Cell Biology and Structure

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.

Mitochondria are the powerhouses of the cell, where aerobic cellular respiration takes place to convert biochemical energy from nutrients like glucose into adenosine triphosphate (ATP).

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.

Eukaryotic cells store their primary genetic material inside a membrane-bound nucleus, whereas prokaryotic cells lack a nucleus and keep their DNA in an unbound nucleoid region. This distinction is one of the defining differences between eukaryotes and prokaryotes.

Photosynthesis occurs inside specialized organelles called chloroplasts, which contain the pigment chlorophyll to absorb light energy. While leaves are the organs where this process happens, the specific cellular organelle responsible is the chloroplast. Mitochondria are responsible for cellular respiration.

The extracellular matrix is the non-living material secreted by cells that fills the spaces between them, providing structural and biochemical support. While ground substance is a component of this matrix, the complete structure containing both fibers and ground substance is the extracellular matrix. The other options are either incomplete or pop-culture references.