Cell membranes

Question 1

phospholipids

Answer 1

Structure: (amphipathic) hydrophobic tail and hydrophilic head

Function: creates a stable boundary between two aqueous compartments

Question 2

cholesterol

Answer 2

Acts as a fluidity buffer
At high T, cholesterol restrains phospholipids movement (less fluid).
At low T, cholesterol stops phospholipids from packing too closely.

Question 3

Protein

Answer 3

(amphipathic) are peripheral (on outside cell membrane) or integral (between cell membrane

Function: transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment of ECM and cytoskeleton

Question 4

Glycoproteins

Answer 4

Structure: membrane carbohydrate covalently bonded to a protein

Function: (cell-cell recognition) cells recognize other cells by binding to the carbohydrates on the outside of the cell membrane

Question 5

Glycolipids

Answer 5

Structure: membrane carbohydrate covalently bonded to a lipid

Function: (cell-cell recognition) Cells recognize other cells by binding to the carbohydrates on the outside of the cell membrane

Question 6

Hydrophobic molecules

Answer 6

O2, CO2, N2, steroid hormones
Have a high permeability and go through easily

Question 7

Small uncharged polar molecules

Answer 7

H2O, urea, glycerol, NH3
Have medium permeability and pass slowly

Question 8

Large uncharged polar molecules

Answer 8

glucose, sucrose
Have medium permeability and pass very slowly

Question 9

Ions

Answer 9

H+, Na+, HCO3-, K+, CA2+, CL-, Mg2+
Have low permeability and is not likely to pass

Question 10

(passive) diffusion

Answer 10

Rapid random movement of particle from concentrated to less concentrated

Question 11

(passive) osmosis

Answer 11

diffusion of water to balance out the concentration gradient.

Question 12

Isotonic

Answer 12

surroundings (identical environment) → no osmosis, as water diffuses at the same rate in both directions

Question 13

hypertonic

Answer 13

surroundings (higher concentrations of solutes) → cell loses water and shrivels up

Question 14

hypotonic

Answer 14

surroundings (lower concentration of solutes) → water will enter the cell and it will swell and burst

Question 15

(passive) channel proteins

Answer 15

transports water (aquaporin) or transports ions (ion channels)

Question 16

(passive) gated channels

Answer 16

Type of channel protein that can open and close in response to a stimulus

Question 17

(passive) carrier proteins

Answer 17

Carrier proteins subtly change their shape to translocate the solute-binding site across the membrane.

Question 18

(active) carrier proteins

Answer 18

move molecules against their concentration gradient, using ATP hydrolysis as a source of energy

Question 19

(active) ion pump

Answer 19

ATP hydrolysis supplies the energy needed to move ions against an electrochemical gradient. This helps maintain the electrochemical gradient, which is important for cellular work such as ATP synthesis

Question 20

electrogenic pump

Answer 20

transport protein that generates voltage across a membrane

Question 21

(active) cotransporters

Answer 21

can couple the passive diffusion of a solute with the active transport of a different solute.

Question 22

(bulk transport) exocytosis

Answer 22

cell takes out molecule through the fusion of vesicles made from the Golgi apparatus and the cell membrane

Question 23

(bulk transport) endocytosis

Answer 23

takes in molecules from the environment by the cell membrane making vesicles.
phagocytosis: cellular eating
pinocytosis: cellular drinking

Question 24

Sodium-potassium pump (step)

Answer 24

1) the sodium-potassium pump binds 3 sodium ions and ATP molecule

2) energy is released from the splitting of ATP to change shape of channel. Sodium ions go through the channel.

3) sodium ions are released and new shape allows potassium to go in

4) release of the phosphate reverts to initial shape, releasing the potassium ion in the cell

Question 25

Proton pump

Answer 25

is a eletrogenic pump that store energy by generating voltage across membrane. most are powered by ATP

Question 26

Membrane potential

Answer 26

the difference in voltage between two sides of a plasma membrane. Most cells have a negative transmembrane potential (the inside of the cell is more negative than the outside).

Question 27

equilibrium potential

Answer 27

the voltage required to maintain an equilibrium concentration gradient, where diffusion forces and electrostatic forces are equal

Question 28

action potential

Answer 28

A brief reversal of electric polarity across a cell membrane. In neurons, this is used to transfer electric signals through the axon and onto neighbouring neurons

Question 29

GLUT transporter

Answer 29

glucose binds to the receptor of a glucose transporter protein. the protein changes shape in order to release glucose in the cytoplasm. This process can happen in the opposite way too

Question 30

SGLT transporter

Answer 30

the protein only changes its shape when it bounded with sodium ion and glucose. Only then it will release it in the cytoplasm