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From Flashcardlet > BMS 108 Ch. 06 Membrane Transport & Electrical Potential > Flashcards

BMS 108 Ch. 06 Membrane Transport & Electrical Potential Flashcards

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0
Q

What are the four general categories of transport across plasma membranes?

A

Carrier-mediated transport
Non-carrier mediated transport
Active transport
Passive transport

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1
Q

The plasma membrane is ___________ ____________ — allowing only certain kinds of molecules to pass.

A

selectively permeable

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2
Q

What is the difference between active and passive transport?

A

Active: requires E; up [gradient]

Passive: no E required; down [gradient]

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3
Q

What are some compounds that readily diffuse through the cell membrane?

A

nonpolar compounds, H2O, CO2 and other gases

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4
Q

Are both charged molecules (Na+) and polar molecules (H2O) able to diffuse across the plasma cell membrane?

A

No. Charged molecules and MOST polar molecules can not.

  1. Charged molecules ALWAYS require a transporter
  2. Polar molecules USUALLY require a transporter
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5
Q

How does a charged molecule get through the plasma cell membrane?

A

Using ion channels or some other transporter.

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6
Q

What are the four things that rate of diffusion of a compound depends on?

A
  1. Magnitude of its concentration gradient
  2. Permeability of the membrane to it
  3. Temperature
  4. Surface area of the membrane
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7
Q

What is osmosis?

A

Net diffusion of H2O across a selectively permeable membrane.

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8
Q

Is osmosis active or passive transport?

A

passive

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9
Q

Is H2O more or less concentrated where there are more solutes?

A

Less

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10
Q

Some cells have water channels that facillitate osmosis. What are they called?

A

aquaporins

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11
Q

What is osmotic pressure?

A

the force that would have to be exerted to stop osmosis

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12
Q

What is osmotic pressure an indicator of?

A

how much H2O wants to diffuse

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13
Q

Is osmotic pressure proportional to solute concentration?

A

yes

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14
Q

What is a solution?

A

A homogenous mixture of two or more components

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15
Q

What is a mole?

A

A compound’s molecular weight in grams, which always contains 6.02 x 10²³ molecules of that compound.

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16
Q

How do you calculate concentration of a solution?

A

Concentration = amount of solute / amount of solvent

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17
Q

How do you calculate % concentration of a solution?

A

% concentration = grams of solute / 100 ml solvent * 100

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18
Q

What is the difference between molarity and molality?

A

Molarity (M) = moles of solute / 1 L solution (solvent is added so the total solution = 1 L)

Molality (m) = moles of solute / 1 Kg solvent (1 Kg of solvent is added to solute)

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19
Q

What is osmolality?

A

Osmolality is the sum of molalities of each solute in a solution.

e. g. 1 m glucose + 1 m fructose = 2 Osm
* If a selectively permeable membrane separates two solutions with equal osmolalities, no osmosis will occur.

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20
Q

Why does a 1 m solution of NaCl yield a 2 Osm solution?

A

Because NaCl dissociates in water into Na+ and Cl-, doubling the number of molecules.

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21
Q

When is Carrier-mediated transport required?

A

When molecules are too big or too polar to diffuse across the plasma membrane.

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22
Q

What are three features protein carriers exhibit?

A
  1. Specificity for a single molecule
  2. Competition among similar substrates for transport
  3. Saturation when all carriers are occupied (Tm - transport maximum)
23
Q

Why can carrier mediated transport be saturated?

A

Because is all the carriers are occupied, no further gain is possible

24
Q

What is facilitated diffusion?

A

Passive transport down a [gradient] by carrier proteins. A type of carrier mediated transport.

25
Q

How does facilitated transport work?

A

Glucose binds to a protein receptor causing a conformational change in the structure and releases the glucose into the cell. The unbinding glucose causes another conformational change that returns the protein transport to its original shape.

26
Q

What is a Primary Active Transport Pump?

A

Transport of molecules AGAINST the concentration gradient

  • requires DIRECT binding of ATP
  • requires a carrier protein
27
Q

What specific Primary Active Transport Pump is most common in our cells?

