Chapter 6: Cell Membrane and Phospholipids

What do phospholipids form?

Bilayers

(hydrophilic heads face solution and hydrophobic tails face each other)

What does permeability mean?

The ability to go through something

Phospholipid bilayers are _____ permeable.

Selectively

Do small nonpolar molecules move across bilayers quickly or slowly? (O2, CO2, N2)

Moves quickly through the bilayers

Do small uncharged polar molecules move more quickly or slowly? (H2O)

Moves more slowly through the bilayers

Do large uncharged polar molecules mover quickly or slower through the bilayers? (Glucose, Sucrose)

Move very slow through the bilayers

Do charged molecules (ions) go through the bilayers? (Cl-, K+, Na+)

NO, they do not cross

How does temperature affect permeability?

Higher temp = More permeable

How do the number of double bonds affect permeability?

The number of bonds determines if the lipid is saturated or unsaturated

What effects membrane permeability?

Lipid length, Membrane proteins, number of cholesterol, temperature, number of bonds

Describe unsaturated hydrocarbon tails

Has double bonds that causes a rigid bend causing molecules to pass through the bilayer easily (easy to pass through)

Describe saturated hydrocarbon tails

Does not have double bonds so tails are closely packed making the membrane denser and less permeable (hard to get through)

Which phospholipids are less permeable (hard to get through)

Saturated Phospholipids

Which phospholipids are more permeable?

Unsaturated Phospholipids

How does cholesterol alter membrane permeability?

Increases the density to the hydrophobic part (tails)

How does cholesterol alter membrane permeability differently at warm vs. cool temperature?

At high temps cholesterol reduces permeability and low temps increases permeability

Membrane fluidity increases with _____

Temperature

In the membrane, when do molecules move faster?

When the temperature increases

What is Diffusion?

Movement of molecules from a high concentration to a low concentration until equilibrium is reached. (no energy is used)

What is osmosis?

Is the solute is charged or large (ions or glucose) water will move from a low to high concentration (uses no energy)

Osmosis has what three types of conditions?

1. Hypertonic

2. Hypotonic

3. Isotonic

What does hypertonic mean in osmosis?

Water leave the vessel and causes the cell to shrink

What does hypotonic mean in osmosis?

Water flows into the cell and the cell swells and bursts

What does isotonic mean in osmosis?

Water is inside and outside the cell causing no change

Which osmosis condition is where the solute concentrations higher outside the cell?

Hypertonic

Which osmosis condition is where the solute concentrations lower outside the cell?

Hypotonic

Which osmosis condition is where the solute concentrations indie/outside the cell is the same?

Isotonic

What type of solution kills animal cells?

Hypotonic solutions

What type of solution is ideal for plants?

Hypotonic Solution, due to the cell wall keeps it safe

How can proteins alter membrane structure?

They’re incorporated into the membranes, and are amphipathic (polar and nonpolar) amino acids

____ is amphipathic.

Proteins

What are the functions of channel proteins?

To facilitate diffsuion

What are ion channels?

Pores specialized for specific ions diffusion

What are electrochemical gradients?

Occurs when ion concentration builds up on one side of a membrane creating a charge gradient

How do ions diffuse into their electrochemical gradient?

Diffuse down from high to low concentration

What are channel proteins?

Selective, allowing only one type of ion or small molecule

• ex: aquaporins- permit water to cross membrane

What is an example of channel proteins?

Aquaporins

What are gated channels?

Can open or close in response to a signal and is often carefully controlled by the cell

• movement is regulated

Carrier proteins facilitate diffusion of _____.

Larger molecules

What are carrier proteins?

Change shape to transport large molecules like glucose across the membrane

What is the difference between channels and pumps?

Channels don’t use energy and go with the concentration gradient. Pumps use energy and go against gradient

Pumps do _____

Active transport

If cells need to move things against the concentration gradient, what will they use?

Active tranport (Pumps)

What is active transport?

Movement of molecules against the gradaient

What is an example of a active transport pump?

Sodium-Potassium Pump

What are the three types of transport?

1. Diffusion

2. Facilitated Diffusion

3. Active Transport

What is included in facilitated Diffusion?

Channel or Carrier proteins