Wednesday, September 23, 2015

Chapters 3.3 & 3.4& 3.5

Chapter 3.3 Cell membrane



Functions: contains cell contents, controls what enters and exits a cell


Fluid mosaic model: describes the arrangement of molecules that make up a cell membrane.


**The Membrane is flexible like a fluid and has a variety of molecules like the variety
 of tiles in a mosaic











                   













                                                           



Phospholipids: form a double layer surrounding a cell. 

charged/polar phosphate group, and glycerol

 no charge/non polar two fatty acid chains. 




head: hydrophilic (water loving) 



tails: hydrophobic (water fearing)





Other Molecules that make up the cell membrane: 

 cholesterol: strengthens membranes

proteins: help cell identification, movement of molecules across 

membranes and cell signaling, 

carbohydrates: aid cell identification  






Selective permeability/Semipermeable:allows some materials to

 cross; in order for cell to maintain homeostasis;






Receptors: detect a signal molecule and perform an action in response










ligand is a molecule that acts as a signal when it binds to a receptor. Can cross the cell membrane






Intracellular: located inside a cell; bind to molecules that can cross the membrane



Membrane : located in the membrane; binds to molecules than cannot cross the membrane;
change in shape transmits the message to the cell interior



















Diffusion & Osmosis 3.4




Passive transport: the movement of 

molecules across a membrane without

 energy input from the cell












Diffusion: movement of molecules from higher to lower concentration













Osmosis: the diffusion of water
















How do different solutions affect cells?


** hypertonic solution has a higher concentration of dissolved particles than a cell. This means water concentration is higher inside the cell than outside. Thus, water flows out of the cell, causing it to shrivel or even die.

**isotonic solution to a cell if it has the same concentration of dissolved particles as the cell.Water molecules move into and out of the cell at an equal rate, so the cell’s size remains constant.

**hypotonic solution has a lower concentration of dissolved particles than a cell. This means water molecules are more concentrated outside the cell than inside. Water diffuses into the cell. If too much water enters a cell, the cell membrane could potentially expand until it bursts.



Facilitated diffusionthe diffusion of molecules across a 

membrane through transport proteins; requires no energy input 

from the cell



Active Transport, Endocytosis & Exocytosis Chapter 3.5






           Membrane Transport Video HERE







**Active transport: drives 

molecules across a membrane 

from lower to higher 

concentration (against a 

concentration gradient) 

**Most active transport proteins use energy 


from  
the breakdown  

oATP (IS ENERGY)



ACTIVE & PASSIVE TRANSPORT RECAP








Endocytosis: process of taking in

liquids or larger molecules into a  

cell by engulfing in a vesicle; 

requires energy 


Exocytosis: process of releasing 

substances out of a cell by fusion of a vesicle 
with the membrane 

requires energy




Phagocytosis (cell eating):is a 

type of endocytosis in which the 

cell membrane engulfs large 

particles. 

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