lipid metabolism

Catabolism

Breakdown of molecules to generate energy.

Lipolysis

Breakdown of triacylglycerols to release fatty acids.

A series of metabolic pathways that convert carbon fuels into CO2 and H2O to generate energy

cellular respiration

Epinephrine

Hormone that stimulates lipolysis during stress.

Glucagon

Hormone that promotes energy release from stored fats.

Albumin

Protein that transports fatty acids from adipose tissue, makes blood pressure

FABPs

Proteins that facilitate fatty acid entry into muscle cells.

The lipase responsible the takes TAG-> DAG

Adipose triglyceride lipase

The lipase responsible the takes DAG--> MAG

hormone-sensitive lipase

The lipase responsible the takes MAG--> Glycerol

monoacylglycerol lipase

β-oxidation

Pathway for fatty acid degradation to acetyl CoA.

Acyl CoA

Fatty acid linked to coenzyme A for metabolism.

Site of B-oxidation in prokaryotes

cytoplasm

Site of B-oxidation in eukaryotes

muscle cells and small amnts in adipocytes

Four steps of Beta Oxidation

1. Oxidation by FAD

2. hydrolysis

3. Oxidation by NAD+

4. Thiolysis by coenzyme A

How many carbons do FA's hydrocarbon chains shorten by

2 carbons

Thiolysis

Cleavage of a compound by a sulfhydryl group.

Bringing fatty acids into the mitochondria requires activation and channels. Hows this done?

By attaching fatty acid to CoA which is catalyzed by acyl CoA synthetase.

Acy CoA crosses _ via ion channel

outer mitochondrial membrane

Carnitine

Molecule that transports acyl groups into mitochondria.

Location of 95% of carnitine in the body

skeletal muscles

Activities at the translocase channel using carnitine is the

rate-limiting step

Enzyme involved in the first step of B-oxidation(oxidation by FAD)

acyl coA deydrogenase

Product of step 1 of beta oxidation

Trans-delta^2- enoyl ocA

Enzyme involved in 2nd step of beta oxidation( hydration)

enoyl coA hydratase

Product of 2nd step of beta oxidation

I-3-hydroxyacyl coA

Enzyme involved in 3rd step of beta oxidation( oxidation by NAD+)

I-3-hydroxyacyl coA dehydrogenase

Products of step 3 of beta oxidation

3- ketoacyl coA and NADH

Enzyme invovled in step 4 of beta oxidation( thiolysis of coenzyme A)

B-ketothiolase

Products of step 4 of beta oxidation

acetyl coA and fatty acid chain two carbons shorter

T/F: both B oxidation and cellular respiration occur in the mitochondrial matrix

True

Steps 1-3 of Beta oxidation are strucurally similar to steps in TCA cycle

6-8

What happens to Aceyl coA after beta oxidation?

enters TCA cycle to make atp

What happens to NADH AND FADH2 after beta oxidation?

donate electrons to ETC

What happens to shortened FAs after beta oxidation?

continues to be metabolized via B-oxidation

Final thiolysis products for an even chain fatty acid

2 acetyl coA

Combustion of hexanoate generates ___ ATP

36

How does the metabolism of odd chain fatty acids occur?

through muscle's B-oxidatio pathway

Acyl CoA synthetase

Enzyme that activates fatty acids for metabolism.

Propionyl CoA

3-carbon product from odd-chain fatty acid metabolism.

Succinyl CoA

Intermediate that enters the citric acid cycle.

Peroxisome

Organelle for initial oxidation of very long fatty acids.

Feedback inhibition

Regulatory mechanism controlling metabolic pathway activity.

Glycerol kinase

Enzyme that phosphorylates glycerol in liver.

Glyceraldehyde 3-phosphate

Intermediate directing into glycolysis or gluconeogenesis.

Fatty acid activation

Process of linking fatty acids to CoA.

How are fatty acid chains longer than 22 carbons metabolized

sent to peroxisome where the acyl group is shortened via peroxisomal b- oxidation and is then transported to the mitochondria for regular b-oxidation

Unsaturated fatty acids require additional enzymes to shift the and of the double bonds

position and configuration

How are steps 1-3 of B-oxidation controlled

through feedback inhibition

What factors can suppress B-oxidation activity?

NADH, Acetyl-CoA, and cyoplasmic malonyl-coA

PGC-1alpha

activates transcription factors, increasing gene expression in b-oxidation

Where is glycerol sent after metabolism

sent to the liver where it is phosphorylated by glycerol kinase

What happens after glycerol is phosphorylated by glycerol kinase?

it's oxidized and isomerized into glyceraldehyde 3-phosphate which is then directed into glycolysis or gluconeogenesis