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
