Cell structures and functions
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Questions and Answers

Which type of substances easily diffuse across a cell membrane?

  • Polar substances
  • Hydrophobic substances (correct)
  • Hydrophilic substances
  • Charged substances

    • What type of transport proteins help specific substances like sugar, amino acids, and ions to diffuse across the membrane?

  • Inactive transport proteins
  • Passive transport proteins
  • Facilitated transport proteins (correct)
  • Non-specific transport proteins

    • Why is the diffusion of water through a membrane's hydrophobic interior relatively slow?

  • Water is polar (correct)
  • Aquaporins slow down water diffusion
  • Water is non-polar
  • The hydrophobic interior repels water molecules

    • Which mechanism is used by a cell to move bulky molecules out of the cell?

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

    In which process does a cell use energy to move solutes against their concentration gradient?

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

    What is the function of tight junctions in animal tissues?

    <p>Fasten cells together preventing fluid leakage</p> Signup and view all the answers

    Where are many embedded protein molecules that function in ATP synthesis found?

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

    What is the main function of anchoring junctions in animal tissues?

    <p>Fasten cells together preventing fluid leakage</p> Signup and view all the answers

    What is the primary purpose of thylakoids in chloroplasts?

    <p>Trap solar energy with green chlorophyll molecules</p> Signup and view all the answers

    What type of molecules can flow through gap junctions between cells?

    <p>Ions or small molecules</p> Signup and view all the answers

    What is the main characteristic of diffusion?

    <p>Particles move down their concentration gradient</p> Signup and view all the answers

    How do molecules of dye typically move in a system involving diffusion?

    <p>Move randomly in all directions</p> Signup and view all the answers

    In the process of osmosis, what determines the direction of water movement across a selectively permeable membrane?

    <p>Difference in solute concentrations on either side of the membrane</p> Signup and view all the answers

    How does diffusion differ from active transport?

    <p>Active transport moves substances against their concentration gradient</p> Signup and view all the answers

    If a selectively permeable membrane separates two solutions with different solute concentrations, what would happen in terms of water movement through osmosis?

    <p>Water will flow from the solution with higher solute concentration to the one with lower solute concentration</p> Signup and view all the answers

    What happens to a cell in a hypotonic solution?

    <p>Water molecules move into the cell, causing it to expand and possibly burst.</p> Signup and view all the answers

    How does an isotonic solution affect cell volume?

    <p>Cell volume will not change.</p> Signup and view all the answers

    What is the main factor that determines tonicity of a solution?

    <p>Relative solute concentration to that inside the cell</p> Signup and view all the answers

    In a hypertonic environment, what happens to plant cells?

    <p>They are flaccid (plasmolyzed).</p> Signup and view all the answers

    Why is osmoregulation important for animal cells in non-isotonic environments?

    <p>To control water balance and prevent bursting or shrinking.</p> Signup and view all the answers

    Which feature of the plasma membrane is critical for the origin of life?

    <p>Self-assembly of phospholipids</p> Signup and view all the answers

    What type of molecules are known to diffuse easily through the plasma membrane?

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

    What is a characteristic of passive transport across the plasma membrane?

    <p>Movement of molecules from high to low concentration</p> Signup and view all the answers

    Which process involves the spontaneous formation of membrane-enclosed collections of molecules?

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

    In osmosis, water molecules move across a selectively permeable membrane from an area of _______ concentration to an area of _______ concentration.

    <p>Higher; lower</p> Signup and view all the answers

    Which organelle is the largest component of the endomembrane system?

    <p>Rough ER</p> Signup and view all the answers

    Which type of ER is abundant in cells that secrete proteins?

    <p>Smooth ER</p> Signup and view all the answers

    What is the main function of rough endoplasmic reticulum (Rough ER)?

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

    Which organelle is responsible for the distribution, storage, and export of molecules within a eukaryotic cell?

    <p>Golgi apparatus</p> Signup and view all the answers

    Which organelle is characterized by tiny vesicles transferring membrane segments between membranes?

    <p>Golgi apparatus</p> Signup and view all the answers

    Which organelle in the cell fuses with food vacuoles to digest food?

