What is the general formula for fatty acids?

CH3(CH2)nCOO-

T/F: fatty acids can be amphipathic and saturated/unsaturated

True

Are FA's usually cis or trans DB? Why?

Cis - It lowers MP by introducing kinks into overall structure

What functional groups are FA's?

Long chain carboxylic acids

What is the shorthand notation for FA's?

(# C) : (# DB) Δ (location of DB)

Do longer fatty acids melt at higher or lower temps?

Higher

Do saturated FA's melt at higher or lower temps?

Higher

What has a greater effect on MP?

Saturation/Unsaturation

Do unsaturated FA's melt at higher or lower temps?

Lower

Why can unsaturated FA's not pack together?

Cannot pack because of the bend - Sat FA's can align closely = maximize van der waals interactions

Which FA's can pack better? cis or trans

Trans

What are FA's stored as?

Triacylglycerol (TAG)

What are the 3 membrane lipids?

- Glycerophosphlipids - Sphingolipids - Cholesterol

Glycerophospholipids have fatty acyl groups ____ attached

Covalently

T/F: The presence of a large polar group makes these molecules amphipathic

True

What are the characterstics of cholesterol? 2

- Rigid, non polar - Weakly amphipathic (Only one -OH group), mostly hydrophobic

What is the purpose of cholesterol?

Maintain fluidity and rigidity

T/F: Nonpolar portion of cholesterol is found outside membrane

False, its found in the membrane

What forms micelles or bilayers in water?

Amphipathic molecules

What is the purpose of micelles?

Eliminate unfavorable contact between water and hydrophobic tails - permit solvation of polar head groups

Membrane lipids form a _____ when mixed in water

Bilayer

FA form ______ when mixed in water

Micelles

Lipid bilayers form _________

Spherical vesicles - liposomes

T/F: Lipid bilayers are stable

True

What does the transition/melting temp of a lipid bilayer mean?

Temp of its transition from ordered crystalline to a fluid state (depending on acyl unsaturation/length)

What do acyl chains look like during the ordered gel phase?

Below transition temp, acyl chains pack together in van der waals contact

What do acyl chains look like during disordered liquid crytaline state?

Above transition temp, acyl chains move freely and rapidly

What does the trans temp look like for an artificial membrane?

Very sharp

Membranes must operate ____ gel temp (MP) but not be disordered

Above

With decreasing temperature, what would the FA chains look like in the membrane?

Shorter Unsaturated

With increasing temp, what would the FA chains look like?

Longer Saturated

How does cholesterol increase membrane rigidity?

Limits rotational movement of neighboring acyl tails = increase in van der waals interactions

What type of diffusion (movement) do lipids undergo?

Lateral (Quick)

What diffusion (movement) do lipids not undergo? Why?

Transverse - Too slow

What enzyme increases the rate of transverse diffusion?

Flipases

What are the 3 types of membrane proteins?

- Integral - Peripheral - Lipid-linked

Describe an integral membrane protein

The portion of protein that is in contact w/ acyl tails must have hydrophobic AA side chains on the surface

If the membrane is interacting with the core of the membrane, what should the AA's on the membrane look like?

Nonpolar

Where are polar side chains most prominent?

In the loops, interacting w/ lipid head and solvent

T/F: Regular secondary structures cannot cross membranes, Why?

False, they can - They satisfy h-bond potential of polypeptide backbone

T/F: AA's that form transmembrane alpha helix are hydrophobic

True

What is the movement of proteins limited by?

Cytoskeleton

Can small, nonpolar molecules cross the lipid bilayer? How?

Yes - Simple diffusion

What 3 things does the rate of simple diffusion depend on?

- Size - Conc gradient - Lipid solubility

What size of molecules are favoured for simple diffusion?

Smaller more faster

What conc gradient favours simple diffusion?

Larger gradient increases rate

What lipid solubility favours simple diffusion?

Greater solubility increase rate

If Δ is negative, then is motion passive or active?

Passive - Spontaneous

If Δ is positive, is motion passive or active? Why?

Active - Energy must be provided to make transport

________ proteins reduce the activation energy barrier for transport

Transport

Describe porins

Contain non specific, water filled pore in center of beta barrel - trimer

Porins and ion channels enable _______ transport via membrane spanning pores

Passive

T/F: Transporter (carrier) proteins do not have membrane spanning pores

True

What does the conformational change of transporter proteins do?

Alternates the openings from one side of membrane to the other

Are carrier proteins selective?

Yes

What 3 types of transporter (carrier) proteins are there?

Symport Uniport Antiport

Primary active transport uses _________ as a source of free energy

ATP

Secondary active transport uses _______________ as a source of free energy

Ion gradient

What is the ΔG describing for primary active transport?

ΔG (rxn) < 0

What is the ΔG describing for secondary active transport?

ΔGt (ion) < 0

T/F: The Na/K ATPase is a primary active transporter Why?

True - 2 conc gradients generated across cell membrane and used as source of energy for secondary active T processes

What kind of transporter is Na/K ATPase?

Antiport

What is the ΔG for Glucose in the Na/Glucose transporter?

ΔG > 0 for glu in (Unafvourable)

What is the ΔG for Na in the Na/Glucose transporter?

ΔG < 0 (favourable)