Transport Across Cell Membrane Flashcards
is a phospholipid bilayer that regulates the entry and exit of molecules.
Cell Membrane
The different types of transport mechanisms across cell membranes are as follows:
Simple Diffusion
Facilited Diffusion
Osmosis
Transport across the plasma membrane occurs unaided in
Simple Diffusion
This is a type of passive transport in which molecules that cross the cell membrane move quickly due to the presence of specific permeases in the membrane.
Facilitated Diffusion
occurs only in the direction of a concentration gradient and does not require metabolic energy. It is distinguished by the following characteristics:
Facilitated diffusionq
is the process by which water molecules pass through a membrane from a region of higher water concentration to a region of lower water concentration
OSMOSIS
The process by which water molecules enter the cell is known as
Endosmosis
the process by which water molecules exit the cell is known as
Exosmosis
Excessive exosmosis causes the cytoplasm and cell membrane in plant cells to shrink away from the cell wall.
Plasmolysis
When two compartments of different solute concentrations are separated by a semipermeable membrane, the compartment with higher solute concentration is called
Hypertonic
When the internal solute concentration equals the external solute concentration, it is said to be
Isotonic
is the process of moving solvent particles across a semipermeable membrane from the solvent’s higher concentration to the solvent’s lower concentration. The complete process does not require energy to take place.
*For example, the absorption of water molecules from the soil through the roots of the plant.
Osmosis
is the process of moving particles from a region of higher concentration to a region of lower concentration until equilibrium is reached. Simple diffusion does not require energy; however, facilitated diffusion requires ATP.
•For example, the aroma is diffused into the air by perfume sprays.
Diffusion
is a kind of cellular transport in which substances like amino acids, glucose and ions are transported across cell membranes to a region that already has a high concentration of such substances.
Active Transport
allows one solute to move downward (along its electrochemical potential gradient) in order to generate enough entropic energy to drive the transport of the other solute upward (from a low concentration region to a high concentration region).
Secondary Active Transport
There are two types of coupled transport
Anitiport
Symport
is the energy-requiring process of pumping molecules and ions across membranes “uphill” - against a concentration gradient. To move these molecules against their concentration gradient, a carrier protein is needed.
Active Transport
can work with a concentration gradient (during passive transport), but some carrier proteins can move solutes against the concentration gradient (from low concentration to high concentration), with an input of energy.
Carrier proteins
moves sodium and potassium ions against large concentration gradients. It moves two potassium ions into the cell where potassium levels are high, and pumps three sodium ions out of the cell and into the extracellular fluid.
The sodium-potassium pump system
Where is sodium-potassium pump found
Plasma Membrane
It helps maintain cell potential and regulates cellular volume.
Sodium-potassium pump
The voltage across a membrane
Membrane potential
It is very important for the conduction of electrical impulses along nerve cells.
membrane potential
2 forces that drive the diffusion of ions across the plasma membrane
Chemical force (ion concentration gradient) and Electrical force
