Cell Biology and Structure

Ribosomes are non-membranous organelles composed of ribosomal RNA and proteins. They are the site of protein synthesis and are not enclosed by any membrane, unlike organelles such as sphaerosomes and glyoxysomes which are membrane-bound.

The ability of cancer cells to invade into a new organ is called metastasis .

A nucleoid is the region within prokaryotic cells where DNA is located, lacking a surrounding nuclear membrane. It is not a true nucleus but contains the genetic material. Capsid is the protein coat of viruses. Chromatin is the complex of DNA and proteins in eukaryotic nuclei. Nucleoplasm is the gel-like material within the nucleus.

Protoplasm is called the physical basis of life because it performs all vital activities - metabolism, growth, reproduction, response to stimuli. It includes cytoplasm and nucleoplasm. Cytoplasm is just the portion outside the nucleus. Kinoplasm and ectoplasm are specialized regions of cytoplasm involved in movement and structural functions respectively, not the entire living substance.

Chromosomes are called vehicles of heredity because they carry genes (DNA) that transmit traits from parents to offspring. They contain the genetic information that determines inherited characteristics. Ribosomes are for protein synthesis. Chromatin is the relaxed form of DNA/proteins. The nucleolus produces ribosomes.

Mature red blood cells (erythrocytes) in mammals lose their nucleus during development to make more space for hemoglobin, which carries oxygen. This adaptation allows RBCs to be flexible enough to squeeze through tiny capillaries. Liver cells, stomach cells, and karyotype (which is a chromosome arrangement, not a cell type) all contain nuclei.

Ribosomes are the cellular organelles where protein synthesis (translation) occurs - they read mRNA and assemble amino acids into polypeptide chains. The endoplasmic reticulum provides surface for ribosomes, Golgi modifies proteins, and mitochondria produce energy, but only ribosomes actually build proteins.

Lysosomes contain digestive enzymes that break down cellular waste, damaged organelles, and foreign materials. When a cell is damaged or dying, lysosomes can rupture and release these enzymes, effectively digesting the cell from within - hence the nickname 'suicide bags' or 'suicide sacs'.

The inner mitochondrial membrane folds inward to create cristae (singular: crista), which dramatically increase surface area for ATP production machinery. These shelf-like projections house the electron transport chain and ATP synthase enzymes essential for cellular respiration.

Eukaryotic 80S ribosomes consist of a large 60S subunit and a small 40S subunit (60+40=80). The 'S' stands for Svedberg units, which measure sedimentation rate during centrifugation, not molecular weight. Prokaryotic 70S ribosomes have 50S and 30S subunits.

Cyclosis is the scientific term for the circular movement of cytoplasm within a cell, often observed around the central vacuole in plant cells. This streaming motion helps distribute nutrients, organelles, and other materials throughout the cell.

A ribosome is the component of a biological cell that creates proteins from all amino acids and RNA representing the protein. One of the central tenets of biology, often referred to as the central dogma of molecular biology, is that DNA is used to make RNA, which is used to make protein.

A mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 10 micrometers in diameter. Mitochondria are sometimes described as cellular power plants because these generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Mitochondria are found in both plant and animal cells and is the site of cellular respiration.They are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into adenosine triphosphate (ATP). ATP is the chemical energy currency of the cell that powers the cell's metabolic activities.