What is the plasma membrane's function?

There are 5.

1. Permeability barrier

2. Transporting material in and out of cell

3. site of specific function due to the protiens found in or within the membrane

4. Detection of signals (receptors)

5. Intercellular communication and adhesion

Proteins, carbohydrates, lipids. 

Not all plasma membrane's need carbohydrates, and can have little protiens, lots of lipids or vis versa. 

What general membrane function does the statement illustrate:

When cells are disrupted and fractioned into subcellular components, the enzyme cytochrome P-450 is recovered with the endoplasmic reticulum fraction?

a.  Permeability barrier  b.  Localization of function

  c.  Regulation of transport  d.  Detection of signals

What general membrane function does this illustrate:

The membrane of a plant root cell has an ion pump that exchanges phosphate inward for bicarbonate outward.

a.  Permeability barrier  b.  Localization of function

  c.  Regulation of transport  d.  Detection of signals

Which one of the general membrane functions does the statment illustrate:

Insulin does not enter a target cell, but binds to a membrane receptor on the external surface of the membrane, therby activating the enzyme adenylyl cyclase on the innter membrane surface.

a.  Permeability barrier  b.  Localization of function

  c.  Regulation of transport  d.  Detection of signals

They have a hydrophilic head (water loving), and hydrophobic tail (water hating) (means that they are amphipatic).

Creates lipid bilayer of PM.

Creates 2 faces Exoplasmic face (exterior) and cytoplasmic face (on the other side)

Cholesterol= It provides rigidity to the membrane and helps determine its fluidity. 

Sterols=makes the membrane less fluid at higher temps than it normally would and decreases the permeability of the lipid bilayer to ions and small polar molecules.

What does the membrane's fludity depend on?

3 main things.

Lipid compostion

-Long chain of fatty acid is less fluid than short chains

-unsat. more fluid than sat.

Cholesterol concentration

-makes membrane less fluid at higher temps

-prevents hydrocarbon chanins from fitting togehter at colder temps

Temp

-must be at certain temp to function correctly

They are thin bands of PM proteins

-looks like PM of two cells fused together

-2 main integral protiens (Occludin and Claudin)

Purpose:

Prevent substances from moving between epithelial cells

Prevents lipids and protiens from moving within the plane of the bilayer

Keeps the specialized parts of the membrane seperated

It's purpose is to bind adjacent cells together

It provides strenght and rigidity to tissues

3 types 

Spot= cell to cell adhesion

Hemi= cell to basal lamina adhesion

Belt=cell to cell adhesion 

-central matrix of proteins between PM's

Provides direct communication between adjacent cells

CQ: Generally speaking transport across membranes can occur in what three ways?

a. Osmosis, active transport, and ion gated channels

b. Simple diffusion, facilitated diffusion and active transport

c. Simple diffusion, active transport, and osmosis

d.  Direct active transport, indirect active transport, and simple diffusion

B. Simple diffusion= way to get things across

Facilitated diffusion= getting things across but with help

Active Transport= hydrolosis of ATP needed to get things across membrane

Direct movement of a solute from high concentration to an area of lower concentration through the lipid bilayer.

-Typically how we get gases across membrane

-If it small enough and nonpolar it can get across membrane

-Ions can't get across because they have a shell of hydration and simple diffusion is hydrophobic

It is the passive transport with the movement from higher to lower concentration in which it only relys on the affinity of the cargo to the transport protein.

-Doesn't require ATP

-Create a hydrophilic channel to get through bilayer of PM

-Carriers are very specific

-A type of facilitated diffusion that is mediated by a carrier

-The driving force behind this is concentration gradient

-Can only transport 1 molecule at a time, and only moves in one direction. 

-Glut 1 is example of uniporter

1. Glucose binds to binding site

2. The glucose is bound

3. The binding cite flips, glucose is now on inside

4. The glucose falls off the bindg site and is now inside the molecule

5. The binding cite flips so it is facing the outside of the molecule again.

Both can tranpsort against the concentration gradient facilitated by a carrier protein but symporter is when both molecules move in the same direction while antiporters are when molecules move in opposite directions

ex. of Symporter= Na+/ Glucose symporter; both Na+ and Glucose go in, both go out.

ex. antiporter= Chloride-Bicarbonate Antiporter; 1 bicarbonate goes out, one cholride ion goes in.

3 Na+ goes in, so 1 Ca2+ must go out. 

-Rise in the calcium triggers concentrations to rise which causes the antiporter is a quick way to get rid of excess calcium. 

1. Plasma membranes have few, if any, transport proteins that are specific for phosphorylated compounds.

  A.  True  b.  False

and why

  Carbon dioxide and bicarbonate anions usually move in the same direction across the plasma membrane of a RBC.

  A.  True  b.  False

and why?

3.  Both simple diffusion and facilitated diffusion require the presence of an integral membrane protein.

  A.  True  b.  False

And why?

-to transport ions and water

-to regulate the electrical potential across the membrane

-cell signaling

They are used to tranpsort ions only using diffusion gradient to power the movement. 

