Module 1: Lecture 4

Question 1

if a cell does not have a plasma membrane, it is?

Answer 1

not a cell

Question 2

why do we want the plasma membrane to be flexible?

Answer 2

• for movement of molecules across
• for cells to move and squeeze through

Question 3

what is another name for the plasma membrane?

Answer 3

cell membrane

Question 4

the plasma membrane is a bilayer of what?

Answer 4

phospholipids

Question 5

what is ONE phospholipid made of?

Answer 5

• a negatively charged, polar, hydrophilic head
• two uncharged, nonpolar, hydrophobic tails

Question 6

the fluid surrounding the outside cell is called?

Answer 6

extracellular fluid

Question 7

the fluid inside the cell is called?

Answer 7

intracellular fluid

Question 8

what are the components of the extracellular and intracellular fluid?

Answer 8

water with lots of nutrients, gases and proteins

Question 9

why is the phospholipid head polar?

Answer 9

its charged with a phosphate group

Question 10

what are the tails of phospholipids made of?

Answer 10

fatty acids

Question 11

what happens if a cells plasma membrane bursts and is now open?

Answer 11

the cell dies. a cell needs a plasma membrane and for it to be fully intact.

Question 12

is the lipid bilayer thick or thin?

Answer 12

very thin (want this so that molecules can transport fast)

Question 13

what controls movement of molecules into and out of the cell?

Answer 13

the plasma membrane

Question 14

in the phospholipid bilayer, what decides whether a molecule moves through it?

Answer 14

• different proteins in the composition of the plasma membrane

Question 15

what does the plasma membrane communicate with?

Answer 15

cell-cell and cell-environment communication

Question 16

what is making water polar?

Answer 16

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.

Question 17

does the phospholipid need an aid to move into its formation?

Answer 17

no. it does it naturally because the tails repel the water surrounding the plasma membrane

Question 18

why do we want the plasma membrane to be liquid?

Answer 18

so its flexible so that molecules can move across and move through

Question 19

how is the plasma membrane liquid?

Answer 19

• 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

Question 20

how many more phospholipid molecules are there than protein molecules? which is larger and heavier in size?

Answer 20

50 times more phospholipid molecules but proteins are larger and take up nearly half the membranes mass

Question 21

what are channels in the plasma membrane for?

Answer 21

small (< or = 0.8nm), water-soluble molecules (like small ions)

Question 22

why can’t ions move across the phospholipid bilayer even though they are so so small?

Answer 22

the nonpolar, hydrophobic, fatty acid that doesn’t let water through.
- charged molecules will be much more repelled by a hydrophobic molecule than water

Question 23

why do we not want ions to move across the phospholipid bilayer freely? (use hydrogen as example)

Answer 23

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

Question 24

what is a carrier molecule used for?

Answer 24

transfer of specific substances; glucose

Question 25

what is a docking-marker acceptor for?

Answer 25

• proteins on the inner-side of the plasma membrane that bind lock-and-key fashion with the docking markers of secretory vesicles

Question 26

what is membrane-bound enzymes for?

Answer 26

enzymes attached to the plasma membrane

Question 27

why do we want enzymes attached to the plasma membrane?

Answer 27

generally for the process of signaling so that when a cell detects something, the enzyme on/in the plasma membrane will now do something

Question 28

if a cell can sense something, what is it going to do?

Answer 28

hormone and receptors which are proteins on a membrane. when receptors bind, enzymatic reactions occur and then carrier molecule production increases

Question 29

what is cell adhesion molecules (CAMS) for?

Answer 29

• communication
• allow cells to stick together

Question 30

what are peripheral proteins?

Answer 30

proteins that don’t cross the entire membrane. they are just on one side (intracellular or extracellular)