Lecture #11 - Lipid Metabolism

Question 1

Fatty Acids

Answer 1

Hydrocarbons found in the membrane of cells

De novo Fatty Acid Synthesis is done in:
1. Adipose tissue (mainly doing triglyceride storage + does a synthesis)
2. Liver (does most fatty acid synthesis)
- Fatty acids are made in the liver and transported to the adipose tissues as VLDL for storage
3. Mammary Tissues –> make de novo fatty acids to put in milk (FA are energy dense fuel for offspring)

Question 2

Insulin + Fatty Acid synthesis

Answer 2

Once insulin is released it goes to adipose tissue –> GLUT4 will go to the plasma membrane in adipocytes –> glucose (carb) goes into cell –> after bring in glucose adpocyte can turn the glucose into fatty acids

Insulin burst helps drive fatty acid synthesis by brining in the carbohydrate substrate (used for de novo fatty acid synthesis) AND is insulin has some signaling role in synthesis

Question 3

Skelatal muscle fatty Acid synthesis

Answer 3

Skelatal muscle does not do de novo fatty acid synethsis (or very little)
- Skelatal muscle uses and stores fatty acids BUT doesn’t make them

Example - Runner and obese people store fat in skeletal muscle BUT they store it in different ways
- Runners – Hold fatty acids in small lipid droplets in muscle Vs. Obese people store fatty acids in larger lipid droplets in muscle

Question 4

What do we synthesize Fatty Acids from

Answer 4

Building block for Fatty Acid biosynthesis is Carbohydrates

Eat a big meal –> Store some of the carbohydrates in glycogen –> one make all possible glycogen can turn the carbohydrates into long chain fatty acids
- Glycogen – immediate source of carbohydrates
- Store long chain fatty acids for long term in tissues (Ex. Store in adipose tissue as triglycerides)

Question 5

Distribution of macronutrients globally in lean vs. Obsese person (Fuel content in Average Vs. Obese)

Answer 5

Difference in distribution of macronutrients in lean vs. obese is the storage of adipose tissue

Have LESS adipose tissue with triglycerides in lean person than in obese person
- Difference affects the ability of people to survive in the absence of food (obese people have more triglycerides and can survive without food for longer)
- Adipose with triglycerides = good storage vessel for enabling life in the absence of food for longer

Question 6

Fatty Acid synthesis (How we make fatty acids) - Overall Reaction

Answer 6

Reaction - AcytlecoA –> Manlonyl-CoA –> Palmitic Acid –> Palmitoyl-CoA –> Palmitoleyl-CoA

Overall- Conversion of eight 2 carbon Actyl-CoAs into a 16 carbon Palmitate chain
- Fatty Acids made = storage vessel

Question 7

AcytlecoA

Answer 7

Actyl group in ActylCoA = short chain FA (2C saturated)

Thioester bond between Acytle Group and co-enzyme A is good for doing Acyl transferase reactions (easily move acyl groups between molecules)

Actycl-CoA is the building block for fatty acid syntehsis/cholestrol (Actyle-CoA is made from carbs)

Question 8

AcytlecoA –> Manlonyl-CoA

Answer 8

AcytlecoA –> Manlonyl-CoA – uses Acycle-coCA Craboxylase

Acycle-coCA Craboxylase - carboxylates ActyclCoA –> Uses Bicrobarnate to add CO2 onto Actyl-CoA to form Malnyl-CoA
- Process regertaes CO2 and Release CoA

Elongating FA to long chain fatty acids uses a reitertive process that uses MalnoylCoA as the buidling block

Rate determining step/Commitmemt step in fatty acid synthesis (Once have Malonyl-CoA reaction/using Acytl-CoA is commited to fatty acid synthesis)

Question 9

Manlonyl-CoA –> Palmitic Acid

Palmitic Acid –> Palmitoyl-CoA

Palmitoyl-CoA –> Palmitoleyl-CoA

Answer 9

Manlonyl-CoA –> Palmitic Acid – uses fatty Acid Synthase (FAS)
- Palmitic Acid is not particularly useful because it is not on CoA –> need to re-esterify it to CoA

Palmitic Acid –> Palmitoyl-CoA – uses AcylCoA synthetases
- Resterifying Palmitic Acid onto CoA = done in an ATP dependnit manner –> NOW Palmitoyl-CoA can be used for reactions
- Palmitoyl-CoA = long chain saturated fatty acid