-Each channel can only transport one specific type of ion

-Most are gated which means that pores open and close in response to stimulus.

a.  When a ligand binds to an ion channel, an enzyme facilitates the passage of the ion across the membrane

b.  When a ligand binds to an ion channel, the channel interacts with a G-protein that subsequently opens another ion channel nearby allowing ions to cross the membrane

c.  A ligand-gated ion channel is generally open and allows ions to cross the membrane. However, in the presence of the ligand, the channel closes

d.  When a ligand binds to an ion channel, the channel changes conformation and the ion channel opens allowing the ion to cross the membrane

-It is ATP powered pumps, goes against gradient.

-Can be a uniporter or an anitporter

-3 types= P-Class, F and V class, and ABV superfamily (all have dif protien strucutres)

-REQUIRES ATP AND PROTEINS

-ATP DRIVES THE TRANSPORT

-Work by the reversible phosphorlyation of the protein

-Adding phosphate group to a pump

It pumps protons into organelles, found in vesicles/ vacuoles

-PH effects 3D strucutre

It is involve din ATP production

-found in bacteria, mitochondria, and choloroplasts

It maintains intercellular Na+ and K+ concentrations in animal cells

-moves 3 NA+ out for every K+ in. 

It releases Ca2+ from SR to cytoplasm which causes contraction (it is found in muscle). 

-Keeps uptake of Ca2+ from cytoplasm which causes relaxation. 

  Active transport is always driven by the hydrolysis of high-energy phosphate bonds.

  a.  True  b.  False

Treatment of an animal cell with an inhibitor that is specific for the Na+/K+ pump is not likely to affect the uptake of glucose by sodium cotransport

  a.  True  b.  False

Active transport usually requires proteins called ATPases.

  a.  True  b.  False

From the list of properties, indicate which one can be used to  distinguish between the following pairs:

Properties:

a.  Directions in which two transported solutes move

b.  Requirement of metabolic energy

c.  Requirement for simultaneous transport of 2 molecules

d.  Kinetics of transport

  a.   A   b.  B  c.  C  d.  D

From the list of properties, indicate which one can be used to  distinguish between the following pairs:

Properties:

a.  Directions in which two transported solutes move

b.  Requirement of metabolic energy

c.  Requirement for simultaneous transport of 2 molecules 

d.  Kinetics of transport

  a.  A  b.  B  c.  C  d.  D

B is correct because facilitated doesn't require ATP

From the list of properties, indicate which one can be used to  distinguish between the following pairs:

Properties:

a.  Directions in which two transported solutes move

b.  Requirement of metabolic energy

c.  Requirement for simultaneous transport of 2 molecules 

d.  Kinetics of transport

From the list of properties, indicate which one can be used to  distinguish between the following pairs:

Properties:

a.  Directions in which two transported solutes move

b.  Requirement of metabolic energy

c.  Requirement for simultaneous transport of 2 molecules 

d.  Kinetics of transport

  a.  A  b.  B  c.  C  d.  D

It imports extracellular molecules by forming vesciles from the PM.

-Moves things from outside the cell, to the inside of the cell in the form of vesicles.

 Role:

Feeding (how some organisms get there nutrients)

Take large particles into cell because it is too big to get in other ways (ex. iorn)

Destory foreign substances then eat them

It is actin-mediated process used to internalize bacteria and other larger materials.

-Ingests large particles occuring in specialized cells

-Englufs specific things, then makes a vacuole

They avoid destruction by, for example, getting internalized but then prevents fusion of its phagosome with a lysosome. or prevents TACO protein removal from phagosome surface, which needs to be removed before phagosomes can fuse with lysosome. 

It is the invagination of the plasma membrane.

Basically cellular drinking

  a.  True  b.  False

  a.  True  b.  False

It internalizes extracellular molecules by means of specific receptors on the outer surface that bind to ligands.

(Ligand=anything that binds specifically to a receptor)

- Results in the formation of an endosome

CQ:  Which protein mediates binding of clathrin to a receptor?

The coat of a coated vesicle comes from the protein

a. Dynamin

b. Connexi

c. Adaptin

d. Clathrin

The release of the cargo from the receptor during receptor mediated endocytosis is mediated by

Under acidic pH, iron leaves transferrin converting ferrotransferrin to apotransferrin.

  a.  True  b.  False

Under neutral pH apotransferrin binds to the receptor.

  a.  True  b.  False

It is triggered by a specific extracellular signal (nerotransmiter, hormone)

Results in generation of a second messenger Ca 2+

It is important in the signal cascade leading to exocytosis 

Take things out wihle endocytosis takes things in (poops things out)

-It realeases inracellular molecules to the extracellular matrix.

Steps:

1. Secretory vesicle approaches the PM

2. SV fuses with the PM

3. Rupture of cell membrane

4. Discharge of vesicle contents

NEEDS A TON OF CALCIUM TO GET THIS TO HAPPEN

It is how iorn is internalized. It delivers iorn to cells (Apotransferrin=iorn free, ferrotransferrin=iorn bound)

1. Ferrotransferrin binds to receptor in coated pit

2. It gets internalized

3. Endosome fuses with a storting vesicle (results in pH decreasing)

4. Iron leaves transferin forming apotransferrin

5. Apotransferrin reamins bound

6. Endosome returned to surface

7. Neutral pH causes transferrin to leave receptor.