Term
| Name three types of extracellular signalling molecule. |
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Definition
| Steroid hormones, peptide hormones, and neurotransmitters |
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Term
| What are the proteins on target cells that have binding sites for a specific signal molecule? |
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Definition
| receptors / receptor molecules |
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Term
| What effect does binding with a signal moelcule have on a receptor? |
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Definition
| changes the conformation of the receptor and initiates a response |
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Term
| Where are the the receptors for hydrophobic signals? |
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Definition
| inside the cell / intracellular |
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Term
| What are the receptors for hydrophobic signalling molecules? |
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Definition
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Term
| What are transcrition factors? |
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Definition
| proteins that when bound to DNA can either stimulate or inhibit initiation of transcription. |
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Term
| Give two examples of steroid hormones which are hydrophobic signalling molecules. |
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Definition
| oestrogen and testosterone |
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Term
| What do the steroid hormones bind to? |
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Definition
| receptors in the cytosol or nucleus |
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Term
| In hydrophobic signalling what happens to the hormone-receptor complex? |
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Definition
| it binds to specific sites on DNA (HREs) and affects gene expression |
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Term
| What is a hormone response element? |
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Definition
| Section of DNA where hormone-receptor complex binds which then affects transcription of the DNA |
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Term
| What type of signalling molecules bind to transmembrane receptors and do not enter the cytosol? |
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Definition
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Term
| Give two examples of hyrdophilic extracellular signalling molecules. |
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Definition
| peptide hormones and neurotransmitters |
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Term
| What happens to the transmembrane receptors when the ligand binds to their extracellular face? |
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Definition
|
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Term
| What are often involved in transduced hydrophilic signals? |
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Definition
| G-proteins or cascades of phosphorylation by kinases |
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Term
| Describe recruitment of GLUT4 glucose transporter proteins |
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Definition
| Binding of insulin to its receptor causes a conformational change that triggers phosphorylation of the receptor. This starts a phosphorylation cascade inside the cell, which eventually leads to GLUT4-containing vesicles being transported to the cell membrane. |
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Term
| What is the cause of Type 1 Diabetes mellitus? |
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Definition
| failure to produce insulin |
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Term
| What is the cause of Type 2 Diabetes mellitus? |
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Definition
| loss of receptor function |
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Term
| Which type of Diabetes is assocaited with obesity? |
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Definition
|
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Term
| Name a lifestyle factor which triggers recruitment of GLUT4. |
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Definition
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Term
| In which two types of cell do GLUT4 transporter proteins aid the transport of glucose? |
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Definition
| Skeletal muscle and fat cells. |
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Term
| Define the resting potential in membrane of neurons. |
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Definition
| whwn there is no net flow of ions across the membrane |
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Term
| What is an action potential? |
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Definition
| a wave of electrical excitation along a neuron’s plasma membrane |
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Term
| What is the effect of neurotransmitters binding to plasma membrane at a synapse? |
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Definition
| opens ligand gated channels to allow the influx of positive ions. This leads to depolarisation of the plasma membrane. |
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Term
| What is the effect on voltage gated channels should a threshold depolarisation level be achieved (in neurons)? |
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Definition
| Action potential will be generated. This is nervous transmission. An influx of Na ions through voltage gated channels causes this. |
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Term
| Restoration of the resting potential of nerones is achieved by |
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Definition
| Inactivation of the Na channels and influx of potassium ions though volatage gated channels |
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Term
| What effect does the action potential have when it reaches the end of the neuron? |
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Definition
| vesicles fuse with the membrane, releasing the neurotransmitter, which difuses across the synapse |
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Term
| Name the two types of photoreceptor cells in the retina. |
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Definition
|
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Term
| Photoreceptors which resond in dim light. |
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Definition
|
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Term
| Photoreceptors which resond in bright light and to coloured light. |
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Definition
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Term
| Which two molecules form rhodopsin? |
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Definition
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Term
| The effect on rhodopsin when a photon of light is absorbed |
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Definition
| This activated rhodopsin results in a cascade of proteins amplifying the signal |
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Term
| What is the effect of photoexcited rhodopsin on transducin? |
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Definition
| activates the enzyme phosphodiesterase (PDE) |
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Term
|
Definition
|
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Term
| What is the function of PDE? |
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Definition
| hydrolysis of cyclic GMP (cGMP) |
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Term
| What is the effect of hydrolysis of cGMP on ion channels and neurons in the retina? |
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Definition
| Closure of ion channels and triggering of nerve impulses in the retina. |
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Term
| Why are rod cells able to be activated at low light intensities? |
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Definition
| the signals are amplified |
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Term
| Why do cone cells have different forms of opsin (combined with retinal)? |
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Definition
| Enables uv, blue, red and green light to be detected. |
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