Give two examples of situations where a cell might use:
Phagocytosis
exocytosis
Phagocytosis:
1. During an infection, white blood cells (such as macrophages) can use phagocytosis to engulf and destroy invading bacteria or pathogens. The cell extends its plasma membrane around the foreign particle, forming a phagosome, which then fuses with lysosomes to digest the engulfed material.
2. In unicellular organisms like amoeba and Paramecium, phagocytosis is employed for obtaining food. These organisms engulf food particles, such as bacteria or algae, by extending their pseudopodia and enclosing the particles within phagosomes. The food is then broken down and digested within lysosomes.
Exocytosis:
1. During neurotransmission, after receiving a signal, nerve cells release neurotransmitters into the synaptic cleft by exocytosis. The vesicles containing neurotransmitters fuse with the plasma membrane of the presynaptic neuron, allowing the release of the neurotransmitters into the extracellular space to bind to receptors on the postsynaptic neuron.
2. Secretory cells, such as those in the pancreas or salivary glands, use exocytosis to release enzymes or hormones into the bloodstream. These cells produce vesicles filled with these substances, and upon receiving the appropriate signal, the vesicles fuse with the cell membrane, releasing their contents into the surrounding tissue or bloodstream.