Lipid Synthesis P1 Flashcards
Why is triacylglycerol (TAG) considered the primary form of stored energy in the body?
TAG is the primary form of stored energy because it is stored in fat droplets within adipocytes and provides more energy per gram than glycogen. Although carbohydrates can be stored as glycogen, glycogen stores are limited and less efficient as an energy reserve.
Where is TAG stored in the body, and how does this storage compare to glycogen?
TAG is stored within fat droplets in adipocytes. Unlike glycogen, which has limited storage capacity, TAG can be stored in larger quantities and is more efficient for long-term energy storage.
What is the main role of phospholipids in cellular functions?
Phospholipids are essential for membrane synthesis as they are the primary components of cellular membranes, enabling cell growth, organ proliferation, and maintaining cellular structure.
Why is lipid synthesis necessary for cellular membrane formation?
Lipid synthesis is crucial for membrane formation because the growth or proliferation of organs and cells requires additional cellular membranes, which are composed primarily of phospholipids.
How do lipids function in cell signaling, and what are some examples of lipid-based signaling molecules?
Lipids act as hormones and signaling molecules that regulate various physiological processes. Examples include cholesterol, which contributes to steroid hormone synthesis, as well as vitamin D, steroid hormones, and retinols, all of which are essential in signaling pathways.
What types of hormones or vitamins are derived from lipids?
Lipid-derived molecules include cholesterol-based hormones, vitamin D, steroid hormones, and retinols, all of which play roles in cellular signaling and regulatory processes.
How do energy storage, membrane synthesis, and signaling collectively explain the importance of lipid synthesis?
Lipid synthesis is vital for creating energy reserves (TAG storage), forming cellular membranes (phospholipids), and producing signaling molecules (e.g., cholesterol, steroid hormones), supporting metabolic needs, cell integrity, and regulatory functions.
What type of metabolic pathway is fatty acid synthesis, and what are the general requirements for it?
Fatty acid synthesis is an anabolic pathway that requires NADPH and ATP. It is a reductive process, distinguishing it from catabolic pathways, which generally use NAD+ as the electron acceptor.
Why is NADPH used in fatty acid synthesis instead of NAD+?
NADPH is used because it allows for separate pools of electron carriers: NAD+ is maintained in high concentrations for catabolic processes, while NADPH is available in high concentrations for anabolic processes like fatty acid synthesis.
Where does fatty acid synthesis primarily occur within the cell and the body?
Fatty acid synthesis occurs in the cytosol of eukaryotic cells, primarily in the liver and adipose tissues.
Which molecule provides the two-carbon units for fatty acid synthesis, and how is it formed?
Malonyl-CoA provides the two-carbon units. It is formed from acetyl-CoA via carboxylation, a reaction catalyzed by acetyl-CoA carboxylase.
Describe the role of acetyl-CoA carboxylase in fatty acid synthesis.
Acetyl-CoA carboxylase has three domains—biotin carboxylase, biotin carrier protein, and transcarboxylase. It carboxylates acetyl-CoA to form malonyl-CoA, using HCO₃⁻ and ATP.
Outline the three-step process catalyzed by acetyl-CoA carboxylase to form malonyl-CoA.
The biotin carboxylase domain adds a CO₂ group to biotin.
The biotin carrier protein transfers the CO₂ to the transcarboxylase domain.
The transcarboxylase domain transfers CO₂ to acetyl-CoA, forming malonyl-CoA.
What is the role of fatty acid synthase (FAS) in fatty acid synthesis?
FAS is a large enzyme complex with seven domains that catalyzes the synthesis of fatty acids by adding two-carbon units (from malonyl-CoA) to a growing acyl chain.
How does the acyl carrier protein (ACP) contribute to fatty acid synthesis within the FAS complex?
ACP acts as a flexible shuttle, tethering the growing fatty acyl chain and transferring reaction intermediates between the active sites within FAS.
