The Diversity of Cells Diversity of Cells Cell

The Diversity of Cells

Diversity of Cells Cell- smallest unit that can perform all processes necessary for life Robert Hooke- 1 st person to describe cells via a microscope in 1665 Cork – first cells seen

Plant cell vs. Animal cell Have a cell wall Easier to see & differentiate in drawings No cell wall Harder to see & differentiate in drawings Hooke didn't think animals made of cells

Cells in other Organisms Leeuwenhoek- discovered “animalcules” Single-celled pond organisms (protists) Also looked at animal blood & bacteria

Cell theory 1. All organisms are made of one or more cells 2. Cell is basic unit of all living things Schwann wrote 1 st two parts of theory (1839) Had contributions from Schleiden who studied plants 3. All cells come from existing cells Virchow, a doctor, discovered the last part (1858)

Cell size Too small to see w/out microscope (50 human cells in one. ) Large- yolk of bird egg Small- most cells Cells must take in food & get rid of wastes If cells get too large, cell can't take in enough food or get rid of enough wastes (limited by surface area) Surface area to volume ratio = surface area/ volume

Surface Area to Volume Ratio Calculate the surface area to volume ratio of a cube whose sides measure 2 cm. Surface area = # of sides x area of side = 6 x (2 cm x 2 cm) = 24 cm 2 Volume = volume of cube = l x w x h = 2 cm x 2 cm = 8 cm 3 Surface area / volume = 24 cm 2 / 8 cm 3 =3/1

Your Turn • Calculate the surface area-to-volume ratio of a cube whose sides are 3 cm long. Surface area = # of sides x area of side = 6 x (3 cm x 3 cm) = 54 cm 2 Volume = volume of cube = l x w x h = 3 cm x 3 cm = 27 cm 3 Surface area / volume = 54 cm 2 / 27 cm 3 =2/1

Analysis • Which Cube has the greater surface area-tovolume ratio? • The cube with 2 cm sides • What is the relationship between the length of a side & the surface area-to-volume ratio of a cell? – The larger the cell is, the smaller the surface area-to-volume ratio is.

Parts of a Cell • Cell membrane – protective layer that covers the surface & acts as a barrier – Controls what goes in and out of the cell • Cytoplasm- fluid & contents inside the cell – Gel-like fluid in which organelles can float

Parts of a Cell • Organelles – structures that perform specific functions within the cell – Most organelles have membranes • Some float in cytoplasm & are attached to membrane

Parts of Cells • Genetic Material – DNA- deoxyribonucleic acid- genetic material that carries information needed to made new cells & new organisms – Controls activities of cell – Many cells have DNA enclosed inside nucleus

Prokaryotic Cells • Single-celled organisms that have NO nucleus or membrane bound organelles – Most common- bacteria • Smallest cells known • No nucleus, DNA is long & circular • Ribosomes- tiny round organelles made of protein & used to make protein • Strong, weblike exterior cell wall (keeps shape)

Prokaryote cells

Archaea Single-celled prokaryotes with some characteristics similar to bacteria & eukaryotes • Bacteria • No nucleus • No membrane organelles • Circular DNA • Eukaryotes • Ribosomes like eukaryotes

Archaea • Make up of cell membrane & cell walls are unique • Live in places no other organisms live • Extremophile-places where conditions are extreme – Heat-loving- hot springs – Salt-loving- extreme salty water • Methane-making- kind of gas found in swamps

Eukaryotic Cells • Largest cells containing a nucleus & other membrane bound organelles (10 X bacteria) – Organelles- similar to organs that carry out specific functions w/in cell • All living things, except bacteria & archaea are eukaryotes • Many eukaryotes are multicellular – Animals, plants, fungi, amoeba, some algae, yeasts

Eukaryotic Cells