General Biology I

Gen Bio for Grade 12 TTAIL

Robert Hooke

British scientist who examined cork in 1665, found little structures he called “cellulae” (cells). Later realized these were the outer walls of dead plant cells.

Antonie van Leeuwenhoek

Dutch scientist (1670–1683) who used a refined microscope to discover moving protists and sperm, which he called “animalcules.” Improved Janssen’s microscope.

Zacharias Janssen

Credited with inventing a primitive microscope around 1590 with the help of his father Hans.

Marcello Malpighi and Nehemiah Grew

Scientists (1665–1676) who conducted separate investigations on plant cells and discovered the presence of organelles.

Robert Brown

Discovered the nucleus in 1831 and made significant discoveries about cell organelles. A breakthrough in biology.

Matthias Schleiden

German botanist (1838) who concluded all plant parts are made of cells. Authored “Contribution in Phytogenesis.”

Theodore Schwann

German zoologist (1839) who concluded all animals are made of cells. Helped unify plant and animal biology under cell theory.

Albercht von Roelliker

In 1840, stated that sperm and egg cells are composed of cells. Claimed all humans originate from cells.

Louis Pasteur

In 1849, worked on fermentation. Proved that bacterial cells come from other bacterial cells and can multiply.

Rudolf Virchow

German scientist who, in 1858, stated “Omnis cellula e cellula,” meaning all cells come from pre-existing cells.

Cell Theory

Scientific theory stating: (1) The cell is the basic unit of life; (2) All living organisms are composed of cells; (3) New cells arise from existing cells.

Plasma Membrane

Outer covering of the cell separating the internal environment from the external one. Regulates material exchange and receives signals.

Fluid Mosaic Model

Describes the plasma membrane as a mosaic of phospholipids, cholesterol, and proteins that move fluidly within the membrane.

Phospholipid

Molecule with a glycerol backbone, two fatty acid tails, and a phosphate head. Forms bilayers in biological membranes.

Hydrophilic Head

Water-attracting part of a phospholipid.

Hydrophobic Tails

Water-repelling parts of a phospholipid.

Cholesterol

Lipid made of four fused carbon rings; found with phospholipids in the membrane to stabilize fluidity.

Integral Proteins

Proteins embedded completely through the plasma membrane.

Peripheral Proteins

Proteins attached to the surface of the membrane (inner or outer side).

Cytoplasm

Region between plasma membrane and nuclear envelope. Contains organelles and macromolecules for cellular functions.

Cytosol

Gel-like fluid portion of the cytoplasm where many metabolic reactions occur.

Cytoskeleton

Provides shape and movement to the cell. Structural framework of the cytoplasm.

Nucleus

Discovered by Robert Brown; the control center of the cell that contains DNA and manages cellular activities.

Nucleolus

Dense structure in the nucleus responsible for synthesizing ribosomes.

Endomembrane System

Network of membranes and organelles in eukaryotic cells that work to produce, modify, and transport proteins and lipids.

Endoplasmic Reticulum (ER)

Interconnected sacs and tubules continuous with the nuclear envelope, involved in protein and lipid synthesis.

Rough Endoplasmic Reticulum (RER)

Has ribosomes attached; produces and modifies proteins for export.

Smooth Endoplasmic Reticulum (SER)

Lacks ribosomes; synthesizes lipids and detoxifies chemicals (especially in liver cells).

Lumen (Cisternal Space)

Hollow portion of ER tubules.

Ribosome

Site of protein synthesis. Found in both prokaryotic and eukaryotic cells, either floating freely or attached to ER.

Prokaryotic Cell

Cell without a nucleus (e.g., bacteria).

Eukaryotic Cell

Cell with a nucleus (e.g., plants, animals, fungi, protists).

Vacuole

Membrane-bound vesicle that stores substances and breaks down waste, similar to lysosomes in plant cells.

Lysosome

Organelle responsible for digesting cellular waste and foreign substances. Known as the “suicide bag” of the cell.

Autophagy

Process where cells digest their own organelles for recycling.

Peroxisome

Organelle that breaks down fatty acids and detoxifies harmful substances; combats Reactive Oxygen Species (ROS).

Reactive Oxygen Species (ROS)

Highly reactive oxygen-containing molecules that can damage cells.

Golgi Apparatus

Flattened sacs that process, package, and ship proteins and lipids from the ER.

Cis Face (Golgi)

Receiving side of the Golgi apparatus.

Trans Face (Golgi)

Shipping side of the Golgi apparatus.

Centrosome

Organizing center of microtubules, consisting of two centrioles. Important in mitosis and maintaining cell structure.

Mitochondria

Powerhouse of the cell; site of cellular respiration and ATP production.

Outer Membrane (Mitochondria)

Selective barrier with transport proteins.

Inner Membrane (Mitochondria)

Folded membrane (cristae) where ATP generation occurs.

Matrix (Mitochondria)

Innermost compartment, containing enzymes, mitochondrial DNA, and ribosomes.

Intermembrane Space (Mitochondria)

Space between the inner and outer membranes.

Adenosine Triphosphate (ATP)

Cell's main energy currency. Releases energy upon phosphate removal.

Chloroplast

Organelle in plants and algae where photosynthesis takes place.

Photosynthesis

Process of converting sunlight, carbon dioxide, and water into glucose and oxygen.

Outer Membrane (Chloroplast)

Semi-permeable membrane allowing small molecules to pass.

Intermembrane Space (Chloroplast)

Thin space between outer and inner membranes.

Inner Membrane (Chloroplast)

Regulates transport and synthesizes fatty acids.

Stroma

Protein-rich fluid inside chloroplast containing DNA, enzymes, and ribosomes.

Thylakoid System

Membranous sacs inside chloroplast where light reactions occur. Contains chlorophyll and arranged in stacks called grana.

Granum

Stack of thylakoids; each stack has 10–20 thylakoids.

Astrobiology

The scientific study of life in outer space, including the search for extraterrestrial life.