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Advanced Higher Bio
Unit 1 Membrane Proteins
| Question | Answer |
|---|---|
| What is a transmembrane protein | one that spans the membrane |
| What is the function of transmembrane proteins | to transport molecules across the membrane |
| What are the two types of transmembrane proteins | 1. channels 2. transporters |
| How do channel proteins move molecules across membrane | passive transport/diffusion |
| What name is given to all channel proteins that involve a conformational change | gated channels |
| What are the two types of gated channels | 1. ligand 2. Voltage |
| What type of gated channel responds to hyperpolarisation/depolarisation | voltage gated channels |
| What type of channel transports water across the membrane | aquaporin |
| what are the two ways to transport water across the membrane and contrast their efficiency | 1. aquaporin (most efficient) 2. phospholipid spaces (less efficient) |
| How do small uncharged molecules cross the plasma membrane | through gaps in phospholipids |
| Name a small uncharged molecule | oxygen/carbon dioxide |
| True or false different cell types/ compartments have different channel and transporter proteins. | true |
| What triggers conformational change in voltage gated channels | change in ion concentration across membrane e.g. K or Na move across membrane causing hyper/depolarisation |
| What causes a ligand gated channel to open | specific ligand (signal molecule) |
| Give an example of a ligand or voltage gated channel | K or Na channel (do not confuse with Na/K ATPase |
| Name two transporters | 1. glucose symport 2. Na/K ATPase |
| By what process is glucose moved across cell | facilitated diffusion i.e. Na needed to provide energy for glucose to move |
| By what process does Na/K ATPase move ions across membrane | active transport |
| What provides energy for Active transport of Na or K | energy from hydrolysis of ATP |
| In the unphosphorylated state the Na/K pump has a high affinity for | Sodium |
| How many Na leave the cell in the Na/K pump | 3 |
| How many K enter the cell via the Na/K pump | 2 |
| In what direction does Na move via the Na/K pump | from intracellular (cytoplasm) to extracellular (outside) cell |
| In what direction does K move via the Na/K pump | from extracellular (outside) to intraceullar (cytoplasm) |
| In the phosphorylated state the Na/K pump has high affinity for | Potassium |
| What feature defines a molecules as a transporter | They must change CONFORMATION to work |
| What happens first Na leaves cell OR pi binds to Na/K ATPase | pi binds to Na/K ATPase |
| What causes the Na/K pump to change conformation | Pi binding or becoming unbound |
| Describe the key stages of the Na/K ATPase | unphosphorylated 3 Na binds inside the cell; phosphorylation by ATP causes conformational changes releasing 3 Na outside High affinity for K outside in phosphorylated state, Dephosphorylation & conformational change 2 K released inside cell |
| Name 2 roles of Na/K ATPase | 1. maintaining osmotic balance in animal cells; 2. generation of the ion gradient for glucose symport in small intestine; 3. generation and maintenance of ion gradient for resting potential in neurons 4.generation of iongradient in kidney tubule |
| Name 3 responses to a cell following signal transduction | 1. activation of an enzyme or G protein (photoreceptor eye) 2. change in uptake or secretion of molecule (nerve impulse) 3. rearrangement of cytoskeleton (cell cycle) 4. activation of proteins that regulate gene transcription.(hydrophilic signalling) |
| resting membrane potential is approx | -70 mv |
| What term means the cell is getting more positive | depolarisation |
| what term means the cell is getting more negative | hyperpolarisation |
| What is the first step in a nerve impulse | Signal molecule ieneurotransmitter, triggers the opening of ligand-gated ion channels at a synapse |
| . If sufficient ion movement occurs changing the voltage the ion concentrations either side of membrane | voltage-gated ion channels will open and the effect travels along the length of the nerve |
| Once the wave of depolarisation has passed what happens next? | hyperpolarisation |
| Describe how hyperpolarisation (becoming more negative) occurs | the channel proteins that were open now close and others open in the opposite direction to restore the resting potential. |
Created by:
kyle_academy
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