BIOSYNTHESIS OF LIPIDS

Question 1

___________ are nonpolar or weakly polar molecules that are very soluble in organic solvents like hexane (C6H14) and carbon tetrachloride (CCl4), and insoluble in a polar medium like water.

Answer 1

lipids

Question 2

___________ are the major fuel store in the body.

Answer 2

Triacylglycerols

Question 3

___________ is a rare genetic disease that causes weakness or numbness of the hands and feet (peripheral neuropathy). Due to a genetic abnormality, people with ARD disease lack the enzyme in peroxisomes that break down phytanic acid, a type of fat found in certain foods.

Answer 3

Refsum disease

Question 4

____________ IS THE MAJOR PRECURSOR FOR FATTY ACID SYNTHESIS

Answer 4

GLUCOSE

Question 5

provides the carbon for fatty acid synthesis (via acetyl
CoA) as well as the reducing equivalents (NADPH) required for this process.

Answer 5

Glucose

Question 6

______________ is defined as the synthesis of fatty acids from nonlipid precursors. It is the conversion of fatty acids and glycerol into fats, or a metabolic process through which acetyl-CoA is converted to triglyceride for storage in fat.

Answer 6

Lipogenesis

Question 7

The saturated ________, is synthesized first, and all other fatty acids are made by its modification.

Answer 7

C16 acid, palmitic acid

Question 8

Synthesis of fatty acids from acetyl CoA requires the activated intermediate, ___________, which is made by carboxylation of acetyl
CoA by acetyl-CoA carboxylase.

Answer 8

malonyl CoA

Question 9

______________ catalyzes the rate-limiting step in fatty acid synthesis.

Answer 9

dAcetyl-CoA carboxylase

Question 10

dAcetyl-CoA carboxylase exists in an inactive, protomeric state and, when activated, as linear polymers. The enzyme is activated by ____________.

Answer 10

citrate or isocitrate.

Question 11

_________ is a protein constituent of the
multienzyme complex.
It transports the growing fatty acid chain between enzyme domains of fatty acid synthase (FAS) during biosynthesis.

Answer 11

acyl carrier protein (ACP)

Question 12

The acyl product is b-ketoacyl-ACP. This intermediate is reduced to B-hydroxyacyl-ACP using ___________ as electron donor.

It is the reduced form of NADP+; used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent.

Answer 12

nicotinamide adenine dinucleotide phosphate (NADPH)

Question 13

The growing fatty acid proceeds through six more reaction cycles to produce palmitoyl-ACP, which then is
acted on by a thioesterase to produce ____________.

Answer 13

free palmitic acid

Question 14

The ________________ and __________ are both free, so that another cycle of fatty acid
synthesis can begin.

Answer 14

a. sulfhydryl groups of ACP
b. synthase

Question 15

The released product is
converted to ___________, preparing it for modification or incorporation into complex lipids.

Answer 15

palmitoyl CoA

Question 16

The principal products are
______________ and ____________, which are absorbed by the epithelial cells that line the small intestine.

Answer 16

a. 2-monoacylglycerols
b. free fatty acids

Question 17

____________ is a triacylglycerol-rich plasma lipoprotein.

Also known as ultra low-density lipoproteins, are lipoprotein particles that consist of triglycerides, phospholipids, cholesterol, and proteins. They transport dietary lipids from the intestines to other locations in the body.

Answer 17

chylomicrons

Question 18

Fatty acids are synthesized in this tissue from excess carbohydrate and amino
acids.

Answer 18

liver

Question 19

__________________ cholesterol is produced in the liver and released into the bloodstream to supply body tissues with a type of fat (triglycerides).

A second triacylglycerol rich lipoprotein.

Answer 19

very low density lipoprotein (VLDL)

Question 20

The triacylglycerols in chylomicrons and VLDL are hydrolyzed by ____________________, located on the surface of capillary endothelial cells in tissues such as adipose tissue and skeletal muscle.

Answer 20

lipoprotein lipase

Question 21

The apoprotein ________, which is found in chylomicrons and VLDL, activates the process by binding the lipoproteins to the enzyme.

Answer 21

ApoC-Il

Question 22

The products of lipoprotein lipase action are ____________ and ________.

Answer 22

a. free fatty acids
b. glycerol

Question 23

The triacylglycerols stored in adipose tissue are mobilized for use as fuel in the fasted state. This process is initiated by ______________, which is located within adipocytes.

Answer 23

hormone-sensitive lipase

Question 24

This enzyme is activated when it is phosphorylated
by _______________________.
Conversely, ________ inhibits the activity of this
enzyme by inducing its dephosphorylation

Answer 24

a. cAMP-dependent protein kinase A
b. insulin

Question 25

___________ is a lipid droplet coating protein known to regulate lipid metabolism in adipocytes by serving as a physical barrier as well as a recruitment site for lipases to the lipid droplet.

Answer 25

Perilipin

Question 26

__________ is an enzyme that synthesizes glycerol 3-phosphate from glycerol and ATP.

Answer 26

glycerol kinase

Question 27

During prolonged fasting, when much of the body’s energy is derived from stored fat, the __________ produced by the hydrolysis of triacylglycerol in adipose
tissue is an important substrate for gluconeogenesis in the liver.

Answer 27

glycerol