fatty acid synthesis

where is acetyl-coA made?

in the mitochondrial matrix

where are fatty acids synthesized?

in the cytosol

in what tissue does triglyceride synthesis primarily occur?

in adipose tissue

esterification of 3 fatty acids with glycerol uses what activated intermediates?

• glycerol-3-phosphate

• fatty acyl-coAs

what happens to the newly synthesized triglycerides in the liver?

they are exported to other tissues for storage as triglycerides or for oxidation to make ATP

why do triglycerides need to be packed into lipoprotein particles for transport in blood?

because they are hydrophobic

what lipoproteins transport triglycerides?

• VLDL

• chylomicrons

what organs synthesize lipoprotein particles and which ones do they synthesize?

• small intestine: chylomicrons

• liver: VLDL

what is GPIHBP1?

binding protein that binds LPL to endothelial surface of capillary

what happens to triglycerides on the endothelial surface of capillaries?

they are broken down by lipoprotein lipase into fatty acids and glycerol

what happens to fatty acids and glycerol after being broken down?

• glycerol goes to liver for gluconeogenesis

• fatty acids cross target cell membrane

what happens to fatty acids once they are in target cells?

G3P reacts with fatty acids to synthesize triglycerides

regulation of fatty acid uptake and metabolism in fed state

• adipose tissue LPL synthesis and secretion are increased

• adipose tissue pulls fatty acids in, esterifies them to triglycerides and stores them

regulation of fatty acid uptake and metabolism in fasted state

• adipose LPL decreases for triglyceride mobilization

• muscle LPL increases

• muscle pulls fatty acids in and primarily oxidizes them for fuel

fatty acids in blood

• non-covalently bound to albumin for transport

• used for oxidation, VLDL synthesis or ketone body formation in liver

can the muscle supply other tissues with fatty acids?

no, only adipose tissue can

what type of protein is albumin?

an amphipathic protein

where does fatty acid oxidation occur and what type of oxidation happens?

in the mitochondria by β-oxidation

what form are fatty acids in when being oxidized?

activated form, attached to CoA

what happens during fatty acid oxidation?

• chain length is reduced by 2-C lengths

• acetyl CoA units are produced

• fatty acids are oxidized, FAD and NAD+ are reduced

does the oxidation of fatty acids or glucose yield more energy?

the oxidation of fatty acids

ketosis

metabolic condition arising from glucose insufficiency

how are energy demands in the body met during ketosis?

body mobilizes fat for oxidation

what happens to acetyl CoA levels during ketosis?

• concentration of acetyl CoA greatly exceeds the concentration of oxaloacetate

• TCA cycle can’t handle all of the available acetyl CoA

ketone bodies

• acetone

• acetoacetate

• BHB

where does ketosis happen?

• in the liver

• ketone bodies are metabolized by other tissues

what happens when there isn’t enough oxaloacetate?

acetyl CoA can’t enter TCA cycle and it backs up leading to ketosis

what happens when there are low levels of glucose?

• oxaloacetate is pulled out of TCA cycle to make glucose and TCA cycle slows down

• acetyl CoA builds up resulting in ketone body synthesis