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

    What is the main function of contractile vacuoles in freshwater protists?

    <p>Pump excess water out of cells</p> Signup and view all the answers

    In a cell, which organelle acts as a recycling center by breaking down damaged organelles?

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

    Which organelle found in mature plant cells holds organic compounds and water?

    <p>Central vacuole</p> Signup and view all the answers

    What organelle contains pigments and poisons that protect the plant?

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

    Which type of vacuole forms as a cell ingests food?

    <p>Food vacuole</p> Signup and view all the answers

    What is the primary function of transport vesicles in the cell?

    <p>Transporting molecules between organelles</p> Signup and view all the answers

    Which organelle is derived from the endoplasmic reticulum (ER) and Golgi apparatus?

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

    What function do central vacuoles perform in many mature plant cells?

    <p>Hold organic compounds &amp; water</p> Signup and view all the answers

    What is the role of rough endoplasmic reticulum in the cell?

    <p>Fusing with other vesicles to be recycled within a cell</p> Signup and view all the answers

    Study Notes

    Endomembrane System

    • The endomembrane system is a network of connected membranes and organelles that work together to synthesize, distribute, store, and export molecules.
    • The system includes the nuclear envelope, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

    Endoplasmic Reticulum (ER)

    • The ER is the largest component of the endomembrane system and is an extensive network of flattened sacs and tubules.
    • There are two types of ER: rough ER and smooth ER.
    • Rough ER has bound ribosomes that stud the outer surface of the membrane, whereas smooth ER lacks attached ribosomes.
    • Rough ER is involved in the synthesis of proteins that are to be secreted or inserted into membranes.
    • Smooth ER is involved in various metabolic processes, including the production of lipids, oils, and steroids.

    Diffusion

    • Diffusion is the passive transport of particles from an area of higher concentration to an area of lower concentration.
    • Net diffusion continues until equilibrium is reached, where there is no net change in concentration on either side of the membrane.

    Osmosis

    • Osmosis is the diffusion of water across a selectively permeable membrane.
    • If a membrane separates two solutions with different solute concentrations, water will cross the membrane, moving down its concentration gradient, until the solute concentration on both sides is equal.

    Facilitated Diffusion

    • Facilitated diffusion is the transport of specific molecules down their concentration gradient using transport proteins.
    • Hydrophobic substances can easily diffuse across a cell membrane, but polar or charged substances require specific transport proteins to cross the membrane.

    Active Transport

    • Active transport is the movement of solutes against their concentration gradient, requiring energy input from ATP.
    • Transport proteins use ATP to pump solutes across the membrane, often against their concentration gradient.

    Exocytosis and Endocytosis

    • Exocytosis is the process of exporting bulky molecules out of a cell, while endocytosis is the process of importing molecules into a cell.
    • Phagocytosis is a type of endocytosis where the cell engulfs large particles or cells.

    Tonicity

    • Tonicity refers to the ability of a surrounding solution to cause a cell to gain or lose water.
    • Isotonic solutions have the same solute concentration as the cell, whereas hypotonic solutions have a lower solute concentration, and hypertonic solutions have a higher solute concentration.

    Cell Junctions

    • There are three types of cell junctions in animal tissues: tight junctions, anchoring junctions, and gap junctions.
    • Tight junctions prevent leakage of fluid between cells, anchoring junctions fasten cells together, and gap junctions allow small molecules to pass between cells.

    Cell Wall

    • Plant cells have a rigid cell wall that provides support and protection.
    • The cell wall is composed primarily of cellulose, with other polysaccharides and proteins embedded in the matrix.

    Plasma Membrane

    • The plasma membrane is a fluid mosaic model, with a phospholipid bilayer embedded with protein molecules.
    • The plasma membrane exhibits selective permeability, allowing certain molecules to pass through while keeping others out.
    • Phospholipids spontaneously self-assemble into simple membranes, a critical step in the origin of life.

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    Cell Structures and Functions PDF

    Description

    Learn about the interconnected membranes within a eukaryotic cell that make up the endomembrane system. Discover how organelles like the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles work together in synthesis, distribution, storage, and export of molecules.

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