Cell Membrane Structure and Function
42 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the thickness of the plasma membrane, and why is it only visible by electron microscopy?

  • 8 nm because it is highly fibrous
  • 10 nm with a trilaminar appearance
  • 5 nm due to its composition
  • 7.5-10 nm and it has a trilaminar appearance (correct)

    • Which component of the plasma membrane helps regulate its fluidity?

  • Phospholipids
  • Integral proteins
  • Cholesterol (correct)
  • Glycoproteins

    • How do integral proteins differ from peripheral proteins in the plasma membrane?

  • Integral proteins cannot be removed from the membrane, while peripheral proteins can.
  • Integral proteins are loosely attached to the membrane.
  • Integral proteins only exist on the cytoplasmic side of the membrane.
  • Integral proteins span the lipid bilayer, while peripheral proteins are not embedded. (correct)

    • What is the role of glycoproteins in the plasma membrane?

    <p>They form the Glycocalyx.</p> Signup and view all the answers

    Which type of transport requires enzymes and energy to move substances across the plasma membrane?

    <p>Active transport</p> Signup and view all the answers

    Which of the following best describes the hydrophobic properties of phospholipids in the plasma membrane?

    <p>They are directed toward the middle of the bilayer.</p> Signup and view all the answers

    What is primarily transported through selective transport in the plasma membrane?

    <p>Glucose and amino acids</p> Signup and view all the answers

    What feature is characteristic of the trilaminar appearance of the plasma membrane?

    <p>Two electron-dense lines separated by an electron-lucent layer</p> Signup and view all the answers

    What is one of the primary roles of free ribosomes in a cell?

    <p>Synthesize cytoplasmic and cytoskeletal proteins</p> Signup and view all the answers

    Which statement about ribosomes is accurate?

    <p>Ribosomes consist of two subunits made of rRNA and proteins.</p> Signup and view all the answers

    What type of ribosomes are found attached to the endoplasmic reticulum?

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

    Which of the following statements about mitochondrial DNA is correct?

    <p>It enables mitochondria to divide based on the cell's energy needs.</p> Signup and view all the answers

    What characteristic differentiates attached ribosomes from free ribosomes?

    <p>Attached ribosomes synthesize proteins destined for secretion.</p> Signup and view all the answers

    What is the primary function of mitochondria in cells?

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

    Which type of endocytosis is characterized by the engulfing of large particles such as bacteria?

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

    What do the number of mitochondria in a cell primarily depend on?

    <p>Activity level of the cell</p> Signup and view all the answers

    Which microscopy technique is best suited for visualizing the double membranous structure of mitochondria?

    <p>Electron microscopy</p> Signup and view all the answers

    What is the role of cristae within mitochondria?

    <p>To increase the surface area for energy production</p> Signup and view all the answers

    Which of the following components is NOT found within a mitochondrion?

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

    Which staining technique is primarily used to visualize DNA and ribosomes in cells?

    <p>Hematoxylin staining</p> Signup and view all the answers

    Which statement accurately characterizes the role of mitochondria in muscle cells?

    <p>Mitochondria can divide and increase in number depending on cell activity.</p> Signup and view all the answers

    Which of the following best describes the role of ribosomes in protein synthesis?

    <p>Ribosomes synthesize proteins for both cell use and secretion.</p> Signup and view all the answers

    What is the primary difference in function between free ribosomes and attached ribosomes?

    <p>Free ribosomes synthesize cytoplasmic and cytoskeletal proteins, while attached ribosomes synthesize proteins for secretion.</p> Signup and view all the answers

    Which of these statements about mitochondrial DNA is accurate?

    <p>Mitochondrial DNA is exclusively inherited from the mother.</p> Signup and view all the answers

    How are ribosomes structurally characterized?

    <p>Ribosomes consist of two subunits made from rRNA and various proteins.</p> Signup and view all the answers

    What is a critical reason for the aggregation of ribosomes leading to basophilia in the cytoplasm?

    <p>The accumulation of ribosomal RNA contributes to intense staining properties.</p> Signup and view all the answers

    What is the primary function of proteoglycans in the plasma membrane?

    <p>To form the glycocalyx and aid in cell recognition.</p> Signup and view all the answers

    Which of the following best describes the role of cholesterol in the plasma membrane?

    <p>It helps in maintaining membrane fluidity and stability.</p> Signup and view all the answers

    What distinguishes transmembrane proteins from peripheral proteins?

    <p>Transmembrane proteins span the lipid bilayer completely.</p> Signup and view all the answers

    What type of molecules typically utilize selective transport through the plasma membrane?

    <p>Hormones and specific nutrients requiring receptors.</p> Signup and view all the answers

    What feature of the plasma membrane assists in the formation of a barrier to polar molecules?

