2026-08-17 11:43:30: Plasma Membrane

biology/Cell Structure and Function/Plasma Membrane.md

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+[[Cell Structure and Function]]
+
+# Summary
+* Phospholipids are amphipathic (both hydrophobic and hydrophilic): hydrophilic phosphate heads point towards water hydrophobic fatty acid tails point away.
+* Embedded proteins have hydrophilic regions facing the cytosol or extracellular fluid. Also have hydrophobic regions that contact the fatty acid tails in membrane interior.
+* Cholesterol (in vertebrate animals) acts as a fluidity buffer, preventing the membrane from getting too loose or stiff in head or cold.
+* Fluid mosaic model describes a membrane with phospholipids, proteins, cholesterol, glyco(proteins/lipids) can move around the surface.
+* Fatty acid affects fluidity, unsaturated with kinks increases it, while saturated makes the phospholipids pack tightly together.
+* Glycoprotein and glycolipid sit on the outside and help with cell recognition.
+
+Plasma membrane defines the edge of every cell, it's not a wall and is flexible.
+# Components of the Plasma Membrane
+
+Phospholipids are main structural framework as a bilayer. Hydrophobic fatty acid tails point away from aqueous environment, hydrophilic phosphate heads point towards.
+
+Steroids (cholesterol in vertebrates) restrain phospholipid movement at high temps and prevents them from packing tightly at low temps.
+
+Gylco(proteins/lipids) are carbohydrates, attached to proteins and lipids, helps cells recognize each other.
+
+# Fluid Mosaic Model
+Describes the plasma membrane as structural framework of phospholipids embedded with proteins, steroids(cholesterol) and glyco(steroids/lipids). Describes them as being able to move freely.
+
+Fluid nature, phospholipids can move laterally like they're in a sea of lipids. Allows components to shift and form regions for different jobs.
+
+Variety of molecules creates a mosaic appearance, thus the name.
+
+# Factors Affecting Membrane Fluidity
+* Temp
+* Fatty acid composition (look below)
+* Cholesterol content (look above)
+# How Structure Connects to Function
+Hydrophobic interior blocks polar molecules while allowing small non-polar molecules pass more freely. Basis for selective permeability.
+
+Embedded proteins allow for specific interactions. Receptor proteins bind to signaling molecules, transport proteins move them.