Cell Biology Quiz: Structure and Function
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Which of the following accurately describes the modern tenet of the cell theory?

  • All living organisms are composed of one or more cells.
  • Cells are the basic unit of structure and function in all living organisms.
  • All cells arise from pre-existing cells.
  • All of the above. (correct)

    • How do developments in microscopy contribute to our understanding of cell structure?

  • Microscopy allows us to visualize the intricate details of cell organelles, which are not visible to the naked eye.
  • Microscopy techniques are constantly improving, enabling us to resolve smaller and smaller structures within cells, revealing new insights into their functionality.
  • By imaging cells at different scales, microscopy helps us understand the organization and interaction of cellular components, providing valuable information about cell function.
  • All of the above. (correct)

    • What is a primary reason that limits the size of human cells?

  • The surface area of a cell needs to be large enough to accommodate the volume of the cytoplasm.
  • The efficiency of nutrient and waste exchange across the cell membrane depends on the ratio of surface area to volume.
  • As cell size increases, the distance for diffusion of substances becomes longer, making it less efficient.
  • All of the above. (correct)

    • Which of the following is NOT a major component of a cell?

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

    What is the name of the fuzzy coat that is external to the plasma membrane, and is composed of carbohydrate moieties of glycoproteins and glycolipids?

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

    Which of the following functions is NOT attributed to the glycocalyx?

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

    Which of these factors contributed significantly to the development of the cell theory?

    <p>All of the above. (D)</p> Signup and view all the answers

    What is the primary function of microvilli?

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

    What is the approximate size of microvilli, in micrometers (μm)?

    <p>1 to 2 μm (B)</p> Signup and view all the answers

    What is the primary function of the single, non-motile primary cilium found on most cells?

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

    Where are motile cilia found in the human body?

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

    What is the name of the condition that results from defects in the structure and function of cilia?

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

    Which of the following is NOT a function of motile cilia in the respiratory tract?

    <p>Secretion of saliva (C)</p> Signup and view all the answers

    What is the primary reason why most cells are limited in size?

    <p>The need to maintain a high surface area to volume ratio for efficient exchange of materials. (C)</p> Signup and view all the answers

    What is the function of the cytoskeleton?

    <p>To provide structural support and aid in cell movement. (A)</p> Signup and view all the answers

    Which of the following is NOT a component of the cytoplasm?

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

    What is the primary function of the sodium-potassium pump?

    <p>To maintain a higher concentration of potassium ions within the cell than in the extracellular fluid. (C)</p> Signup and view all the answers

    What is the primary role of the plasma membrane?

    <p>To control the movement of substances into and out of the cell. (A)</p> Signup and view all the answers

    How many sodium ions are exchanged for potassium ions in each cycle of the sodium-potassium pump?

    <p>3:2 (C)</p> Signup and view all the answers

    What is the difference between a light microscope (LM) and a transmission electron microscope (TEM)?

    <p>LM uses light to visualize specimens, while TEM uses electrons. (A)</p> Signup and view all the answers

    What type of transport mechanism does the sodium-potassium pump utilize?

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

    What is a major difference between the surface area and volume of a cell as it increases in size?

    <p>The volume increases much more rapidly than the surface area. (B)</p> Signup and view all the answers

    Which of the following microscopy techniques produces 3D images of the surfaces of cells?

    <p>Scanning Electron Microscopy (C)</p> Signup and view all the answers

    Which of the following is NOT an example of a carrier-mediated transport process?

    <p>Simple diffusion of oxygen across the cell membrane (B)</p> Signup and view all the answers

    What is the main function of the lipid component of the plasma membrane?

    <p>To provide structural support and flexibility. (B)</p> Signup and view all the answers

    Which of the following vesicular transport processes involves engulfing large particles?

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

    What is the role of clathrin in receptor-mediated endocytosis?

    <p>It binds to receptors on the cell membrane, triggering the formation of vesicles. (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of active transport?

