Cell Theory What have we learned about cells over time? What do we currently know about cells?

The 3 Main points of CELL THEORY ALL ORGANISMS ARE COMPOSED OF 1 or MORE CELLS (Schwann, 1839) THE CELL IS THE BASIC UNIT OF LIFE IN ALL LIVING THINGS (Schwann, 1839) ALL CELLS COME FROM EXISTING CELLS (Virchow, 1858)

Who was the first person to see single-celled organism? Anton Von Leuwenhoek – the guy who is credited with inventing the microscope Saw ‘beasties’ (bacteria) under 200x magnification He observed bacteria in pond water- bacteria which couldn’t be seen with the naked eye

Who named cells? Robert Hooke (1665) He observed slices of cork under a microscope and called the box-like structures “cells”

Plant and Animal Cells In 1838, Matthias Schleiden proposed that all plants are made of cells In 1839, Theodor Schwann proposed that all animals are made of cells

All organisms are made of 1 or more cells Sometimes there are organisms made of only 1 cell: single celled organisms; unicellular creatures Prokaryotic cells do not contain a nucleus (ex/ Archaebacteria & Eubacteria) Eukaryotic cells contain a nucleus (ex/ Protozoa (Paramecium), gametes) We and many other creatures are made of more than one cell: multicellular organisms (ex/ Protozoa (Kelp), Fungi, Plants, Animals)

The cell is the basic unit of life in all living things Living things must reproduce (sexually or asexually) Living things contain genetic material (DNA) Living things utilize energy (Metabolism, cell transport) Living things grow and develop (get larger and change as they grow) Living things respond to stimuli (the environment affects the activity of an organism. The organism tries to maintain homeostasis Vocab: Homeostasis: maintaining a stable internal environment

All cells come from existing cells In 1858 Rudolf Virchow observed cellular reproduction (asexual) Theorized that cells all come from other cells Well, how did the first cells come to be? Scientists are still trying to find this out... ENDOSYMBIONT THEORY: mitochondria and chloroplasts descended from ancient prokaryotes, and developed a symbiotic (mutual benifiting) relationship; they “live” inside eukaryotic cells

NOW… How do we define a ‘typical’ cell? Kinda Tough…. There is no typical cell We can group them as prokaryots/eukaryots Uni- or Multi- cellular Plants or Animal Cells Identify Organelles

PROKARYOTES vs EUKARYOTES Fun fact: Karyot = Kernel There are no typical cells, but we divide them into two sub categories. Prokaryotes are mainly bacteria Eukaryotes are mostly higher plants and animals They have many similarities: They contain DNA (genetic material) They have a cell membrane They have ribosomes They have cytoplasm They MAY have flagella or cilia They have mechanisms for creation of ATP (energy) They contain many similar structures and mechanisms

PROKARYOTES vs EUKARYOTES IMAGES Fun fact: Karyot = Kernel

Can be uni- or multi-cellular Have a sticky capsule PROKARYOTES EUKARYOTES Contain no nucleus Have a nucleus Contain no organelles Have organelles Are all unicellular Can be uni- or multi-cellular Have a sticky capsule Covered in a n extracellular matrix outside of the plasma membrane All contain cell walls Have cytoskeletons Were likely the very first cells (2.5 bya) Likely evolved from prokaryotes (~1by after prokaryotes) They can live in a variety of environments May need to have adapted to it’s environment All are bacteria Includes everything which is not bacteria Smaller in size Much larger in size DNA is in a ring formation DNA is in a linear (chromosomal) form Reproduce asexually May reproduce sexually or asexually

Unicellular Organisms Multicellular organism May be prokaryotic or eukaryotic Must be eukaryotic Made of only 1 cell Made of 1 or more cells Can do all functions required for life (reproduce, produce waste… etc) Cells are specialized and work together (skin cells, digestive tract lining cells, etc…) Likely the first type of cell Likely evolved from unicellular