Prokaryotic Vs. Eukaryotic Section 4.3

Learning Objectives Compare & contrast the structure of prokaryotic cells & eukaryotic cells Describe the functions of prokaryotic organelles Explain how internal membranes increase efficiency of cell processes & allow eukaryotes to be larger than prokaryotes

2 Types of Cells Prokaryotic cell = cell that lacks a nucleus & membrane-bound organelles Ex. Bacteria & Archaea Eukaryotic cell = cell with a nucleus & membrane-bound organelles Ex. Plant cell & animal cell

Prokaryotes Single-celled organisms Cells have no nucleus or membrane-bound organelles Includes all bacteria & archaea Smallest organisms Live almost everywhere on Earth

Eukaryotes Can be free-living unicellular organisms or multi-cellular organisms Includes all protists, fungi, plants, & animals Cells have a nucleus & membrane-bound organelles Cells are usually larger than prokaryotic cells

Review… Remember that all cells have: Plasma membrane DNA Ribosomes Cytoplasm Cytoskeleton

Structure of Prokaryotic Cells

Have the 5 things found in all cells But the DNA in prokaryotes is usually just one circular chromosome Some cells have a piece of extra DNA called a plasmid Plasmid – extra small circle of DNA that contain a few specific genes Can provide resistance to antibiotics (medicines)

Nucleoid – area of cytoplasm where DNA is found Cell wall – layer surrounding the plasma membrane, reinforces cell shape In bacteria it is made of peptidoglycan In archaea it is made of proteins Capsule – sticky outer coating that helps the cell attach to surfaces Also offers protection from toxins & predators

Flagella – long, tail-like structures used for movement Works like a propeller on a boat Pili, Cilia, & Fimbriae – short protein filaments that help the cell grab & move along surfaces A specific kind (sex pili) help bacteria catch another bacteria & transfer plasmids during “mating”

Oldest Evidence of Life on Earth Are Prokaryotic Biofilms Biofilm = community living arrangement where many individuals live together in a shared mass of slime Can include more than one species Often a type of symbiosis with each species benefiting somehow from the community

Membrane-Bound Organelles Allow For Larger Cells Eukaryotic cells have membrane-bound organelles Prokaryotic cells do not Membranes create separate “rooms” Allows the cells to be more efficient Different reactions can occur simultaneously (at the same time) Allows the cell to grow larger

Membrane-bound organelles have internal environments different from the rest of the cell Optimizes reaction rate Allows cells to store energy One reaction does not affect the entire cell Ex. The enzymes in lysosomes destroy only what is in the organelle with them, not the entire cell