Lipids And Membranes 2 Flashcards
Recall that we learnt that lipids are non polar and don’t dissolve in water if they have more then 6C, meaning 7C or above are unsoluable in water. So what are the three structures that lipids or glycerophospholipids make in the water solution?
They can form three structures
1-micelle
2-bilayer
3- vesicle/liposome cell
Compare and contrast between the three forms.
MICELLE. BILAYER. VESCICLES
Shape of individual unit Wedge shaped. Cylindrical with two FA tails. Cylindrical with two FA tails
Size of cross section. CS of head > side chain. =. =
Draw the glycerophospholipids with the different heads
We will now talk about a brief history of glycerophospholipids. Which category do you think glycerophospholipids fall under
Phospholipase
Diving deep into the structure of glycerophospholipids , how many parts does this lipid consists pf ?
4
2 FA chain -A1 and A2
A phosphate group- C
A small head- D
Explain how phospholipases play a role in the body
Phosphotidylinositol 4,5 bisohosphate ——> diacylglycerol + 145 inositol triphosphate
Both are secondary messenger- regulate enzyme activity
Arachidonic acid , is a omega 6 Fatty acid, released by A2- precursor to thromboxanes,, prostaglandins, leukoteriens -inflammation, fever, pain , repro
Draw the phophotidylinositol 4 5 bisohosphate , diacylglycerol, inositol 1 4 5 triphosphate
Sphingolipid are derived from
Sphingosine
Draw the structure of sphingosin
Recall recently , we talked about the function of phospholipase, compare the functions of both membrane lipid
BOTH PLAY AN IMPORTANT ROLE IN MEMBRANES
Glycerophospholipids
Phosphate group acts as a ligand
Regulate fever, inflammation, pain and reproduction
Sphingolipid
Imp to mem of plants and animals
Brain and PNS
How many parts does sphingolipids have ?
3
Sphingosine
Fatty acid
Head group
Describe the bonds between the 3 parts?
Sphingosine —amide bond— fatty acid = ceramide
Sphingosine attached to head group by Oxygen/ester bond
Draw the general structure of sphingolipid
What are the three classes of ceramide. And what is the difference between these 3 types?
Only the head molecule differs
Sphingomyelin
Glycosphingolipids
Gangliosides
Draw the sphingomyelin and phosphatidylcholine
Compare between sphingomyelin and phosphatidylcholine
Similarities
No charge
Both have phosphate and choline
Phosphodiester bond
Differences btw sphingomyelin and phosphatidylcholine
- sphingomyelin has an amine group
-sphingomyelin has an amide bond instead of ester bond - sm has only 2 alcohol groups
-sm has an embedded hydrocarbon chain (part of sphingosine) - sm has only 1 Fatty acid tail attached by amide bond
- sm has a trans double bond in the embedded hydrocarbon chain
PHOSPHOTIDYLCHOLINE
-pc has no amine group
-pc has ester bonds
-pc has 3OH groups
-pc doesnt have an embedded hc chain but has the phosphate as a part of glycerol
-pc has two FA tails
-pc doesn’t have any double bond embedded in the general structure, there may or may not be double bond in the fa tails
-the fa tails differ for both
What head does a Glycosphingolipids has?
Sugar head molecule and neutral
What are the two types of Glycosphingolipids?
1- cerebrosides - the head molecule is made of only one sugar unit
2- globosides-the head molecule has more then 1 sugar unit
Functions of Glycosphingolipids
On the surface of PM - cell cell recognition
On the surface of RBC - ANTIGENS - determines the blood group
What head molecule does a ganglioside have ?
It is complex
- charge
Head molecule - oligosacharide (similar to Glycosphingolipids)
What is the ovligosacharide in ganglioside made of ?
Residues of N acetylneuraminic acid and a sialic acid at the termini
Compare and contrast between Glycosphingolipids and ganglioside
Both have sugar units as head molecules
Glyco has no charge
Gang has - charge and is complex
Compare and contrast between sphingomyelin and Glycosphingolipids
Both have no charge
Sp have a choline head molecule and phosphate attached through a phosphodiester bond
Glyco and gang have glycosidic bonds and sugar units as head molecules
Earlier we discussed the functions of Glycosphingolipids, what is the function of ganglioside
It is negatively charged - limit transport through plasma membrane
May help in ion movement by transmembrane potential
(Same can be applied to other negatively charged groups )
Sialic acid is found on surface of resp cells and may help protect against resp viruses
Name the main components in our body that is made of lipids
Vitamins
Coenzymes
Steroids
Name the 3 types of vitamins
Vit D3
Vit E
Vit K
Vit D3 aLso know as..
Cholecalciferol
How are Vit D3 formed
Formed by skin by uV induced photochemical rxns on 7- dehydrocholestrol
Functions and deficiency.
