Bio Ch. 8 (-3) & Ch. 9

What factors influence membrane fluidity?

• fluid-mosaic characteristics (?)

• type of fatty acids in the phospholipids

• cholesterol

• temperature

How do the fluid-mosaic characteristics affect fluidity

the “mosaic” arrangement means that it can adapt more easily and self seal if disrupted. It makes it more flexible as a whole

How does the type of fatty acid in phospholipids affect fluidity of the membrane

saturated = straight, make a dense & rigid membrane

unsaturated = bent and don’t pack as tightly (makes it more flexible)

how does cholesterol affect membrane fluidity

cholesterol lipids lessen the effects of temperature on the membrane by acting as a buffer

extends the range of temperature it can function properly in

how does temperature influence membrane fluidity

higher temperatures increase fluidity - moves more freely, which creates a “more fluid state” that lipids and proteins can move laterally within more easily

lower temperatures decrease - less movement, more rigid, less fluid, more tightly packed together

The amphipathic nature of plasma membranes makes the membrane ________ _________

selectively permeable

How does the amphipathic nature of plasma membranes make it selectively permeable & what does that mean

the membranes have both hydrophobic and hydrophilic regions, which allows for some things to get through and others to not

what CAN get through the hydrophobic areas of the membrane (and examples)

small, lipid-soluble substances

hydrophobic gases like O2 and CO2

fat soluble vitamins (A, D, E, K)

what CANT get through the membrane (and examples)

hydrophilic substances

polar, charged, ions

large polar molecules (monosaccharides & amino acids)

When is passive transport used?

substance moves high —> low concentration

does passive transport require energy

nope!

when is active transport used

substance moves from low —> high concentration

does active transport require energy

yes

Is diffusion active or passive

passive

what is a concentration gradient

a range of concentrations across a space/the difference in the concentration of a substance between areas

substances typically move from areas of ______ concentration to areas of _____ concentration

high —> low

what is dynamic equilibrium

state where systems maintain stability despite continuous internal changes

• just a more specific version of homeostasis

Factors that affect diffusion:

“steepness” of the concentration gradient

mass of the molecules diffusing

temperature

solvent density

how does the “steepness” of the concentration gradient affect diffusion

the greater the difference in concentration, the faster diffusion happens

the closer the distribution of the material gets to the equilibrium, the slower it happens

how does the mass of the molecules diffusing affect diffusion

heavier molecules move slower and therefore diffuse more slowly

how does temperature affect diffusion

higher temps = increased energy and movement of molecules, so faster diffusion

how does solvent density affect diffusion

as density ↑ rate of diffusion ↓

molecules slow down because they have a harder time getting through a denser area

if the area is less dense diffusion increases

What is facilitated diffusion

diffusion with the help of membrane proteins

What are the membrane proteins for facilitated diffusion

channel and carrier proteins

why is facilitated diffusion sometimes required

for polar or charged molecules that can’t get through the phospholipid bilayer directly

how do the proteins help these molecules get through the bilayer

they shield them from the repulsive force of the membrane

Which protein do ions use for facilitated diffusion

channel proteins (because they are small and charged)

What protein do larger polar molecules like glucose and amino acids diffuse through (facilitated diffusion)

carrier proteins

What part of channel proteins is hydrophobic and which part is hydrophilic

hydrophobic = the exterior/part that interacts with the phospholipid bilayer

hydrophilic = interior “channel” is hydrophilic

what is the most common type of channel protein

ion channels

Can an ion channel work for multiple ion types

no, each ion channel is specific to one type of ion

What is the difference between an “open” ion channel protein and a “gated” one

“open” = always open

“gated” = can be opened or closed

How do “ligand-gated” channels work

the attachment of a particular molecule to the channel protein may cause it to open

how do “voltage-gated” channels work

they require a change in voltage across the membrane to open them

What cells have voltage gated channels in their membranes

cells involved in the transmission of electrical impulses

nerve & muscle cells

what are aquaporins

channel proteins that allow water to pass through the membrane at a very high rate

What molecules use carrier proteins (and examples)

molecules that are too large to pass through channels

amino acids & glucose

what happens when a substance binds to its carrier protein?

