Question

How many of the following are not included in endomembrane system? Endoplasmic Reticulum, Golgi complex, Lysosome, Mitochondria, Chloroplast, Vacuoles, Peroxisomes (a) 2 (b) 3 (c) 4 (d) 5

Short answer

The answer is (c) 4. There are 4 organelles in the given list that are not part of the endomembrane system: Mitochondria, Chloroplast, Vacuoles, and Peroxisomes.

Step-by-step solution

List the organelles in the endomembrane system

First, list the organelles that are known to be part of the endomembrane system. These are: Nuclear Envelope, Endoplasmic Reticulum, Golgi Complex, Vesicles, Lysosomes, and Plasma Membrane.

Identify the organelles not in the list

Next, compare this list with the organelles given in the exercise: Endoplasmic Reticulum, Golgi complex, Lysosome, Mitochondria, Chloroplast, Vacuoles, and Peroxisomes. It can be seen that Mitochondria, Chloroplast, Vacuoles, and Peroxisomes are not part of the endomembrane system

Count the number of non-endomembrane system organelles

Count the number of organelles identified in Step 2 that are not part of the endomembrane system. There are four such organelles: Mitochondria, Chloroplast, Vacuoles, and Peroxisomes

Key concepts

Cell Organelles

Cell organelles are like the mini-organs within a cell. Each organelle has a specific function that contributes to the cell's overall operation. Think of them as the worker bees inside a beehive. They might have different roles, but all are essential for maintaining the hive's functionality.

• Nucleus: The control center of the cell, housing DNA.
• Endoplasmic Reticulum (ER): Either smooth or rough, helps in synthesizing proteins and lipids.
• Golgi Complex: Acts as the shipping center, modifying and packaging proteins.
• Lysosomes: The digestive system, breaking down waste.
• Mitochondria & Chloroplast: Powerhouses and food producers, respectively, though not part of the endomembrane system.

Understanding these cell organelles is key to grasping the broader workings of cellular biology.

Mitochondria

Mitochondria are often referred to as the "powerhouses" of the cell. They are not part of the endomembrane system. Their primary function is to generate energy in the form of adenosine triphosphate (ATP) through a process known as cellular respiration.
This process involves the breaking down of glucose and other molecules. The mitochondrial matrix and inner membrane play crucial roles in ATP synthesis through the electron transport chain.
Mitochondria have their own DNA, which is similar to bacterial DNA, hinting at their evolutionary origin – an ancient symbiotic relationship with early eukaryotic cells. This makes them semi-autonomous cell organelles capable of replicating independently of the cell.

Chloroplast

Chloroplasts are specialized organelles found mainly in plant cells and some algae. They are not included in the endomembrane system. Chloroplasts are responsible for photosynthesis, the process by which light energy is converted into chemical energy stored in glucose.
They contain chlorophyll, the green pigment that captures sunlight. The inner membrane system of chloroplasts, called thylakoids, is where the light reactions of photosynthesis occur.
Like mitochondria, chloroplasts have their own DNA and share a similar evolutionary history, suggesting endosymbiosis. This means they likely originated from a symbiotic relationship between a photosynthetic bacterium and a primitive eukaryotic cell.

Lysosomes

Lysosomes are small sacs of digestive enzymes found within cells, and they are indeed part of the endomembrane system. Their primary role is to break down macromolecules into their basic building blocks, which the cell can then reuse.
Think of lysosomes as the recycling center of the cell. They help in disposing waste and cleaning up the cell by digesting unwanted or malfunctioning components.
The enzymes within lysosomes are able to break down proteins, lipids, carbohydrates, and nucleic acids. Because of this digestive function, the membrane surrounding lysosomes keeps these powerful enzymes contained, preventing damage to other parts of the cell.