12 - LIPID METABOLISM 2025

Activation of fatty acids into acyl coenzyme A (acyl-CoA) occurs mainly in this cellular compartment

Cytosol

Sequence of steps repeated in the process of lipogenesis

Condensation → Reduction → Dehydration → Reduction

Sequence of steps repeated in the process of beta-oxidation of fatty acids

Oxidation → Hydration → Oxidation → Thiolysis

Site of beta-oxidation of fatty acids

Mitochondria

Site of oxidation of very long chain fatty acids

Peroxisomes

Most common inborn error of fatty acid oxidation

Medium-chain fatty acyl CoA dehydrogenase (MCAD) deficiency

This condition occurs due to the consumption of unripe fruit of the akee tree due to the toxin hypoglycin that inactivates medium- and short-chain acyl-CoA dehydrogenase, inhibiting β-oxidation and causing hypoglycemia

Jamaican vomiting sickness

Deficiency of phytanoyl-CoA hydroxylase leading to accumulation of phytanic acid

Refsum disease

Inherited absences of peroxisomes in all tissues leads to marked accumulation of very-long-chain, saturated, unbranched fatty acids in liver and central nervous system

Zellweger syndrome

Refers to the inability to transport VLCFAs across the peroxisomal membrane leads to accumulation in the brain, adrenals, and testes

Adrenoleukodystrophy

Autosomal recessive disorder due to mutations in the CFTR gene

Cystic fibrosis

This value of sweat chloride may be used to diagnose cystic fibrosis

Sweat chloride >60 mmol/L

Products of ketogenesis

Acetoacetate, β-hydroxybutyrate, Acetone

7-dehydrocholesterol reductase deficiency leading to low plasma cholesterol and elevated 7-dehydrocholesterol

Smith-Lemli-Opitz syndrome

Most common form of congenital adrenal hyperplasia

21-alpha-hydroxylase deficiency

Refers to the autoimmune destruction of the adrenal cortex leading to adrenocortical insufficiency

Addison disease

Lipoprotein with the largest diameter, lowest density, and highest triacylglycerol content

Chylomicron

Lipoprotein with the highest cholesterol content

LDL

Lipoprotein with the highest protein content

HDL

Cofactor of lecithin : cholesterol acyltransferase, and structural component of HDL

Apolipoprotein A-1

Mediates assembly and secretion of VLDL, and structural protein of VLDL, IDL, LDL

Apolipoprotein B-100

Main apoprotein and mediates secretion of chylomicrons from small intestines

Apolipoprotein B-48

Cofactor of lipoprotein lipase

Apolipoprotein C-II

Mediates uptake of chylomicron remnants and IDLs

Apolipoprotein E