Lipids are critical for _______, _______ and ________.
Lipids do not form...
Name the five major classes of lipids.
Free fatty acids
Lipids are considered to be ________ molecules that are __________ in organic solvents.
Water-soluble molecules that are highly soluble in organic solvents.
Fatty acids are a main source of ____ and a critical building block for ________.
Source of fuel
Building block for membrane lipids
Fatty acids are chains of hydrocarbon chains that have a ________ at one end and a ______ at the other end.
Saturated FAs contain ______. Example?
No double bonds.
Unsaturated FAs contain ______. Example?
What two factors enhance the fluidity of membranes containing these fatty acids?
Short chain length
The presence of cis double bonds
Which have a lower melting point (saturated or unsaturated)?
Double bonds are most commonly in the ____ conformation. This conformation causes ______ and ______. Which causes the melting point to be ______.
Causes kinks and more fluidity
Melting point will be lower
Which FAs are essential components of our diets because we cannot synthesize them?
Cis polyunsaturated fatty acids (Omega-3 FAs - found in fatty fish and shellfish)
Which two types of FAs have been implicated in high cholesterol and cardiovascular disease?
Saturated and trans-unsaturated fats
The [ ] of FAs in the blood is _____ because they are strong acids.
Low (A high [ ] would disrupt pH balance of cells)
3 Fatty acids esterified to one molecule of glycerol.
In mammals, the major site for triacylglycerol storage is ______.
Adipose tissue (large lipid droplet)
Triacylglycerols are ________ because they are hydrophobic and reduced.
Energy rich (Richer than carbs!)
One gram of anhydrous fat stores more than ______ the energy of a gram of hydrated glycogen (carb).
Glycogen and glucose stores provide enough energy to sustain biological function for about _______.
Triacylglycerol stores allow survival/biological function for ________.
The most common lipids in membranes are?
List the 4 components of phospholipids.
Fatty acids (2 or >)
Platform (i.e. glycerol)
Sphingomyelin is a common membrane sphingolipid that is common in...
the myelin sheath of nerve cells
Carbohydrate-containing lipids are called...
The carbohydrate components of glycolipids are on the extracellular surface of the cell membrane, where they play a role in _______.
The simplest glycolipids are called ______.
The most common steroid is _____ and it plays a role in _____________.
Cholesterol - maintaining membrane fluidity
Steroids are built on a tetracyclic platform, consisting of _____________ and a __________ fused together.
3 cyclohexane rings fused with a cyclopentane ring
Cholesterol is absent from ________ and does not exist outside of _________.
Membrane lipids are ______.
(FAs - hydrophobic)
(Phosphate/Alcohol - hydrophilic)
Failure to remove a farnesyl group from the nuclear protein lamin results in...
-Deformed nuclear membrane and impaired nuclear function
-Causes premature aging - Hutchinson-Gilford progeria syndrome HGPS
There are 8 characteristics of membranes. What are they?
Composed of lipids and proteins
Allow movement and information across membrane
The formation of membranes is powered by?
Phospholipids and glycolipids form _________ in aqueous solutions.
Ions (w/charges) cannot cross membranes because of...
The energy cost of shedding their associated water molecules (solvation shell)
Ex: sodium (Na+)
Indole is _________ than tryptophan in membranes because it is ______.
More soluble because it is uncharged.
The ability of small molecules to cross a membrane is a function of its ______.
Melting temperature is dependent on 2 things.
1.) Length of fatty acds
2.) Cis unsaturation
Function of cholesterol in animals
Helps to maintain proper membrane fluidity in membranes
-4-ring structure does not pack tightly: causes disorder
Membrane proteins allow _______ and _______ the membrane.
Transport of molecules and information cross
Membranes that serve primarily as insulation are primarily...
Membranes that must allow traffic in and out require more...
This membrane protein spans the bilayer and is embedded in the hydrocarbon core of the membrane.
Shown in yellow
This membrane protein is bound to the lipid polar head groups or exposed surfaces of other membrane proteins.
Peripheral (Disrupted by adding salts or changing pH)
Shown in blue
What is common structural feature of integral membrane proteins?
Membrane-spanning alpha helices
Aspirin inhibits __________ activity of PGH2 synthase-1 by _______________.
Cylcooxygenase by obstructing the channel (block to reduce inflammation)
Lipids laterally diffuse _____ while proteins laterally diffuse ______.
