Biochemistry Membranes

Biochemistry – Membranes

General Properties Fluid Mosaic Phospholipid bilayer GLYCEROL Fluid Mosaic Phospholipid bilayer Selectively Permeable Asymmetric Outer and inner leaflet Lipid + protein + cholesterol + CHO Amphipathic(hydrophillic and hydrophobic) NO  Yes NAM SM PC Sphingosine L V Choline

Lipid + Protein + Cholesterol Lipids Phospholipids, NOT TAGs Lecithins such as Phosphatidylcholine (outer leaf) Sphingomyelin (outer leaf, has choline!) Gangliosides (lipid with sugar) N-acetylneuraminic acid Proteins Peripheral = on periphery Integral = goes all the way through membrane Leucine and valine are found on interior of globular proteins(nonpolar, hydrophobic aa) Cholesterol Most abundant non-phospholipid component of membrane CHO Attached to lipids(gangliosides) and proteins GS SM NAM Sphingosine L V Choline

Types of movement Passive Diffusion(uses no energy, -ΔG) Simple diffusion (if water, osmosis) Facilitated diffusion (mediated diffusion) Swimming downstream Active transport (uses energy +ΔG) Primary active transport Secondary active transport Swimming upstream NOTE: delta G = gibbs free energy -ΔG = spontaneous +ΔG = not spontaneous

Selectively permeable No = large and charged Need protein transport systems to move across Yes = small, nonpolar, uncharged Steroids, crol is nonpolar

Types of movement 1. Simple diffusion (if water, osmosis) Facilitated diffusion (mediated diffusion) Primary active transport Secondary active transport Simple Diffusion Facilitated Diffusion Active Transport No nrg With gradient Protein transporter

Simple Diffusion No energy Movement from high to low concentration Down gradient Aka With the gradient Swimming downstream Penetrating solutes Go through with no help

Facilitated Diffusion No energy used Down gradient Non-penetrating solutes Need help Uses proteins Saturation kinetics of binding sites [High solute], all binding sites used up (enzyme lecture)

Simple diffusion vs facilitated diffusion Energy used Protein transporter Solutes Saturation kinetics Simple Diffusion No, down gradient no penetrating Facilitated diffusion yes Non-penetrating

Simple Vs Facilitated Diffusion How is simple diffusion different than facilitated diffusion? Facilitated involves saturation kinetics How is facilitated diffusion different than active transport? Facilitated diffusion requires a concentration gradient. Active transport doesn't’t, can just use ATP What is similar between facilitated diffusion and active transport Saturation kinetics and competitive inhibition

Primary Active Tport Sodium potassium ATP pump(NaKA) Against gradient Up gradient Directly uses ATP Gain in free energy

Secondary Active Tport Indirectly uses ATP Aka cotransport aka countertransport Against the gradient Binding kinetics Gain in free energy

+ΔG Passive Transport Active Transport -ΔG Simple Diffusion Facilitated Diffusion Primary AT Secondary AT Osmosis Channel Proteins Carrier Proteins AKA Cotransport