Lecture 2 Membrane Transport Mechanisms Flashcards
What transport mechanism requires energy other than kinetic energy?
Active transport
What ion is most concentrated in the extracellular environmet?
Na+
The sodium - potassium pump is what type of transport
Primary active transport
The Sodium - Calcium pump is what type of transport?
Secondary Active transport
Glucose transporters (GLUT) are what type of transporters?
Facilitated diffusion
Define diffusion
Movement of particles from a region of high concentration to an area of low concentration
What type of membrane is used for diffusion?
A membrane is not necessary for diffusion to occur but a permeable barrier can be present
Define Osmosis
Movement of a solvent from a region of high concentration to an area of low concentration across a semipermeable membrane
What is the universal solvent?
H2O
Define Kinetic energy
energy of motion
What creates Osmotic pressure
Water moves across a cell membrane because of concentration differences, water will accumulate on one side. This usually creates higher pressure one one side
Describe the methods of molecular movement
It is random and has kinetic energy
What are mechanisms for crossing cell membranes using only kinetic energy (energy independent)
Diffusion
Osmosis
Facilitated diffusion
Give examples of molecules that can diffused across a cell membrane
Oxygen, CO2, N, alcohols
What determines the rate of diffusion
Concentration differences, membrane electric potential and pressure difference
What are the types of energy independent channels
Non-gated (aquaporins, ion channels)
Gated (ligand, voltage gated)
What are aquaporins
Channels that are permeable to water
What is the difference between simple diffusion and facilitated diffusion?
As concentration of a substance increases, in FD the rate of diffusion approaches a maximum called Vmax. as the concentration of the diffusing substance increases.
What uses Facilitated diffusion?
Amino acids and glucose
Facilitated diffusion requires what?
Uniporter carrier protein
Describe uniporter
Has binding sites that are alternately available on either side of the membrane
What is a major example of a uniporter
GLUT (glucose transporter) Allow the intake of glucose
What is active transport?
Movement of particles against concentration gradient and requires energy other than kinetic (ATP)
Define Primary Active Transport
Movement of particles against concentration gradient with energy derived directly from breakdown of ATP. Utilizes ATPase transporters
Define secondary active transport
Energy is derived secondarily from concentration differences of molecular or ionic substances created originally by primary active transport.
What are multiporters?
They are secondary active transporters that have at least one of the solutes move down its electrochemical gradient while one or more of the other solutes moves up (against) its elctrochemical gradient
What ion is oftern involved in secondary active transport?
Sodium
What are the two types of multiporters?
Symporters and antiporters
Active transport always occurs when what happens?
When a substance moves up (against) its electrochemical gradient
If sodium moves down its electrochemical gradient in a multiporter, why it this referred as to as secondary active transport.
Because we had to move the sodium out to begin with against its concentration gradient using active transport
Sodium/ calcium antiporters move three sodium ions per calcium ion. Why does it take three sodium ions to move one calcium ion?
Because Calcium is much larger than sodium
K+ channels are always open and non gated. So if a large K+ can pass through this channel then why cant a small Sodium ion pass through the channel?
Ions in solutions are surrounded by water molecules. A hydrated K+ ion has a larger diameter than a hydrated sodium ion. Carbonyl oxygens on the channel will pull off the water molecules. K+ is dehydrated and small enough to pass through the pore. Hydrated sodium is too small to be effected by the carbonyl oxygens
