Unit 3: Passive Membrane Transport Flashcards

1
Q

Define

Semi-permeable

A

Allowing some, but not all, substances to pass through

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2
Q

Describe how nonpolar substances move across the membrane

A

Directly through phospholipid bilayer

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3
Q

Why can nonpolar substances get through the phospholipid bilayer?

A

Dissolve into the lipid tails that make up the bilayer

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4
Q

Describe how polar substances move across the membrane

A

Through channels or carrier proteins (transport proteins)

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5
Q

Why can polar substances not get through the phospholipid bilayer?

A

Hydrophobic core (lipid tails) repel the polar or charged molecules; particles cannot dissolve in hydrophobic core

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6
Q

Examples of nonpolar substances

A

CO2, O2

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7
Q

Examples of polar substances

A

Glucose, ions

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8
Q

Describe

Transport proteins

A

Chains of amino acids, with polar amino acids on the cytoplasmic and extracellular side of protein, plus through the center to make a canal through which particles can pass;
Nonpolar amino acids make up the exterior portion that gets sandwiched in lipid tails

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9
Q

Compare and contrast

Channel and carrier proteins

A

Both:
* Transmembrane proteins
* Allow particles to move through membrane
* Specific to one or only a few particles

Differences:
* Channel proteins do not change shape; carrier proteins do
* Channel proteins allow faster passage through membrane; carrier proteins are slower

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10
Q

Define

Aquaporin

A

A channel protein that is specific to water

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11
Q

What is meant by

Transport protein specificity

A

Each transport protein (channel or carriers) allow only one or a few specific particles to cross
Cells can have unique combinations of transport proteins to suit their specific needs (and can even change which proteins they have on their membrane at a given time)

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12
Q

Describe

Concentration gradient

A

A difference in solute concentrations between two regions

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13
Q

Characteristics of

Passive membrane transport

A
  • Does not require cellular energy
  • Occurs spontaneously (consequence of random thermal motion)
  • Net movement of particle from area of higher to lower concentration (“down” concentration gradient)
  • Continues until dynamic equilibrium is reach
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14
Q

Types of

Passive membrane transport

A
  • Simple diffusion
  • Facilitated diffusion (including osmosis)
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15
Q

Define

Dynamic Equilibrium

A

When the net movement of particles is equal in all directions

Individual particles still move

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16
Q

What type of particles move via simple diffusion?

A

Small & nonpolar

Ex: CO2 and O2

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17
Q

Describe

Simple diffusion

A

Movement of small, nonpolar substances across the phospholipid bilayer, from an area of high concentration to an area of low concentration

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18
Q

Describe

Facilitated diffusion

A

Movement of large and/or polar/ionic substances across the membrane via channel or carrier proteins, from an area of high concentration to an area of low concentration

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19
Q

Define

Osmosis

A

Diffusion of water across a membrane

20
Q

Define

Tonicity

A

Concentration of solutes that a membrane is not permeable to (cannot pass through membrane)

21
Q

Define

Hypotonic

A

Side of a membrane with lower tonicity / higher free water concentration

22
Q

Define

Hypertonic

A

Side of a membrane with higher tonicity / Lower free water concentration

23
Q

Define

Isotonic

A

Equal tonicity across a membrane

24
Q

In what direction does water move during osmosis?

A

Higher → Lower free water concentration
Hypotonic → Hypertonic
Higher ψ → Lower ψ

25
# What is Water potential
A water's tendency to move | Includes pressure and the effects of solutes
26
Solute potential (ψS) is always...
negative
27
Ionization (*i*) of NaCl | Consider formula for solute potential
2
28
Ionization (*i*) of sucrose | Consider formula for solute potential
1
29
When calculating solute potential, temperature must always be in
Kelvin
30
Water potential is normally expressed in | (what unit?)
bars
31
What happens to a plant cell in a hypertonic environment?
Water moves out Plant cell shrinks May plasmolyze
32
What happens to an animal cell in a hypertonic environment?
Water moves out Animal cell shrinks
33
What happens to a plant cell in an isotonic environment?
Equal movement of water in/out No turgor pressure Plant will wilt
34
What happens to an animal cell in an isotonic environment?
Equal movement of water in/out No change to cell size
35
What happens to a plant cell in hypotonic environment?
Water moves into cell Cell wall prevents bursting Cell experiences turgor
36
What happens to an animal cell in hypotonic environment?
Water moves into cell Prolonged exposure may cause cell to lyse (burst)
37
The ideal osmotic environment of plant cells
Hypotonic
38
The ideal osmotic environment of animal cells
Isotonic
39
Animal cell in hypotonic environment; cell lyses
40
Animal cell in isotonic environment
41
Animal cell in hypertonic environment
42
Plant cell in hypotonic environment; makes plant turgid
43
Plant cell in isotonic environment; makes plant flaccid
44
Plant cell in hypertonic environment; can cause plasmolysis
45
# Define Turgor pressure / Turgid
Outward pressure of a cell against a cell wall Good for plants... Helps them stay upright!
46
# Define Flaccid | (in terms of osmosis!)
Wilting Due to plant's exposure to isotonic or hypertonic environment