Structure and Function of the Cell Membrane

Question 1

what are the two main components of cell membranes?

Answer 1

phospholipids and proteins

Question 2

what structural property makes phospholipids form bilayers in water?

Answer 2

their amphipathic nature

Question 3

which part of the phospholipid is hydrophobic?

Answer 3

the fatty acid tails

Question 4

which part of the phospholipid is hydrophilic?

Answer 4

the polar head groups

Question 5

what model describes the dynamic and fluid nature of the membrane?

Answer 5

the fluid mosaic model

Question 6

what affects membrane fluidity?

Answer 6

cholesterol content and temperature

Question 7

what is selective permeabilty?

Answer 7

the ability of the membrane to regulate which substances can cross it

Question 8

what types of molecules diffuse easily through the lipid bilayer?

Answer 8

small, non-polar, lipid-soluble molecules

Question 9

what’s osmosis?

Answer 9

the passive net movement of water across a semi-permeable membrane

Question 10

what’s tonicity?

Answer 10

how a solution affects cell volume based on solute permeability

Question 11

what’s the role of aquaporins?

Answer 11

to facilitate rapid osmotic water transport

Question 12

what defines an integral membrane protein?

Answer 12

it spans the lipid bilayer and is amphipathic

Question 13

how do peripheral proteins interact with the membrane?

Answer 13

via non-covalent interactions with integral proteins or lipids

Question 14

what is membrane potential?

Answer 14

a voltage across the membrane due to ion gradients

Question 15

what percentage of resting cell energy maintains ion gradients?

Answer 15

approximately 30%

Question 16

why is membrane fluidity important for cell function?

Answer 16

enables protein movement, signal transduction, and membrane reshaping for processes like endocytosis

Question 17

how does cholesterol act as a membrane fluidity buffer?

Answer 17

it prevents excessive fluidity at high temperatures and rigidity at low temperatures

Question 18

why can’t charged ions freely cross the phospholipid bilayer?

Answer 18

the hydrophobic core is highly impermeable to charged particles

Question 19

what’s the importance of asymmetric lipid distribution?

Answer 19

it affects membrane curvature and protein signalling

Question 20

how does diffusion differ from osmosis?

Answer 20

diffusion is the movement of solutes; osmosis is the movement of water

Question 21

why do RBCs lyse in hypotonic solutions?

Answer 21

water enters the cell due to osmotic imbalance, causing swelling and bursting

Question 22

how does the membrane maintain homeostasis?

Answer 22

by regulating substance entry and exit, and maintaining ion gradients

Question 23

why do larger molecules diffuse slower than smaller ones?

Answer 23

because of greater mass and resistance

Question 24

how is ATP involved in membrane transport?

Answer 24

it powers pumps that maintain ion gradients like Na+/K+ ATPase

Question 25

what happens to water movement if solutes can cross the membrane?

Answer 25

the tonicity effect is reduced or becomes nullified

Question 26

why is 'flip flop' of lipids rare?

Answer 26

because it requires significant energy to move hydrophilic heads through the hydrophobic core

Question 27

how do membrane proteins assist impermeable molecules?

Answer 27

through channels or transporters that facilitate or actively move them across

Question 28

what causes crenation in cells?

Answer 28

exposure to hypertonic solutions, leading to water loss and shrinkage

Question 29

what role does membrane potential play in nerve function?

Answer 29

it enables the transmission of electrical signals along neurons

Question 30

why are membranes compared to capacitors?

Answer 30

because they store electrical charge by separating ions across the bilayer

Question 31

the ___ model describes the membrane as a fluid structure with proteins embedded in or attached to a bilayer of phospholipids

Answer 31

fluid mosaic

Question 32

phospholipids form a bilayer in aqueous environments due to their ___ nature

Answer 32

amphipathic

Question 33

the ___ heads of phospholipids face the aqueous environments inside and outside the cell

Answer 33

hydrophilic (polar)

Question 34

the membrane is most permeable to ___ molecules like O2, N2, and steroids

Answer 34

small nonpolar

Question 35

movement of water form a hypotonic to a hypertonic solution is called ___

Answer 35

osmosis

Question 36

___ is the minimum pressure required to prevent osmosis

Answer 36

osmotic pressure

Question 37

cholesterol ___ membrane fluidity at low temperatures, and ___ it at high temperatures

Answer 37

increases; decreases

Question 38

membrane proteins that span the bilayer and are amphipathic are called ___ proteins

Answer 38

integral

Question 39

peripheral proteins are attached to membrane surfaces through ___ interactions

Answer 39

non-covalent

Question 40

only ___ solutes contribute to tonicity

Answer 40

non-penetrating

Question 41

ATP-powered pumps maintain ion gradients by using energy from ___

Answer 41

ATP hydrolysis

Question 42

the ___ gradient combines both concentration and electrical gradients

Answer 42

electrochemical

Question 43

in the cell membrane, ___ fatty acids increase fluidity by preventing tight lipid packing

Answer 43

unsaturated

Question 44

the property that allows lipids and proteins to move within the membrane plane is called ___

Answer 44

lateral diffusion

Question 45

diffusion is a ___ process that doesn't require cellular energy

Answer 45

passive