    <p>Depends on the concentration gradient of the transported substance (A)</p> Signup and view all the answers

    What is the process of discharging material from the cell called?

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

    Which of the following is NOT a factor that affects the rate of simple diffusion through a membrane?

    <p>Presence of a carrier protein (C)</p> Signup and view all the answers

    What is the main difference between active transport and passive transport across a cell membrane?

    <p>Active transport requires ATP, while passive transport does not. (A)</p> Signup and view all the answers

    Which of the following is an example of passive transport?

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

    How does osmosis differ from simple diffusion?

    <p>Osmosis involves the movement of only water molecules, while simple diffusion can involve any type of molecule. (B)</p> Signup and view all the answers

    What is the primary function of a flagellum?

    <p>To propel the cell through its environment (D)</p> Signup and view all the answers

    Which of these statements correctly describes the relationship between cilia and flagella?

    <p>Cilia are much shorter and more numerous than flagella. (C)</p> Signup and view all the answers

    What is the term used to describe the ability of a membrane to allow certain substances to pass through while blocking others?

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

    Which of the following accurately describes the movement of water in osmosis?

    <p>Water moves from a region of low solute concentration to high solute concentration. (C)</p> Signup and view all the answers

    What is the primary function of the plasma membrane?

    <p>To regulate the passage of substances into and out of the cell (A)</p> Signup and view all the answers

    What type of membrane protein is responsible for relaying signals within the cell after a chemical message is received?

    <p>Second messenger systems (D)</p> Signup and view all the answers

    What are the three types of gated channels?

    <p>Ligand-gated, Voltage-gated, Mechanically-gated (C)</p> Signup and view all the answers

    Which of the following is NOT a function of membrane proteins?

    <p>Synthesis of proteins and nucleic acids (C)</p> Signup and view all the answers

    What is the role of a G protein in a second messenger system?

    <p>To relay the signal to adenylate cyclase (D)</p> Signup and view all the answers

    Which type of membrane protein utilizes ATP to transport molecules across the membrane?

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

    Which of the following is an example of a cell-identity marker?

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

    What is the difference between a channel protein and a carrier protein?

    <p>Channel proteins form a continuous pore through the membrane, while carrier proteins bind and transport solutes. (B)</p> Signup and view all the answers

    What is the role of kinases in a second messenger system?

    <p>To add phosphate groups to other enzymes (B)</p> Signup and view all the answers

    Study Notes

    Introduction

    • All organisms are composed of cells
    • Cells are responsible for all structural and functional properties of a living organism
    • Understanding cells is crucial for comprehending the workings of the human body, mechanisms of disease, and rationales for therapy

    3.1 Concepts of Cellular Structure

    • The modern cell theory's tenets are discussed.
    • Cell shapes are described using descriptive terms.
    • The size range of human cells is stated. The limitations to cell size are discussed.
    • Developments in microscopy impact the understanding of cell structure.
    • The major components of a cell are outlined.

    Development of the Cell Theory

    • Cytology is the scientific study of cells, which began with Robert Hooke's observation of cork cell walls in the 17th century.
    • Theodor Schwann's work in the 19th century established that all animals are made of cells.
    • Louis Pasteur's experiments in 1859 disproved spontaneous generation, showing that cells arise only from pre-existing cells.

    Development of the Cell Theory 2

    • All organisms are composed of cells and cell products.
    • The cell is the simplest structural and functional unit of life.
    • An organism's structure and functions result from the activities of cells.
    • Cells originate only from pre-existing cells.
    • Cells of all species display biochemical similarities.

    Cell Shapes and Sizes 1

    • Approximately 200 cell types in the human body have diverse shapes.
    • Cell shapes include squamous, cuboidal, columnar, polygonal, stellate, spheroidal, discoidal, fusiform, and fibrous.
    • Cell shapes might look different based on how they're sectioned.

