Lipid Metabolism Flashcards
What are lipids?
- group of molecules that are insoluble in water
What is the principle functions of lipids in the body?
- stored energy
What structural aspect in the body do lipids primarily contribute towards?
- biological membranes
How do lipids help with digestion in the GIT?
- act as an emulsifying agent
Do lipids that are stored as energy have positive or negative charge?
- neutral charge
Do membrane bound lipids contain a positive or negative charge?
- both - hydrophobic and hydrophilic
- negative in middle, positive on outside
What is the basic structure of a glycerophospholipids?
- glycerol backbone
- 2 fatty acids
- 1 phosphate attached to alcohol group
What is the basic structure of a sphingolipids?
- glycerol backbone
- 1 fatty acids
- 1 mono or oligosaccharide
What is the basic structure of a galactolipids?
- glycerol backbone
- 2 fatty acids
- 1 mono or oligosaccharide attached to a sulphate group
If a lipid is saturated what does this mean when thinking about the carbons?
- carbons have full compliment of H+
Are saturated or unsaturated lipids provide more flexibility to membranes?
- unsaturated
- due to kind in their tails
Unsaturated lipids have a double bond between 2 carbon molecules, what does this mean for the structure of the carbons?
- gives the tail of the lipids a kink
- makes the membrane it is part of more flexible
Are saturated and unsaturated more likely to be solutions or solids?
- saturated = solid and a ⬆️ melting point (butter)
- unsaturated = liquid and a ⬇️ melting point (olive oil)
What are the 2 major pathways of triglyceride metabolism?
- B oxidation = releaseing energy
- Synthesis = S for storing energy
Why is B oxidation called B oxidation?
- removal of electrons
- occurs prior to beta carbon
What is the first step of B oxidation?
- fatty acids are activated by coenzyme A
- coenzyme A attaches to fatty acid
In the mitochondria where do fatty acids become activated by the coenzyme A attaching to it?
- cytosol
What is an acyl group?
- carbon attached to O with double bond
- R tail is the fatty acid
What is the carnitine shuttle?
- exchange between CoA and carnitine groups
- facilitates acyl groups from cytosol to matrix of mitochondria
How does the carnitine shuttle move acyl across the inner mitochondrial membrane?
- acyl-CoA is converted into acyl-carnitine
- enzyme carnitine palmitoyl 1 cleaves CoA from fatty acid
- leaving Carnatine attached to fatty acid
- THIS IS THE RATE LIMITING STEP OF CARNATINE SHUTTLE
Once inside the matrix how does the carnitine shuttle keep acyl groups inside the matrix?
- acyl-carnitine is converted back into acyl-CoA
- enzyme carnitine palmitoyl 2 cleaves carnatine from fatty acid
- leaving CoA attached to fatty acid
What is the carnitine palmitoyl transferase I?
- enzyme
- converts acyl-CoA into acyl-carnitine
What is the carnitine palmitoyl transferase II?
- enzyme
- converts acyl-carnitine into acyl-CoA
What is the rate limiting step in B oxidation?
- carnitine shuttle
- exchange of acyl-CoA to acyl-carnatine
What is step 3 of B oxidation?
- multiple oxidation steps
- 2 carbon units removed each time
- 1 FADH2 and 1 NADH are formed per cycle
During each B oxidation cycle how many acetyl-CoA, FADH1 and NADH are formed?
- acetyl-CoA = 1 can then enter the cirtic acid cycle
- FADH1 = 1 = 1 can then enter the TCA
- NADH = 1 = 1 can then enter the TCA
Once the 2 carbon units have been oxidised from long fatty acid chains what cycle does it enter within the matrix of the mitochondria?
- Kreb Cycle also know as the citric acid cycle
If there are mutations in the enzymes responsible for B oxidation, what can this cause in infants (SIDS)?
- sudden infant death syndrome
- cannot use lipids as energy
If a fatty acid has a long tail, how do you calculate how many cycles of B oxidation it needs to go through?
- total number of carbons in tail divide by 2
- then subtract 1
What does a hydrase enzyme do to a molecule?
- adds H2O to a molecule
- like hydrating it
What is dehydrase enzyme?
- removes H+
- like dehydrating it
What is fatty acid synthesis?
- fatty acids are stored as adipose tissue
What are the 2 primary sites where fatty acid synthesis takes place?
- liver
- adipose tissue
Where does fatty acid synthesis take place?
- cytosol of mitochondria
In order for fatty acid synthesis to occur acetyl CoA is needed, but it is within the matrix of the mitochondria. How is acetyl CoA removed from the mitochondrial matrix to facilitate fatty acid syntheis?
- oxaloacetate (OAA) and acetyl-CoA (AcCoA) are converted into citrate
- the enzyme citrate synthase facilitates this