Regulate the ca level in kidneys, intestines and bones
Ca needed for exocytosis, muscle contraction and bones formation
Can cause rickets - week bones
Vit E are also called..
They are a closely related family of lipids called tocopherols
They are compounds with substituted aromatic rings and isprenoid chains
Functions and deficiencies
Acts as biological antioxidants - the oxygen radicals on aromatic rings prevents non enzymatic oxidation of lipids as this changes the structure of lipids.
Deff causes sterility and muscle weakness
Vit k
They are closely related family of lipids with different unsaturated chains attached to napthoquinone
Function and deff of vk
Acts as co factor for blood clotting
Deff- causes the inability to form prothrombin, a precursor required for blood clotting
What are the two types of co enzymes
1- ubiquinone or coenzyme Q
2-plastoquinone
Ubiquinone and plastoquinone
U is an e carrier
Two carbonyl grouos get oxidizes giving e to complex 3 and 2
They are hydrophobic therefore can travel through membrane
P- hydrophobic and can transport through membrane
Why are there a variety of rhodopsin
So that we can cover the range of light energies
B- Wavelength max =440
G- Wmax = 530
Y- Wmax = 570
Rhodopsin subunit
1 alpha
1 beta
What are the two types of proteins in the phospholipid bilayer
1- peripheral
2- integral
What are the three types pf integral membrane proteins?
Transverse membrane - single alpha helix
Transverse membrane -4,12 a helixes
8-16 B strands form a giant B barrel(porins)
Why can some molecules go past the phospholipid bilayer membrane and some cant ?
Non polar readily dissolve in bilayer- hydrophobic
Small can easily pass
And if water and o2 required energy to pass, they are fundamental and we need a lot of them and would need lot of biomolecules and energy to let them pass.
Examples of molecules that can pass
O2, ch4,h2o, n2
Which cant pass the membrane?
Charged and small
Uncharge and large eg glucose
How can the molecules go inside the cell , if they cant directly pass through the membrane?
Pump- AT
Carries/channel proteins-PT
Carrier proteinstypes
1- uniteansport - transport 1 type of molecule in one direction
2-co transport- transport of 2 molecules
Symport - in same direction
Antiport- different direction
What type of transport is FACILITATED TRANSPORT
Passive trnsport
Describe facilitated transport
The molecules use the carriers/channel/permease/transporter proteins
To move from high concentration to low concentration gradient untill eq reached
Moving dow the gradient lowers activation energy
Therfeore no atp/energy req
What are the examples of facilitated transportation
Glucose permeate
Chloride bicarbonate
About glucose permease
Transports glucose
From outside to inside only
12 a helixes and multi span protein
50000 faster then simple diffusion
Describe how one molecule of glucose can transport into the cell
Through glucose permease in RBC
One glucose molecule binds to the transporter
Changes conformation
Opens inside
Release
Release changes conformation back to normal
Explain chloride bicarbonate facilitated diffusion.
So these are on RBC
Co2 enters repiring tissues, co2( less soluble in blood) —-> hco2- (more soluble)
Hco2- leaves the cell, and 1 cl- comes in to maintain membrane potential
The hco2 enters the lungs, cl- leaves the lungs, converted to co2
What is active transport and what are the two types?
The movement of ions up the concentration gradient
Primry active transport
Secondary active transport
What is primary active transport
The transport is directly coupled by an exergonic reaction eg ATP—>ADp
What is secondary active transport?
An ionic gradient is set by active transport , the ion going down the conc grad , providing energy to transport another molecule against its conc grad
Give an example of primary transport
Na k ATPas
Gove example of secondary transport
Glucose transport into the epithelial cells
Lactose uptake in ecoli
Explain how Na+ k+ Atpase pump works
High conc of Na inside
High conc of K outside
Atpase pumps 3Na outside
Pumps 2k into the cell
Causing a transmembrane gradient, + outside
Cotransport , antitransport
Explain the glucose intake in epithelial cells
Ionic gradient of na + made using the atpase pump. Na moves out of the cell (low to high affinity)
Gradient of glucose by uniport, glucose goes out of the cell , (high to low)
The na moves down it con gradient
Provides energy to co transport (symport) glucose againt its conc gradient
Lactose uptake in e coli
H+ pump pumps h+ outside the cell (fuel turned to co2)
H+ comes in via latose transporter (down conc gradient) provides energy and moves lactose into the celll (against conc gradient)
What are ion channels or voltage gatted channels?
Any channels that open or close due to the rapid change in transmembrane gradient caused by stimulus
Function of atpase
Mainstanins the cells resting membrane potential
Help build gradoent for the transportation of other molecules
Function of ion channels
Signal excitation
Transport of signals along the neurons
Muscle contraction
Describe how ion channel works?
K+ wither hydrating water molecules
Water filled vestibule causes hydration of k+
Backbone carbonyl oxygen form cage that fits k+ precisely
Helix dipole stabilizes k+
Alternating k+ sites occupied
