Bio130: Section 2 Flashcards
What is special about saccharomyces cerevisiae?
It is an eukaryotic cell yet has a cell wall
What is ECM and who has it?
ECM is extracellular matric and animal cells have it while other organisms don’t. It is specialized material outside of the cell.
What are lysosomes?
they are organelles that function to degrate cellular components that are no longer needed.
What is Cytoplasm
Everything outside the nucleus including the organelles with the exception of the nucleus, includes ribosomes, and the cytoskeleton
What is cytosol?
It is the aqueous part of the cell, doesn’t include the membrane-bound organelles. Does include ribosomes and cytoskeleton
What is lumen?
Inside of the organelles
What are some functions that occur at the membranes?
- Compartmentalization
- Scaffold for biochemical activities
- Selectively permeable barrier
- Transport solutes
- Respond to external stimuli
- Interact between cells
Why is Singer and Nicolson’s model called ‘fluid mosaic model’?
Fluid: Due to the mobility of the lipids and some proteins
Mosaic: Many different lipids and proteins
What are some examples of membrane lipids?
- Phospholipids
- Glycolipids
- Sterols
What is an example of different kinds of phospholipids?
Phosphoglyceride is an example of phospholipid- which most commonly have a glycerol group attached to them.
What is the general structure of phosphoglycerates
- Different groups (chlorine)
- Phosphate group
These two make the polar head - Glycerol
- Hydrocarbon tails
- these tails can be saturated or unsaturated
- and are about 14-28 atoms long
How does glycerol look like?
It has 3 carbons and 3 oxygens. The right two are attached to the hydrocarbon tails and the last one is attached to the phosphate group
What are liposomes?
These are artificial lipid bilayers used to study lipid proteins.
What is fluidity affected by?
- Temperature: lower temperature makes it more viscous and less fluid
How can the cell react to changes in the temperature?
- Change in composition by doing the following:
- Phospholipid saturation: Increasing the cis-double bonds increase fluidity at lower temperatures
- Phospholipid tail length: Shorter hydrocarbon tail length increase the fludity
- Lipid composition: Add cholesterol in animal cell membranes (stiffens the membrane, and makes it less permeable to water)
What is the ratio of cholesterol to phospholipids in the membrane?
There can be 1: 1 ratio of cholesterol and phospholipids. this stiffens the membrane by decreasing mobility and the plasma membrane is less permeable to polar molecules.
What enzyme catalyzes the flip flop of random phospholipids in the membrane?
Scramblase catalyzes the flip flop of random phospholipids.
Why are scramblases even needed?
The phospholipids are synthesized in the cytosolic leaflet, so scramblases helps to put them on either side.
Does the membrane retain their position throughout the processes?
The enzyme flippases catalyze the flip flop of “specific” phospholipids in the Golgi-apparatus. From here, the phospholipids retain their positions.
What are the two roles of flippases?
- It flip flops specific phosphilipids in the golgi-apparatus
- It sometimes helps to join proteins to the plasma membrane
How are glycolipids or glycoproteins made ?
The are formed by adding sugar to lipids or proteins on the LUMINAL face of Golgi
Then they either end up facing non-cytocylic side on either plasma membrane or inside of some organelles.
They protect the membrane from harsh environment
What are intergral membrane proteins?
They insert into the membrane some way.
What are pheripheral membrane proteins?
Associated with the membranes or integral membrane proteins in non-covalent ways.
What are Transmembrane proteins?
These are the proteins that pass through the entire lipid bilayer once or many times. (it is a type of integral protein)
What are monolayer-associated proteins?
These are types of integral membrane proteins. They pass only one layer into the membrane
What are lipid linked proteins?
the lipid part of the protein inserts into the membrane, so it is still a integral protein
What are protein attached proteins?
these are non-covalently bonded to other proteins, making them pheripheral proteins.
How many types of integral proteins exist and what are they?
1.Transmembrane proteins
2. Monolayer proteins
3. Lipid-linked proteins
so there are 3 overall
How can you extract the integral membrane proteins?
Use detergents to destroy the bilayer and extract the proteins
How can you extract the pheripheral membrane proteins?
Use gentle extraction methods, because the lipid bilayer does not have to be destroyed.
What are some characteristics of Transmembrane integral proteins?
They have 2 domains and are amphipathic:
Hydrophillic domain (polar): AA chain are polar
Hydrophobic domains (non-polar): The AA are non-polar
In a membrane spanning proteins, how many hydrophobic amino acids are there?
20 hydrophobic amino acids
Why does each transmembrane protein have specific orientation?
Because it is essential for their function
What are two ways transmembrane proteins can be identified?
- X-Ray crystallography: deterimes 3D structures
- Hydrophobicity plots: Segements of 20-30 hydrophobic amino acids can span the lipid bilayer as an
ALPHA HELIX.
How is the hydrophobicity graph studied?
Y axis: has the hydropathy index, the lower means HYDROPHILLIC and higher means HYDROPHOBIC
X -axis: amino acid number, starts counting from the N-terminus
What does the highest peak indicate on the hydropathy index?
It means that, that region is hydrophobic and DOES NOT MEAN that , that amino acid hydrophobic
What are the characteristics of Monolayer associated membrane proteins?
Thye are proteins anchored on the cystolic face by an amphipathic aplha-helix
What are characteristics of Lipid linked membrane proteins?
These have GPI anchor and are synthesized in the ER lumen and hence face the non-cytosolic face
there are other proteins that lipid anchor and the cytosolic enzymes add the anchor and direct proteins to cytosolic face.
What is triton X-100 and what regions does it have?
It has a hydrophobic region and a hydrophobic one. And it is a detergent
What are some problems with extraction?
so first you break the lipid bilayer using detergent. Now you purify the proteins abd remove the detergent and add phospholipids. But these may not form the same way they used to be.
What is FLAX?
It is used to study the movement of proteins. the proteins are fused to GFP. but not all proteins have lateral movement cause they might be struck to something.
Do membrane proteins flip-flop?
Nothing ever flipflops after its set up, so no
How do you read the FRAP graph?
So the Y axis is the flurocent in the blrached area. You read the frap time from the dip all the way to the end until the same height as before the photobleach takes place.
What is the rate of florescence recovery?
It is the amount of time taken for the neighboring unbleached flurocent proteins to move to the bleached area.
How do you know which protein has a faster lateral movement?
The one with lower FRAP time is faster
