Chapter 12 Membrane Structure and Function Flashcards
What is the membrane structure like and what does it form?`
It has sheetlike structures, two molecules thick and those form closed boundaries
What are membranes composed of?
Lipids and Proteins and either of them can be decorated with carbs
What are membrane lipids and what do they form and what is the purpose of them?
They are small Amphiathic molecules that form closed molecular sheets and helps prevent the movement of polar or charged membrane
Membranes are _________________ assembiles
Noncovalent
Membranes are ____________ in that the outer surface is always different from the inner surface
Asymmetric
Membranes are ___________ structures
Fluid
Most cell membranes are ____________________ such that the ____________ is negative
Electrically polarized , Inside
What is the formation of membranes powered by?
Hydrophobic effect
If two non polar molecules are next to each other in water, what will happen if you combined both of them
The entropy would increase
What type of lipids form the lipid bilayer in aqueous solution?
Phospholipids and Glycolipids
What is a liposome and what do we use them for?
They are aqueous compartments enclosed by a lipid membrane. Liposome is a used as a drug delivery system, so its more targeted and it means less of the body is exposed to potentially toxic drugs.
Why are lipid bilayers highly impermeable to ions and most polar molecules?
Its because there is an energy cost for ions and polar molecules as they have to shed water so they can cross the lipid bilayers.
What happens to the membrane transition at the melting temperature?
It goes from being highly ordered to very fluid
What is melting temperature dependent on ?
It is dependent on the length of the fatty acids in the membrane and the degree of cis unsaturation.
In animals, what helps maintain proper membrane fluidity in membranes?
Cholesterol
What happens to the fatty acid chains if there is an unsaturated fatty acid in there?
A kink or a bump forms in the structure to show the unsaturated fatty acid
What is the role of a membrane protein ?
It helps with transport of molecules and information across the membrane
Where are the integral membrane proteins embedded ?
In the Hydrocarbon core of the membrane
Where are the Peripheral membrane proteins bound to ?
They are bound to the polar head groups of membrane lipids or to the exposed surfaces of integral membrane proteins
What are Hydrophobic moeitys function?
It is another way some proteins associate with membranes, this is an attachment that is inserted into the membrane
What is a common structural feature of integral membrane proteins?
The membrane spanning alpha helices
What other ways can you embed an integral membrane protein?
By using Beta strand to form a pore in the membrane or by embedding part of the protein into the membrane
What is the COX activity of prostaglandin H2 synthase-1 dependent on?
A channel connecting there active site to the membrane interior
How does the Aspirin inhibit COX activity?
By obstructing the channel
What does the FRAP technique used for?
It allows the measurement of lateral mobility of membrane components
What is the lateral diffusion of proteins dependent on?
Whether they are attached to other cellular or extracellular components
Transverse diffusion is very rare without the assistance of _____________
Enzymes
A small molecule will spontaneously cross a membrane if what two conditions are met?
1.The concentration of the molecule is higher on one side of the membrane than the other
2.The molecule is lipophilic or soluble in non polar solutions
Polar molecules can diffuse with the assistance of a particular channel and such movement is called____________
Facilitated diffusion or Passive transport
What is active transport?
It is a movement of molecules against a concentration gradient requires a source of energy
What is a transport protein?
It is a pump or channel that facilitate the flow of small molecules across the cell membrane
The Na and K ATPase uses the energy of ____________________ to simultaneously pump _________ Na ions out of the cell and _________ K ions into the cell against their concentration gradients
ATP hydrolysis, Three, Two
What is a Symporter
It is a transport of molecule against its concentration gradient by coupling the movement to the movement another molecule down its concentration gradient with both molecules moving in the same direction.
What is an antiporter?
It uses one concentration gradient to power the formation of another but the molecules move in opposite directions.
What is a tetrodotoxin?
It is a lethal inhibitor of the Na channel produced by the pufferfish
Why are larger ions not transported through the channel
because they are too big to enter
