Chapter 8: Transport Across Membranes

Passive, simple diffusion, facilitated diffusion, channel, carrier, active, primary, direct, secondary, indirect

2 Main Types of Membrane Transport:

1. ___ transport that moves down the [] gradient and no energy

   • ___ ___

   • ___ ___ by ___ and ___ proteins

2. ___ transport that moves against the [] gradient and needs energy

   • ___ or ___ transport

   • ___ or ___ transport

Gases, nonpolar, small, free energy, osmosis, solute [], hypertonic, hypotonic, isotonic

Passive Transport: Simple Diffusion:

• Happens with ___, ___, or ___ molecules

• Minimized ___ ___

• ___ is a subtype with water across a selectively permeable membrane

  • Determined by ___ ___

  • ___ solution with more solutes outside the cell

  • ___ solution with less solutes outside the cell

  • ___ solution with equal solutes across the cell

Transmembrane, channels, carrier, transporters, pumps

Transport Proteins:

• Are ___ proteins that transport molecules

3 Classes:

1. ___ for facilitated diffusion

2. ___ or ___ for facilitated diffusion

3. ___ for active transport

Hydrophilic, ions, sugars, AA, vitamins, carrier, channel proteins, [] gradient, number, transport proteins

Passive Transport: Facilitated Diffusion:

• For ___ molecules like ___, ___, ___, ___

• Needs ___ or ___ ___ to facilitate transport which are specific for 1 type of molecule

• Transport rate depends on ___ ___ and ___ of ___ ___

Selective, ions, small, regulated, ligand, mechanically, voltage, open, [] gradient, electrochemical potential, aquaporins

Passive Transport: Facilitated Diffusion: Channel Proteins:

• Are ___ for ___ or ___ molecules

• Are tightly ___ or gated by being ___-gated, ___-gated, ___-gated, or ___

• Transport by ___ ___ and ___ ___

• EX: ___ for water

Selective, larger, glucose, AA, regulated, uniport, coupled, symport, antiport

Passive Transport: Facilitated Diffusion: Carrier Proteins:

• Are ___ for ___ molecules like ___ or ___

• Are tightly ___ or gated

2 Types:

1. ___ for 1 solute

2. ___ for 2 solutes and is dependent on both

   • Can be ___ in the same direction or ___ in opposite directions

Erythrocyte, glucose, uniport, GLUT1, glucose, GLUT1, outside, T1, T2, inside, glucose, second conformational change, T1

Example of Carrier Proteins:

• ___ uptake of ___ by a ___ carrier called ___

Steps:

1. ___ binds to ___ that is open to the ___ of the cell or in ___ conformation

2. Binding triggers ___ conformation that is open to the ___ of the cell

3. ___ is released and protein undergoes a ___ ___ ___

4. Protein returns to ___ conformation

Exergonic, specific, regulated, faster, saturated, hyperbolic, linear

Facilitated Diffusion Kinetics:

• Is an ___ process

• Proteins are ___ and can be ___

• Transport by channels is ___ than carrier proteins

• Carrier proteins can become ___ as solute [] increases

• If graphed, facilitated diffusion plot is ___ vs simple diffusion plot is ___

Against, energy, endergonic, exergonic, ATP hydrolysis, directionality, direct, indirect, nutrients, wastes, ion nonequilibrium []

Active Transport:

• Solutes move ___ the [] gradient

• Needs ___

• Couples ___ transport to an ___ process, usually ___ ___

• ___ of solute transport in 1 direction

• Can involve ___ or ___ active transport

3 Functions:

1. Uptake of ___

2. Removal of ___

3. Maintenance of ___ ___ ___

Exergonic, ATP hydrolysis, H+, electrochemical [], solute, ions, H+, solute, H+

Active Transport: Direct vs Indirect:

• Direct couples transport with ___ processes like ___ ___ that can transport solutes like ___ to establish an ___ ___

• Indirect couples transport of ___ with ___ or ___, the ___ goes against its [] gradient and ___ goes down its [] gradient

P, phosphorylation, V, vacuole, F, factor, ABC, ATP-binding cassette

Active Transport: Direct Transport:

• 4 Types of ATPases

  1. ___-type ATPases (___)

  2. ___-type ATPases (___)

  3. ___-type ATPases (___)

  4. ___-type ATPases (___)

Na+/K+ ATPase, P-ATPase, inside, E1, 3 Na+, E1, phosphorylation, alpha subunits, ATP, E2, outside, 2 K+, E2, dephosphorylation, alpha subunits, E1, 2 K+, inside

Example of Direct Transport:

• The ___/___ ___ which is a type of ___-___ in animal cells

• Initial state has protein open to the ___ of the cell and is in ___ conformation

1. ___ (#) ___ binds to ___

2. Binding triggers ___ of ___ ___ by ___

3. The rxn causes a conformational change to ___ that releases the solute to the ___ of the cell

4. ___ (#) ___ binds to ___

5. Binding triggers ___ of ___ ___ to return to ___ conformation

6. The ___ (#) ___ are released to the ___ of the cell

Na+/glucose symporter, outside, E1, 2 Na+, E1, glucose, inside, E2, 2 Na+, Na+/K+, outside, Na+, glucose, inside, E1

Example of Indirect Transport:

• The ___/___ ___

• Initial state is open to the ___ of the cell and is in ___ conformation

1. ___ (#) ___ binds to ___

2. Binding triggers ___ to bind and a conformational change

3. Opens to the ___ of the cell and is in ___ conformation

4. ___ (#) ___ are released but are pumped by the ___/___ pump to the ___ of the cell

5. Release of ___ is followed by ___ release to the ___ of the cell

6. Returns to ___ conformation

Small polar, small polar, large polar, ions, large polar, ions

Transport Types:

1. Simple Diffusion: ___ ___

2. Facilitated Diffusion: ___ ___, ___ ___, and ___

3. Active Transport: ___ ___ and ___

No, down, energy, driving force, equilibrium, ions, sum, equilibrium

Solute Movement: [] gradient or electrochemical gradient:

[]:

• For solutes with ___ +

• Simple or facilitated diffusion goes ___ the [] gradient and no ___ needed

• [] gradient increases the ___ ___ of the solute

• ___ when there is no [] gradient

Electrochemical:

• For solutes that are ___

• Is the ___ of [] and + gradients

• ___ when chemical and electrical gradients are balanced

2

Which of the following is likely to cross the membrane the slowest?

1. Glucose

2. Na2+

3. Vitamin K (hydrophobic)

4. Estrogen (large, hydrophobic)

4

Which of the following molecules can enter cells by diffusion in the absence of a transporter protein?

1. oxygen and K +

2. K + and H +

3. carbon dioxide and H +

4. oxygen and carbon dioxide

3

Celery stalks that are immersed in freshwater for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. Which of the following statements is true?

1. Freshwater and the salt solution are both hypertonic to the cells of the celery stalks

2. Freshwater and the salt solution are both hypotonic to the cells of the celery stalks

3. Freshwater is hypotonic and the salt solution is hypertonic to the cells of the celery stalks

4. Freshwater is hypertonic and the salt solution is hypotonic to the cells of the celery stalks

2

How is facilitated diffusion similar to active transport?

1. Both involve moving substrates down a concentration gradient.

2. Both involve specific transport proteins.

3. Both consume ATP.

4. Both can involve “pump” proteins.

2

Which if the following is most likely to be transported by a carrier protein?

1. Tyrosine up its concentration gradient

2. Ions down their concentration gradient

3. Alanine down its concentration gradient

4. Water against its gradient