Medical Biology: chapter 2
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Questions and Answers

Which statement about primary active transport is true?

  • It does not require energy from ATP hydrolysis.
  • It only involves F-class and V-class transporters.
  • It operates without any ion gradients.
  • It directly pumps ions against their concentration gradients. (correct)

    • What distinguishes symporters from antiporters in secondary active transport?

  • Symporters transport molecules in different directions.
  • Antiporters do not rely on ion gradients.
  • Antiporters utilize ATP directly for transport.
  • Symporters transport substrates in the same direction. (correct)

    • Which class of ATPase primarily pumps protons against their concentration gradient?

  • Sodium-potassium ATPase
  • P-class transporters
  • ABC-class transporters
  • F-class transporters (correct)

    • Which of the following statements correctly describes secondary active transport?

    <p>It does not have transport proteins with ATPase activity.</p> Signup and view all the answers

    Which type of transporter would move drugs and xenobiotics against their gradient?

    <p>ABC-class transporters</p> Signup and view all the answers

    Which best describes the relationship between primary and secondary active transport?

    <p>Secondary transport relies on the gradients established by primary transport.</p> Signup and view all the answers

    Which process involves the movement of molecules from an area of high concentration to an area of low concentration without the use of energy?

    <p>Simple diffusion</p> Signup and view all the answers

    Which component of cell membranes is primarily responsible for maintaining membrane stability and facilitating cell-cell interactions?

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

    What type of transport requires membrane proteins but does not consume energy?

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

    What is the role of ion channels in facilitated diffusion?

    <p>They bind ions specifically and move them with the concentration gradient.</p> Signup and view all the answers

    Which form of transport allows the uptake of large molecules into the cell?

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

    What defines the selective permeability of the plasma membrane?

    <p>It permits specific substances to cross while blocking others.</p> Signup and view all the answers

    Which mechanism primarily facilitates the entry of water into cells?

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

    How do glycoproteins contribute to human blood-group antigen recognition?

    <p>They act as recognition sites for antibodies.</p> Signup and view all the answers

    Which one of the following statements is true regarding passive transport?

    <p>It can occur through mechanisms like simple diffusion and facilitated diffusion.</p> Signup and view all the answers

    Which type of bulk transport is used for the uptake of fluid and small particles?

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

    What primarily drives the movement of substrates against their concentration gradient in secondary active transport?

    <p>Ion gradient energy</p> Signup and view all the answers

    Which characteristic is true about symporters in cotransport?

    <p>They facilitate the movement of substrates in the same direction</p> Signup and view all the answers

    What is the primary structural feature of cell membranes as described in the fluid mosaic model?

    <p>Dynamic mix of lipids and proteins</p> Signup and view all the answers

    Which type of lipid is characterized by having a glycerol backbone, two fatty acids, and a phosphate group?

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

    What role does cholesterol play in the structure of cell membranes?

    <p>Maintains membrane fluidity and stability</p> Signup and view all the answers

    What determines the asymmetrical distribution of lipids and proteins in a cell membrane?

    <p>Specific trafficking mechanisms and functions</p> Signup and view all the answers

    What types of proteins are primarily synthesized on free ribosomes?

    <p>Proteins that remain in the cytosol</p> Signup and view all the answers

    What is a key function of the carbohydrate groups on glycoproteins and glycolipids?

    <p>Facilitate cell-to-cell recognition and signaling</p> Signup and view all the answers

    What feature distinguishes antiporters from other transport proteins in membrane transport?

    <p>Facilitating the exchange of substrates in opposite directions</p> Signup and view all the answers

    What is the primary function of transport proteins in the cell membrane?

    <p>Facilitating selective passage of specific molecules</p> Signup and view all the answers

    Which of the following statements about the composition of cells is accurate?

    <p>Water constitutes around 70% of total cell mass.</p> Signup and view all the answers

    In terms of their genetic material, which type of cells have a significant difference?

    <p>Eukaryotic cells contain DNA as part of their structure.</p> Signup and view all the answers

    Which of the following organic molecules primarily serves as an energy source for immediate cell needs?

    <p>Simple carbohydrates</p> Signup and view all the answers

    What do proteins in cells primarily serve to do?

    <p>Facilitate enzymatic reactions and provide structural support</p> Signup and view all the answers

    Which statement correctly describes the differences between prokaryotic and eukaryotic cells?

    <p>Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not.</p> Signup and view all the answers

    Which types of molecules are categorized as nucleic acids?

    <p>Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)</p> Signup and view all the answers

    What role do enzymes specifically play in the functioning of cells?

    <p>Convert cellular molecules into forms that meet energy needs</p> Signup and view all the answers

    Which of the following best describes the level of complexity of eukaryotic cells compared to prokaryotic cells?

