1.3 Flashcards
What is the plasma membrane?
A fluid mosaic bilayer of phospholipids and proteins
How do hydrophilic head groups align?
To the extracellular space or cytoplasm
Where to the hydrophobic tails point?
inwards
What are the two types of proteins in the membrane?
Integral and Peripheral
In integral proteins, what do the hydrophobic R groups allow?
Strong hydrophobic interactions holding membrane proteins within the phospholipid bilayer
Some integral proteins are transmembrane, what does this mean they do?
Span the width of the membrane
Are peripheral proteins embedded in the bilayer?
no
Are integral proteins embedded in the bilayer?
Yes
What do the hydrophilic R groups of the surface of peripheral proteins do?
They are bound to the surface of membranes mainly by ionic and hydrogen bond interactions and they can interact with the surfaces of integral proteins
The phospholipid bilayer is a barrier to……
ions and uncharged polar molecules
What is facilitated diffusion?
The passive transport of substances across the membrane through specific transmembrane proteins.
What are the channels water can pass through?
Aquaporins
What are the two types of membrane channel?
Ligand-gated and voltage-gated
What are ligand-gated channels controlled by?
The binding of signal molecules (e.g. neurotransmitter)
What are voltage-gated channels controlled by?
Changes in ion concentration
What are the jobs of membrane channels?
Change conformation to allow or prevent diffusion.
What do Transporter Proteins do?
Bind to a specific substance to be transported and undergo a conformational change to transport a solute across the membrane
Do transporter proteins require energy?
Some do
ATPases…..
hydrolyse ATP
How is the membrane potential created?
When there is a difference in electrical charge on two sides of the membrane.
What is the Sodium-Potassium pump and what does it do?
It’s an ion pump that uses energy from the hydrolysis of ATP to establish and maintain ion gradients
Is Na+ pumped in or out?
Out
How many NA+ are pumped out?
3
Is K+ pumped in or out of the cell?
In
How many K+ are pumped in?
2
What is a symporter?
An integral membrane protein involved in the transport of different molecules.
Na+ ions enter the cell ____ their concentration gradient
down
the simultaneous transport of glucose into the cell is ____ the concentration gradient
against
What are the functional steps of the sodium-potassium pump?
- Transporter protein has high affinity for sodium ions inside the cell therefore binding occurs.
- Phosphorylation by ATP causes the conformation of the protein to change
- Affinity for ions changes resulting in Na+ being released out of the cell.
- K+ ions from the outside of the cell bind to the pump
- Dephosphorylation occurs causing conformation of protein to change
- K+ ions are taken into the cell and affinity returns to the start.
