Transport of substances Through the cell membrane
3NA in ____________out
2K
Two types of active transport (give examples)
Active Transport is the term used to describe the processes of moving materials through the cell membrane that requires the use of energy. There are three main types of Active Transport: The Sodium-Potassium pump, Exocytosis, and Endocytosis.
What activates the Na/K ATPase
Insulin Beta-2 adrenergic agonist
Cytoplasm with high concentration of
K
sodium calcium exchanger
Removes Ca2+ from cardiac muscle in exchange for Na+ Important for heart
Difference between simple diffusion vs facilitated diffusion
Simple diffusion is passive but facilitated diffusion is an active process that uses energy. Simple diffusion requires molecules to move through special doorways in the cell membrane.
Facilitated diffusion
Specific carrier proteins help transport the substances across the membrane
Osmosis
flow of water across the semipermeable membrane from a solution with low solute concentration to a solution with the high solute concentration
Diffusion of water across the selectively permeable membranes depend on
osmotic pressure
Diffusion energy of Na+ can be used to transport
other substances across the cell membrane
Aquaporins
small integral membrane channels that facilitate water transport across the plasma membrane of cells in response to osmotic gradients -maintenance of constant water homeostasis
Membranes control the structure and environment of the compartments they define and thereby
the metabolism of these compartments
Size and charge affect
the rate of diffusion across a membrane
glucose and amino acids
transported via facilitated diffusion
primary active transport
-Energy is derived directly from ATP breakdown -Active transport that relies directly on the hydrolysis of ATP.
secondary active transport
-Energy of ions going down its gradient drives the movement of the other substances -But since ionic gradients are maintained by ATP hydrolysis, ATP is the indirect source of energy for this process
P-class pumps
-Get phosphorylated -Move a variety of different ions, mostly cations
Explain the effects of insulin and beta-2 adrenergic agonist on extracellular and intracellular potassium concentrations
-Insulin increases the permeability of many cells to potassium, magnesium and phosphate ions. The effect on potassium is clinically important. Insulin activates sodium-potassium ATPases in many cells, causing a flux of potassium into cells. -Beta2-adrenergic agonists act on beta-2 receptors to drive potassium into the cells.
Transport of ions through proteins
-Ion channels - selectively permeable for certain ions -can be opened or closed by gates
What can cross membranes by simple diffusion?
-Lipophilic molecules:Rate of diffusion proportional to lipid solubility -Water, and small molecules; through channels in membrane spanning proteins. Rate of diffusion is inversely proportional to the size
Hypokalemic periodic paralysis
-caused by mutation of skeletal muscle Na+ channels - manifests as episodic weakness accompanied by low serum potassium levels - triggered by large carbohydrate meal , strenuous exercise, hypothermia
Management of anesthesia for hypokalemic periodic paralysis
-hypothermia must be avoided -large carbohydrate meals should be avoided 24 hours before surgery -glucose-containing solutions and drugs that cause intracellular shift of potassium (beta-adrenergic agonist) should be avoided
function of Na/K ATPase
-maintains NA+ and K+ concentration differences across the cell membrane -establish negative voltage inside the cells -control cell by removing ions from the cell
Active transport
-movement is against the concentration gradient -required energy
Diffusion
-movement is always down the concentration gradient -no energy required
Diseases associated with defective NA+ channels(channelopathies):
-periodic paralysis -paramyotonia congenita -QT syndrome (Type III)
Chemical gradients do not develop spontaneously , cell membranes maintain these gradients by:
-preventing ion flux -active transport of ions from side to side of the plasma membrane
carrier proteins
-they are specific -they are enzyme like -rate of diffusion follows enzyme kinetic rules -carriers exhibit saturation -rates increase with concentration -can be inhibited by specific inhibitors
simple diffusuion
-through the intermolecular spaces or membranes opening without any interaction with CARRIER proteins - can use CHANNEL proteins
Hydrophobic molecules Small, uncharged polar molecules Large, uncharged polar molecules Ions
02, c02, N2- cross the bilayer H20, indole, glycerol- cross the bilayer Glucose, sucrose - don't cross without active transport Cl, K, NA- don't cross with active transport
Steps of Na+/K+ ATPase Pump
1. 3 NA bind to the cytoplasmic side of protein 2. Phosphate is transferred from ATP to protein 3. Phosphorylation changes the shape of the protein , moving NA across the membrane 4. K+ binds to protein , causing phosphate release 5. Release of phosphate changes the shape of the protein , moving K+ to the cytoplasm
ABC superfamily
A large group of integral membrane proteins that often function as ATP-powered membrane transport proteins to move diverse molecules (e.g., phospholipids, cholesterol, sugars, ions, peptides) across cellular membranes.
Which of the following substances normally fails to cross the cell membrane under any circumstance A:Water B:DNA C:Fatty Acid D:Oxygen E:Glucose
B: DNA E: Glucose
Hypertonic solution
Cells lose water , by osmosis and shrink in a hypertonic solution -contains higher concentration of solute than are present inside the cells
Isotonic solutions
Cells retain their normal size and shape -same solute/water concentration as inside cells , water moves in and out
Hypotonic solutions
Cells take on water by osmosis until they become bloated and burst(lyse) -contains a lower concentration of solutes than are present inside cells
What is an example of facilitated transport antiport system
Chloride-bicarbonate transport
Factors affecting net rate of diffusion
Concentration gradient, size of the particles that are diffusing, and temperature of the system affect the rate of diffusion.
Extracellular fluid has high concentration of
NA
life-threatening complications can be caused by ignorance of
Osmosis
Describe how substances get across cell membrane
Passive Transport: Passive transport is the movement of molecules across the cell membrane and does not require energy. It is dependent on the permeability of the cell membrane.There are three main kinds of passive transport - Diffusion, Osmosis and Facilitated Diffusion. Active Transport: is the term used to describe the processes of moving materials through the cell membrane that requires the use of energy. There are three main types of Active Transport: The Sodium-Potassium pump, Exocytosis, and Endocytosis.
How opening and closing of ion gates is controlled
voltage-gating: change of electrical potential across the cell membrane Ligand-gating: binding of chemical substance to the channel mechanical gating: change in membrane tension
Never mix ____________with albumin , it will create a ____________________solution thus causing massive , life-threatening ______________
water hypotonic hemolysis