Cell Biology Fundamentals

Phosphorus is a key structural component of DNA and RNA. DNA (deoxyribonucleic acid) is a nucleic acid, and its backbone contains phosphate groups which contain phosphorus. Proteins contain nitrogen but no phosphorus in their basic structure. Cytochrome is a protein, and carbohydrates contain carbon, hydrogen, and oxygen only.

Ribosomes are the cellular structures where protein synthesis occurs. They read mRNA and assemble amino acids into protein chains. Lysosomes break down waste materials. Mitochondria produce energy (ATP). Endoplasmic reticulum modifies proteins but the actual synthesis happens at ribosomes (which can be free or attached to the ER).

Chlorophyll contains magnesium at its center, which is essential for photosynthesis. The magnesium ion helps absorb light energy. Iron is found in hemoglobin, not chlorophyll. Manganese is a micronutrient for plants but not part of chlorophyll. Calcium is important for cell walls but not a chlorophyll component.

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells.

Unicellular refers to organisms that consist of a single cell, such as bacteria, protozoa, and some algae. Viruses are not considered living organisms as they cannot reproduce independently without a host cell.

Animal cells contain lysosomes for waste digestion and centrosomes for organizing cell division, which are generally absent in plant cells. Both cell types share mitochondria for energy production and ribosomes for protein synthesis.

Proteins are the most abundant organic molecules in cytoplasm, serving as enzymes that catalyze reactions and as structural components. While water is the major component overall, it's inorganic, and lipids and sugars are present in smaller amounts than proteins.

The plasma membrane controls the movement of water, ions, nutrients, and waste products into and out of the cell through selective permeability. It does not synthesize proteins (that's ribosomes) or specifically protect plant cell organelles (that's the cell wall's job).

Bacteriophages are viruses that specifically infect bacteria, using bacterial machinery to replicate themselves. They are not bacteria themselves, nor are they multicellular organisms like worms or birds.

Protoplasm encompasses all living parts of the cell: the plasma membrane, cytoplasm, and nucleus. The cell wall is an extracellular structure in plants, fungi, and bacteria and is not considered part of the protoplasm.

Animal cells lack cell walls, which are rigid outer structures found in plant cells (made of cellulose), fungal cells (chitin), and bacterial cells (peptidoglycan). This allows animal cells to be more flexible and change shape.

ATP stands for adenosine triphosphate, which is the primary energy currency of the cell, providing quick energy for cellular processes. Glucose and glycogen are storage forms of carbohydrates rather than immediate quick energy molecules.

Bacillus is the correct term for rod-shaped bacteria. Vibrio are comma-shaped, cocci are spherical, so bacillus specifically describes the elongated, cylindrical shape.

Oncology is the branch of medicine that specifically studies tumors and cancer. Virology studies viruses, ornithology studies birds, and osteology studies bones.

Watson and Crick proposed the double helix structure of DNA in 1953. Khurana worked on genetic code, Mendel discovered inheritance laws, and Darwin proposed evolution.

Cyclosis (cytoplasmic streaming) in Paramecium primarily aids in the movement and circulation of food vacuoles during digestion. It distributes nutrients but is not primarily for excretion, locomotion, or reproduction.

Robert Brown discovered the nucleus in 1831 while studying plant cells. Robert Hooke discovered cells, Strasburger discovered chromosomes, and Von Mohl named the protoplasm.

ATP (Adenosine Triphosphate) is the primary energy storage molecule in cells. DNA stores genetic information, NADP is involved in photosynthesis, and ATP is the universal energy currency.

PPLO (Pleuropneumonia-like organisms), now called Mycoplasma, are the smallest known cells (0.1-0.3 micrometers). Viruses are smaller but not cells, and bacteria are larger.

Eukaryotic cells have a true nucleus surrounded by a double membrane and membrane-bound organelles like mitochondria and ER. Prokaryotic cells lack these features, and unicellular refers to number of cells, not cell type.