Cell Biology and Structure

Chloroplasts are organelles found exclusively in plant cells and some algae, where they conduct photosynthesis. Ribosomes, nuclei, and plasma membranes are universal features found in both plant and animal cells.

The endoplasmic reticulum (ER) is a complex network of membrane-bound tubules and sheets that extends throughout the cytoplasm. It provides a large surface area for cellular activities like protein synthesis and lipid metabolism. Vacuoles are storage sacs, chloroplasts are for photosynthesis, and mitochondria produce energy.

Plastid is absent in an animal cell. The plastid is a major double-membrane organelle, found among others, in the cells of plants and algae.

Lysosomes are membrane-bound sacs containing digestive enzymes but lack DNA. Plastids (including chloroplasts) and mitochondria have their own DNA from their evolutionary origin as independent prokaryotes. The nucleus contains the main cellular DNA.

Mitochondria are called the powerhouse of the cell because they generate ATP through cellular respiration, releasing energy from organic compounds. Lysosomes digest waste, plastids (in plants) handle photosynthesis, and vacuoles are storage compartments.

Cytoplasm is the gel-like, jelly-like fluid that fills the cell and suspends organelles. It provides the medium where cellular processes occur and organelles are embedded or suspended. The nucleus is the control center, lysosomes digest waste, and vacuoles store materials.

Mitochondria are membrane-bound organelles found only in eukaryotic cells, absent in prokaryotes. Prokaryotes do have cell membranes, cytoplasm, and ribosomes (70S type). The lack of mitochondria is a key distinguishing feature of prokaryotic cells.

Both prokaryotic and eukaryotic cells contain chromosomes carrying genetic material, though they differ in structure (circular vs linear) and location (nucleoid vs nucleus). Prokaryotes lack a nuclear membrane and have circular chromosomes. Respiratory enzymes on the cell membrane are a prokaryotic feature, not shared by eukaryotes.

 Animal cells differ from plant cells in that, they do not have cell wall.

The Golgi apparatus consists of stacked, flattened membrane-bound sacs called cisternae. These are arranged in parallel bundles and modify, sort, and package proteins and lipids. Tubules are thin tubes, vacuoles are storage sacs, and lysosomes contain digestive enzymes.

The shape and size of a cell is directly related to its specific functions. Cells adapt their structure to perform specialized tasks efficiently - like nerve cells being long for signal transmission, or red blood cells being disc-shaped for oxygen transport. Appearance is just a visual characteristic, not the determining factor. Nucleus and location are cell components, not functional determinants.

Unchecked proliferation of cell type present in the epithelium is called carcinoma.

The spread of cancerous cells to distant sites is called metastasis.

The genetic material in HIV is single-stranded RNA.

The malignant growth of epithelial tissue that covers the body organs is called carcinoma.