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Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
0 
 
 
 
 
 
 
Discipline: Botany 
Paper: Plant Metabolism 
Lesson: Lipid Metabolism 
Lesson Developer: Dr. Misha Yadav  
Department/College: Department of Botany, Shivaji 
College 
University of Delhi 
 
 
 
 
 
 
 
Page 2


Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
0 
 
 
 
 
 
 
Discipline: Botany 
Paper: Plant Metabolism 
Lesson: Lipid Metabolism 
Lesson Developer: Dr. Misha Yadav  
Department/College: Department of Botany, Shivaji 
College 
University of Delhi 
 
 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
1 
 
Table of Contents 
Chapter: Lipid Metabolism 
? Introduction  
? Lipid synthesis 
? Fatty acid biosynthesis 
? Synthesis of triglycerides: lipid deposition in 
seeds 
? Synthesis of oil bodies 
? Oil bodies: structure and composition 
? Catabolism of Triglycerides 
? Lipolysis: Mobilization of oil bodies 
? Fatty acid oxidation/ Beta (ß) oxidation 
? Alpha (a) oxidation 
? Glyoxylate cycle 
? Gluconeogenesis 
? Summary 
? Exercise/ Practice 
? Glossary 
? References 
? Weblinks 
 
 
 
 
 
Page 3


Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
0 
 
 
 
 
 
 
Discipline: Botany 
Paper: Plant Metabolism 
Lesson: Lipid Metabolism 
Lesson Developer: Dr. Misha Yadav  
Department/College: Department of Botany, Shivaji 
College 
University of Delhi 
 
 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
1 
 
Table of Contents 
Chapter: Lipid Metabolism 
? Introduction  
? Lipid synthesis 
? Fatty acid biosynthesis 
? Synthesis of triglycerides: lipid deposition in 
seeds 
? Synthesis of oil bodies 
? Oil bodies: structure and composition 
? Catabolism of Triglycerides 
? Lipolysis: Mobilization of oil bodies 
? Fatty acid oxidation/ Beta (ß) oxidation 
? Alpha (a) oxidation 
? Glyoxylate cycle 
? Gluconeogenesis 
? Summary 
? Exercise/ Practice 
? Glossary 
? References 
? Weblinks 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
2 
Learning Outcomes 
In this chapter you will learn about: 
? The synthesis of lipids, triglycerides and oil body formation 
? The catabolism of fatty acids 
? The various pathways of catabolism : (ß) oxidation, (a) oxidation and glyoxalate 
cycle 
? The pathway of gluconeogensis 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 4


Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
0 
 
 
 
 
 
 
Discipline: Botany 
Paper: Plant Metabolism 
Lesson: Lipid Metabolism 
Lesson Developer: Dr. Misha Yadav  
Department/College: Department of Botany, Shivaji 
College 
University of Delhi 
 
 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
1 
 
Table of Contents 
Chapter: Lipid Metabolism 
? Introduction  
? Lipid synthesis 
? Fatty acid biosynthesis 
? Synthesis of triglycerides: lipid deposition in 
seeds 
? Synthesis of oil bodies 
? Oil bodies: structure and composition 
? Catabolism of Triglycerides 
? Lipolysis: Mobilization of oil bodies 
? Fatty acid oxidation/ Beta (ß) oxidation 
? Alpha (a) oxidation 
? Glyoxylate cycle 
? Gluconeogenesis 
? Summary 
? Exercise/ Practice 
? Glossary 
? References 
? Weblinks 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
2 
Learning Outcomes 
In this chapter you will learn about: 
? The synthesis of lipids, triglycerides and oil body formation 
? The catabolism of fatty acids 
? The various pathways of catabolism : (ß) oxidation, (a) oxidation and glyoxalate 
cycle 
? The pathway of gluconeogensis 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
3 
Introduction 
Lipids are amongst the variety of biomolecules vital for the existence of cellular organisms. 
Lipids are a heterogeneous group of molecules sparingly soluble in water but highly soluble 
in non-polar organic solvents. Most of world’s lipids are produced by plants. Other 
organisms including human beings depend on the lipids synthesized by plants to fulfill lipid 
requirements.  A few of the important roles played by them are listed as follows: 
? They serve as means of energy storage in concentrated form especially in the form 
of triglycerides (TGs). 
? They are important components of cell membranes. 
? They are important for absorption of fat soluble vitamins (A, D, E and K) in animals. 
? Certain hormones are derived from lipids. Secondary metabolites derived from lipids 
have regulatory roles. Examples are prostaglandins and oxyilipins. 
? They serve to protect animal and plant surfaces from desiccation and infections, in 
the form of oils and waxy coverings.  
 
