Understanding Uniport, Cotransport, Symport, and Antiport
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Questions and Answers

What is the function of the lipid layer in the tear film?

  • Enhancing tear production
  • Stimulating blinking reflex
  • Preventing tear evaporation (correct)
  • Providing nutrients to the cornea

    • Which of the following is NOT a component of the lipid layer in tear film?

  • Cholesterol
  • Wax esters
  • Triacylglycerols
  • Proteins (correct)

    • During tear-film breakup time, the subsequent blink is stimulated by:

  • Pain sensation
  • Muscle contraction
  • Corneal dryness
  • Film stabilization (correct)

    • Which gland secretes Meibum, a crucial component of the tear film lipid layer?

    <p>Meibomian gland</p> Signup and view all the answers

    The aqueous layer of tear film contains which of the following components?

    <p>Dissolved salts</p> Signup and view all the answers

    In tear film formation, when substances are transported in opposite directions, it is an example of:

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

    What is the major component of the lipid layer of the precorneal tear film?

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

    Which of the following is derived from eicosanoic acids and includes examples like prostaglandins and leukotrienes?

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

    What is the main characteristic of glycolipids?

    <p>Found in nervous, ocular, and other tissues</p> Signup and view all the answers

    What is the basic structure that binds glycolipids?

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

    In which glycolipid is phosphocholine esterified to a ceramide?

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

    What is the function of lipid esters found in tear film?

    <p>Help the lipids adhere to the eyelid skin and act as a barrier to the aqueous layer</p> Signup and view all the answers

    What is a possible cause contributing to meibomian gland dysfunction?

    <p>Increased cholesterol and appearance of ceramides</p> Signup and view all the answers

    What is the advantage of high fluidity of the photoreceptor disc membrane?

    <p>Allows for rotational and lateral movements of rhodopsin needed for phototransduction</p> Signup and view all the answers

    To what class of lipids does Vitamin A belong?

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

    What is the role of Vitamin E in the retina?

    <p>Absorbs free radicals</p> Signup and view all the answers

    What are the chemical forms of Vitamin A and their roles?

    <p>Retinyl ester: storage; Retinol: transport; Retinal: visual transduction; Retinoic acid: synthesis</p> Signup and view all the answers

    What process involves the transport of 3 sodium ions out of the cell and 2 potassium ions into the cell by hydrolyzing 1 molecule of ATP?

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

    Which type of transport involves substances being transported in the same direction, such as glucose transport in kidney tubules?

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

    What is the primary function of the lipid layer in tear film?

    <p>To stabilize the tear film</p> Signup and view all the answers

    Which components are present in the anterior/superficial lipid layer of tear film?

    <p>Cholesteryl esters and waxes</p> Signup and view all the answers

    In tear-film formation, when substances are transported simultaneously, it is an example of:

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

    Which gland secretes Meibum, a crucial component of the tear film lipid layer?

    <p>Meibomian gland</p> Signup and view all the answers

    What is the result of tear-film breakup time?

    <p><strong>Stimulation</strong> of the next blink</p> Signup and view all the answers

    What is the composition of the aqueous layer in tear film?

    <p><strong>Dissolved salts and proteins</strong></p> Signup and view all the answers

    What is the significance of the protein to lipid ratio in a membrane?

    <p>Helps gauge the role of membrane – transport, metabolism, and signal transduction</p> Signup and view all the answers

    What is simple diffusion and provide an example?

    <p>Movement from lower to higher concentration without energy, example: movement of glucose using GLUT-1</p> Signup and view all the answers

    How does facilitated transport differ from active transport?

    <p>Facilitated transport occurs against the concentration gradient, while active transport occurs down the gradient</p> Signup and view all the answers

    What is the role of glycolipids in cell membranes?

    <p>Serve as biological bridges and bonding agents in membranes</p> Signup and view all the answers

    Which membrane has a protein to lipid ratio of 3:1?

    <p>Mitochondrial inner membrane</p> Signup and view all the answers

    What is the primary function of glycoproteins in cell membranes?

    <p>Function as molecular bridges between cells</p> Signup and view all the answers

    Which type of transport is limited by the ability of proteins or enzymes to perform the task?

    <p><em>Facilitated transport</em></p> Signup and view all the answers

    Give an example of a process that requires enzyme catalysis for energy to operate a pump moving molecules against their concentration gradient.

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

    What is one of the functions of lipid esters found in the tear film?

    <p>Help the lipids form a film over the aqueous layer and maintain contact with it</p> Signup and view all the answers

    Which is a possible cause contributing to meibomian gland dysfunction?

    <p>Detachment of epithelial cells from the gland blocking lipid flow to the tear film</p> Signup and view all the answers

    Why is high fluidity crucial for the photoreceptor disc membrane?

    <p>Enables rotational and lateral movements required for phototransduction</p> Signup and view all the answers

    To which class of lipids does Vitamin A belong?

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

    What happens in the retina in the absence of Vitamin E?

    <p>Free radicals attack membrane fatty acids, breaking them into fragmentary aldehydes</p> Signup and view all the answers

    What is a role of retinol among the chemical forms of Vitamin A?

    <p>Transport and hormonal function</p> Signup and view all the answers

    Which statement describes a function of Vitamin E in the retina?

    <p>Absorption of free radicals</p> Signup and view all the answers

    What are common dietary sources of Vitamin A apart from animal sources?

    <p>Carrots, sweet potatoes</p> Signup and view all the answers

    What is a common adverse effect of high daily intake of Vitamin A?

    <p>Blurred vision</p> Signup and view all the answers

    Where do gangliosides mainly reside in the body?

    <p>Nervous tissue</p> Signup and view all the answers

    What is the characteristic physical feature of Tay-Sachs disease?

    <p>Accumulation of gangliosides in nerve tissues</p> Signup and view all the answers

    What enzyme deficiency leads to Tay-Sachs disease?

    <p>Hexosaminidase A</p> Signup and view all the answers

    In which region of the eye is the characteristic cherry-red spot observed due to Tay-Sachs disease?

    <p>Macular region</p> Signup and view all the answers

    What is the primary impact of ganglioside accumulation in the retina?

    <p>Degeneration of ganglion cells</p> Signup and view all the answers

    How does Tay-Sachs disease affect the lifespan of affected individuals?

    <p>Causes early childhood death</p> Signup and view all the answers

    What are some common symptoms experienced with high Vitamin A intake?

    <p>Irritability and abdominal pain</p> Signup and view all the answers

    What is the main role of Chylomicra in the body?

    <p>Incorporate hydrophobic lipids</p> Signup and view all the answers

    How is retinol conveyed from the liver to target cells?

    <p>Mobilization after binding to prealbumin</p> Signup and view all the answers

    What happens to retinol after it enters target cells?

    <p>Released and transported via a receptor protein</p> Signup and view all the answers

    Which proteins are involved in mobilizing retinal for transport to target cells?

    <p>Prealbumin and retinol binding protein</p> Signup and view all the answers

    What are the three disorders of the eye caused by Vitamin A deficiency?

    <p>Nyctalopia, xerophthalmia, keratomalacia</p> Signup and view all the answers

    What does Keratomalacia involve?

    <p>Degeneration of corneal epithelium and corneal perforation</p> Signup and view all the answers

    Which process occurs after all-trans retinal is converted to 11-cis-retinal in the retina?

    <p>Esterification and isomerization</p> Signup and view all the answers

    What is Xerophthalmia primarily characterized by?

    <p>Dry eyes due to hardening of corneal conjunctiva</p> Signup and view all the answers

    Which type of lipids are found on the surface of chylomicra transport complexes?

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

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