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