Topic 3 - Membranes - Biology 241 - University of Calgary

• Molecules that tend to repel, not absorb, or not dissolve/mix with or by water.

Hydrophobic

• Molecules that tend to be attracted to, absorb, or dissolve/mix with or by water.

Hydrophilic

• Triglycerides.
• Phospholipids.
• Sterols.

What are the three main biological lipids?

• Energy storage.

What is the function of triglycerides?

• Hydrocarbon chain.
• Carboxyl group at the end of the chain.

What makes up a fatty acids structure? (2)

• Cannot absorb anymore hydrogen atoms in its carbon chain; commonly found in animal fats.
• No double bonds.

Saturated Fatty Acid (2)

• Can absorb additional hydrogen atoms; found in vegetable oils.
• Has a double bond.

Unsaturated Fatty Acid (2)

• 3 fatty acids.
• Glycerol anchor.

What makes up a triacylglycerols structure? (2)

• Charged molecule.
• Phosphate.
• Glycerol.
• 2 fatty acids.

What makes up a phospholipids structure?

• Charged molecule.
• Phosphate.
• Glycerol.

What makes up a phospholipids head group?

• 2 fatty acids.

What makes up a phospholipids tails?

• False.

A phospholipids head groups repels water, true or false?

• True.

A phospholipids tails repel water, true or false?

• Tight packing between them.
• Less fluidity.
• Restricted movement.

What are the characteristics of saturated phospholipid fatty acid tails?

• Looser packing between them.
• More fluidity.
• More movement.

What are the characteristics of unsaturated phospholipid fatty acid tails?

• Regulates transport in and out of the cell.

What does the cell membrane do?

• Membrane.

Which part of a cell is commonly known for the following:

• Communication
• Chemical Reactions

• Selective.

What type of permeability do membranes have?

• Allows some molecules to pass through the membrane.

Selective Permeability

• Yes.

Is it possible for lipids and proteins to coexist in a membrane?

B) Laterally.

Which way do lipids and proteins diffuse in a membrane?

A) Diagonally
B) Laterally
C) Horizontally
D) They don't diffuse across the membrane

• Protein.

Transport involves what types of channels and carriers?

• Involves enzymes and the binding of substrates to enzymes.

Enzymatic Activity

• Involves a hormone that binds to a receptor.

Signal Transduction

• Attachment points for cytoskeleton and extracellular matrix.

Attachment/Recognition

• Junctions - Connect and join two cells together.
• Enzymes - Fixing to membranes localizes metabolic pathways.
• Transport - Facilitated diffusion and active transport.
• Recognition - Markers for cellular identification.
• Attachment - Attachment points for cytoskeleton and extracellular matrix.
• Transduction - Receptors for peptide hormones.

JETRAT

(I found this online and thought it would help to remember the different types of membrane protein functions)

• Short fatty acid tails.
• Unsaturated fatty acids.
• Higher temperature.
• Sterols.

What factors increase the fluidity of a membrane?

• They change the strength of van der Waals forces.

How do short fatty acid tails increase a membranes fluidity?

• Sterols.

What factor both increases and decreases the fluidity of a membrane?

• To prevent freezing, sterols stop phospholipids from packing too tightly together.
• To prevent melting, sterols fill in gaps between phospholipids.

How do sterols regulate membrane fluidity (for both preventing freezing and melting)?

• More solutes can pass through the bilayer more quickly.

If fluid membranes are "leaky" what happens?

• Fewer solutes are able to pass through the membranes more slowly.

Why are viscous membranes better barriers?

• Small, uncharged, barely polar molecules.

What can diffuse across a lipid bilayer?

• Large, charged, polar molecules.
• Ions.

What cannot diffuse across a lipid bilayer? (2)

• Maintain homeostasis.
• Cells live in dynamic environments.
• Allows for concentrations of molecules on the inside that are different from the outside.
• Transport of molecules is regulated by cells.

Why do cells need a selective barrier? (4)

• An area of high concentration distributes evenly to an area of lower concentration.

Diffusion

• The concentration gradient (high in entropy).

Where does the energy in diffusion come from?

• Diffusion of water from a low solute to a high solute.

Osmosis

• Capability of a solution to modify the volume of cells by altering their water content.

Tonicity

• No net movement of water, causing the cell to not change in size or shape.

Isotonic Conditions

• Water diffuses out of the cell, causing shrinkage.

Hypertonic Conditions

• Water diffuses into the cell, causing swelling.

Hypotension Conditions

• Transport of a solute through diffusion.

Passive Transport: Simple Diffusion

• Moves down or with its concentration gradient.
• Powered by potential energy in the concentration of the gradient.
• A greater concentration gradient = greater rate of movement.

What are the characteristics of passive transport (simple diffusion)? (3)

• Involve protein carriers to help carry large/charged/polar molecules into and out of the membrane.

Passive Transport: Facilitated Diffusion

• Moves down with the concentration gradient.
• Direction of transport is reversible.
• Rate of transportation depends on concentration gradient.
• Substrate specific.

What are the characteristics of passive transport (facilitated diffusion)? (4)

• Bind a single solute and transport it across the lipid bilayer.

Carrier Proteins

• Form hydrophilic channels in the membrane which water and ions can move across.

Channel Proteins

• They move solutes away from equilibrium (low energy state).

How do cells establish a concentration gradient?

• ATP.

In order for cells to establish a concentration gradient, what molecule is needed?

• Involves specific protein pumps that cross the membrane and moves solutes up (against) their concentration gradient.

Primary Active Transport

• ATPO.

What does the transporter pump use in primary active transport?

• Chemical gradients.
• Electrochemical gradients.

What types of gradients do transporter pumps generate? (2)

• Specific protein pumps that move solutes up their concentration gradient.
• Powered by the energy released as different solutes move down its concentration gradient.

Secondary Active Transport Pumps (2)

• Both solutes move in the same physical direction.

Symporters

• Solutes move in opposite physical direction.

Antiporters

• Having both hydrophobic and hydrophilic parts.

Amphiphatic

• A type of membrane protein that is permanently attached to the biological membrane.

Integral Proteins

• Interact with the surface of the lipid bilayer of cell membranes.

Peripheral Proteins