A shape change is triggered that moves the bound molecule across the membrane

What does it mean when all carrier proteins are bound to their ligands and are saturated?

the rate of transport is at its maximum

will the rate of transport change if you increase the concentration gradient when all carrier proteins are bound to their ligands and are saturated?

nope! everything’s already at its max

what do glucose transport proteins (GLUTs) do

transport glucose and other sugars into the cell

what kind of proteins are glucose transport proteins (GLUTs)?

carrier proteins

are carrier proteins or channel proteins faster means of transportation

channel proteins

what is osmosis

diffusion of water across a semipermeable membrane

what is the relationship between amount of water and solute concentration

“inversely proportional”

the higher the water concentration, the lower the solute concentration (and vice versa)

which direction does water move in terms of concentration

water moves from a high concentration of water to a low concentration of water

• where there’s less water, that’s where it goes

What is tonicity

the ability of a solution to cause a cell to gain or lose water depending on the relative concentrations of solute inside and outside of the cell

• a comparison between the solute concentration inside the cell and outside of it

what is osmolarity and what does it influence

the total concentration of dissolved solute particles per liter of solution/the total solute concentration of the solution

• influences water movement across membranes and cell volume

what does it mean if a solution has a low osmolarity

there is more water relative to the solute

(like hypotonic but all within the cell, just compares internal substances)

what does it mean if a solution has a high osmolarity

there is less water relative to the solute

(like hypertonic but within the cell itself, just compares internal substances)

What 3 terms describe the comparison between the osmolarity of a cell to the osmolarity of the extracellular fluid?

hypotonic

hypertonic

isotonic

hypotonic definition and which direction does water move

solution outside of the cell has a lower solute concentration/more water

water moves down the concentration gradient and go into the cell to dilute it

hypertonic definition and which direction does water move

solution outside of the cell has a greater solute concentration/less water

water moves out of the cell

isotonic definition and which direction does water move

iso = same —> they have the same osmolarity (concentration) both inside and outside of the cell

How does the cell wall in plants, fungi, bacteria, and some protists help the cell from lysing (bursting)

the inflow of water produces turgor pressure that stiffens the cell walls

plasmolysis

the a plant is not watered the extracellular fluid will become hypertonic and the plant cell will shrink within its cell wall

what is the turgor pressure equivalent in protists that don’t have cell walls

contractile vacuoles that pumps out excess water

Does active transport require energy

yes

when is active transport used

if a substance has to move against the concentration gradient to get into the cell

what is active transport

the movement of solutes (not water) across a membrane against their concentration gradient

which direction do solutes move in active transport in terms of concentration

solutes move from a lower concentration to a higher concentration area

VERY basic explanation of active transport

pushing a rock uphill takes more energy and effort because you’re fighting gravity

what type of energy do cells typically use for active transport

ATP

difference between hypo/hpertonic movement and active transport movement

hypo/hypertonic movement moves water from areas with lots of water to areas with less water (adding water to juice to make it less strong)

active transport moves solute from areas of less solute to areas with more solute (pushing more people into a crowded area)

What is an electrical gradient

a difference of charge across the plasma membrane

what causes the electrochemical gradient

ions move in and out of cells but cells have proteins that don’t move and are mostly negatively charged

is the inside of living cells more electrically negative or positive compared to the extracellular fluid

electrically negative

Do cells have a higher or lower concentration of sodium ions than the extracellular fluid

lower concentration of Na+

what does it mean that the inside of cells has a greater electronegativity and a lower concentration of Na+

both the concentration gradient and electrical gradient tend to drive Na+ into the cell (????)

