lec 4- membrane transport and potentials

Question 1

what is the plasma membrane made of and what is its function?

Answer 1

The plasma membrane is made of a phospholipid bilayer and it protects the cell, allows entry of materials needed for the cell, facilitates chemical reactions

Question 2

what is selective permeability?

Answer 2

the membrane only allow small and non-polar molecules to pass through easily, and large polar molecules not at all

Question 3

what is diffusion?

Answer 3

Diffusion is the spontaneous movement of small molecules through the membrane

Question 4

what is osmosis?

Answer 4

Osmosis is the diffusion of water through the membrane

Question 5

what is a concentration gradient and what happens when it exists?

Answer 5

a concentration gradient is created by a difference in solute concentrations, and when it exists, it results in a net movement from high-concentration regions to low-concentration regions

Question 6

why is diffusion good?

Answer 6

diffusion is good because it increases entropy which results in an increase of disorder

Question 7

what is equilibrium during diffusion?

Answer 7

Equilibrium during diffusion is when molecules are still moving randomly but no net movement occurs

Question 8

what is passive transport?

Answer 8

Passive transport occurs when a substance diffuses across a membrane in the absence of an outside energy source

Question 9

what are the steps to diffusion?

Answer 9

1. Separation of solutes on both sides of bilayer, both molecules diffuse freely across the bilayer
2. Diffusion, solutes diffuse across the membrane where both undergo a net movement along its own concentration gradient
3. Equilibrium is reached, solutes move back and forth but no net movement occurs

Question 10

during osmosis, which gradients does water move from and to?

Answer 10

During osmosis, water moves from a low solute concentration gradient to a high solute concentration gradient

Question 11

what is hypertonic and what happens to the cell?

Answer 11

An outside solution with a higher concentration is said to be hypertonic to the inside of the cell, the cell will shrink due to water moving out

Question 12

what is hypotonic and what happens to the cell?

Answer 12

An outside solution with a lower concentration is said to be hypotonic to the inside of the cell, the cell will swell due to water moving in

Question 13

what is isotonic and what happens to the cell?

Answer 13

Equal concentration both in and out of cell is called isotonic, cell will remain the same due to no water movement

Question 14

what is a lipid?

Answer 14

Lipids are carbon containing compounds found in organisms, largely nonpolar and hydrophobic

Question 15

what is a hydrocarbon?

Answer 15

Hydrocarbons are molecules that only contain carbon and hydrogen, they are hydrophobic

Question 16

what is a fatty acid?

Answer 16

Fatty acid is a hydrocarbon bonded with a carboxyl group (-COOH), can be saturated or unsaturated

Question 17

what are the three types of lipids?

Answer 17

-Fats are three fatty acids linked with glycerol
-Steroids are a family of lipids with a four ring structure, cholesterol is an important steroid
-Phospholipids are a glycerol linked with a phosphate group (PO4^2-) and to two fatty acids or isoprene (plants)

Question 18

what are phospholipids made of?

Answer 18

Phospholipids consist of a glycerol and phosphate group head which is polar and a tail made of two fatty acid chains which are nonpolar

Question 19

what part of the phospholipid is facing outside and inside?

Answer 19

head (hydrophilic, outside)
tail (hydrophobic, inside)

Question 20

are phospholipids amphipathic?

Answer 20

Yes, they are both hydrophobic and hydrophilic

Question 21

what characteristics do bilayer membranes have?

Answer 21

Membranes are flexible (cells can change shape), repairable, expandable, selectively permeable

Question 22

what factors affect membrane fluidity?

Answer 22

Temperature, number of double bonds between carbons, length of tails, number of cholesterol molecules

Question 23

what does a decrease in temp do to the membrane fluidity?

Answer 23

Decrease in temperature results in decrease of fluidity, decrease in fluidity results in decrease in permeability

Question 24

what does a different in bonds of the tails do to the membrane?

Answer 24

Single bonded tails are saturated which means less permeable, tails with a double bond are unsaturated and have a kink which means they are more permeable

Question 25

what does length of side chains do to the membranes fluidity?

Answer 25

Small length means more fluidity and permeability, long means less fluidity and permeability

Question 26

what type of qualities does a lipid bilayer want to be ideal?

Answer 26

short and unsaturated hydrocarbon tails result in high fluidity and permeability

Question 27

what does increase of cholesterol do to fluidity and permeability?

Answer 27

causes increase in fluidity but decrease in permeability

Question 28

what is homeoviscous adaptation?

Answer 28

changing characters of phospholipid bilayer to adapt to cold or hot environments

Question 29

how do animals change their bilayer in cold environments?

Answer 29

In cold environments fatty acid length is decreased as well as the saturation (increases cholesterol for more fluidity)

Question 30

what are proteins that lodge themselves into the membrane called?

Answer 30

transmembrane proteins

Question 31

what are proteins that bind to the membrane without passing through it called?

Answer 31

peripheral membrane proteins

Question 32

what is the fluid-mosaic model?

Answer 32

The fluid-mosaic model is a model that shows that the membrane is fluid and filled with phospholipids and proteins

Question 33

what are the types of passive transport?

Answer 33

diffusion and facilitated diffusion

Question 34

what is facilitated diffusion?

Answer 34

Facilitated diffusion is when transmembrane proteins assist in passive transport

Question 35

what membrane proteins help in facilitate diffusion?

Answer 35

The two types of transmembrane proteins in facilitated diffusion are channel proteins (selectively admit ions) and carrier proteins (undergo conformational change to transport specific molecules)

Question 36

what is an aquaporin channel?

Answer 36

a channel that only lets water through

Question 37

what does an ion channel do?

Answer 37

allows ions in or out and changes electrical state of membrane

Question 38

what is a gated channel?

Answer 38

it opens or closes in response to the binding of a molecule

Question 39

what is active transport?

Answer 39

the moving of substances against the gradient and requires energy

Question 40

what pump uses ATP and transport specific ions?

Answer 40

Sodium-Potassium Pump

Question 41

what are the steps to sodium-potassium pump?

Answer 41

1. Unbound protein: three binding sites have a high affinity for sodium ions
2. Three sodium ions from inside of the cell bind
3. A phosphate group from ATP binds to the protein causing a conformational change
4. The sodium ions leave and move out of cell
5. Unbound protein: two binding sites have high affinity for potassium ions
6. Potassium ions bind
7. The phosphate group is cleaved/removed from protein allowing change to original form
8. Potassium ions leave into the inside of the cell

Question 42

what is a uniporter?

Answer 42

Uniporter membrane proteins move one solutes down the gradient

Question 43

what is a symporter?

Answer 43

Symporter membrane proteins move two solutes against the gradient

Question 44

what is an antiporter?

Answer 44

Antiporters move two molecules down the gradient in opposite directions

Question 45

how do ions diffuse?

Answer 45

down their electro chemical gradient

Question 46

what are the steps to the electrochemical gradient?

Answer 46

1. no permeability to any ion
2. potassium channel opens resulting in it exiting the cell
3. more potassium cant leave due to concentration gradient pushing back and being repelled back by the electrochemical gradient, resulting in equal gradients