lecture 23 synthesis of lipids

Question 1

phosphatidate

Answer 1

GAP + 2 fatty acid chains. key molecule that is a precursor of triglycerides and phospholipids

Question 2

how and where is phosphatidate formed

Answer 2

Phosphatidate is formed by the addition of two fatty acids to glycerol 3-phosphate. their ACP groups get swapped for coA groups. synthesized in ER membrane

Question 3

what is cholesterol synthesized from

Answer 3

acetyl coA

Question 4

describe the energy used in the production of phosphatidate

Answer 4

you use the energy from the high energy thiol linkage to power the addition of the fatty acids to the GAP.

Question 5

what are the two products phosphatidate can produce

Answer 5

fats + phospholipids

Question 6

how does phosphatidate produce fats

Answer 6

lose phosphate (PAP enzyme does this.) triacylglycerol synthase then adds a third acyl chain on to it.

Question 7

how does phosphatidate produce phospholipids

Answer 7

2 different methods: can either form CDP-diacylglycerol which then reacts with an alcohol to form phospholipid. or, create CDP-alchohol by activating a phosphoalcohol with CTP, and then combining with diacylglycerol.

Question 8

how are membrane phospholipids formed

Answer 8

reaction with CTP to form CDP-alcohol.

The activated alcohol reacts with diacylglycerol to form the phospholipid.

Question 9

how are sphingolipids formed?

Answer 9

synthsized from ceramide. c16 fatty acid meets a serine. terminal hydroxyl group of ceramide is substituted to form other sphingolipids

Question 10

what are the three stages of cholesterol formation?

Answer 10

HMG reductase forms mevalonate using NADPH. mevalonate -> isoprene->squalene. squalene rolls up into cholesterol

Question 11

committed step of cholesterol formation?

Answer 11

HMG reductase forming mevalonate

Question 12

what is the Regulation of cholesterol synthesis ?

Answer 12

regulating HMG reductase; occurs via sterol regulatory element binding protein (SREBP), metabolites of mevalonate/cholesterol, and increases in cholesterol

Question 13

how is cholesterol delivered throughout the blood?

Answer 13

Cholesterol is carried in a particle that can be isolated from the blood. Particles come in different sizes and densities.

Question 14

what do chylomicrons do?

Answer 14

carry exogenous fat to skeletal muscles and liver

Question 15

what does VLDL do?

Answer 15

delivers endogenous fat synthesis in liver. lipases release fatty acids. remaining cholesterol returns to liver to process into IDL.