Unit 1.3 - Membrane Proteins Flashcards
Describe the phospholipid head.
Hydrophilic and negatively charged.
Describe the phospholipid tail.
Hydrophobic and positive.
Describe integral proteins
Held within the membrane by strong hydrophobic interactions
Describe peripheral proteins
Bound to the surface of membranes, hydrophilic R-groups on their surface, held by ionic and hydrogen bonds
What types of molecules can pass through the phospholipid bilayer?
Small, non-polar molecules such as Oxygen and Carbon Dioxide
What ions/molecules do channel proteins allow through and how?
They allow passage of specific ions or non-polar molecules without any conformational change by facilitated diffusion
What causes a conformational change in ligand-gated channels?
Signal molecules binding
What causes a conformational change in voltage-gated channels?
A change in the ion concentrations across the membrane
What do transporter proteins do?
Bind to the substrate and undergo a conformational change to transfer the solute across the membrane
What is the membrane potential?
A voltage potential difference across the membrane due to a difference in electrical charge
What do the concentration gradient and electrical potential difference combine to make?
The electrochemical gradient
Where does the sodium-potassium pump get its energy?
Hydrolysing ATP
What are the stages of the sodium-potassium pump?
1 - transporter protein has a high affinity for sodium ions inside the cell, three Na+ ions bind.
2 - transporter protein is phosphorylated by hydrolysis of ATP, conformation changes.
3 - affinity for Na+ ions decreases allowing Na+ ions to be released out of the cell.
4 - new conformation has a high affinity for potassium ions, allowing them to bind.
5 - dephosphorylation of the protein causes the conformation to return to original.
6 - the original conformation has a low affinity for K+ ions causing them to be released into the cell.
The sodium-potassium pump is found in most animal cells, what is it responsible for?
The metabolic rate
A change in the activity of glucose symport proteins in the small intestine is caused by?
The sodium gradient
