This is a theory proposed by Lynn Margulis that states that mitochondria arose from an endosymbiotic event where a bacterium was engulfed by a host cell and was still viable. Some of the evidence for this theory is that mitochondria have their own DNA which is circular and has 70S ribosomes which are the bacterial ribosomes.

Endosymbiotic Theory

The mitochondria is responsible for aerobic respiration in eukaryotes. It contains two lipid membranes which are the inner and outer membranes. The inner membrane is the site for the electron transport chain for aerobic respiration. The mitochondrial matrix is also an important site for metabolic enzymes and the mitochondrial DNA.

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Eukaryotes have membrane-bound organelles, each with their own structure and function. Organelles commonly found in eukaryotes include:
- Nucleus
- Endoplasmic Reticulum
- Golgi Apparatus
- Lysosome
- Vacuole
- Mitochondria
- Chloroplast
- Peroxisomes

Organelles Commonly Found in Eukaryotes

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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.

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The nucleus is a defining characteristic of eukaryotes. The nucleus has a nuclear membrane that contains the DNA genome of a eukaryotic cell.The DNA is organized in the nucleus because it is condensed with histone proteins.

Nucleus

The endoplasmic reticulum is responsible for synthesizing molecules in the cell. It is make of a lipid bilayer and is connected by tubules and flat sacs called cisternae. 

There are two types of endoplasmic reticulum with their own molecules they synthesize. 
- Rough endoplasmic reticulum
- Smooth endoplasmic reticulum

Endoplasmic Reticulum

The Golgi apparatus contains enzymes that modify lipids and proteins that were transported from the endoplasmic reticulums. It can typically modify them by making them glycolipids or glycoproteins which are important for the plasma membrane. The Golgi apparatus has a stacked disk appearance and it is made of a lipid bilayer.

The Golgi Apparatus

Lysosomes are organelles that contain digestive enzymes. These enzymes break down parts of the cell that are not needed for the cell anymore such as damaged organelles or debris. 

Lysosomes

Vacuoles are formed off of the plasma membrane in a process called phagocytosis.

Vacuole

Mitochondria

Peroxisomes produce hydrogen peroxide which is needed to break down amino acids and uric acid. Peroxisomes also have catalase which degrades hydrogen peroxide. Peroxisomes, like lysozymes, are important in compartmentalizing degradation molecules to protect the cell. 

Peroxisome

A multi-membrane organelle where photosynthesis occurs in eukaryotes

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