Cell Biology Overview
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Questions and Answers

What is the primary function of the nucleus in eukaryotic cells?

  • Storage of proteins
  • Transport of materials across membranes
  • Synthesis of ATP
  • Control center for genetic information (correct)
  • Which structure is responsible for controlling the movement of proteins and RNAs across the nuclear envelope?

  • Nuclear lamina
  • Chromatin
  • Nucleoplasm
  • Nuclear pore complexes (correct)
  • What is the main difference between chromatin and nucleolus?

  • Chromatin synthesizes proteins, while nucleolus stores DNA.
  • Nucleolus contains enzymes; chromatin is solely composed of RNA.
  • Chromatin is involved in rRNA synthesis; nucleolus contains DNA.
  • Nucleolus is a dense mass associated with the nuclear envelope; chromatin is not. (correct)
  • Which of the following statements about the nucleolus is incorrect?

    <p>It synthesizes DNA polymerase. (B)</p> Signup and view all the answers

    Mitochondria are known as the powerhouse of the cell primarily due to their role in:

    <p>Producing ATP through cellular respiration (C)</p> Signup and view all the answers

    What feature allows mitochondria to change shape under different metabolic conditions?

    <p>Their dynamic lipid bilayer (D)</p> Signup and view all the answers

    In eukaryotes, where does DNA replication and RNA transcription occur?

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

    Which of the following statements regarding mitochondria is true?

    <p>Mitochondrial numbers vary by cell type. (B)</p> Signup and view all the answers

    Which of the following organelles is associated with the synthesis of ribosomal RNA?

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

    What role does catalase enzyme play in peroxisomes?

    <p>It destroys toxic hydrogen peroxide. (A)</p> Signup and view all the answers

    Which enzyme is NOT found in the nucleolus?

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

    Which statement about cytoplasm is incorrect?

    <p>Cytoplasm is devoid of metabolic reactions. (B)</p> Signup and view all the answers

    What is a primary function of the plasma membrane?

    <p>It enables selective permeability. (B)</p> Signup and view all the answers

    Which component typically does not contribute significantly to cellular membranes?

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

    In eukaryotic cells, what is the role of the internal membrane systems?

    <p>To assist in the functions of surrounding organelles. (B)</p> Signup and view all the answers

    What is the main component of the outer mitochondrial membrane?

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

    What percentage of membrane composition typically consists of carbohydrates?

    <p>1 to 10 percent (D)</p> Signup and view all the answers

    Which of the following does not describe peroxisomes?

    <p>They exclusively metabolize short-chain fatty acids. (D)</p> Signup and view all the answers

    Which proteins are responsible for allowing substances to diffuse across the outer mitochondrial membrane?

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

    What is the lipid-protein ratio in the inner mitochondrial membrane?

    <p>0.27:1 (A)</p> Signup and view all the answers

    What is the major characteristic of membrane permeability?

    <p>Membranes exhibit selective permeability. (D)</p> Signup and view all the answers

    Which statement about the intermembrane space is true?

    <p>It has about the same ionic composition as the cytosol. (C)</p> Signup and view all the answers

    The cristae in the inner mitochondrial membrane serve what purpose?

    <p>Increasing surface area for energy production (B)</p> Signup and view all the answers

    Which of the following is NOT found in the mitochondrial matrix?

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

    What type of biomolecules are abundant in the inner mitochondrial membrane?

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

    What causes the inflammation associated with gout?

    <p>Phagocytosis of urate crystals by immune cells (B)</p> Signup and view all the answers

    Which statement about the function of the outer mitochondrial membrane is correct?

    <p>It facilitates certain oxidation reactions. (D)</p> Signup and view all the answers

    What is a key characteristic of I-cell disease?

    <p>Accumulation of undegraded molecules in lysosomes (B)</p> Signup and view all the answers

    What specific enzyme deficiency is associated with I-cell disease?

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

    What is contained within the mitochondrial matrix?

    <p>Enzymes for fatty acid oxidation (D)</p> Signup and view all the answers

    Which feature distinguishes the inner mitochondrial membrane from the outer mitochondrial membrane?

    <p>Presence of cristae (D)</p> Signup and view all the answers

    How are enzymes affected in individuals with lysosome-related inherited disorders?

    <p>Enzymes are absent due to the lack of acid hydrolases (C)</p> Signup and view all the answers

    What is a defining feature of peroxisomes?

    <p>They lack energy-coupled electron transport systems (D)</p> Signup and view all the answers

    Which characteristic is unique to prokaryotic cells when compared to eukaryotic cells?

    <p>Absence of membrane-bound organelles (A)</p> Signup and view all the answers

    What role does the mitochondria play in eukaryotic cells?

    <p>Site of respiration (C)</p> Signup and view all the answers

    Which statement accurately reflects a key principle of cell theory?

