Secondary endosymbiosis of chloroplasts is an evolutionary process where a cell engulfed a red or green algal cell already containing a primary chloroplast, subsequently destroying everything except the chloroplast and potentially the original cell's membrane, leaving three or four membranes around the chloroplast.

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Algal chloroplasts can vary in their membrane count, reflecting secondary or tertiary endosymbiotic events, and they may contain starch-synthesizing and starch-storing structures called pyrenoids.

Algae Chloroplasts

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

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Pyrenoids are structures inside of algal chloroplasts that can synthesize and store starch.

Pyrenoids

Primary chloroplasts possess two membranes, with one originating from the cyanobacteria engulfed by the ancestral eukaryotic cell, and the other originating from the plasma membrane of the engulfing host cell.

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