bio-membrane transport Flashcards
“fluid mosaic” model
Lumpy, constantly changing / shifting mosaic of “tiles” (proteins)
Functions of the plasma membranes
Isolates cells contents from environment
Regulates exchange of essential substances
Communicate with other cells
Creates attachments within and between other cells
Regulates biochemical reactions
Structure of cell membranes
Phospholipid bilayer with proteins scattered throughout
Describe phospholipid bilayer
2 rows of phospholipids, hydrophilic heads facing outwards on both sides, hydrophobic tails facing inwards in between
What drives the phospholipids to form a bilayer
The exterior and interior of the membrane face watery environments (extracellular fluid, cytosol), hydrophilic heads must face outwards in both sides with tails between
Purpose of cholesterol in membranes on animal cells
Keeps it flexible
What holds the phospholipids together
Weak interactions between phospholipids NOT BONDED TOGETHER
What happens if the fatty acid tails of the phospholipids are unsaturated? Saturated?
If it’s unsaturated there are kinks in their tails, if Saturated they are more straight
What makes the membrane fluid?
Individual phospholipids aren’t bound together,
Unsaturated fatty acids make membrane more fluid than if they were saturated
Where are proteins found in the membrane
Embedded within phospholipid bilayer (either floating or anchored in)
Glycoproteins
Proteins with attached carbohydrates
Categories of membrane proteins
Receptor proteins Recognition proteins Enzymatic proteins Attachment proteins Transport proteins
Receptor proteins
Trigger cellular responses upon binding specific molecules (look at pics in ppt)
Recognition proteins
Serve as identification tags on the surface of the cell
Enzymes
Promote chemical reactions that either make or break up biomolecules
Attachment proteins
Anchor the cell membrane to the inner cytoskeleton, to proteins outside the cell, and to other cells
Transport proteins
Regulate import/export of hydrophilic molecules
Types of transport proteins
Channel and carrier proteins
Homeostasis
Maintain a stable internal state
Biggest contributor in maintaining homeostasis in a cell
Cell membrane
What does it mean to reach equilibrium
All molecules are equally spread out
Opposite of equilibrium
Gradient
Fluid
A substance that can move or change shape in response to external forces
Solute
A substance that can be dissolved (dispersed as ions or molecules)in a solvent
Solution
A mixture in which one substance is dissolved evenly in another
Solvent
Fluid capable of dissolving a solute
Concentration
How much solute in a given amount of solvent