    <p>Each organism is composed of one or more cells. (D)</p> Signup and view all the answers

    What is a defining feature of eukaryotic cells regarding their internal organization?

    <p>Presence of membrane-bound organelles (B)</p> Signup and view all the answers

    Which type of cell does not undergo mitosis or meiosis for reproduction?

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

    In eukaryotic cells, where are the informational components collectively known as chromatin located?

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

    Which of the following organisms would be classified as prokaryotic?

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

    Which process encompasses both anabolism and catabolism within a cell?

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

    What is the size comparison between prokaryotic and eukaryotic cells?

    <p>Eukaryotic cells are generally larger than prokaryotic cells. (B)</p> Signup and view all the answers

    Which of the following statements about the respiratory system in prokaryotic cells is true?

    <p>It is closely associated with the plasma membrane. (D)</p> Signup and view all the answers

    Flashcards

    Peroxisome Function

    Peroxisomes carry out oxidation reactions, producing hydrogen peroxide (H₂O₂). Catalase destroys this peroxide. They also have a key role in fatty acid oxidation.

    Cytosol

    The fluid part of the cytoplasm, free of organelles; composed of water, enzymes, and other dissolved substances. The site of many metabolic reactions.

    Plasma Membrane

    The outer boundary of a cell that controls what enters and leaves the cell. It separates the cell's interior from the outside environment.

    Selective Permeability

    The plasma membrane's ability to control what molecules cross into or out of the cell. It allows some things to pass and prevents others.

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    Membrane Composition

    Membranes are mostly lipids (40%), proteins (60%), and small amounts of carbohydrates (1-10%).

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    Cell Membrane Carbohydrates

    Membrane carbohydrates are always attached to proteins or lipids.

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    Zellweger Syndrome

    An inherited disorder where peroxisomes may be absent.

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    Membrane and Organelles

    Eukaryotic cells have internal membranes surrounding organelles, each with specialized functions.

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    Nucleus Function

    The nucleus is the control center of the eukaryotic cell, responsible for DNA replication and RNA transcription, which is the first step in expressing genetic information.

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    Nuclear Envelope

    A double membrane structure that surrounds the nucleus, separating it from the cytosol.

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    Nuclear Pore Complexes

    Structures embedded in the nuclear envelope that control the movement of molecules, like proteins and RNA, between the nucleus and the cytoplasm.

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    Chromatin

    Coiled DNA in the nucleus that appears as a dense mass, stained darkly with certain dyes.

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    Nucleolus Function

    The nucleolus is a dense mass within the nucleus where ribosomal RNA (rRNA) synthesis occurs, and ribosome subunits are assembled.

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    Mitochondrion Function

    The mitochondrion is responsible for cellular respiration, producing energy (ATP) for the cell.

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    Mitochondrion Size

    Mitochondria vary in size, but a typical mammalian mitochondrion has a diameter of 0.2 to 0.8 μm.

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    Mitochondrion Shape

    The shape of mitochondria can change under different conditions, but they are often described as bean-shaped.

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    Number of Mitochondria

    The number of mitochondria in a cell varies depending on the cell's energy demands, from a single mitochondrion in some algae to hundreds of thousands in some protozoa.

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    Nucleoplasm

    The fluid inside the nucleus, containing various enzymes like DNA polymerases and RNA polymerases involved in DNA and RNA synthesis.

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    Outer mitochondrial membrane composition

    Primarily phospholipids and cholesterol, with many porin proteins.

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    Porin protein function

    Forms channels allowing small molecules (< 10,000 Da) to pass through the outer membrane.

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    Outer membrane proteins

    Biosynthesis of fatty acids and phospholipids, some oxidation reactions.

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    Inner mitochondrial membrane composition

    High protein content, low lipid-to-protein ratio, contains cardiolipin phospholipid, impermeable to many polar/ionic molecules.

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    Inner mitochondrial membrane folds

    Cristae, increasing surface area for metabolic processes.

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    Intermembrane space composition

    Similar ionic composition to cytosol due to outer membrane permeability.

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    Mitochondrial matrix location

    The region enclosed by the inner mitochondrial membrane.

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    Mitochondrial matrix function

    Site of citric acid cycle, fatty acid oxidation, and mitochondrial DNA/ribosome.

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    Cardiolipin

    A phospholipid abundant in the inner mitochondrial membrane.

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    Cristae

    Inward folds of the inner mitochondrial membrane that increase surface area.

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    Gout: Urate Crystals

    In gout, sharp urate crystals form in joints, triggering inflammation and pain. These crystals are ingested by phagocytes, but the process damages lysosomes, releasing inflammatory enzymes.

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    Lysosomal Storage Disease

    These genetic disorders involve the buildup of complex molecules (lipids or sugars) within cells due to missing or faulty lysosomal enzymes. This leads to cell dysfunction and potentially serious health consequences.

