Membrane Transport

Question 1

what living cells need to do for survival

Answer 1

maintain an internal ion composition

Question 2

simple diffusion

Answer 2

-small polar and lipid soluble substances eg water, alcohol, fatty acid
-difuse directly thru the lipid bilayer
-high to low concentration

Question 3

facilitated diffusion

Answer 3

-larger and polar molecules eg glucose amino acid
-transported substances bind to carrier protein or pass thru channel

Question 4

osmosis

Answer 4

movement of water

Question 5

carrier mediated facilitated diffusion

Answer 5

via protein carrier, binding of substrate cause shape change in transport protein

Question 6

channel mediated facilitated diffusion

Answer 6

thru a channel, nostly ions selected based on size and charge

Question 7

osmosis

Answer 7

diffusion thru aquaporin or lipid bilayer

Question 8

factors that influence molecules moving across a cell membrane

Answer 8

-size
-lipid solubility
-temperature
-gradient
-distance to diffuse

Question 9

osmosis definition

Answer 9

net diffusion of water across membrane

Question 10

osmosis occurs when

Answer 10

-solutes cannot cross the membrane (no diffusion) so the solvent (water) crosses the membrane
-water molecules diffuse across membrane towards solution w more solute
-volume infreases on the side w more solute

Question 11

animal cell is best in an __ environment

Answer 11

isotonic

Question 12

plant cells are turgid and healthies in ___ environment

Answer 12

hypotonic

Question 13

direction of transport depends on

Answer 13

the relative concentration of the solute

Question 14

passive transport

Answer 14

solute at higher concentration outside the cell will move spontaneously across the membrane down its concentration gradient eithout energy by its membrane transport protein

Question 15

active transport

Answer 15

-solute move against its concentration graduent with the help of transport protein (transporter) with energy . because they drive the transport of solutes against concentration gradient, transporters are called pumps

Question 16

two types of membrane transport protein

Answer 16

transporter and channel

Question 17

difference btw transporter and channel

Answer 17

the way they descriminate solutes than can pass thru

Question 18

transporter (carriers)

Answer 18

-provide private passageway across tge membrane
-highly specific and selective
-eg transport protein only allow passage for na+ but not k+
-allows passage only to those molecules or ions that fit into a binding site of the protein, it transfers across the membrane at the same time changing its confirmation
-they are multipass transmembrane protein. by crisscrossing back and forth, the polypeptide chain forms a continuous protein-lined pathway that allows selected small hydrophilic molecules to cross the membrane without coming into contact with hydrophobic interior

Question 19

channel discriminate based

Answer 19

-mainly based on size and electric charge
-if channel open. ion or molecules that is small enough and carries the appropriate charge can slip thru

Question 20

function of transporter

Answer 20

to guide and propel the complex traffic of small molecules into and out of the cell, vtween cytosol, diff membrane enclosd organelles

Question 21

example of transporter

Answer 21

glucose transporter-plasma membrane of most anima cells-none energy source-fx passive import of glucose
ca2+ pump-plasma membrane of eukaryotic cell-atp hydrolysis-fx active export of ca2+
H+ pump-plasma membrane of plant cells, fungi and bacteria-atp hydrolysis-active export or h+

Question 22

transport of glucose (glucose transporter)

Answer 22

when sugar in plentiful outside the liver after a meal, glucose molecule bind to externally displayed binding sites, switches conformation , carries and release the glucose into the cytosol where glucose is low.
for uncharged molecule like glucose, the direction of passive movement determined solely by concentration gradient

Question 23

glucose transport is passive but highly___

Answer 23

specific . the glucose transporter only bind to D-glucose and not L-glucose

Question 24

for electrically charged molecule

Answer 24

additional force is needed

Question 25

what is membrane potential

Answer 25

most cell membranes have voltage across each side of the membrane, a difference in electrical potential in each side is called membrane potential

Question 26

how membrane potential help in transport of molecules

Answer 26

the difference in potential exerts a force on any molecule that carry charge

Question 27

the net force driving charged solute across the membrane consists of 2 forces

Answer 27

1. concentration gradient
2. the voltage across the membrane

(electrochemical gradient)

Question 28

voltage and concentration gradient work in the same direction creating

Answer 28

steep electrochemical gradient
eg na+ is positively charged and at a higher concentration outside cells than inside. Na+ tends to enter cells

Question 29

active transport moves solute ___ electrochemical gradient

Answer 29

against

Question 30

three main wagd in maintaining ionic composition

Answer 30

1. coupled transporter
2. atp driven pump
3. light driven pump

Question 31

types of active transport

Answer 31

1. primary active transport : require atp at the same time substrate is moved
2. secondary active transport: requires energy later

Question 32

atp driven pumps

Answer 32

1. P type pumps : structurally and functionally related to multipass transmembrane protein. named p type because they phosphorylate themselves during pumping cycle. maintaning NA+ K+ Ca2+ H+ across the cell membrane
2. ABC transporter: differ structurally from p type atpase and primarily pump small molecules across the membrane
3. V type pumps: transfers H+ into the organelle to acidify the interior of these organelles
4. F type pumps: structurally same with v type but work in reverse where they use H+ to synthesize atp

Question 33

what is coupled transporter

Answer 33

the downhill movement of molecules down its gradient provides energy to drive the uphill of the second solute