Unit 4: Cells

The Discovery of the CellCell: the smallest unit that can carry

on all the processes of life.

Because the cell is SO small, we need microscopes to see them.

The Discovery of the Cell

Robert Hooke 1665: EnglishLooked at the corkNamed the small components within the cork

“cells” because they looked like the cell blocks from prison.

He was looking at the cell walls of dead plants.

***Yes, cork comes from a plant!

The Discovery of the CellAnton Van Leeuwenhoek (pronounced “Levin-

hook”) 1700-DutchFirst person to actually observe a living cell!Improved lenses of the microscopesObserved pond water and scrapings of teeth!

The Discovery of the Cell

Matthias Schleiden and Theodore Schwann (German)Schleiden- observed plants and said “all plants are

made of cells”Schwann- observed animals and said “all animals

are made of cells”These two side theories led to part of the cell theory

The Cell Theory1. All living things are made of cells.

2. Cells are the basic structure and function of living things.

3. All cells come from pre-existing cells.

MicroscopesLight Microscope

Light passes through the object or lense to eye or

computer

Magnifies up to 1000x

Bacterium or larger (0.2 micrometers in diameter)

Cannot see the internal cell structure

Useful for living specimen

Electron Microscope

Uses beams of electrons that bounce of

objects to create image

Magnifies up to 1,000,000 x

Reveals details of internal cell structure

Specimen must be dead

SEM: Scanning Electron Microscope

studies the surface structures of objects/cells

TEM: Transmission Electron Microscope

Explores deep internal structures of

objects/cells

Micrograph: photograph taken through

an electron microscope.

Cell StructureOrganelles: internal structures of the cell

Each organelle has a specific function.

Plant and animal cells DO NOT have all the same organelles.

Cell Shape Most cells have a

specific shape

The shape depends on the function

Cell Shape Example:

Cells of the nervous system need to carry information from your brain all the way to your toes.

Therefore, they are long and skinny.

Cell Shape Example:

Blood cells need to travel smoothly through veins and vessels.

Therefore, they are small and round.

2 main classes of CellsProkaryotic Eukaryotic

Lacks a nucleus, but still has most organelles.

Has a nucleus, and has organelles.

DNA is not separate from the cell.

DNA is protected inside the nucleus.

Size: 1 - 10 micrometers Size: 10 – 100 micrometers

Example: Bacterial Cell Example: Plant or Animal Cell

Cell Organization in Multicellular Organisms

CellsThe smallest unit of life capable of carrying out all

functions/characteristic of life.Tissues

A group of cells working together towards the same function.

OrgansSeveral types of tissues functioning together for a

specific purpose.Organ System

Several organs working together to perform a function to help the organism carry out all other functions.

OrganismAll the organ systems working together to create one

being.

Tissues of Plants

Dermal TissueForms the outer layer of the plant

Ground TissueMakes up the bulk of the roots and stems

Vascular TissueTransports water and food throughout the

plant

Organs of Plants

Roots StemsLeavesFlowers