The majority of proteins located in mitochondria are not encoded by mtDNA, they are encoded by genes in the nucleus and are imported into the mitochondria after their synthesis in the cytosol.

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#Unit 4. Cell Communication and Cell Signaling

Classes of Antibody Heavy Chains

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#Unit 4. Cell Communication and Cell Signaling

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#Unit 4. Cell Communication and Cell Signaling

Antibody Light Chains

Light chain was extremely variable, whereas the sequence of the carboxyl-terminal half could be classified into one of two major sequence types.

κ (kappa) 

λ (lambda) 

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#Unit 4. Cell Communication and Cell Signaling

Chromosomal locations of immunoglobulin genes

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#Unit 4. Cell Communication and Cell Signaling

IgM antibodies are produced first in a humoral immune response and tend to be of low affinity.

IgM molecules form pentamers that are stabilized by a single J-chain molecule.

This higher avidity of the pentamer compensates for the low affinity

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#Unit 4. Cell Communication and Cell Signaling

IgG efficiently opsonizes pathogens for engulfment by phagocytes and activates the complement system. The affinity of the individual antigen binding sites for their antigen is therefore critical for the effectiveness of these antibodies, and most of the B cells expressing these classes have been selected in the germinal centers for their increased affinity for antigen after somatic hyper mutation.