view all the answers

    Match the phases of mitosis with their descriptions:

    <p>Prophase = Dissolution of the nuclear envelope and condensation of chromatin Metaphase = Alignment of chromosomes at the equatorial plate Anaphase = Pulling of chromosomes to opposite poles Telophase = Partitioning of two components into daughter cells</p> Signup and view all the answers

    What term describes the division of the cytoplasmic components after mitosis?

    <p>Cytokinesis</p> Signup and view all the answers

    Telomeres protect chromosomes from shortening by capping their ends.

    <p>True</p> Signup and view all the answers

    What is the result of meiosis II?

    <p>four nonidentical gametes</p> Signup and view all the answers

    The sequence of events during somatic cell division is called the __________.

    <p>cell cycle</p> Signup and view all the answers

    Which statement is true regarding human chromosomes?

    <p>Telomeres prevent degradation of chromosome ends.</p> Signup and view all the answers

    What percentage of the membrane is composed of phospholipids?

    <p>75%</p> Signup and view all the answers

    Cholesterol decreases membrane fluidity.

    <p>True</p> Signup and view all the answers

    Define membrane fluidity.

    <p>Membrane fluidity refers to the viscosity of the lipid bilayer of a cell membrane, which allows for the movement of lipids and proteins within the membrane.</p> Signup and view all the answers

    The membrane is permeable to _______ molecules like O2 and CO2, as they can travel through the membrane without help.

    <p>nonpolar</p> Signup and view all the answers

    Match the following types of membrane proteins with their functions:

    <p>Integral proteins = Span the entire membrane Peripheral proteins = Bound by electrostatic interactions Glycoproteins = Help distinguish cell types Receptor proteins = Bind specific molecules to send signals</p> Signup and view all the answers

    Which statement about membrane fluidity is correct?

    <p>Unsaturated fatty acids lead to a more fluid membrane.</p> Signup and view all the answers

    Active transport does not require metabolic energy.

    <p>False</p> Signup and view all the answers

    What role do ion channels play in facilitated diffusion?

    <p>Ion channels provide a pore that allows charged substances to diffuse across membranes.</p> Signup and view all the answers

    A _______ gradient refers to the difference in concentration of a substance within a system.

    <p>concentration</p> Signup and view all the answers

    What happens to the rate of diffusion as temperature increases?

    <p>It increases.</p> Signup and view all the answers

    Study Notes

    Introduction to Cells

    • Cells vary greatly in shape and size, with approximately 200 distinct types present in the human body.
    • Cells serve as the fundamental unit of life, organized into specialized subunits called organelles, which perform specific functions.
    • Only eukaryotic cells, such as human cells, contain membranous organelles.

    Organelles of Eukaryotic Cells

    • The plasma membrane functions as a flexible barrier, regulating material exchange and facilitating cell communication.
    • Cytoplasm includes all components between the plasma membrane and nucleus, providing an environment for chemical reactions.
    • The cytoskeleton, made from actin, myosin, intermediate filaments, and microtubules, provides structure, stability, and movement to cells.
    • Organizes microtubules within centrosomes, which play a crucial role during cell division through the formation of the mitotic spindle.
    • Structures like cilia and flagella assist in cellular movement: cilia are short and move fluid, while flagella are long and propel cells.

    Nucleus and DNA

    • The nucleus, a membranous organelle, houses DNA within a double membrane called the nuclear envelope, punctuated by nuclear pores.
    • DNA must be compacted to fit within the cell; it can exist as chromatin (loose form) or tightly packed chromosomes (condensed).
    • Ribosomes, composed of rRNA and protein, synthesize proteins from mRNA in a process known as translation, occurring in the cytoplasm.

    Endoplasmic Reticulum and Golgi Complex

    • The rough endoplasmic reticulum (rER) contains ribosomes, synthesizing proteins for organelles while being continuous with the nuclear membrane.
    • The smooth endoplasmic reticulum (sER) synthesizes lipids, metabolizes carbohydrates, and stores calcium ions.
    • The Golgi complex modifies, sorts, and packages proteins into vesicles. It has distinct entry and exit faces for efficient processing.

    Lysosomes, Peroxisomes, and Proteasomes

    • Lysosomes contain enzymes for breaking down cellular materials and recycling waste. Dysfunction can lead to diseases like Tay-Sachs.
    • Peroxisomes oxidize molecules, metabolizing fatty acids and detoxifying substances like alcohol.
    • Proteasomes degrade proteins into smaller peptides, playing a role in cell regulation; dysfunction can be linked to neurodegenerative diseases.

