Organisation of cells Flashcards
which type of cell is compartmentalised?
eukaryotic
what are the 5 functions of membranes?
- transport
- enzyme activity
- cell communication
- connecting cells
- cell recognition
what is the membrane structure?
- 2 molecules thick
- Form closed boundaries (compartments)
- Most membranes 5 – 10 nm thick
what are membranes composed of?
lipids and proteins
what are phospholipids?
phosphate containing lipids
what is the most abundant membrane lipid?
phospholipids
how many different types of lipids have been identified in membranes?
500-1000
what are the 2 types of membrane movement?
latertal movement and flip-flop movement
how often does lateral movement occur?
~10^7 times per second
how often does flip-flop movement occur?
<1 per month (uncatalysed)
what 3 things impact the fluidity of a membrane?
non-covalent bonds, membrane composition and temperature.
do nonpolar or polar molecules pass through membranes rapidly?
nonpolar (hydrophobic) as they can disolve in the lipid bilayer
how much of a cells energy is devoted to running the Na+/K+ pump?
1/3
why is the sodium-potassium pump so important?
- Cells contain many solutes trapped within the cell by the plasma membrane: Proteins, Sugars, Amino acids, Nucleotides, Ions
- Therefore water will move into the cell by osmosis. If this is unregulated the cell will burst.
how do cells control intracellular omolarity?
by actively pumping out inorganic ions such as Na+ across the plasma membrane so that their cytoplasm contains a lower concentration of inorganic ions than the extracellular fluid, thereby compensating for their excess of organic solutes.
