Chapter 11: Lipid and Amino Acid Metabolism

Question 1

Dietary fat consists mainly of ________________, with the remainder comprised of what 4 types?

Answer 1

triacylglycerols;
1. cholesterol
2. cholesteryl esters
3. phospholipids
4. free fatty acids

Question 2

Emulsification of lipids occurs in the ________________.

Answer 2

duodenum

Question 3

What aids emulsification?

Answer 3

Bile

Question 4

What happens after emulsification?

Answer 4

Intestinal cells absorb fats

Question 5

At the end of the ileum, ________ ________ are actively reabsorbed and recycled.

Answer 5

bile salts

Question 6

Digested lipids are absorbed into the mucosa and re-esterified to form triacylglycerols and cholesteryl esters and packaged, along with certain apoproteins, fat-soluble vitamins, and other lipids into ________________. These leave the intestine via ____________, the vessels of the lymphatic system, and re-enter the bloodstream via the ____________ ________.

Answer 6

chylomicrons; lacteals; thoracic duct

Question 7

Although human adipose tissue does not respond directly to glucagon, a fall in insulin levels activates a ____________-____________ ____________ that hydrolyzes triacylglycerols, yielding what 2 things?

Answer 7

hormone-sensitive lipase; fatty acids and glycerol

Question 8

While free fatty acids are transported through the blood in association with ____________, a carrier protein, triacylglycerol and cholesterol are transported in the blood as ____________.

Answer 8

albumin; lipoproteins

Question 9

Chylomicrons are highly soluble in both ____________ fluid and ________ and function in the transport of dietary triacylglycerols, cholesterol, and cholesteryl esters to other tissues.

Answer 9

lymphatic, blood

Question 10

________ metabolism is similar to that of chylomicrons; however, it is produced and assembled in liver cells. Its primary function is the transport of ____________ to other tissues.

Answer 10

VLDL - very low density lipoprotein; triacylglycerols

Question 11

Once triacylglycerol is removed from VLDL, the resulting particle is referred to as either a VLDL remnent or ________. Some of this is reabsorbed by the ________, and some is further processed in the blood stream.

Answer 11

intermediate-density lipoprotein (IDL); liver

Question 12

ALthough LDL and HDL are primarily cholesterol particles, the majority of the cholesterol measured in blood is associated with ________

Answer 12

LDL

Question 13

The normal role of LDL is to do what?

Answer 13

Deliver cholesterol to tissues for biosynthesis

Question 14

____ is synthesized in the liver and intestines and released as dense, protein-rich particles into the blood.

Answer 14

HDL

Question 15

HDL is used for what?

Answer 15

Cleaning up excess cholesterol from blood vessels for excretion

Question 16

Apolipoproteins, aka, apoproteins form what?

Answer 16

THe protein component of lipoproteins (they combine with the lipid)

Question 17

Most cells derive cholesterol from LDL or HDL, but some is synthesized de novo in the ________ and is driven by ________-________ and ________.

Answer 17

liver; acetyl-CoA, ATP

Question 18

The ____________ shuttle carries mitochondrial acetyl-CoA into the ____________, where cholesterol synthesis occurs.

Answer 18

citrate; cytoplasm

Question 19

____________ promotes cholesterol synthesis.

Answer 19

insulin

Question 20

________ ________ are long-chain carboxylic acids. The carboxyl carbon is carbon 1, and carbon 2 is referred to as the ____-________.

Answer 20

fatty acid; alpha-carbon

Question 21

When describing a fatty acid, the total number of ________ is given along with the number of ____________ ____________, written how?

Answer 21

carbons; double bonds
carbons:double bonds

Question 22

____________ fatty acids have no double bonds while ____________ fatty acids have one or more double bonds.

Answer 22

saturated; unsaturated

Question 23

Humans can synthesize only a few of ____________ fatty acids; the rest come from essential fatty acids found in the diet that are transported as chylomicrons as triacylglycerols from the intestine.

Answer 23

unsaturated

Question 24

What are the 2 important essential fatty acids? What are they used for?

Answer 24

1. alpha-linolenic acid
2. linoleic acid

Used for maintaining cell membrane fluidity

Question 25

Fatty acid biosynthesis occurs in the ________ and its products are subsequently transported to adipose tissue for storage.

Answer 25

liver

Question 26

Both of the major enzymes of fatty acid synthesis, ________-____ ____________ and ________ ________ ____________ are also stimulated by ________.

Answer 26

acetyl-CoA carboxylase, fatty acid synthase; insulin

Question 27

____________ ________ is the primary end product of fatty acid synthesis.

Answer 27

palmitic acid

Question 28

____________-________ is the product of the pyruvate dehydrogenase complex, and it couples with ____________ to form citrate at the beginning of TCA.

Answer 28

acetyl-CoA; oxaloacetate

Question 29

____________ ________________ is the rate-liming enzyme of TCA; as the cell becomes energetically satisfied, it slows TCA, which causes ____________ acccumulation.

Answer 29

isocitrate dehydrogenase; citrate

Question 30

In the cytosol, ________ ________ splits citrate back into ____________-________ and ____________.

Answer 30

citrate lyase; acetyl-CoA and oxaloacetate

Question 31

________-________ ____________ requires biotin and ATP to function, and adds ____ to acetyl-CoA to form ____________-________.

Answer 31

acetyl-CoA carboxylase; CO2, malonyl-CoA

Question 32

Fatty acid synthase is more appropriately called ____________ ____________ because palmitate is the only fatty acid that humans can synthesize de novo.

Answer 32

palmitate synthase

Question 33

____________, the storage form of fatty acids, are formed by attaching ________ fatty acids (as fatty acyl-CoA) to ____________.

Answer 33

triacylglycerols; three, glycerol

Question 34

Triacylglycerol formation from fatty acids and glycerol 3-phosphate occurs primarily in the ________.

Answer 34

liver

Question 35

What is the reverse of fatty acid syntehsis?

Answer 35

beta-oxidation

Question 36

When fatty acids are metabolized, they first become activated by attachment to ____, which is catalyzed by ________-________-________ ____________.

Answer 36

CoA; fatty-acyl-CoA synthetase

Question 37

Short-chain fatty acids get into the mitochondria how? How about long-chain fatty acids? What enzyme is used to oxidize?

Answer 37

Simple diffusion (then oxidized); long-chain are transported via carnitine shuttle with carnitine acyltransferase I as the oxidizing enzyme

Question 38

Fatty acids with an ____ number of carbon atoms undergo beta-oxidatino in the same manner, except in the final cycle, these fatty acids yield one acetyl-CoA and one ____________-CoA (from the 5-carbon remaining fragment). This CoA is converted to methylmalonyl-CoA by ____________-________ ________________.

Answer 38

odd; propionyl-CoA; propionyl-CoA carboxylase

Question 39

Methylmalonyl-CoA is then converted into ____________-________ by what enzyme?

Answer 39

succinyl-COA; methylmanlonyl-CoA mutase

Question 40

____________-____ is a TCA intermediate and can be converted into ________ to enter the gluconeogenic pathway in the cytosol.

Answer 40

succinyl-CoA; malate

Question 41

Amino acids are classified by their ability to turn into specific metabolic intermediates: ____________ amino acids can be converted into glucose through ________________; ____________ amino acids can be converted into acetyl-CoA and ketone bodies.

Answer 41

glucogenic, gluconeogenesis; ketogenic