Cell Biology and Structure

Eukaryotic cells contain larger 80S ribosomes in their cytoplasm and on the rough endoplasmic reticulum, whereas prokaryotic cells contain smaller 70S ribosomes. Although eukaryotic organelles like mitochondria and chloroplasts contain 70S ribosomes, 80S ribosomes are the defining cytoplasmic ribosomes of eukaryotes.

Animal cells may contain small, temporary vacuoles, but they do not have the large, permanent central vacuole characteristic of plant cells. Ribosomes, lysosomes, and DNA are all present in animal cells.

In eukaryotic cells, DNA replication takes place inside the nucleus, not in the cytoplasm. Metabolic reactions, organelle suspension, and translation (protein synthesis) by free ribosomes all occur within the cytoplasm.

Chloroplasts are the sites of photosynthesis and are found in plant cells (and some algae) but not in animal cells. Peptidoglycan cell walls are found in bacteria, small vacuoles can be found in animal cells, and both plant and animal cells have a nucleus.

Chloroplasts carry out photosynthesis in plant cells, using light energy, water, and carbon dioxide to synthesize glucose. Mitochondria, conversely, break down glucose to produce ATP.

Specialized structures within a cell that perform specific functions are called organelles (literally 'little organs'). Examples include the nucleus, mitochondria, and ribosomes.

Both plant and animal cells are eukaryotic because they contain a membrane-bound nucleus and other membrane-bound organelles. This distinguishes them from prokaryotic cells, such as bacteria.

Cellulose is a complex carbohydrate that provides structural support and rigidity, and it is the primary component of plant cell walls. It is not found in the cell membrane, cytoplasm, or nucleus.

Lysosomes are membrane-bound organelles containing hydrolytic enzymes that break down waste materials, foreign debris, and worn-out cellular components.

Plant cells typically contain a single, large central vacuole that stores water and maintains turgor pressure to keep the plant upright. In contrast, animal cells may contain multiple small, temporary vacuoles, but not a large central one.

The Golgi apparatus is responsible for modifying, sorting, and packaging proteins received from the rough endoplasmic reticulum. The nucleus houses genetic material, while the smooth and rough ER are primarily involved in lipid and initial protein synthesis, respectively.

The cell membrane (or plasma membrane) is selectively permeable, meaning it regulates the passage of substances into and out of the cell. The cell wall provides structural support but is fully permeable, while the nucleus and mitochondria have different metabolic and genetic functions.

Ribosomes (such as 70S ribosomes in prokaryotes, mitochondria, and chloroplasts) are macromolecular complexes of RNA and proteins and do not possess a surrounding lipid membrane. The nucleus, mitochondria, and chloroplasts are all bound by double membranes.