Cell - The Unit of Life

Vocabulary flashcards based on lecture notes about cell biology, cell theory, cell structure, and prokaryotic/eukaryotic cells.

Cell

The minimum, smallest, and fundamental structural unit of all living organisms; capable of independent existence, metabolism, and consciousness.

Unicellular Organism

Organisms like bacteria and protists, capable of performing all essential functions of life independently.

Cell Biology

The study of cells, microentities. Closely related to biology.

Robert Hooke

The scientist who first studied and discovered cells from a thin slice of cork, discovering the cell wall.

Anton Von Leeuwenhoek

The scientist who discovered living cells capable of movement using his designed microscope (e.g., bacteria, protozoans like Amoeba).

Robert Brown

Observed the nucleus (a dense structure) in a cell.

Cell Theory

A theory stating all plants and animals are composed of cells and their products.

Matthias Schleiden

A German botanist (1838) who stated that plant parts are composed of different kinds of cells.

Theodor Schwann

A British zoologist (1839) who stated that animal cells have a thin outer layer (plasma membrane) and plant cells have an additional rigid wall (cell wall). Proposed that organisms are made up of cells and their products.

Rudolf Virchow

Explained that new cells arise from pre-existing cells ('Omnis cellula-e cellula') in 1855 and provided the final shape to the cell theory.

Plasma Membrane

The delimiting structure of animal cells.

Cell Wall

The outermost boundary of plant cells.

Prokaryotes

Cells without a well-defined nucleus, containing only a single molecule of DNA (e.g., bacteria).

Eukaryotes

Cells with a well-defined nucleus (e.g., animal and plant cells).

Organelles

Membrane-bounded structures within eukaryotic cells (e.g., endoplasmic reticulum, plastids, mitochondria, Golgi body, lysosomes).

Ribosomes

Non-membrane-bound organelles found in all cells, including mitochondria, plastids, and endoplasmic reticulum.

Cytoplasm

The semi-fluid matrix of the cell; the main arena of cellular activities.

Centrioles/Centrosomes

Found in animal cells, fungi, and some algae, but absent in higher plants.

Protoplasm

Includes the nucleus and cytoplasm within a cell.

Cell Envelope

Includes the cell wall and plasma membrane.

Double Membranous Organelles

Organelles bound by two membranes, such as plastids, mitochondria, and the nucleus.

Single Membranous Organelles

Organelles bound by a single membrane, such as the endoplasmic reticulum, Golgi body, lysosomes, vacuoles, and microbodies.

Non-Membrane Organelles

Organelles lacking a membrane, such as ribosomes and centrioles.

Mycoplasma/PPLO

The smallest cell, approximately 0.3 μm in length.

Prokaryotic Cells

Include bacteria, cyanobacteria, mycoplasma, and BGA; show faster rates of division and variation in shape (bacillus, coccus, spiral, vibrio).

Glycocalyx

The outermost layer of the bacterial cell envelope; its chemical composition and thickness vary in different bacteria.

Slime Layer

A thin and loose layer of glycocalyx that prevents water and nutrient loss.

Capsule

A thick and tough layer of glycocalyx that hides the bacterium from the host's immune system.

Peptidoglycans/Murein/Mucopeptides

The chemical composition of the bacterial cell wall; provides strong structural support and prevents collapsing and twisting.

Gram-positive Bacteria

Bacteria that retain crystal violet stain and appear purple; have a thicker cell wall with more peptidoglycan and are less easily destained.

Gram-negative Bacteria

Bacteria that can be destained by acetone or ethyl alcohol and have a thinner cell wall with two plasma membranes; mostly pathogenic.

Mesosome

Non-membranous extensions of the plasma membrane into the cell in bacteria; involved in cell wall formation, DNA replication, secretion, and aerobic respiration, analogous to mitochondria.

Chromatophores

Membranous extensions into the cell found in photosynthetic bacteria; contain chlorophyll pigments and are involved in photosynthesis.

Flagellum

A filamentous outgrowth from the cell wall in bacteria, composed of a basal body, hook, and filament; involved in motility.

Fimbrae

Short bristle-like surface extensions found in some bacteria, made up of fimbrin protein; help bacteria attach to surfaces.

Pili (singular: Pilus)

Elongated, hollow, and tubular surface extensions in bacteria, made of pilin protein; provide passage for DNA transfer from one bacterium to another.

Plasmid

Circular DNA present in many bacteria, providing unique phenotypic characteristics such as antibiotic resistance.

Inclusion Bodies

Reserved materials stored in the cytoplasm of bacteria, not bounded by any membrane (e.g., phosphate granules, glycogen granules).

Eukaryotic Cells

Include plant, animal, fungus, and protist cells; show extensive compartmentalization with membrane-bound organelles.

Plasma Membrane/Cell Membrane/Plasma Lemma

Composed mainly of lipids and proteins; lipids are mainly phospholipids arranged in a bilayer with polar heads towards the outer sides and non-polar tails towards the inner part.

Amphipathic Molecule

A molecule with both hydrophobic and hydrophilic regions (e.g., phospholipids).

Peripheral Proteins

Proteins located on the outside of the plasma membrane, easily extracted, and hydrophilic.

Integral Proteins

Proteins located partially or totally buried in the membrane, difficult to extract, and hydrophobic or amphipathic.

