chapter 7- membrane structure and function

Question 1

what is an amphipathic molecule and example

Answer 1

a molecule that has both a hydrophilic and hydrophobic region
phospholipid

Question 2

why are membranes considered fluid

Answer 2

because the proteins and lipids move laterally through the membrane

Question 3

what moves and how does it move in a membrane

Answer 3

phospholipids and proteins move side to side fast
but they wont flip upside down because it would require going through the hydrophobic/hydrophilic portions (hard to cross)

Question 4

how does temperature affect the fluidity of the membrane

Answer 4

lower temperature = solid membrane
higher temperature = more fluid/liquid

Question 5

how is the temperature at which a membrane solidifies determined

Answer 5

based on the types of lipids in it

Question 6

why should a membrane be fluid

Answer 6

it needs to be to work properly

Question 7

which membrane it more fluid:
lots of unsaturated fatty acids or lots of saturated fatty acids

Answer 7

unsaturated as the kinks in the fatty acids prevent the packing of molecules

Question 8

what does cholesterol do regarding membranes at different temperatures

Answer 8

at warm temperatures it restrains the phospholipid movement (stops membrane from being too fluid)
at cool temperatures it prevents packing (keeps membrane fluid)

Question 9

what is the reason for the difference in membrane lipid composition (evolution)

Answer 9

adaptation to different environmental conditions
(ability to change lipid composition as temperature changes evolved in organisms that live where temperature varies)

Question 10

what are integral proteins

Answer 10

proteins that are imbedded into the membrane (through the hydrophobic middle)

Question 11

characteristics of integral proteins

Answer 11

they have hydrophobic sections made up of nonpolar amino acids/R groups and hydrophilic/polar sections that touch the inside and outside of the cell

Question 12

what are integral proteins also called

Answer 12

transmembrane proteins

Question 13

what are peripheral proteins

Answer 13

proteins that are bound to the surface of the membrane or to integral proteins

Question 14

what are the six major functions of membrane proteins

Answer 14

transport
enzymatic activity
signal transduction
cell-cell recognition
intercellular joining
attachment to cytoskeleton and extracellular matrix

Question 15

what are the two types of membrane carbohydrates

Answer 15

glycolipids (sugar + lipid)
glycoproteins (sugar + protein)

Question 16

what is the role of membrane carbs in cell recognition

Answer 16

cells recognize each other by binding to surface molecules, often carbs and recognizing foreign glyco-lipids/proteins

Question 17

what builds the membrane

Answer 17

the ER and golgi

Question 18

what does selective permeability mean

Answer 18

allows some substances to cross more easily than others

Question 19

what passes through the membrane and what does not

Answer 19

hydrophobic molecules pass through easily while hydrophilic molecules do not or pass through slowly

Question 20

what facilitates the movement of hydrophilic molecules across the membrane

Answer 20

transport

Question 21

what are the types of transport proteins

Answer 21

channel and carrier

Question 22

what are the types of channel proteins

Answer 22

aquaporins
ion channels

Question 23

how do ion channels work

Answer 23

they have a hydrophilic channel that allows polar molecules to pass (ions)

Question 24

what are gated channels

Answer 24

ion channels that open or close in response to a stimulus

Question 25

how do aquaporins work

Answer 25

channel that allows water to pass through

Question 26

are transport proteins specific

Answer 26

yes they are specific to the substance that they move (and sometimes related substances)

Question 27

what are carrier proteins

Answer 27

proteins that bind molecules and change shape to shuttle them across the membrane

Question 28

what is diffusion

Answer 28

tendency for molecules to spread out evenly into available space

Question 29

how does diffusion work

Answer 29

substances diffuse down their concentration gradient (high concentration to low) spontaneous

Question 30

what kind of transport is diffusion

Answer 30

passive

Question 31

what does passive transport mean

Answer 31

substance moves with no energy being used from the cell

Question 32

what is osmosis

Answer 32

diffusion of water across a selectively permeable membrane

Question 33

how does water diffuse in osmosis

Answer 33

moves from region of lower solute concentration to a region of higher solute concentration until they are equal

Question 34

what is the formula for solute concentration/osmolarity

Answer 34

molarity x number of ionized particles (van hoff i)

