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AP Biology - Unger 2022/23 > Unit 3: Passive Membrane Transport > Flashcards

Unit 3: Passive Membrane Transport Flashcards

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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
Q

What is

Water potential

A

A water’s tendency to move

Includes pressure and the effects of solutes

26
Q

Solute potential (ψS) is always…

A

negative

27
Q

Ionization (i) of NaCl

Consider formula for solute potential

A

2

28
Q

Ionization (i) of sucrose

Consider formula for solute potential

A

1

29
Q

When calculating solute potential, temperature must always be in

A

Kelvin

30
Q

Water potential is normally expressed in

(what unit?)

A

bars

31
Q

What happens to a plant cell in a hypertonic environment?

A

Water moves out
Plant cell shrinks
May plasmolyze

32
Q

What happens to an animal cell in a hypertonic environment?

A

Water moves out
Animal cell shrinks

33
Q

What happens to a plant cell in an isotonic environment?

A

Equal movement of water in/out
No turgor pressure
Plant will wilt

34
Q

What happens to an animal cell in an isotonic environment?

A

Equal movement of water in/out
No change to cell size

35
Q

What happens to a plant cell in hypotonic environment?

A

Water moves into cell
Cell wall prevents bursting
Cell experiences turgor

36
Q

What happens to an animal cell in hypotonic environment?

A

Water moves into cell
Prolonged exposure may cause cell to lyse (burst)

37
Q

The ideal osmotic environment of plant cells

A

Hypotonic

38
Q

The ideal osmotic environment of animal cells

A

Isotonic

39
Q
A

Animal cell in hypotonic environment; cell lyses

40
Q
A

Animal cell in isotonic environment

41
Q
A

Animal cell in hypertonic environment

42
Q
A

Plant cell in hypotonic environment; makes plant turgid

43
Q
A

Plant cell in isotonic environment; makes plant flaccid

44
Q
A

Plant cell in hypertonic environment; can cause plasmolysis

45
Q

Define

Turgor pressure / Turgid

A

Outward pressure of a cell against a cell wall
Good for plants… Helps them stay upright!

46
Q

Define

Flaccid

(in terms of osmosis!)

A

Wilting
Due to plant’s exposure to isotonic or hypertonic environment

AP Biology - Unger 2022/23 (23 decks)

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