Final answer:
The nucleus houses DNA and oversees cellular functions; chloroplasts perform photosynthesis in plant cells; mitochondria generate energy for the cell; and the endoplasmic reticulum is involved in protein and lipid synthesis.
Step-by-step explanation:
Explanation of Cell Organelles
Nucleus: The nucleus is often referred to as the control center of the cell because it houses the cell's DNA and directs the synthesis of proteins and ribosomes, the cellular organelles responsible for protein synthesis.
Chloroplast: Found only in plant cells and some algae, chloroplasts are the sites of photosynthesis. They contain a green pigment called chlorophyll, which captures the energy of sunlight to create sugars from water and carbon dioxide.
Mitochondria: Known as the power plants of the cell, mitochondria generate ATP, the cell's main energy currency, through a process called cellular respiration. They are unique in having their own DNA and double membrane, supporting the endosymbiotic theory, which suggests mitochondria were once independent prokaryotic organisms.
Endoplasmic Reticulum (ER): The ER is an extensive network of membranes that forms tubes and sacs throughout the cytoplasm of eukaryotic cells. The rough endoplasmic reticulum is studded with ribosomes and involved in protein synthesis, while the smooth endoplasmic reticulum lacks ribosomes and is involved in lipid synthesis and detoxification processes.