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12 Cards in this Set

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Indicate the main sites in the body and the metabolic condition under which fatty acid de novo synthesis takes place
Liver, brain, kidney, mammaryglands, intestines and adipose tissue.

The liver synthesizes fatty acids as components of TAG when there is an excess of carboyhydrate in the date relative to lipids.
Outline the action of citrate lyase and the malic enzyme in the liver
The transfer of acetyl units from the mitochondrial pool to the cytosol during the fed state takes place via the Malate-Citrate Shuttle Mechanism.

1. Citrate Synthase condenses Acetyl-CoA with oxaoacetate to form citrate (TCA cycle) which is able to pass through the inner membrane to the cytosol.
2. Citrate crosses the mitochondrial membrane to the cytosol.
3. ATP-citrate lyase converts it to Acetyl-CoA and Oxaloacetate.
4. Malate Dehydrogenase uses a NADH to convert Oxaloacetate to Malate
5. The malic enzyme creates a NADPH in the decarboxylation of malate into pyruvate which is then able to pass through the inner membrane back to the matrix.
Explain how acetyl-CoA carboxylase synthesizes malonyl-CoA and how the reaction is regulated (short and long term)
ACCase uses ATP to caboxylate Acetyl-CoA to Malonyl-CoA in the cytosol. It is regulated by the ration of its inactive protomer to its active polymer.

1. Carboxylation of biotin to form carboxybiotin
2. Transcarboxylation of biotin
Outline the fatty acid synthetic pathway and incate the role of acyl carrier protein in the pathway.
Acetyl-CoA (C2) is carboxylated to Malonyl-CoA (C3) and Acyl Carrier Proteins (ACP) and transfered to both Acetyl-CoA and Malonyl-CoA in exchange for the CoA.

1. Acetyl-Synthase and Malonyl-CoA (C3) are condensed to acetoacetyl-ACP
2. A NADPH is used to reduce Acetoacetyl-ACP to β-hydroxybutyrl-ACP
3. β-hydroxybutyrl-ACP is dehydrated to crotonyl-ACP
4. Another NADPH is used to reducde Crotonyl-ACP to butyryl-ACP in a second reduction reaction.

This reaction is the opposite of mitochondrial β-oxidation (C2 + C3 → C4 + CO2) and is run four times to make a single Palmitic Acid.
Identify the sources of NADPH for fatty acid synthesis
Pentose Phosphate Pathway ??
Discuss malonyl-CoA inhibition of acarnitine-palmityol transferase I (CPT 1)
Malonyl-CoA, the product of fatty acid anabolism, inibits CPT1 from taking Acyl-CoA across the inner membrane and beginning mitochondrial β-oxidation, the catabolism of fatty acids.
Outline the elongation of fatty acids in humans.
1. ER (microsomal) pathway uses malonyl-CoA: Most palmitoyl-CoA is elongated to stearic acid

OR

2. Mitochondrial pathway uses acetyl-CoA: Carnitine takes the Palmitoyl-CoA into the mitochondria and it is either elongated of β-oxidized.
List the major tissues of triacylglycerol synthesis and storage
Adipocyte - lipid storage, TAG & NEFA interconversion
Blood - Transport either w/albumin or VLDLs
Hepatocyte - NEFA to Ketone Bodies or Acetyl CoA, TAG synthesis
Distinguish between the glycerol-3-P pathway and the MAG pathway for triacylglycerol synthesis
Glycerol 3-Phosphate pathway (Kennedy Pathway) - Takes place in the liver, adipose tissue and mammary glands where a series of acyltransferases add three acyl groups to a glycerol backbone.

TAG Synthesis - takes place in the intestines where acyltransferase adds two acyl groups directly to a mono-acyl group.
Outline the desaturation of fatty acids in humans.
Desaturating fatty acids is the process of adding C = C double bonds to increase membrane fluidity. Humans are unable to desaturate past the Δ9 position. All desaturases are associated with the Smooth ER.
Explain the converstion of linoleic acid to arachidonic acid and α-linolenic acid to docosahexaenoic acid.
C18:2n-6 (linoleic) is desaturated to C18:3n-6 (gamma-linolenic), elongated to C20:3n-6 and then desaturated again into C20:4n-6 (arachidonic acid)

C18:3n-3 (alpha-linolenic) is desaturated to C18:4n-3, elongated to C20:4n-3 and then desaturated again to C20:5n-3 (eicosapentaenoic EPA) before being both elongated and desaturated again into C22:6n-3 (docosahexenoic DHA)