Do cells have a higher or lower concentration of potassium ions than the extracellular fluid

higher

what happens since there is a higher K+ concentration inside cells

the concentration gradient pushes K+ out of the cell while the electrical gradient pushes it into the cell

(wut)

What is the electrochemical gradient

the combined gradient of concentration and electrical charge that affects an ion

what protein does active transport use to work against the electrochemical gradient

pumps

what is the official term for the specific carrier proteins or pumps that facilitate active transport

transporters

what are the 3 types of transporters

uniporter

symporter

antiporter

what does a uniporter do in active transport

carries one specific ion or molecule

what does a symporter do in active transport

carries 2 different ions or molecules in the same direction

(sym means “together” or “with”)

what does an antiporter do in active transport

carries 2 different ions or molecules in different directions

(anti means “opposite”)

what kind of molecules can all 3 transporters carry

polar molecules like glucose against their gradient

picture of proteins for active transport

difference between primary active transport and secondary active transport (basic)

primary is directly dependent on ATP

secondary does not directly require ATP

why does secondary active transport not directly require ATP and what does this mean in terms of order of events

it uses electrochemical gradients established by primary active transport for fuel

means primary must occur first

why is the sodium-potassium pump important for cells

maintains the electrochemical gradient and the correct concentrations of Na+ and K+ on both sides of the cell membranes

is the sodium-potassium pump for animal cells or plant cells

animal

what active transport protein is the sodium-potassium pump

antiporter

What does the sodium-potassium pump do as an antiporter

moves 3 Na+ out of the cell and 2 K+ into the cell each cycle

Steps of the sodium-potassium pump (5 really long steps)

1.) 3 Na+ bind to the inside of the pump and ATP binds to the outside of the pump

2.) ATP attaches a phosphate group to the pump

3.) the pump changes shape and opens towards the outside of the cell and 3 Na+ are released from the cell

4.) 2 K+ attach to the inside of the pump, which causes the phosphate group to detach

5.) the pump changes back to its original shape and the 2 K+ are released into cytoplasm

Picture of the sodium-potassium pump

what is phosphorylation in the sodium-potassium pump example

in each cycle a phosphate group is transferred from ATP to the pump protein

what occurs as a result of phosphorylation in the sodium-potassium pump cycle

the pump protein changes shape, moving ions across the membrane

what is the definition of an electrogenic pump

a pump that creates an electrical imbalance across the membrane

What makes the sodium-potassium pump an electrogenic pump

because 3 Na+ move out as 2 K+ go in, the interior is slightly more negative than the exterior

what is the purpose of secondary active transport

to use ion gradients to bring substances like glucose and amino acids into the cell

Don’t know how to turn this into a question but it seems kinda important

“in one example of secondary active transport, cotransporter proteins bind to sodium ions and glucose on the outside of the cell. Sodium ions moving down their electrochemical gradient provide the energy to change the shape of the cotransporter protein, releasing both sodium ions and glucose into the cell”

what are vesicles used for and what is this process called

bringing large materials that can’t get through the membrane into and out of the cell

bulk transport

what are the types of bulk transport

endocytosis (not bolded = types of endocytosis)

phagocytosis

pinocytosis

receptor-mediated endocytosis

exocytosis

what is endocytosis and how does it work

moves particles such as large molecules, parts of cells, and even whole cells into a cell

the plasma membrane dents inward and creates a pocket that’s pinched off to become an intracellular vesicle

what is phagocytosis and how does it work

“cell eating” - large particles like other cells or relatively large particles are taken in by the cell

white blood cells eat invaders

surrounds and engulfs the microorganism

what is pinocytosis and how does it work

“cell drinking” - cells take in molecules that it needs from the extracellular fluid (including water)

results in a much smaller vesicle than phagocytosis and the vesicle does not need to merge with a lysosome after entering the cell

what is receptor-mediated endocytosis and how does it work

targeted variation of endocytosis that uses specific receptor proteins in the plasma membrane that bind to specific substrates