Lipids Flashcards
This is a broad category that includes fats, oils, waxes, and other substances that are hydrophobic (not soluble in water). Lipids are diverse in structure and function but are generally characterized by their solubility in nonpolar solvents. Lipids include triglycerides (fats and oils), phospholipids (which make up cell membranes), and sterols (like cholesterol).
Describe the solubility characteristics of lipids.
Lipids have only slight solubility in water and tend to self-associate due to the hydrophobic effect.
Define triglycerides and their composition.
Triglycerides, also known as triacylglycerol, are lipids made up of one glycerol molecule and three fatty acid tails.
How are simple triglycerides defined?
Simple triglycerides are those in which all three fatty acids are identical.
Explain the structure and function of phospholipids.
Phospholipids (glycerophospholipids) consist of one glycerol backbone, two fatty acid tails, and one phosphate group, making them amphipathic and a major component of biological membranes.
What role do fatty acids play in biological systems?
Fatty acids are involved in energy storage, membrane structure, and serve as precursors for signaling molecules.
Describe the structure of sphingolipids.
Sphingolipids have a sphingosine backbone that is amide (Nitrogen) bonded to a fatty acid tail and are also amphipathic.
How does cholesterol contribute to cell membranes?
Cholesterol has a four-ring structure and is a key component of the plasma membrane, also serving as a precursor for steroid hormones.
What are waxes and their primary function?
Waxes are lipids made of a long chain fatty acid attached to a long chain alcohol, known for their extreme hydrophobicity and protective functions.
Define the term amphipathic as it relates to lipids.
Amphipathic refers to molecules that have both hydrophobic (water-repelling) and hydrophilic (water-attracting) parts, such as phospholipids and sphingolipids.
How do lipids contribute to energy storage?
Lipids, particularly fatty acids and triglycerides, serve as a major form of energy storage in biological systems.
Define phospholipids and their role in cells.
Phospholipids are membrane lipids that form bilayers, creating cell boundaries and enabling cytoplasmic compartmentalization.
Explain the formation of micelles by single chain lipids.
Single chain lipids form micelles and function as detergents, helping to solubilize fats.
How are lipids transported in the body?
Lipids are transported using structures such as serum lipoproteins due to their insolubility.
Define the nomenclature for fatty acids.
Fatty acid nomenclature is defined by the number of carbons and the number of double bonds, such as 16:0 for palmitate and 20:4 for arachidonate.
Describe the characteristics of membrane lipids.
Membrane lipids have two fatty chains, a polar group, and often a phosphate group, allowing them to self-associate into bilayers.
Explain the role of adipocytes in lipid storage.
Adipocytes are specialized cells that primarily store energy in the form of triglycerides.
What is the reverse process of triglyceride synthesis called?
The reverse process of triglyceride synthesis is called saponification.
Describe the two main types of lipids.
The two main types of lipids are hydrolyzable lipids, which can be broken down into smaller sections, and nonhydrolyzable lipids, which cannot be broken down into smaller sections.
How do different types of phospholipids arise?
Different types of phospholipids arise from various groups attaching at the phosphate location, such as serines, choline, and ethanolamine.
Describe the structure of Glycerophospholipids.
Glycerophospholipids have a glycerol backbone that forms ester linkages to two fatty acids and a polar head group.
Describe the concept of saturation in relation to phospholipids.
Saturation refers to the number of single bonds a carbon atom has with other molecules in phospholipids.
Define saturated fatty acids.
Saturated fatty acids have tails that only contain single bonds, allowing every carbon atom to bond with four other atoms.
How do saturated fatty acid tails interact with each other?
Saturated fatty acid tails form van der Waals interactions with other saturated fatty acid tails due to their symmetric and orderly nature.
What is the state of saturated fatty acids at room temperature?
Saturated fatty acids tend to be solid at room temperature due to their cohesive structure.
Explain the structure of unsaturated fatty acids. What is their state at room temperature?
Unsaturated fatty acids contain one or more double bonds, which introduce ‘kinks’ in the structure of the alkyl chain.
The kinks in unsaturated fatty acids make them less likely to stack and solidify, resulting in them being liquid at room temperature.
What is the melting temperature comparison between saturated and unsaturated fatty acids?
Saturated fatty acids have a higher melting temperature, while unsaturated fatty acids have a lower melting temperature.
How do waxes differ from other lipids in terms of cell membrane presence?
Waxes are not usually found in cell membranes, unlike many other types of lipids.
What is the relationship between fatty acids and fatty acid salts?
Fatty acid salts are unprotonated forms of fatty acids that associate with cations.
What type of solvents are lipids soluble in?
Lipids are soluble in organic solvents, which are carbon-based.
What drives the organization of lipids?
The organization of lipids is driven by their hydrophobic interactions.
Describe the hydrophobic effect in relation to nonpolar solutes.
The hydrophobic effect refers to the phenomenon where water molecules naturally order around nonpolar solutes. To reduce this ordering, water pushes nonpolar solutes together, which increases entropy.
Define amphiphilic lipids.
Amphiphilic lipids are molecules that have both a polar region and a nonpolar region, allowing them to interact with both polar and nonpolar environments.
