Membranes & transport - membrane transport Flashcards
(30 cards)
What is simple diffusion?
A type of membrane transport involving particles passing directly between phospholipids in the plasma membrane.
Define simple diffusion.
The net movement of a substance from a region of higher concentration to a region of lower concentration due to random motion of molecules or ions.
What causes the random movement of molecules in simple diffusion?
Kinetic energy of the molecules or ions.
What does it mean for molecules to move down a concentration gradient?
Molecules move from an area of higher concentration to an area of lower concentration.
What happens when diffusion occurs for a long enough time period?
Molecules reach equilibrium, being evenly distributed on either side of a membrane.
Give an example of a molecule that moves by simple diffusion.
Oxygen.
How does oxygen diffuse into cells?
From surrounding capillaries due to a concentration gradient created by respiration.
What is another molecule that diffuses by simple diffusion?
Carbon dioxide.
How does carbon dioxide diffuse out of cells?
Into surrounding capillaries due to a concentration gradient created by respiration.
What factors affect the rate of diffusion across a membrane?
- Steepness of the concentration gradient
- Temperature
- Surface area
- Properties of the molecules or ions
How does temperature affect the rate of diffusion?
Higher temperature increases the rate of diffusion due to increased kinetic energy.
How does surface area influence diffusion?
Greater surface area increases the rate of diffusion.
Which type of molecules diffuse more slowly?
Large molecules.
What type of molecules diffuse faster across the phospholipid bilayer?
Uncharged and non-polar molecules.
Fill in the blank: Osmosis is the diffusion of _______ across a partially permeable membrane.
water molecules
How is osmosis related to concentration gradients?
Water moves from a dilute solution to a solution with a higher solute concentration, down its concentration gradient.
What allows water to pass through membranes more freely?
Channel proteins called aquaporins.
Define osmosis in terms of water potential.
The net movement of water molecules from a region of higher water potential to a region of lower water potential.
What is facilitated diffusion?
Diffusion that requires transport proteins to help substances cross the phospholipid bilayer.
What types of substances typically require facilitated diffusion?
- Large molecules
- Polar molecules
- Ions
What are the two types of proteins involved in facilitated diffusion?
- Channel proteins
- Carrier proteins
Is facilitated diffusion an active or passive form of transport?
Passive form of transport.
What is the role of channel proteins?
They allow the passage of specific substances, including charged substances like ions.
What is a unique feature of gated channel proteins?
They can open or close to control the exchange of ions.
