Lipids Flashcards
What are the 2 structures that lipids can be broken down into?
fatty acids and isoprenoids
How do we name fatty acids? 2 methods.
:D^123
#= number of carbons
D= number of double bonds (db)
^123= 1st carbon of each db, counting from the acid end
OR
#= “ “
D= “ “
(omega - 3) = first carbon of first db counting from the methyl end, each subsequent db is then 3 carbons away
What are the 2 types of unsaturated fatty acids?
Cis and trans
Which form of unsaturated fats create a “bend” in the structure?
Cis
Does a bend in the structure increase or decrease membrane fluidity?
Increases
Do cis bonds allow for tighter or looser packing of phospholipids?
looser
Which type of unsaturated fats are mostly from naturally made fats?
cis
What are the 2 sources of trans fats?
1.) Some made naturally by gut bacteria of ruminants, meat.
2.) Most made commercially as a by-product of partial hydrogenation
Partially hydrogenation targets cis-bonds in fatty acids to:
A) Remove hydrogens and turn oils into solid fats
B) Remove hydrogens and turn solid fats into oils
C) Add hydrogens and turn oils into solid fats
D) Add hydrogens and turn solid fats into oils
C.) Add hydrogens and turn oils into solid fats
What is the by product of partial hydrogenation?
trans bonds
Less that how many grams per serving can be labelled as “0% trans fat”?
.5 g per serving
Where are fatty acids synthesized?
cytoplasm
Which fatty acid is usually synthesized? How many carbon?
16:0 palmitate
What are fatty acid substrates?
Acetyl CoA and malonyl CoA
Malonyl CoA is acetyl CoA with what extra group added?
CO2
With fatty acid synthase, how many fatty acid chains can be made at once?
2
What are 3 coenzymes that could be involved in FA synthesis?
B7, B5, B3
What does B7 (biotin) do in FAS?
Helps add CO2 to acetyl CoA to make malonyl CoA
What does B5 do in FAS?
Part of fatty acid synthase
Part of acetyl CoA and malonyl CoA
What does B3 do in FAS?
Reduced the FA chain
What are the steps of FA synthesis?
1.) acetyl group joins
2.) malonyl group joins
3.) acetyl and malonyl groups condense with loss of CO2
4.) O removed as water, NADPH donates H’s
5.) FA chain shifts over
If we can only make 2 FA chains at once, how do we get a 16 carbon chain?
Keep repeating steps 2-4
How do you separate the FA chain from the enzyme?
Use water to break the bond
How do you make a chain bigger than 16C? Where does this happen?
Elongate using enzymes embedded in the ER membrane. ER. Similar steps, different enzymes
How do you make odd-numbered fatty acid chains?
Start with propionyl CoA (3C) rather than acetyl CoA (2C) in step one can make odd number chains.
How do you get unsaturated FAs? (2)
1.) Made in ER: Desaturase enzymes use NAD(P)H (B3) to create double bonds
2.) Others are essential, from diet. (linoleic acid), plants
What do fatty acids support?
cardiovascular, immune, reproductive and nervous systems
What kind of fatty acid is alpha- linolenic acid?
Omega-3
What kind of fatty acid in linolenic acid?
Omega-6
What kind of il has a high level of linoleic acid?
vegetable oils
When is epinephrine released?
Sympathetic responses (flight or fight)
Synthesis is oppositely regulated to ______________.
breakdown
Glucagon promotes (beta ox / FA synthesis) and therefore (increases / decreases) FA synthesis.
beta ox
decreases
Insulin promotes (beta ox / FA synthesis) and therefore (increase / decrease) beta ox
FA synthesis, decreases
Epinephrine promotes (beta ox/FAS) and therefore decreases/increases FAS.
beta ox
decreases
What are the 3 regulators of fatty acid synthesis? And what do they do?
Glucagon and epinephrine (inhibit acetyl CoA carboxylase)
Insulin (activates acetyl CoA carboxylase)
Acetyl CoA will be inhibited by phosphorus. True or False
True
What are the 2 outcomes of the inhibition of acetyl CoA carboxylase, and the lowering of malonyl CoA
1.) decreased substrate for FA –> decreased FAS
2.) increased transport of FAs into the mitochondria –> increased beta oxidation
Triglycerides are 3 fatty acids attached to a _____________ backbone via an _____________ link.
glycerol
ester
What do FAs provide?
energy and insulation
True or False. TGs pack tighter and therefore store energy more efficienty.
TGs
Where does lipogenesis take place?
cytosol
Steps of lipogenesis
1.) Addition of 2 FAs to a glycerol backbone
2.) Make substrates (glycerol-3-phosphate backbone and 3 fatty acyl CoAs)
3.) Transfer 2 FA chains to the backbone sequentially
4.) Replace the phosphate on the backbone with the 3rd FA chain
What enzyme adds a phosphate to glycerol?
glycerol kinase
In adipose and liver, what enzyme is used to convert DHAP to glycerol-3-phosphate using what enzyme?
glycerol-3-phosphate dehydrogenase
What acts to carry the FA chains to the backbone and transfer them over from FA to fatty acyl CoA?
ATP
What do both phospholipids and glycosphingolipids both contain what 3 things?
1.) a backbone
2.) lipid
3.) head group
Phosphoglycerides contain what 2 things?