    Cell Shapes and Sizes 2

    • Most human cells have a diameter between 10-15 µm
    • Egg cells are considerably large (100 µm)
    • Some nerve cells can exceed 1 meter in length
    • A cell's size is limited because its volume increases faster than its surface area.

    Basic Components of a Cell 1

    • Light microscopes reveal plasma membranes, nuclei, and cytoplasm (fluid between nucleus and surface.)
    • Advanced microscopes like transmission electron microscopes offer higher resolution.
    • Scanning electron microscopes focus on surface features.

    Basic Components of a Cell 2

    • Plasma (cell) membrane: surrounds the cell; defines boundaries, made of proteins and lipids.
    • Cytoplasm: where organelles reside; cytoskeleton, stored materials, (intracellular fluid,) and extracellular fluid (fluid outside a cell)

    3.2 The Cell Surface

    • Plasma membrane structure is described.
    • Functions of lipids, proteins, and carbohydrates in the plasma membrane are explained.
    • Second-messenger systems and their role in human physiology are elaborated.
    • The glycocalyx's function and composition are also discussed.
    • The structure and function of various cell surface extensions such as microvilli, cilia, and flagella are discussed.

    The Plasma Membrane 1

    • The plasma membrane appears as parallel dark lines under electron microscopy.
    • The membrane has intracellular and extracellular faces, defining cell boundaries and controlling the transport of material into and out of the cell.

    The Plasma Membrane 3

    • The plasma membrane consists of a phospholipid bilayer embedded with proteins.

    Membrane Lipids 1

    • Lipids make up 98% of membrane molecules, mainly phospholipids (75%).
    • Phospholipids are amphipathic molecules, with hydrophilic heads facing water and hydrophobic tails facing the interior of the membrane.

    Membrane Lipids 2

    • Cholesterol (20% of membrane lipids) maintains membrane fluidity and stability, while glycolipids (5%) contribute to the glycocalyx.

    Membrane Proteins 1

    • Membrane proteins (50% of membrane weight) include integral proteins that penetrate the membrane and peripheral proteins that adhere to one side.
    • Functional regions of transmembrane proteins (hydrophilic and hydrophobic) pass through the membrane.
    • Proteins can attach to the cytoskeleton.

    Membrane Proteins 2

    • Peripheral proteins are attached to one side of the membrane, usually to the cytoskeleton.
    • Membrane protein functions include signal reception via receptors, catalysis by enzymes, transport via channels and carriers, identification tags, and cell adhesion.

    Membrane Proteins 3

    • Receptors bind chemical signals.
    • Second messengers facilitate communication between the cell exterior and interior.
    • Enzymes catalyze reactions, including producing second messengers.
    • Channels allow hydrophilic substances and water to permeate the membrane.

    Membrane Proteins 4

    • Carriers bind and transport solutes.
    • Pumps are carriers that utilize ATP.
    • Cell-identity markers (glycoproteins) identify the cell.
    • Cell-adhesion molecules link a cell to the extracellular matrix.

    Second Messengers

    • Chemical messengers, such as epinephrine, bind to surface receptors.
    • Receptors activate G proteins, relaying signals.
    • Adenylate cyclase converts ATP to cyclic AMP (cAMP), a second messenger, which activates other enzymes.
    • A series of reactions occur following the activation of the G protein.

    The Glycocalyx

    • A fuzzy, carbohydrate-rich coat on cell surfaces.
    • It is composed of glycoproteins and glycolipids with unique compositions.
    • The glycocalyx helps with protection, cell adhesion, immunity (immune response.)
    • It's crucial in processes like fertilization, defense against cancer, embryonic development, and transplant compatibility.

    Extensions of the Cell Surface - Microvilli 1

    • Microvilli are membrane extensions that increase surface area, important for absorption.
    • The brush border in absorptive cells is a densely packed collection of microvilli.
    • Microfilaments within the microvilli help absorb materials.

