The <u>vesicles</u> pick up whole and partial neurotransmitters from the synaptic gap and bring them into the terminal button, where other structures recycle these neurotransmitters for future use.
Within the presynaptic terminals is where the synthesis of the small-molecule neurotransmitters takes place. A process known as slow axonal transport is responsible for moving enzymes from the neuronal cell body to the cytoplasm of nerve terminals at a rate of 0.5–5 millimetres each day. These enzymes are necessary for the production of transmitters and are produced in the neuronal cell body. Transporter proteins, which are typically located in the plasma membrane of the nerve terminal, are the ones responsible for bringing the precursor chemicals that these synthetic enzymes use into the terminal. Enzymes produce a neurotransmitter pool in the cytoplasm, which must then be loaded into synaptic vesicles using transport proteins in the vesicular membrane. Within the synaptic vesicles, the final synthetic steps of the production of certain small-molecule neurotransmitters are actually carried out.
Helper T cells are the CD4T cells that are present in the inactive form. These cells have receptors for antigens on their surface. These antigen receptors are called T-cell receptors (TCRs). The function of TCR is to recognize and bind to specific foreign antigen fragments that are presented in antigen–MHC complexes. Different helper T cells have their unique TCRs to recognize a specific antigen–MHC complex. The CD4 proteins of helper T cells also interact with the MHC antigens and help maintain the TCR–MHC coupling.
Respiration occurs when glucose (sugar produced during photosynthesis) combines with oxygen to produce useable cellular energy. This energy is used to fuel growth and all of the normal cellular functions.
