CELL MEMBRANEs and TRANSPORT Lecture 2 Cell Biology (BWD10103)

What can I actually learn from this topic?

Roles of the cell membrane & its components within

Many holes Flexible, not 1 piece but many tiny pieces 2 important components of cell membrane are: Protein and phospholipids Phospholipids make up the bags Proteins the holes

Lipid Bilayer - 2 layers of phospholipids Hydrophilic (water loving) tails bump up against each other heads are facing the watery surroundings of the cell Hydrophobic (water hating)

Fluid Mosaic Model of the cell membrane S.J. Singer and G.L. Nicolson (1972) – developed the Model FLUID- because individual phospholipids and proteins can move around freely within the layer, like liquid MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above

Mosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials

The structure allows it to be selective!! Important functions of the cell membrane selective permeability allows to regulate what enters and exits the cell, thus facilitating the transport of materials needed for survival. membranes facilitate the synthesis of ATP through chemiosmosis The structure allows it to be selective!!

Cell resting potential??? When the ions in the inside of the membrane relative to the outside Basically more Na+ outside and more K+ inside

How do molecules get in and out of the cells (cross cell membranes)???

Types of Cellular Transport Passive Transport – cell doesn’t use energy to get in Active Transport – cell needs energy to enter

Passive? Active ?

cell uses no energy molecules move randomly molecules spread out from an area of high concentration to an area of low concentration there are 3 types

Facilitated diffusion Passive transport Diffusion osmosis Facilitated diffusion

Facilitated diffusion Passive transport Diffusion osmosis Facilitated diffusion

Diffusion Diffusion: random movement of particles from an area of high concentration to an area of low concentration Diffusion continues until equilibrium (all molecules are evenly spaced) is achieved Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm

Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) diffusion of specific particles through transport proteins found in the membrane Transport Proteins are specific – they “select” only certain molecules to cross the membrane Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein http://bio.winona.edu/berg/Free.htm

Osmosis diffusion of water through a selectively permeable membrane Water moves from high to low concentrations Water moves freely through pores Ion concentrations is the same on both sides of the cell membrane

cell uses energy actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration there are 3 types

Active transport Protein pumps Endocytosis Exocytosis

Active transport Protein pumps Endocytosis Exocytosis

Protein pumps proteins do much of the work in active transport use cellular energy (usually ATP) to actively pump substances Sodium Potassium Pumps

Endocytosis transport where large amounts of material are brought into a cell cell membrane enfolds/engulf the particle forms food vacuole & digests food

Exocytosis transport in which large amounts of material are moved out of a cell membrane surrounding the material fuses with cell membrane particles are released outside cell

Endocytosis vs Exocytosis

Translocation special type of active transport facilitate the delivery of various molecular cargoes to the cytoplasm or an organelle normally done by plants; specialized in animals

translocation in plants The process by which products of photosynthesis (sucrose and other organic materials) are transported to different tissues of the plant takes place in the phloem and follows a pattern of "source to destination”

3 mechanisms of membrane translocation Direct Penetration Endocytosis mediated Translocation Translocation Through the Formation of a Transitory Structure

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