BTEC Level 3 Applied Science: Cell Structure, Function, and Tissues

A comprehensive vocabulary review deck covering cell theory, eukaryotic and prokaryotic organelles, Gram staining, microscopy formulas, cell differentiation, and epithelial/endothelial tissue biology.

Cell

The basic building block and fundamental structural and functional unit of all living organisms.

Organelle

A specialised sub-cellular unit within a cell that performs a specific metabolic or structural function.

Tissue

A group of cells working together to perform a shared function, often sharing a similar structure.

Organ

A body structure made up of groups of different tissues working together to carry out specific physiological functions.

Organ System

A group of organs with related functions working collaboratively to execute major physiological processes in the body.

Differentiation

The process by which an unspecialised cell (such as a stem cell) transforms into a specialised cell type with specific structural and functional adaptations.

Stem Cells

Undifferentiated biological cells that can self-renew via division and differentiate into specialized cell types.

Spontaneous Generation

The historical idea that living organisms could arise spontaneously from non-living matter, such as fly larvae emerging from decaying meat.

Robert Hooke

English scientist who first identified and described cells in 1665 using an early light microscope to observe the honeycomb-like structure of cork.

Anton von Leeuwenhoek

Scientist who developed powerful glass lenses (1674–1683) and became the first person to observe microscopic bacteria and protists in pond water.

Robert Brown

Scottish botanist who in 1831 was the first to observe and describe the nucleus inside a plant cell.

Matthias Schleiden

German botanist who proposed in 1838 that all plant material is composed of cells.

Theodor Schwann

German zoologist who proposed in 1839 that all living organisms are composed of cells.

Jan Evangelista Purkinje

Czech anatomist who observed in 1839 that animal tissues are composed of cells and share structural similarities with plant tissues.

Robert Remak

Physiologist who observed cell division in animal cells in 1852 and 1855, demonstrating that cells arise from pre-existing cells.

Rudolf Virchow

Scientist who published findings in 1855 stating that new cells form from existing ones, supporting and popularizing Remak's work.

Louis Pasteur

French chemist who disproved spontaneous generation in 1860 by demonstrating that bacteria only grow in sterile nutrient broth after exposure to airborne contaminants.

Classical Cell Theory

The biological principle stating that all organisms are composed of one or more cells, the cell is the basic unit of life, and all cells are produced by the division of pre-existing cells.

Modern Cell Theory

The expanded cell theory stating that all cells have similar chemical compositions and metabolic activities, pass hereditary DNA during cell division, and depend on sub-cellular organelles for cell activity.

Eukaryote

An organism composed of cells containing a membrane-bound nucleus enclosing genetic material, as well as membrane-bound specialized organelles.

Prokaryote

A unicellular organism lacking a membrane-bound nucleus and specialized membrane-bound organelles, typically having naked DNA in a nucleoid region.

Plasma Membrane

A phospholipid bilayer separating the cytoplasm from the external environment that provides structural support and regulates molecular transit.

Nucleus

A spherical eukaryotic organelle measuring $10\text{--}20\,\mu\text{m}$ in diameter that acts as the cell's control centre, directing protein synthesis and housing chromosomes.

Nucleolus

The largest sub-structure located inside the nucleus, functioning as the primary site of ribosomal RNA (rRNA) and ribosome subunit synthesis.

Mitochondria

Rod-shaped double-membraned organelles measuring $1\text{--}10\,\mu\text{m}$ in diameter containing cristae and a matrix; site of the Krebs cycle, electron transport chain, and ATP synthesis.

Rough Endoplasmic Reticulum

A series of flattened, membrane-bound sacs studded with ribosomes on its outer surface, responsible for folding, processing, and transporting newly synthesised proteins.

Smooth Endoplasmic Reticulum

A network of membrane-bound tubular sacs lacking ribosomes, involved in lipid synthesis, carbohydrate metabolism, calcium storage, and detoxification.

Golgi Apparatus

A series of flattened, discontinuous membrane-bound cisternae that receives proteins from the endoplasmic reticulum, modifying, sorting, and packaging them into vesicles.

Lysosome

A specialized membrane-bound vesicle containing digestive hydrolytic enzymes used to break down macromolecules, worn-out organelles, and pathogens.

Ribosome

A macromolecular complex (80S in eukaryotes, 70S in prokaryotes) composed of RNA and proteins that carries out polypeptide translation.

Centriole

A cylindrical cellular organelle composed of microtubules that forms the centrosome and organizes the spindle apparatus to separate chromosomes during mitosis.

Cytosol

The gel-like, fluid component of the cytoplasm consisting mainly of water, dissolved ions, soluble proteins, and small molecules.

Cell Wall

A rigid outer protective layer found in plant cells composed of cellulose microfibrils, pectin, and glycoproteins that provides mechanical strength and regulates water passage.

Chloroplast

A biconvex photosynthetic eukaryotic organelle measuring $2\text{--}10\,\mu\text{m}$ across, containing stroma, grana (thylakoid stacks), and chlorophyll to drive photosynthesis.

Tonoplast

The selectively permeable membrane that encloses the large central permanent vacuole in plant cells, regulating ion traffic and maintaining cell turgor pressure.

Amyloplast

A non-pigmented plant leucoplast dedicated to synthesizing and storing starch granules composed of amylose and amylopectin.

Plasmodesmata

Microscopic cytoplasmic channels passing through adjacent plant cell walls that facilitate intercellular transport of water, solutes, RNA, and signalling proteins.

Pits

Thin microscopic depressions in plant secondary cell walls that pair with pits of adjacent cells to permit the passage of water and dissolved minerals.

Peptidoglycan

A mesh-like cross-linked polymer of sugars and amino acids that constitutes the rigid cell wall of bacterial cells.

Pili

Hair-like proteinaceous appendages extending through the cell walls of bacteria that facilitate surface attachment and intercellular conjugation.

Gram-positive Bacteria

Bacteria possessing a thick peptidoglycan cell wall that retains crystal violet stain to appear blue or purple, making them susceptible to cell wall synthesis inhibitors such as penicillin.

Gram-negative Bacteria

Bacteria with a thin layer of peptidoglycan and an outer lipopolysaccharide membrane that stain pink or red with safranin and exhibit elevated resistance to many antibiotics.

Magnification

The degree to which an object is enlarged by an optical instrument, calculated using the formula: $\text{Magnification} = \frac{\text{Image Size}}{\text{Actual Size}}$.

Resolution

The minimum distance by which two distinct points can be separated and still be distinguished as separate individual objects under a microscope.

Photophores

Specialised light-emitting cells found in animals active primarily at night or dwelling deep in the ocean.

Epithelial Tissue

Animal tissue consisting of closely packed cells that covers external body surfaces and lines internal cavities, classified by cell morphology and layer arrangement.

Goblet Cells

Unicellular mucus-secreting epithelial glands scattered along the respiratory and gastrointestinal tracts that lubricate tissues and entrap pathogens.

Endothelium

A single layer of smooth simple squamous epithelial cells lining the internal lumen of blood vessels, lymph vessels, and heart chambers.

Atherosclerosis

A vascular disease initiated by endothelial damage, resulting in the progressive accumulation of fatty plaques within arterial walls, lumen narrowing, and reduced blood flow.

Chronic Obstructive Pulmonary Disease

A progressive inflammatory lung disorder characterized by alveolar destruction, chronic airway inflammation, and excess mucus obstruction, leading to emphysema and chronic bronchitis.