Chapter 5.1 cell membranes Flashcards
What is the purpose of a membrane?
They separate cells from their external environment. allow cell to carry out its diverse functions
What are cell membranes made up of?
- Lipids
- protiens (imbedded or associated, preform functions such as transporting molecules)
- carbohydrates (usually attached to lipids (glycolipids) and proteins (glycoproteins)
What is the most common typeof lipid found in a cell membrane? and what is it made up of?
Phospholipid
- a glycerol backbone
- phosphate group (hydrophilic, polar, forms hydrogen bonds)
- 2 fatty acids (hydrophobic, non-polar no H bonds)
What is the scientific word(s) for a molecule that is
- water loving
- water fearing
- both water loving and water fearing
- hydrophilic
- hydrophobic
- amphipathic
in an aqueous solution, how do amphipathic molecules behave?
- they spontaneously arrange themselves into various structures.
- The polar head is located on outside to interact with water
- The non-polar fatty tails are faced in away from water.
What are the possible structure shapes a amphipathic molecule can form?
- micelle (bulky head and single fatty acid tail) aka soap
- bilayer (less bulky head and two hydrophobic tails)
- liposome (environments with a neutral pH)
What is the cell theory
- All organisms are made up of cells
-the cell is the fundamental unit of life
-cells come from preexisting cells
cells are defined by membranes
Why is pH important for a phospholipid bilayer?
insures that the head groups are in their ionized (charged) form and hydrophilic.
why do liposomes form?
if phospholipids are added to a test tube of water at neutral pH and the spontaneously form spherical bilayer structures.
why are liposomes most likely involved in early evolution?
- can form, break, re-form in environments
- can grow by incorporating more lipids
why are lipids able to move in the plane of the membrane?
- Freely associated with each other (van Der Waals forces) between fatty acid tails
- these weak interactions can easily break and reform
what determines membrane fluidity?
depends on which type of lipid makes up the membrane
- long fatty acid tails, saturated, are interactions, tighter packing = reduced lipid mobility
- short fatty acid tails, unsaturated, double bonds, reducing tightness of packing = enhancing lipid mobility.
What is another type of lipid that influences membrane fluidity?
Cholesterol
- major component of of animal cell membrane
- represent about 30% by mass of membrane
What are the similarities and differences between cholesterol and phospholipids
-both amphipathic
cholesterol
-hydrophilic region contains OH group
-hydrophobic region consists of four interconnected carbon rings with an attached hydrocarbon chain
How is cholesterol inserted into the lipid bilayer?
The cholesterols head interacts with the hydrophilic head group of phospholipids, while the ring structure participates in VdW interactions with the fatty acid chains.