    Mitochondria

    • Mitochondria are known as the powerhouses of the cell, involved in aerobic cellular respiration and ATP production.
    • They feature two membranes, with the inner membrane extensively folded to increase surface area for energy reactions.
    • Unique in having their own DNA, mitochondria are maternally inherited and play a role in apoptotic pathways.

    Cell Division

    • Somatic cells undergo mitosis and cytokinesis, involving a series of phases known as the cell cycle: G1, S, and G2 phases prepare for division.
    • Mitosis consists of four stages: prophase, metaphase, anaphase, and telophase, ultimately followed by cytokinesis.
    • Telomeres protect chromosome ends and shorten with age, influencing aging processes and cancer development due to their effect on cell division.

    Reproductive Cell Division

    • Meiosis produces haploid gametes through two divisions, including genetic crossover to promote diversity.
    • Meiosis I separates homologous chromosomes, while meiosis II separates sister chromatids, resulting in four non-identical daughter cells.

    Membrane Structure and Function

    • The plasma membrane's fluid mosaic model describes its flexible permeability, allowing selective transport of substances.
    • The lipid bilayer comprises phospholipids, making up 75% of the membrane, with cholesterol and glycolipids comprising 20% and 5%, respectively.
    • Membrane fluidity is influenced by fatty acid saturation and temperature; unsaturated fatty acids enhance fluidity compared to saturated ones.

    Transport Mechanisms

    • Nonpolar molecules diffuse freely across membranes, while polar substances require assistance via facilitated diffusion through protein channels.
    • Active transport mechanisms move substances against their gradients, necessitating energy but enabling maintenance of specific ion concentrations within cells.### Active Transport Mechanisms
    • Active transport involves moving solutes against concentration gradients across membranes.
    • Sodium-potassium (Na+-K+) pump in animal cells maintains higher Na+ concentration outside the cell and higher K+ concentration inside.
    • The Na+-K+ pump is a primary active transporter that utilizes ATP hydrolysis to function.

    Types of Active Transporters

    • Primary active transporters require ATP directly to move solutes against their gradients.
    • Secondary active transporters do not use ATP directly; instead, they rely on electrochemical gradients created by primary transporters.
    • Secondary active transporters transport two solutes; one moves down its gradient, releasing free energy, while the other moves against its gradient.

    Types of Secondary Active Transport

    • Symporters allow both solutes to flow in the same direction.
    • Antiporters transport solutes in opposite directions.

    Effects of Cyanide on Active Transport

    • Cyanide inhibits ATP production, resulting in loss of all forms of active transport due to lack of energy.

    Vesicular Transport

    • Vesicles are membrane sacs used for transporting substances between organelles.
    • Endocytosis is the process of moving substances into cells; exocytosis refers to the release of substances out of cells, also known as secretion.
    • Both processes require ATP hydrolysis.
    • Transcytosis involves substances moving through cells by sequential endocytosis and exocytosis.

    Endocytosis Types

    • Receptor-mediated endocytosis specifically imports selected molecules into cells.
    • Phagocytosis is a process where phagocytic cells "eat" cells or molecules, engulfing them into a vesicle for digestion by lysosomes.
    • Pinocytosis, or "cell drinking," involves the uptake of dissolved solutes into large vesicles.

    Osmosis and Water Movement

    • Osmosis is the movement of water from low solute concentration to high concentration across a semi-permeable membrane.
    • Aquaporins are specialized channel proteins that facilitate efficient water movement across cell membranes.

    Cell Responses to Solutions

    • Hypertonic solutions have higher solute concentrations than the inside of the cell, causing water to flow out and resulting in cell shrinkage.
    • Hypotonic solutions have lower solute concentrations, resulting in water flowing into the cell and potentially causing it to swell.
    • Isotonic solutions have equal solute concentration inside and outside the cell, resulting in no net water movement.

    Osmolarity and Tonicity

    • Osmolarity defines the total solute concentration of a solution, impacting how cells behave when exposed to different solutions.
    • The osmolarity of solutions is crucial for determining their tonicity: isotonic, hypotonic, or hypertonic.
    • Understanding osmolarity is essential, especially in medical contexts like intravenous (IV) fluids, which should be isotonic to maintain cell integrity.

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    Description

    Explore the fascinating world of eukaryotic cells and their organelles. Understand the roles of the plasma membrane, cytoplasm, and cytoskeleton in cell function. This quiz will test your knowledge of the various types of cells and their specialized structures.

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