Biochemistry Chapter on Lipids

<p>Brown fat, which specializes in thermogenesis. (D)</p> Signup and view all the answers

<p>They act as long-term energy storage molecules. (B)</p> Signup and view all the answers

<p>They typically have an even number of carbon atoms. (A)</p> Signup and view all the answers

<p>Storing energy in the form of fat. (A)</p> Signup and view all the answers

<p>Providing chemical signaling through steroids. (C)</p> Signup and view all the answers

<p>The pro-S carbon is assigned as C1. (A)</p> Signup and view all the answers

<p>Hexosaminidase A (D)</p> Signup and view all the answers

<p>Ceramides (B)</p> Signup and view all the answers

<p>It decreases fluidity by reducing unsaturated bonds. (D)</p> Signup and view all the answers

<p>They are associated with one side of the bilayer. (A)</p> Signup and view all the answers

<p>Glycosphingolipids possess a hydrophobic tail derived from sphingosine. (C)</p> Signup and view all the answers

<p>It portrays membranes as a mixture of lipids and proteins that can move fluidly. (B)</p> Signup and view all the answers

<p>Sphingosine (B)</p> Signup and view all the answers

<p>The movement of chains becomes more dynamic. (B)</p> Signup and view all the answers

<p>Longer saturated tails tend to increase the Tm. (A)</p> Signup and view all the answers

<p>It broadens the transition without changing the transition temperature. (B)</p> Signup and view all the answers

<p>6 nm (D)</p> Signup and view all the answers

<p>Lipids can move more freely than in a solid state. (A)</p> Signup and view all the answers

<p>Outer and inner leaflets usually differ in lipid composition. (D)</p> Signup and view all the answers

<p>The proteins gradually mix over the fused surface. (C)</p> Signup and view all the answers

<p>Two separate lamellar phases. (B)</p> Signup and view all the answers

<p>Functions as a light driven proton pump (B)</p> Signup and view all the answers

<p>A single, highly hydrophobic transmembrane helix (C)</p> Signup and view all the answers

<p>It facilitates the passage of protein segments through the lipid bilayer (B)</p> Signup and view all the answers

<p>The alignment of transmembrane helices with their ends in the cytoplasm (A)</p> Signup and view all the answers

<p>Phosphatidylinositol (D)</p> Signup and view all the answers

<p>They insert into the membrane while still being synthesized (C)</p> Signup and view all the answers

<p>It allows nascent peptides to access the membrane core (A)</p> Signup and view all the answers

<p>Small, polar residues (A)</p> Signup and view all the answers

<p>Facilitating rapid water transport (C)</p> Signup and view all the answers

<p>Tetramer of identical monomers (B)</p> Signup and view all the answers

<p>Helical conformation (C)</p> Signup and view all the answers

<p>The geometry of chelating groups in ion channels (D)</p> Signup and view all the answers

<p>N-terminal Asn-Pro-Ala (A)</p> Signup and view all the answers

<p>Electrostatic repulsion due to dipoles (C)</p> Signup and view all the answers

<p>Faster transport of water molecules (D)</p> Signup and view all the answers

<p>10 nm in diameter and 10 nm in length along the sevenfold axis (A)</p> Signup and view all the answers

<p>Formation of a coated pit (D)</p> Signup and view all the answers

<p>Concentration of K+ ions (B)</p> Signup and view all the answers

<p>To insulate the axon with myelin (B)</p> Signup and view all the answers

<p>Voltage-gated channels open allowing ion flow (D)</p> Signup and view all the answers

<p>They contain numerous Na+ ion channels (C)</p> Signup and view all the answers

<p>Caveolae (A)</p> Signup and view all the answers

<p>Through changes in membrane potential (A)</p> Signup and view all the answers

<p>60 mV (C)</p> Signup and view all the answers

Lipids are a class of biological molecules that are insoluble in water but can form water-soluble structures like micelles, vesicles, and bilayers.

Fatty acids are the simplest lipids, composed of a hydrophilic carboxylate group attached to a hydrophobic hydrocarbon chain.

Saturated fatty acids have carbons in their tail that are fully saturated with hydrogen atoms. They are typically straight and solid at room temperature.

Unsaturated fatty acids have one or more double bonds in their tail. They are typically liquid at room temperature.

Membrane lipids are amphipathic, meaning they have both hydrophilic and hydrophobic parts. This allows them to form structures like micelles and bilayers in water.

Triacylglycerols are esters of fatty acids and glycerol. They are the major long-term energy storage molecules in many organisms.

Fat storage in animals serves three primary functions: energy production, heat production, and insulation.

Adipocytes are specialized cells responsible for storing fat in animals. They are found in adipose tissue.

Glycerol is a molecule that can exist in two mirror-image forms, but in its natural state, it is neither. Phosphorylation of one of its CH2OH groups creates a chiral molecule, resulting in either the R or S enantiomer of glycerol phosphate.

