Chapter 7: Membrane Structure and Function Flashcards
Two types of cellular membrane proteins
Integral (transmembrane)
Peripheral (does not go through the bilayer
Amphipathic molecules?
Hydrophobic and hydrophilic components
Describe the movement of phospholipids across the membrane
Phospholipids in the plasma membrane can mice within the bilayer
Most lipids and some proteins drift laterally
Rarely do they flip flop transversely across the membrane
Do proteins move in the membrane?
Some drift within the bilayer
Move slower than lipids
Some moved by motor proteins in the cytoskeleton
Some never move and are anchored by The cytoskeleton
Cholesterol regulates the ___________ of a membrane
Fluidity
Cholesterol wedges between plasma membrane of animal cells
Two types of membrane proteins
Peripheral proteins- loosely bound, cytoplasmic side and exterior side
Integral proteins- within the membrane
Proteins that have a hydrophobic and hydrophilic regions, transmembrane proteins
Integral proteins
Covalent attachments of a lipid to an amino acid side chain within a protein
Lipid-anchored proteins
Six major functions of membrane proteins??
- transport
- enzymatic activity (speed up chemical reactions)
- signal transduction
- Cell-cell recognition
- intercellular joining
- attachment to the cytoskeleton and extracellular matrix (ECM)
Cells recognize each other by binding to surface molecules, often ___________, on the plasma membrane
Carbohydrates
Also glycolipids, glycoproteins, usually branched oligosaccharides with fewer than 15 sugar units
The asymmetrical distribution of proteins, lipids and associated carbohydrates in the plasma membrane is determined when the membrane is built by the _________________
ER and Golgi apparatus
What can pass through the plasma membrane rapidly, dissolve in the lipid bilayer?
Hydrophobic (nonpolar) molecules and gasses
What does not pass through the plasma membrane easily? Mostly transported through transport proteins
Hydrophilic/ polar molecules
What diffuses slowly across the PM?
Ions
Water enters through the plasma membrane though….
Aquaporins
What allows the passage of hydrophilic substances or certain ions across the membrane?
Transport proteins
- bind to molecules and change shape to shuttle them across the membrane
- specific for the substances it moves
- how sugar is brought in
Carrier proteins
Does facilitated transport require energy?
No
With diffusion each substance diffuse ________ their concentration gradient
Down
Water diffuses across a membrane from a region of ________ solute concentration to region of ________ solute concentration
Lower, higher
The ability of a solution to cause a cell to gain or lose water
Tonicity
When cells with walls are in a hypotonic they become….
Turgid(from) this is normal for plants
When plants are in a isotonic solution they are…..
Flaccid (limp)- the plant may wilt
When a plant cell is in a hypertonic solution what happens?
Plasmolysis - membrane pulls away from the wall, usually lethal
What kind of transport always goes from high to low concentrations
Passive
Facilitated transport is passive but needs proteins
Corridors that allow a specific molecule or ion to cross the membrane (some are gated)
Energy is not required, molecules follow their concentration gradient
Channel proteins type of facilitated diffusion
Undergo a subtle change in shape that translocates the solute-binding site across the membrane
Energy is not required, molecules follow their concentration gradient
Carrier proteins type of facilitated diffusion
Sodium-potassium pumps create what type of gradient?
Electrochemical
With sodium-potassium pumps, _____ K+ goes ______ the cell and _____NA+ goes _____the cell
Inside the cell the charge is _________
Outside the cell the charge is _______
2, into
3, out
Negative, positive
What is membrane potential
The voltage difference across a membrane
What is the main electrogenic pump of plants, fungi, and bacteria?
Proton pump
Transport protein that generates the voltage across the membrane
Electrogenic pump
What is the difference between primary and secondary active transport?
Primary directly uses energy to transport solute, secondary uses pre-existing gradient to drive transport of solute
Occurs when active transport of a solute indirectly drives transport of another solute
Ex: plants commonly use the gradient of hydrogen ions generated by proton pumps to drive active transport of nutrients into the cell
Cotransport: coupled transport
Uniport
Symptoport (both of the same direction)
Antiport (go in opposite directions)
Large molecules, such as polysaccharides and proteins, cross the membrane via _______
Vesicles
- transport vesicles migrate to the membrane, fuse with it, and release their contents
- many secretory cells use this to export their products
- energy is required
Exocytosis
Liquids or solids are taken up by the cell by invagination of the plasma membrane
Requires energy
Endocytosis
“Cellular eating”
Cell engulfs particles in a vacuole
Phagocytosis
Type of endocytosis
Cellular drinking
Cell creates vesicle around fluid
Pinocytosis
Type of endocytosis
Binding of ligands to receptors triggers vesicle formation ex: cholesterol
Receptor-mediated endocytosis
