Biological Membranes: Transport I Quiz

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Questions and Answers

What is the primary function of the sodium-dependent co-transport carrier system in intestinal epithelial cells?

  • To facilitate the hydrolysis of ATP for energy
  • To co-transport glucose and amino acids against their concentration gradients (correct)
  • To maintain a potassium gradient across the membrane
  • To transport sodium ions solely into the cell

Which of the following describes the action of the sodium/potassium pump (Na+/K+-ATPase)?

  • It uses glucose as the primary energy source
  • It transports 3 K+ ions from inside to outside of the cell
  • It operates independently of ATP hydrolysis
  • It maintains a Na+ gradient by moving 3 Na+ ions out of the cell and 2 K+ ions into the cell (correct)

What type of energy does secondary active transport primarily rely on?

  • Potential energy stored in cellular membranes
  • The concentration gradients created by ion pumps (correct)
  • Chemical energy from ATP
  • Thermal energy from surrounding environment

Which of the following is NOT a characteristic of microtransfer across cell membranes?

<p>It requires ATP for all transport processes (B)</p> Signup and view all the answers

In which mechanism does secondary active transport occur?

<p>Via either antiport or symport systems (C)</p> Signup and view all the answers

Which statement best describes the role of membrane transport in cell survival?

<p>Membrane transport is essential for both nutrient uptake and waste removal. (A)</p> Signup and view all the answers

What distinguishes macrotransfer from microtransfer?

<p>Macrotransfer requires energy, whereas microtransfer does not. (D)</p> Signup and view all the answers

Which of the following processes falls under the category of passive diffusion?

<p>Facilitated transport using protein channels. (D)</p> Signup and view all the answers

How do transporter proteins differ from channel proteins?

<p>Transporter proteins undergo conformational changes, while channel proteins do not. (A)</p> Signup and view all the answers

What is facilitated transport?

<p>Transport using proteins to assist the movement of molecules down their concentration gradient. (C)</p> Signup and view all the answers

Which mechanism is responsible for glucose entry into cells?

<p>Sodium-dependent co-transport carrier system. (D)</p> Signup and view all the answers

What aspect is not part of the intracellular environment?

<p>Communication between neighboring cells. (A)</p> Signup and view all the answers

Which process is involved in the exchange between neighboring and surrounding intercellular mediums?

<p>Diffusion and active transport. (B)</p> Signup and view all the answers

What size must particles be to exhibit Brownian movement?

<p>Less than 2µm (D)</p> Signup and view all the answers

What is the primary driving force for diffusion?

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

What type of transport requires energy to move substances across a cell membrane?

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

What type of transport allows water and small non-polar molecules to pass through a membrane freely?

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

Which molecules enter cells through facilitated diffusion?

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

Which type of transport solely involves bringing materials into endosomes or lysosomes?

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

What determines the rate of facilitated diffusion?

<p>Saturation of carrier binding sites (C)</p> Signup and view all the answers

What characterizes passive transport?

<p>Requires no energy (B)</p> Signup and view all the answers

Which of the following is NOT a method of microtransfer?

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

What happens to the rate of diffusion when all carrier proteins are saturated?

<p>It cannot increase regardless of the concentration gradient. (C)</p> Signup and view all the answers

What process is NOT required for facilitated transport?

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

What is the main difference between passive and active transport?

<p>Passive transport does not require energy (C)</p> Signup and view all the answers

Which of the following best describes facilitated diffusion?

<p>Passive transport using specific carrier proteins (B)</p> Signup and view all the answers

Which type of transport involves the engulfing of larger particles by the cell?

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

What is the function of exocytosis in a cell?

<p>Releasing substances outside the cell (C)</p> Signup and view all the answers

Macromolecules and charged ions require what type of transport mechanism?

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

What must occur for diffusion to cease?

<p>When equilibrium is reached (B)</p> Signup and view all the answers

Which mechanism does NOT involve the uniform distribution of molecules?

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

What process allows small molecules and ions to cross cell membranes without energy usage?

<p>Passive diffusion (A)</p> Signup and view all the answers

What is required for macrotransfer to occur?

<p>Endosomes or lysosomes (B)</p> Signup and view all the answers

What is the primary function of membrane transport proteins?

