Ch. 8 Membrane Structure and Function An Overview of the Plasma Membrane and Cell Transport

Membrane Structure _________________ Model Phopholipids are _______________

Membrane Structure Fluid Mosaic Model Phospholipid bilayer with embedded or attached proteins Phopholipids are amphipathic Nonpolar tails = hydrophobic Polar heads = hydrophilic

Figure 8.1 Artificial membranes (cross sections) Either in one or two layers, the hydrophobic tails of the phospholipids will automatically arrange themselves to not face the water. Think about what happens when you try to mix oil and water.

Proteins are scattered in two layers of phospholipids. Proteins can be ___________ or ___________. These proteins can have various functions

Proteins are scattered in two layers of phospholipids. Proteins can be integral or peripheral. These proteins can have various functions

Some functions of membrane proteins Pg. 144 in text

Figure 8.9 Some functions of membrane proteins Pg. 144 in text

Figure 8.9 Some functions of membrane proteins Pg. 144 in text

Figure 8.9 Some functions of membrane proteins Pg. 144 in text

Figure 8.6 The detailed structure of an animal cell’s plasma membrane, in cross section

Membranes are Fluid Phospholipids and some proteins can move laterally very rapidly Flip-flopping is rare – why?!? Other conditions can influence membrane fluidity Temperature, unsaturated vs saturated fatty acids, cholesterol

Figure 8.4 The fluidity of membranes

Traffic Across Membranes Membranes are _______________ What kind of molecules cross easily?

Traffic Across Membranes Membranes are semi-permeable small, hydrophobic molecules cross with ease ex. CO 2 and O 2 some ions and polar molecules are also permeable through protein channels ex. Ion channels and aquaporins

Passive vs. Active Transport Passive – Active –

Passive vs. Active Transport Passive – no energy input required down concentration gradient includes simple diffusion, osmosis, and facilitated diffusion Active – energy input required Against concentration gradient Ex. Sodium/potassium pump pg. 149

Figure 8.16 Review: passive and active transport compared

Figure 8.14 Two models for facilitated diffusion Facilitated diffusion requires the help of an _______________, but requires ____________. Proteins can form a _________ or ________ _______________ when stimulated by a solute.

Figure 8.14 Two models for facilitated diffusion Facilitated diffusion requires the help of an integral protein, but requires no energy. Proteins can form a channel or change conformations when stimulated by a solute.

Figure 8.15 The sodium-potassium pump: a specific case of active transport

Figure 8.10 The diffusion of solutes across membranes

Solute passively moves from high to low concentration. Examples? Why do cells have to be small?

The goal is to make the ________________________ equal on each side…if the _______ can’t move, the __________ will…from an area of _____ water concentration to _______ water concentration…in other words, from the __________ to ____________ solution

The goal is to make the concentration of the solute equal on each side…if the solute can’t move, the water will…from an area of high water concentration to low water concentration…in other words, from the hypotonic to hypertonic solution

Terms hypotonic, isotonic, and hypertonic compare two solutions on the basis of _______________________

Terms hypotonic, isotonic, and hypertonic compare two solutions on the basis of solute concentration