Question 35

what is tonicity

Answer 35

ability of a surrounding solution to make a cell gain or lose water

Question 36

what is an isotonic solution

Answer 36

solution's solute concentration is the same as the cell's concentration (no water movement)

Question 37

what is a hypertonic solution

Answer 37

solution's solute concentration is higher than the cell's (water moves out of the cell)

Question 38

what is a hypotonic solution

Answer 38

solution's solute concentration is lower than cell's (water moves in the cell)

Question 39

when an animal cell is placed into isotonic, hypertonic and hypotonic solutions what happens to it

Answer 39

isotonic: normal hypertonic: shrivel hypotonic: swell

Question 40

what is osmoregulation

Answer 40

control of solute concentrations and water balance

Question 41

what is different for plant cells regarding osmosis

Answer 41

they have cell walls which allow them to have better water balance

Question 42

when a plant cell is placed into isotonic, hypertonic and hypotonic solutions what happens to it

Answer 42

isotonic: flaccid (limp) hypertonic: plasmolysis (dead) hypotonic: turgid (firm)

Question 43

what happens during plasmolysis

Answer 43

plant cell loses water, plasma membrane pulls away from cell wall and causes plant to wilt

Question 44

what is facilitated diffusion

Answer 44

transport proteins aid the passive movement of molecules across the membrane

Question 45

what is active transport and characteristics

Answer 45

moving of substances against their concentration gradient, requires energy, performed by specific proteins embedded in membrane

Question 46

what is a type of active transport system

Answer 46

sodium-potassium pump

Question 47

what are the 6 steps of the sodium-potassium pump

Answer 47

1. sodium in the cell binds to the pump 2. binding of sodium stimulates the attachment of a phosphate group to the pump (using atp) 3. the attachment of P group leads to the pump changing shape and releasing the sodium to the outside 4. new shape attracts and binds potassium from the outside which triggers the release of the P group (inside) 5. losing P group restores the original shape 6. potassium is released

Question 48

what is phosphorylation

Answer 48

attachment of a phosphate group to a molecule of ion

Question 49

how much energy does one cycle of the sodium-potassium pump take

Answer 49

one ATP molecule

Question 50

how many sodiums are taken out and potassiums taken in

Answer 50

3 sodiums and 2 potassiums

Question 51

what is membrane potential

Answer 51

voltage difference across a membrane

Question 52

how is voltage created in a membrane

Answer 52

by the differences in the distribution of + and - charged ions across a membrane

Question 53

what is the electrochemical gradient

Answer 53

chemical force (ion's concentration gradient) and electrical force (effect of membrane potential on ion's movement)

Question 54

what does the electrochemical gradient do

Answer 54

diffuses ions across the membrane

Question 55

what is an electrogenic pump and example

Answer 55

a transport protein that generates voltage across a membrane sodium-potassium pump

Question 56

what is the main electrogenic pump for plants fungi and bacteria

Answer 56

proton pump (pumps out H+)

Question 57

what is another function of the electrogenic pump

Answer 57

store energy that can be used for cellular work

Question 58

what is cotransport

Answer 58

when the transport of one solute indirectly drives the transport of other solutes active transport driven by concentration gradient

Question 59

what is bulk transport

Answer 59

large molecules crossing membrane using vesicles

Question 60

does bulk transport require energy

Answer 60

yes

Question 61

what is exocytosis

Answer 61

transport vesicles migrating to the membrane then fusing with it and releasing their contents outside

Question 62

what is endocytosis

Answer 62

cell taking in macromolecules by forming vesicles from the membrane

Question 63

what are the three types of endocytosis

Answer 63

phagocytosis pinocytosis receptor-mediated endocytosis

Question 64

what is phagocytosis

Answer 64

when a cell engulfs a particle into a vacuole vacuole then fuses with lysosome to be digested

Question 65

what is pinocytosis

Answer 65

extracellular fluid in gulped into tiny vesicles

Question 66

what is receptor-mediated endocytosis*

Answer 66

molecule or ion binding to a receptor triggers the formation of a vesicle

Question 67

what do humans use receptor-mediated endocytosis for*

Answer 67

to take in cholesterol using LDL receptors

Question 68

how is cholesterol found in blood*

Answer 68

in particles called low-density lipoproteins (LDL)