Human Phys 1.3 Flashcards
What is diffusion?
Random molecular movement (move on their own)
How does diffusion always occur?
Down a concentration gradient (downhill)
What is simple diffusion determined by?
Amount of substance available
Velocity of motion
Number of size and openings (permeability)
What does facilitated diffusion always require?
Carrier protein
What is always true about flow down gradients?
There will always be an energy gradient (supports flow) and a resistance to flow
Flow
Movement of substances from one point in the system to another
Why does flow occur?
Due to the presence of an energy gradient
What can determine the direction of flow?
More than one gradient
What will there always be when it comes to flow?
Some form of resistance
What is true about resistance in flow?
It can be varied or physiologically controlled
Are there multiple gradients during flow?
Yes (working at same time)
What is osmosis?
Flow down gradient
How do molecules diffuse?
Independently of one another
Does the presence of a gradient mean flow will always occur?
No (due to resistance)
Chemical gradient
Flow occurs from higher to lower concentration
Electrical gradient
Flow occurs based on attraction between + and - charges
What is it called when a chemical and electrical gradient are combined?
Electrochemical gradient
Pressure gradient
Behaves same as chemical gradient (high to low pressure)
Mole
6 x 10^23
Equivalent
Used to describe the amount of charged (ionized) solute (moles x valence)
Osmole
The number of particles into which a solute dissociates in solution
Pores
Always open (non gated)
What is selectivity of a pore based on?
Diameter and electrical charge
Channel
Closed (gated)
What are the types of gates that come with a channel?
Voltage gated
Ligand gated
Mechanically gated
Voltage gated
Opens based on electrical charge
Ligand gated
Opens due to molecule binding
Mechanically gated
Opens due to change in pressure
What limits the maximum rate of facilitated diffusion?
Saturation
Speed of conformational change
Saturation
All carrier proteins have a limited number of binding sites (and limited number of carrier proteins)
(Seats available in boat)
Speed of conformational change
The rate of transport can never be greater than the speed of conformational change (how fast the boat can go)
What are the factors that affect net diffusion?
Concentration gradient
Partition coefficient
Diffusion coefficient
Thickness of the membrane
Surface area
Partition coefficient
Decreases the solubility of a solute in oil relative to its solubility in water
Diffusion coefficient
Depends on size of molecule and viscosity of the medium
Thickness of membrane
The greater the distance of diffusion the lower diffusion rate
Surface area
The greater the surface area available the higher rate of diffusion
What are two factors that affect net diffusion if the solute is an electrolyte?
Potential difference
Diffusion potential
When does a diffusion potential occur?
Only if the membrane is permeable to the electrolyte
When will negatively charged molecules stop entering a positively charged cell?
When equilibrium is reached between both the chemical and electrical gradient
