Key Concepts in Cell Biology and Structure

Cell theory

Cell theory

All organisms are made of cells, the basic unit of life, and cells come from existing cells.

Cell wall

Rigid outer layer that supports and protects plant cells.

Central vacuole

Large storage organelle in plant cells that holds water and helps with growth.

Centrosome

Structure in animal cells that organizes cell division.

Chlorophyll

Green pigment that captures light for photosynthesis.

Chloroplast

Organelle where photosynthesis occurs in plant cells.

Chromatin

DNA and protein material that makes up chromosomes.

Chromosome

Structure made of DNA that carries genetic information.

Cilium

Hair-like structure that moves cells or materials across the cell surface.

Cytoplasm

Jelly-like material inside the cell containing organelles.

Cytoskeleton

Network of fibers that support cell shape and movement.

Cytosol

Gel-like fluid in which organelles are suspended inside the cell.

Desmosome

Structure that links adjacent cells for stability.

Electron microscope

Tool that uses electrons to magnify objects.

Endomembrane system

Group of organelles that work together to process and transport proteins and lipids.

Endoplasmic reticulum (ER)

Network of membranes that produce proteins (RER) and lipids (SER).

Eukaryotic cell

Cell with a nucleus and membrane-bound organelles.

Extracellular matrix

Network of molecules outside animal cells that provide structure and support.

Flagellum

Long, tail-like structure that helps cells move.

Gap junction

Channel between animal cells that allows communication.

Golgi apparatus

Organelle that modifies, sorts, and packages proteins and lipids for transport.

Intermediate filament

Protein fibers that provide cell stability and anchor structures.

Light microscope

Tool that uses light to magnify objects.

Lysosome

Organelle that digests and breaks down cell waste.

Microfilament

Thin fibers that provide cell shape and movement.

Microscope

Tool that magnifies objects.

Microtubule

Thick fibers that support the cell and help with cell division.

Mitochondria

Organelle that produces energy (ATP) through respiration.

Nuclear envelope

Double membrane around the nucleus.

Nucleoid

Region in prokaryotes where the DNA is found.

Nucleolus

Region in the nucleus where ribosomes are made.

Nucleoplasm

Fluid inside the nucleus.

Nucleus

Organelle that contains the cell's DNA.

Organelle

Specialized structure within a cell.

Peroxisome

Organelle that breaks down fatty acids and detoxifies substances.

Plasma membrane

Outer cell membrane that controls what enters and exits the cell.

Plasmodesma

Channels between plant cells that allow material to pass.

Prokaryote

Single-celled organism without a nucleus.

Ribosome

Structure that makes proteins.

Rough endoplasmic reticulum (RER)

ER with ribosomes that produces and modifies proteins.

Smooth endoplasmic reticulum (SER)

ER without ribosomes that makes lipids and detoxifies chemicals.

Tight junction

Seal between animal cells that prevents leakage.

Unified cell theory

Theory that all living things are made of cells.

Vacuole

Storage sac in cells, especially large in plant cells.

Vesicle

Small sac that transports materials within the cell.

Archaea

A domain of single-celled microorganisms that are prokaryotes, distinct from bacteria.

Peptidoglycan

A polymer that forms the cell wall of most bacteria.

Capsule

Outer layer found in some prokaryotes, made of polysaccharides, that helps protect the cell.

Surface area-to-volume ratio

Ratio that limits the size of cells, as larger cells have less surface area relative to their volume, affecting diffusion.

Phospholipid bilayer

Double layer of phospholipids that makes up the plasma membrane.

Cellulose

Primary component of the plant cell wall, providing structural support.

Centrioles

Paired structures in the centrosome of animal cells, involved in cell division.

Myosin

A protein often associated with actin filaments (microfilaments) in cellular movement.

Motor proteins

Proteins that move along microtubules, transporting vesicles through the cell.

Pathogen

A microorganism that can cause disease, which is destroyed by lysosomes.

Phagocytosis

Process by which a cell engulfs particles or pathogens for digestion.

Photosynthesis

Process in plant cells where chloroplasts convert sunlight into energy (sugars).

Cell division

The process by which a cell replicates its DNA and divides into two new cells.

Integral proteins

Proteins embedded in the cell membrane that can span the entire membrane and help transport substances across it.

Peripheral proteins

Proteins attached to the surface of the cell membrane (inside or outside) that assist with signaling or structural support.

Transport proteins

Integral proteins that help move molecules (like ions or nutrients) across the cell membrane.

Channel proteins

A type of transport protein that forms a channel allowing specific substances (like ions) to pass through the membrane.

Carrier proteins

A type of transport protein that binds to a substance, changes shape, and moves it across the membrane.

Receptor proteins

Proteins on the cell membrane that bind to specific molecules (like hormones) and trigger a cellular response.

Glycoproteins

Proteins with attached carbohydrate chains that play a role in cell recognition and signaling.

Anchor proteins

Proteins that attach the cell membrane to the cytoskeleton or to other cells for structural support and stability.

Pinocytosis

Process by which a cell engulfs small particles or liquids ("cell drinking").

Nonpolar (hydrophobic)

Molecules that do not mix with water and repel it ("water-fearing").

Polar (hydrophilic)

Molecules that mix well with water ("water-loving").

Hypotonic

A solution with lower solute concentration compared to another, causing water to enter a cell.

Hypertonic

A solution with higher solute concentration compared to another, causing water to leave a cell.

Isotonic

A solution with equal solute concentration on both sides, causing no net water movement.

Endosymbiosis

Theory that explains how eukaryotic cells evolved from prokaryotic cells by engulfing them and forming a symbiotic relationship.

Ligand

A molecule that binds to a receptor on a cell to initiate a response.

Phosphorylation cascade

A series of chemical reactions where a phosphate group is added to proteins, leading to a cellular response.

Osmoregulation

The process by which cells regulate water and solute concentrations to maintain balance.