Cell Membrane Transport Flashcards
(26 cards)
Define passive transport
When no energy is required from the cell to pass through the cell membrane. Substances are moving from an area of higher concentration to an area of lower concentration.
Define active transport
When substances require energy to pass through the cell membrane, often because they’re moving from an area of low concentration to an area of high concentration (up the gradient)
Define concentration
The number of particles of a substance per unit of volume. More particles means a higher concentration.
Describe diffusion
The movement of a substance due to a difference in concentration. Happens w/out help from other molecules.
What are the three types of passive transport?
diffusion, osmosis, and facilitated diffusion
What kind of substances pass through using diffusion? Why?
Small, hydrophobic molecules (like oxygen and CO2) can squeeze between lipid molecules by simple diffusion.
Describe osmosis
The diffusion of water molecules. Moves from area of high concentration to low concentration. Water moves in or out of the cell until its concentration is the same on both sides of the membrane. Has to occur across a semipermeable membrane (like the plasma membrane).
Describe facilitated diffusion
Transport proteins help diffusion.
What kind of substances use facilitated diffusion?
hydrophilic molecules, charged ions, relatively large molecules
What are the different types of transport proteins?
Channel proteins and carrier proteins
What do channel proteins do?
Form tiny holes/pores in the membrane which allows water molecules and small ions to pass through the membrane without touching the hydrophobic tails of the lipid molecules.
What do carrier proteins do?
Bind with specific ions or molecules. Binding makes protein change shape as it carries ions/molecules across the membrane.
Define solution
A mixture of a solvent (usually H2O) and a solute (the thing that is dissolved, like sugar or salt)
Define isotonic
solutions of equal concentrations of solutes.
Which of the following can pass through the cell membrane: Na+, Cl-, O2, a protein, H2O, glucose.
O2 and H2O
Hypertonic v. Hypotonic
A hypertonic solution has a higher concentration of solute than another solution, meaning water will flow into it. A hypotonic solution has a lower concentration of solute than another solution, meaning water will flow out of it.
What are pumps?
proteins embedded in the cell membrane that help with active transport
What are the two types of active transport?
Membrane pumps (like sodium-potassium pump) and vesicle transport
Describe sodium-potassium pump
it moves sodium ions out of the cell and potassium ions into the cells. Both ions move from low concentration to high concentration, so energy is needed from ATPs. The pump is a carrier protein.
What is the membrane potential?
An electrical and chemical gradient across the cell membrane. Membrane potential is the difference in electric potential between the interior and the exterior of a biological cell.
Define vesicle transport and name the types
Active transport, helps very large molecules across the cell membrane. Two types: endocytosis and exocytosis
Describe the process of endocytosis
Endocytosis moves a substance into the cell. the plasma membrane engulfs the substance, a vesicle pinches of from the membrane and carries the substance into the cell.
Describe the process of exocytosis
Exocytosis moves a substance out of the cell. A vesicle containing the substance moves through the cytoplasm to the cell membrane.
What is phagocytosis?
When an entire cell or other solid particle is engulfed through endocytosis.