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    I-Cell Disease

    A rare genetic disorder where lysosomes lack almost all functional enzymes, leading to the accumulation of undegraded molecules within cells. This causes severe developmental delays and often leads to early death.

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    GlcNAc Phosphotransferase

    This enzyme adds a 'marker' (Mannose-6-Phosphate or M6P) to certain lysosomal enzymes. In I-cell disease, this enzyme is faulty, leading to a lack of M6P and the enzymes being secreted outside the cell instead of going to lysosomes.

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    Peroxisomes: Microbodies

    Small organelles present in eukaryotic cells, also known as microbodies. They lack energy-producing systems but play a vital role in oxidation reactions, producing and breaking down hydrogen peroxide. They are likely formed from the smooth ER.

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    Cell Theory

    A set of principles explaining the fundamental nature of cells as the basic unit of life. It states that all living organisms are composed of cells, cells arise from pre-existing cells, and genetic information is passed down through generations.

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    Prokaryotic Cells

    Simple cells lacking a nucleus and membrane-bound organelles, like bacteria and cyanobacteria. They are smaller and have less internal organization compared to eukaryotic cells.

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    Eukaryotic Cells

    Complex cells with a nucleus and membrane-bound organelles, found in fungi, plants, and animals. They are larger and more structurally intricate compared to prokaryotic cells.

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    What are Histones?

    Proteins that bind to DNA in eukaryotic cells, helping to condense and organize the genetic material within the nucleus.

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    What is the respiratory site in prokaryotic cells?

    In prokaryotic cells, the plasma membrane is closely associated with the respiratory system.

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    What is the respiratory site in eukaryotic cells?

    In eukaryotic cells, the mitochondria is the primary site for cellular respiration.

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    What is the function of the nucleus?

    The nucleus is the control center of the eukaryotic cell, containing the genetic material (DNA) and regulating cellular activities.

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    What is chromatin?

    The complex of DNA and proteins (histones) found within the nucleus of eukaryotic cells. It condenses into chromosomes during cell division.

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    What is Metabolism?

    The sum of all chemical reactions that occur within a living organism, encompassing both breaking down (catabolism) and building up (anabolism) processes.

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    What is Anabolism?

    The process of building up complex molecules from simpler ones, requiring energy.

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    Study Notes

    Cell and Cell Organelles

    • Cells are the fundamental units of life, forming all animal tissues, including humans.
    • When cells die, tissues perish and stop functioning.

    Cell Theory

    • Each organism is composed of cells.
    • All cells arise from other cells.
    • Genetic code is passed down from one generation to the next to keep cells functioning and create new ones.
    • Metabolism (anabolism and catabolism) encompasses the chemical events (reactions) within an organism's cells.

    Types of Cells

    • Two main types of cells exist in nature: prokaryotic and eukaryotic cells.

    Prokaryotic Cells

    • Typically smaller in size and have minimal internal organization.
    • Lack membrane-bound organelles.
    • Genetic material (DNA) is not enclosed by a nuclear membrane.
    • DNA is not complexed with histones.
    • Respiratory system is closely associated with the plasma membrane.
    • Reproduction does not involve mitosis or meiosis.
    • Examples include bacteria and cyanobacteria.

    Eukaryotic Cells

    • Larger and more complex than prokaryotic cells.
    • Have a high degree of internal structure with various membrane-bound organelles.
    • Nucleus is the site for informational components (chromatin).
    • Reproduction involves both mitosis and meiosis.
    • Respiratory site is the mitochondria.
    • Examples include fungi, plants, and animals (including humans).

    Cell Organelles: Nucleus

    • Contains over 95% of the cell's DNA.
    • Controls the eukaryotic cell.
    • Nuclear envelope: A double membrane separating the nucleus from the cytosol.
    • Nuclear pore complexes: Embedded in the nuclear envelope, regulate the movement of proteins and RNA across the nuclear envelope.
    • Chromatin: DNA in the nucleus, coiled into a dense mass.
    • Nucleolus: A second dense mass associated with the inner nuclear envelope, synthesizes ribosomal RNA (rRNA).
    • Nucleoplasm: Contains various enzymes like DNA and RNA polymerases for mRNA and tRNA synthesis.
    • Functions: DNA replication, RNA transcription, and major metabolic activity of the nucleus.

