Oxidative Metabolism of Lipids In Liver and Muscle Flashcards

Comprehensive practice flashcards covering lipid structure, digestion, cellular transport, beta-oxidation enzymatic steps, and ketogenesis based on the lecture notes.

Beta-oxidation

The entirely oxidative catabolism of fats that serves as a major source of energy in liver and muscle.

Triglycerides

The storage and transport form of fats in the body.

Trans fatty acids

Fatty acids that have the effect of extending the molecule into a linear shape similar to saturated fatty acids.

Cis form

A fatty acid orientation resulting in folding back and kinking of the molecule into a U-like orientation.

Myristic acid

A saturated fatty acid with a $14:0$ notation found in coconut and palm nut oils, as well as most animal and plant fats.

Palmitic acid

A saturated fatty acid with a $16:0$ notation found in animal and plant fats.

Stearic acid

A saturated fatty acid with an $18:0$ notation found in animal fats and some plant fats.

Arachidic acid

A saturated fatty acid with a $20:0$ notation commonly found in peanut oil.

Lignoceric acid

A saturated fatty acid with a $24:0$ notation found in most natural fats and peanut oil.

Palmitoleic acid

An unsaturated fatty acid with a $16:1$ notation found in marine animal oils and small amounts in plant/animal fats.

Oleic acid

An unsaturated fatty acid with an $18:1$ notation found in plant and animal fats.

Linoleic acid

An unsaturated fatty acid with an $18:2$ notation found in corn, safflower, soybean, and cottonseed oils.

alpha-linolenic acid

An unsaturated fatty acid with an $18:3$ notation found in linseed, soybean, and other seed oils.

Arachidonic acid

An unsaturated fatty acid with a $20:4$ notation found in animal fats as a phospholipid component.

Eicosapentaenoic acid

An unsaturated fatty acid with a $20:5$ notation found in marine algae and fish that consume them.

Docosahexaenoic acid

An unsaturated fatty acid with a $22:6$ notation found in marine algae and fish.

Lingual lipase

An enzyme produced in the salivary glands that cleaves some fatty acids in the mouth.

Gastric lipase

An enzyme produced in the stomach that initiates additional digestion of triacylglycerols and diacylglycerols.

Bile

A secretion used in the small intestine for Phase I (emulsification) of fat digestion.

Pancreatic lipase

An enzyme produced in the pancreas that cleaves fatty acids in the small intestine to yield monoacylglycerols and fatty acids.

Micellar particles

Formations made of lipids and bile salts in the small intestine lumen that are acted upon by intestinal and pancreatic enzymes.

Chylomicron

A lipoprotein particle formed in the enterocyte from reformed lipids and apo-B48 that enters the lymph by exocytosis.

Enterocyte

The cell type where glycerol, glucose, cholesterol, and long-chain fatty acids are absorbed from the intestinal lumen.

alpha-GP (alpha-glycerolphosphate)

A compound formed from glucose by glycolysis or glycerol conversion in the enterocyte used to reform triglycerides.

Acyl-CoA synthetase

Also known as fatty acid thiokinase, this enzyme activates fatty acids to a CoASH derivative at the outer mitochondrial membrane.

Carnitine

A trimethyl-lysine derivative made from lysine and SAMe that facilitates the transport of long-chain fatty acids into the mitochondria.

CPT-1 (carnitine palmitoyl transferase-1)

The enzyme located on the outer mitochondrial membrane that transfers long-chain fatty acids to carnitine.

CPT-2

The enzyme in the mitochondrial matrix that recycles carnitine and releases fatty acyl CoA for beta-oxidation.

Carnitine acyl carnitine translocase

The transporter that moves acyl carnitine into the mitochondrial matrix and carnitine out into the intermembrane space.

SAMe (S-adenosylmethionine)

A molecule required for carnitine synthesis that necessitates Magnesium, Methionine, and $B_{6}$.

VLCFA (Very long chain fatty acids)

Fatty acids with $\geq 22$ carbons that are broken down into short-chain fatty acids in peroxisomes.

LCFA (Long chain fatty acids)

Fatty acids with $14-20$ carbons that are metabolized in the mitochondria via the carnitine cycle.

SCFA/MCFA

Short and medium chain fatty acids ($2-12$ carbons) that are metabolized in the mitochondria via free diffusion.

Peroxisomes

The cellular site where very long chain fatty acids are initially processed.

Hormone sensitive lipase (HSL)

The enzyme responsible for releasing fatty acids from adipose tissue, requiring glucagon, epinephrine, and normal thyroid level ($T_{3}$).

T3 (Triiodothyronine)

The active thyroid hormone level required for HSL activity; its conversion from $T_{4}$ requires bile acids.

Albumin

A blood protein that transports free fatty acids, capable of carrying $6$ to $8$ fatty acids.

Acyl CoA dehydrogenase

The first step of beta-oxidation that requires $FAD$ and produces a double bond next to the acetyl CoA group.

Enoyl CoA hydratase

The second step of beta-oxidation that requires $H_{2}O$ and produces an $OH$ group next to the acetyl CoA group.

Hydroxyacyl CoA dehydrogenase

The third step of beta-oxidation that requires $NAD^{+}$ and produces a ketone group next to the acetyl CoA group.

Thiolase

The fourth step of beta-oxidation that requires $CoASH$ and results in a fatty acyl CoA ($n-2$ carbons) and an acetyl CoA.

Acyl adenylate intermediate

The intermediate structure formed during the activation of fatty acids using $ATP$ before the addition of $CoA$.

Palmitate ATP yield

A net total of $106\,ATP$ calculated as ($80\,ATP$ from acetyl CoA oxidation + $28\,ATP$ from carbon cleavage - $2\,ATP$ for activation).

318 ATP

The total energy produced from the three fatty acids released from one triglyceride molecule ($106\,ATP \times 3$).

Glucose ATP yield

Approximately $38\,ATP$ in total, making it the preferred source of cellular energy despite lower yield than palmitate.

Acetyl CoA

A two-carbon end product of beta-oxidation; palmitic acid ($16\,C$) produces $8$ of these.

FADH2

An electron carrier produced during beta-oxidation; palmitic acid ($16\,C$) produces $7$ of these.

NADH + H+

An electron carrier produced during beta-oxidation; palmitic acid ($16\,C$) yields $7$ of these.

Propionyl-CoA

A three-carbon product resulting from the oxidation of odd-chain fatty acids like oleic acid.

Methylmalonyl-CoA mutase

A $B_{12}$-dependent enzyme that converts Methylmalonyl-CoA into Succinyl-CoA.

Succinyl-CoA

An intermediate of the TCA cycle produced from the metabolism of propionyl-CoA.

Ketogenesis

The process in the liver during fasting or starvation where excess acetyl CoA is converted into ketone bodies.

Acetoacetate

A four-carbon ketone body produced during ketogenesis from acetoacetyl CoA.

Beta-hydroxybutyrate

A four-carbon ketone body formed from acetoacetate; this reaction requires $NADH$.

Acetone

A three-carbon ketone body formed via the non-enzymatic decarboxylation of acetoacetate.

HMG CoA synthase

An enzyme required for the formation of 3-hydroxy-3-methyl-glutaryl CoA during ketogenesis.

HMG CoA lyase

The enzyme that cleaves HMG CoA to produce acetoacetate and acetyl CoA.

Ketosis

A metabolic state that happens when fats are used as the primary fuel source; it is distinct from ketoacidosis.

Glucagon

A hormone active during fasting and starvation that stimulates the release of fatty acids from adipose tissue.

Epinephrine

A hormone involved in the stress response (hypoglycemic) that activates lipolysis.