Unit 1: Cells and Proteins KA 1.3: Membrane proteins Flashcards
where are integral (transmembrane) membrane proteins found?
they are embedded into the membrane. Some can be transmembrane and span the entire width of the membrane.
what are integral membrane proteins interactions with the membrane?
integral membrane proteins are held in place by strong hydrophobic interactions between the R groups of the protein and the hydrophobic region of the membrane
where are peripheral membrane proteins located?
peripheral membrane proteins are located on the surface of the membrane.
they can be intracellular or extracellular
how to peripheral membrane proteins interact with the membrane
peripheral membrane proteins have hydrophilic R groups on the surface of the protein and often interact with the surface of integral proteins
bound to the membrane surface by hydrogen and ionic bonds
describe the process of facilitated diffusion
The passive transport of substances across the membrane through specific transmembrane proteins such as channels or transporters
does facilitated diffusion require energy?
Nope, this process moves substances down their concentration gradient
how do ligand gated channels open to let molecules pass through?
ligand channels change confirmation in response to the binding of ligand the protein channel
this confirmational change allows the channel to open and molecules to pass through
how do voltage gated channels open to let molecules pass through?
voltage gated channels change confirmation in response to changes in ion concentration
as ions are charged molecules voltage changes
This confirmational change allows the channel to open and molecules to pass through
how to transport proteins facilitate diffusion from the extra cellular to the intracellular space
Molecules binds to transporter on the extracellular side
Confirmation of transporter protein changes and the binding site is now on the intracellular side
The molecule is released from the binding site and the confirmation of the protein returns to the original shape
describe ATPases
ATPases are pumps coupled with an energy source that hydrolyse (breakdown using water) ATP directly and these catalyse the conversion of ATP into ADP + pi
this reaction releases energy which brings about the conformational change required to move the substance across the membrane
what is an example of an ATPase?
sodium potassium pump
how are molecules transported in active transport?
Against the concentration gradient by pumps like ATPases
Does passive transport require energy?
no
Does active transport require energy?
Yes
name the two different types of passive transport
Simple diffusion and facilitated diffusion
what molecules are transported by simple diffusion?
O2 and CO2
How are molecules transported into simple diffusion?
Down the concentration gradient and through the bilayer
what molecules are transported in facilitated diffusion?
Glucose and water
how are molecules transported in facilitated diffusion?
against the concentration gradient with help of transporters or channels
what molecules are transported in active transport?
Ions and glucose (in some areas)
what is the concentration gradient?
Difference in concentration of a solute across the plasma membrane
what is membrane potential also known as electrical potential difference?
membrane potential is created when there’s a difference in electrical charge on the two sides of the membrane
what is the process of the sodium potassium pump?
a) the pump has higher affinity for sodium ions inside the cell, therefore binding occurs
b) the pump hydrolysis ATP and phosphate attaches to it. phosphorylation by ATP causes the confirmation of the protein to change
c) the affinity for sodium ions decrease resulting in sodium being released outside the cell
d) the pump now has high affinity for potassium ions outside the cell therefore binding occurs
e) default realisation occurs which causes the conformation of the protein to change
f) potassium ions are taken into the cell and the process starts again
why is the glucose symport classed as active transport?
because glucose needs energy to move across it as it’s moving against its concentration gradient
define the term symport
Who transports two substances at the same time in the same direction?
in what direction are glucose and sodium move to glucose symport in terms of concentration gradient?
Glucose moves against the concentration gradient
sodium ions move with the concentration gradient