A

The Na+/K+ Pump

28
Q

What does the Na+/K+ Pump do?

A

It uses ATP to move 3 Na+ out and 2 K+ into the cell.

  • Both molecules are going against [gradient]
  • Most important in the body
  • 30% of ATP is used just for this
29
Q

What is the protein structure that makes up the Na+/K+ Pump called?

A

ATPase

30
Q

What is Secondary Active Transport?

A

One type of molecule moving DOWN its concentration gradient coupled with another molecule that needs to move UP its concentration gradient.

31
Q

Define Cotransport.

A

secondary transport in the same direction as Na+ (aka symport)

32
Q

What is Countertransport?

A

moves a molecule in the opposite direction to Na+ (aka antiport)

33
Q

Why do we say secondary active transport is energy requiring?

A

It is energy requiring because molecule #1 (moving down [gradient]) originally needed ATP (and thus Primary Active Transport) in order to establish its concentration gradient. It still requires energy, just 1 step back.

Molecule #2 plays off of #1’s gradient, thus ATP and phosphorylation are not directly coupled to the carrier of molecule #2

34
Q

In what ways does glucose get across the membrane epithelia?

A

Glucose uses secondary active transport to enter the epithelial cell and facilitated transport to exit the cell into the bloodstream.

35
Q

What is absorption?

A

the transport of digestion products across intestinal epithelium into blood

36
Q

What is reabsorption?

A

transport of compounds out of the urinary filtrate back into the blood

37
Q

What is the definition of Transcellular Transport?

A

Movement of material from one side of an epithelial cell to the other

38
Q

What is Paracellular Transport? What limits this kind of transport?

A

Movement of material through tiny spaces between epithelial cells; Limited by junctional complexes that connect adjacent epithelial cells

39
Q

What are four types of intercellular junctions?

A
  1. Tight Junction
  2. Adherens Junction
  3. Desmosomes
  4. Gap Junction
40
Q

To respond to a chemical signal, a target cell must have a ________ _______ for it.

A

receptor protein

41
Q

In _________ signaling, cells secrete regulatory molecules that diffuse to nearby target cells.

A

paracrine

42
Q

In ___________ signaling, cells secrete regulatory molecules that bind to and regulate itself.

A

autocrine

43
Q

In ________ signaling, 1 neuron sends neurotransmitter messages to another cell via synapses.

A

synaptic

44
Q

Some cells (e.g. cardiac muscle cells) use ______ __________ to pass signals directly from one cell to the next.

A

gap junctions

45
Q

In __________ signaling, cells secrete chemical regulators that move through the bloodstream to distant target cells.

A

endocrine

46
Q

Regulatory molecules used in cell signaling can be either ______ or ________.

A

Polar; nonpolar

47
Q

What do nonpolar molecules generally effect?

A

Nonpolar molecules pass through the plasma membrane and bind to receptors in the nucleus. They affect the rate of transcription (protein production)

48
Q

What do polar regulatory molecules generally effect?

A

Polar regulatory molecules bind to surface receptors of cells and either open ion channels directly OR send second messengers into the cytoplasm to mediate actions of a different regulatory molecule (open ion channel elsewhere or up/down regulate an enzyme).

e.g. acetylcholine, epinephrine, insulin

49
Q

What ions have a high concentration outside the cell? Inside the cell?

A

Na+, Ca ++, Cl-; K+

50
Q

What ion is the cell membrane most permeable to?

A

K+

51
Q

What is the defintion of Resting Membrane Potential (RMP)?

A

The membrane voltage of a cell not producing impulses. Measured in millivolts (mV)

52
Q

What is an average RMP?

A

-65 to -85 mV

53
Q

Why doesn’t K+ leave the cell, flowing down its concentration gradient?

A

The chemical drive of K+ is countered by the Na+/K+ pump and the electrical attraction of K+ to P- inside the cell, causing equillibrium.

54
Q

What determines the RMP of a cell?

A
  1. Many open K+ leak channels

2. Na+/K+ Pump

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