Cell Membrane Structure and Transport Mechanisms
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Questions and Answers

What is a key characteristic of secondary active transport?

  • It only occurs in the presence of glucose.
  • It requires ATP directly.
  • It involves transporting molecules against their concentration gradient. (correct)
  • It transports molecules from high to low concentration.

    • Which transport mechanism is specifically used for glucose absorption in intestinal and kidney cells?

  • Primary active transport
  • Secondary active transport via symport (correct)
  • Osmosis
  • Facilitated diffusion

    • What does antiport refer to in the context of transport mechanisms?

  • Transport of two molecules in the same direction.
  • Transportation of a single type of ion.
  • Transport of two molecules in opposite directions. (correct)
  • Transport of one molecule without another.

    • Which of the following is true about vesicular transport?

    <p>It facilitates the transport of large molecules using vesicles.</p> Signup and view all the answers

    During secondary active transport, if a substance moves 'up' its gradient, it requires what kind of symport mechanism?

    <p>Cotransport mechanism</p> Signup and view all the answers

    Which of the following statements about glucose and sodium transport is accurate?

    <p>Sodium helps in the absorption of glucose in a symport mechanism.</p> Signup and view all the answers

    What role do vesicles play in exocytosis?

    <p>They transport large molecules outside the cell.</p> Signup and view all the answers

    The term 'gradient' in the context of molecular transport refers to what?

    <p>The difference in concentration between two areas.</p> Signup and view all the answers

    What structure is represented as the 'heads' of phospholipids in the cell membrane?

    <p>Hydrophilic regions</p> Signup and view all the answers

    Which component of the membrane is primarily involved in cellular recognition?

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

    What forms the bilayer structure of the cell membrane?

    <p>Phospholipid molecules</p> Signup and view all the answers

    Which of the following is NOT a component typically found in a cell membrane?

    <p>Nucleic acids</p> Signup and view all the answers

    How are the tails of phospholipids oriented in the bilayer?

    <p>They face inward toward the cytoplasmic environment.</p> Signup and view all the answers

    Which of the following statements about glycoproteins is true?

    <p>They facilitate cell communication and signaling.</p> Signup and view all the answers

    The fibrous proteins in the membrane primarily contribute to what property?

    <p>Stability and structure</p> Signup and view all the answers

    What type of lipid molecule is prominently featured in cell membranes for structural purposes?

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

    What is the molarity of the NaCl solution created by dissolving 9g of NaCl in 1L of water?

    <p>0.154 M</p> Signup and view all the answers

    What is the approximate osmolarity of the NaCl solution after doubling the molarity?

    <p>300 mOsM</p> Signup and view all the answers

    In the non-physiological illustration, what is the expected outcome after adding water to compartment A?

    <p>Compartment A swells</p> Signup and view all the answers

    What process will occur after adding penetrating particles to compartment A?

    <p>Particles will migrate until there is no concentration gradient</p> Signup and view all the answers

    What effect do non-penetrating particles have when distributed between compartments A and B without water movement?

    <p>They do not affect the osmotic balance</p> Signup and view all the answers

    What determines the distribution of penetrating particles at equilibrium across a semi-permeable membrane?

    <p>The concentration of non-penetrating solutes</p> Signup and view all the answers

    Which of the following types of solutes can cross the plasma membrane?

    <p>Freely penetrating solutes like urea</p> Signup and view all the answers

    Which statement describes the condition of compartment A if it is hypotonic relative to compartment B?

    <p>It will cause compartment B to swell</p> Signup and view all the answers

    What is the result if equilibrium is not reached after adding penetrating and non-penetrating particles?

    <p>The concentration gradient will continue to affect water movement</p> Signup and view all the answers

    What is a characteristic of non-penetrating solutes?

    <p>They cannot cross the plasma membrane.</p> Signup and view all the answers

    How does the addition of non-penetrating particles influence the distribution of water in the two compartments?

