Biochem 9.2 Introduction to Structural Lipids

Lipids that possess both a hydrophobic and a hydrophilic region.

A spherical structure formed by amphiphilic molecules in an aqueous environment. The hydrophobic tails point inwards, while the hydrophilic heads face outwards.

A single layer of amphiphilic molecules with their hydrophobic tails facing outwards and hydrophilic heads facing inwards.

A double layer of amphiphilic molecules with hydrophobic tails facing each other and hydrophilic heads facing outwards. It forms the basis of biological membranes.

A type of phospholipid that is derived from glycerol. It consists of a glycerol backbone, two fatty acid chains, and a phosphate group.

A type of phospholipid that is derived from sphingosine. It consists of a sphingosine backbone, one fatty acid chain, and a phosphate group.

The hydrophobic portion of a glycerophospholipid, formed by the two fatty acid chains attached to the glycerol backbone.

The hydrophilic portion of a glycerophospholipid, formed by the phosphate group and its associated head group.

Glycolipids are formed when a carbohydrate group is added to a lipid head group, like phosphatidylinositol (PI). This creates a molecule with both lipid and carbohydrate components.

Glycosylphosphatidylinositol (GPI) is a specific type of glycolipid that can anchor proteins to cell membranes. The protein is permanently attached through a lipid link.

Sphingolipids are a type of membrane lipid with sphingosine as their backbone, unlike glycerophospholipids which use glycerol.

Ceramides are sphingolipids with a simple -H group as their head group. They are characterized by an amide bond connecting sphingosine to a fatty acid.

Sphingomyelins are zwitterionic sphingolipids with phosphocholine or phosphoethanolamine as their head group. They are commonly found in the myelin sheath of neurons.

Glycosphingolipids are sphingolipids with carbohydrate head groups. They can be simple monosaccharides, complex oligosaccharides, or even polysaccharides like gangliosides.

Cerebrosides are glycosphingolipids with a single monosaccharide as their head group.

Gangliosides are glycosphingolipids with complex polysaccharides containing sialic acid derivatives as their head group.

Long chains of carbon atoms (14-24) found in membrane lipids; may be saturated (no double bonds) or unsaturated (at least one double bond).

The level of saturation affects the fluidity of the membrane. Unsaturated fatty acids with double bonds create kinks, making the membrane more fluid. Saturated fatty acids with no double bonds are more tightly packed, making the membrane less fluid.

The head group of a glycerophospholipid is composed of a phosphate group attached to a variable R' group. This determines the overall charge of the head group (zwitterionic or negative).

A molecule with an equal number of positive and negative charges, resulting in a net neutral charge.

Phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are glycerophospholipids with zwitterionic head groups. They have positively charged amine groups (primary or quaternary) that cancel the negative charge of the phosphate group.

Phosphatidylglycerol (PG) and phosphatidylinositol (PI) have neutral R' substituents, making their head groups negatively charged. Phosphatidylserine (PS) also has a negative head group due to its negatively charged phosphate group and zwitterionic but overall negative R' substituent.

The phospholipid head groups can be categorized based on their net charge. Some head groups are zwitterionic (neutral) while others are negatively charged.

A type of lipid with a long-chain fatty acid attached to a long-chain alcohol, serving as a protective coating for skin and hair in humans and for energy storage in other organisms.

Spherical structures formed by amphiphilic molecules like fatty acids in an aqueous solution, with hydrophobic tails facing inward and hydrophilic heads outward.

A single layer of amphiphilic molecules, typically phospholipids, with hydrophilic heads facing the aqueous environment and hydrophobic tails facing away.

A double layer of phospholipids, with hydrophobic tails facing inwards and hydrophilic heads facing outwards on both sides, forming a barrier between two aqueous compartments.

Lipid bilayer membranes selectively allow certain molecules to pass through while restricting the movement of others. Small hydrophobic molecules can pass through, while hydrophilic molecules need special mechanisms.

The process by which a lipid aggregate is enclosed within a phospholipid monolayer, eliminating the need for a highly ordered solvation layer.

A type of lipid with a four-ringed structure, essential for membrane fluidity and precursor for various steroid hormones.

A specific type of sphingolipid with a phosphocholine head group, found in abundance in myelin sheaths and involved in signal transduction.

The ability of individual lipid and protein molecules to move laterally within a membrane bilayer.

The movement of a membrane component from one leaflet of the bilayer to the other (inner to outer or outer to inner).

Membranes are asymmetric because lipids and proteins cannot freely flip between leaflets. For example, a phospholipid on the outer leaflet cannot easily move to the inner leaflet.

The ability of a membrane to maintain its fluidity and flexibility, essential for proper function.

External temperature affects membrane fluidity. Higher temperatures increase fluidity, while lower temperatures decrease fluidity.

Cells adjust membrane fluidity by changing lipid composition. Saturated fatty acids decrease fluidity, while unsaturated fatty acids increase fluidity.

The strength of intermolecular forces between membrane components influences fluidity. Stronger forces lead to less fluidity.

Membranes must balance rigidity and flexibility. Too rigid, and the membrane breaks. Too fluid, and the membrane leaks.

The strength of interactions between molecules in a membrane, primarily due to London dispersion forces between phospholipid tails.

The longer the phospholipid tail, the stronger the London dispersion forces between them, leading to increased viscosity and reduced membrane fluidity.

Unsaturated fatty acids contain double bonds in their carbon chains, creating kinks and reducing packing efficiency, thus increasing membrane fluidity.

A steroid molecule that acts as a buffer for membrane fluidity, preventing drastic changes in fluidity from temperature.

Self-assembly of specific membrane components, primarily lipids and proteins, into localized regions within a cell membrane leaflet.

The ability of membrane components to move laterally within the plane of the membrane, creating a dynamic system.

The ability of cells to adapt to changes in temperature by altering the composition of their membranes to maintain optimal fluidity.

The term 'phospholipid' often refers to glycerophospholipids, which are common components of biological membranes. They have a glycerol backbone, two fatty acids, and a phosphate group.

Glycerophospholipids have two 'tails' formed by the hydrophobic fatty acid chains, which are attached to the glycerol backbone. These tails make up the hydrophobic part of the molecule.

The phosphate group and its associated head group form the hydrophilic 'head' of a glycerophospholipid. This head group is responsible for the molecule's water-loving properties.

The structure of a glycerophospholipid makes it 'amphipathic', having both hydrophilic and hydrophobic regions. This property allows it to form membranes, with the heads facing the water and the tails facing inward.

The most common phospholipid in membranes is the phospholipid phosphatidylcholine (PC). It has a zwitterionic head, which means it has a neutral overall charge despite having both positive and negative charges within the group.

The length of the fatty acid tails in membrane lipids affects the fluidity of the membrane. Longer tails result in stronger London dispersion forces between them, leading to increased viscosity and reduced fluidity.

Unsaturated fatty acids, containing double bonds in their carbon chains, create kinks that disrupt tight packing in the membrane. This increases the overall fluidity of the membrane.

Cholesterol acts as a fluidity buffer in membranes. It prevents drastic changes in fluidity caused by temperature fluctuations by interacting with phospholipid tails to adjust membrane packing.

The presence of different head groups on phospholipids creates a diversity of function and behavior. These head groups can be zwitterionic (neutral) or negatively charged, influencing membrane interactions and signaling.

The saturation of fatty acid tails in membrane lipids influences membrane fluidity. Unsaturated tails with double bonds create kinks that make the membrane more fluid, while saturated tails without double bonds pack tightly, reducing fluidity.