Lecture #6 - Structure + Organisation of Cell Flashcards
Anything inside the cell is……and anything outside is……
Alive inside and dead outside
What does a cell membrane do?
Provides special conditions within the cell (separates alive from dead)
Provides a SEMI PERMEABLE barrier so can CONTROL movement of substances
What must a cell do? (5 things)
- MANUFACTURE cellular materials (eg macromolecules)
- OBTAIN raw materials (aa’, glucose etc from environ)
- REMOVE wastes (toxic to cell)
- GENERATE the required energy
- CONTROL all of the above (else could become a cancerous cell)
Basically, do many different processes so needa separate conditions
Organelles
- Provide….
- Keep….
- Allow….
- Form….
- Package…..
- Form SPECIAL CONDITIONS for specific processes
- Keep INCOMPATIBLE processes apart
- Allow HIGH CONCENTRATIONS of substances
- Form CONCENTRATION gradients (for like power providing etc)
- Package for TRANSPORT or export (vesicles)
Cell’s got many different functions so needa keep separate compartments - organelles
What’s the basic structure of plasma membrane?
Two layers of phospholipids - they AREN’T STATIC (membrane associated proteins FLOAT in membrane)
Hydrophilic phosphate groups on the outside (because environment is watery)
Hydrophobic fatty acids inside (composition of acid affects membrane fluidity)
Hydrophilic phosphate groups
Unsaturated tails:
- Kinks or nah?
- Fluid or viscous?
- They HAVE kinks
2. Make membrane more FLUID (can lower the freezing point) - prevents packing of tails
Saturated tails:
- Kinks or nah?
- Fluid or viscous?
- NO kinks
2. Make membrane more VISCOUS because allow tails to pack together
Cholesterol is “fluidity buffer” - why?
High/moderate/body temps:
REDUCES fluidity by restraining phospholipid movement
Low temps:
Hinders solidification by disrupting the regular packing of phospholipids - INCREASES fluidity
Phospholipid bilayer is permeable to…..and restricts movement of…..
Permeable to LIPID SOLUBLE (hydrophobic) molecules eg steroid hormones, gasses down conc grad (I think only relatively small molecules?)
Restricts movement of WATER SOLUBLE and CHARGED molecules e.g. glucose, ions, water
Facilitated diffusion
- What is it?
- Involves?
- Passive or active?
Movement of these hydrophilic molecules requires membrane proteins:
- Movement of specific substances down their concentration gradient
- Involves channels or carrier
proteins
3. No energy input - passive
Channels may be regulated (gates)
- Voltage gated open…
- Ligand-gated open….
- Voltage - response to CHANGE IN VOLTAGE - allow ion influxes
- Ligand - response to an EXTRACELLULAR SIGNAL (signals from one cell to another)
Both passive
Active transport
- What is it?
- Involves?
- Passive or active?
- Movement of specific substances against their concentration gradient
- Involves pumps
- Requires energy input - ATP (active)
Active transport - direct and indirect
Direct/primary: involves an energy expending conformational change in the membrane protein to transport a specific molecule or ion across the membrane.
Indirect/secondary: utilizes energy directly to generate a transmembrane gradient down which ions move and then up or down which the coupled molecule or ion of interest is transported indirectly.
Co-transport definition
A transport protein (cotransporter) can couple the “downhill” diffusion of the solute to the “uphill” transport of a second substance against its own conc grad.
Membrane proteins
- Are…
- They have….
- Give cell it’s “….”
- Are transporters
- Have roles specific to cell type other than transport
- Give cell it’s character