Palmitoyl-CoA –> Palmitoleyl-CoA – uses SCD
- Can change the propterties of Palmitoyl-CoA (Ex. add double bond to d9 position) –> causes a kink in molecule

Question 10

Effect of adding double bonds to molecules

Answer 10

Making double bonds changes the membrane fluidity in plasma membrane

Different between a saturated and unsaturated fatty acid is the melting Point
- Example - Butter Vs. Oil difference in liquid Vs. Solid is mediated by saturation of the fatty acids

Question 11

Biochemical determination of the requirements for fatty acid synthesis

Answer 11

How they found the chemical process of fatty Acid synthesis/compoents that are needed

Experiment – Syntehsized long chain FA from in a cell-free environment
- Added - C14-labled Actcyle CoA + Pigeon liver homoegeonate + ATP-Mg + Citrate + NADHPH (Reducing equivilent) + Thiol groups

Question 12

In vitro reconstitution of fatty acid synthesis

Answer 12

Took liver homogenate –> Added different salts to solution –> fractionated by amonium sulfate precipiation (based on amount of salt in solution)

Results - Seperated synthesis of fatty acids in 2 different reactions:
1. Acytl-CoA Craboxylase (Acytl-CoA –> Malonyl-CoA)
- Uses ATP
2. Fatty Acid Synthase - Takes Acytle-CoA and Manoyl-CoA to make Palmitate (makes a long chain fatty Acid)
- Uses NADPH ; Release CO2 + NADP+ + Water

END - 2 main enzymes that are needed to syntehsize fatty acids

Question 13

Acytl-CoA Carboxylase

Answer 13

Overall - ACC take Actyle-CoA and adds on CO2 –> Makes malonyl-CoA (a dicrabaoxylic Acid)

Uses 2 enzymatic steps:
1. Biotin Carboxylase - Uses HCO3 (bicarbinate) toi loads CO2 group onto a Biotin carrier proteins –> THEN transcraboxylase part of enzyme
- Biotin carrier protein is linked to biotin
2. Trancraboxylase - Transfer of biotin linked CO2 (activated CO2) to Acytl-CoA to form Malonyl-CoA

ACC activities:
1 – Biotin carrier protein
2 – biotin Craboxylase
3 – transcraboxylase

Question 14

Biotin Arm of Acytl-CoA Carboxylase

Answer 14

ACC has Biotin arm is in the middle of the enzyme

Biotin Arm – allows for CO2 to be carried from one active site to the other one

Biotin arm goes from Active site with Biotin Carboxylase activity where biotin arm binds to CO2 to Active site with transcarboxylation activity to make Malnoyl-CoA
- In active site with Biotin craboxylae actovity –> Biotin Arm binds CO2 to the Biotin carrier protein
- Transcarboxylation activity – arms is used to put CO2 from the biotin containing protein to Actyl-CoA

Question 15

Removing Biotin + Avidin

Answer 15

Get Biotin from diet

Avidin (found in egg whites) –> binds tightly to biotin (Kd = 10^-15)
- Used Avidin in lab to isolate things (biotynytlate something and use strepdavidin beads to isolate them)
- Eat too much egg white prevents Biotin absorption in the gut because avidin in egg whites binds to biotin –> remove biotin from cells and get biotin deficiency
- Avidin is in Egg whites because it is antibacterial

Can manipulate the pathway by removing biotin

Question 16

Fatty Acid Synthase

Answer 16

FAS makes loing chain fatty acids by elongating Malnoyl-CoA into long chain FA

Question 17

Fatty Acid Synthase proteins/genes

Answer 17

FAS has 7 activities

Bacteria/Plants - have 7 genes that codes for 7 proteins (Each has a different activity)
- Evolution put the 7 proteins into a metabolon (type of MLO) –> as they evoloved they fused the components into 1 protein

Yeast – 2 proteins (still has all 7 activities)
Veratberets – 1 protein (still has all 7 activities)
Tranpanosome Brucei (parasite) – Makes enzyme by taking a primer and elongating it

Question 18

FAS activities

Answer 18

Overal - FAS Takes Malonyl-CoA and Actyl-CoA (primer) –> Puts together the Malonyl-CoA and Actyl-CoA –> makes Pamitic Acid (16 carbon FA)

