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6.1: Exocytosis - Biology

6.1: Exocytosis - Biology


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Learning Outcomes

Identify the steps of exocytosis

The reverse process of moving material into a cell is the process of exocytosis. Exocytosis is the opposite of the processes discussed in the last section in that its purpose is to expel material from the cell into the extracellular fluid. Waste material is enveloped in a membrane and fuses with the interior of the plasma membrane. This fusion opens the membranous envelope on the exterior of the cell, and the waste material is expelled into the extracellular space (Figure 1). Other examples of cells releasing molecules via exocytosis include the secretion of proteins of the extracellular matrix and secretion of neurotransmitters into the synaptic cleft by synaptic vesicles.

A summary of the cellular transport methods discussed is contained in Table 1, which also includes the energy requirements and materials transported by each.

Table 1. Methods of Transport, Energy Requirements, and Types of Material Transported
Transport MethodActive/PassiveMaterial Transported
DiffusionPassiveSmall-molecular weight material
OsmosisPassiveWater
Facilitated transport/diffusionPassiveSodium, potassium, calcium, glucose
Primary active transportActiveSodium, potassium, calcium
Secondary active transportActiveAmino acids, lactose
PhagocytosisActiveLarge macromolecules, whole cells, or cellular structures
PinocytosisActiveSmall molecules (liquids/water)
Receptor-mediated endocytosisActiveLarge quantities of macromolecules
ExocytosisActiveWaste materials, proteins for the extracellular matrix, neurotransmitters

In Summary: Exocytosis

Exocytosis in many ways is the reverse process from endocytosis. Here cells expel material through the fusion of vesicles with the plasma membrane and subsequent dumping of their content into the extracellular fluid.


Watch the video: Cell Transport (May 2022).