Lecture 19.2

What chemical keeps lipids soluble during digestion?

Bile

Lipoprotein

a protein contains a core is of neutral lipids including TAGS and cholesterol esters

• surrounding the core is a layer of phospholipids in which varying proportion of proteins and cholesterol are embedded

Lipids in diet are transported by

chylomicrons (digestion)

Fatty acids from storage in adipose tissue are transported by

serum albumin (mobilization)

TAGs synthesized in the liver are transported by

VLDLs (synthesis)

LDL

transport of endogenous lipids (cholesterol) to tissues (receptor mediated)

HDL

transport of lipids and cholesterol from cells in the vasculature to liver

VLDLs and LDL are

atherogenic ( beginning of atherosclerosis)

HDL

anti-atherogenic (good cholesterol)

Acetyl CoA can be converted to

• fatty acids

• amino acids

• ketone bodies

TAG storage is regulated by

Insulin and Glucagon

• high levels of insulin stimulate TAG synthesis

Storage (synthesis) of TAGS

Step 1: glycolysis produces DHAP then Glycerol-3-Phosphate

Step 2: Transfer FA from CoA to G-3-P (occurs in adipocytes)

DHAP

one point where lipid metabolism and carbohydrate metabolism are linked

Mobilization (hydrolysis) of TAGs

• low insulin levels and high glucagon levels stimulate triacylglycerol lipase in adipocytes.

Fates of Fatty Acids in the Cell

1. Activation of FA by the addition of CoA: Energy cost = 2ATPs

2. Binds to carnitine for transport5 into mitochondria matrix via a pore formed by large enzyme complex.

3. Oxidation of FA with even number of carbons to acetyl (beta-oxidation of Fatty Acids)

Fatty Acid Spiral

1. Introduction of a double bond

2. H20 is added to the double bond producing an alcohol

3. The alcohol is oxidized to a ketone

4. A c-c bond is broken

Beta-oxidation of fatty acids is a _____ pathway

spiral

Energy from Fatty from Fatty Acid Oxidation

Step 1: activate the FA and trap it in the cell by adding CoA - 2ATP

Step 2: the activated FA will go through FA spiral

Step 3: acetyl CoAs enter the TCA cycle

Step 4: reduced coenzymes enter the ETC

Fatty Acid Oxidation

• occurs in the mitochondria

• enzymes different from synthesis

• intermediates carried by coenzyme A

• coenzymes FAD, NAD+

• carbon atoms removed two at a time

Fatty Acid Synthesis

• occurs in cytosol

• enzymes different from oxidation

• intermediates carried by acyl carrier protein

• coenzyme": NADPH

• carbon atoms added two at a time

Ketone bodies

compounds produced in the liver that can be used as fuel in muscle and brain tissue (3-hydroxybutyrate, acetoacetate, acetone)

Ketogenesis

the synthesis of ketone bodied from acetyl-SCoA

• 3 ketones produced

Ketoacidosis

results from increased concentration of ketone bodies i the blood

• blood pH drops

• labored breathing

• increased urination

• dehydration

• depression

• coma death