    Extensions of the Cell Surface - Microvilli 2

    • Various microvilli types and functions are depicted in images.

    Extensions of the Cell Surface - Cilia 1

    • Cilia are hair-like extensions, some motile others not.
    • They play critical roles in monitoring surroundings, balance, and light detection.
    • Non-motile cilia are on sensory cells of nose.
    • Motile cilia in respiratory tract, uterine tubes, and brain ventricles propel substances across surfaces.

    Extensions of the Cell Surface - Cilia 3

    • Image of cilia structure.

    Ciliary Action

    • Images showing the mechanics of ciliary movement.

    Extensions of the Cell Surface - Flagella

    • The tail of a sperm is the only example of a flagellum in humans.
    • Flagella are whip-like structures that are significantly longer than cilia.

    3.3 Membrane Transport

    • Selectively permeable membranes allow certain substances to pass through while blocking others.
    • Various mechanisms, like passive and active transport, facilitate material movement across cellular membranes.
    • Osmolarity and tonicity (e.g., hypotonic, hypertonic, isotonic) impact cell volume and are essential for cellular processes.

    Membrane Transport

    • Plasma membranes are selectively permeable, allowing some substances to pass while preventing others.
    • Passive transport (e.g., filtration, diffusion, osmosis) does not require energy.
    • Active transport and vesicular transport require energy.

    Simple Diffusion 1

    • Simple diffusion is the net movement of particles from a high to a low concentration region.
    • It is driven by random molecular motion.
    • Small, nonpolar, hydrophobic, and lipid-soluble molecules can pass through the membrane.

    Simple Diffusion 2

    • Factors affecting diffusion rate include temperature, molecular weight, steepness of concentration gradient, membrane surface area, and membrane permeability.

    Osmosis 1

    • Osmosis is the net movement of water across a selectively permeable membrane from a high to a low water concentration.
    • Solute particles that cannot penetrate the membrane draw water to them.

    Osmosis 2

    • Osmotic pressure stops osmosis. It increases if the nonpermeating solute concentration increases.
    • Reverse osmosis uses pressure to override osmotic pressure, for example in water purification.
    • The heart is an example of reverse osmosis.

    Osmolarity and Tonicity 1

    • Osmolarity refers to the number of osmoles per liter of solution.
    • Body fluids, including blood plasma, tissue fluid, and intracellular fluid, have an osmolarity of 300 mOsm.

    Osmolarity and Tonicity 2

    • Tonicity refers to how a surrounding solution (bath) affects cell volume.
    • A hypotonic solution has a lower solute concentration than the cell, causing water entry and cell swelling.
    • A hypertonic solution has a higher solute concentration, leading to water loss and cell shrinking.
    • An isotonic solution has an equal solute concentration to the cell, maintaining no change in cell volume.

    Effects of Tonicity on RBCs

    • Images illustrating the effects of hypotonic, isotonic, and hypertonic solutions on red blood cells.

    Carrier-Mediated Transport 1

    • Carrier proteins facilitate transport of solutes into and out of cells.
    • These proteins exhibit specificity, transporting only particular solutes.
    • The rate of transport is limited by the transport maximum (Tm), where all carriers are occupied.

    Carrier-Mediated Transport 2

    • Various Carrier Types (uniport, symport, antiport) are described.

    Carrier-Mediated Transport 3

    • Facilitated diffusion, a type of carrier-mediated transport, occurs down the concentration gradient and does not require ATP.
    • The solute binds to the carrier, the carrier changes conformation, and the solute is released on the other side of the membrane.

    Carrier-Mediated Transport 4

    • Active transport moves solutes against their concentration gradient; ATP is required.
    • Examples such as calcium pumps and sodium-potassium pumps are illustrated.

    Carrier-Mediated Transport 5

    • The sodium-potassium pump (Na⁺-K⁺ pump) is a critical example of active transport, maintaining intracellular and extracellular sodium and potassium gradients. Half of daily caloric expenditure is used for this process.

