Biosynthesis and Storage of Fatty Acids

A complete set of vocabulary flashcards covering the biosynthesis, regulation, elongation, desaturation, and storage of fatty acids, as well as adipocyte types and hormonal regulation.

De novo synthesis

The process of creating new fatty acids from excess intake of refined carbohydrates or protein, occurring in the liver, kidney, mammary gland, and adipose tissue.

Liver

The main organ where de novo synthesis of fatty acids occurs.

Malate shuttle

The mechanism that transports Acetyl CoA from the mitochondria into the cytosol for fatty acid synthesis.

ATP citrate lyase

The cytosolic enzyme that breaks down citrate into oxaloacetate (OAA) and acetyl CoA.

Malate dehydrogenase

An enzyme that converts oxaloacetate (OAA) to malate in the cytosol using NADH as a coenzyme.

Malic enzyme

An enzyme that converts malate to pyruvate in the cytosol while producing NADPH.

Acetyl CoA carboxylase

The enzyme that catalyzes Stage 1 of fatty acid synthesis, converting Acetyl CoA and $CO_2$ into Malonyl CoA.

Biotin

A vitamin cofactor required by acetyl CoA carboxylase, specifically for the formation of carboxy-biotin.

Malonyl CoA

The product of the acetyl CoA carboxylase reaction which serves as a building block for fatty acid synthase.

Citrate (Activation)

A metabolic intermediate required to convert inactive protomers of acetyl CoA carboxylase into an active polymer.

Palmitoyl CoA

A long-chain acyl CoA that inhibits the polymer activation of acetyl CoA carboxylase.

Glucagon and epinephrine

Hormones that lead to the inhibition of acetyl CoA carboxylase activity.

Ketogenic diet

A diet that decreases fatty acid synthesis but increases cholesterol synthesis (i.e. $LDL$).

Fatty Acid Synthase

A multi-enzyme complex in Stage 2 of synthesis that exists as a dimer of identical polypeptides arranged head to tail.

Acyl carrier protein (ACP)

A functional component of the fatty acid synthase complex that carries the growing fatty acyl chain.

Palmitate

The 16-carbon saturated fatty acid ($16:0$) that is the end product of the fatty acid synthase complex.

NADPH

The coenzyme required as the reducing agent for both fatty acid synthesis and elongation reactions.

Fatty acid elongase

A multi-enzyme complex that uses malonyl CoA as a substrate to add two-carbon units to palmitate.

Smooth Endoplasmic Reticulum (SER)

The cellular location where fatty acid elongation occurs.

Mitochondrion (Short/Medium chain FA)

The location where production of medium and short chain fatty acids occurs via the reverse of beta-oxidation.

Brain (Very long chain FA)

The location where fatty acids with 22-24 carbons are produced for sphingolipid synthesis.

Myelination

The biological process in the brain that requires the synthesis of sphingolipids from very long chain fatty acids.

Delta 9 desaturase

The enzyme responsible for adding a double bond at the delta 9 position to create non-essential fatty acids like palmitoleic and oleic acid.

Linoleic acid

An essential omega 6 fatty acid ($18:2$) found in corn, soybean, and peanut oil.

Alpha linolenic acid

An essential omega 3 fatty acid ($18:3$) found in flax seed, borage oil, walnut oil, and required for concentration.

Eczema

A deficiency symptom specifically linked to a lack of linoleic acid (omega 6) in the diet.

Delta 6 desaturase

The rate-limiting enzyme in the synthesis of conditionally essential fatty acids from linoleic and linolenic acid.

Triacylglycerol

The storage form of fatty acids, also known as triglycerides.

Glycerol kinase

The enzyme used in the liver to produce glycerol $3-P$ for triglyceride storage.

DHAP (Dihydroxyacetone phosphate)

The glycolytic intermediate from which adipose tissue derives glycerol $3-P$ for triglyceride storage.

Leptin

A small molecular weight protein produced by white adipose tissue that suppresses food intake via the hypothalamus.

Ghrelin

The 'hunger hormone' produced by the gastrointestinal tract that is high before eating and low after eating.

White Adipocytes

Unilocular cells found in subcutaneous and visceral fat whose primary role is lipid uptake and release.

Brown Adipocytes

Multilocular cells found in infants in the intrascapular and neck region, responsible for non-shivering thermogenesis.

Beige Adipocytes

Multilocular cells found primarily in subcutaneous adipose tissue that can perform non-shivering thermogenesis.

Uncoupling protein 1 (UCP1)

The protein in brown and beige adipocytes that facilitates non-shivering thermogenesis.

PPAR$\gamma$

Peroxisome proliferator activated receptor gamma; the transcription factor that governs the differentiation of an adipocyte.

Estrogen

A sex steroid that decreases subcutaneous adipose tissue lipolysis and upregulates PPAR$\gamma$ expression.

Hypertrophy

The expansion of white adipose tissue through the increase in the size of individual adipocytes.

Hyperplasia

The expansion of white adipose tissue through the increase in the number of adipocytes.

Adipocyte Progenitor Cells (APCs)

Cells residing on the vasculature that differentiate into adipocytes under the influence of PPAR$\gamma$.

CXCR4

A G protein-coupled receptor responsible for stem cell migration, similar to the hematopoietic system.

Hypothalamus

The brain region that serves as the metabolic target for leptin in the regulation of food intake.

Corticotrophin releasing hormone (CRH)

The hormone used by the leptin system to suppress food intake.

Neuropeptide Y

A molecule in the brain whose suppression by leptin results in the reduction of food intake.