Biochem Unit 1 Lecture 3 Membrane Structure & Function

--- serve to separate different aqueous compartments in the cell thus allowing different functions to be maintained within each

Phospholipid bilayers

Bilayers also represent a physical barrier to transport of --- substances and a metabolically important site for --- via transmembrane proteins

hydrophilic; cell signaling

--- are lipids with a carbohydrate chain attached

Glycolipids

When phospholipids are dispersed in water they naturally form --- or vesicles(liposomes) with a lipid bilayer:

micelles

Basic Phospholipid Structures

--- Backbone: the 3 OH groups of --- are sites for side chain attachment

Glycerol; glycerol

Basic Phospholipid Structures

--- Backbone: usually O-linked to a charged group and amide-linked to an acyl group, such as a fatty acid

Sphingosine

Basic Phospholipid Structures

Sphingosine Backbone: usually O-linked to a --- group and amide-linked to an --- group, such as a fatty acid

charged; acyl

What are the 4 major phospholipids in mammalian plasma membranes?

Phosphatidylethanolamine

Phosphatidylserine

Phosphatidylcholine

Sphingomyelin

True or false?

Charged molecules cannot readily diffuse through lipid bilayer.

true

O 2, N2 and CO 2 can diffuse --- across bilayer and H 20 can diffuse more ---

rapidly; slowly

--- and other --- cannot diffuse across membranes

Glycine; amino acids

--- compounds can diffuse across membranes (e.g., estrogen, steroids)

Hydrophobic

Lipid components of the plasma membrane are distributed ---

asymmetrically

--- are artificially prepared vesicles composed of a lipid bilayer.

--- can be used to administer and transport nutrients and pharmaceutical drugs in the body.

Liposomes; Liposomes

The --- is a common structural feature of transmembrane regions of integral membrane proteins

alpha helix

Other than phospholipids and membrane proteins, what are other components of plasma membrane?

cholesterol, triglycerides, glycolipids

Fluorescence recovery after photobleaching (FRAP) showed that ---.

Membrane Proteins can Move within the Lipid bilayer

--- are specialized domains predominantly within plasma membranes of cells which organize membrane proteins and glycolipids into groupings having functional implications in terms of receptor trafficking, neurotransmission, and membrane fluidity.

Lipid Rafts

Compositionally, lipid rafts differ from the plasma membrane as a whole by being enriched in --- and ---.

cholesterol and sphingolipids

Lipid rafts tend to be resistant to dissociation by --- which can dissociate the other (more fluid) regions of the membrane

detergents

---, which are invaginations of the plasma membrane, form from lipid rafts.

Caveolae

Caveolae, which are invaginations of the plasma membrane, form from ---.

lipid rafts

It has been proposed that --- play a role in cell signaling events for the B-cell antigen receptor, the T-cell antigen receptor, and IgE receptor

lipid rafts

Membrane Fusion

Enveloped virus attaches to the --- of recipient cell via receptors and receptors on the surface of the virus, followed by fusion where the envelope blends with the cell membrane and releases its contents (---) into the cell.

cell membrane; genome

Give some examples of enveloped viruses containing human pathogens.

DNA viruses (example, herpesviruses)

RNA viruses (example, Coronavirus)

Retroviruses (example, HIV).

Scramblase tends to not use ---.

ATP

What is the difference between the 3 different phosphoglycerides?

Phosphatidylethanolamine Phosphatidylserine

Phosphatidylcholine

the polar head groups have different compositions

Some phospholipids can be cleaved into products that function as important ---

intracellular second messengers

A --- micelle/liposome has multiple lipid bilayers while a --- micelle/liposome has a single lipid bilayer

multilamellar; unilamellar

--- were used for COVID vaccine delivery.

Liposomes

What are 4 functions of membrane proteins?

Cell-cell contact (cell adhesion)

Receptor signaling systems

Pores and channels (transport)

Enzymes

--- have no phosphate group and 3 fatty acid chains.

Triglycerides