    Vesicular Transport 1

    • Vesicular transport moves large substances through membrane. Different types described.

    Vesicular Transport 2

    • Receptor-mediated endocytosis is a more selective form of endocytosis, enabling cells to take up specific molecules.
    • Molecules bind to receptors, forming coated vesicles containing clathrin, then transported to the cytosol for use.
    • Uptake of LDL from the bloodstream is an illustration of this mechanism.

    3.4 The Cell Interior

    • Cytoskeleton functions and its composition are described.
    • Functions, structure, and descriptions of the organelles present in cells are illustrated.
    • Cell inclusions are distinguished from organelles.

    The Cytoskeleton 1

    • Cytoskeleton is a network of filaments and proteins.
    • It is involved in determining the cell shape and maintaining structure, also directs movement of materials inside cells.
    • Composed of microfilaments, intermediate fibres and microtubules.

    Organelles

    • Organelles are the internal structures of cells.
    • Membranous organelles, such as the nucleus, mitochondria, lysosomes, peroxisomes, endoplasmic reticulum, and Golgi complex, are described.
    • Non-membranous organelles, such as ribosomes, centrosomes, centrioles, and basal bodies are also described.

    The Nucleus 1

    • The nucleus is generally the largest organelle.
    • Most cells have a single nucleus.
    • Some cells have more than one nucleus or have no nucleus at all.
    • The nuclear envelope is a double membrane with nuclear pores.

    The Nucleus 2

    • The nuclear envelope is supported by the nuclear lamina, a web of protein filaments.
    • The material within the nucleus is the nucleoplasm, composed of chromatin, and nucleoli, where ribosomes are made.

    The Nucleus as Seen by Electron Microscope

    • Images showing the internal and external views of a nucleus, labelled with its major components.

    Endoplasmic Reticulum 1

    • The endoplasmic reticulum (ER) is a system of channels enclosed by membranes.
    • The rough ER is associated with ribosomes and produces phospholipids and proteins for cell membranes.

    Endoplasmic Reticulum 2

    • Smooth ER lacks ribosomes and is involved in synthesizing steroids, lipids, detoxifying substances (e.g., alcohol), and storing calcium.

    Endoplasmic Reticulum 3

    • Images illustrating the structure of rough and smooth endoplasmic reticulum.

    Ribosomes

    • Ribosomes are small granules of protein and RNA found in nucleoli, the cytoplasm, and on rough ER.
    • Roles involve reading genetic codes and assembling amino acids into proteins.

    Golgi Complex 1

    • The Golgi complex processes, modifies, and packages proteins and lipids received from the ER.
    • Proteins may be sorted, glycosylated, and packaged into vesicles for different destinations.

    Golgi Complex 2

    • Images depicting the morphology of the golgi complex.

    Lysosomes

    • Lysosomes are membrane-bound sacs containing enzymes involved in intracellular digestion.
    • They break down various molecules and structures within the cell.
    • Examples of lysosomal functions include autophagy (digestion of worn-out organelles) and autolysis (cell self-digestion).

    Mitochondria

    • Mitochondria are organelles responsible for ATP synthesis, the molecule for energy transfer in cells.
    • Cellular energy is extracted and stored in ATP from organic molecules.
    • Mitochondrial membranes, including the inner cristae, play a critical role in ATP synthesis.

    A Mitochondrion

    • Visual representation of a mitochondrion's structure.

    Evolution of the Mitochondrion

    • Mitochondria are believed to be remnants of bacteria, integrated into other cells for energy production.
    • Their DNA is inherited maternally and has a faster mutation rate than nuclear DNA.

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    Test your knowledge on cell theory and the structure of cells with this quiz. Explore important concepts such as microvilli, cilia, and the glycocalyx. Perfect for students studying cell biology or related subjects.

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