Lipid metabolism

Question 1

What are two essential fatty acids?

Answer 1

Alpha-linolenic and linoleic

Question 2

Name three precursors for fatty acid synthesis

Answer 2

Acetyl coA (which is found in the mitochondria and transported to the cytoplasm). 
Acetyl coA+ 7 Malonyl coA + 4 NADH -->palmitic acid

Question 3

Name two enzyme complexes involved in FA synthesis

Answer 3

Acetyl coA carboxylase: catalyzes Acetyl coA to Malonyl coA (rate limiting)

Fatty Acid synthase- which catalyzes combining acetyl coA with malonyl coA to form palmitic acid

Question 4

How is FA acid synthesis regulated?

Answer 4

• Hormones and diet.
• phosphorylation and dephosphorylation of acetyl carboxylase
• malonyl coA inhibits FA oxidation

Question 5

How are FA chains elongated?

Answer 5

same way as fatty acid synthesis. Add 2Cs per cycle. Desaturase aids in desaturation in the ER by adding double bonds

Question 6

Where and when are TAGs made?

Answer 6

in the well fed state in the liver and the intestines

Question 7

Where and when are FAs synthesized?

Answer 7

Everywhere except RBCs. In the cytosol. Well fed state.

Question 8

Discuss the role of biotin in metabolism and its function in FA synthesis.

Answer 8

biotin bound to acetyl coA carboxylase carboxybiotin transfers carboxyl group to acetyl coA to form malonyl coA.

Question 9

Discuss the overview of FA metablism

Answer 9

Fat is converted to glycerol (which goes to the liver to be converted to glucose) and Free FAs (bound to albumin). Free FAs go the the liver to be made into energy and to ketone bodies. The brain uses ketone bodies for energy. Free FAs also go to muscle to be converted to energy.

Question 10

When and how are fats metabolized from adipose?

Answer 10

In the fasting state. TAGs are broken down to FFAs in adipocytes. glycerol goes to liver for gluconeogensis and FFA are converted in the muscle and liver to acetyl coA and undergo beta oxidation.

Question 11

What do hormone sensitive lipase and perilipin do?

Answer 11

HSL catalyzes TAG->DAG->MAG reactions. Perilipin activates HSL.

Question 12

What are adipokines?

Answer 12

Type of cytokine-related to inflammation and metabolic diseases. Made by adipocytes and macrophages. E.g. leptin.

Question 13

How do FAs get into the mitochondria from the cytoplasm?

Answer 13

FA converted to acetyl coA+carnitine in cytolsol. becomes acyl carnitine, transported through CPT1 on outer mito membrane and through translocase on inner membrane. Acyl carnitine converted back to acyl coA+carnitine in mito matrix by CPTII. CPT=carnitine palmitoyl transferanse.

Question 14

Describe beta oxidation.

Answer 14

palmitoyl coA+ 7coA+7FAD +7NAD+7H2O–>7FADH2 +7 NADH+8acetyl coA. Oxidation of C16:0 results in 28 ATP from beta ox and 80 ATP from krebs cycle (from NADH and FADH2) Total 108 ATP.

Question 15

What are three ketone bodies? When and how are they made?

Answer 15

acetoacetate, beta-hydroxylbutyrate, and acetone (waste product). Made during the fasting state in the liver. beta ox-> acetyl coA–>acetoacetylcoA–> HMG coA –>acetoacetate –> beta hydroxybutyrate

Question 16

How are ketone bodies utilized?

Answer 16

the skeletal muscle, heart, and brain oxidize ketone bodies to acetyl coA, which goes to krebs cycle to produce ATP

Question 17

Describe the events during starvation or in untreated diabetes when ketone bodies are used.

Answer 17

Ketoacidosis occurs because in untreated diabetes, the body doesn’t have enough insulin. Cells can’t take up glucose and compensates by oxidizing fatty acids and producing ketone bodies, which increases acidity in the blood.