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Physiology > Transport Of Substances Through Cell Membranes > Flashcards

Transport Of Substances Through Cell Membranes Flashcards

1
Q

Channel proteins

A

Proteins have watery spaces and allow free movement of water and other non polar selected ions and molecules.

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2
Q

Diffusion

A

Continual Movement of molecules among one another in a liquid or gas

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3
Q

Carrier proteins

A

Bind with molecules or ions, conformational changes in the protein then move the substances

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4
Q

Difference between diffusion and active transport

A

Energy that causes diffusion is the energy of the normal kinetic energy of matter. In a active transport substance move against energy gradient and requires an additional source of energy besides kinetic energy

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5
Q

Simple diffusion

A

Kinetic Movement of molecules through the membrane openings or through intermolecular spaces

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6
Q

Facilitated Transport

A

Interaction with carrier protein aids passage of subs through the membrane by binding chemical with them

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7
Q

Rate of diffusion determined by

A
  1. subs available
  2. velocity of kinetic motion
  3. number and size of openings in the membrane
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8
Q

Ways of simple diffusion

A
  1. through interstates of the lips bilayer if subs are lips soluble
  2. Through Channel Proteins
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9
Q

Rate of diffusion lips soluble subs is directly proportional to

A

Lipid solubility is the subs

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10
Q

Aquaporins

A

Type of channel protein that selectively permits passage of water through cell membrane

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11
Q

How many types of aquaporins

A

13 different types in various cells of mammals

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12
Q

Provides selectivity to membrane that permit only certain molecules to pass through

A
  1. diameter of pore
  2. nature of electrical charges
  3. shape
  4. chemical bonds along its inside surface
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13
Q

Aquaporins selective to water

A

Have narrow pores that permit water molecules to diffuse. Too narrow our permit passage of any hydrated ions.

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14
Q

Potassium channels structure

A

They have tetrameric structures consisting of 4 identical protein sub units surrounding central pore. On top of the pore are “pore loops” form narrow selective filters, lined by carbon oxygens.

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15
Q

Potassium channel is selective to potassium

A

When hydrated potassium Jones enter the selective filter they interact with Carbonyl oxygens and shed their bound water permitting the dehydrated potassium one to pass.

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16
Q

Sodium being smaller why can’t it enter potassium channel

A

Small Size so Carbonyl oxygens too far apart and so they cannot interact and therefore excluded by selective filter

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17
Q

Sodium channel structure

A

Have gate like extension of the transport protein, it is only 0.3x0.5 nm in diameter and under surface of this channel are lined with amino acids that are strongly negatively charged

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18
Q

Sodium channel selective to Sodium

A

Negative charges of the protein pull dehydrated Sodium one into the channel and pulling it away from their hydrating water molecule and once inside Sodium in diffuse.

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19
Q

Gating

A

Means of controlling ion permeability of the channels

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20
Q

Two ways of opening and closing gates

A
  1. voltage Gating

2. chemical (Ligand) Gating

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21
Q

Voltage Gating

A

Molecular conformation of the gate or its chemical bonds respond to the electrical potential across the cell membrane

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22
Q

Sodium gate opening and closing

A

If negative charge on the inside of cell membrane, outside Sodium gates remain closed. When Inside of the membrane loses its negative charge, gates open and allow Sodium to pass

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23
Q

Potassium gates

A

On the intracellular end of the potassium channel they open when the inside of the cell membrane becomes positively charged

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24
Q

Chemical Gating

A

Opens by binding of a Chemical subs with a protein which causes a conformational change in protein that opens our closes the gate

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25
Q

Acetylcholine gates

A

Acetylcholine binds to open the gate of this channel providing a negatively charged pore of about 0.65nm in diameter.

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26
Q

Patch - clamp method

A

A mirco pipette tip with a diameter of 1-2 micrometers is put against outside a cell membrane. Suction is then applied inside the pipette to pull the membrane against the tip to create a seal resulting in a membrane “patch” through which electrical current flow can be recorded.