    <p>The hydrophobic tails of phospholipids.</p> Signup and view all the answers

    How are microvilli associated with the plasma membrane?

    <p>They increase surface area for absorption.</p> Signup and view all the answers

    What cellular structure primarily participates in the synthesis of membrane proteins?

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

    Which of the following statements about the plasma membrane is accurate regarding its selective permeability?

    <p>It selectively permits the entry of certain molecules based on their size and polarity.</p> Signup and view all the answers

    What is the primary function of the cristae in mitochondria?

    <p>To increase the surface area for ATP production</p> Signup and view all the answers

    Which type of endocytosis is specifically for the uptake of fluids and small molecules?

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

    How do the numbers of mitochondria in a cell typically adjust?

    <p>They are influenced by mitochondrial division and energy needs</p> Signup and view all the answers

    Which microscopy technique is most effective for visualizing the specifics of mitochondrial structure?

    <p>Transmission electron microscopy</p> Signup and view all the answers

    What role do mitochondria primarily play in cellular energy production?

    <p>Aerobic respiration in the mitochondrial matrix</p> Signup and view all the answers

    What distinguishes the outer membrane of mitochondria from the inner membrane?

    <p>The outer membrane is smooth and not folded</p> Signup and view all the answers

    The hematoxylin and eosin (H&E) staining technique is characterized by which of the following properties?

    <p>Hematoxylin stains basic structures blue, while eosin stains acidic structures red</p> Signup and view all the answers

    What is a key feature of receptor-mediated endocytosis?

    <p>It involves integral proteins that bind to specific large molecules</p> Signup and view all the answers

    Study Notes

    Cell Membrane

    • The cell membrane is the outer limiting membrane that surrounds the cell.
    • It is also known as the plasma membrane or plasmalemma.
    • It is 7.5-10 nm thick and visible only by electron microscopy (E.M.).
    • It has a trilaminar appearance with two electron-dense lines separated by an electron-lucent one.
    • It is composed of phospholipids, cholesterol, proteins, and carbohydrates.
    • Phospholipids are organized into a double layer (bilayer) with hydrophilic heads facing the water and hydrophobic tails directed toward the middle.
    • Cholesterol regulates the fluidity of the phospholipid bilayer and stabilizes it.
    • Integral proteins are firmly embedded in the lipid bilayer and not easily extracted.
    • Peripheral proteins are loosely attached to the outer or inner membrane surfaces and easily extracted.
    • Trans-membrane proteins completely span the lipid bilayer and are usually attached to microfilaments in the cytoplasmic side.
    • Carbohydrates are located on the external surface of the membrane, forming the Cell Coat or Glycocalyx.

    Functions of Cell Membrane

    • Passive diffusion: for gases and ions, according to concentration gradient.
    • Active transport: for amino acids, glucose, and fatty acids, needs enzymes and energy.
    • Selective transport: for hormones, drugs, and bacteria, needs receptors and energy.
    • Phagocytosis: for solid (cell eating), example: macrophages can engulf bacteria.
    • Pinocytosis: for fluid (cell drinking).
    • Receptor-mediated endocytosis: for large molecules, needs receptors, example: protein hormones and some drugs.
    • Exocytosis: opposite to phagocytosis, the cell expels waste products.
    • Adhesive function: for adjacent cells.
    • Immunity: recognizes the cell of its own type and foreign cells.
    • Participates in the formation of the basement membrane.

    Mitochondria

    • Membranous organelles containing enzymes specialized for the production of energy (ATP).
    • It is the power house of the cell.
    • Mitochondria vary in size and shape, being elongated, rod-shaped, or spherical.
    • The number of mitochondria is variable depending on the cell's activity, with liver cells containing numerous mitochondria and lymphocytes very few.
    • The number of mitochondria is modified by mitochondrial division.
    • Mitochondria are mobile and localize at sites of maximum energy requirement, for example, between myofibrils in cardiac muscle cells.

    Light Microscopy (L/M) of Mitochondria

    • Hematoxylin (H): basic (alkaline), stains blue, reacts with acidic structures inside the cell.
    • Eosin (E): acidic, stains red, reacts with basic structures inside the cell, usually cytoplasm.
    • Cytoplasm rich in ribosomes and RER is basophilic, for example, plasma cells.
    • Cytoplasm rich in mitochondria is acidophilic, for example, renal tubules.

    Electron Microscopy (E.M.) of Mitochondria

    • The mitochondria is a double-membranous organelle.
    • Each mitochondrion consists of four compartments:
      • Outer membrane: smooth, no folds.
      • Inner membrane: forms complex folds called cristae, the number of cristae increases in more active cells.
      • Intermembranous space: between inner and outer membrane.
      • Mitochondrial matrix: contains mitochondrial DNA and ribosomes.

