What are the conditions that need to be met for cells to survive?
- Exchange between neighbouring cells
- Exchange within the cell itself (intracellular environment)
- Exchange between the surrounding intercellular medium (extracellular matrix)
What affects rates of facilitated diffusion?
- The concentration gradient
What are active transport systems usually inhibited by?
Low temperatures
What energy does the secondary active transport use?
The electrochemical gradient
Why do some cells produce and accumulate secretory vesicles?
To be able to release large amounts of active molecules on demand
What are two general mechanisms involved in membrane transport?
Macrotransfer and microtransfer
Macrotransfer?
- Transport of macromolecules
- Only brings materials into endosomes or lysosomes within the cytoplasm
Microtransfer?
- Transfer of small molecules and ions across the cell membrane, both external and internal
What must happen for molecules to be absorbed into the cytoplasm?
They must cross the surrounding membrane
What are two different mechanisms for the microtransfer of biomolecules?
- Passive transport (simple diffusion)
- Active transport (requires energy)
Brownian movement?
The first time someone indirectly observed the passive transport of biomolecules
What is passive transport?
The simple diffusion of substances
What is diffusion dependent on?
It is dependent on the movement of molecules due to their kinetic energy (high concentration to low concentration)
When does movement in a cell stop?
When the concentration equilibrium gradient constant reaches 0
Facilitated transport?
- A passive transport system, since it uses no energy
- Uses a set of carrier proteins, which are highly selective
Active transport?
- Some macromolecules don’t pass freely through the cell membranes, so these molecules require the use of pores or channels (membrane transport proteins)
- Requires energy (ATP)
Primary active transport?
Moves molecules against their electrochemical gradient by using ATP
Secondary active transport?
Moves molecules together through symport (in the same direction), or antiport (in opposite directions)
