Membrane Transport (1) Flashcards
Exam 1
How do cells communicate?
Cells communicate with each other by secreting chemical regulators into the extracellular environment
Cells receive nourishment from and release wastes into the ____ ____
extracellular environment
What does the extracellular environment include?
everything located outside the cells
What does body fluid refer to?
body fluid refers to the watery solution of dissolved substances (oxygen, nutrients, and wastes) present in the body
Intracellular Fluid Definition
fluid located inside the cells
~67% of all fluid in the body
Extracellular Fluid Definition
Fluid in the blood and in spaces surrounding the cells
remaining ~33%
What makes up extracellular fluid?
20-25% is in the fluid portion of blood (plasma)
75-80% lies around and between cells (interstitial fluid)
Interstitium Definition
space containing interstitial fluid
In membrane transport, what changes the conformation to move a molecule/ion?
carrier proteins
In membrane transport, what provides selective channels for the orient of specific substances (e.g., specific ions, water)?
Channel proteins
True or False:
The plasma membrane is selectively permeable
True
What are the two categories to enter membrane transport?
- Non-carrier mediated
2. Carrier mediated
What is non-carrier mediated?
simple diffusion, osmosis (filtration capillaries)
What type of transport happens in non-carrier mediated and what is the definition of that transport?
Active Transport- no energy, moved down gradient (high to low concentration)
Random molecular motion eventually evens things out
What type of transport occurs in carrier mediated and what is the definition of that transport?
Active Transport- against gradient (low to high concentration)
needs transport protein and ATP
Simple Diffusion Definition?
net movement of particles from high concentration to lower concentration
(down the gradients, spontaneous motion)
Does simple diffusion require a membrane?
No, simple diffusion does not require a membrane
if there is a membrane, substances will diffuse is the membrane in permeable
What are diffusion rates?
How quickly a cell can acquire or eliminate wastes
What factors effect simple diffusion rate through a membrane?
- temperature (higher temp, faster particle motion)
- molecular weight (larger molecular size, slower diffusion)
- concentration gradient steepness (higher gradient, faster rate)
- Membrane Surface Area (higher SA, faster rate-places like intestines/lungs/kidneys)
- membrane permeability (higher permeability, faster rate)
Osmosis Definition
the net flow of water through a selectively permeable membrane
Osmosis moved from __ concentration to __ water concentration
high
low
What are aquaporins?
allows water to move across the membrane
- -specialized channel proteins
- -different by cell (install channels based on conditions)
What is osmotic pressure?
pressure required to stop osmosis
measure of how strongly a solution draws water
___ solute concentration the __ the pressure
greater
greater
What is molarity?
number of molecules of solute per liter of a solution
same molecule number
Physiological impact of a chemical depends on how many ___ of it are present in a given ___
molecules
volume
How many molecules are in a mole?
6.022 x10^23 molecules in a mole
What is osmolarity?
the number of osmoles per liter of solution
(the total number of solute particles (concentration) in a solution
one osmole (osm) = __ ___ of dissolved particle
1 mole
___ osmolarity = ___ water concentration
higher
lower
What is tonicity?
ability of a surrounding solution (bath) to affect fluid volume and pressure in a cell
concentration of ___ vs ___ causes water to move in or out of a cell
solutes
water
Effect of osmosis on cells in isotonic solution
- no change in cell volume
- concentrations of non permeating solutes in bath of ICF are the same
- 0.9% saline isotonic to red blood cells
Effect of osmosis on cells in hypotonic solution
- concentration of water outside the cell is greater than inside the cell
- cell gains water
- lysis (cells may burst)
(blood hemolysis)
Effect of osmosis on cells in hypertonic solution
- causes cell to lose water and shrivel (crenate)
- ECF has a higher concentration of non permeating solutes than ICF
Ligand Definition and what determines it
Chemical that binds (reversibly) to a receptor site on a protein
–charges/shapes must be complementary
Determined by conformational shape of the protein
Chemical Specificity Definition and what does it determine
ability of a protein-binding site to bind specific ligands
determines what can actually bind to the binding site
What is the shape of proteins determined by?
determined by amino acid sequence
different amino acid sequences are going to lead to different shapes which will lead to different binding sites
True or False
All protein sites only bind to one ligand
False
some protein sites only bind to one ligand; others bind to many
Affinity Definition and what does it determine
strength of ligand-protein binding
determines how likely that the particular bound ligand will leave
Chemical specificity depends on the ___; affinity depends on the ____ of the liquid and protein attraction
- shape
- strength
What equals a high affinity?
Opposite charges + ligand shape + binding site shape
Saturation definition
fraction of total binding sites that are occupied at any given time
Why is there competition among different ligands for binding sites?
influenced by the affinity this then impacts the saturation
What is carrier-mediated transport?
use a membrane protein to transport substances across membrane
What are the three kinds of carriers in carrier- mediated transport?
- uniport (carries one type of solute)
- . symport (two or more solutes, moving in the same direction at the same time)
- antiport (two or more solutes, moving in opposite directions)
What is an example of uniport?
calcium pump
What is an example of symport?
sodium-glucose transporters
What is an example of antiport?
sodium-potassium pump
What do the three mechanisms of carrier-mediated transport use?
- facilitated diffusion
- primary active transport
- secondary active transport
Facilitated diffusion is where…..
a carrier moves a solute from hight to low concentration (down the gradient)
Primary active transport is where…
a substance moves through a membrane against the gradient
Secondary active transport is where…
the carrier moves solute through a membrane (uses ATP indirectly)
(uses a combination of facilitated diffusion [symport] with primary active transport [antiport])
What does each cycle of the sodium-potassium pump consume?
1 ATP and exchanges 3 sodium for one potassium
What is the purpose of the sodium-potassium pump?
-keep potassium concentration higher and sodium concentration lower inside the cell
___ ___ influences osmosis which influences ____ ___
solute concentration
cell volume
Carrier-mediated transport is a process where….
solute particles move through a membrane by means of a transport protein (uniport, symport, antiport)
ATP is not necessary in ___ ___
facilitated diffusion
ATP is necessary in ____ ___ ____
Primary active transport
What are the three things included in endocytosis?
- pinocytosis
- phagocytosis
- receptor-mediated endocytosis
What is pinocytosis?
“cell drinking” - droplets of ECF containing molecules
What is Phagocytosis?
“cell eating” - cell surround, engulfs, and digests particle
What is receptor-mediated endocytosis?
particles bind to specific receptors on plasma membrane
What happens in Exocytosis?
- Discharges material
- Replaces plasma membrane removed by endocytosis
What is transcytosis?
transport of material across the cell
capture on one side; release on the other
What do receptor- mediated endocytosis and exocytosis do in transcytosis?
receptor-mediated endocytosis moved it into the cell and exocytosis moves it out the other side