Lipids include fats, oils, waxes and compounds with similar properties. Common types are 
fatty acids, neutral lipids, phospholipids, glycerolipids, terpenes and steroids. Fatty acids are 
composed of long hydrocarbon chains terminating in carboxyl groups. Fatty acids can be 
categorized into two types: saturated and unsaturated fatty acids. Unsaturated fatty acid 
has at least one double bond in their hydrocarbon chain. Tremendous fatty acid diversity 
exists in lipids. To date, nearly 300 naturally occurring fatty acids have been described. 
Some commonly present fatty acids are shown in the table. 
Table: Some common fatty acids present in lipids. 
Name of fatty 
acid 
Number of 
carbon atoms: 
double bonds 
Structure 
Lauric acid  12:0 CH
3
(CH
2
)
10
COOH 
Myristic acid  14:0 CH
3
(CH
2
)
12
COOH 
Palmitic acid  16:0 CH
3
(CH
2
)
14
COOH 
Stearic acid  18:0 CH
3
(CH
2
)
16
COOH 
Oleic acid  18:1 CH
3
(CH
2
)
7
CH=CH(CH
2
)
7
COOH 
Linoleic acid  18:2 CH
3
(CH
2
)
4
CH=CHCH
2
CH=CH(CH
2
)
7
COOH 
Page 5


Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
0 
 
 
 
 
 
 
Discipline: Botany 
Paper: Plant Metabolism 
Lesson: Lipid Metabolism 
Lesson Developer: Dr. Misha Yadav  
Department/College: Department of Botany, Shivaji 
College 
University of Delhi 
 
 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
1 
 
Table of Contents 
Chapter: Lipid Metabolism 
? Introduction  
? Lipid synthesis 
? Fatty acid biosynthesis 
? Synthesis of triglycerides: lipid deposition in 
seeds 
? Synthesis of oil bodies 
? Oil bodies: structure and composition 
? Catabolism of Triglycerides 
? Lipolysis: Mobilization of oil bodies 
? Fatty acid oxidation/ Beta (ß) oxidation 
? Alpha (a) oxidation 
? Glyoxylate cycle 
? Gluconeogenesis 
? Summary 
? Exercise/ Practice 
? Glossary 
? References 
? Weblinks 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
2 
Learning Outcomes 
In this chapter you will learn about: 
? The synthesis of lipids, triglycerides and oil body formation 
? The catabolism of fatty acids 
? The various pathways of catabolism : (ß) oxidation, (a) oxidation and glyoxalate 
cycle 
? The pathway of gluconeogensis 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
3 
Introduction 
Lipids are amongst the variety of biomolecules vital for the existence of cellular organisms. 
Lipids are a heterogeneous group of molecules sparingly soluble in water but highly soluble 
in non-polar organic solvents. Most of world’s lipids are produced by plants. Other 
organisms including human beings depend on the lipids synthesized by plants to fulfill lipid 
requirements.  A few of the important roles played by them are listed as follows: 
? They serve as means of energy storage in concentrated form especially in the form 
of triglycerides (TGs). 
? They are important components of cell membranes. 
? They are important for absorption of fat soluble vitamins (A, D, E and K) in animals. 
? Certain hormones are derived from lipids. Secondary metabolites derived from lipids 
have regulatory roles. Examples are prostaglandins and oxyilipins. 
? They serve to protect animal and plant surfaces from desiccation and infections, in 
the form of oils and waxy coverings.  
 
Lipids include fats, oils, waxes and compounds with similar properties. Common types are 
fatty acids, neutral lipids, phospholipids, glycerolipids, terpenes and steroids. Fatty acids are 
composed of long hydrocarbon chains terminating in carboxyl groups. Fatty acids can be 
categorized into two types: saturated and unsaturated fatty acids. Unsaturated fatty acid 
has at least one double bond in their hydrocarbon chain. Tremendous fatty acid diversity 
exists in lipids. To date, nearly 300 naturally occurring fatty acids have been described. 
Some commonly present fatty acids are shown in the table. 
Table: Some common fatty acids present in lipids. 
Name of fatty 
acid 
Number of 
carbon atoms: 
double bonds 
Structure 
Lauric acid  12:0 CH
3
(CH
2
)
10
COOH 
Myristic acid  14:0 CH
3
(CH
2
)
12
COOH 
Palmitic acid  16:0 CH
3
(CH
2
)
14
COOH 
Stearic acid  18:0 CH
3
(CH
2
)
16
COOH 
Oleic acid  18:1 CH
3
(CH
2
)
7
CH=CH(CH
2
)
7
COOH 
Linoleic acid  18:2 CH
3
(CH
2
)
4
CH=CHCH
2
CH=CH(CH
2
)
7
COOH 
Lipid Metabolism 
 
