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Cell theory

The idea that all living things are made of cells, cells are the basic units of life, and all cells come from other cells.

Theory (scientific vs. daily use)

In science, a theory is a well-tested explanation. In daily use, it's more like a guess.

Inductive reasoning

Making general rules based on specific observations.

Deductive reasoning

Applying general rules to make specific conclusions.

Microscope

A tool that magnifies small objects so they can be seen in detail.

Ocular lens

The lens you look through on a microscope.

Objective lens

The lens closest to the specimen on a microscope.

Total magnification

The combined power of the ocular and objective lenses.

Wet mount

A slide preparation with water to view living organisms.

Field of view (FOV)

The visible area through a microscope.

Magnification

How much larger an object appears.

Resolution

The clarity or sharpness of an image.

Light microscope

Uses light to view cells and small organisms.

Electron microscope

Uses electrons to see very small structures in high detail.

Fluorescent stain

A dye that glows under special light to highlight parts of cells.

Immunofluorescence

Uses glowing antibodies to label specific cell structures.

Freeze-fracture

A way to break frozen cells to see inside structures.

Cryo-electron microscopy (Cryo-EM)

Views frozen cells in very fine detail using electrons.

Prokaryote

A simple cell with no nucleus, like bacteria.

Eukaryote

A complex cell with a nucleus, like plant or animal cells.

Plasma membrane

A barrier that surrounds the cell and controls what enters and leaves.

Cell wall

A stiff layer outside the cell membrane in plants, fungi, and bacteria.

Cytoplasm

The jelly-like fluid inside the cell where organelles float.

Ribosome (70s and 80s)

Tiny structures that make proteins (70s in prokaryotes, 80s in eukaryotes).

Nucleoid DNA

The region in prokaryotes where DNA is found.

Nucleus

The control center of eukaryotic cells containing DNA.

Mitochondrion

The powerhouse of the cell that makes energy.

Chloroplast

The green organelle in plant cells that does photosynthesis.

Endoplasmic reticulum (rough and smooth)

Rough ER has ribosomes and makes proteins; smooth ER makes fats.

Golgi apparatus

Packages and ships proteins around the cell.

Vesicle

A small bubble that moves materials inside the cell.

Vacuole

A storage space in cells, larger in plant cells.

Lysosome

An organelle with enzymes to break down waste.

Cytoskeleton

A network of fibers that gives the cell shape and support.

Microtubules / Microfilaments

Parts of the cytoskeleton that help with movement and shape.

Cilia / Flagella / Microvilli

Structures for movement (cilia, flagella) or absorption (microvilli).

Naked DNA

DNA not wrapped in proteins, found in prokaryotes.

Atypical cells

Unusual cells like red blood cells (no nucleus), muscle fibers (long and multinucleated), fungal hyphae (many nuclei), and phloem sieve tubes (no nucleus).

Phospholipid bilayer

A double layer of phospholipids that makes up the cell membrane.

Hydrophobic

Water-fearing; repelled by water.

Hydrophilic

Water-loving; attracted to water.

Simple diffusion

Movement of molecules from high to low concentration without energy.

Concentration gradient

Difference in concentration between two areas.

Osmosis

The diffusion of water through a semi-permeable membrane.

Aquaporin

A protein channel in the cell membrane that allows water to pass.

Facilitated diffusion

Movement of molecules through a membrane with the help of a protein.

Channel protein

A protein that forms a tunnel to help substances pass through the membrane.

Gated channel

A channel protein that opens or closes in response to a signal.

Pump protein

A protein that moves substances against the concentration gradient using energy.

Active transport

Movement of substances from low to high concentration using energy.

Selective permeability

Property of a membrane to let some substances pass and block others.

Glycoprotein

A protein with a carbohydrate attached; used in cell recognition.

Glycolipid

A lipid with a carbohydrate attached; used in cell recognition.

Cell recognition

The ability of a cell to identify other cells based on surface molecules.

Cell adhesion

Cells sticking together using proteins on their surfaces.

Fluid mosaic model

Model of the membrane as a fluid structure with proteins floating in it.

Integral protein

A protein that goes through the membrane.

Peripheral protein

A protein attached to the outside or inside of the membrane.

Cholesterol

A lipid in the membrane that helps it stay flexible and stable.

Organelle

A specialized structure within a cell that performs a specific function (e.g., nucleus, mitochondrion).

Single membrane organelle

An organelle surrounded by one membrane, such as the lysosome or endoplasmic reticulum.

Double membrane organelle

An organelle with two membranes, like the mitochondrion or chloroplast.

Solid organelle

An organelle that does not have a surrounding membrane, such as the ribosome or centriole.

Compartmentalization

The division of the cell into different regions (compartments) to separate different cellular processes.

Transcription

The process where DNA is copied into messenger RNA (mRNA).

Translation

The process where mRNA is read by ribosomes to make proteins.

Post-transcriptional modification

Changes made to mRNA after transcription, such as splicing or adding a cap and tail.

Phagocytic vacuole

A membrane-bound compartment formed when a cell engulfs a particle (e.g., bacteria) during phagocytosis.

Lysosome

A single membrane-bound organelle that contains digestive enzymes to break down waste and cellular debris.

Zygote

A single cell formed by the fusion of a sperm and egg; the first cell of a new organism.

Chemical gradient

A difference in the concentration of a substance across a space or membrane.

Gene expression

The process by which information from a gene is used to make a protein.

Stem cell

An unspecialized cell that can divide and become different types of specialized cells.

Stem cell niche

The specific location in the body where stem cells are maintained and controlled.

Totipotent

Can become any cell in the body or the placenta.

Pluripotent

Can become any cell in the body, but not placenta cells.

Multipotent

Can develop into a limited range of cells within a specific tissue type.

Differentiation

The process by which a cell becomes specialized for a specific function.

Surface area to volume ratio (SA:V)

A measure of how much surface area a cell has compared to its volume, affecting the rate of exchange with the environment.

Specialized cells

Cells that have developed specific structures and functions to perform unique tasks.

Neuron

A nerve cell that transmits electrical signals in the body.

Dendrite

Branch-like part that receives signals.

Axon

Long part that carries signals away.

Cell body

Main part of the neuron containing the nucleus.

Membrane potential

The electrical difference across a neuron's membrane.

Resting potential

The stable, negative charge of a neuron at rest.

Sodium-potassium pump

A protein that moves sodium out and potassium into the neuron to maintain resting potential.

Nerve impulse

The electrical signal carried by a neuron.

Action potential

A sudden change in membrane potential that travels down the axon.

Myelinated

Axons with a myelin sheath for faster signal transmission.

Unmyelinated

Axons without a sheath; signals travel more slowly.

Synapse

The gap between neurons where signals are passed.

Synaptic gap

The tiny space between the axon of one neuron and the dendrite of another.

Effector

A muscle or gland that responds to a nerve signal.

Neurotransmitter

A chemical that transmits signals across a synapse.

Depolarization

When a neuron's membrane potential becomes less negative, starting an action potential.

Exocytosis

The process of vesicles releasing substances (like neurotransmitters) out of the cell.

Postsynaptic potential

The change in membrane potential in the receiving neuron.

Ion channel

A protein that allows ions to pass through the membrane.

Acetylcholinesterase

An enzyme that breaks down the neurotransmitter acetylcholine.