1.) glycerol backbone
2.) 2 fatty acid chains
What 2 things do sphingolipids?
1.) sphingosine backbone
2.) ceramide: sphingosine (includes a fatty chain), plus and additional FA chain
What are 3 sphingolipids?
1.) sphingomyelin
2.) cerebrosides
3.) gangliosides
What are 2 phosoholipids?
1.) phosphatidates
2.) sphingomyelin
What structures have a polar phosphate-alcohol head?
phospholipids
What structures have a carbohydrate head?
glycosphingolipids
What are the 3 major kinds of cell membrane lipids in animals?
glycolipids, phospholipids and cholesterol
Where are phospholipids synthesized?
cytosol
What 2 ways is glycerol-3-P made?
1.) Glycerol-3-phosphate is made from dihydroxyacetone phosphate (DHAP) in liver and adipose tissue.
2.) The liver can also convert glycerol into glycerol-3-phosphate.
Once you have phosphatidic acid, how do you get to other phopholipids? What is added then removed in this process? What substitution is necessary?
1.) Phosphatidic acid is dephosphorylated
2.) Additional head groups are added: Different head groups are added to the remaining diacylglycerol (DAG) backbone
3.) CMP
4.) Nucleophilic
What is the difference between the 2 phosolipid groups, glycerophospholipids and sphingomyelin?
It has a sphingosine back bone, rather than a glycerol backbone.
What is the same between the 2 phospholipid groups?
both have 2 fatty acid-like tails
What group do cerebrosides and gangliosides belong to?
sphingolipids (glycosphingolipids)
What differentiates sphingomyelin and cerebrosides/gangliosides?
sm has a phosphorous head group
c/g have carbohydrate head group
G: 1 or more sialic acid PLUS 1 or more additional monosaccharide
C: monosaccharide head group
***sulfatide if additionally sulfated
Which type of sphingolipid has a polar and nonpolar part?
Ganglioside
What is sphingolipid storage disease (spingolipidases)? Most common example?
accumulation of sphingolipids
usually fatal by 5 years old
Tay-Sachs Disease
GM2 accumulates in lysosome due to enzyme deficiency
Most severe excesses occur in brain= neural cell damage
What are eicosanoids derived from? (2)
1.) arachidonic acid (20:4)
2.) 20 C FAs
What is a common eicosanoid?
prostaglandin
What are 3 physiological functions of eicosanoids?
1.) vasodilation
2.) vasoconstriction
3.) platelet aggregation
What is a mixture FAs linked to long-chain hydrocarbon alcohols via ester bonds?
wax (the simplest FA esters)
non polar
What is an isoprene unit linked together called?
isoprene
What forms could terpenes be?
alcohol, aldehyde, ring
What is the smallest terpene? How many isoprene units?
monoterpene, 2
What is a sesqui (1.5) terpene called?
Farnescene
What is a triperpene called?
squalene
What is a tetraterpene called?
beta cartene
What is a mixed terpene?
terpene + non- terpene
ex: CoQ, vit K, farnesylated proteins
How many isoprene units make up a steroid?
6 (4 fused rings with various substituents)
What are steroids made from?
cholesterol
Cholesterol synthesis starts with 3 of what molecule, making which intermediate?
acetyl-CoA into 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA)
In cholesterol synthesis, what is the rate limiting enzyme? What does it do? What does high cholesterol do to this enzyme?
HMG-CoA reductase
catalyzes the conversion of HMG-CoA to mevalonate, a key step in the pathway. Regulation of HMG-CoA reductase is vital for maintaining cholesterol homeostasis in the body.
When cholesterol levels are elevated, it inhibits the activity of HMG-CoA reductase, thus reducing the production of cholesterol. This regulatory mechanism helps prevent excessive accumulation of cholesterol in cells.
What class of pharma drugs inhibits this enzyme?
statins
What isoprenoid is formed that is ultimately converted to the cyclic structure of cholesterol?
In the pathway of cholesterol synthesis, an isoprenoid called farnesyl pyrophosphate (FPP) is formed. FPP serves as a precursor for various molecules, including squalene. Squalene is then converted to lanosterol, which eventually leads to the formation of the cyclic structure of cholesterol.
Cholesterol synthesis
1.) 3 A-COA
2.)HMG CoA
a.) ketogenesis
b.) rate limiting step
i.) HMG-CoA reductase begins synthesis
ii.) HMG- CoA r. blocked by high cholesterol levels or statin drugs
3.) mevalonate
4.) isopentenyl pyrophosphate (isoprene units)
5.) squalene
6.) cholesterol
Where does most cholesterol synthesis occur?
liver
What does the liver do with cholesterol?
1.) make bile
2.) make lipoproteins (LDL) to carry cholesterol to the tissues –> binds on cell and taken in –> broken down inside –> chol. released
What is familial hypercholesteremia?
inherited defect in LDL-receptors (increase circulated LDL, therefore cholesterol in the blood
increase risk of myocardial infarction
What is the precursor to steroid hormones?
cholesterol
What is cholesterol first converted to, which is then converted to various other steroid hormones?
pregnenolone
What can compete with intestinal cholesterol absorption? What do they help?
plant sterols
lower LDL cholesterol levels
Cardiac glycosides are derivatives of what?
plant sterols
What does digoxin do? (cardiac glycoside)
Increase heart contractility and decrease rate
