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General Biology II > Lect. 8 Membrane Transport - Energy and Metabolism > Flashcards

Lect. 8 Membrane Transport - Energy and Metabolism Flashcards

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1
Q

Definition of something that is “selectively permeable”

A

It allows some substances to cross it more easily than others.

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2
Q

Generally, biological membranes are permeable to:

A

small molecules (H2O, O2, CO2) and lipid-soluble substances

they can penetrate the hydrophobic interior of the bilayer

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3
Q

A selectively permeable bilayer is permeable to:

A
  • small uncharged molecules (O2)
  • very small polar molecules (H2O, CO2)
  • large non-polar molecules

urea, glycerol

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4
Q

A selectively permeable bilayer is impermeable to:

A
  • large polar molecules (glucose)
  • charged particles (ions: H+, Na+, Cl-, HCO-)

glucose, sucrose

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5
Q

Molecules enter/leave cells by: (5)

A
  1. diffusion
  2. osmosis (for water)
  3. facilitated diffusion
  4. active transport
  5. bulk transport: endocytosis & exocytosis

DOFAB

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6
Q

Water’s role in cells

A
  • essential for survival
  • prevents drying
  • all chemicals that enter a cell can only do so if dissolved in water

all cells must live in a moist env

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7
Q

Diffusion is a ____ process. Does the cell have to expend energy to make it happen?

A

Diffusion is a passive process: the cell does not have to expend energy to make it happen.

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8
Q

Diffusion occurs when there exists a ____ until ____ .

A

Diffusion occurs when there exists a concentration gradient (CG) until equilibrium is reached.

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9
Q

What is a concentration gradient?

A

The difference in concentration b/w the high concentration vs the area of low concentration.

ex: - campfire: heat source; warm when close, cool when far; diff in temp represents a gradient
- perfume spray at one end of room; high fragrance next to spray, low at opp side of room; diff in fragrance represents a gradient

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10
Q

Concentration Gradient in a Cell

ex: A lipid-soluble substance moves through the lipid bilayer from ____ to ____ concentration.

A

A lipid-soluble substance moves through the lipid bilayer from high to low concentration.

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11
Q

As long as CG exists, net movement of molecules will be:

A

in direction of gradient.

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12
Q

Once equilibrium is reached, net movement stops but:

A

exchange still occurs on a molecule for molecule basis.

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13
Q

Diffusion: a physical process based on random motion

All atoms and molecules possess ____ above absolute 0.

A

All atoms and molecules possess kinetic energy above absolute 0. This is why there is random molecular motion in diffusion.

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14
Q

Factors that influence diffusion rate: (3)

A
  1. Concentration gradient
  2. Size and shape (small=more free mov, globular moves easier)
  3. Temp (kinetic E of the particles)
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15
Q

What are the 2 general principles that apply to diffusion and osmosis?

A
  1. concentration gradient
  2. equilibrium
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16
Q

Osmosis = fluid diffusion

Water’s net mov is from the side of ____ solute concentration to side of ____ solute concentration.

A

Water’s net mov is from the side of low solute concentration to side of high solute concentration.

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17
Q

Osmosis = fluid diffusion

Water’s net mov is from the side of ____ solvent concentration to side of ____ solvent concentration.

A

Water’s net mov is from the side of high solvent concentration to side of low solvent concentration.

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18
Q

An animal cell in a hypotonic solution will be:
While a plant cell is:

A
  • lysed (pop)
  • turgid (normal)
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19
Q

When an animal cell is normal in an isotonic solution, a plant cell is:

A

flacid.

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20
Q

In a hypertonic solution, an animal cell is:
and a plant cell is:

A
  • shriveled/crenated
  • plasmolyzed
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21
Q

tonicity in plant cells

ex: When water seeks to exit cell, solution surrounding cells is:

plant looks sad

A

hypertonic

no turgor pressure on cell wall

22
Q

osmoregulation: control water balance

Paramecium is ____ to the pond in which it lives. To solve this problem, paramecium cells have a specialized organelle, the contractile vacuole, which functions as a pump to force water ____ the cell.

A

hypertonic, out of

23
Q

Definition of “tonicity”

A

Tonicity is a measure of osmotic pressure related to the concentration of impermeable solutes in a particular solution.

hypotonic / hypertonic / isotonic

24
Q

Definition of “osmolarity”

A

Osmolarity is a measure of molarity of all solutes (permeable + impermeable) dissolved in a particular solution.

hyperosmotic / hypo-osmotic / isosmotic

25
Q

In facilitated diffusion, molecules that are too big (glucose or AA) and polar/charged molecules require ____ to get them through the cell membrane.

A

In facilitated diffusion, molecules that are too big (glucose or AA) and polar/charged molecules require protein molecules to get them through the cell membrane.