    <p>It encourages water to move into compartment B</p> Signup and view all the answers

    In what situation do penetrating particles move across a semi-permeable membrane?

    <p>When there is a difference in penetrating particle concentration</p> Signup and view all the answers

    What effect does the presence of non-penetrating solutes have on volume across a semi-permeable membrane?

    <p>It restricts movement of water, affecting overall volume.</p> Signup and view all the answers

    Which of the following is a common secondary messenger involved in signal transduction?

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

    What is the role of G-protein in signal transduction?

    <p>It transmits the signal from the receptor to the effector protein.</p> Signup and view all the answers

    What is the primary function of the effector proteins in signaling pathways?

    <p>To modulate enzyme activity and trigger secondary messengers.</p> Signup and view all the answers

    Which component of a homeostatic control mechanism is responsible for detecting changes in the environment?

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

    Which type of control system is responsible for systemic responses in homeostasis?

    <p>Endocrine systems</p> Signup and view all the answers

    What mechanism occurs when homeostatic mechanisms fail?

    <p>Physiological disturbances occur.</p> Signup and view all the answers

    In the context of homeostasis, what does 'set point' refer to?

    <p>The ideal operating condition for physiological variables.</p> Signup and view all the answers

    Which of the following describes the process of a simple neural reflex?

    <p>It involves mechanoreceptors that initiate a reflex action.</p> Signup and view all the answers

    Study Notes

    Cell Membrane Structure

    • Composed of a phospholipid bilayer with hydrophilic "heads" facing outward and hydrophobic "tails" inward.
    • Contains glycolipids and glycoproteins, providing structural integrity and facilitating cellular communication.
    • Fibrous proteins play a role in maintaining the membrane's shape and function.

    Transport Mechanisms

    • Cellular transport mechanisms include primary active transport and secondary active transport.
    • Primary active transport directly uses ATP to move molecules against their concentration gradient.
    • Secondary active transport utilizes the energy from the movement of one molecule to transport another against its gradient, categorized into symport (same direction) and antiport (opposite direction).

    Glucose Transport

    • Sodium-dependent glucose transporters (GLUTs) help absorb glucose across intestinal and kidney cells.
    • Glucose moves from low to high concentration (against its gradient) through symport mechanisms.

    Vesicular Transport

    • Involves movement of large molecules via vesicles, requiring energy (ATP).
    • Exocytosis releases substances outside the cell, while endocytosis brings substances into the cell.

    Osmolarity and Solution Examples

    • Normal saline solution: 0.154M sodium chloride, approximately 300 mOsM.
    • Understanding osmolarity principles is crucial for physiological assessments and treatments.

    Semi-permeable Membrane Dynamics

    • Water and penetrating particles (e.g., urea) can cross semi-permeable membranes, causing changes in volume.
    • Non-penetrating particles (e.g., proteins) cannot cross the membrane, influencing the overall solute balance and water distribution.

    Homeostasis and Regulation

    • Homeostasis is the body's ability to maintain stable internal conditions despite external changes.
    • Walter Cannon's postulates highlight the autonomic nervous system's role, tonic activity, antagonistic control, and the influence of chemical signals on receptor activity.

    Components of Homeostatic Control

    • Homeostatic control mechanisms involve a stimulus, sensor (receptor), control center (integration center), effectors, and compensatory responses.
    • Responses to stimuli can be localized (e.g., paracrine signaling) or systemic (involving the nervous and endocrine systems).

    Neural Reflex Mechanics

    • Simple neural reflexes involve a pathway: stimulus → receptor → sensory neuron → integrating center (spinal cord) → motor neuron → effector (muscle).
    • Example: Knee-jerk reflex demonstrates rapid response and integration at the spinal level.

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    Description

    This quiz explores the structure of the cell membrane, including the phospholipid bilayer and the roles of proteins. It covers various transport mechanisms such as active transport and the role of glucose transporters in cellular absorption. Test your understanding of these essential biological concepts.

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