Cells and Organelles: Microscopy, Cell Types, and Cytoskeleton

Magnification

Ratio of object's image to actual size

Resolution

Measure of clarity of image

Contrast

Difference in brightness between parts of the sample

Light microscopy

Magnify effectively to about 1000 times, resolution too low to study organelles

Electron microscopes

Study subcellular structures

SEMs

Provides 3D pictures, focuses a beam of electrons onto the surface of a specimen

TEMs

Focuses a beam of electrons through a specimen, used to study internal structure of cells

Prokaryotic

Bacteria and Archaea

Eukaryotic

Protists, fungi, animals, and plants

Plasma membrane

Found in both prokaryotic and eukaryotic cells

Cytosol

Found in both prokaryotic and eukaryotic cells

Chromosomes

Found in both prokaryotic and eukaryotic cells

Cell Size

Surface area to volume ratio

Nucleus

Contains DNA organized into chromosomes

Nuclear envelope

Double membrane that regulates entry and exit of materials

Nucleolus

Site of rRNA synthesis

Ribosomes

Complexes that synthesize proteins

Endoplasmic Reticulum

Highly folded membrane system continuous with nuclear envelope

Rough ER

Secretes glycoproteins and distributes transport vesicles

Smooth ER

Synthesizes lipids and detoxifies drugs and poisons

Golgi Apparatus

Modifies products of ER and sorts materials into transport vesicles

Lysosome

Membranous sac containing hydrolytic enzymes that digests macromolecules

Vacuole

Large vesicle from ER and Golgi

Centrioles

Can transform into basal bodies and contribute to cell mobility

Peroxisome

Specialized metabolic compartments that detoxify harmful substances

Mitochondria

Found in almost all eukaryotic cells, involved in ATP synthesis

Chloroplast

Contains chlorophyll and enzymes that function in photosynthesis

Endomembrane system

Includes nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, plasma membranes

Cytoskeletal Elements

Interacts with dynein motor proteins to produce cell motility

Microtubules

Hollow tubes made of dimers of tubulin

Microfilaments

Solid rods built as twisted double chains of actin subunits

Intermediate filaments

Range in diameter from 8-12 nm, support cell shape

Plasmodesmata

Channels through adjacent cell walls in plant cells

Tight junctions

Membranes of neighboring animal cells pressed together to prevent leakage

Desmosomes

Anchor animal cells together into strong sheets

Gap junctions

Cytoplasmic channels between adjacent animal cells to facilitate communication

Cilia

Short, back-and-forth movement for moving substances along surfaces

Flagella

Whip-like motion for propulsion