    Cell Organelles: Mitochondria

    • The "powerhouse of the cell."
    • Number: Varies greatly between cell types (e.g., some algae have one, while protozoa can have millions).
    • Size: Typically 0.2-0.8 μm in diameter.
    • Shape: Adaptable, assuming different shapes under varying metabolic conditions.
    • Mitochondrial Membranes:
      • Outer membrane: Consists mostly of phospholipids and cholesterol, containing Porin protein.
      • Inner membrane: Highly folded (cristae), abundant in proteins and cardiolipin, resistant to the passage of most polar and ionic molecules, requiring specialized transport proteins.
    • Intermembrane space: The space between the outer and inner membranes; ionic composition similar to the cytosol.
    • Mitochondrial matrix: The region enclosed by the inner membrane; contains enzymes for the citric acid cycle, fatty acid oxidation, circular DNA, ribosomes, and enzymes for mitochondrial protein synthesis. Mitochondria have their own genome.
    • Functions: Carrying out oxidation reactions producing hydrogen peroxide (H₂O₂), destroyed by the catalase enzyme.
      • β-oxidation system capable of oxidizing long-chain fatty acids (C16 to 18 or > C18).
    • Diseases: Age-related degenerative disorders (e.g., Parkinson's disease) and inherited disorder (e.g., Zellweger's syndrome) can be linked to mitochondrial dysfunction.

    Cell Organelles: Endoplasmic Reticulum (ER)

    • Extends from the cell membrane, surrounds mitochondria, and appears to connect to the Golgi apparatus.
    • Involved in protein synthesis, transport, modification, storage, and secretion.
    • Two types: Rough ER (with ribosomes) and Smooth ER (without ribosomes).
    • Rough ER roles in synthesizing membrane lipids and secretory proteins, modifying them, and transporting them throughout the cell.
    • Smooth ER's roles include lipid synthesis and modification of proteins generated in rough ER, detoxification of drugs, and other vital functions.
    • Dysfunction: Linked to neurological disorders like cerebral ischemia, sleep apnea, Alzheimer's disease, and multiple sclerosis.

    Cell Organelles: Golgi Complexes

    • Also known as Dictyosomes, these are stacks of smooth compartments in eukaryotic cells.
    • Often associated with ER.
    • Structure: Includes proximal, medial, and distal compartments.
    • Function: Sorting center for newly synthesized proteins containing signal or transit peptides (transport). Proteins lacking these peptides are rejected.
    • Subsequent Functions: Receives new proteins from ER, modifies them (e.g., attaching carbohydrates/lipids), packages them into vesicles (secretory vesicles), and transports them to their destination in/out of the cell via exocytosis.
    • Diseases related to genetic mutations in Golgi proteins and impaired membrane trafficking. (e.g., Wilson's disease).

    Cell Organelles: Lysosomes

    • Contain hydrolytic enzymes.
    • Digestive bodies within the cell.
    • Involved in digestion (breakdown) of various cellular components and foreign molecules.
    • pH lower than cytosol (optimal around 5) ensuring proper activity.
    • Active during autolysis and in autophagic processes.
    • Involved in cellular degradation within cells.
    • Diseases involving malfunction can lead to build-up and improper functioning of various cell components or diseases such as I-cell disease.

    Cell Organelles: Peroxisomes

    • Small organelles sometimes called Microbodies.
    • Present in eukaryotic cells, approximately 0.5 µm in diameter.
    • Formed by budding from smooth ER.
    • Contain oxidases, catalase, and other enzymes involved in various metabolic reactions in which hydrogen peroxide is generated and then degraded, contributing to various metabolic pathways that maintain homeostasis.
    • Deficiencies in these enzymes can result in diseases like Zellweger syndrome.

    Cell Organelles: Cytosol

    • Simplest structure of the cell.
    • Cellular fluid surrounding organelles.
    • Contains free ribosomes, often in polysome form, and many proteins.
    • Site of numerous metabolic reactions.

    Biological Membranes (Structure and Function):

    • Plasma membrane: A prototype cell membrane, separating cell contents from the external environment; this separation is necessary for life.
    • Selective permeability: The property of allowing controlled movement of molecules/ions into and out of the cell (essential for survival).
    • Membrane proteins: Integral and peripheral proteins have roles in cellular communication, and facilitated transport; they also provide structural support for cells.
    • Carbohydrates: Attached to proteins or lipids (glycoproteins and glycolipids). They are vital for cell-cell recognition and communication.

    Chemical Composition of Membranes: Lipids

    • Building blocks of cell membranes.
    • Amphipathic molecules: A polar head (attracted to water) and nonpolar tails (repelled by water).
    • Types: Fatty acids, glycerophospholipids (e.g., phosphatidylcholine, phosphatidylethanolamine), sphingolipids (e.g., sphingomyelin), and cholesterol.

    Chemical Composition of Membranes: Proteins

    • Integral membrane proteins: Embedded within the membrane, often extending across the entire structure.
    • Peripheral membrane proteins: Situated on the surface of the membrane; they can be associated with integral proteins or the lipid bilayer.

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    Explore the fundamentals of cell biology, focusing on cell theory, types of cells, and the differences between prokaryotic and eukaryotic cells. This quiz covers essential concepts that form the basis of understanding life at the cellular level, including metabolism and genetic information. Test your knowledge on how cells operate and their roles in living organisms.

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