Comprehensive Cell Biology: Structures, Microscopy, and Differences

Cell

The fundamental unit of life because they carry out metabolism, maintain homeostasis, grow, reproduce, respond to the environment, and are the smallest structure capable of life.

Plasma membrane

Phospholipid bilayer that separates inside from outside.

Cytosol

Water-based gel-like fluid.

DNA

Genetic material.

Ribosomes

Build proteins.

Light Microscopy (LM)

Uses light to illuminate specimens with a max magnification of ~1000x; cannot resolve most organelles clearly.

Brightfield Microscopy

Simplest type of light microscopy; low contrast unless stained.

Phase-contrast Microscopy

Good for live, unstained cells.

Fluorescence Microscopy

Labels specific molecules with fluorescent dyes.

Confocal Microscopy

Uses lasers to create sharper 3D images.

Deconvolution Microscopy

Digital image cleaning to improve resolution.

Electron Microscopy (EM)

Uses electron beams for ultra-high resolution.

Transmission Electron Microscopy (TEM)

Provides internal detail, cross-sections, and organelles.

Scanning Electron Microscopy (SEM)

Provides 3D surface details.

Magnification

Image size / actual size.

Resolution

Ability to distinguish two points as separate.

Contrast

Difference in brightness; increased by stains.

Prokaryotes

Domains: Bacteria and Archaea; no membrane-bound organelles, DNA in nucleoid, cell wall of peptidoglycan (bacteria), smaller, higher surface area:volume ratio.

Eukaryotes

Domain: Eukarya (plants, animals, fungi, protists); true nucleus, membrane-bound organelles, larger, more complex, internal membranes compartmentalize functions.

Endomembrane System

This system synthesizes, modifies, packages, and transports proteins and lipids.

Nuclear envelope

The double membrane surrounding the nucleus in eukaryotic cells.

Endoplasmic reticulum (ER)

A network of membranes involved in protein and lipid synthesis.

Golgi apparatus

Flattened sacs that modify, sort, and package proteins into vesicles.

Lysosomes

Organelles that contain digestive enzymes to break down macromolecules.

Vesicles / vacuoles

Membrane-bound sacs that transport and store substances within the cell.

Membrane Flow

The process of vesicle transport between organelles, including secretion to the plasma membrane.

Rough ER

Endoplasmic reticulum studded with ribosomes that synthesizes proteins.

Smooth ER

Endoplasmic reticulum that synthesizes lipids and detoxifies drugs.

Golgi Apparatus Functions

Modifies proteins, adds sugars, sorts, and packages proteins into vesicles.

Lysosomes Functions

Break down old organelles and macromolecules; involved in phagocytosis and autophagy.

Vacuoles

Storage organelles that can be food vacuoles in protists or central vacuoles in plants.

Mitochondria

Organelles that generate ATP through cellular respiration, possessing their own DNA.

Chloroplasts

Organelles in plants and algae that conduct photosynthesis, containing thylakoids.

Peroxisomes

Organelles that perform oxidation reactions and detoxify harmful substances.

Endosymbiont Theory

The theory that mitochondria and chloroplasts originated as free-living prokaryotes.

Cytoskeleton

A network of fibers that provides structural support and facilitates cell movement.

Microfilaments

Smallest cytoskeletal components made of actin, important for muscle contraction and cell shape.

Microtubules

Largest cytoskeletal components made of tubulin, involved in vesicle movement and cell division.

Intermediate Filaments

Medium-sized cytoskeletal components that provide structural support and anchor organelles.

Cilia

Short, numerous projections that move substances across cell surfaces.

Flagella

Long, few projections that move the cell itself.

Plant Cell Wall

A rigid structure made of cellulose that protects and maintains the shape of plant cells.

Animal Extracellular Matrix (ECM)

A network of proteins and carbohydrates that provides structural and biochemical support to surrounding cells.

Intercellular Junctions

Structures that connect adjacent cells, including plasmodesmata in plants and tight junctions in animals.

Plasmodesmata

Channels between plant cell walls that connect the cytoplasm of adjacent cells.