cell membrane

Question 1

who is it that has an outer membrane but no internal membranes?

Answer 1

prokaryotes

Question 2

what is an endomembrane and who has them?

Answer 2

-internal membranes around different organelles
-eukaryotes have them

Question 3

why are cell membranes important?

Answer 3

-physical separation between the inside of the cell (biochemical reactions) and the outside of the cell
-selective permeability
-further compartmentalization in eukaryotes

Question 4

what are the molecular constituents of the cell membrane?

Answer 4

1) phospholipid bilayer
2) proteins:
a) transmembrane protein
b) interior protein network
3) surface markers (mainly carbs)

Question 5

true or false: the phospholipid bilayer excludes water-soluble molecules from non-polar interior of bilayer and cell

Answer 5

true

Question 6

what is an integral membrane protein?

Answer 6

-they are inserted into the phospholipid bilayer
-if it crosses the bilayer completely it is called a transmembrane protein

Question 7

what are peripheral membrane proteins?

Answer 7

they are attached to the surface of the phospholipid bilayer or to an integral protein

Question 8

what is composed of hydrophobic amino acids which anchor the protein to the membrane, since the fatty acids of the phospholipids are also hydrophobic ?

Answer 8

protein network (transmembrane domain)

Question 9

what can single transmembrane domain be used for (integral membrane protein)?

Answer 9

to anchor the cytoskeleton on the cell

Question 10

what can multiple transmembrane domains be used for (integral membrane protein)?

Answer 10

cell-surface receptors for external molecules such as a hormone

Question 11

what are the 6 types of proteins?

Answer 11

-transporter
-enzyme
-cell-surface receptor
-cell-surface marker
-cell-to-cell adhesion
-attachment to the cytoskeleton

Question 12

which type of proteins form channels or carries to control movement of material in and out of cell?

Answer 12

transporter proteins

Question 13

what type of transporter proteins have a hydrophilic interior that provides an aqueous channel through which polar molecules can pass when the channel is open?

Answer 13

channel proteins

Question 14

which type of transporter proteins bind specifically to the molecule they assist to carry through the membrane?

Answer 14

carrier proteins

Question 15

which type of proteins are involved in the catalytic reactions of chemicals, lowering the activation energy?

Answer 15

enzymes

Question 16

which type of proteins detect chemical messages (insulin)?

Answer 16

cell surface receptors

Question 17

which type of proteins have carbohydrates (usually oligosaccharides) on the outer surface and permit to ID a cell type and self?

Answer 17

cell surface markers

Question 18

which type of proteins bind cells together?

Answer 18

cell-to-cell adhesion

Question 19

which type of proteins anchor cells to the cytoskeleton and extracellular matrix?

Answer 19

attachment

Question 20

what are spectrins?

Answer 20

-determine shape of cell
-support scaffold beneath membrane

Question 21

what are clathrins?

Answer 21

-anchor certains proteins to specific sites
-proteins line coated pits and facilitate binding to specific molecules
(looks like football)

Question 22

which type of membrane transport
-requires no energy
-molecules move in response to a concentration gradient?

Answer 22

passive transport

Question 23

which type of transport
-requires energy
-can move substances from low to high concentration?

Answer 23

active transport

Question 24

what are the 3 types of passive transport?

Answer 24

-simple diffusion
-facilitated diffusion
-osmosis

Question 25

what is it: the molecules will always disperse from a high concentration to a low concentration until all the solution reaches the same concentration?

Answer 25

simple diffusion

Question 26

describe the permeability of different types of molecules in simple diffusion

Answer 26

-non-polar molecules: will move until the concentration is equal on both sides -very small polar molecules: can pass through the membrane (O2, CO2) -small polar molecules: limited permeability (H2O) -larger polar molecules and ions: very limited permeability (won't pass through)

Question 27

what is it: the molecules that cannot cross the membrane easily may move through proteins

Answer 27

facilitated diffusion

Question 28

what are the 3 characteristics of facilitated diffusion?

Answer 28

1) specific transport: only will transport certains molecules or ions 2) passive transport: moves by diffusion from region of higher to lower concentration (no energy required) 3) saturation: the transport protein can get saturated

Question 29

what are the two types of facilitated diffusion?

Answer 29

1) channel proteins 2) carrier proteins

Question 30

what is it: open channels permit water to cross the plasma membrane according to concentration (osmosis)

Answer 30

aquaporins

Question 31

what is it: -allows the passage of ions through non-polar interior of plasma membrane -have ion selectivity -some are gated channels (open/close in response to stimulus)

Answer 31

ion channels

Question 32

true or false: at high enough concentrations, all carrier proteins will be occupied, therefore the rate of transport will be constant, meaning the carrier exhibits saturation

Answer 32

true

Question 33

what is osmosis?

Answer 33

-net diffusion of water across a selective membrane towards a a higher solute concentration

Question 34

what are the 3 cases of osmolarity of a solution?

Answer 34

-hypotonic: solution has a lower solute concentration than the cell (cell can burst) -isotonic: solution has same concentration as cell -hypertonic: solution has a higher solution concentration than cell (cell can shrivel)

Question 35

what is osmoregulation?

Answer 35

how some organisms can maintain osmotic balance

Question 36

what is turgor pressure?

Answer 36

plants use it to push the cell membrane against the cell wall and keep the cell rigid, thus blocking entry of too much water and giving the plant their rigidity

Question 37

what is extrusion?

Answer 37

excess water is collected and ejected from cell through contractile vacuoles in some protists

Question 38

what is isosmotic regulation?

Answer 38

some organisms living in the ocean adjust their internal concentration of solutes to match that of surrounding seawater. since they are isosmotic with environment, no net flow occurs in/out of cells

Question 39

describe active transport

Answer 39

-moves substance from a region of lower to higher concentration, against a concentration gradient -requires ATP -requires carrier proteins

Question 40

which type of active transport protein is it: transports one substance in one direction

Answer 40

uniport

Question 41

what type of active transport protein is it: transports 2 different substances in the same direction

Answer 41

symport

Question 42

what type of active transport protein is it: transports 2 different substances in opposite directions

Answer 42

antiport

Question 43

what is primary active transport?

Answer 43

ATP used to transport a chemical outside the cell against its concentration

Question 44

what is secondary active transport?

Answer 44

passive movement of one solute with its concentration gradient induces the movement of another solute against its concentration gradient

Question 45

What creates electric potential in the Na+/K+ pump?

Answer 45

-present in the membrane of neuron more Na+ outside compared to the amount of K+ inside -electric potential of -70 mV

Question 46

what is endocytosis?

Answer 46

-movement of bulk substances into the cell -occurs when the plasma membrane envelops food particles and/or liquids to bring them into the cell -requires energy to work

Question 47

what is exocytosis?

Answer 47

-movements of bulk materials out of the cell -used in plants to export cell wall material -used in animals to secrete hormones, neurotransmitters, digestive enzymes, expel waste

Question 48

what are the 3 types of endocytosis?

Answer 48

phagocytosis: material the cell takes in is particulate pinocytosis: material the cell takes in is dissolved substances or fluids receptor-mediated endocytosis: molecules first bind to specific receptors in the plasma membrane, they have a conformation that fits into the receptor, acts as molecular mousetrap: closing over to form an internal vesicle