Biochemistry Fatty Acids Quiz

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Questions and Answers

What type of fatty acids are solid at body temperature due to being composed of saturated fatty acids?

Triglycerides (correct)

Unsaturated fatty acids

Trans fatty acids

Phospholipids

How do the double bonds in natural unsaturated fatty acids primarily orient?

In a spiral shape

In a linear shape

In a bent shape (correct)

In a zig-zag shape

Which fatty acids are associated with an increased risk of diseases such as cardiovascular disease and diabetes?

Long-chain fatty acids

Saturated fatty acids

Trans fatty acids (correct)

Cis fatty acids

Why can't the brain efficiently use fatty acids as a source of fuel?

There is no adequate transporter for fatty acids in the brain. Signup and view all the answers

Which of the following is a disadvantage of using fatty acids as an energy source in neurons?

Fatty acid oxidation generates superoxide, causing oxidative stress. Signup and view all the answers

What biological function do fatty acids serve aside from being a source of energy?

They are involved in the formation of cell membranes. Signup and view all the answers

What is the primary reason that fatty acids cannot ensure rapid ATP generation during high neuronal activity?

The ATP generation rate from fatty acids is slower than glucose. Signup and view all the answers

In the context of fatty acids, what does biohydrogenation primarily refer to?

The modification of dietary unsaturated fatty acids by rumen bacteria. Signup and view all the answers

What triggers the secretion of secretin in the small intestine?

Acidic materials from the stomach Signup and view all the answers

Which component is primarily secreted by the pancreas in response to secretin?

Bicarbonate Signup and view all the answers

What is the main process by which triacylglycerols are packaged in intestinal cells?

Fatty acid activation and esterification Signup and view all the answers

Which lipoprotein primarily transports dietary lipids from the intestine?

Chylomicron Signup and view all the answers

Which statement is true regarding apolipoproteins?

They can serve as enzyme cofactors or inhibitors. Signup and view all the answers

Which of the following is NOT one of the five major plasma lipoproteins?

Triglyceride Signup and view all the answers

What happens to fatty acids and monoacylglycerols after digestion?

They are packaged into micelles for absorption. Signup and view all the answers

Which of the following is true about integral and peripheral apolipoproteins?

Integral apolipoproteins cannot be removed. Signup and view all the answers

Which enzyme is responsible for converting palmitoyl-CoA to palmitoleoyl-CoA during the synthesis of monounsaturated fatty acids?

9 desaturase Signup and view all the answers

What is the role of methylene groups in the synthesis of polyunsaturated fatty acids?

They are used to separate additional double bonds introduced into MUFAs. Signup and view all the answers

What happens to desaturation and elongation systems during a starving state?

They are diminished. Signup and view all the answers

What is the primary reason that triacylglycerols cannot penetrate cell membranes?

Their large molecular size. Signup and view all the answers

Where does the synthesis of triacylglycerol primarily occur in the body?

In the liver and adipose tissue. Signup and view all the answers

Which pathway is involved in the conversion of glycerol-3-phosphate to phosphatidate?

Glycerol phosphate pathway Signup and view all the answers

Which condition is known to diminish the desaturation and elongation enzyme systems?

Starving state. Signup and view all the answers

What is the initial step in synthesizing triacylglycerols in tissues?

Formation of acyl-CoA from activated fatty acids. Signup and view all the answers

What is the primary function of chylomicrons?

To transport dietary lipids from the intestine Signup and view all the answers

Which lipoprotein primarily delivers cholesterol to various tissues?

LDL Signup and view all the answers

What major substances are released from triglycerides during their digestion in peripheral tissues?

Fatty acids and glycerol Signup and view all the answers

What happens to the remnants of chylomicrons after their triglycerides are digested?

They are taken up entirely by the liver Signup and view all the answers

Which lipoprotein is formed during the lipolysis of VLDL triglycerides?

IDL Signup and view all the answers

What is the major function of HDL in lipid transport?

To transport excess cholesterol from tissues back to the liver Signup and view all the answers

What type of lipids does VLDL primarily transport?

Endogenous lipids made by the liver Signup and view all the answers

What role does lipoprotein lipase play in lipid transport?

Converts triglycerides into fatty acids and glycerol Signup and view all the answers

What is the primary source of cholesterol in the human body?

Biosynthesis and diet Signup and view all the answers

Which enzyme is considered the regulatory enzyme in cholesterol biosynthesis?

HMG-CoA reductase Signup and view all the answers

In which cellular compartments does cholesterol biosynthesis primarily occur?

Cytosol and endoplasmic reticulum Signup and view all the answers

What is the first step in the biosynthesis of cholesterol?

Biosynthesis of mevalonate from acetyl-CoA Signup and view all the answers

What regulates the activity of HMG-CoA reductase?

