BSC 300 2023 TM_Lecture #7_Membrane Structure_In Class Lecture Slides

• Compartmentalization • Scaffold for biochemical activities • Selectively permeable barrier • Transporting solutes • Responding to external signals • Intercellular interaction • Energy transduction Each function plays a crucial role in maintaining cellular integrity and facilitating communication and energy management.

A model describing eukaryotic cellular membranes as dynamic structures composed of a fluid lipid bilayer with embedded proteins. This model emphasizes the flexibility and diversity of membrane components.

Membrane fluidity allows movement of proteins and lipids, assembly and growth of membranes, and adaptation to temperature changes. Membrane fluidity is crucial for cellular processes such as signal transduction and membrane fusion.

• Phosphoglycerides • Sphingolipids • Sterols Each type of lipid has unique structural properties and functions in membrane architecture.

Lipids with a glycerol backbone, two hydrophobic fatty acyl chains, and a polar head group linked by phosphate ester bonds. Phosphoglycerides are the most abundant lipids in cellular membranes.

Cholesterol enhances membrane fluidity and mechanical rigidity while preventing crystallization at physiological temperatures. Sterols are crucial for maintaining membrane integrity in various organisms.

Membrane asymmetry reflects different lipid compositions in the exoplasmic and cytosolic leaflets, affecting membrane function and properties. This asymmetry is essential for processes like cell signaling and membrane trafficking.

Proteins that penetrate and pass through the lipid bilayer, making up 20-30% of all encoded proteins. Integral proteins are often amphipathic, with hydrophobic regions anchoring them in the membrane.

Peripheral proteins are attached to the membrane by weak bonds and do not penetrate the lipid bilayer. They are typically associated with the membrane surface and can be easily solubilized.

Proteins that are attached to the membrane via lipid anchors, which can vary in type and orientation. Examples include GPI-linked proteins found on the outer leaflet.

• Glycoproteins: involved in cell interactions • Glycolipids: serve as recognition sites Carbohydrates are crucial for cellular communication and recognition.

The temperature at which lipids change from a liquid to a gel state, influenced by fatty acyl chain length and unsaturation. This property affects membrane fluidity and function.

Enzymes that catalyze the movement of lipids from the inner to outer leaflets of the membrane. Flippases play a key role in maintaining membrane asymmetry.

False Triglycerides are too bulky and not sufficiently amphipathic to form bilayers.

[vary significantly]

They provide a favorable environment for cell-surface receptors and GPI-anchored proteins. Lipid rafts are specialized regions enriched with cholesterol and sphingolipids.

• Phosphatidylcholine (PC) • Phosphatidylethanolamine (PE) • Phosphatidylserine (PS) • Phosphatidylinositol (PI) These head groups contribute to the diversity of phosphoglycerides.

Sphingolipids are derivatives of sphingosine and contain an amide bond connecting fatty acyl chains. This structural difference affects their function and properties within membranes.

The ability of organisms to adjust membrane fluidity in response to temperature changes. This adaptation is observed in poikilothermic organisms such as bacteria and cold-blooded animals.