Inside the Cell

Cell cytoskeleton

Overview Prokaryotic vs Eukaryotic Cells Cell organelles Endomembrane system• transport within a cell, molecular “zip

codes” Cytoskeleton• a structural framework• facilitates cell division, movement, and

transport

Key concepts

The structure is related to function Cells are dynamic and integrated

Why are cells small?

4 3

Magnification vs Resolution

Resolution – minimum distance 2 points can be apart and still distinguished as separate

Light Microsco

py Brightfield (unstained) Phase Contrast

Brightfield (stained) Nomarski

Fluorescence Confocal

Grouping of cells Morphology- 2 types:

1. Prokaryotes- lack nucleus2. Eukaryotes, have a nucleus

Phylogeny, or evolutionary history- three domains:1. Bacteria2. Archaea3. Eukarya – eukaryotic

All cells are surrounded by Plasma Membrane

Plasma membrane encloses the cell and separates its contents from its surroundings

Fluid Mosaic - Phospholipid bilayer, proteins

Transport proteins, receptor proteins, and markers

Plasma Membrane

All cells contain DNA and ribosomes

DNA in Prokaryotes – usually circular– Chromosome – in the nucleoid region

– Small, usually circular, extrachromosomal plasmid - contains independent genes; for adapting to new environments

DNA in Eukaryotes –in the membrane-bound nucleus

Ribosomes are the site of protein synthesis

Bacteria: Common Structures

Plasma membrane Stiff cell wall A single chromosome Ribosomes, which synthesize

proteins

Simple interior organization No true nucleus Few, if any compartments

Typical Bacterial Cell

Bacterial cell wall Cell wall contains peptidoglycan Gram-positive – thick, single-

layered cell wall Gram-negative – multilayered

cell wall Cell wall determines shapes,

and susceptibility to antibiotics Polysaccharides cover cell wall for adhering

to surfaces and form aggregates: biofilms

Additional Internal Structures in some prokaryotic cells

Recent discoveries

Internal photosynthetic membranes

Some cytoskeleton of long, thin protein filaments

Some membrane-enclosed organelles

Organelle: a membrane-bound compartment specialized for a particular function, common in eukaryotes

External Structure: Flagella- Aids Bacterial Movement

Tail-like structure, ROTATES to move the cellStructure unique to bacteria (flagellin component)One or more per cell or none depending on the species