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which structure will form when a primitive cell engulfs an aerobic bacterium?

which structure will form when a primitive cell engulfs an aerobic bacterium?

Which structure will form when a primitive cell engulfs an aerobic bacterium?

which structure will form when a primitive cell engulfs an aerobic bacterium?

When a primitive cell engulfs an aerobic bacterium, the structure that will form is the mitochondria. This process is explained by the endosymbiotic theory, which suggests that mitochondria and chloroplasts in today's eukaryotic cells were once separate prokaryotic microbes that were engulfed by primitive cells.

Mitochondria are believed to have evolved from aerobic bacteria that were taken in by early eukaryotic cells around 1.5 billion years ago4. The endosymbiotic theory proposes that these bacteria form a symbiotic relationship with the host cell, eventually losing their cell wall and much of their DNA.

When a primitive cell engulfs an aerobic bacterium, it can lead to the formation of a symbiotic relationship known as endosymbiosis. During endosymbiosis, the primitive cell provides a protective environment for the aerobic bacterium, allowing it to survive and replicate. Over time, the aerobic bacterium becomes integrated into the cellular structure of the primitive cell, leading to the formation of a new organelle called a "mitochondrion. The mitochondrion plays a crucial role in cellular respiration, the process by which cells generate energy.

Here's the truly fascinating part: according to the endosymbiotic theory, this wasn't just the bacterium being trapped.

1. Primitive Cells and Bacterial Engulfment

Billions of years ago, Earth was a hotbed of simple life forms. Among these were primitive cells, basic entities with limited internal structures. These early cells had a remarkable ability: they could engulf other smaller cells or particles. Imagine a tiny cell engulfing a bacterium—a pivotal moment in the evolution of life!

2. The Aerobic Bacterium Encounter

One day, a primitive cell encountered an aerobic bacterium—a bacterium that thrived in the presence of oxygen. Instead of digesting it, the primitive cell decided to form a symbiotic relationship. It enveloped the bacterium, creating a cozy home within its own cytoplasm.

3. The Birth of Mitochondria

This union was transformative. Over time, the engulfed bacterium adapted to its new environment. It provided energy to the host cell by performing aerobic respiration, a process that generates energy using oxygen. In return, the host cell sheltered and nourished it.

And thus, the mitochondrion was born!

4. Mitochondria: Powerhouses of the Cell

Mitochondria are now essential organelles in eukaryotic cells (cells with a nucleus). Here’s why they’re so crucial:

- Energy Production: Mitochondria generate energy through cellular respiration. They convert nutrients (like glucose) and oxygen into adenosine triphosphate (ATP), the cell’s energy currency.

- Double Membrane Structure: Mitochondria have a double membrane—a relic of their bacterial origin. The outer membrane resembles the primitive cell’s membrane, while the inner membrane houses intricate machinery for ATP production.

- Own DNA: Unlike other organelles, mitochondria carry their own genetic material. This DNA encodes essential proteins involved in energy production.

- Endosymbiotic Theory: The story of mitochondria exemplifies the endosymbiotic theory. According to this theory, eukaryotic cells evolved from primitive cells that engulfed bacteria. These once-independent organisms merged, flourished, and evolved into a single, complex cell.

5. Easy Recap

Think of mitochondria as the cell’s power plants. They’re like tiny factories churning out ATP, keeping our cells alive and kicking. So next time you feel energetic, thank your mitochondria—they’ve been working tirelessly for billions of years.

How did mitochondria evolve in eukaryotic cells?

Mitochondria, the energy-producing organelles in eukaryotic cells, are believed to have evolved from free-living alpha-proteobacteria through the process of endosymbiosis, where one symbiotic species is taken inside the cytoplasm of another symbiotic species and both become endosymbiotic.

The endosymbiotic theory proposes that an ancestral cell with some membrane compartmentalization engulfed a free-living aerobic prokaryote, specifically an alpha-proteobacterium, around 1.5 billion years ago when the amount of oxygen increased in the atmosphere.

The evolution of mitochondria in eukaryotic cells is a complex process that is still being studied and debated. Some researchers suggest that the evolution of the first eukaryotes involved more than two partners and happened more gradually than previously thought

However, others argue that the acquisition of the mitochondrion was the spark that ignited the evolution of eukaryotic cells, leading to the development of complex organisms, including plants, animals, and humans. Fresh evidence from genomics and cell biology may help resolve the debate and fill in the knowledge gaps about the origin of complex cells.

What is the function of chloroplasts in eukaryotic cells?

What is the function of chloroplasts in eukaryotic cells?

The function of chloroplasts in eukaryotic cells is to facilitate photosynthesis, the process by which light energy is converted into chemical energy. Chloroplasts are organelles found in plant cells and some algae responsible for capturing light energy and using it to produce energy-storing sugars like glucose. During photosynthesis, chloroplasts absorb sunlight through pigments like chlorophyll a and b, which are essential for this process.

Double Membrane: Chloroplasts possess a double membrane, an outer and an inner membrane. This creates distinct compartments within the organelle.

Thylakoids: Inside the chloroplast are stacks of flattened sacs called thylakoids. These contain chlorophyll, the green pigment that absorbs light energy.

Grana: Thylakoids are arranged in interconnected stacks called grana (singular: granum).

Stroma: The fluid surrounding the thylakoids is the stroma. It contains enzymes, DNA, and other materials necessary for photosynthesis.

The Process of Photosynthesis

Photosynthesis occurs in two primary stages:

Light-Dependent Reactions:

These reactions happen within the thylakoid membranes.

Chlorophyll absorbs light energy, which excites electrons.

This energy is used to split water molecules, releasing oxygen (O2) and generating energy-carrying molecules (ATP and NADPH).

Light-Independent Reactions (Calvin Cycle):

These reactions occur in the stroma.

The ATP and NADPH from the light reactions power the conversion of carbon dioxide (CO2) into glucose (sugar), the plant's food source.


The process of a primitive cell engulfing an aerobic bacterium is a key step in the endosymbiotic theory. This theory explains the origin of mitochondria, the energy-producing organelles within eukaryotic cells. The engulfed bacterium eventually formed a mutually beneficial relationship with the host cell, evolving into the mitochondria we know today.


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