The sn (stereochemical numbering) system assigns C1 to the pro-S carbon of glycerol. All glycerophospholipids are derivatives of sn-glycerol-3-phosphate.

Sphingolipids are a class of lipids derived from sphingosine, an amino alcohol with a long-chain hydrophobic tail. They are found in cell membranes and play crucial roles in cell signaling and recognition.

Ceramides are a type of sphingolipid formed when a fatty acid is linked to the amino group (NH2) of sphingosine through an amide bond. This structure gives them hydrophobic and hydrophilic properties.

Sphingomyelin is a type of sphingolipid where a phosphocholine group is attached to the C-3 hydroxyl of ceramide. It is a major component of myelin sheaths, which insulate nerve cells.

Glycosphingolipids are sphingolipids with sugar groups attached to the C-1 hydroxyl of ceramide. They play a vital role in cell recognition and signaling.

Monogalactosyl diglyceride is a type of glycoglycerolipid found in plant and bacterial membranes. It has a single galactose sugar attached to a diglyceride molecule.

Cholesterol is a type of lipid that plays a vital role in regulating membrane fluidity. Its rigid structure helps maintain the structural integrity of cell membranes.

A pore-forming protein that allows the rapid transport of water across cell membranes.

A conserved sequence found in aquaporins that is involved in water passage.

Aquaporins function as tetramers, meaning they are composed of four identical monomers.

The narrowest part of the aquaporin channel, where the two NPA-containing helices meet.

Aquaporins prevent the passage of protons (H+) due to the electrostatic barrier created by charged amino acids.

The inherent permeability of membranes to water is not sufficient to support rapid transport in many cells.

Erythrocytes, secretory cells, and epithelial cells all require rapid water transport for their function.

A helical antibiotic that forms a pore through cell membranes, allowing ions to cross.

A type of phospholipid with choline as its head group. Commonly found in cell membranes.

A type of phospholipid with ethanolamine as its head group. Important for membrane structure and signaling.

A type of phospholipid with serine as its head group. Found in the inner leaflet of cell membranes.

A type of phospholipid with inositol as its head group. Plays a crucial role in cell signaling pathways.

A type of sphingolipid with phosphocholine as its head group. Abundant in the myelin sheath of nerve cells.

A light-driven proton pump found in certain bacteria. It is a transmembrane protein with seven helices spanning the membrane.

A protein that was the first integral membrane protein to be sequenced. It has a single transmembrane helix and carries oligosaccharides.

A protein channel that facilitates the insertion of integral membrane proteins into the membrane bilayer.

The cell membrane is a thin, flexible barrier that encloses the cell and regulates what enters and exits. It consists of a phospholipid bilayer with embedded proteins.

These are proteins embedded within the phospholipid bilayer of the cell membrane, playing various roles in functions like transport, signaling, and anchoring.

The cell membrane is composed of two layers of phospholipid molecules arranged with their hydrophilic heads facing outwards and their hydrophobic tails facing inwards.

The fluid mosaic model describes the cell membrane as a dynamic structure with a flexible phospholipid bilayer and embedded proteins that can move laterally.

The change in temperature affects the fluidity of the membrane. When the temperature is lowered, the phospholipid tails become more packed, making the membrane more rigid. Conversely, increasing the temperature leads to increased fluidity.

Cholesterol is embedded within the phospholipid bilayer of the membrane and plays a role in maintaining fluidity and stability.

The two layers of the membrane are often asymmetrical, meaning they have different lipid compositions. This asymmetry is important for maintaining cell function and signaling.

The transition temperature (Tm) for a membrane is the temperature at which it changes from a gel-like state to a liquid-like state. It is influenced by factors such as the length and saturation of fatty acid tails in the phospholipids.

Sugars are modified by adding a phosphate group either during transport across the membrane or immediately upon entering the cell's cytosol.

The process of moving substances across cell membranes involves specialized transport systems that ensure specific directions and movement of molecules.

A mechanism for transporting large molecules or groups of molecules across cell membranes. This process involves the formation of small, membrane-bound sacs called vesicles. Two types of vesicle formation involve clathrin and caveolae.

Clathrin-coated vesicles are formed by invagination of the plasma membrane, where a coated pit emerges, buds off, and ultimately forms a free vesicle.

Caveolae formation occurs at specific sites within the cell membrane, rich in cholesterol and sphingolipids. This process involves the insertion of caveolin protein, which causes the membrane to fold, forming a pouch that ultimately buds off as a caveola.

Neurons use changes in membrane potential to transmit electrical impulses. These changes occur in specific regions of the neuron's plasma membrane.

The axon is a long, slender projection of a neuron that transmits signals away from the cell body. The axon terminates in synaptic termini, which are specialized structures responsible for communication with other neurons or muscle cells.

Schwann cells are specialized cells that wrap around the axon, forming a myelin sheath. Myelin is an insulating layer that speeds up the conduction of electrical signals along the axon. The gaps between Schwann cells are called nodes of Ranvier.