Medical Biochemistry Lecture 5: Transport Mechanisms
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Questions and Answers

Which of the following transport mechanisms does not require energy but has a more rapid rate than simple diffusion?

  • Aquaporins
  • Facilitated diffusion (correct)
  • Ion channels
  • Active transport

What is the main function of aquaporins?

  • Regulation of nerve impulses
  • Facilitated diffusion
  • Transport of water (correct)
  • Transport of ions

Which of the following is a salient feature of ion channels?

  • They allow the selective entry of various ions (correct)
  • They require energy for transport
  • They are regulated by hormones
  • They are unidirectional

What is the best example of active transport mentioned in the text?

<p>Sodium pump (C)</p> Signup and view all the answers

What is the main function of the calcium pump?

<p>Maintain low cytosolic calcium concentration (C)</p> Signup and view all the answers

Which transport system carries single solute across the membrane?

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

Which type of substances is the permeability of cell membrane dependent on?

<p>Solubility in lipids (D)</p> Signup and view all the answers

What drives the entry of solutes and gases into the cells in simple diffusion?

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

In which direction does simple diffusion occur?

<p>From higher to lower concentration (A)</p> Signup and view all the answers

What type of process is simple diffusion?

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

What drives the entry of solutes and gases into the cells in facilitated diffusion?

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

What property influences the rate of entry of solutes and gases in simple diffusion?

<p>Solubility in the hydrophobic core of the membrane (B)</p> Signup and view all the answers

What kind of process is facilitated diffusion?

<p>Passive transport (C)</p> Signup and view all the answers

What allows facilitated diffusion to operate bidirectionally?

<p>Specific carrier proteins (B)</p> Signup and view all the answers

What is an important function of the cell membrane related to transport mechanisms?

<p>Withhold unwanted molecules (B)</p> Signup and view all the answers

What does passive transport not require?

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

What determines the rate of entry in simple diffusion?

<p>Solubility in the hydrophobic core of the membrane (B)</p> Signup and view all the answers

What is an example of passive transport mechanism?

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

Flashcards

Cell membrane permeability

The ability of substances to pass through the cell membrane. Lipid solubility is key, not necessarily size.

Passive transport

Movement of substances across the membrane without energy input.

Simple diffusion

Substances move from high to low concentration.

Facilitated diffusion

Substances move from high to low concentration with the help of a protein.

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Aquaporins

Channel proteins that specifically transport water.

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Ion channels

Channel proteins that allow specific ions to pass.

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Active transport

Movement of substances across the membrane requiring energy.

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Sodium-potassium pump

An active transport mechanism that maintains sodium and potassium balance.

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Uniport

A transport system that moves one substance at a time.

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Symport

A transport system that moves two substances in the same direction.

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Antiport

A transport system that moves two substances in opposite directions.

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Sodium-dependent glucose transport

Glucose moves into the cell with sodium.

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Sodium-chloride exchange

Sodium moves in, chloride moves out.

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Sarcoplasmic reticulum

Specialized membrane system in muscles that stores calcium.

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ATP

Energy currency for active transport.

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Transport systems and homeostasis

Transport systems help maintain a stable internal environment in the cell.

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Calcium pump

Maintains low cytosolic calcium levels.

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Integral membrane protein

A protein that spans the cell membrane.

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Study Notes

  • Lecture 7 in the Department of Biochemistry and Pharmacy at Al-Imam Muhammad Ibn Saud University, by Dr. Rayyad Hanifah, discusses transport mechanisms in cell membranes.
  • Substances' permeability across cell membranes depends on their solubility in lipids rather than molecular size.
  • Water-soluble compounds, unlike lipid-soluble ones, are generally impermeable and require specialized carrier-mediated transport.
  • Cell membranes serve to keep out unwanted molecules and allow entry of necessary ones.
  • Transport mechanisms are classified into two major categories: passive and active transport.
  • Passive transport involves simple diffusion and facilitated diffusion:
    • Simple diffusion: solutes and gases enter passively, driven by the concentration gradient.
    • Facilitated diffusion: carrier molecules facilitate entry of specific solutes into the cell without requiring energy.
  • Aquaporins are membrane channel proteins that serve as selective water pores.
  • Ion channels are specialized carrier systems for ion transport:
    • Quick entry of various ions (e.g., Ca++, K+, Na+, and Cl--).
    • They are selective ion conductive pores.
    • They are transmembrane proteins that regulate their activity through voltage-gated, ligand-gated, or mechanically gated mechanisms.
  • Active transport is a unidirectional process requiring energy:
    • The sodium pump is an example of active transport, maintaining low intracellular sodium and high potassium levels.
    • The calcium pump maintains low cytosolic calcium levels to facilitate muscle contraction.
  • Transport mechanisms can be classified as uniport, symport, and antiport systems.
  • The sodium-potassium ATPase is an integral membrane protein responsible for maintaining the intracellular concentration of sodium and potassium.
  • Sarcoplasmic reticulum is a specialized membrane system in skeletal muscles responsible for regulating calcium concentrations and thus muscle contraction.
  • ATP plays a critical role in active transport systems.
  • Transport systems are important for various cellular processes and maintaining homeostasis.
  • Sodium and calcium pumps are two major examples of active transport systems.
  • Transport systems can be classified based on the number of solutes they transport.
  • Sodium-dependent glucose transport is an example of symport.
  • Sodium-chloride exchange is an example of antiport.

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