1. Acyl carrier protein carries acyl groups in thioester linkage
2. Malonyl-CoA/acetyl-CoA transacylase transfers acyl group from CoA to Cys residue of KS
   3.ketoacyl-ACP synthase (KS) condenses acyl and malonyl group
3. Beta Ketoacyl-ACP reductase reduces beta keto group to beta hydroxy-ACP
4. beta hydroxyacyl-ACP dehydratase removes water from beta hydroxy-ACP –> creating double bond
5. Enoyl-ACP reductase reduces double bond, forming saturated acyl-ACP
6. Thioesterase cleaves the fatty acid

Question 19

Fatty Acid Syntahse - Step 1

Answer 19

Load fatty Acid Synathase enzyme with Actyl-CoA (2) and Malnoyl-CoA (3C) –> FAS makes Buyrate (short chain FA ; 4C)
- 4 carbons because 2C Actyl-CoA 2C and Malonyl-CoA 3C –> 5C-1becuase CO2 is released = 4C

Actyl-CoA is place on Cystein on a condensing enzyme (CE is part of FAS)
- CoA and Cystein on CE end with a sulfhydrol = Actyl group is easily trasnfered between the two

Malnoyl-CoA is placed onto the SH of pantotheinate group on the Acyl Carrier protein (part of FAS)

Question 20

Actyle carrier protein Vs. CoA

Answer 20

Actyle carrier protein in FAS is similar to Co-enzyme A because BOTH have a phosphopantotheinate group
- Phosphopantantotheniate group = another vitemen used for FA sythesis (analogous to biotin arm of ACC)
- Acyl carrie protein (ACP) - permit the growing fatty acid chain to reach distant catalytic sites on the fatty acid synthase

Malnoyl can attached in thioster link via terminal sulfhydral group on the phosphopantotheinate when attached to CoA or Acyl carrier protein

Question 21

Formation of Palmitate by Fatty Acid Synthase

Answer 21

1, Adding Actyl-CoA to condensing enzyme AND Malnoyl-CoA to the Acyl carrier protein (BOTH are attached to thiol on FAS)
2. Condensing enzyme domain catylyzes the condensation of Actycle- ACP (primer) with malnoyl-ACP (Elongating Unit) –> make Acetoacetyl-ACP
- CO2 from ACC reaction is lost in this step
- After condensation need to remove CoA
3. Sequential reduction of the Keto Group at C3 of Acetoacetate
- Reduction –> Dehdrayion –> reduction –> Get Butryl-ACP (BOTH reduction reactions use NADPH)
4. Tranfer of growing Acycle chain from ACP to Condesning enzyme

Question 22

If the CO2 from malnoy CoA is lost – Why use the Malonyl group (why not just condense 2 Acetyl groups)

Answer 22

Condensation of two Actyle groups is energetically unfavorable Vs. CO2 leaving malonate makes the reaction favorable
- Energy for reaction = from ATP (use in ACC)

ACC needs ATP BUT FAS does not need ATP instead FAS condensation uses the lose of CO2 as the energy that drives the reaction forward
- Invest ATP in ACC step and then utilize it in FAS by using the energy of the loss of CO2 (use ATP to add CO2 at the start)
- Add CO2 in ACC reaction using ATP and lose CO2 in FAS reaction to drive reaction foward

Question 23

Formation of Palmitate by Fatty Acid Synthase - Expense of reaction

Answer 23

Expensice of reaction – Uses 2 NADPH in Reduction –> Dehdrayion –> reduction reaction
- Reactions that use NADPH release NADP+

Need NADPH to drive the Fatty Acid synthesis forward

Question 24

Formation of Palmitate by Fatty Acid Synthase - Tranfer of growing Acycle chain from ACP to Condesning enzyme

Answer 24

Once condensed the acycl groups from Malonly-CoA and Acytl-CoA (have have a short chain saturated FA) –> do Acyl transferase reaction to transfer the chain from the Acycle carrying protein (ACP) to the condenzying enzyme

NOW ACP is open –> load a new Manoyl Co-A to the ACP

Repeat reaction until get 16 carbons -> THEN palmityl thioesterase in FAS cuts the thioester to cut the FA acyl chain off of the enzyme –> get free long chain 16 carbon saturated FA

Question 25

Acyle Chain elongation

Answer 25

Sequential rounds of acyl transfer to condensing enzyme --> malonyl transacylation --> condensation of the malonyl group with the growing acyl chain --> reduction of the resulting di-ketone result in the generation of a 16 carbon palmityl group --> cleaved from the converting enzyme by a palmityl thioesterase

