Cell Membrane Structure and Function (week 2)

Question 1

what is the function of the phospholipid bilayer?

Answer 1

1. creates a barrier
2. protects intracellular space
3. regulates what enters and leaves a cell (semipermeable)

Question 2

what make up integral proteins?

Answer 2

transport and receptors

Question 3

function of peripheral proteins

Answer 3

tethering points for cytoskeleton and enzymes

Question 4

what make up integral proteins?

Answer 4

support and enzyme proteins

Question 5

function of integral proteins

Answer 5

channel/carriers + receptors

Question 6

function of cholesterol

Answer 6

1. keeps membrane integrity, particularly at high temps
2. maintains membrane integrity at more extreme temperature
   conditions.
3. reduces fluidity at extreme high temperatures and increases fluidity at extreme low temperatures
4. prevents membranes from being too fluid and too permeable at warmer temperatures.
5. separates the phospholipids, preventing them from crystallizing at lower temperatures,

Question 7

functions of glycoproteins/lipids

Answer 7

cell ID, cell to cell interaction

Question 8

what happens when you increase cholesterol?

Answer 8

slightly reduces membrane permeability

Question 9

what are integral proteins

Answer 9

proteins that penetrate the membrane

Question 10

why are the heads hydrophilic?

Answer 10

phosphates are polar since they are negatively charged

Question 11

why are the tails hydrophobic?

Answer 11

Since they are composed of hydrogen and carbon atoms, which are non polar

Question 12

what factors increase membrane permeability/fluidity?

Answer 12

1. Increase temperature
2. šIncrease amount of unsaturated bonds
3. Make fatty acid tails shorter
4. Reduce concentration of cholesterol

Question 13

what factors decrease membrane permeability/fluidity?

Answer 13

1. Decreases temperature
2. Decrease amount of unsaturated bonds
3. Make fatty acid tails longer
4. Increase concentration of cholesterol

Question 14

passive transport

Answer 14

no ATP needed (high to low concentration to achieve equilibrium)

Question 15

active transport

Answer 15

ATP needed (low to high concentration gradient)

Question 16

which types of molecules have the hardest time passing through?

Answer 16

small non-polar molecules and large polar molecules (without a channel)

Question 17

which types of molecules have the easiest time passing through?

Answer 17

large non-polar (steroid hormones) and small, charged molecules (h2O)

Question 18

why do ions need a channel?

Answer 18

due to their charge

Question 19

what is osmosis

Answer 19

movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules, through a cell’s partially permeable membrane

Question 20

what is diffusion

Answer 20

1.Spontaneous movement of particles from an area of high concentration to an area of low concentration
2. Does not require energy
3. Occurs via random kinetic movement
4. Net diffusion stops when equilibrium is reached
5. Molecules can continue to move, but no net change in concentration
6. Diffusion of one compound doesn’t depend on the diffusion of another compound

Question 21

isotonic

Answer 21

same concentration as cytoplasm, in equilibrium (no change to cell)

Question 22

Hypotonic

Answer 22

lower concentration than cytoplasm; cell swells and bursts

Question 23

Hypertonic

Answer 23

higher concentration than cytoplasm; cells shrink and burst

Question 24

what are some of the factors that influence that ease by which substances can cross the cell membrane?

Answer 24

solubility (polar vs. non polar), molecular size, charge, presence of channel/carrier

Question 25

sequence the following in order of what can easily pass to cannot pass through the cell membrane: oxygen, potassium, glucose, water

Answer 25

oxygen, water, glucose, potassium

Question 26

what substances require move via facilitated transport methods?

Answer 26

ions, polar large molecules (glucose, amino acids, protein-based hormones)

Question 27

what is facilitated diffusion?

Answer 27

1. Allows diffusion of large, membrane insoluble compounds such as sugars, amino acids, and ions across a biological membrane down their concentration gradients
2. Does not require energy (passive)
3. Highly Selective
   - Substance binds to membrane-spanning transport protein - Binding alters protein conformation, exposing the other surface
   - Movement rate of particles reaches a max because there are only so many transporter

Question 28

what are the 3 types of channel variations?

Answer 28

1. Uniport (transport of one substance across a membrane
2. Symport (Transport of two or more
   substances one direction)
3. Antiport (Transport of two or more substances in opposite directions)

Question 29

what are the types of ion channels?

Answer 29

leakage, ligand gated, mechanically gated, voltage gated

Question 30

leakage channels

Answer 30

no stimuli bc they are always open

Question 31

ligand gated channels

Answer 31

ligand binding

Question 32

mechanically gated channels

Answer 32

pressure/mechanical change

Question 33

voltage gated channels

Answer 33

change in membrane voltage

Question 34

exocytosis (passive)

Answer 34

large wastes or cell products are released from inside to outside a cell

Question 35

endocytosis (osmosis)

Answer 35

large particles are surrounded by the membrane and taken into the cell

Question 36

equilibrium (active)

Answer 36

a state reached when particles continue to move but in equal amounts in and out of the cell

Question 37

kinetic energy

Answer 37

energy of motion/movement (ex: water falling over a waterfall or throwing a football)

Question 38

potential energy

Answer 38

stored energy (ex: stored in springs of mattresses or stored within bonds of molecule)

Question 39

Phagocytosis

Answer 39

large particles, ex: bacteria

Question 40

pinocytosis

Answer 40

anything that is in the extracellular liquid

Question 41

receptor-mediated endocytosis

Answer 41

specific ligands, ex: cholesterol