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#lipid storage

2 public questions tagged with this topic.

Glycolipid and Phospholipid

Which statement about lipid droplets is correct?

Lipid droplets defy classic bilayer vesicle definition possessing neutral core surrounded by monolayer explaining unique buoyancy density microscopy appearance. Emergence begins when DGAT1 DGAT2 synthesize triacylglycerol DAG acyl CoA ACAT1 ACAT2 forms cholesteryl ester accumulating between ER leaflets forming oil lens twenty to sixty nanometers growing via Ostwald ripening coalescence regulated Seipin LDAF1 perilipin recruitment. Lens buds toward cytosol coated phospholipid monolayer enriched PC PE lyso PC preventing coalescence decorated perilipin family PLIN1 five CIDE proteins Seipin Rab18 regulating lipolysis contacts mitochondria peroxisomes for beta oxidation fatty acid exchange energy provision. Function storing energy five kilocalories per gram sequestering toxic free fatty acids cholesterol preventing lipotoxic ER stress unfolded protein response providing precursors membrane synthesis eicosanoids prostaglandins. Mobilization ATGL PNPLA2 HSL LIPA lipases and lipophagy via Rab7 LC3 autophagy. They contain hundreds associated proteins contrary protein free notion and do not produce ATP via oxidative phosphorylation which occurs mitochondria matrix. Understanding monolayer architecture explains why droplets float density gradients expand obesity metabolic syndrome nonalcoholic fatty liver disease pathology and diabetes insulin resistance cellular metabolism context for biomedical exams.

Ref: Walther TC & Farese RV, Annu Rev Biochem 2012, Lipid droplets neutral lipid storage monolayer organization and functions.

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Cell Organelles

Which plastid stores lipids?

Plastid diversity reflects differentiation of proplastids in meristems according to tissue identity and developmental signals regulated by light, hormones and transcription factors. Elaioplasts are specialized non-photosynthetic leucoplasts lacking chlorophyll that function in lipid storage and metabolism crucial for reproduction. They are abundant in oil seeds like Brassica, citrus exocarp oil glands, and anther tapetum where lipid reserves for pollen coat tryphine formation and pollinator attraction are needed. Ultrastructurally they contain numerous electron-dense plastoglobuli and oil droplets bounded by single inner envelope, with few internal thylakoids and extensive physical connections to endoplasmic reticulum for fatty acid trafficking via touching domains. They possess complete enzymes for fatty acid synthesis, including acetyl-CoA carboxylase, fatty acid synthase complex, and stearoyl-ACP desaturase, converting imported photosynthate like sucrose-derived pyruvate into triacylglycerols and sterol esters stored as osmiophilic globules. In contrast amyloplasts accumulate starch via ADP-glucose pyrophosphorylase, proteinoplasts store proteins in crystalline protein bodies, and chromoplasts accumulate carotenoids for coloration, illustrating functional specialization supporting plant physiology.

Ref: Wise & Hoober, The Structure and Function of Plastids, Chapter 9: Classification of Leucoplasts and Elaioplasts.

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