Question 26

What is the chain length of every Fatty Acid in the body

Answer 26

ALL FA chains are divisible by two because have 2 Carbons in Actyl-CoA and 3 carbons in Malnoyl-CoA BUT lose Carbon when CO2 is released = 4 carbons in the building blocks YOU CAN have an odd number of Carbins in a fatty acid chain if start with Propnyl-CoA (instead Actyl-CoA) - Propanoyl CoA + Malnoyl-CoA --> get 5C (3 + 3 – 1 = 5)

Question 27

Where does Acteyl CoA come from

Answer 27

Most fatty acids we make use carbohydrates as a substrate (Use Acytl CoA that comes from carbohydrates) Pyruvate (from glycolysis) goes to the mitocnidra --> once in mitochondria pyruvate can go to different pathways: 1. Pyruvate can go to Oxoloacetate (Using Pyruvate Carboxylate) 2. Pyruvate can be oxidated and decarboxylated to Actyl-CoA (used PDH) - Actycl-CoA can used in TCA cycle to make energy

Question 28

Pyruvate --> Oxoloacetate

Answer 28

Pyruvate Carboxylate - Carboxylates Pyruvate to Oxaloacetate - PC is simikar to ACC First step in TCA – condensation of Actyl-CoA and Oxoloaceteis--> makes Citrate (Using CS) --> citrate is transported out of the mitochondria to cytosol in high energy (because inhibit Citrate dehydrogeniase --> get a build up of citrate --> citrate goes to the cytoplasm using a transporter in inner mitcondiral membrane)

Question 29

Use of Citrate in the cytoplasm

Answer 29

Make Citarte into Acytle-CoA using ATP - Citrate lyase makes Citrate --> Oxoloactete + Acytl-CoA (Uses ATP) - Released Acytl-CoA can be used in FA synthesis Recycle Oxoloactete to Pyruvate: 1. Malate deH2ase makes Oxoloacetate --> Malate 2. Malic Enzyme makes malate --> pyruvate + NADPH - NADPH made can be used for FA synthesis - MINOR pathway for making reducing equivilents (NADPH) OVERALL - Citrate --> OAA --> Malate --> Pyruvate

Question 30

Where does most NADPH come from

Answer 30

Most reducing equivalents (NADPH) comes from the pentose phosphate pathway (PPP) - Rate limiting reaction of PPP – gives 2 NADPH Cells with a lot of de novo fatty acid synthesis have a lot of PPP activity Link between fatty acid synthesis to carbon metabolism - Carbon metabolism drives the PPP --> PPP makes reducing equivalents --> reducing equivalents drive fatty acid synthesis - ALSO pyruvate from carb metabolism leads to Actyl-CoA (carbon substrate for FA synthesis)

Question 31

Short term Regulation of Fatty Acid Biosynthesis

Answer 31

1. Regulate the amount of carbs that are taken up by cells using insulin dependent activation of carb uptake in cells 2. Citrate transporter is feedback inhibited by fatty Acyl-CoAs - More Actyl-CoA --> citrate won’t be transpotered = making less NADPH = have less fatty acid synthesis 3. Actyl-CoA carboxylase - primary site of control

Question 32

Regulation of Actyl-CoA carboxylase

Answer 32

1. Citrate – Serves as a feed forward allosteric activation (More citrate = More ACC activity) - Need citrate for ACC to work 2. Phosphorylation inactives ACC using Uses cAMP dependent kinase and 5’AMP activated kinase (most regulation happens using phosphorylation of AMP kinase) 3. Fatty Acyl CoAs – Feedback inhibition 4. Actyl CoA – required for polymer assembly and therefore enzymatic activity

Question 33

Regulation of ACC by phosphorylation

Answer 33

Phosphorylation inactives ACC using Uses cAMP dependent kinase and 5’AMP activated kinase (AMP activated kinase = activated by AMP ; inhibited by ATP) Energy charge of cell decrease (AMP/ATP ratio increases) -->of 5’AMP activated protein kinase is activated --> phosphyltaes and inactivates ACC - Don't want to make FA in low energy because want to use carbs to make ATP (not store carbs) = inactivate ACC = inactive FA synthesis Insulin stimulated phosphatase reverses the inactivation (when have insulin want to be able to make fatty acids to store the sugars)

