Basic Cell Physiology: Cell Membrane and Transport Flashcards
(55 cards)
Basic function(s) of the plasma membrane
regulate the passage of molecules
Detecting chemical signals from other cells and binding proteins for cell communication
Types of membrane proteins
- Peripheral
- Transmembrane
- Channels/pores
- 7 pass
Carbohydrates role on the plasma membrane
Facilitate the organization of ions that will be going through the membrane
Tight junctions
Cell contact that is made when the EC surfaces of 2 plasma membranes are joined together. No space between
What type of cells are joined by tight junctions
Epithelial cells (intestinal tract)
Gap junction
Two cells linked together by their cytosol. Space in-between
What is the shape of the protein determined by
Sequence of amino acids
Simplest membrane protein
Channel or pore - what goes through the membrane will be based on size and charge of the particle
Ficks Law
J(net flx) = P x Area (Conc out-conc in)
Speed of a molecule
Depends on size and heat of the molecule. i.e. - water moves much faster than glucose because it is so much smaller
Diffusion
The movement of molecules from one spot to another based on random thermal motion (concentration gradients) no energy
Flux
amount of material crossing a surface in a unit of time
One-way flux
some particles will always move back against the gradient regardless of any other factors
net flux-
the difference between flux in and flux out. Will also be greater in the direction of high to low solutes
Factors affecting diffusion
- Temperature
- Mass
- surface area between
- Medium through which the cells are moving. Air is more rapid
What is the major factor limiting diffusion across a membrane
The hydrophobic interior (lipid layer)
Which molecules diffuse rapidly across the membrane
non-polar (because the lipid layer is non-polar)
Which molecules diffuse slowly across the membrane
polar h2o
What are the charges of a cell
EC= + IC= -
How does glucose diffuse across a membrane
Through a transporter protein. Comes into the cell with Na+ (facilitated diffusion)
2 types of mediated transport
- Facilitated diffusion - downhill
2. Active transport - uphill (needs energy)
Which types of transport needs energy
Primary and secondary active transport
Primary active transport
The direct use of ATP to move molecule against the gradient
Secondary active transport
Use of an ion concentration difference to drive the active transport process. The energy from the chemical gradient produces energy need to transport uphill (indirect ATP)
