Unit 3- Membranes and Movement across membranes Flashcards Preview

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A structure that surrounds every cell and protects internal cellular components from the outside

Plasma membrane


What is the Plasma Membrane?

A Two-ply sheet of phospholipids with embedded or peripheral proteins


True or False: the Plasma membrane is permeable to polar/hydrophilic/water-soluble molecules

False: It is generally not very permeable to these molecules


True or False: The Plasma Membrane is impermeable to charged molecules or Ions ( by itself)



What are the activities the Plasma Membrane is involved in?

Information Transmission Import/Export of small molecules Capacity for movement/expansion All Properties linked to proteins found within the plasma membrane


Compartmentalization in the Plasma Membrane

This allows the cell to compartmentalize within the eukaryotic cells to create the membranes around organelles.


What environment are cells typically in

An Aqueous Environment


What will the membrane lipids do if they are present in large enough numbers?

They will automatically form a bilayer.


What is the most abundant lipid in the plasma membrane?

The Phospholipid


How are phospholipids amphipathic?

They have hydrophobic tails and hydrophyllic head regions (which facilitate bilayer formation)


Describe the self-sealing membrane layer:

Hydrophobic regions inability to form interactions with water results in highenergy cage-like formation of water molecules around molecule • Energy demand decreases if hydrophobic regions interact with each other as opposed to water • Hence, phospholipids, with both hydrophobic and –philic regions spontaneously coalesce into phospholipid bilayers with hydrophilics facing outward and –phobics interacting with each other with minimal exposure of any hydrophobic region to aqueous environment


What types of movement do phospholipids perform within the membrane?

Within plane Flip-Flop Spin in place Flexion: Fatty Acid Tails flexing


True or false: Flip flops of phospholipids across the membrane is a common occurance.

False: These rarely occur unless catalyzed by an enzyme


What is the difference between a saturated and an unsaturated fatty acid?

Saturated Fatty acids have at least one double bond, which will result in a bent tail. Unsaturated fatty acids have no double bonds, so both tails are straight.


What is choleterol and what is its function in relation to phospholipids?

Cholesterol is a rigid planar ring with one polar head group and a nonpolar tail. It is used to fill spaces between neighboring phospholipids, hindering movement and permeability


Describe this process

Membrane Assembly:

beginning in the cytosolic face of the Endoplasmic Reticulum


Where are phospholipids made?

On the cytosolic face of the ER


Define: Scramblases

Enzymes that randomly select phospholipids to move from one side to the opposite side of the ER Membrane.


How are phospholipids distributed to other organelles

As vesicles leave ER, new membrane gets distributed to other organelles and cell membrane


True or False: All membranes are symmetrical


Some membranes are asymmetrical (have different types of phospholipids on one face of membrane vs. other)


What is the function of flippase?

It helps the golgi sequester specific phospholipids on one face


What is the result of golgi phospholipid sequestration:

It results in membranes having a distinct inside and outside face, which is important in fuction of the associated organelles.


What are the types of membrane proteins?

Anchors, transporters, Ion Channels, Receptors, and Enzymes


What is the function of the Na+ pump?

Actively pumps Na+ out of cells and K+ in the cells


What is the function of the K+ leak channel

It allows K+ ions to leave cells, thereby having a major influence on cell excitability


What is the function of an integrin (anchoring) protein?

They link intracellular actin filaments to extracellular matrix proteins


What is the function of a PDFG (Platelet-derived growth factor) receptor?

Binds Extracellular PDGF and, as a consequence, generates intracellular signals that cause the cell to grow and divide.


What is the function of adenylyl cyclase (enzyme in the membrane)

Catalyzes the production of the small intracellular signaling molecule Cyclic AMP (cAMP) in response to extracellular signals.


Define: Transmembrane Proteins:

Transmembrane proteins have portion(s) that span the membrane with parts of the protein on both sides of the membrane. 


What structures do Transmembrane Proteins typically have?

Alpha-Helix or Beta Pleated sheets (several required)