Fluid Mosaic Model

Model of the cell membrane proposed by Singer and Nicolson in 1972, illustrating the quasi-fluid nature of lipids enabling lateral movement of lipids and proteins within the bilayer.

Passive Transport

Movement of molecules along the concentration gradient without any requirement of energy (e.g., simple diffusion, osmosis, facilitated diffusion).

Active Transport

Movement of molecules against the concentration gradient, requiring specific proteins (pumps) and energy (e.g., Na+/K+ pump).

Cell Wall

Provides definite shape, structural support, protects the cell, aids in cell-cell interactions.

Tonoplast

The membrane of the plant cell vacuole.

Mitochondria

Double-membrane-bound organelles responsible for aerobic respiration and ATP synthesis; contain their own DNA and ribosomes.

Plastids

Double-membrane-bound organelles in plant cells; come in different types based on pigmentation: chloroplasts (green), chromoplasts (colored), and leucoplasts (colorless).

Ribosomes

Dense granules involved in protein synthesis; exist as 70S in prokaryotes and 80S in eukaryotes, composed of rRNA and proteins.

Cytoskeleton

A filamentous, proteinaceous network providing mechanical support, shape maintenance, and motility in eukaryotic cells; includes microtubules, microfilaments, and intermediate filaments.

Cilia and Flagella

Hair-like outgrowths of the cell membrane; involved in cell movement and ingestion.

Centrosome

Aids the formation of microtubules within the animal cell.

Nucleus

First discovered by Robert Brown in 1831. Contains chromatin.

Nuclear Envelope

A double-membraned protective covering of the nucleus, perforated with pores, allowing the movement of molecules in and out.

Nuclear Pores

Small openings in the nuclear envelope that allow the passage of molecules between the nucleus and cytoplasm.

Nucleolus

A spherical structure within the nucleus, the site of active ribosomal RNA (rRNA) synthesis.

Chromatin

A network of DNA and proteins within the nucleus; condenses to form chromosomes during cell division.

Histones

Proteins associated with DNA in chromatin; packaging and ordering of DNA.

Endoplasmic Reticulum (ER)

A network of interconnected membranous sacs and tubules in eukaryotic cells; involved in protein and lipid synthesis.

Rough Endoplasmic Reticulum (RER)

ER with ribosomes attached to its surface; involved in protein synthesis and modification.

Smooth Endoplasmic Reticulum (SER)

ER without ribosomes; involved in lipid synthesis

Golgi Apparatus

A series of flattened, disc-shaped sacs or cisternae in eukaryotic cells; involved in packaging, processing, and transporting proteins and lipids.

Lysosomes

Membrane-bound vesicles containing hydrolytic enzymes; function in intracellular digestion.

Vacuoles

A single-membrane-bound sac in plant and animal cells; stores water, nutrients, and waste products; maintains turgor pressure in plant cells.

Microbodies

Small, single-membrane-bound organelles containing various enzymes; involved in oxidation reactions.

Chlorophyll

Green pigment in chloroplasts; captures light energy for photosynthesis.

Grana

Stacks of flattened membranous sacs (thylakoids) inside chloroplasts; site of the light-dependent reactions of photosynthesis.

The fluid-filled space surrounding the grana in chloroplasts; contains enzymes for the light-independent reactions of photosynthesis.

Golgi Apparatus

A series of flattened, disc-shaped sacs or cisternae in eukaryotic cells; involved in packaging, processing, and transporting proteins and lipids.

Lysosomes

Membrane-bound vesicles containing hydrolytic enzymes; function in intracellular digestion.

Vacuoles

A single-membrane-bound sac in plant and animal cells; stores water, nutrients, and waste products; maintains turgor pressure in plant cells.

Microbodies

Small, single-membrane-bound organelles containing various enzymes; involved in oxidation reactions.

Chlorophyll

Green pigment in chloroplasts; captures light energy for photosynthesis.

Grana

Stacks of flattened membranous sacs (thylakoids) inside chloroplasts; site of the light-dependent reactions of photosynthesis.

Stroma

The fluid-filled space surrounding the grana in chloroplasts; contains enzymes for the light-independent reactions of photosynthesis.

Cell

The basic unit of life.

Unicellular Organism

A single-celled organism.

Cell Biology

The study of cells.

Robert Hooke

Discovered cells in cork.

Anton Von Leeuwenhoek

Observed living cells.

Robert Brown

Discovered the nucleus.

Cell Theory

All organisms are made of cells.

Matthias Schleiden

Plants are composed of cells.

Theodor Schwann

Animals are composed of cells.

Rudolf Virchow

Cells arise from pre-existing cells.

Plasma Membrane

The outer boundary of animal cells.

Cell Wall

The outer boundary of plant cells.

Prokaryotes

Cells without a nucleus.

Eukaryotes

Cells with a nucleus.

Organelles

Structures within eukaryotic cells.

Ribosomes

Involved in protein synthesis.

Cytoplasm

The cell's semi-fluid matrix.

Centrioles/Centrosomes

Involved in cell division in animal cells.

Protoplasm

Includes the nucleus and cytoplasm.

Cell Envelope

Includes the cell wall and plasma membrane.

Double Membranous Organelles

Organelles with two membranes.

Single Membranous Organelles

Organelles with one membrane.