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Bio test 2 > Lecture 8b > Flashcards

Lecture 8b Flashcards

1
Q
A

d)

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2
Q

what determines a substances ability to pass through the plasma membrane?

A

their size and polarity

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3
Q

how can ions, polar and/or large molecules pass through the plasma membrane?

A

can only cross through membrane proteins

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4
Q

what transports large quantities of substances in the cell?

A

substances that are large can be imported or removed from the cell through bulk transport via vesicles

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5
Q

what are the two ways molecules leave and enter the cell?

A

1) passive transport (no energy required)
2) active transport(energy required)

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6
Q

what are the three types of passive transport?

A

1)diffusion through membrane
2)osmosis - specific to water
3)facilitated diffusion - required integral membrane proteins

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7
Q

what are two types of active transport?

A

1) transporter pumps
2) bulk transport ( endocytosis and exocytosis )

transporter pumps = goes from low energy to high energy as it goes against the concentration gradient
bulk transport = -> endocytosis = vesicles sucking in materials into the membrane
exocytosis = vesicles that pack and secrete these materials

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8
Q

passive transport

what happens in diffusion?

A

substances move from an area of high concentration to an area of low concentration untill equilibrium is reached

molecules moving across the membrane

does not need energy

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9
Q

what is net movement?

A

movement in one direction minus the movement in the opposite direction - movement in the direction of concentration gradient

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10
Q

what is the net movement at equilibrium?

A

net movement is zero but exchange still occurs on a molecule-for-molecule basis

the molecules are always moving however same amount of molecules in both directions = equilibirum

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11
Q

passive transport

what is osmosis?

A

the diffusion of water across a selectively permeable membrane
- water diffuses across a membrane from low solute concentration to high solute concentration

driven by impermeable solutes only
water can pass through the gradient

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12
Q

what is the net movement of water?

A

the net movement of free water is from low solute concentration to high solute concentration

free water= not interacting with solute thus free to diffuse

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13
Q

what is osmotic pressure?

A

hydrostatic pressure needed to stop the net flow of water across a membrane due to osmosis.

must apply pressure to prevent water flow

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14
Q

high solute concentration leads to high or low osmotic pressure?

A

high solute concentration= high osmotic pressure
low solute concentration = low osmotic pressure

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15
Q

what is tonicity?

A

the ability of a solution to cause a cell to gain or lose water; the measure of the osmotic pressure gradient.

depends on the total concentration of impermeable solutes

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16
Q

what is an isotonic solution?

A

where the solute concentration in the solution is the same as inside the cell
- no net water movement across the plasma membrane

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17
Q

what is hypertonic solution?

A

where the solute concentraion in the solutions is larger than that inside the cell
- cell loses water

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18
Q

what is hypotonic solution?

A

where the solution concentration in the solution is smaller than that inside the cell
- cell gains water

influx of water causing the cell to burst

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19
Q

Tonicity in plant cells

what type of solution surrounds a plant cell that is getting fed water?

A

hypotonic

the water vacuole is full and provides turgor pressure on the cell wall- the cell is turgid (firm)
- turger pressure = where the cells have reached their absorption point and wont take in anymore water thus they will not burst

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20
Q

tonicity in plant cells

what solution surrounds a healthy plant cell?

A

isotonic

net movement is equal

the water vacuole does not exert enough pressure on cell wall to give proper support - the cell becomes flaccid (limp) and the plant may wilt

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21
Q

tonicity in plant cells

what solution surrounds a dying plant cell?

A

hypertonic

water seeks to exit the cell therefore the cell wall cannot help, the membrane pulls away from the wall ( plasmolysis )

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22
Q

what is osmolarity?

A

the total concentration of all solutes

measured in osmoles

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23
Q

what is iso-osmotic?

A

number of particles/solutes is the same on both sides of the membrane

24
Q

what is hyper-osmotic?

A

number of particles/solutes is greater on one side of the membrane than the other

25
Q

what is hypo-osmotic?

A

number of particles/solutes is lower on one side of the membrane than the other

26
Q

what is osmoregulation?

A

controls the water balance

example: paramecium (purple )- hypertonic to the pond water it lives in therefore its cell has a contractile vacuole that acts as a pump to force water out of the cell

27
Q

is 0.3M ethyl alchohol hypotonic or isotonic to mammalian cells?

A

hypotonic and causes an influx water which is dangerous for the animal cell

28
Q

where do you find osmoregulation in plant cells?

A

the cell walls

they help maintain water balance

29
Q

osmosis problem

Solution A contains 0.15mM of NaCl
solution B contains 0.3mM of sucrose
What is the tonicity of the solution A with respect to solution B?

A
30
Q

osmosis problem

A
31
Q

what is facilitated diffusion?

A

where transport proteins speed up the passive movement of molecules across the plasma membrane.

no energy input required

net movement down its concentration gradient ( high concentration to a low concentration )

32
Q

what are channel proteins?

A

channel proteins found in facilitated diffusion that provide hydrophilic corridors allowing specific molecules/ions to cross the membrane.

33
Q

what do aquaporins do in channel proteins?

A

aquaporins are for facilitated diffusion of water

34
Q

what is the role of ion channels in channel proteins?

A

they open or close in response to a stimulus (gated channels)

35
Q

why are channel proteins gated?

A

they are usually gated to regulate the cell over what comes in and what comes out

i.g. aquaporins

36
Q

when do the carrier proteins undergo a change in shape?

