Cell Membrane Transport Flashcards
What is diffusion
Process of moving solute molecules away from an area of high concentration towards area of low concentration
Down the concentration gradient
No external energy just kinetic energy of molecules is what type of diffusion
Passive
How long does diffusion occur for
Until equilibrium is reached
Explain the rate of diffusion
Fast over short distances
Slow over long distances
Distance squared relationship
Rate of diffusion is faster at high temp
Rate of diffusion is faster for small molecules
Rate of diffusion is slower across a membrane
Simple diffusion
Across no membrane means diffusion is fast
Across a semipermeable membrane allows selected solutes to pass but more slowly
And some solutes can’t pass
What affects the diffusion of Solutes across a cell membrane
The type of molecule
Concentration gradient
Temperature
Surface area
Composition of membrane
How does the type of molecule affect its diffusion rate
Size (two big)
Polar or non polar
Hydrophobic non polar = pass through
Small uncharged polar molecules = pass
Large uncharted polar molecules = no pass
Charged molecules = no pass
What are hydrophobic non polar molecules
O2 CO2 Lipids Steroids Fat soluble molecules
What are small uncharged polar molecules
Urea
H2O
Large uncharged polar molecules
Glucose
Proteins
Amino acids
What are charged molecules
Ions
How does the composition of membrane affect diffusion
Simple bilayer vs many proteins and extracellular matrix
Types of phospholipids and sphingolipids
Presence of cholesterol
What is ficks law of diffusion
Rate of diffusion
Surface area x concentration gradient x membrane permeability
What is liposomal drug delivery
Some drugs may have low bioavailability due to poor solubility
Some drugs may be toxic at useful doses and must be targeted to a specific cell type
Liposomal drug delivery is an emerging technology that may help address these issues
Body fluids are in two compartments ____
Extracellular fluid
Intracellular fluid
Intracellular fluid
Is 2/3 of the total body water volume. Material moving into and out of the ICF must cross the cell membrane
Extracellular fluid
Includes all fluid outside the cells. The ECF is 1/3 of the body fluid volume
The extracellular fluid consists of
Interstitial fluid
- which lies between the circulatory system and the cells is 75% of the ECF volume
Plasma
- the liquid matrix of blood is 25% of the ECF volume
Define osmosis
The diffusion of water
Water can have a concentration gradient and will diffuse down the gradient
Pure water has the highest concentration of water
Solutes lower the concentration of water
Movement of water can cause pressure
How to compare osmolarities
1 glucose = 1 OsM
2 glucose = 2 OsM
1 NaCl = OsM
Higher OsM means ____
Lower OsM means _____
hyperosmotic
Hyposomotic
Why is osmolarity important
Changing osmolarity of the extracellular solution causes redistribution of water and some solutes in cells
This causes cells to shrink or swell
The ability of a solution to shrink or swell cells is its
Tonicity
What is the difference between osmolarity and tonicity
Osmolarity describes only the number of solute molecules in a cell
Osmolarity can compare any two solutions
Does not tell if a cell swells or shrinks
Tonicity is a comparative term describes whether a cell changes volume
Tonicity compares a solution to a cells intracellular solution
Specifically tells if a cell swells or shrinks
Tonicity depends on _____
Concentration of penetrating and non penetrating solutes
Penetrating solutes
Small polar and non polar molecules
For example urea glycerol ethanol
Non penetrating solutes
Ions and larger polar molecules
For example Na+ glucose amino acids
Hyposmotic solutions are always ____
Hypotonic
Intracellular solutes are _____
Non penetrating
Water will flow into the compartment that contains the ___ concentration of ____ solutes
Higher
Nonpenetrating
A _____ is a water filled pore. Can open to both sides
Channel protein
What are two examples of channel proteins
Water channels
Ion channels
What are two types of channel proteins
Gated
Open
____ NEVER form an open channel between the two sides of the membrane
Carrier proteins
What are three types of carrier proteins
Uniport (one molecule through)
Symport (two molecules through same direction)
Antiport (two molecules through different directions)
Describe carrier protein process
Passage open to one side
Conformational changes occur
Transition stage with both gates closed
Conformational changes
Passage open to other side
What are the three categories of energy carrier proteins
Facilitated diffusion
Primary active transport
Secondary active transport
Moving a molecule across the membrane via a carrier protein
Facilitated diffusion
True or false
Facilitated diffusion requires ATP
False does not require ATP
What’s another name for facilitated diffusion
Passive transport
True or false
Facilitated diffusion cannot accumulate solute against a concentration gradient
True
What is an example of facilitated diffusion
Glucose transporter
explain the facilitated diffusion of glucose
High concentration of glucose outside of the cell
Glucose moves through FD Into the cell from high to low
Explain primary active transport
Uses ATP
Establishes gradients
Sometimes called pumps
What are the most common molecules to pass through the primary active transport
Na
K
ATPase
(Ca H as well)
Describe primary active transport steps
3 Na from the ICF moves into the protein and fits in the walls
ATP is used to close the gates turns to ADP
Protein changes and 3 Na released into ECF
2 K from the ECF moves into the protein and fits in the walls
ATP and protein changes
2 K is released into ICF
What is the Na K ATPase pump
Pumps 2 K ions INTO THE CELL
Removes 3 Na ions OUT OF THE CELL
Hydrolyses ATP
This pump accounts for 20 watts of the 100 watts the body produces
Secondary active transport
Active transport
Does not directly utilize ATP as a source of energy
Uses the concentration gradient of one molecule/ions to move another AGAINST its gradient
What’s an example of a secondary active transporter
Na glucose
Explain secondary active transport
Na binds to the carrier from the ECF
Na binding creates a site for glucose
The glucose binding changes the carrier conformation and opens the protein to the inside
Na is released into the cytosol of the cell and glucose follows
Epithelial transport utilizes what types of transport
Facilitated diffusion
Primary active transport
Secondary active transport
Transport of material from the lumen of an organ to the ECF is called ____
Absorption
Describe the trans-epithelial absorption of glucose
Na glucose symporter brings glucose into the cell AGAINST its gradient using energy stored in the NA concentration gradient
(Primary active transport)
GLUT transporter transfers glucose to ECF by facilitated diffusion
(Secondary active transport)
Na K ATPase pumps Na out of the cell keeping ICF Na concentration low
(Facilitated diffusion)