Institute of Lifelong Learning, University of Delhi                                                                            
 
4 
Linolenic acid  18:3 CH
3
CH
2
CH=CHCH
2
CH=CHCH
2
CH=CH(CH
2
)
7
COOH 
 
The percentage of fatty acids present in plant lipids varies according to the species. Fatty 
acids are essential components of triglycerides/ triacylglycerols. TAGs consist of three fatty 
acid molecules esterified to a glycerol backbone.  Their biosynthesis, storage and 
degradation will be discussed shortly. 
They are non-polar.  They serve as major form of storage lipids. Upon complete oxidation 
TAGs release more than double the energy released during carbohydrate or protein 
hydrolysis. Thus, they are considered efficient reserves which accumulate fatty acids, for 
energy production and serve as a source of carbon blocks for synthesis of membranes. In 
higher plants, TAG deposition is mostly associated with seed tissue in the form of lipid 
droplets. These TAG deposits occur in the form of intracellular organelles known as oil 
bodies.  
 
Figure: Structure of unsaturated fat triglyceride 
Source: 
http://upload.wikimedia.org/wikipedia/commons/b/be/Fat_triglyceride_shorthand_formula.P
NG (cc) 
The mechanism of synthesis and degradation of TAG has been well characterized in 
developing seeds and during seed germination respectively. In plants the de novo synthesis 
of fatty acids occurs in plastids. Such fatty acids are then exported to endoplasmic 
reticulum, to be assembled into TAGs. The mechanism involved for membrane glycerolipid 
synthesis is similar to that for TAG synthesis. The flux of fatty acids from plastids, cytosolic 
acyl-CoA pool, specificity of enzymes (such as acyltransferases) involved in the pathway 
Read More
17 docs

FAQs on Lecture 11 - Lipid metabolism - Plant Metabolism - Botany

1. What is lipid metabolism?
Ans. Lipid metabolism refers to the biochemical processes that occur in living organisms to synthesize, store, and break down lipids. It involves the metabolism of various types of lipids, such as fatty acids, triglycerides, phospholipids, and cholesterol, to produce energy, structural components, and signaling molecules.
2. How are lipids metabolized in plants?
Ans. In plants, lipids are metabolized through various pathways. Lipid biosynthesis occurs in the plastids, specifically in the endoplasmic reticulum (ER) and the cytosol. Fatty acids are synthesized in the chloroplasts and are then transported to the ER for further modifications. Lipid degradation, on the other hand, takes place primarily in the peroxisomes. The breakdown of lipids generates energy and produces intermediates that are utilized in various metabolic pathways.
3. What are the functions of lipids in plants?
Ans. Lipids serve multiple functions in plants. They are important for energy storage, providing a concentrated source of metabolic fuel. Lipids also act as structural components of cell membranes, helping to maintain membrane integrity and function. Additionally, lipids play a crucial role in plant development, as they are involved in hormone signaling and cell signaling processes. Lipids are also involved in the synthesis of pigments, waxes, and cutin, which contribute to plant defense mechanisms and protection against environmental stress.
4. How are lipids transported in plants?
Ans. Lipids are transported within plants through various mechanisms. One important mode of lipid transport is through the formation of lipoprotein particles called lipoproteins. These particles consist of a core of hydrophobic lipids, such as triglycerides and cholesterol esters, surrounded by a shell of phospholipids and proteins. Lipids can also be transported through the formation of lipid droplets, which are storage organelles that can move within cells. Additionally, lipids can be transported through the phloem, the vascular tissue responsible for long-distance transport in plants.
5. How does lipid metabolism contribute to plant growth and development?
Ans. Lipid metabolism is essential for plant growth and development. Lipids provide a significant source of energy for plant cells, which is crucial for processes such as cell division, elongation, and differentiation. Lipids also play a role in membrane biogenesis, contributing to the formation of new cell membranes during cell division and growth. Furthermore, lipids act as signaling molecules, regulating various developmental processes, including seed germination, flower development, and root formation. Overall, lipid metabolism is closely linked to plant growth and development.
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