Question 34

Long Term regulation of Fatty Acid biosynthesis

Answer 34

Nutritional regulates the synthesis of enzymes involved in fatty acid synthesis in a direction that makes sense Chart – Shows different regulation under different settings - Fasting state (Low glucose) - Not synthesizing fatty Acids --> decrease in Fatty Acid synthesis enzymes (FAS+ ATP-Citrate Lyase + ACC ; AND decrease DeH2ase + Malic enzymes that make NADPH for FA synthesis) - Refeed – Want use carbohydrates from food and make long chain fatty acids for long term storgae of nuetrients --> increase in ALL FA synthesis enzymes

Question 35

Changes that we can make to Palmitate

Answer 35

Might want to make Fatty acids that are longer than 16 carbonds or make unsaturated fatty acids (add double bond) - Changing properties of fatty acids Example of fatty acids with different properties - Part of Caribou leg that is in the snow has different composition of fatty acids than the part of leg that is not in the snow - Fatty acids have different saturation and different chain lengths because need different fluidity in different temperatures

Question 36

Making fatty acids longer than 16 carbons

Answer 36

Once make a 16 carbon long FA can elongate it 2 carbons at a time Enzymes at the cyosolic face of the ER can add one or more 2-carbon units to Palmitate or other unsaturaed fatty acids (makes FA longer than 16 carbons) - Uses Malanoyl coA as the 2-carbon unit donor - Don’t want the chain to get too long because long chains can disrupt the membrane

Question 37

To make unsaturated fatty acids (add in double bond)

Answer 37

Desaturases can add a cis-double bind into fatty Acyl CoA chains - Desaturases are on the ER - Destauraes use a version of an ETC – ETC will transfer electrons from NADH and the fatty acid to oxygen --> transferring the electrons --> result in water and unsaturated fatty acid Have a limited ability to make double bonds (Mostly add double bonds at the delta 9 position in fatty acids)

Question 38

Nomenclature of fatty acids

Answer 38

Omega fatty acids – Usually count the double bond position from the carboxyl end - Example – delta 9 --> carbon 9 has the double bond (Sterol-CoA desaturase desaturates the delta 9 bind into a mono unstrated FA by adding a double bond to the 9th position In omega fatty acids delta 9 is the last bond that can be desaturated - There are desaturases that can destaruate until position 10 --> then can’t made a double bond in 10-18 - IF want a fatty acid with a double bond after carbon 10 --> need to eat it in diet

Question 39

Polyunsaturated Fatty Acids beyond delta9

Answer 39

FA with double bonds after delta 9 can’t be made --> To get fatty acids with double bond after delta 9 need to --> derive from essential fatty acids (Ex. Linoleate and Linolenate) - Essential fatty acids = have to be consumed in diet - Linoleate and Linolenate are essential FA (precursors for many long-chain polyunsaturated fatty acids like Arachidnate)

Question 40

Signaling properties of Long chain fatty acids

Answer 40

Can make different signlaing lipids from long chain fatty acids (Long fatty acid chains can be important for signaling) Example – Can make Arachidoate from Linoleate --> Arachidoate is important for making prostaglandins

Question 41

Making omega 3/omega 6 fatty acids

Answer 41

We don’t have the enzyme to make omega 3 or omega 6 fatty acids or DHA (Example - Linoleate and Linolenate) --> need to ingest them - DHA = elongated Linelaic Acid (DHA = polyunsaturated fatty acid with 4 double bonds) - Get omega 3/omega 6 fatty acids and DHA from fish Fish from sea - Will have omega 3 fatty acids and DHA BUT also has mercury - Microorganism that fish eat have the desaturase enzymes to make omega 3 fatty acids Fish from farm - Salmon are fed soy and corn so have no omega 3 fatty acids/DHA but have no mercury

Question 42

What happens after make fatty acids

Answer 42

Once make the fatty acids + modified them + took in some from diet --> NOW want to store them Store fatty acids as triglycerol - Triglycerol = glycerol with 3 fatty acid chains (FA are attached via ester bond to OH in glycerol) Building block of triglycerides is NOT glycerol and fatty acids INSTEAD Glycero-3-phosphate is the building block of triglycerides - Don't use glycerol because glycerol BUT this is soluble and will be released from the cell --> need to trap the glycerol in the cell by adding phosphate (makes Glycerol-3-Phosphate)

