Ch. 8 - Membrane Transport

Diffusion is the…

Passive movement of particles down it’s concentration gradient.

To predict the direction of particles during diffusion, identify the which side between the permeable membrane has ____ particles, net movement will be towards the side with ____ particles

more; fewer

Name the 3 Types of Membrane Transport

1. Simple Diffusion

2. Facilitated Diffusion

3. Active Transport

Diffusion = net movement from high → low concentration across a selectively permeable membrane. (True or False)

True

_______ _______ is the unassisted movement of a solute from high concentration to low concentration, driven by _______.

Simple Diffusion; entropy

“Simple diffusion is a non-spontaneous process, that maximizes free energy (G > 0)”. True or False? Explain.

False, Simple diffusion is an energetically favored process that minimizes free energy, making it spontaneous.

Define Osmosis.

The simple diffusion of water through a selectively permeable membrane.

In osmosis, the net movement of water moves towards the area of _______ solute concentration

Higher

_______ is how a solution affects cell volume, depends non-penetrating solutes and movement of water. This determines whether cell shrinks or swells.

• Name the 3 terms of this.

Tonicity

• Isotonic, Hypertonic, Hypotonic

Match the Tonicites

1. Lower solute concentration; cell swells or bursts as water enters.

2. Equal osmotic concentrations; no net movement of water.

3. Higher solute concentration; cell shrinks as water leaves.

1. Hypotonic

2. Isotonic

3. Hypertonic

How is Osmolarity different from Tonicity when it comes to affecting cell size?

Measures both penetrating and non-penetrating solute particles in total concentration

What transport that requires membrane proteins for substances unable to diffuse across the membrane due to size or charge.

• Is this an Endergonic or Exergonic process?

Facilitated Diffusion

• Exergonic

Facilitated Diffusion can be carried out by _______ or _____ ______.

• What specific molecules does each transport?

Channels; Carrier Proteins

• Channels transport ions and water. Carrier proteins transport glucose and amino acids.

Fill in the Channels (Facilitated)

• _________: Selective for specific ions (sodium, chloride, calcium)

• _________: Larger openings, allow for less specific passage based on size restriction (<15,000 Daltons)

• _________: Helps water movement across membranes. Rapid compared to simple diffusion.

• Ion Channels

• Porins

• Aquaporins

Ion Channels have ____ channels that are always open, and _____ channels that are regulated by mechanical, ligand, or voltage-related stimuli.

Leak; Gated

Aquaporins have a _______ channel design with a _____ molecule in the middle. Regulated by _______ into membranes (not gated)

Tetramer; lipid; insertion

What do Carrier Proteins do?

Bind to solutes and transport them across the membrane.

Fill in the Carrier Blanks

• ________ transports a single solute.

• Antiporters transports two solutes in the ______ direction.

• Symporters transports two solutes in the ______ direction.

• Uniporters

• Opposite

• Same

Name a Carrier Protein that removes CO₂ waste from tissues.

• CO2 ____ erythrocytes → combines w/ water to form _______ → it’s then transported out while _____ enters. Reverse process occurs in lungs.

The Chloride-Bicarbonate Exchanger

• enter; bicarbonate; chloride

Name Carrier Protein that transports glucose from high to low concentration in erythrocytes. (blood sugar)

• Finish the Steps

  1. ______ protein binds glucose on one side

  2. protein changes shape, this is called…

  3. glucose _______ on the other side

GLUT1 Glucose Transporter

1. GLUT1

2. conformational changes

3. releases

Facilitated vs. Simple Diffusion

• Which Diffusion is Slower? Explain.

• Which Diffusion is less restrictive and involves a wider range of solutes?

• Facilitated, due to conformational changes and binding processes involved.

• Simple

On a line graph, The rate of facilitated diffusion is faster at lower concentrations but eventually _______, or becomes saturated (finite proteins), as the concentration gradient increases.

Plateau’s

_____ ______ is the movement of solutes against their concentration gradient, requiring energy, making it a highly ________ process.

Active Transport; endergonic

Active Transport often couples endergonic transport to an exergonic process, such as ____ ______ and ______ ______.

ATP Hydrolysis; existing gradients

Fill in the Blanks (Types of Active Transport)

• _____ active transport involves the direct use of ATP.

• _____ active transport involves the indirect use of ATP

• Primary

• Secondary

A transport ATPase is a membrane protein that…

hydrolyzes ATP to move solutes across membranes

What kind of ATPase is used in the sodium-potassium pump (transports heavy metal ions and K⁺)

• What does it stand for?

P-type

• P is for phosphorylation

What kind of ATPase keeps the pH of the compartment low which activate hydrolytic enzymes

• What does it stand for?

• What specific kind of membrane does this occur at?

V-type

• V is for Vacuole

• Lysosomal Membrane and Vacuolar Membrane

Which ATPase uses the proton gradient to drive ATP synthesis?

• Where does occur in eukaryotes

F-type

• inner mitochondrial membrane

ABC-type ATPase’s are importers of a variety of solute/nutrients and exporters of _____, ______, and etc.

drugs; toxins

In the Sodium-Potassium pump (primary active transport)

• 3 Na⁺ ions are transported___ and 2 K⁺ ions are transported ___, important for maintaining membrane potential and overall cell function.

  1. E1 Conformation: Opens to the inside of the cell where…

  2. What occurs by ATP leading to E2 Conformation?

  3. Pump opens to the outside; sodium ions are _____ while potassium ions ___.

  4. What occurs, returning pump to E1 and releasing potassium ions.

• Out; In

  1. Sodium ions bind

  2. Phosphorylation

  3. released; bind

  4. De-Phosphorylation

Example of secondary active transport that uses a sodium gradient created by sodium-potassium pump to move glucose into cells against its gradient?

• Na⁺ and glucose move in the _____ direction. After transported into the cell, Na⁺ moves _____ its gradient and glucose is moved _____ its gradient

• What bodily function does this help in?

Sodium-Glucose Symporter

• same; down; against

• Intestinal Uptake

Match the main type of transport with the molecules it can transport.

• Small uncharged polar (water) /nonpolar (CO₂) molecules; Large nonpolar molecules (oils, steroids)

• Large polar molecules (glucose); Ions

• Small and Large polar molecules; Ions

• Simple Diffusion

• Active Transport

• Facilitated