Cell Biology and Structure

The cell wall is the rigid outer layer made of cellulose in plant cells that provides structural support and protection. It lies outside the plasma membrane. Plasmodesmata are channels connecting cells. Lamella is the middle lamella between cells. Unit membrane refers to the membrane structure itself.

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.

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.

The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cell) of many animals. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation.

Lysosomes are cellular organelles that contain acid hydrolase enzymes to break down waste materials and cellular debris. They are found in animal cells, while in yeast and plants the same roles are performed by lytic vacuoles.Lysosomes digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria.

A thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen.

Ribosomes occur, both as free in the cytoplasm and as associated with endoplasmic reticulum. Ribosome are of 80 S kind. There are two subunits. Ribosomal RNA and proteins occur in the constitution of ribosomes.

 In plant cells, a large vacuole occurs which is surrounded by a semipermeable membrane called tonoplast. The membrane around vacuoles in animal cells is made up of lipoprotein. Normally, vacuoles do not occur in animal cells.