A

they undergo a subtle change in shape when they bind to a solute that translocates the solute-binding site across the membrane

GLUT4 transports glucose inside the cell
LacY transports lactose inside the cell

37
Q

what is the difference between carrier proteins and channel proteins based on speed?

A

carrier proteins are much slower because they must change shape

the rate of carrier proteins is dependent on the number of carriers in the membrane

38
Q

what are the three terms carrier proteins are classified as?

A

1) uniporters=a single solute moves in one direction,recognizes only one substrate
2) symporters=two solutes move in the same direction, recognizes two different substrates in the same direction
3) antiporters=two solutes moving in opposite directions, recognizes two different substrates in opposite directions

39
Q

what is the main function that occurs in active transport?

A

moves substances against their concentration gradient therefore requires energy ( ATP )

40
Q

what are the two types of active transport?

A

1) Primary active transport = carrier mediated and energy is provided by the ATP
2) Secondary active transport = co-transport, ATP required, ion gradient as a mean of transport (takes advantage of the gradient and hops on another molecule using downward movement)

41
Q

What are the main differences between passive transport and active transport?

A

passive:
- net movement from high to low concentration untill equilibrium is reached
- no energy is required as its going with the gradient
- passive transport through a channel or transporter that is by facilitated diffiusion
active:
- requires ATP as the net movement is going against the concentration gradient
- large or small transported molecules
- requires a carrier/transporter protein
- allows the cell to maintain different internal and external environments

42
Q

what is primary active transport?

A
  • requires energy (ATP)
  • donating a phosphate group by ATP to a carrier protein leads to a conformational change of shape
  • allows the passage of substances across the membrane
  • transports substances from low to high concentrations (against the concentration gradient)
43
Q

what type of transport is the sodium-potassium pump?

A

primary active transport

44
Q

Describe the process of Na/K ATPase

A

1) three cytoplasmic Na+ binds to the sodium potassium pump. (high affinity when the protein has this shape) -
2) the binding of Na+ stimulates phosphorylation by ATP
3) phosphorylation leads to a change in protein shape, reducing its affinity for Na+ (released outside)
4) This new shape has a high affinity for two K+, therefore the two K+ bind on the extracellular side which triggers the release of the phosphate group.
5) loss of the phosphate group restores the protein’s original shape ( has a lower affinity for K+)
6) the K+ is released, Na+ affinity is high and the cycle repeats

45
Q

what do ion pumps have the ability to do?

A

have the ability to generate membrane potential
- they are electrogenic pumps/transport proteins that generate a voltage across a membrane

gives an uneven overall net charge across membrane

membrane potential= voltage difference across a membrane

46
Q

how is voltage created?

think of ion pumps

A

voltage is created by differences in the distribution of positive and negative ions across a plasma membrane

47
Q

if sodium potassium pump sends three Na+ out and two K+ in, what relative charge, positive or negative, does it create inside the cell versus the exterior?

A

creates a negatively charged interior relative to a positively charged exterior.

extracting positive ions from the inside of the cell would create a net charge across the membrane (more positive outside than in)

48
Q

what is the main electrogenic pump of animal cells?

A

the Na+/K+ ATPase

especially important for neurons

49
Q

what is the result of membrane potential?

A

favors the passive transport of cations into the cell and anions out of the cell via ion channels

50
Q

what two types of gradients does the active transport create?

A

1) an electrical gradient = different net charge inside and outside the cell
2) a concentration gradient = more Na+ outside the cell causes the ions to diffuse down the concentration gradient

51
Q

Both the electrical and concentration gradients together create what?

A

these two forces create a different type of net gradient= an electrochemical gradient which drives processes like cellular respiration, transmission of nerve impulses and muscle contraction.

52
Q

what does secondary active transport do?

A
  • secondary active transport pumps can produce electrochemical gradients that store energy for cellular work
  • *use of an existing gradient to drive the active transport of a solute *

blocking any pump would result in no facilitated transport

53
Q

what is bulk transport?

A
  • large molecules that cannot cross the membrane by aforementioned mechanisms
  • therefore these large molecules must cross the plasma membrane in bulk transport via vesicles

requires energy

large molecules such polysaccharides, proteins, viruses, bacteria

54
Q

how do large molecules undergoing bulk transport leave and enter the cell?

A

leave a cell by exocytosis
enter a cell by endocytosis

55
Q

bulk transport

what happens in exocytosis?

A
  • vesicle fuses with the plasma membrane and releases contents into extracellular space
  • membrane proteins and phospholipids are incorporated into plasma membrane by exocytosis
  • can be regulated or constitutive
56
Q

what are the three types of processes of endocytosis?

A

1) phagocytosis= large particles engulfed into vacuole which fuses with the lysosome
2) Pinocytosis= nonspecific uptake of extracellular fluid
3) receptor-mediated endocytosis= triggered by binding of ligand to surface receptor.

57
Q

what happens in receptor-mediated endocytosis?

A

a vesical is formed through recruitment of a coated pit when specific molecules attach to their respective surface receptors on the membrane
- unlike pinocytosis, this is a specific mechanism in that it takes in specific molecules
- once in the molecules exit the vesicle, the receptors are returned to the cell surface for reuse.
- most blood cholesterol travels in lipoprotein particles
- LDL contains cholesterol destines for uptake by cells
- cells take in LDLs via receptor-mediated endocytosis (LDLs bind to specific surface receptors)

Bio test 2 (9 decks)

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