Question 43

How do you make Glycerol-3-Phosphate

Answer 43

1. Glycerol kinase (Glycerol --> Glycerol-3-Phosphate) (ONLY in the liver) - Liver has of glycerol kinase because want to trap glycerol and utilize for glucoegensis as substarte 2. Glycerol-3-phsphate dehydrogenase makes Dihyderoxyacetone phosphate (DHAP) --> Glycerol-3-Phosphate - In liver or Adipose tissue - HERE get Glycerol-3-phosphate through glycolysis because DHAP is a glycolytic intermediate - Adipose tissue --> couples glycolysis and fatty acid synthesis because uses DHAP (glycolytic intermdieate) to make Glycerol-3-phosphate (can only use DHAP because adipose does not have Glycerol kinase)

Question 44

Why doesn't adipose tissue have glycerol kinase

Answer 44

No glycerol kinase in the adipocyte because Apdiose want to get rid of glycerol so don’t want glycsorol kianse that would trap the glycerol in the adipocute because then glycerol cant go to the liver

Question 45

Why is FA storage (making triglycerides) and Glycolysis coupled

Answer 45

Because during starvation you want to hydrolyze triglycerides and give glycerol to the liver (don’t wnat to recapture the glycerol in adipose tissue) In stravation --> change glycolysis --> chnage in gkycolsisys would cause the glycerol to not be phosphorylated (because would have less glycolysis and would have less of the glycolytic interemate) NOW won’t phosphorylate glycerol so it won’t be trapped in adipose cells and can be sent to the liver)

Question 46

Conversion of Fatty Acyl CoA to phophatidic acid

Answer 46

To make Acyl-CoA --> Phosphatidic Acid: Glycerol-3-phosphate backbone --> esterify 2 fatty acids (Acyl-CoA) onto glycerol-3-phoshate --> makes phosphatdic acid - Phosphatic acid – has 2 Acyl chains and a phosphate group To make the triglyceride – phosphatic acid phosphatase removes the terminal phosphate from Phosphatic Acid --> Get Free OH on Phosphatic acid --> Free OH on Phosphatic can be esterified to a fatty acid --> NOW have Diacylglycerol - Mutaions in phosphatic acid phosphatase - can’t make triglycerode from of fatty acids Once have Diacylglycrol --> esterify another fatty acid --> make triacylglycrol (type of triglyceride) - Triglycerol goes to VLDL partcile (liver) OR a Fat droplet (Adipose)

Question 47

2nd Path for Phosphatidic Acid

Answer 47

Can put the phosphatidic acid into the kenndey pathway --> makes glycerol phospholipids - Precursor to membrane phospholipids is phosphatadic acid (ultimately glycerol-3-phosphate) In kennedey pathway - make a head group to add onto Phosphatidc Acid (Ex. inosiltol, serine, choline) --> put the phospholipid in the membrane - Overall: Phosphatidc acid --> glycerophospholipid --> goes to cell membrane

Question 48

Review of Fatty Acid synthesis

Answer 48

In the fed state - taking excess carbohydtrates to make fatty acids for long term storage Took Glucose --> Actyl-CoA --> Citrate in TCA --> exported citrate into cytoplasm – make more Actyla CoA --> Took Actyla CoA craboxylate to Mlanoyl –COA (chain elongation unit to make long chain FA) --> elingated or detatsurated --> esterified onto glycerol-3-phoshate to make triglyceride

Question 49

Fatty Acids in Starving state

Answer 49

In starving - need to take energy and utilize it (NOW breaking down fatty acids) NOTE - Fatty acid synthesis is in the cytoplasm ; Fatty Acid oxidation is the mitocondrial matrix

Question 50

First step in fatty acid oxidation (Breakdown of fatty acids)

Answer 50

To do FA oxidation - Fatty Acids need to be transported from cytoplasm to the mitcondria (because FA synthesis is in the cytoplasm ; FA oxidation is the mitocondrial matrix) - Transport of fatty acids = Comitment step that is regulated for fatty acid breakdown Overall - Carnitine Palmityle Transferases mediated transport of Palmityle-CoA to the mitochondria - Palmitoyl-CoA = made at the end of FA sythesis

Question 51

Transporting Palmitoyl-CoA

Answer 51

All co-A molecules don’t have a trasnporter (Ex. Can't transport ActylCoA into mitochondria) --> need to biotrasform Palmitoyl-CoA - To get rid of CoA from Palmitoyl-CoA – add an amino acid (replaces CoA) Reaction - Carnitine Palmityle Transferases (CPT-1) takes Acyl-CoA off of Palmitoyl-CoA – puts on Actyl group onto Carnitine --> get Acyle Carnitine - Concentration of Acyl Carnitine is used as rate setting step for transprot of FA into the mitochondria Once have Acytle Carntine --> transporter in the mitocondria membrane transports the Acytle Cartine from the cytoplasm to the matrx of the mitocondria