    <p>Eukaryotic cells are more complex due to the presence of organelles.</p> Signup and view all the answers

    What is the primary driving force behind the simple diffusion of particles?

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

    Which type of proteins are essential for the movement of water through the plasma membrane?

    <p>Water channel proteins</p> Signup and view all the answers

    In facilitated diffusion, how do transmembrane proteins assist in the transport of molecules?

    <p>By binding specifically to certain ligands</p> Signup and view all the answers

    What is the process called that moves molecules against their concentration gradient using energy?

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

    Which characteristic defines the action of ion channels in the plasma membrane?

    <p>They transport ions only along their concentration gradient</p> Signup and view all the answers

    How does osmosis differ from simple diffusion?

    <p>Osmosis specifically involves water movement</p> Signup and view all the answers

    During facilitated diffusion via a glucose transporter, how is the affinity denoted?

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

    What defines the semi-permeable nature of the plasma membrane?

    <p>It selectively allows certain molecules through while blocking others</p> Signup and view all the answers

    In passive transport, which factor limits the rate of solute transport across membranes?

    <p>Affinity between transport protein and solute</p> Signup and view all the answers

    What role do amphipathic phospholipids play in membrane diffusion?

    <p>They help regulate the specificity of transport</p> Signup and view all the answers

    Study Notes

    Cell Membranes and Organelles

    • Cell membranes are composed of a phospholipid bilayer.
    • Phospholipids are arranged with their hydrophilic heads facing the watery environment and their hydrophobic tails facing inward.
    • The fluid mosaic model describes cell membranes as a fluid structure with embedded proteins.
    • Cell membranes act as barriers, regulate transport, and provide a surface for cell signaling.

    Main Membrane Lipids

    • Major membrane lipids include phosphoglycerides, sphingolipids, and glycolipids.
    • Phosphoglycerides are composed of glycerol, fatty acids, and a phosphate group.
    • Sphingolipids are based on sphingosine, a long-chain amino alcohol.
    • Glycolipids have sugar residues attached to lipids.
    • Cholesterol is an amphipathic molecule that interacts with water and helps regulate membrane fluidity, thickness, and curvature.
    • Some prokaryotes, like Mycoplasma, have cholesterol in their cell membranes but lack a cell wall.

    Membrane Proteins

    • Membrane proteins are embedded within the cell membrane and perform various functions.
    • Integral proteins span the membrane, while peripheral proteins are associated with one side of the membrane.
    • Carbohydrate groups on glycoproteins and glycolipids are important for cell recognition and adhesion.
    • Asymmetrical distribution of lipids and proteins gives the cell membrane polarity and plays a crucial role in cellular processes.
    • While some membrane phospholipids and proteins can flip-flop, others can only move laterally within the membrane.

    Membrane Transport

    • Passive transport occurs without energy input and moves molecules down their concentration gradient.
    • Simple diffusion allows small, nonpolar molecules to cross the membrane directly.
    • Facilitated diffusion utilizes membrane proteins (ion channels or transporters) to facilitate the movement of specific molecules.
    • Osmosis is the movement of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.
    • Active transport requires energy to move molecules against their concentration gradient.
    • Primary active transport utilizes ATP hydrolysis to directly power the transport of molecules.
    • Secondary active transport utilizes the energy stored in ion gradients established by primary active transport to move other molecules.
    • Cotransporters are involved in secondary active transport and can be either symporters or antiporters.
    • Symporters transport two substrates in the same direction across the membrane.
    • Antiporters transport two substrates in opposite directions across the membrane.

    Cells

    • Cells are the basic unit of life and are surrounded by a plasma membrane.
    • Prokaryotic cells are simple cells lacking a nucleus and other membrane-bound organelles.
    • Eukaryotic cells are more complex and have a nucleus and other membrane-bound organelles.
    • All cells contain a cell membrane, genetic material (DNA), and cytoplasm.

    Cellular Components

    • Water is the most abundant molecule in cells.
    • Nucleic acids (DNA and RNA) are responsible for storing and expressing genetic information.
    • Proteins perform a wide range of functions, including catalysis and structural support.
    • Carbohydrates serve as energy sources and structural components.
    • Glycoproteins and glycolipids influence cell recognition and adhesion.

    Transport of Ions and Small Molecules:

    • Simple diffusion: Movement of particles from an area of high concentration to an area of low concentration.
    • Facilitated diffusion: Movement of ions or small molecules across a membrane with the help of a transport protein.
    • Active transport: Movement of molecules across a membrane against their concentration gradient, requiring energy.

    Bulk Transport:

    • Phagocytosis: The process of engulfing large particles, such as bacteria.
    • Endocytosis: The process of taking in material from outside the cell by forming vesicles.
    • Pinocytosis: The uptake of fluids and small molecules by the cell.
    • Receptor-mediated endocytosis: The uptake of specific molecules that bind to receptors on the cell surface.

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