Membranes and Proteins Flashcards
What is the function of the cell membrane?
Communication, regulating transport, transmitting signals
What types of biological molecules are found in cell membranes?
Carbohydrates, proteins, and lipids
Why does the membrane form a bilayer?
The hydrophobic tails of the phospholipids interact with each other and the hydrophilic heads interact with the water on the outside and inside of the cell
Why are membranes asymmetrical? What causes it?
The outside has different functions than the inside. The asymmetry comes from the proteins and the different types of phospholipids
What is a membrane’s TM?
The temperature where a membrane freezes or becomes fluid
What characteristics of the phospholipid tails contribute to their fluidity?
Unsaturation and chain length
What makes a membrane more fluid?
Phospholipids with shorter carbon chains and more double bonds
What are integral membrane proteins?
Proteins with a hydrophobic regions that goes into (monotopic) or through (transmembrane) the membrane
What are multipass proteins?
Proteins that have hydrophobic regions separated by hydrophilic regions. The hydrophobic regions pass through the membrane and the hydrophilic regions form loops
What are peripheral membrane proteins?
Proteins on one side of the membrane that have no hydrophobic regions and don’t go into the membrane
What is glycosylation and what is it used for?
Adding a sugar to something, usually a membrane protein for signaling or recognition purposes?
What kinds of molecules can easily get through the membrane?
Small hydrophobic molecules, gases, small uncharged polar molecules
What kinds of molecules can’t get through the membrane at all without help?
Large uncharged polar molecules, ions, charged polar molecules
What is passive transport?
Solutes moving down their concentration gradient, no energy input is needed
What is active transport?
Solutes move against their concentration gradient, requires energy input
What are carrier proteins? How do they work?
They are used in facilitated diffusion to get certain molecules across the membrane that can’t diffuse across on their own. They bind to their specific solute, change shape, and the solute detaches on the other side of the membrane because its still moving down its concentration gradient
What are channels? How do they work and how are they regulated?
Multiple proteins forming a hollow tube that allows ions through. The channels are specific for one particular ion, and the ion diffuses down its concentration gradient through the channel. They are regulated by gating
What are the three types of ion channel gating?
Voltage, ligand, and mechanical
What triggers voltage gated channels to open or close?
A change in the membrane potential will make the charged amino acids in the S4 domain of the channel move around and open the channel, and go back to their original positions when at resting voltage.
What triggers ligand gated channels to open or close?
When the ligand binds, the channel opens. When the ligand detaches, the channel closes
What triggers mechanical gated channels to open or close?
Physical stretching of the membrane
How does the Na+/K+ ATPase pump work? What is the purpose?
ATP is hydrolyzed and 3 sodium are pumped out of the cell and 2 potassium are pumped in. It sets up membrane potential
What are cotransporters? How do they work?
Transport proteins that move 2 things at once. They work through indirect active transport. One thing moves down its concentration gradient and powers the other thing moving against its concentration gradient. ATP is still used up, but not directly by the cotransporter
What are symporters?
Both things move in the same direction