Question 52

What happens to Acyl Carnatine when it enters the mitocondria

Answer 52

In mitocondira – Acylt-Carnitine is re-estrified onto Co enzyme A --> NOW beta oxidation machinery can access the fatty acid

Question 53

Regulation of fatty acid oxidation

Answer 53

FA oxidation is regulated by limiting access of the fatty to the fatty acid oxidation machinery - Carnitine Palmityle Transferases 1 (CPT1) = key regulator site of fatty acid oxidation CPT1 – inhibited by malonyl-CoA - MEANS that the rate determining step of fatty acid syntehsis (making Malnoil-CoA) inhibits the rate determining step of fatting acid oxidation (transport of Palmotoil CoA into the mitochondria) - Makes sure FA oxidation and syntheres don't happen at the same time ACC is regulated by energy charge = link of energy of the cell to oxidation of fatty acids (link through the generation of Malnoyl CoA)

Question 54

Why does the muscle have ACC

Answer 54

Muscle has Acyle-CoA Carboxylase (ACC) BUT muscle does not have de novo fatty acid synthesis - WHY does muscle have ACC - ANSWER - to make Malnoyl-CoA to regulate CPT-1 Muscle ACC is attached to the outer mitochondria membrane --> ACC makes malnoyl-CoA (nearby the CPT-1) --> Malnoyl-CoA can regulate CPT-1

Question 55

Why can't FA oxidation and Synthesis happen at the same time

Answer 55

Oxidation and Synthesis can't happen at the same time because enzyme that is made in fatty acid synthesis inhibits the ability to do fatty acid oxidation - Can’t break down FA chains while making them because the product that is made during fatty acid syntehsis is inhibiting the degredation of fatty acids by inhibiting CPT-1 NOTE - Acyl Carnitine is used to understand in born errors of fatty acid oxidation

Question 56

Fatty Acid Oxidation Pathway

Answer 56

Steps: 1. Palmitoil-CoA --> Enoyl-CoA (acyl-CoA dehydrgenase) --> 2. Enoyl-CoA --> Beta hydroxy Acyl-CoA (Enoly-coA hydratase) --> 3. Beta hydroxy Acyl-CoA --> beta Ketocyl CoA (Beta hydroxyacyl-CoA dehydrogenase) --> 4, Beta Ketocyl CoA --> Acytle-CoA and Acyl-CoA (Acyl-CoA acytltransferase) Fatty Acid oxidation extractes energy from a molecule (energy made = FADH2 and NADH --> can be used to make ATP in ETC) - FA synthesis uses NADPH - NADPH is used for FA synthesis ; NADH and FADH2 are are used as energy substrates

Question 57

Fatty Acid Oxidation - Process

Answer 57

Oxidation takes the 16 carbon chain and make 8 Actycle CoA (2C) - Extract 1 Actyl CoA at a time from the carbxyl end of the chain - For each turn of beta oxidation cycle - get Actyl-CoA + FADH2 + NADH Families of Actyl-CoA dehydrgenases - have dehydrigenases for Long, Medium, Short Acyl CoA fatty acids (ALL are expressed in the mitochondrial matrix) - Mutaton in short chain enzyme = get a little energy because can shorten the chain a little (less sevre phenotype) Vs. mutation in long chain don’t get any shorting at all (more severe phenotype) Only have different dehdygenases ; rest of the enzymes in oxidation would work for all lengths of fatty acids

Question 58

Fatty Acid degredation Vs. Synthesis

Answer 58

Fatty acid oxidation is very similar to fatty acid synthesis but in reverse (using different enzymes) First step - Fatty Acid oxidation – have Oxidation treacton Vs. Fatty Acid synthsis have reduction reaction Second step - Fatty Acid oxidation have Hydation Vs. Fatty Acid synthesis have dehyration

Question 59

Fate of Actyl-CoA in heart muscle

Answer 59

Heart has 1 job --> extract as much ATP out of food to facilitate contraction Fatty Acid oxidation in cardiac tissue shorterns fatty Acid chain to get Acytl-CoA --> Take the Acytl-CoA and put in the TCA cycle --> make H2O and CO2 AND ATP - When put Actyl-CoA in the TCA cycle --> can etract more energy from it

