Cell Transport Flashcards
List some functions of the plasma membrane proteins
- Selective transport of molecules
- Cell recognition via surface antigens
- Cell communication (plasma membrane receptors)
- Tissue organization through adhesion molecules
- Enzymatic activity
- Determination of cell shape by linking the cytosceleton to the membrane
List some functions of the plasma membrane lipids
- Transport of molecules
- Source of second massengers
- Surface
What are different types of transport through the plasma membrane
- simple diffusion
- protein-mediated membrane transport
- vesicular transports
What are examples of protein-mediated membrane transport?
- solute carriers (facilitated diffusion)
- ATP-dependent carriers (pumps)
- ion channels
- water channels
What are examples of vesicular transports?
- endocytosis (pinocytosis, phagocytosis, receptor-mediated endocytosis)
- exocytosis
What is simple diffusion?
- a form of passive transport that works on the basis of a driving chemical gradient (concentration difference)
What is the mechanism of diffusion?
- random movement of solute due to brownian motion
- solute (particle) moves to area of smaller solute concentration
How do you measure the net rate of diffusion?
Fick’s First Law
What is Fick’s First law?
J = DA/ ∆x * ∆c
What do the values of Fick’s First Law stand for?
J = net rate of diffusion (in moles per unit time)
D = diffusion coefficient
A = area, across which the diffusion is occuring
∆x= distance
∆c= concentration difference
What properties effect diffusion?
- the driving force (the concentration gradient)
- thickness
- O2, CO, CO2, NO, urea, hydrophobic hormones
- (H2O, ions, glucose)
- no peptides, no proteins, no disaccharide
What does the rate of diffusion depend on?
hydrophobicity and the size of the solute
What are the two types of protein-mediated membrane transport?
- facilitated trasnport
- active transport
What is facilitated transport?
- passive
- transport not linked to metabolic energy
What is active transport?
- needs ATP (energy)
- direct/primary active transport → pump
- indirect/ secondary active transport → works together with a pump
Protein-mediated membrane transport can be ______ (in regards to number of solute & carried charge)
- uniporter
- cotransporter: sym/anti
- electroneutral
- electrogen
What are properties of facilitated diffusion?
- integral plasma membrane protein mediated
- more rapid than free diffusion
- passive (no energy required)
- driving force is conc. gradient
- saturation kinetics
- chemical specificity
- competition between structurally related molecules
- specific inhibition
What is a water channel?
- passive transport
- driving force is osmosis
- water permeability of lipid bilayer is low
What is osmosis?
- the flow of water in the direction that intends to dilute the other substance
- water flows from higher concentration of water to lower
- water flows from lower concentration of solute (particle) to higher
What is osmotic pressure?
the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane
How can we calculate osmotic pressure?
Van’t Hoff’s Law
What is Van’t Hoff’s Law?
π = RTnc (see notes for what each letter means)
Properties of carriers (enzymes)
energy: passive/ active
transport mode: cycle
speed: slow
kinetics: saturation
Properties of channels
energy: passive
transport mode: gated
speed: fast
kinetic: cannot be saturated
How can you classify membrane carriers?
by number of solutes: uniporter → cotrasnporter (sum/anti)
energetically: passive or active
carried charge: electroneutral → electrogen
What are the units of osmolarity?
mOsm/L
What are the unites of osmolality?
mOsm/kg
What is tonicity?
the effect of a solution on a cell
What happens to the cell volume in the case of an isotonic solution?
cell volume does not change
What happens to the cell volume in the case of an hypertonic solution?
- cell volume decreases
- cell shrivels
What happens to the cell volume in the case of an hypotonic solution?
- cell volume increases
- cell swells; lysis
What are some examples of cell transports?
- Glucose transport
- Cl- HCO3- exchanger
- Na+/ K+ ATPase (Sodium pump)
Name some properties of the glucose transport.
- facilitated diffusion
example: GLUT 1-7 (glucose transporter molecule)
What is the function of GLUT 1-7?
- transports glucose from extracellular compartment to intracellular compartment
- passive transport
- electroneutral -uniporter
What is special about GLUT-2?
they can get information about glucose concentration via beta cells
What is the function of GLUT-4?
- insulin sensitive transporter
found in: skeletal muscle and adipocytes
Name some properties of the Cl-/HCO3- exchanger.
- cotransporter, antiporter
- passive process
- electroneutral
- transports CO2
- found in: RBC membranes
Name some properties of the Sodium pump.
- active transport
- requires ATP
- works against chemical gradient
- electrogenic
- inhibitor: quabain
3 Na+ IC→EC
2 K+ EC→IC
Oncotic pressure
type of osmotic pressure of large molecules such as proteins
What is relative osmotic pressure?
π = RTnc • σ
σ: reflection coefficient
σ = 1 → solute cannot pass (ex. NaCl, sucrose)
σ = 0 → membrane permeable (ex. urea, glucose)
