Chapter 7 Lipid Metabolism Flashcards
Key Functions of Lipids in Plants (4)
Energy storage
Membrane structure
Signaling molecules
Thermal Protection
serve as a concentrated source of energy.
Lipids
____, stored in seeds and
other tissues, provide energy during periods of growth and development.
Triacylglycerols (TAGs)
__, ___, and ___are fundamental components of cellular membranes,
contributing to membrane integrity, fluidity, and functionality.
Phospholipids, glycolipids, and sterols
__ and ___ help plants retain moisture and protect against environmental
stressors, such as extreme temperatures and pathogens.
Waxes and cuticular lipids
Types of Lipids in Plants
Fatty acids
Triglycerides
Phospholipids
Glycolipids
Sterols
___ are carboxylic acids with long hydrocarbon chains
Fatty acids
___ have no double bonds between carbon atoms, making them solid at room temperature,
Saturated fatty acids
______ contain one or more
double bonds, which introduces kinks in their structure and keeps them liquid at
room temperature.
unsaturated fatty acids
are the primary form of stored energy in plants, predominantly
found in seeds and some fruits.
Triglycerides
are composed of three fatty acids attached to
a glycerol molecule.
Triglycerides
During ____, triglycerides are broken down into fatty
acids and glycerol, providing energy and carbon skeletons for the growing plant.
germination
They serve not only as energy reserves but also as thermal insulators and
protective agents
Triglycerides
They consist of
two fatty acid tails, a glycerol backbone, and a phosphate group.
Phospholipids
The unique
structure of phospholipids,
with hydrophilic (water-attracting) heads and
hydrophobic (water-repelling) tails,
___are lipids that contain carbohydrate moieties
Glycolipids
These molecules are typically found in the outer layer of the plasma
membrane and contribute to cell-cell interactions, which are crucial for processes
like immune response and tissue development
Glycolipids
are a subgroup of lipids characterized by a four-ring structure
Sterols
most common sterols are
sitosterol and stigmasterol.
These compounds help to
maintain membrane fluidity and integrity, particularly under varying temperature
conditions.
sterols
can also play roles in plant growth and development by
influencing hormone pathways and cell signaling mechanisms
Sterols
Lipid Metabolism Pathways
Lipogenesis
Lipolysis
location of lipogenesis
plastids, particularly in chloroplasts, and within
the endoplasmic reticulum (ER) of cells.
Key process of lipogenesis
Fatty acid synthesis
Triglyceride formation
Lipid modification
Fatty Acid Synthesis:
The process begins with ____, which is derived from carbohydrates or
proteins.
acetyl-CoA
Fatty Acid Synthesis:
Acetyl-CoA is converted to ____ by the enzyme _____
malonyl-CoA;
acetyl-CoA
carboxylase.
Fatty Acid Synthesis:
Malonyl-CoA is then used in the _____ to
elongate the fatty acid chain in a series of condensation, reduction, dehydration,
and reduction steps, producing ____ (usually C16 and C18).
fatty acid synthase complex;
long-chain fatty acids
Triglyceride Formation:
Once fatty acids are synthesized, they are linked to ____ through
____, forming triglycerides.
glycerol-3-phosphate;
esterification;
Triglyceride formation:
Triglycerides are primarily stored in specialized organelles known as ___, with a significant concentration found in seeds, which rely on
these reserves for energy during germination
oil bodies or
lipid droplets
Lipid Modifications:
○ The synthesized fatty acids can undergo various modifications, including
___ and ____
desaturation and elongation.
Lipid modification results in the formation of different lipid
classes such as _____(important for cell membranes) and ____
(which play roles in cell recognition and signaling).
phospholipids ;
glycolipids
location of lipolysis
mainly occurs in the peroxisomes and mitochondria
key process of lipolysis
Triglyceride hydrolysis
Beta-oxidation
Glyoxylate cycle
Triglyceride hydrolysis:
The breakdown of stored triglycerides starts with their hydrolysis into ___ and___, facilitated by enzymes ___
free fatty acids and glycerol;
lipase
The released free fatty acids are transported into peroxisomes and mitochondria
for a process called ____
beta-oxidation.
During beta-oxidation, fatty acids are broken down into ___, along
with the production of reducing equivalents such as____ and ____
acetyl-CoA units;
NADH and FADH2.
Inplant seedlings, the ___ is a unique metabolic pathway that
enables the conversion of acetyl-CoA, produced during fatty acid oxidation, into
carbohydrates.
glyoxylate cycle
This conversion is vital for supporting growth and energy needs during early
development stages when seedlings rely on stored lipids before they can
photosynthesize effectively
glyoxylate cycle
Factors controlling the Lipid Metabolism
Hormonal Control
Nutritional Status
Environmental Factors
Microbial Interactions
Plant Hormones=
Phytohormones
examples of phytohormones
Auxins
abscisic acid
ethylene
: Can influence lipid accumulation by modulating cell growth and
division.
Auxins
Often increases during stress, promoting lipid mobilization
for energy.
Abscisic Acid (ABA):
: Affects lipid breakdown during fruit ripening and senescence.
Ethylene
Nutritional Status depends on
Carbon Availability
Nutrient Levels
Excess carbohydrates can lead to increased lipid storage through pathways like
de novo fatty
acid synthesis.
Essential nutrients, such as __ and ___, play crucial roles
in lipid metabolism
nitrogen and phosphorus
____ can impair lipid synthesis, while sufficient
levels promote healthy growth and storage.
Nitrogen deficiency
Environmental Factors
Light
Temperature
stress condiitons
Temperature fluctuations can alter lipid composition, particularly the ___, impacting membrane fluidity and metabolic rates.
fatty acid profile
Environmental stressors (e.g., drought, salinity) can trigger
alterations in lipid metabolism, often leading to the accumulation of stress-related lipids
like___ and
___
phospholipids and fatty acid derivatives
can influence lipid metabolism in plants by enhancing nutrient
availability and promoting beneficial interactions that can modify metabolic pathways
Soil microbiota
fatty acids modification can be utilized in
waxes
cutin and suberin
sterols
