22 cards generated

Save your deck before it's gone

These flashcards aren't stored yet — they'll disappear when you leave. Create a free account to keep them, and unlock everything below.

Keep & study
  • Save this deck to your account
  • Study with spaced repetition
  • Export to Anki (.apkg) or PDF
Bigger & better generations
  • Process documents up to 100 pages
  • Images extracted from your PDFs
  • Sharper text extraction & a more advanced AI model
Sign up free → Free forever · No credit card
Membrane Transport video transcript W2
  • Info
    Click 'Save & Edit' to enable all features
    Study
    Export
    Edit
    Manage
Public

Flashcards in this deck (22)

Searching...

  • What is the primary property of the plasma membrane that controls substance movement?

    Selective permeability: it allows passage of some substances and prevents passage of others.

    membrane permeability

  • What distinguishes passive transport from active transport across the plasma membrane?

    Passive transport does not require cellular energy; active transport requires ATP.

    transport energy

  • Define diffusion in the context of membrane transport.

    Diffusion is passive net movement of a substance down its concentration gradient from high to low concentration.

    diffusion passive

  • Which substances move across the membrane by simple diffusion?

    Nonpolar, lipid-soluble plasma membrane compatible substances such as oxygen, carbon dioxide, and soluble vitamins.

    simple_diffusion examples

  • What is carrier-mediated facilitated diffusion?

    Specific water-soluble molecules bind integral carrier proteins that change shape and transport them across the membrane down their concentration gradient.

    carrier facilitated_diffusion

  • Give an example of carrier-mediated facilitated diffusion.

    Glucose transporters moving glucose down its concentration gradient without using energy.

    glucose carrier

  • How do channel proteins transport substances across membranes?

    Channels form aqueous pathways selective for size and charge, allowing water-soluble substances to pass through.

    channels selectivity

  • What is the difference between leakage channels and gated channels?

    Leakage channels are always open; gated channels open in response to chemical, mechanical, or electrical signals.

    channels gating

  • Define osmosis and its direction relative to solute concentration.

    Osmosis is diffusion of a solvent (e.g., water) across a selectively permeable membrane from low solute concentration (high solvent) to high solute concentration (low solvent).

    osmosis water

  • What types of signals open gated channels and give one example for each?

    • Chemical: ligand-gated channels
    • Mechanical: mechanically gated channels
    • Electrical: voltage-gated channels
    gated signals

  • Why do some substances require carriers or channels to cross the plasma membrane?

    Because they are water-soluble and incompatible with the lipid bilayer, so they need an aqueous path or specific carriers.

    transport compatibility

  • What basic role does the plasma membrane play between the cytoplasm and extracellular fluid?

    It acts as a barrier separating the cytoplasm from the extracellular fluid.

    membrane barrier

  • What energy molecule is explicitly mentioned as required for active transport?

    ATP (cellular energy).

    atp active_transport

  • What is primary active transport and give an example?

    Primary active transport uses ATP to move substances against their concentration gradient; example: the sodium-potassium pump exchanges intracellular Na+ for extracellular K+.

    active primary

  • What energy source is required for the sodium-potassium pump?

    ATP is required for the sodium-potassium pump.

    atp pump

  • What is secondary active transport?

    Secondary active transport uses an ion gradient established by primary active transport to drive movement of other charged molecules down that gradient.

    secondary transport

  • How do 'symport' and 'antiport' differ in secondary active transport?

    Symport cotransports molecules in the same direction; antiport cotransports molecules in the opposite direction.

    symport antiport

  • What is vesicular transport?

    Vesicular transport moves substances into or out of the cell inside vesicles, which are small sacs formed at or with the plasma membrane.

    vesicular transport

  • Which cellular organelle packages many proteins that are then transported by vesicles?

    Many proteins produced and packaged by the Golgi apparatus are transported by vesicles.

    golgi proteins

  • Define endocytosis.

    Endocytosis transports substances from the extracellular fluid into the cell by forming vesicles at the plasma membrane.

    endocytosis vesicles

  • Define exocytosis.

    Exocytosis is the process where intracellular vesicles fuse with the plasma membrane to release their contents into the extracellular fluid.

    exocytosis vesicles

  • What are the main categories of transport across the plasma membrane?

