Membrane Proteins Flashcards
Regions of hydrophobic R groups allow
strong hydrophobic interactions that hold integral proteins within the phospholipid bilayer
Some integral proteins are
transmembrane
What are peripheral membrane proteins?
Have hydrophilic R groups on their surface and are bound to the surface of membranes, mainly by ionic and hydrogen bond interactions
The phospholipid bilayer is a barrier to
ions and most uncharged polar molecules
Some small molecules, such as oxygen and carbon dioxide
pass through the phospholipid bilayer by simple diffusion
What is facilitated diffusion?
The passive transport of substances across the membrane through specific transmembrane proteins
What do different cell types have in order to perform specialised functions?
different channel and transporter proteins
Most channel proteins in animal and plant cells are ________ selective
highly
Some channel proteins are gated and change conformation to
allow or prevent diffusion
What are ligand-gated channels controlled by?
the binding of signal molecules
What are voltage-gated channels controlled by?
changes in ion concentration
Transporter proteins bind to the
specific substance to be transported and undergo a conformational change to transfer the solute across the membrane
Active transport uses
pump proteins that transfer substances across the membrane against their concentration gradient
What is required for active transport?
A source of metabolic energy
Some active transport proteins hydrolyse ATP directly, to
provide the energy for the conformational change required to move substances across the membrane
What does ATPase do?
hydrolyse ATP
What is the electrochemical gradient?
A combination of the concentration gradient and the electrical potential difference
What does the electrochemical gradient do?
determines the transport of the solute
What do ion pumps (eg the sodium-potassium pump) use energy from the hydrolysis of ATP to do?
To establish and maintain ion gradients
The sodium-potassium pump actively transports
sodium ions out of the cell and potassium ions into the cell
The pump has high affinity for
sodium ions inside the cell; binding occurs; phosphorylation by ATP; conformation changes; affinity for sodium ions decreases; sodium ions released outside of cells, potassium ions bind outside the cell; dephosphorylation ;conformation changes; potassium ions taken into cell; affinity returns to start
In the small intestine, the concentration gradient of sodium ions created by the sodium-potassium pump
drives the active transport of glucose
The sodium potassium pump is found in
most animal cells
The sodium-potassium pump accounts for a
high proportion of the basal metabolic rate in many organisms
The glucose transporter responsible for this glucose symport transports
sodium ions and glucose at the same time and in the same direction
When is a membrane potential (an electrical potential difference) created?
when there is a difference in electrical charge on the 2 sides of the membrane
For each ATP hydrolysed
3 sodium ions are transported out of the cell and 2 potassium ions are transported into the cell
What does the transport of ions establish?
both concentration gradients and an electrical gradient
Sodium ions enter the cell down their
concentration gradient, the simultaneous transport of glucose pumps glucose into the cell against its concentration gradient
What happens in intestinal epithelial cells?
The sodium-potassium pump generates a sodium ion gradient across the plasma membrane