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27
Q

Alternate way of patch clamp method

A

Small piece of cell membrane patch at the end of pipette can be torn away from the cell. Pipette with the sealed patch inserted into a free solution which allows the concentration of ions both sides to be altered. Also the voltage between the 2 sides can be set or “clamped” to a five voltage

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28
Q

Carrier mediated diffusion /facilitated diffusion

A

Diffuse through the membrane with the help of specific carrier Proteins

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29
Q

Difference between facilitated and simple diffusion

A

Concentration of the diffusing subtance increases the Rate of simple diffusion increases, facilitated diffusion the rate cannot rise greater than Vmax level

30
Q

Mechanism of facilitated diffusion

A

Carrier protein has a large pore and also a binding receptor on the inside. Molecule to be transported enters the pore and becomes bound. In a fraction of a second, a conformational or chemical change occurs and the poor opens to the opposite side of the membrane. Because bidding force is weak the thermal motion of attached molecule causes it to break and be released

31
Q

Limit of rate of facilitated diffusion

A

Rate cannot be greater than the rate at which carrier protein molecule can undergo change back and forth between its 2 states

32
Q

Glucose carrier protein

A

Glucose transporter molecules GLUT

GLUT4 activated by insulin increase rate of facilitated diffusion of Glucose in insulin sensitive tissue

33
Q

Effect of concentration of sub across the membrane on net diffusion

A

Rate at which sub diffuse into the cell is proportional to the concentration of the sub outside the cell which determines how many molecules strike the outside of the menace each sec and vise versa. Therefore the net diffusion into the cell is proportional to the conc. On the outside minus the conc. On the inside.

34
Q

Effect of membrane electric potential on diffusion

A

If an electric potential is applied across the membrane an electric gradient is created and conc. Difference of the ins develop in the direction opposite to the electrical potential difference. The Conc. Difference now tends to move them back to position. When conc difference rises high enough the 2 effects balance each other

35
Q

Nernst equation

A

Determines the electric difference that will balance a given conc difference of univalent ions
EMF (millivolts) = +_61 logC1/C2

36
Q

Effect of pressure difference on diffusion

A

Pressure means the sum of all force of the different molecules striking a unit surface area at a given instant. If there is a higher pressure on one side of the membrane than on the other side the result is that increased amounts of energy are available to cause net diffusion of molecules from high pressure side towards low pressure side

37
Q

Osmosis

A

Process of net movement of water caused by conc difference of water
Osmosis occurs from pure water into the solution with a non diffusible solute.

38
Q

Osmotic pressure

A

The amount of pressure needed to stop Osmosis.
The pressure difference across the membrane at this point is equal to the Osmotic pressure of the solution that contains the non diffusible solute

39
Q

Factor that determines Osmotic pressure of a solution

A

The Conc of solution in terms of number of particles (molar concentration if it is a non dissociated molecule), not in the terms of mass of the solute.

40
Q

Osmole

A

The unit used To express the concentration of a solution in terms of no. Of particles instead of grams.
1osm is 1g Molecular of weight of osmotically active solute

41
Q

If solute doesn’t dissociate his many Osmoles?

A

1osm

42
Q

If solute dissociate into 2 ions how many Osmoles?

A

1g Molecular weight of the solute will become 2osm

Ex. 1g Molecular weight of Sodium chloride, 58.5g is equal to 2osm

43
Q

Osmolality

A

A solution that has 1 osm of solute dissolved in each kilogram of water is said to have an Osmolality of 1osm/kg

44
Q

Normal Osmolality of extracellular and intracellular fluids

A

300mOsm/kg of water

1osm/kg =1000mOsm/kg

45
Q

Osmotic pressure in the solution caused by concentration of 1osm/L At normal body temp 37°C

A

19,300 mmHg Osmotic pressure in the solution

1mOsm/kg equivalent to 19.3 mmHg Osmotic pressure

46
Q

Osmotic pressure of body fluids

A

Multiplying 19.3mmHg Osmotic pressure to the 300mOsm concentration of body fluids gives Osmotic pressure of the body fluids of 5790mmHg. The measured value average about 5500mmHg

47
Q

Why is actual value of Osmotic pressure of body fluids lower than the calculated amount

A

Many jobs in the body fluids such as Sodium and chloride ions are highly attracted to one another, they cannot move entirely unrestrained in the fluid and create their full Osmotic pressure potential. On average the actual Osmotic pressure of the body fluids is about 0.93 times the calculated value

48
Q

Osmolarity

A

Is Osmolar conc expressed as Osmoles per liter of solution.

49
Q

Active transport

A

Transport of substance uphill against a concentration gradient or uphill against a pressure or electrical gradient.

