Ch 24 Bio Exam 4 Flashcards
A transport system called the ______ carries fatty acids into the mitochondria from the cytosol.
______ catalyzes the transfer of a fatty acyl group to the hydroxyl group of carnitine to produce fatty acyl carnitine.
- carnitine shuttle
- Carnitine acyltransferase
Fatty acyl carnitine then passes through the inner mitochondrial membrane into the matrix.
Fatty acids in the cytosol are transported through the inner mitochondrial membrane to ______ in the matrix.
- undergo β oxidation
Bile salts break fat globules into smaller particles called ______ in the small intestine.
- micelles
Pancreatic lipases ______ ester bonds to form monoacylglycerols and fatty acids, which recombine in the intestinal lining.
- hydrolyze
phospholipids and proteins coat the fats, forming ______, which are transported to the cells of heart, muscle, and adipose tissues.
- chylomicrons
Lipases hydrolyze triacylglycerols, forming _____ and free fatty acids, which are oxidized to acetyl CoA molecules for ATP synthesis.
- glycerol
- the process of fat utilization is stimulated.
- the hormones glucagon and epinephrine are secreted into the bloodstream, where they bind to receptors on the membrane of adipose tissue.
- a hormone-sensitive lipase within the fat cells catalyzes the hydrolysis of triacylglycerols to glycerol and free fatty acids.
- glycerol and fatty acids diffuse into the bloodstream and bind with plasma proteins to be transported to the tissues, muscles, and fat cells.
- When blood glucose is depleted and glycogen stores are low,
- adds a phosphate from ATP to form glycerol-3-phosphate.
- undergoes oxidation of the —OH group to dihydroxyacetone phosphate.
- becomes an intermediate in glycolysis and gluconeogenesis.
Glycerol from fat digestion
What helps add a phosphate group to Glycerol?
What helps oxidize Glycerol -3-phosphate to Dihydroxyacetone phosphate?
- Glycerol kinase
- Glycerol-3-phosphate dehydrogenase
How is glycerol utilized?
- Glycerol adds a phosphate and is oxidized to an intermediate of the glycolysis and gluconeogenesis pathways.
- a fatty acid is combined with CoA to yield a high-energy fatty acyl CoA.
- energy is released by the hydrolysis of ATP to AMP and used to drive the reaction.
- Fatty acid activation
A large amount of energy is obtained when fatty acids undergo oxidation in the mitochondria to acetyl CoA.
________, which removes two-carbon segments containing the alpha and beta carbon from the of the fatty acid.
- beta oxidation (β oxidation)
- carboxyl end
After the fatty acyl carnitine is transferred by the carnitine shuttle into the mitochondria matrix what does carnitine acyltransferase do?
- catalyzes the reverse reaction that transfers the fatty acyl group to CoA to reform fatty acyl CoA.
- releases the carnitine and returns to the cytosol.
What is produced in reaction one of beta oxidation?
- trans-Enoyl CoA and FADH2
- acyl CoA dehydrogenase catalyzes the transfer of hydrogen atoms from the α and β carbons of the activated fatty acid.
- a trans C = C bond is formed between α and β carbons, and the reduced coenzyme FADH2 is produced.
- a hydration reaction catalyzed by enoyl CoA hydratase adds the components of water to the trans double bond.
- a hydroxyl group (—OH) attaches to the β carbon of the fatty acid, and a hydrogen atom attaches to the α carbon.
- beta-oxidation reaction 2
- the secondary hydroxyl group on the β carbon (carbon 3) is oxidized by 3-hydroxyacyl CoA dehydrogenase to yield a ketone.
- the hydrogen atoms removed in the oxidation are transferred to NAD+ to yield a β keto or 3-keto group and the reduced coenzyme NADH.
- beta-oxidation reaction 3
- the Cα — Cβ bond is cleaved by β-ketoacyl CoA thiolase to yield a two-carbon acetyl CoA and a new fatty acyl CoA that is shortened by two carbon atoms.
- the shorter fatty acyl CoA repeats the four steps of the β- oxidation cycle until the original fatty acid is completely degraded to two-carbon units of acetyl CoA.
- beta-oxidation reaction 4
Odd-numbered fatty acids go through the same four steps of β oxidation until the final cycle, in which the remaining fatty acyl CoA is cleaved to yield a_____ group and an acetyl CoA.
- propionyl CoA (C3)
For one cycle of beta-oxidation how many molecules of NADH, FADH, and acetyl CoA are produced and where are they produced?
- 1 FADH in reaction 1
- 1 NADH in reaction 2
- Acetyl CoA in reaction 4
Some fats from our diets contain unsaturated fatty acids, which have one or more cis double bonds.
An isomerase converts a cis double bond to a trans double bond between the ______ so the fatty acid can undergo hydration. It forms a product that enters β oxidation at reaction 2, so the energy released by the β oxidation of an unsaturated fatty acid is slightly less because no _____ is produced in that cycle.
- α and β carbons
- FADH2
How many ATP does it take to activate Fatty acid beta-oxidation?
- 2 ATP
____ is a protoxin that is metabolized to become an inhibitor of acyl CoA dehydrogenase, the first enzyme in the b oxidation pathway.
- Hypoglycin A
If carbohydrates are not available
fatty acids break down to meet energy needs.
acetyl CoA molecules combine to form ketone bodies.
Where do high levels of acetyl CoA accumulate?
- Liver
acetyl CoA molecules combine in a pathway known as ketogenesis to form compounds called ketone bodies.
During reaction 1 of ketogenesis ( condensation), what do two molecules of acetyl CoA combine to form?
- Acetoacetyl CoA
this condensation is in the opposite direction of the last step of β oxidation
- in cases of diabetes, diets high in fat, and starvation.
- as ketone bodies accumulate.
- when acidic ketone bodies lower blood pH below 7.4 (acidosis).
- Ketosis occurs
Hydrolysis reaction 2 of ketogenesis:
Acetoacetyl CoA undergoes hydrolysis to form what?
- Acetoacetate
______ can undergo either a hydrogenation or a decarboxylation (reactions 3 and 4) to produce other ketone bodies.
- Acetoacetate
Acetoacetate is reduced by 2H from NADH + H+ to _____, which is considered a ketone body even though it does not contain a keto group.
- β-hydroxybutyrate
Reaction 3
Acetoacetate can also undergo ____ to yield acetone, a ketone body, and CO2.
- decarboxylation
Reaction 4
where does lipogenesis occur?
- In the cytosol
Lipogenesis occurs in the cytosol using the reduced coenzyme _____ instead of occurring in the mitochondria, where oxidation takes place using FAD and NAD+.
- NADPH
What activates the Acyl compounds for fatty acid synthesis?
- acyl carrier protein