<p>To facilitate active transport of molecules (C)</p> Signup and view all the answers

Which statement accurately describes primary active transport?

<p>It requires ATP to move molecules against their electrochemical gradient. (B)</p> Signup and view all the answers

What is a characteristic feature of secondary active transport?

<p>It relies on the electrochemical gradient created by primary transport. (D)</p> Signup and view all the answers

How do temperature changes impact active transport systems?

<p>Low temperatures can inhibit active transport. (A)</p> Signup and view all the answers

In terms of proton pumps, what role does ATP play?

<p>ATP provides energy for the transport of protons across membranes. (A)</p> Signup and view all the answers

Which of the following best describes symport transport?

<p>Two molecules move in the same direction across the membrane. (D)</p> Signup and view all the answers

Which molecules are typically involved in active transport systems?

<p>Inorganic ions, amino acids, and monosaccharides (C)</p> Signup and view all the answers

What distinguishes antiport transport from symport transport?

<p>Antiport involves molecules moving in opposite directions, whereas symport involves the same direction. (B)</p> Signup and view all the answers

What happens to Na+, K+, and Cl- ions at the cellular membrane?

<p>They require selective pores or channels for transport. (C)</p> Signup and view all the answers

Why is ATP crucial for active transport processes?

<p>It serves as a primary energy source to drive the transport. (C)</p> Signup and view all the answers

Flashcards

Membrane Transport

The movement of substances across the plasma membrane, which is the outer layer of a cell.

Intracellular Environment

The conditions inside a cell.

Intercellular Environment

The conditions surrounding a cell, including fluid and other cells.

Exchange between Neighbouring Cells

The exchange of substances between neighbouring cells.

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Exchange within the cell

The exchange of substances within a cell.

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Exchange between the surrounding medium

The exchange of substances between a cell and its surroundings.

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Membrane Transport - Importance

The process that allows cells to take in nutrients and oxygen, and get rid of waste products.

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Microtransfer

The movement of substances across the plasma membrane through various transport mechanisms.

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Passive Transport

Movement of molecules from an area of high concentration to an area of low concentration, requiring no energy.

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Passive Diffusion

The movement of molecules across a membrane without the cell expending energy.

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Phagocytosis

The process by which cells engulf large particles, like bacteria or other cells, into a phagosome.

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Pinocytosis

The process by which cells take in small droplets of fluid and dissolved substances.

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Receptor-mediated endocytosis

The type of endocytosis where specific molecules bind to receptors on the cell surface and are then taken into the cell.

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Active Transport

The process by which the cell expends energy to move molecules across a membrane against their concentration gradient.

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Exocytosis

Release of substances from the cell, often packaged in vesicles.

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Fluid-phase endocytosis

A type of endocytosis where the cell takes in bulk amounts of fluid and dissolves substances.

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Diffusion

The movement of molecules from a high concentration region to a low concentration region due to their inherent kinetic energy.

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Equilibrium

The point where diffusion stops because the concentration of the molecules is equal on both sides of the membrane.

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Saturation

The rate at which facilitated diffusion occurs is limited by the number of carrier proteins available in the membrane. If all carrier proteins are occupied, the diffusion rate plateaus even if the concentration gradient increases.

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Concentration Gradient

The difference in the concentration of a molecule across a membrane. This drives diffusion from high concentration to low concentration.

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Facilitated Diffusion

A type of membrane transport that requires carrier proteins to facilitate the movement of molecules across the membrane.

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Carrier Proteins

Proteins embedded in the membrane that bind to specific molecules and facilitate their transport across the membrane.

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Freely Permeable Molecules

Molecules that can freely pass through the cell membrane without the need for carrier proteins.

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Osmosis

The movement of water molecules across a semi-permeable membrane from a region of high water concentration to a region of low water concentration.

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Membrane Transport Proteins

Transmembrane proteins that facilitate the movement of specific molecules across cell membranes.

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Active Transport: Moving Against the Gradient

The movement of substances across a cell membrane from an area of high concentration to an area of low concentration, requiring the use of energy.

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Primary Active Transport

Active transport systems that use the energy directly from ATP.

