Basic cell physiology Flashcards
What is ECF?
Extracellular fluid
What are homeostatic mechanisms?
A dynamic equilibrium that maintains a specific sets of thresholds compatible for life -> to detect and respond to deviations from pH 7.4
What is the osmolarity of blood plasma?
300 mOsM - equal amount of water in blood cell and plasma
What is osmolarity?
Concentration of osmotically active particles
What is tonicity of a solution?
Describes the cell volume change that occurs at equilibrium if the cell is placed in that solution
Explain hypotonic, hypertonic and isotonic solutions
Tonicity Osmolarity
- hypotonic - hypoosmotic
- hypertonic - hyperosmotic
- isotonic - isosmotic
hypo: cells swell - net influx of H2O into ICF at equilibrium
hyper: cells shrink - net H2O loss to ECF at equilibrium
iso: normal cells - no net movement between ICF and ECF
What determines whether a substance can pass through a cell membrane?
Lipid and protein composition
How is the membrane permeable or impermeable to a solution?
Membrane is permeable to solution if it allows it in.
Membrane is impermeable to solution if it doesn’t allow it in
What type of molecules can move easily across cell membranes?
Oxygen, carbon dioxide and lipids
What molecules move across cell membrane with more difficulty?
Polar molecules and large molecules (proteins)
What is diffusion?
Passive transport of molecules down a chemical (concentration) gradient -> higher concentration to lower concentration
Which is more likely to cross cell membrane by simple diffusion: fatty acid or a glucose molecule?
Fatty acid because it is lipophilic
What is osmosis?
Passive movement of water molecules from regions of relatively high H2O potential to regions of low H2O potential through a differentially permeable membrane
Do cell membranes have specific channels for molecules?
Yes. Example: glucose -> glucose transporter in membrane
Explain active transport
Moves molecules against their concentration gradient and requires energy
Primary active transport: ATP used
Secondary active transport: indirectly driven by ATP
Name two ways channels differ from carriers
Channel proteins form continuous connections between two sides of membrane and transport molecule faster
What can pass through open channels?
Ions and water molecules
What is the most important primary active transport?
Na+/K+ ATP (Sodium/Potassium ATPase)
- Pumps NA+ out and K+ into cell
- Maintain concentration gradient of Na+ and K+
- Transporter protein to pump 3NA+ out and 2K+ in
True or false:
ICF has higher NA+ concentration than the ECF
False:
ICF: low Na+ / high K+
ECF: high Na+ / low K+
Which are the protein-mediated transporters?
Structural proteins: maintain cell shape
Enzymes: catalyze chemical reactions and transport signals across membrane
Receptor proteins: part of body signaling system
Transporter proteins: move molecules in and out
What is resting membrane potential?
-70 mV - electrical gradient that exists between ECF and ICF
- inside of cell negative
What primary ion determines the resting membrane potential?
K+
How does Na+/K+ ATPase help maintain the RMP?
Removing Na+ that leaks into cell and returning K+ that has leaked out