26
Q

Types of transport proteins facilitate movement of molecules/ions across membranes: (2)

A
  1. channel proteins
    (tunnel like gap junctions)
  2. carrier proteins

down a concentration gradient

w/out carrier proteins, many molecules would not move across the membrane or would do so in such a slow fashion as to be useless to the cell

27
Q

Channel proteins

Channel proteins provide ____ corridors for the passage of specific charge/polar molecules/ions.

A

Channel proteins provide hydrophilic corridors for the passage of specific charge/polar molecules/ions.

28
Q

Channel proteins

Name the specialized gated channel proteins that carry water rapidly across the membrane in response to osmolarity.

A

aquaporins

gated: responds to chemical or electrical stimulus

29
Q

Carrier Proteins

Describe how a solute travels through carrier proteins

A

Carrier protein in the membrane selectively binds a solute particle and changes shape, opening a channel through the membrane. The solute can be transported into or out of the cell, but net mov is always from a region of higher to lower concentration.

30
Q

Carrier proteins

The rate of transport depends on: (2)

A
  1. the number of carrier proteins
  2. how fast a solute travels through them
31
Q

What are ion channels?

A

A specific category of protein that allow specific ions through, they function as gated channels.

Many ion channels are gated channels

32
Q

Active transport requires: (2)

A
  1. energy (ATP) since it’s going away from equilibrium
  2. carrier proteins

transporting molecules against the chemical gradient

33
Q

Active transport allows cell to maintain ____ internal conditions compared to external conditions.

A

Active transport allows cell to maintain different internal conditions compared to external conditions.

34
Q

How does ATP supply its energy for active transport?

A

By phosphorylating (giving phosphate) to the carrier protein. It triggers the conformational change required to transport ions across membrane.

35
Q

What is the sodium-potassium pump responsible for?

A

Creating/maintaining the membrane potential in neurons. It transports K+ in and Na+ out.

pump = active transport

36
Q

sodium-potassium pump

The exchange is unequal: 2 K+ imported in for 3 Na+ exported. This creates:

A

a membrane potential; negative interior relative to a positive exterior.

37
Q

Pumps that create membrane potentials are called:

A

electrogenic pumps

eletrically generating

38
Q

Creating membrane potentials stores energy that can be harnessed for other reactions. What are the main electrogenic pumps in animal cells and {plants, fungi, and bacteria}?

A

animal: sodium-potassium pump
plants, fungi, and bacteria: proton pump to export H+ ions from cytoplasm

39
Q

As a result of the membrane potential created via active transport, the passive transport of cations ____ the cell and anions ____ the cell is favoured.

A

As a result of the membrane potential created via active transport, the passive transport of cations into the cell and anions out of the cell is favoured.

40
Q

The 2 forces (gradients) that drive ions towards equilibrium:

A
  1. Concentration gradient (applies to all molecules on either side of membrane)
  2. Electrical gradient (applies to charged particles)

The 2 combined are collectively called the electrochemical gradient.

41
Q

Cotransport

ex: Plant cotransport proteins use the energy expended from H+ entering the cell (____ transport) to transport sucrose into the cell against its concentration gradient (____ transport).

A

Plant cotransport proteins use the energy expended from H+ entering the cell (passive transport) to transport sucrose into the cell against its concentration gradient (active transport).

42
Q

Macromolecules (polymers: proteins, polysaccharides) and larger particles need to use what to enter the cells?

A

vesicles

43
Q

Bulk Transport

Materials are transported out of the cell via:

A

exocytosis

ex: exit of insulin from pancreatic cells
- vesicle approaches plasma membrane
- fuses with it
- releases its contents outside

44
Q

Bulk Transport

Materials are transported into the cell via:

A

endocytosis

45
Q

Types of endocytosis:

A
  1. Phagocytosis
  2. Pinocytosis
  3. Receptor-mediated endocytosis
46
Q

How does Phagocytosis work?

“cell eating”

A
  • cell wraps pseudopodia around particle and forms vacuole (large vesicle)
  • vacuole then fuses with lysosome for digestion
47
Q

ex: White blood cells phagocytize microbes constantly to protect the body from possible infection. Microbial debris are released by:

A

exocytosis

48
Q

How does Pinocytosis work?

“cell drinking”

A
  • cell takes in portions of extracellular fluid and all solutes dissolved in the solution
  • non-specific mechanism (in comparison with receptor-mediated endocytosis)
49
Q

How does Receptor-mediated Endocytosis work?

A
  • A vesicle is formed when specific molecules attach to their respective surface receptors on the membrane
  • specific mechanism compared to pinocytosis
  • once the molecules exit the vesicle in the cell, the receptors are returned to the cell surface for reuse
50
Q

ex: What is the mechanism used for the intake of LDLs?

A

receptor-mediated endocytosis
- blood cholesterol travels as lipoprotein
- LDL destined for uptake in cells

LDL’s bind to specific surface receptors

51
Q

ex: What does influenza virus use for endocytosis?

A

Receptor-Mediated Endocytosis
Haemagglutinin is the protein responsible for both receptor binding and membrane fusion

General Biology II (9 decks)

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