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Secondary Active Transport

The movement of one substance across a cell membrane, driven by the movement of another substance along its concentration gradient.

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Symport

Secondary active transport where both molecules move in the same direction across the membrane.

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Antiport

Secondary active transport where molecules move in opposite directions across the membrane.

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Proton Pump

A type of primary active transport that uses the energy of ATP to pump protons (hydrogen ions) across membranes.

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Electrochemical Gradient

The difference in charge and concentration of ions across a membrane.

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Homeostasis

The ability of a cell to maintain a stable internal environment despite changes in the external environment.

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Study Notes

Biological Membranes: Transport I (Microtransfer)

  • Course: Fundamentals of Human Biology
  • Code: FUNBIO.8
  • Lecturer: Dr. Irene Oglesby
  • Date: 14th October 2024
  • Year: Foundation Year

Learning Outcomes

  • ALO1: Contrast and compare intracellular and intercellular environments
  • ALO2: Differentiate between macrotransfer and microtransfer processes
  • ALO3: Describe passive diffusion processes and membrane transport proteins' role
  • ALO4: Differentiate between transporter and channel proteins
  • ALO5: Explain facilitated transport
  • ALO6: Describe mechanisms of active transport in cell membranes
  • ALO7: Explain how glucose enters cells via sodium-dependent co-transport

Membrane Transport

  • Involves substance movement across plasma membranes
  • Nutrients and oxygen must enter; waste products must exit for metabolism

Membrane Transport - Intracellular vs. Intercellular

  • Cell survival depends on exchange
    • Between neighboring cells
    • Within the cell (intracellular environment)
    • With the surrounding intercellular medium (extracellular matrix)

Membrane Transport Mechanisms

  • Macrotransfer: Transport of macromolecules
    • Materials are brought into endosomes or lysosomes within the cytoplasm
    • Molecules must cross the surrounding membrane to enter the cytoplasm
  • Microtransfer: Transport of small molecules and ions across cell membranes (internal and external)

Microtransfer Mechanisms

  • Passive Transport: No energy required
    • Simple diffusion: Movement along concentration gradient
    • Brownian movement: Random movement of particles less than 2µm
    • Molecules move from high to low concentrations till evenly distributed
  • Active Transport: Requires energy
    • Moves molecules against concentration gradient

Passive Transport

  • No energy required

Facilitated Transport

  • Uses carrier proteins (permeases)
  • Highly selective, often transporting one type of molecule
  • Facilitates the transport of sugars, amino acids, and nucleotides
  • Essentially a passive transport system (no direct energy required)
  • Affected by carrier binding site saturation and concentration gradient

Active Transport

  • Requires energy (ATP)
  • Transports macromolecules and charged ions (H+, Na+, K+, Cl−) across membranes against concentrations gradients
  • Involves selective pores and channels (membrane transport proteins)
  • Types:
    • Primary Active Transport: Moves molecules against electrochemical gradient directly using ATP energy.
    • Secondary Active Transport: Uses electrochemical gradient of one molecule to transport a second molecule against its gradient.
      • Can be symport (molecules move in the same direction) or antiport (molecules move in opposite directions).

Sodium-Dependent Co-Transport (Symport)

  • Important in intestinal epithelial cells
  • Drives glucose, other monosaccharides, amino acids, and pyrimidines into cells
  • Glucose and sodium ions move together in the same direction (symport)

Active Transport - Antiport System

  • Most membranes have ATP-driven sodium/potassium pumps (Na+/K+-ATPase)
    • Maintains a sodium gradient
  • Transports 3 Na+ ions outward, 2 K+ ions inward using one ATP
  • Antiport transports molecules in opposite directions

Models of Active Transport

  • Integral transmembrane proteins act as carriers, moving substances between cell surfaces.
  • Proton pumps use ATP energy to move protons (H+) across membranes. The resulting electrochemical gradient can be used for other processes.

Summary - Membrane Transport (Microtransfer)

  • Microtransfer is the transport of small molecules and ions across cell membranes (internal or external)
  • Includes diffusion, facilitated diffusion, passive transport, and active transport
  • Active transport requires ATP; passive transport, facilitated, and diffusion do not.

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