    Functions of Mitochondria

    • Provide the cell with ATP by aerobic respiration occurring within the matrix and on the inner membrane.
    • The mitochondrial matrix contains DNA for division and ribosomes for protein synthesis.

    Ribosomes

    • Non-membranous organelles.
    • The ribosome is the protein factory of the cell.
    • They are very small (20-30 nm in diameter) and too small to be seen by L.M.
    • Aggregation of ribosomes leads to basophilia of the cytoplasm due to rRNA.
    • Ribosomes are small electron-dense particles composed of two subunits: small and large subunits.
    • The two subunits are formed of rRNA and about 80 different protein molecules.

    Types of Ribosomes

    • Free ribosomes: many ribosomes bound to a single mRNA molecule, synthesize proteins for use by the cell (cytoplasmic and cytoskeletal proteins).
    • Attached ribosomes (polyribosomes or polysomes): single ribosome or polysomes attached to the surface of the endoplasmic reticulum forming RER, synthesize proteins to be secreted outside the cell as secretory proteins, or to remain in the cytoplasm as primary lysosomes.

    Cell Membrane

    • The outer limiting membrane surrounding the cell
    • 7.5-10 nm thick
    • Visible only by electron microscopy
    • Appears trilaminar: two electron dense lines (black) separated by an electron lucent one (white)
    • Composed of phospholipids, cholesterol, proteins, and carbohydrates
    • Phospholipids form a double layer (bilayer) with hydrophilic heads facing outwards and hydrophobic tails inwards
    • Cholesterol stabilizes the phospholipid bilayer
    • Integral proteins are firmly embedded and not easily extracted, while peripheral proteins are loosely attached
    • Transmembrane proteins span the lipid bilayer and can act as channels
    • Carbohydrates form a "cell coat" or "glycocalyx" on the external surface

    Functions

    • Passive diffusion for gases and ions based on concentration gradients
    • Active transport for amino acids, glucose, and fatty acids requiring enzymes and energy
    • Selective transport for hormones, drugs, and bacteria needing receptors and energy
    • Phagocytosis: engulfing solid particles (e.g., macrophages engulfing bacteria)
    • Pinocytosis: engulfing fluids (cell drinking)
    • Receptor-mediated endocytosis: engulfing large molecules using receptors (integral proteins)
    • Exocytosis: expelling waste products, opposite to phagocytosis
    • Adhesive function: for adjacent cells
    • Immunity: recognizing self and foreign cells
    • Participates in basement membrane formation

    Mitochondria

    • Membranous organelles containing enzymes for energy (ATP) production
    • Powerhouse of the cell
    • Vary in size and shape (elongated, rod-shaped, or spherical)
    • Number varies depending on cell activity (e.g., liver cells have many, lymphocytes have few)
    • Mitochondria are mobile and localize at sites of high energy demand (e.g., between myofibrils in cardiac muscle cells)
    • Visible with light microscopy (L/M) using H&E staining
    • Basophilic (blue) due to DNA and RNA
    • Acidophilic (red) due to abundance of mitochondria
    • Visible with electron microscopy (E.M) and appears double membranous
    • Composed of four compartments: outer membrane, inner membrane, intermembranous space, and mitochondrial matrix
    • Outer membrane is smooth without folds
    • Inner membrane forms folds called cristae, with more cristae in active cells
    • Intermembranous space is between the inner and outer membrane
    • Mitochondrial matrix contains DNA (allowing division) and ribosomes (synthesizing some of its own proteins)

    Functions

    • Provide ATP through aerobic respiration occurring within the matrix and on the inner membrane
    • Contain DNA for division and ribosomes for protein synthesis

    Ribosomes

    • Non-membranous organelles
    • Protein factories of the cell
    • Small (20-30 nm diameter)
    • Individually too small for L/M, but aggregations (polyribosomes or polysomes) are basophilic (blue)
    • In E.M., they appear as small electron-dense particles
    • Composed of two subunits: small and large
    • Subunits are made of rRNA and proteins

    Types

    • Free ribosomes (polyribosomes or polysomes): multiple ribosomes bound to a single mRNA molecule, synthesize proteins for cell use (cytoplasmic and cytoskeletal)
    • Attached ribosomes (to endoplasmic reticulum): single ribosomes or polysomes attached to the surface of ER, synthesize proteins for secretion outside the cell, remaining in cytoplasm as primary lysosomes

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Histology L1 PDF

    Description

    Explore the intricate structure and components of the cell membrane in this quiz. Learn about phospholipids, proteins, and the role of cholesterol in maintaining membrane fluidity. Test your understanding of the cell's outer limiting membrane, also known as the plasma membrane.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser