Biochemistry: Classification of Lipids

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Questions and Answers

What effect do essential fatty acids have on serum cholesterol levels?

They increase serum cholesterol levels.

They promote the synthesis of cholesterol.

They decrease serum cholesterol levels. (correct)

They have no effect on serum cholesterol levels.

Which of the following is NOT a symptom of essential fatty acid deficiency?

Scaly skin

Increased wound healing efficiency (correct)

Hyperkeratosis

Acanthosis

How do cis isomers of fatty acids affect biological membranes?

They stabilize the membrane structure.

They decrease membrane fluidity.

They have no impact on membrane fluidity.

They increase membrane fluidity. (correct)

What is a consequence of long-term consumption of trans fatty acids?

Exacerbation of essential fatty acid deficiency. Signup and view all the answers

Why are melting temperatures of fatty acids significant?

They are key to the fluidity of cell membranes. Signup and view all the answers

What type of lipid serves as a primary storage form of energy in the body?

Triacylglycerol Signup and view all the answers

Which of the following is NOT a function of lipids?

Acting as catalysts in biochemical reactions Signup and view all the answers

Which classification of lipids includes triacylglycerol and waxes?

Simple lipids Signup and view all the answers

Phospholipids are primarily involved in which of the following functions?

Structural components of biomembranes Signup and view all the answers

Which of the following describes derived lipids?

They are products obtained after hydrolysis of simple and compound lipids. Signup and view all the answers

What are the characteristics of fatty acids classified as saturated?

Are fully hydrogenated Signup and view all the answers

Which of the following is a function of amphipathic lipids?

Detergency and emulsification Signup and view all the answers

What is a key feature of the fluid mosaic model of biological membranes?

Proteins embedded in lipids can move laterally. Signup and view all the answers

What is the general formula for fatty acids?

R—CO—OH Signup and view all the answers

Which type of fatty acids are primarily found in microbial cell walls?

Odd chain fatty acids Signup and view all the answers

How are dietary short- and medium-chain fatty acids absorbed in the body?

Directly absorbed in the small intestine and transported via the portal vein Signup and view all the answers

Which classification of fatty acids refers to those with 2 or more double bonds?

Polyunsaturated fatty acids Signup and view all the answers

What is a characteristic of short-chain fatty acids?

They have 2 to 6 carbon atoms and act as metabolic intermediates Signup and view all the answers

What is the maximum number of carbon atoms usually found in long-chain fatty acids?

20 Signup and view all the answers

Which of the following fatty acid types is NOT classified by the length of its hydrocarbon chain?

Saturated fatty acids Signup and view all the answers

In which category do fatty acids with an even number of carbon atoms mostly fall?

Long-chain fatty acids Signup and view all the answers

Which fatty acids are considered essential fatty acids for humans?

Linoleic acid and linolenic acid Signup and view all the answers

What is a characteristic of monounsaturated fatty acids?

They only contain one double bond Signup and view all the answers

Which fatty acid is a precursor to eicosanoids?

Arachidonic acid Signup and view all the answers

What are the two main classifications of unsaturated fatty acids?

Monounsaturated and polyunsaturated Signup and view all the answers

Why are linoleic and linolenic acids essential for humans?

Humans lack the enzymes to synthesize them with double bonds beyond C9 Signup and view all the answers

What is docosahexaenoic acid (DHA) primarily needed for?

Development of brain and retina Signup and view all the answers

Which of the following accurately describes the function of essential fatty acids?

They serve as precursors for eicosanoids Signup and view all the answers

Which of the following is NOT a type of eicosanoid derived from arachidonic acid?

Linoleic acid Signup and view all the answers

Study Notes

Learning Outcomes

Students will be able to classify lipids and describe their function in the body.
Students will be able to classify fatty acids (FA) and describe the properties of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA).
Students will be able to describe the chemical properties of fatty acids.
Students will be able to describe the structure, properties, and function of triacylglycerols.
Students will be able to classify phospholipids and describe their functions.
Students will be able to identify major classes of lipids and describe their biochemical functions.
Students will be able to outline the general features of the fluid mosaic model of biological membranes.

Definitions and Classification of Lipids

Lipids are a diverse group of hydrophobic organic molecules.
They include fats, oils, steroids, waxes, and related compounds.
Lipids are insoluble in water but soluble in organic solvents like chloroform, ether, and benzene.
Lipids are classified as simple, compound, and derived lipids based on their chemical structure.

Simple Lipids

These are esters of fatty acids with glycerol or other alcohols.
Triacylglycerols (TG) or triglycerides are the most common type of simple lipid, also known as neutral fats.
Waxes are esters of fatty acids with long-chain alcohols.

Compound Lipids

These are esters of fatty acids with an alcohol that also contains additional prosthetic groups.
Phospholipids contain a phosphate group.
Glycolipids contain carbohydrate groups.
Lipoproteins contain proteins.

Derived Lipids

These are products of hydrolysis of simple and compound lipids.
Examples include fatty acids (FAs), steroids, cholesterol, and lipid-soluble vitamins and hormones.

Functions of Lipids

Storage of energy (triacylglycerols).
Structural components of biomembranes (phospholipids and cholesterol).
Metabolic regulators (steroid hormones and prostaglandins).
Acting as surfactants, detergents, emulsifying agents (amphipathic lipids).
Acting as electrical insulators in neurons.
Providing insulation against temperature changes (subcutaneous fat).
Shaping and contouring the body.
Providing cushioning effect for internal organs (fat pads).
Assisting in the absorption of fat-soluble vitamins (A, D, E, and K).
Enhancing taste and palatability of food.

Fatty Acids

Fatty acids are carboxylic acids with a hydrocarbon chain.
The general formula is R-COOH, where COOH is the carboxyl group.
Fatty acids are classified based on the number of carbon atoms and the presence or absence of double bonds in their hydrocarbon chains.

Classification of Fatty Acids

Chain Length: Short (2-6 carbons), medium (8-14 carbons), long (16-24 carbons), and very long (>24 carbons).
Saturation: Saturated (no double bonds), monounsaturated (one double bond), and polyunsaturated (two or more double bonds).
Position of Double Bonds (omega numbering): Indicate the position of the first double bond from the methyl (ω) end of the hydrocarbon chain.

Essential Fatty Acids

Essential fatty acids cannot be synthesized by the body and must be obtained through the diet.
Linoleic acid (ω-6) and α-linolenic acid (ω-3) are the essential fatty acids.
Arachidonic acid (ω-6) can be derived from linoleic acid.

Trans and cis Fatty Acids

Naturally occurring fatty acids are predominantly cis isomers.
Trans isomers are often formed during processing of oils (partially hydrogenated oils) and are associated with increased risk of certain health problems.

Deficiency in essential Fatty Acids

Symptoms may include skin issues, fatty liver, impaired mitochondrial function, and decreased fibrinolytic activity.

Functions of Essential Fatty Acids

Involved in the synthesis of eicosanoids (prostaglandins, thromboxanes, prostacyclins, and leukotrienes).
Important components of cell membranes.
Essential for brain and retina development (DHA).
Help lower serum cholesterol levels, limiting atherosclerosis.

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Description

This quiz focuses on the classification and functions of lipids within the body. Students will explore various types of fatty acids, their properties, and the chemical structure of triacylglycerols and phospholipids. Additionally, the quiz covers the fluid mosaic model of biological membranes.