Question 60

Fate of Actyl-CoA in Liver

Answer 60

NOT putting Acytl-CoA into TCA INSTEAD makes the Fatty Acid carbons from Acyetl CoA into ketone bodies - Gets rid of Acytle-CoA and makes ketone bodies

Question 61

Liver making Ketone bodies

Answer 61

Condense 2 Actyl-CoA to make Acetoacetate (ketone body) Acetoacteates (not stable in the blood) --> Acetoacteates are reduced to beta-hydroxybutarate (stable and higher energy density) - Beta-hydroxybutarate can be used as an energy substrate in the brain and muscle (alternative oxidative substarte) Process ALSO makes Acetone - If someone is in keto Acidosis their breath can smell fruity because they have a lot of ketones (Including Acetones)

Question 62

Effect of making Ketone bodies on Co enzyme A

Answer 62

Making ketone bodies recycles Co-enzyme A If break down long chain and make 8 Actyl CoA --> would run out of out Co-enzyme A to put Acytle groups onto Solution - In higher energy the liver wants to get rid of carbons (Acyl-CoA) and reycle Co-enzyme A - Recycling Co-Enzyme A allows the body to continue oxidizing fatty acids (have Co-enzyme A to keep putting acyle groups on when they come off of the long chain Fatty Acid)

Question 63

Use of ketones by extrahepatic tissues - What does Beta-hydroxybutarate do in target tissues

Answer 63

In target tissue --> can use beta-hydroxybutarate to generate NADH and make 2 Actyl-CoA - Put Acty-CoA into TCA cycyle --> extract more energy To make Actyl-CoA from beta-hydroxybutarate - need to activate Acetoactatate to Acetoactly-CoA by making Succinly-CoA to Succinate using Beta-ketacyl-CoA transferase - Liver does not have Beta-ketacyl-CoA transferase

Question 64

Why does liver not have Beta-ketacyl-CoA transferase

Answer 64

Liver does not want to use the ketone bodies it is making INSTEAD it wants to give substrates to other tissues SO it does not have Beta-ketacyl-CoA transferase that is used for the reactivation of ketone bodies Liver does not have the enzyme that is used to be able to use the ketone bodies because it does not want to use the ketone bodies it wants to give them to other tissues

Question 65

Use of ketone bodies

Answer 65

Ketone bodies can be used as signaling molecules

Question 66

Ketone bodies as signaling molecules

Answer 66

Example – give niacin as a drug to treat dyspilidemia - Niacin binds to GPCR on Adipocytes --> inhibits lipolyis (niacin is a dislipodemic drig) - Beta-hydroxy butarate is a ligand for the same GPCR niacin binds to = Beta-hydroxybutarate can block lipolysis When hydrolyze triglycerides from adipose tissue --> triglycerides go to liver --> liver makes the fatty acids into ketone bodies --> ketone bodies talk back to the adipocyte because beta hydrxyburate binds to GPCR on Adipoctye --> regulates lipolysis and amount of ketones - Circut between adipocyte lipolysis and ketongensis in the liver

Question 67

What is happening during starvation - Review

Answer 67

In stravtion – hydrolyze triglycerides into its compoents (Fatty Acids and Glycerol) Fatty go to and are oxidized in liver --> FA oxidation is used to drive gluconeogenesis in liver - Fatty acids are not providing the carbon skelatons for gluconeogensis INSTEAD they provide the fuel to drive reaction ; carbons come from amino acids Glcyerol – can be transferred into glycolysis as a gluconeogentic substarte - Glycerol was stored as triglycerides in adipose during stravtion (I THINK)

Question 68

Main issue with inborn error with fatty acid oxidation

Answer 68

1. Build-up of lipid droplets 2. Short term issue in fasting --> once run out of glycogen they die because not breaking long chain FA (cant promote gluconeogensis) - Not breaking Fatty acids (not breaking triglycerol) --> not getting glycerol to liver --> not getting gluconeogensis or ketone bodies - SOLUTION (helps because have defect in gluconeogensis) - Manage blood glcuose by giving polymers of glucose (give starch before bed) --> digest it slowly and maintain blood glucose NOTE - There are neutral lipid storage disease – have fatty liver

Question 69

Lipid droplets in neuron

Answer 69

Don’t store lipid droplets in nueorns because neurons have a constative hydrolase NO lipid droplets = Not storing energy – why they need to extract it from circulation