Cell Biology Fundamentals

Cytoplasmic streaming is indeed the movement of the cytoplasm within a cell. This internal circulation helps distribute nutrients, organelles, and other materials throughout the cell.

Leucoplasts are colorless plastids that primarily store starch, lipids, or proteins. They are found in non-photosynthetic tissues like roots and are specialized for storage functions.

Chloroplasts do contain their own DNA, which is evidence supporting the endosymbiotic theory. This DNA allows chloroplasts to replicate independently and code for some of their own proteins.

Lysosomes are NOT the powerhouse of the cell - that function belongs to mitochondria. Lysosomes contain digestive enzymes and are responsible for breaking down waste materials and cellular debris.

Not all living cells have a cell wall. Animal cells lack cell walls, while plant cells, fungi, and most bacteria do have them. The cell wall provides structural support but is not universal.

All living cells do have a cell membrane (plasma membrane). The cell membrane is a fundamental feature of all cells, providing boundary, regulating transport, and maintaining cellular homeostasis.

Peptidoglycan consists of sugar derivatives (N-acetylglucosamine and N-acetylmuramic acid) cross-linked by short peptide chains of amino acids. This mesh-like structure provides strength to bacterial cell walls.

Messenger RNA (mRNA) carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm, where it serves as a template for protein synthesis. DNA remains in the nucleus as the permanent genetic store.

Normal human somatic cells contain 46 chromosomes arranged in 23 pairs - one set of 23 from each parent. This diploid number is characteristic of most human cells except gametes which are haploid.

Muscle cells require continuous energy (ATP) for contraction and relaxation. Mitochondria are the powerhouses of the cell producing ATP through cellular respiration, so cells with high energy demands like muscle cells contain the most mitochondria.

The cell membrane (also called plasma membrane) surrounds all organelles as well as the entire cell. It is selectively permeable and regulates the movement of substances in and out. The nuclear membrane specifically surrounds only the nucleus.

Both bacteria (bacilli) and honey bees (as eukaryotes) have ribosomes for protein synthesis and DNA as their genetic material. Option A is wrong because bacteria have DNA not RNA as genetic material. Option B is wrong because only eukaryotes have lysosomes. Option D is wrong because bacteria lack a defined nucleus.

Robert Hooke discovered cells in 1665 while examining cork slices under a microscope. He observed tiny box-like structures and named them cells because they reminded him of monks' cells in a monastery.

A hen's egg is a single cell (the yolk is the actual cell) large enough to be visible to the naked eye. Most neurons are microscopic, and while giant squid neurons are exceptionally long, they are still too thin to be clearly visible without magnification.

Human egg cells (oocytes) contain centrioles which help organize the spindle apparatus during cell division. Option A is wrong because animal cells lack cell walls. Option C is wrong because tonoplast is found in plant cells. Option D is wrong because mature human eggs have minimal vacuoles.

Robert Brown discovered the nucleus in 1831 while studying orchid root cells. He observed a dark, dense structure in each cell and named it the nucleus. This was a key observation that contributed to understanding cell structure.

Cell theory states that the cell is the basic structural and functional unit of all living organisms. Option A is wrong because many cells (like animal cells) lack cell walls. Option B is wrong because cells arise only from pre-existing cells (omnis cellula e cellula). Option D is wrong because red blood cells lack nuclei.

Amoeba exhibits cellular level of organization because it is a unicellular organism - all life functions (nutrition, respiration, reproduction) occur within a single cell. Tissue, organ, and organ system levels require multicellular organisms with specialized cell groups.

Prokaryotes are unicellular organisms lacking a membrane-bound nucleus and organelles. Mycoplasma, bacteria, and cyanobacteria are all prokaryotic organisms. Algae and fungi are eukaryotic, having true nuclei and organelles, while viruses are not even cells.

Nerve cells (neurons) are post-mitotic, meaning they lose their ability to divide after reaching maturity. This is why brain damage from injury or stroke is often permanent. Blood cells, muscle cells, and bone cells retain regenerative capacity through stem cells.

Plants grow primarily through cell division (mitosis) in meristematic tissues, which increases cell number. While individual cells do expand (increase in size), the fundamental growth mechanism is the production of more cells through cell division.

Centrioles are cylindrical organelles that organize microtubules and play essential roles in cell division. They form centrosomes and organize the mitotic spindle during mitosis and meiosis, ensuring proper chromosome separation.

Cell sap refers to the fluid inside plant cell vacuoles, which is a solution of water containing dissolved salts, sugars, and other substances. This solution helps maintain turgor pressure and stores nutrients and waste products.

In unicellular organisms like protozoa (e.g., Amoeba), food vacuoles are responsible for digesting food through intracellular digestion. This is analogous to how multicellular organisms have entire digestive systems to break down food.

Humans are multicellular organisms made up of trillions of cells, each of which is eukaryotic (having a membrane-bound nucleus and organelles). This distinguishes us from unicellular organisms and prokaryotes (which lack nuclei and organelles).