Module 1: Lecture 4 Flashcards
if a cell does not have a plasma membrane, it is?
not a cell
why do we want the plasma membrane to be flexible?
- for movement of molecules across
- for cells to move and squeeze through
what is another name for the plasma membrane?
cell membrane
the plasma membrane is a bilayer of what?
phospholipids
what is ONE phospholipid made of?
- a negatively charged, polar, hydrophilic head
- two uncharged, nonpolar, hydrophobic tails
the fluid surrounding the outside cell is called?
extracellular fluid
the fluid inside the cell is called?
intracellular fluid
what are the components of the extracellular and intracellular fluid?
water with lots of nutrients, gases and proteins
why is the phospholipid head polar?
its charged with a phosphate group
what are the tails of phospholipids made of?
fatty acids
what happens if a cells plasma membrane bursts and is now open?
the cell dies. a cell needs a plasma membrane and for it to be fully intact.
is the lipid bilayer thick or thin?
very thin (want this so that molecules can transport fast)
what controls movement of molecules into and out of the cell?
the plasma membrane
in the phospholipid bilayer, what decides whether a molecule moves through it?
- different proteins in the composition of the plasma membrane
what does the plasma membrane communicate with?
cell-cell and cell-environment communication
what is making water polar?
the oxygen molecule.
- oxygen is very electronegative so when it bonds with hydrogen, it takes its orbits electrons to form a covalent bond, making it polar.
does the phospholipid need an aid to move into its formation?
no. it does it naturally because the tails repel the water surrounding the plasma membrane
why do we want the plasma membrane to be liquid?
so its flexible so that molecules can move across and move through
how is the plasma membrane liquid?
- the phospholipids are vibrating, twirling and always move around within their own bilayer
- cholesterol is in between the tails of the phospholipids to contribute to stability and fluidity
how many more phospholipid molecules are there than protein molecules? which is larger and heavier in size?
50 times more phospholipid molecules but proteins are larger and take up nearly half the membranes mass
what are channels in the plasma membrane for?
small (< or = 0.8nm), water-soluble molecules (like small ions)
why can’t ions move across the phospholipid bilayer even though they are so so small?
the nonpolar, hydrophobic, fatty acid that doesn’t let water through.
- charged molecules will be much more repelled by a hydrophobic molecule than water
why do we not want ions to move across the phospholipid bilayer freely? (use hydrogen as example)
hydrogen is concentrated in intermembrane space to create a gradient to turn it into ATP. If hydrogen could just cross over, we cannot make ATP
what is a carrier molecule used for?
transfer of specific substances; glucose
what is a docking-marker acceptor for?
- proteins on the inner-side of the plasma membrane that bind lock-and-key fashion with the docking markers of secretory vesicles
what is membrane-bound enzymes for?
enzymes attached to the plasma membrane
why do we want enzymes attached to the plasma membrane?
generally for the process of signaling so that when a cell detects something, the enzyme on/in the plasma membrane will now do something
if a cell can sense something, what is it going to do?
hormone and receptors which are proteins on a membrane. when receptors bind, enzymatic reactions occur and then carrier molecule production increases
what is cell adhesion molecules (CAMS) for?
- communication
- allow cells to stick together
what are peripheral proteins?
proteins that don’t cross the entire membrane. they are just on one side (intracellular or extracellular)
