1.3 (cell membrane + transport)

cell membranes and transport the higher the solute potential concentrations… (46) is last flashcard put into anki

cell membrane main component

phospholipids

whys it called a bilayer

has two layers

orientation of each phospholipid end + why

phosphate heads pointing outwards (towards water in cytoplasm) + fatty tails inwards (away from water)

when submerged in water phospholipids form

micelles

model name for phosphlipid bilayer + why

fluid- mosaic model

fluid = movement of molecules within a layer

mosaic = proteins studded through the phospholipid bilayer

cholestrol function

gives stability + regulates fluidity of membrane

name 1

phospholipid bilayer

name 2

intrinsic protein

name 3

carrier protein

name 4

cholestrol

name 5

channel protein

name 6

extrinsic proteins

name 7

glycolipid

name 8

glycoprotein

cell membrane size

5-10nm

simple diffusion definition

passive net movement of molecules/ ions down a concentration gradient from a region of higher concentration to lower concentration

what type of molecules move through simple diffusion

very small non-polar molecules

facilitated diffusion definition

passive + down a concentration gradient- across a membrane by channel/ carrier proteins

what type of molecules/ ions move through facilitated diffusion

larger molecules + water soluble ions

factors affecting rate of facilitated diffusion

-temp

-difference in concentration of two sides

-frequency of carrier proteins available on plasma membrane

-type of carrier proteins (some are specific)

active transport definition

movement of molecules/ ions against a concentration gradient from a region of lower concentration to higher concentration using energy in the form of ATP and protein carrier molecules

how active transport in a carrier protein works

-molecule/ ion to be transported binds to carrier protein

-inside the cell ATP binds to carrier protein causing it to split into ADP + phosphate causing carrier protein to change shape + open to opposite side of membrane

-molecule/ion released on other side of membrane

-phosphate molecule released from protein + recombines with ADP to form ATP

-causes protein to revert to original shape, ready for process to be repeated

against a concentration gradient means

from lower to higher concentration

down a concentration gradient means

from higher to lower concentration

cells performing lots of active transport need lots of…

mitochondria

is cholesterol is plant cells or animal cells or both

animal cells

co-transport definition

a type of facilitated diffusion by which two substances are simultaneously transported across a membrane by a carrier protein

what molecules can pass through the phospholipid bilayer

-small molecules

-lipid soluble substances

-water soluble substances

things that affects rate of diffusion

-difference between concentration gradients

-thickness of exchange surface

-surface area of the membrane

-size of diffusing molecule

-temp

do fat soluble or water soluble molecules diffuse faster

fat soluble molecules

do polar or non-polar molecules diffuse faster

non-polar molecules

what are channel proteins

-molecules with polar group lined pores, water soluble ions can pass through

-channels open + close when needed

what are carrier proteins

-allow diffusion of larger, polar molecules

-molecule attaches to it’s binding site

-carrier protein changes shape + releases molecules on other side then returns to original shape

example of co-transport

sodium potassium pump

how sodium potassium pump works

Sodium (3)
Out
Potassium (2)
In

osmosis diffusion

the net passive diffusion of water molecules across a selectively permeable membrane from a region of higher water potential to a region of lower water potential

water potential (Ψ) definition

a measure of the free energy of water molecules and is the tendency for water to move

does water potential have a negative or positive scale

negative scale

pure water has a water potential of…

0

water potential is measured in

kilopascals (kpa)

more solute added to water does what to the water potential

lowers water potential (more negative)

water potential equation

Ψ = Ψs + Ψp

solute potential (Ψs)

a measure of the osmotic strength of a solution- reduction in water potential due to the presence of solute molecules

pressure potential (Ψp) definiton

the hydrostatic pressure exerted by the cell contents on the cell wall- it is equal + opposite to the pressure exerted by the cell wall on the cell contents

pressure potential increases…

the tendcency of water to move out

the higher the solute potential concentrations…

the less likely the water is to move out

the polarity of protein molecules affects their…

position in the membrane

how is a glycocalyx formed

extracellular surfaces of the proteins are glycosylated

plasmolysis definition

the retraction of the cytoplasm and the cell membrane from the cell wall as a cell loses water by osmosis

endocytosis definition

the active process of the cell membrane engulfing material, bringing it into the cell in a vesicle

endocytosis definition

the active process of the cell membrane engulfing material, bringing into the cell in a vesicle

exocytosis definition

the active process of a vesicle fusing with the cell membrane, releasing the molecules it contains

phagocytosis definition

the active process of the cell membran engulfing large particles, bringing them into the cell in a vesicle

pinocytosis defintion

the active process of the cell membrane egulfing droplets of fliud, bringing them into the cell in a vesicle

exocytosis and endocytosis provides

a mechanism for bulk transport across a cell membrane

exocytosis and endocytosis change

the surface area of cells as they occur

transport across cell membranes is affected by

• surface area

• concentration gradient

• temp

• molecule size

• lipid solubility

  • membrane thickness

active transport provides

a mechanism to increase the rate of transport across the membrane for certain molecules eg polar molecules

isotonic definition

cell has same water potential as surrounding solution

movement of water in isotonic solution

no net movement of water

hypertonic definition

water potential of the external solution is more negative (lower) than the solution inside the cell

movement of water in a hypertonic solution

water flows out of cell

how to remember what hypertonic is

hyper- lower- further away from zero (external solution)

hypotonic definition

water potential of external solution is less negative (higher) than the solution inside the cell

movement of water in a hypotonic solution

hypo- zero- closer to zero (external solution)

what happens to a plant cell in a hypotonic solution

turgid- cytoplasm pushed against cell wall

what happens to a plant cell in a isotonic solution

incipient plasymolsis- cystoplasm begining to pull away from cell wall

what happens to a plant cell in hypertonic solution

plasmolysed- cytoplasm completely pulled away from cell wall

what happens to animal cell in hypotonic solution

haemolysis- cell bursts

what happens to animal cell in isotonic solution

nothing- stays same

what happens to an animal cell in hypertonic solution

becomes crenated- cell shrinks + loses shape

turgid definition

a plant cell that holds as much water as possible- further entry of water is prevented as the cell wall cannot expand further

plasmolysis definition

the retraction of the cytoplasm and the cell membrane from the cell wall as a cell loses water by osmosis

incipient plasmolysis definition

cell membrane and cytoplasm are partially detatched from the cell wall due to insufficient water to make cell turgid

how does cyanide stop active transport

by blocking cellular respiration

two factors affecting permeability of the plasma membrane

-temp

-organic solvents

all membrane in cells are

selectively permeable

how does a glycoprotein act as a receptor

has a specific shape thats complementary to the communicaitng molecule

three roles of glycoproteins in membranes

-act as an antigen for cell recognition

-act as a receptor triggering a series of chemical reactions within the cell

-forms hydrogen bonds with surrounding water molecules to stabilize membrane structure

why can’t water molecules easily move through the phospholipid bilayer

water is polar and fatty acids are hydrophobic