Terms in this set (34)
What type of molecules pass easily through the phospholipid bilayer of the membrane?
Smaller, nonpolar molecules
Give three examples of molecules that easily pass through the membrane.
Smaller lipids, steroids, oxygen, and carbon dioxide
What provides most of the membrane function?
The proteins embedded in the phospholipid bilayer. (Proteins = action molecules)
What provides most of framework of the plasma membranes?
What does not pass easily through the membrane?
Larger, charged (polar) and ionic molecules
Give examples of molecules that don't pass easily through the membrane.
Water, glucose- polysaccharides, proteins- amino acids and NaCl
Do all plasma membrane have the same permeability?
What determines different permeability's?
Different types of transfer proteins (protein channel).
-saturated and unsaturated
-Unsaturated fatty acids are liquid at room temperature and therefore will be more liquid- more permeable.
-Saturated fatty are solid at room temperature and therefore less permeable.
*Ratio of unsaturated to saturated fatty acids in phospholipid molecules helps determine permeability. The more unsaturated, the more permeable.
What is the function of the membrane?
-It serves as a boundary between life and non-life.
-It regulates what enters and exits the cell.
-It defines the boundary of the cell.
-It controls the flow of water and it is selectively permeable.
-It is part of the endomembrane system.
-It helps maintain homeostasis of the cell.
Describe the four types of membrane proteins.
-Attached to either the outer or inner surface of the membrane.
**Does not go into the membrane.
-Penetrate into bilayers either partially or completely through the membrane.
-Very specific and determine the permeability of the membrane.
-Carry out the chemical reactions.
-Receive messages from other cells and sends messages to nucleus - gene is either turned on or off. The signal molecule is a hormone.
-Proteins with a carbohydrate attached. They act as name tags or recognition proteins. (Causes troubles in transplants- reject bc different glycoproteins)
Structure of Plasma Membrane-
The plasma membrane is a phospholipid bilayer made of phospholipids with a polar, hydrophilic phosphate head and nonpolar, hydrophobic fatty acids as tails.
The hydrophilic heads face outwards while the hydrophobic tails face inwards away from the water. Proteins are embedded in the plasma membrane.
More "need to know"
-In ANIMAL cells cholesterol is found between phospholipid molecules.
-Cholesterol stabilizes the membrane. Cholesterol prevents phospholipids from spreading apart. When too cold, cholesterol prevents phospholipids from getting too close.
Fluid Mosaic Model-
The mosaic component refers to the protein embedded in the phospholipid bilayer.
Fluid- the membrane is not completely solid.
Within a layer, phospholipid molecules and proteins can move.
Gives the membrane a fluid like quality (ping pond balls in a bucket of water).
Membranes are selectively permeable: They don't allow everything to enter or leave. It determines what should enter of leave the cell.
What provides framework of plasma membrane?
A phospholipid bilayer.
How are phospholipid molecules arranged?
Arranged in two layers with the phosphate heads in both layers face outward towards the water on the inside and outside of the cell.
What provide different functions of the membrane?
The proteins embedded in the phospholipid bilayer.
How are proteins embedded in membrane?
-attached to either the outer or inner surface
-penetrated into the bilayer partially or completely through and through.
Membranes around organelles accomplish what for cells?
It helps to compartmentalize the (eukaryotic) cell.
Why is compartmentalization beneficial for cells?
Creates little rooms where separate functions/chemical reactions can be carried out simultaneously.
Why do membranes have different selective permeability's?
Different transport proteins are found in different membranes as well as different types of fatty acids in phospholipid molecules in different membranes (ratio between saturated and unsaturated).
What is permeable to the membrane & why?
Carbon dioxide, oxygen and steroids because membrane is mostly lipid and they are all lipid soluble (not polar or ionic).
What is non permeable to membrane & why?
Glucose, water, amino acids and ions. They are polar or ionic or too big to pass through the membrane.
How do non-permeable substances enter or leave the cell?
Through the protein pores or channels.
What are four functions of membrane proteins?
Enzymes, receptors, name tags (glycoproteins), transportations
Where is cholesterol found?
In between the phospholipid molecules in animal cell membranes (not plant).
What is the function of cholesterol?
Stabilizes membrane by making it less fluid when hot and less solid when cold.
Why is the membrane called a fluid Mosaic?
The proteins are embedded onto a canvas of lipids created a mosaic appearance.
The proteins and phospholipid molecules can move within their layer creating a fluid or flow like quality to the membrane.