University:
California State University, Northridge
Course:
BIOL 101 | General Biology
Academic year:

2024
Views:

263

Pages:

4
Author:

Skye S.

Chapter 1 : Cellular Biology Introduction to Pathophysiology Carbohydrates in Membranes ● Carbohydrates are associated with plasma membranes, forming glycolipids and glycoproteins ● Carbohydrates are mainly chemically combined with lipids and proteins Fluidity of Cell Membranes ● Cell membranes are not static and are always moving ● Protein-lipid interactions are important for correct insertion, folding, and orientation of membrane proteins ● Outer surfaces of plasma membranes contain invaginations called caveolae Lipids ● Lipid molecules are polar or amphipathic, meaning they have a hydrophobic part and a hydrophilic part ● The membrane consists of two layers of lipids due to the incompatible solubilities ● The hydrophobic region of lipids is protected from water, while the hydrophilic region is immersed in it ● The lipid bilayer acts as a barrier to water and hydrophilic substances, but allows lipid-soluble molecules to diffuse through ● The plasma membrane consists of glycerophospholipids, sphingolipids, and sterols, with phospholipids being the most abundant ● Phospholipids have a hydrophilic head connected to a hydrophobic tail and form self-sealing lipid bilayers ● Lipids, along with proteins, contribute to the structural integrity of the membrane ● Lipid rafts are distinct regions of the plasma membrane that are under investigation Proteins ● Proteins are made up of chains of amino acids (polypeptides) ● There are 20 types of amino acids in proteins, and each protein has a unique sequence of amino acids ● Posttranslational modifications (PTMs) diversify the limited number of proteins generated and alter their activity and functions ● Studies on proteomics aim to understand changes in proteins, analyzing their synthesis, translocation, modification, and roles in diseases ● Membrane proteins associate with the lipid bilayer in different ways, including transmembrane, monolayer-lipid linked, protein-attached, and protein-associated Membrane Proteins ● Membrane proteins can be classified as integral and peripheral membrane proteins ● Integral membrane proteins span across the lipid bilayer ● Peripheral membrane proteins are located on the surface of the lipid bilayer Protein Folding and Trafficking ● Proteins fold into complex three-dimensional structures ● Misfolded proteins can lead to disease and cell death ● Protein folding occurs in the endoplasmic reticulum (ER) ● ER stress can occur due to mutations, environmental toxins, or protein synthesis errors ● The unfolded-protein response (UPR) is activated to deal with misfolded proteins Functions of Membrane Proteins ● Membrane proteins play roles in recognition and binding of substances ● They act as pores or transport channels for ions and specific carriers for molecules ● Some membrane proteins are enzymes that drive active transport Components of the plasma membrane ● Phospholipids ● Cholesterol ● Proteins ● Carbohydrates Protein functions in the plasma membrane ● Transport of molecules ● Enzymatic activity ● Cell signaling ● Cell adhesion ● Catalysts of chemical reactions