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bio 3/4
cellular signals
| Question | Answer |
|---|---|
| What are the three modes of transmission? | Autocrine is cell targets itself or same type of cell that secreted them. Paracrine is cell secretes molecules that act on nearby cells, eg. Neurotransmitters. Endocrine is signal molecules act on cells far away, eg. Hormones. |
| What are plant hormones? | Triggered by a variety of stimuli and produced in small amounts. Mainly produced in growing regions of shoots and roots, and transmitted via diffusion in xylem, phloem or cell-cell. |
| What are neurotransmitters? | Hydrophilic molecules made by neurons; dendrites receive neurotransmitters from other cells. Transmitted through paracrine. |
| What are cytokines? | Hydrophilic signalling molecules, communication between immune cells, sources are macrophages, T and B lymphocytes, eg. Interferons and interleukins. Paracrine, autocrine or endocrine mode of transmission. |
| What are pheromones? | Produced by specialised cells, excreted outside organism and diffuse through the air. Influence behaviour or physiology of other individuals. |
| What is step 1 of the stimulus-response model? | Reception involves detection of signalling molecule by a cytokine. The receptor can be surface, cytosol or nucleus, it depends on whether hydrophobic or hydrophilic signal molecule. |
| What is step 2 of the stimulus-response model? | Transduction involves converting signal into a useful form to be relayed through the cell. Can be one step (signal molecule binds and response is seen), or multi-stepped (cascade, pathway chain of events for a final response). |
| What is step 3 of the stimulus-response model? | Response is initiated in the nucleus, cytosol or plasma membrane, eg. Transduction or enzyme activation. |
| What are hydrophobic signalling molecules? | Lipid based molecules involved in gene regulation that easily diffuse through the plasma membrane and bind intracellularly, eg. Steroids. |
| What are hydrophilic signalling molecules? | Signalling molecule binds to extracellular part of receptor which changes shapes of intracellular part and activates the cellular response, eg. peptide hormones, neurotransmitters, cytokine. This is also may include cascades or secondary messengers. |
| What is the cellular response to hydrophobic molecules? | In the nucleus; gene regulation, eg. protein production. In the cytosol; inhibition or activation of enzymes, eg. Insulin intake. In the plasma membrane; regulating entry and exit of substances, eg. opening/closing of channels. |
| What is apoptosis? | A natural, regulatory process to regulate the number of cells in your body or remove cells that may be damaged or are no longer required, eg. webbing in hands and toes during embryonic development. Once triggered, apoptosis cannot be stopped. |
| Why do cells apoptose? | End of natural life, dysfunctional, damaged or disease, excessive in number, has not fully developed, more than required, no longer needed. |
| What are the apoptosis steps? | Separation from neighbouring cells, cytoskeleton collapses, cell shrinks, nucleus and organelles breakdown, blebbing, apoptotic bodies form, phagocytosis of these apoptotic bodies. |
| What is the intrinsic or mitochondrial pathway? | Occurs if serious internal cell damage, caused by radiation, virus, toxins or damaged DNA. |
| What are the intrinsic pathway steps? | Pores form in outer membrane of mitochondria, cytochrome c released into cytoplasm, activates caspase-9, caspase-9 activates caspase-3, 6, and 7, ‘executioners’ dismantle cell, contents packaged into apoptotic bodies and removed by phagocytosis. |
| What is the extrinsic or death receptor pathway? | All cells possess death receptors on their plasma membrane, and these receptors respond to cytokines. Once cytokines bind, the signal is transduced into the cell which leads to the caspase activation. |
| What is a caspase? | Enzymes that physically breakdown components of cells during apoptosis. |
| What is the function of caspases? | Cleave DNA, degrade nuclear proteins, dismantles cell cytoskeleton, initiate blebbing, breakdown of organelles. |
| What is excessive apoptosis? | The excessive loss of tissue, eg. Alzheimer’s is the apoptosis in brain cells. Parkinson’s disease is the uncontrolled apoptosis due to a mutation. AIDS is the apoptosis of T helper cells. |
| What is inhibited apoptosis? | Cancers in uncontrolled cell division, herpes blocks apoptosis process, rheumatoid arthritis is the excessive production of synovial cells after blocking of apoptosis. |
Created by:
lucyokane
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