Lipids Overview

Study Notes

Lipids

Heterogeneous group of organic molecules related to fatty acids
Relatively insoluble in water (hydrophobic) due to the predominance of hydrocarbon chains
Soluble in non-polar solvents such as ether, benzene, chloroform, and acetone
Most efficient form of stored energy in humans
Form a major part of our diet alongside carbohydrates and proteins
Excess lipids are stored as fat
Examples: Fatty acids, tri-acylglycerol, phospholipids, glycolipids, sphingolipids, steroids, vitamins A, D, E and K

Classification of Lipids

Simple:
- Neutral fats:
  - Esters of fatty acids with glycerol
  - Neutral (carry no charge)
  - Types:
    - Fats (Acylglycerol): Esters of fatty acids with glycerol (e.g., triglycerides)
    - Waxes: Esters of fatty acids with higher alcohols (alcohols other than glycerol, e.g., beeswax, lanolin)
Conjugated (Complex):
- Esters of fatty acids with alcohol, in addition to other groups (e.g., phospholipids)
- Phospholipids:
  - Glycerophospholipids
  - Sphingophospholipids
- Sphingolipids:
  - With or without phosphate:
    - Glycolipids
    - Sulfolipids
    - Gangliosides
    - Mucolipids
- Proteolipids (Lipoproteins):
Derived:
- Any substance that can be obtained by hydrolysis of simple or complex lipids (e.g., fatty acids, steroids, fat-soluble vitamins, ketone bodies, carotenoids)

BioMedical Importance of Lipids

Diet:
- Source of high energy
- Contain fat-soluble vitamins
- Contain essential fatty acids
- Make diet palatable
Body:
- Adipose tissue: Storage form of energy
- Thermal insulator: Subcutaneous tissue
- Electrical insulator: Nervous tissue (allows rapid propagation)
- Lipoprotein formation:
  - Component of cell membrane structure
  - Act as a transport form of energy in the blood

Neutral Fats (Tri Acyl Glycerol)

Esters of 3 fatty acids with glycerol
Glycerol: Short-chain alcohol containing 3 OH groups
Types:
- Simple: Contains similar fatty acids (e.g., tripalmitin and triolein)
- Mixed: Contains different fatty acids (e.g., palmito-oleio-stearin and di-stearin palmitin)
Solid form: Fats
Liquid form: Oils

Fatty Acids (FA)

Long-chain organic molecules containing carboxylic end (COOH)
Types:
- Saturated:
  - No double bonds (no C=C)
  - Non-essential
- Unsaturated:
  - Contain one or more double bonds
  - Essential or non-essential
Water insoluble long-chain hydrocarbons
Can be saturated or unsaturated
Mostly mono-carboxylic acids
Mostly aliphatic (no-branches) acids
Occur mainly as esters in neutral fats
Can occur freely in plasma
Fatty acids in neutral fats contain an even number of carbons

Saturated Fatty Acids (Anoic)

No double bonds (no C=C)
General Formula: CH3 - (CH2)n- COOH
(n): number of methylene groups (CH2 )
Examples:
- Butyric acid (4C): CH3 – CH2 – CH2 – COOH
- Caproic acid (6C): CH3– (CH2)4– COOH
- Palmitic acid (16C): CH3 – (CH2)14– COOH
- Stearic acid (18C ): CH3 – (CH2)16– COOH

Carbon Skeleton of Fatty Acid

Numbered either:
- From the Carboxylic Group (COOH):
  - Delta (Δ) or Alpha, Beta, Gamma, Delta, Epsilon
- From the Terminal Methyl Group (Omega=ώ):

Non-Essential Fatty Acids

Can be synthesized in the body from Acetyl CoA (common metabolic pool)
Include saturated & mono-unsaturated FA

Unsaturated Fatty Acids (Enoic)

Fatty acids containing double bond(s)
Types:
- Mono-unsaturated: One double bond
- Poly-unsaturated: More than one double bond
General Formula: Cn – H2n-1– COOH
(n): number of carbon atoms without COOH
Double bonds:
- Nearly always in cis configuration
- Spaced at 3 carbon intervals if the fatty acid has more than one double bond

Mono-unsaturated Fatty Acids

MonoEnoic Fatty acids (Non-essential):
- Example:
  - Palmitoleic (16C) written as 16:1 Δ9, 16:1 ώ7
  - Oleic = OctaDecaEnoic (18C) written as 18:1 Δ9

Poly-unsaturated Fatty Acids

PolyEnoic fatty acids (Essential):
- Linoleic acid (18:2 Δ9,12 )
- Linolenic acid (18:3 Δ9,12,15 )
- Arachidonic acid (20:4 Δ5,8,11,14)
PolyThenoic fatty acids:
- Docosahexaenoic acid (DHA) (22:6 ω3 )
- Eicosapentaenoic acid (EPA) (20:5 ω3)

Essential Fatty acids

Cannot be synthesized in the body
Must be obtained from the diet
Play essential roles in cell membrane function, hormone synthesis, and inflammatory responses

Naming of Fatty Acids

Delta (Δ) system: Begins at carboxyl group
Omega (ώ) system: Begins at methyl group
Common names: Based on the number of carbons, level of saturation, and location of double bonds

Trans Fatty Acids

Similar to saturated fatty acids in structure
Increase risk of cardiovascular disease

Essential Fatty Acids

Linoleic acid (C18:2 ω6): precursor to arachidonic acid
α-Linolenic acid (C18:3 ω3): precursors to EPA and DHA

Importance of Essential Fatty Acids

Role in growth and development
Immune function
Regulation of blood pressure and cholesterol levels
Brain function
Inflammation and pain control

Description

This quiz covers the fundamental aspects of lipids, including their classification, properties, and significance in human nutrition. It explores the different types of lipids such as simple and conjugated lipids, and their roles in energy storage and dietary composition. Test your knowledge on the various forms of lipids and their functions in biological systems.

Lipids Overview

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Questions and Answers

What characteristic makes lipids hydrophobic?

Which of the following are classified as simple lipids?

What form of energy do lipids primarily provide in the human body?

Which of the following is NOT a type of lipid mentioned?

Which classification of lipids includes both phospholipids and sphingolipids?

What is the primary structure that neutral fats consist of?

Which type of fatty acid contains no double bonds?

Which of the following is a function of lipids in the body?

What kind of fatty acid is characterized by having one or more double bonds?

Which fatty acid is commonly found in coconut oil and palm oil?

Which of the following fatty acids is a saturated fatty acid with 18 carbon atoms?

Which of the following accurately describes simple neutral fats?

Which of the following is a characteristic of polyunsaturated fatty acids?

Which fatty acid is considered essential and must be obtained through the diet?

In the classification of fatty acids, what does 'omega (ω)' refer to?