50
Q

2 types of active transport and basis of division

A

Divided according to the source of energy used to facilitate the transport :

  1. Primary active transport
  2. Secondary active transport
51
Q

Primary active transport

A

Subs transported using energy derived from the breakdown of adenosine triphosphate (ATP) or some other high - energy phosphate compound

52
Q

Secondary active transport

A

Transport of subs using energy derived secondarily from energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic subs between the 2 sides of the membrane created originally by primary active transport

53
Q

Example of primary active transport

A

Sodium - potassium pump

54
Q

Sodium - potassium pump function

A
  1. Responsible for maintaining the Sodium and potassium concentration difference across the cell membrane.
  2. controlling the volume of the cell
  3. Creating an electrical potential which is a basic requirement in nerve and muscle fibers for transmitting nerve and muscle signals
55
Q

Physical components of the Sodium - potassium pump

A

The carrier protein of the Sodium - potassium pump is a complex of 2 separate Globular proteins:large one called the alpha subunit mw=100,000 and smaller one called the beta subunit mw=55,000

56
Q

Function of beta subunit of Sodium - potassium pump

A

Not know except that it might anchor the protein complex in the lipid membrane

57
Q

Function of the alpha subunit of the Sodium - potassium pump

A
  1. 3 binding sites for Sodium ions on the protein that protrudes to the inside of the cell
  2. 2 binding sites for potassium ions on the outside
  3. Near the Sodium binding sites has ATPase activity
58
Q

Sodium - potassium pump mechanism to pump Sodium and potassium

A

2 K+ ions bind to the outside and 3 Na+ ions bind to the inside, ATPase becomes active which leaves to the cleavage of one ATP molecule, splitting it to Apple and liberating high energy causes a chemical and conformational change in protein carrier transporting the 3 Na+ outside and the 2 K+ inside

59
Q

Sodium - potassium pump mechanism to produce ATP

A

With other enzymes the Sodium - potassium ATPase pump can run in reverse. If the electrochemical gradient for Na+ and K+ are increased to a degree that the energy stored in their gradient is greater than the chemical energy of ATP hydrolysis these ions will move down their concentration gradient and the Sodium - potassium pump will synthesize ATP from ADP and phosphate

60
Q

Mechanism of controlling cell volume by Sodium - potassium pump

A

Inside the cell large no. Of Proteins and other organic molecules that cannot escape the cell they are negatively charged so attract Sodium, potassium and other +vely charged ions into the cell then causing Osmosis of water to the interior allowing cell to swell. Membrane is less permeable to Na+ and once out tend to stay there this represents net loss of ions outside the cell initiating Osmosis of water out of the cell.

61
Q

Na-K pump mechanism for creating an electric potential across the membrane

A

The pump moves 3Na ions out and 2K ions inside therefore there is a net of one positive charge moved from the interior of the cell to the exterior for each cycle. This creates positivity outside the cell and causes negativity on the inside. There is said to be electrogenic

62
Q

2 toes of secondary active transport

A
  1. Co transport

2. Counter transport

63
Q

Cotransport

A

The carrier in this serves as an attachment for both Sodium ion and substanc to be cotransported. Once both attach the energy gradient of the Sodium in causes both the Sodium in and other substance to be transported together to the interior of the cell

64
Q

Counter transport

A

Sub to be transported is on the inside of the cell and must be transported to the outside. Sodium ion binds to the carrier protein on the exterior surface and the sub binds to the interior projection, once both are bound confirmational change occurs and energy released by the action of Na ion moving to the interior causes the other sub to move to the exterior.

65
Q

Counter transport

A

Sub to be transported is on the inside of the cell and must be transported to the outside. Sodium ion binds to the carrier protein on the exterior surface and the sub binds to the interior projection, once both are bound confirmational change occurs and energy released by the action of Na ion moving to the interior causes the other sub to move to the exterior.

66
Q

Shifting Cotransport of Glucose and amino acidd function

A

Occurs through epithelial cells of the intestinal tract and the renal tubeless of the kidney to promote absorption of these sub into the blood

67
Q

Where does transport through a cellular sheet occur

A
  1. Epithelium of renal tubules
  2. Epithelium of intestinal tract
  3. Epithelium of gallbladder
  4. Epithelium of exocrine flame
  5. Membrane of the choroid plexus of the brain
68
Q

Mechanism for transportation through cellular sheet

A
  1. Active transport through the cell membrane on one side of cells in the sheet
  2. Either simple diffusion or facilitated diffusion through the membrane on the opposite side of the cell
69
Q

Mechanism for transportation of Sodium through epithelial sheet

A

Epithelial cells are connected tightly at the luminal pole by means of junction. The brush border on the luminal surface permeable to Sodium and water which diffuse readily to the interior. At the basal and lateral membrane Na + ions actively transported into extra cellular fluid creates high Na conc gradient across the membrane causes Osmosis of water. Thus active transport of Na at basolateral side of epithelium cells results in transport of Na as well as water.

70
Q

Vasicular transport

A

Transport of large molecule (macro molecules)
Achieved by 2 process :
1. Endocytosis
2. Exocytosis

Physiology (19 decks)

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