Unit 1.3(a) - Movement of Molecules Across Membranes Flashcards
Describe the structure of the cell membrane
Made up of a phospholipid bilayer where the outside is hydrophilic and the inside is hydrophobic
How are integral proteins held within the phospholipid bilayer?
Regions of hydrophobic R groups allow extensive hydrophobic interactions holding the integral membrane protein in place
How do peripheral proteins bind to the surface of the cell membrane
They have hydrophilic R groups on their surface allowing them to bind to the surface of membranes mainly by ionic and hydrogen interactions
They can also interact with the surfaces of integral proteins
What is the role of the phospholipid bilayer?
It is a barrier to ions and most uncharged polar molecules. Some small molecules such as oxygen and carbon dioxide can pass through the bilayer by simple diffusion
What is facilitated diffusion?
The passive transport of substances across the membrane through specific transmembrane proteins
How do different cell types perform specialised functions?
They have different channels and transporter proteins
What are channels?
They are multi-subunit proteins with the subunits arranged to form water filled pores that extend across the membrane
What are ligand and voltage gated channels?
Ligand gated channels are controlled by the binding of signal molecules
Voltage gated channels are controlled by changes in ion concentration
How do transporter proteins work?
They bind to the specific substance to be transported and undergo a conformational change to transfer the solute across the membrane
Describe the use of pumps in active transport
Pumps are transporter proteins coupled to an energy source meaning that substances can be transferred across the membrane against their concentration gradient
Describe how energy can be provided for active transport
ATPases can hydrolyse ATP to provide the energy required for the conformational change to move substances across the membrane