    Transport across the plasma membrane can be either passive (simple diffusion, osmosis, facilitated diffusion) or active (requires ATP and can move substances against gradients).

    membrane transport
Study Notes

Membrane transport — quick study notes

Overview

  • The plasma membrane is a lipid bilayer that separates cytoplasm and extracellular fluid and is selectively permeable.
  • Transport across the membrane is either passive (no ATP) or active (requires ATP).
  • Cells exchange nutrients and wastes by different mechanisms depending on molecule size, polarity and charge.

Passive transport (no cellular energy)

  • Definition: net movement down a concentration gradient: \([X]_{high}\rightarrow[X]_{low}\).

Simple diffusion

  • Small, nonpolar and lipid‑soluble molecules cross the bilayer directly (e.g., O₂, CO₂, fat‑soluble vitamins).
  • Rate depends on concentration difference and membrane permeability.

Facilitated diffusion (still passive)

  • Used for water‑soluble or charged molecules that cannot cross the lipid core.

Carrier‑mediated facilitated diffusion - Carriers (integral proteins) bind a specific molecule, change shape, and release it on the other side. - Shows specificity and can saturate when carriers are fully occupied (transport maximum). - Example: glucose transporters move glucose down its concentration gradient.

Channel‑mediated facilitated diffusion - Channels are transmembrane pores that allow passage of ions or small polar molecules via an aqueous path. - Channels are selective for size and charge. - Types: - Leak channels: always open, permit passive flow. - Gated channels: open only with a specific signal: - Ligand‑gated: chemical binds to open. - Mechanically gated: opened by physical force or pressure. - Voltage‑gated: opened by changes in membrane potential.

Osmosis

  • Osmosis = diffusion of a solvent (usually water) across a selectively permeable membrane.
  • Water moves from low solute (high water) to high solute (low water) concentration.
  • Can cause cell swelling or shrinking depending on extracellular tonicity.

Active transport (requires energy)

  • Moves substances against concentration gradients or maintains ion gradients; needs ATP or an energy source.

Primary active transport

  • Direct use of ATP to move ions/molecules.
  • Key example: Na⁺/K⁺ ATPase (sodium–potassium pump) — maintains intracellular low Na⁺ and high K⁺.
  • Stoichiometry commonly taught: \(\(3\ \mathrm{Na}^+\ \text{out},\ 2\ \mathrm{K}^+\ \text{in (per ATP)}\)\)

Secondary active transport (cotransport)

  • Uses the electrochemical gradient set up by primary active transport as an indirect energy source.
  • Movement of one ion down its gradient drives transport of another solute.
  • Two modes:
  • Symport (cotransport): both move in the same direction (e.g., Na⁺/glucose symporter).
  • Antiport (exchanger): move in opposite directions.

Vesicular transport (bulk transport)

  • Moves large particles, droplets, or many molecules in membrane‑bound vesicles.

Endocytosis (into cell) - Vesicles form at the plasma membrane to bring substances inside. - Common forms (high‑level): phagocytosis (large particles), pinocytosis (fluid), receptor‑mediated endocytosis (specific uptake).

Exocytosis (out of cell) - Intracellular vesicles fuse with the plasma membrane and release contents to the extracellular space. - Used to secrete proteins, neurotransmitters, and membrane renewal.

Key relationships & points to remember

  • Passive vs active: passive follows gradients; active can go against gradients using ATP.
  • Solubility matters: nonpolar → simple diffusion; polar/charged → channels or carriers.
  • Channels vs carriers: channels provide open pores (fast), carriers undergo conformational changes (slower, saturable).
  • Primary vs secondary active transport: primary uses ATP directly; secondary uses the gradient established by primary transport.
  • Osmosis is driven by solute concentration differences but is movement of the solvent.

Common examples (quick)

  • Gas exchange: O₂ and CO₂ by simple diffusion.
  • Glucose uptake into many cells: carrier‑mediated facilitated diffusion or Na⁺‑driven symport in intestines.
  • Neuron signalling: voltage‑gated ion channels and Na⁺/K⁺ pump maintain resting potential.

Study tips

  • Draw diagrams showing gradients and transport direction.
  • Memorize which molecules use which pathway by polarity/size.
  • Practice explaining Na⁺/K⁺ pump and secondary transport in one sentence each.

Short summary

  • Membrane transport mechanisms let cells control internal composition by combining passive flows, ATP‑driven pumps, and vesicular traffic.