lipid metabolism

define lipids

• water-insoluble organic molecules

what are the different forms lipids can exist in?

1. triacylglycerols

2. fatty acids

3. phospholipids

4. steroids

5. glycolipids

which is the storage form of lipids?

a) fatty acids

b) phospholipids

c) triacylglycerols

d) glycolipids

c) triacylglycerols

which form of lipids is “free”?

a) fatty acids

b) phospholipids

c) triacylglycerols

d) glycolipids

a) fatty acids

• not coupled with ester

what are the different functions of lipids?

• energy storage

• constituents of membranes

• anchors for membrane proteins

• cofactors for enzymes

• signaling molecules

• pigments

• detergents

• transporters

• antioxidants

dietary lipids are broken down by ____

• lipases

what are the three types of lipases? what are they categorized by?

1. lingual lipase

2. gastric lipase

3. pancreatic lipase

• separated by location (oral, stomach, pancreatic)

emulsification of lipids by bile salts occurs in the ____

• duodenum

micelles

• allow lipids to be absorbable + be transported

  • core = hydrophobic

  • surrounding = hydrophiliic

SATA: anabolism of fatty acids require:

a) acetyl-CoA

b) malonyl-CoA

c) NADH

d) NADPH

e) FAD+

f) FADH₂

a) acetyl-CoA

b) malonyl-CoA

d) NADPH

SATA: catabolism of fatty acids produces:

a) acetyl-CoA

b) malonyl-CoA

c) NADH

d) NADPH

e) FAD+

f) FADH₂

a) acetyl-CoA

c) NADH

f) FADH₂

catabolism of fatty acids takes place in the ______. Anabolism in animals takes place in the ______. Anabolism in plants takes place in the ______.

• mitochondria

• cytosol

• chloroplast

cholesteryl ester is hydrolyzed to produce _____

• cholesterol

triacylglycerols w/ pancreatic lipase produce…

• 2-monoacylglycerol + 2 fatty acids

T/F: Fatty Acid Synthase I (FAS I) is used in plants and bacteria

• false

  • FAS I = vertebrates + fungi

  • FAS II = plants + bacteria

what amino acid residue is found in Fatty Acid Synthase?

a) S

b) C

c) Q

d) T

b) C

Acyl Carrier Protein contains what vitamin B molecule/acid?

• pantothenic acid

  • also in acyl-CoA

FAS I uses 2 enzyme bound ____ groups as activating groups

• thiol

explain the prep step

1. acetate fragment of acetyl-CoA is transferred to ACP

   • acetyl CoA-ACP acetyltransferase

2. ACP passes acetate to the Cys-SH of the KS domain of FAS I

   • beta-ketoacyl-ACP synthase (KS) domain

3. ACP-SH group is recharged with malonyl from malonyl-CoA

   • malonyl CoA-ACP transferase

what action does acetyl CoA-ACP acetyltransferase perform?

• moves the acetate fragment of acetyl-CoA to ACP

what action does beta-ketoacyl-ACP synthase (KS) domain perform?

• moves the acetate to the CYS-SH of the KS domain of FAS I

• ACP-SH = open

what action does malonyl CoA-ACP transferase perform?

• ACP-SH group is recharged with malonyl from malonyl-COA

what enzyme is used in the first step of fatty acid synthesis?

a) acetyl CoA-ACP acetyltransferase

b) beta-ketoacyl-ACP reductase

c) enoyl-ACP reductase

d) beta-ketoacyl-ACP synthase

e) beta-hydroxyacyl-ACP dehydratase

d) beta-ketoacyl-ACP synthase

what enzyme is used in the second step of fatty acid synthesis?

a) acetyl CoA-ACP acetyltransferase

b) beta-ketoacyl-ACP reductase

c) enoyl-ACP reductase

d) beta-ketoacyl-ACP synthase

e) beta-hydroxyacyl-ACP dehydratase

b) beta-ketoacyl-ACP reductase

what enzyme is used in the third step of fatty acid synthesis?

a) acetyl CoA-ACP acetyltransferase

b) beta-ketoacyl-ACP reductase

c) enoyl-ACP reductase

d) beta-ketoacyl-ACP synthase

e) beta-hydroxyacyl-ACP dehydratase

e) beta-hydroxyacyl-ACP dehydratase

what enzyme is used in the fourth step of fatty acid synthesis?

a) acetyl CoA-ACP acetyltransferase

b) beta-ketoacyl-ACP reductase

c) enoyl-ACP reductase

d) beta-ketoacyl-ACP synthase

e) beta-hydroxyacyl-ACP dehydratase

c) enoyl-ACP reductase

what type of reaction is the first step of fatty acid synthesis?

• condensation

what type of reaction is the second step of fatty acid synthesis?

• reduction

what type of reaction is the third step of fatty acid synthesis?

• dehydration

what type of reaction is the fourth step of fatty acid synthesis?

• reduction

describe the first step of fatty acid synthesis (what is the product? type of reaction? enzyme?)

• condensation reaction → decarboxylation of malonyl-CoA

• malonyl group attacks acetyl carbonyl → beta-ketoacyl intermediate = acetoacetyl-ACP

  • beta-ketoacyl-ACP synthase

describe the second step of fatty acid synthesis (what is the product? type of reaction? enzyme?)

• NADPH reduces beta-keto intermediate → alcohol = beta-hydroxybutyryl-ACP

  • NADPH = oxidized → NADP+

• beta-ketoacyl-ACP reductase (KR)

describe the third step of fatty acid synthesis (what is the product? type of reaction? enzyme?)

• dehydration

• OH + H are eliminated → double bond = trans-D²-butenoyl-ACP

  • beta-hydroxyacyl-ACP dehydratase

describe the fourth step of fatty acid synthesis (what is the product? type of reaction? enzyme?)

• reduction #2

  • NADPH reduces double bond → saturated alkane = butyryl-ACP

  • enoyl-ACP reductase (ER)

the final result of FA synthesis increases the chain length of the acyl group of the fatty acid by _____

• 2 carbons

after step 4, what can happen?

• if a longer chain is wanted, the chain will be given to CYS-SH

• ACP can get a new malonyl CoA → repeat steps