Feedback inhibition and metabolic control Signup and view all the answers

What is the outcome of excess intracellular free cholesterol regulation?

Inhibition of LDL receptor expression Signup and view all the answers

How does glucagon affect cholesterol biosynthesis?

Decreases cholesterol synthesis Signup and view all the answers

What is the role of bile acids in cholesterol metabolism?

Bile acids facilitate enterohepatic circulation of cholesterol Signup and view all the answers

Study Notes

Fatty Acids and Their Properties

Triglycerides (TG) with three saturated fatty acids remain solid at body temperature.
Membrane lipids, having more unsaturated fatty acids, are liquid at all environmental temperatures.
Geometric isomerism in unsaturated fatty acids is classified as “cis” and “trans.”
Naturally occurring unsaturated fatty acids feature “cis” double bonds, creating a U-shape which impacts molecular packing in cell membranes.
“Trans” fatty acids are linked to specific foods and the process of hydrogenation, posing increased risks for cardiovascular disease (CVD) and diabetes mellitus (DM).

Biological Functions of Fatty Acids

Fatty acids are significant energy sources for skeletal and cardiac muscles, while the brain primarily relies on glucose.
Fatty acids are bound to albumin but cannot cross the blood-brain barrier effectively, leading to delayed transport.
Several factors limit the brain's use of fatty acids:
- Greater oxygen demand for ATP generation via β-oxidation compared to glucose.
- Production of superoxide, increasing oxidative stress in neurons.
- Slower ATP production from fatty acids compared to glucose during high-energy demands.

Lipid Absorption in the Gastrointestinal Tract

Pancreatic lipase hydrolyzes triglycerides into free fatty acids and monoacylglycerols.
Digested products include:
- 2-monoacylglycerol (≈72%)
- 1-monoacylglycerol (≈6%)
- Glycerol (≈22%)
Fatty acids and monoacylglycerols are packaged into micelles for absorption through microvilli.

Transport of Lipids

Lipids are inherently insoluble in water, requiring transport via lipoproteins in the circulatory system.
Major plasma lipoproteins include:
- Chylomicrons
- Very low-density lipoproteins (VLDL)
- Intermediate-density lipoproteins (IDL)
- Low-density lipoproteins (LDL)
- High-density lipoproteins (HDL)

Role of Apolipoproteins

Integral apolipoproteins are integral to lipoprotein structure, while peripheral ones can transfer between lipoproteins.
Apolipoproteins serve multiple functions:
- Structural components (e.g., Apo B)
- Enzyme cofactors (e.g., Apo CII for lipoprotein lipase)
- Ligands for lipoprotein receptors in tissues (e.g., Apo B100 and Apo E for LDL receptors).

Chylomicrons and VLDL

Chylomicrons transport dietary lipids from the intestine to peripheral tissues.
Triglycerides (TG) from chylomicrons are hydrolyzed to fatty acids and glycerol for tissue uptake.
VLDLs transport endogenous lipids synthesized in the liver to various tissues, resembling the chylomicron transport pathway.
Intermediate-density lipoproteins (IDL) are formed during the breakdown of VLDL and quickly convert to LDL.

LDL and HDL Functions

LDL is the primary source of cholesterol for tissues and constitutes mainly cholesterol.
HDL acts as a scavenger, transporting excess cholesterol back to the liver for excretion.

Fatty Acid Desaturation and Synthesis

Monounsaturated fatty acids are synthesized in tissues, primarily the liver, using a desaturase enzyme.
Polyunsaturated fatty acids are formed by introducing additional double bonds using desaturase and elongase enzyme systems, which are reduced in starvation states.

Triacylglycerol Biosynthesis

Triacylglycerols are synthesized for energy storage in adipose tissue and muscles but cannot cross cell membranes.
Liver synthesizes TG, which is then transported via lipoproteins, while mammary glands excrete TG in milk.

Cholesterol Metabolism

Cholesterol is synthesized primarily from acetyl-CoA, with more than half produced endogenously.
Key steps in cholesterol biosynthesis include conversion to mevalonate, formation of squalene, and subsequent conversion to lanosterol and finally cholesterol.
Regulation of cholesterol biosynthesis occurs through feedback mechanisms, enzyme degradation, and receptor-mediated uptake of LDL.

Regulation of Cholesterol Biosynthesis

HMG-CoA reductase, a rate-limiting enzyme, is controlled by sterol levels, such as through gene expression and post-translational modifications.
Plasma cholesterol levels are maintained through the uptake of LDL and reverse cholesterol transport mediated by HDL.

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Description

Test your knowledge on the structure and properties of saturated and unsaturated fatty acids. This quiz covers melting points, isomerism, and the role of fatty acids in biological membranes. Perfect for students of biochemistry and related fields.