Lipid Metabolism Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the main function of Phosphatidilcholine in the body?

Nervous transmission as a acetylcholinesterase

Cell signaling

Programmed cell death

Source of methyl groups needed for many steps in metabolism (correct)

What is the name of the enzyme that is feedforward activated by citrate and inhibited by feedback inhibition of fatty acids?

Biotin dependent enzyme ACC (correct)

Fatty acid synthase

Decarboxylase

Carboxylase

What is the term for the process of fatty acid synthesis?

Fatty acid degradation

Fatty acid elongation

Lipogenesis (correct)

Lipolysis

What is the primary location where lipogenesis occurs?

Liver and lactating mammary glands Signup and view all the answers

What is the general property of lipids?

Soluble in organic solvents Signup and view all the answers

What is the term for the lipids that are widely distributed in every tissue of the body, particularly in nervous tissue?

Glycolipids Signup and view all the answers

What is the term for the main lipid constituents of membranes?

Phospholipids Signup and view all the answers

What is the primary function of lipids in the body?

Energy storage and provision Signup and view all the answers

What is the name of the phospholipid involved in cell signaling?

Phosphatidilinositol Signup and view all the answers

Which of the following is NOT a function of lipids?

Protein synthesis Signup and view all the answers

What is the term for lipids that contain one double bond?

Monounsaturated fatty acid Signup and view all the answers

What is the characteristic of fatty acids?

Amphoteric nature Signup and view all the answers

Which of the following is a type of complex lipid?

Phospholipid Signup and view all the answers

What is the primary function of insulin in relation to ACC?

Activating ACC Signup and view all the answers

What is the primary source of energy in lipids?

Fatty acids Signup and view all the answers

What is the cofactor of fatty acid biosynthesis?

Acyl carrier protein (ACP) Signup and view all the answers

Which of the following diseases is related to lipid metabolism?

All of the above Signup and view all the answers

What is the end product of fatty acid synthase activity?

Palmitic acid Signup and view all the answers

What is the term for lipids that are combined with proteins in the blood?

Lipoproteins Signup and view all the answers

Where does the further elongation of fatty acid chains occur?

Smooth endoplasmic reticulum (SER) Signup and view all the answers

What is required for desaturation reactions in the SER?

NADH, cytochrome b5 and its FAD-linked reductase Signup and view all the answers

How many carbon atoms are added to the growing fatty acid chain in each cycle?

2 Signup and view all the answers

What is the role of fatty acid synthase (FAS)?

Catalyzing enzymatic reactions in fatty acid biosynthesis Signup and view all the answers

What is unique about the brain's elongation capabilities?

It can produce very-long-chain fatty acids (over 22 carbons) Signup and view all the answers

What is the typical number of cycles performed to produce palmitic acid?

7 Signup and view all the answers

Study Notes

Lipid Metabolism Overview

Lipids are non-polar, hydrophobic compounds that are insoluble in water but soluble in organic solvents.
Lipids include fats, phospholipids, sterols, and others, serving as a concentrated source of energy (1g = 9.3 kcal).
Lipids play a role in thermoregulation, absorption of fat-soluble nutrients, and as structural components of cells and subcellular components.

Classification of Lipids

Simple lipids: acylglycerols, waxes
Complex lipids:
- Phospholipids: glycerophospholipids, sphingophospholipids
- Glycolipids
Sterols: cholesterol, hormones, vitamins, bile acids
Lipid derivatives: eicosanoids, polyisoprenoids, ketone bodies

Fatty Acids

Fatty acids are aliphatic carboxylic acids, typically occurring in the body as esters in natural fats and oils.
Fatty acids usually contain an even number of carbon atoms and can be saturated or unsaturated.
There are two types of unsaturated fatty acids: monounsaturated (one double bond) and polyunsaturated (two or more double bonds).

Glycerophospholipids

Glycerophospholipids are amphipathic, consisting of alkyl chains with a terminal carboxyl group.
Phospholipids are the main lipid constituents of membranes.
Examples of phospholipids include:
- Phosphatidylcholine (a source of choline and involved in nervous transmission)
- Phosphatidylethanolamine (cephalin)
- Phosphatidylserine (plays a role in apoptosis)
- Phosphatidylinositol (involved in cell signaling)
- Cardiolipin (diphosphatidylglycerol, a major lipid of mitochondrial membranes)

Cholesterol

Cholesterol is a sterol, an important lipid component of cell membranes.

Fatty Acid Synthesis (Lipogenesis)

Fatty acid synthesis occurs primarily in the liver and lactating mammary glands, and to a lesser extent in adipose tissue.
Lipogenesis uses ATP and NADPH and is a totally cytosolic process.
The synthesis of fatty acids involves the repeated addition of two-carbon units from malonyl-CoA to a growing fatty acid chain.
The process is catalyzed by a multi-enzyme complex called fatty acid synthase (FAS) and involves several enzymatic reactions, including condensation, reduction, dehydration, and reduction.
Acyl carrier protein (ACP) is a cofactor of fatty acid biosynthesis.
Palmitic acid (16:0) is the primary end product of fatty acid synthase activity.
Fatty acid chains can be further elongated by the addition of two-carbon units in the smooth endoplasmic reticulum (SER).
Desaturation of fatty acid chains occurs in the SER, requiring NADH, cytochrome b5, and its FAD-linked reductase.