Lipids - rapidly
Proteins - at different rates (depending on attachment to other cellular/extracellular components)
What is transverse diffusion?
Flip-flopping that occurs when lipids diffuse without the assistance of enzymes (very slow)
A small molecule will cross a membrane under these two conditions:
[ ] of molecule is higher on 1 side than another
the molecule is lipophilic (soluble in nonpolar solns)
Polar molecules CAN diffuse with the assistance of what?
A channel by means of facilitated or passive transport
This occurs down a concentration gradient only
Movement of molecules against a concentration gradient requires a source of energy. This is called...
The most important active transport example is...
Na+/K+ ATPase Pump
More than ____of the ATP consumed by a resting animal cell is used to pump what?
What is digitalis?
Inhibits the Na+/K+ ATPase which affects calcium [ ] which leads to a more robust heart contraction.
ATP hydrolysis only takes place when....
Na+ and K+ are present
The Na+/K+ pump uses the energy of ATP hydrolysis to simulataneously pump ______ out of the cell and ______ into the cell against their [ ] gradients.
3 Na+ out
2 K+ in
Multidrug Resistance Protein (MDR)
Pumps drugs out of a cell - uses energy of ATP to pumpback out of the cell foreign substances
Cystic Fibrosis Transmembrane Regulator (CFTR)
Involved with Chloride channels, against concentration gradient
-Can involve just one AA change
Powers the transport of a molecule ______ its concentration gradient by coupling the mvmt to the mvmt of another molecule down its concentration gradient, with both molecules moving in the __________.
Against [ ] gradient
Moving in the same direction
Uses one concentration gradient to power the formation of another, but molecules move in _______.
Glucose is higher in or out of cell?
In the cell
Glucose is moved into some animal cells _____ the concentration gradient by symporter that is powered by Na+ ions moving _____ a concentration gradient.
Glucose - against
Na+ - down
Channels can be activated by changes in ____ (________) or by binding of specific molecules to the channels (________).
Voltage (voltage-gated channels)
What is tetrodotoxin?
Toxin produced by a puffer fish that is a lethal inhibitor of Na+ channel
Potassium ion channel aims to
Selectively and rapidly transport K+ (spontaneously it should want to leave the cell) across the cell membrane.
Potassium channel is 100x...
Better at letting K+ out than Na+ out
Smaller ions are excluded from the K+ channel because they cannot interact with the...
Selectivity filter - allows K+ to move through due to intimate bonds between the two, but excludes Na+ because it cannot form the bonds
It provides energetic compensation for it losing its water shell (more energetically favorable)
Why is the K+ channel so rapid?
Because of electrostatic interactions! It repels/provides a force to bump all others out over and over
As ions enter the channel from one side, other ions are pushed out the other side.
The K+ ion channel...
Requires K+ ions to become dehydrated to pass through
K+ ion channel does NOT closely interact with Na+ ions...
Na+ ions must stay hydrated and hence, cannot pass through the channel.
The class of lipids that does not contain fatty acids is:
Which type of lipid is not amphipathic?
Characteristics of polyunsaturated fatty acids
They contain more than one double bonds
They have an even number of carbons
The chain form is kinked
They remain in liquid form at lower temperature than saturated fatty acids
The fluid lipid bilayer can solidify and freeze at very cold temperatures. However, there are certain kinds of fish that live in very cold water (deep sea). The cell membranes of these fish are likely to have more of which of the following membrane components than would a fish that occupies warmer waters?
Phospholipids with polyunsaturated FAs
What type(s) of membrane transport requires a protein carrier, is not saturable with substrate, and requires no energy input?
Channels and pores
Which second messenger(s) is made by the inositol-phospholipid signal transduction pathway?
DAG and IP3
How is adenylyl cyclase activated at the plasma membrane?
By binding to a Gα-GTP subunit of a trimeric G protein
Which of the following are correct parts of the Membrane Fluid Mosaic Model?
Lipids and proteins are asymmetric distributed in the membrane
can dynamically move around in the membrane
T or F: Signal transduction pathways directly generate ATP
In the G-protein coupled receptor (GP/CR) signaling pathway, what is required to activate protein kinase A (PKA)?
The precursor for the synthesis of estrogen or androgen?
T or F: Lipophilic or nonpolar molecules (such as estrogen) require active transporters