Chp 4 – The Cell
Cells- basic unit of structure and function in LIVING things
-organisms made of atoms-molecules-elements-compounds-cells-tissues-organs-organ systems
-organisms can be unicellular (1 celled) or multicellular (many cells)
Discovery of Cell
-began with the invention of the lens and microscope
Light microscope- uses light- magnifies up to 2000 x
TEM – transmission electron microscope- 1000 x stronger than light microscope
SEM – scanning electron microscope- produces a 3-D image
-1655-Robert Hooke- cut a slice of cork (dead plant cells)- saw “empty boxes”- reminded him of the
rooms monks lived in which were called cells- so he named what he saw “cell”
-20 yrs later Anton van Leeuwenhoek, a microscope maker- looked at pond scum and called what he
saw “animalcules – or little animals” – today they we call them protists- one celled organisms
-also was the first to see bacteria
-Father of Microbiology
Cell Theory
Based on the work of 3 scientists:
Schleiden- botanist- studied plants – found out plants were made of cells
Schwann- zoologist-studied animals- found out animals were made of cells
Virchow- doctor- studied diseases- found out that cells came from other cells
Cell Theory States:
1. The cell is the basic unit of structure and function in living things
2. All living things are made of cells
3. Cells come from other cells
Modern Cell Theory - Original Theory + 4 more parts
-The cell contains hereditary information (DNA) which is passed on from cell to cell during cell division.
-All cells are basically the same in chemical composition and metabolic activities.
-All basic chemical & physiological functions (movement, digestion, etc) are carried out inside the cells
-Cell activity depends on the activities of sub-cellular structures within the cell (ex - organelles, nucleus,)
Belief in Spontaneous Generation Theory (Abiogenesis)
There wasn’t an any advancement in the cell theory after Hooke and Leeuwenhoek for nearly 200
Years because people STILL believed in Aristotle’s idea of Spontaneous Generation
Aristotle proposed the theory of Spontaneous Generation
– Also called abiogenesis
– Abiogenesis: the idea that living things can come from non-living matter
– Theory survived 2000 years because that is what people “observed”:
- lots of rain/flooding = creation of frogs
- grain in baskets/bins/clothes = creation of mice
- rotting meat = creation of maggots/flies
Diversity of Cells (Differences between cells)
-not all cells are the same- their structure is based on their FUNCTION
-nerve cells – long- transmit info
white blood cells- change shape to fight invaders,
skin- flat cells like plates for protection
-they come in various shapes, sizes, and organization – though most are spherical or square
-cells are small and can’t be big because of the ratio of the volume & surface area
- the volume grows much faster than the surface area- surface area can’t keep up
-the surface area can’t get enough food or water into the cell or waste out to keep the cell alive
so the cell has to divide and become smaller
Internal Organization
-cells contain organelles: a cell part that performs a specific function for the cell
Organelles → cells
DNA – controls cell
are like
organs → body
Brain – controls body
3 Things found in ALL cells
Cell membrane – membrane that surrounds cell and separates it from its surroundings
DNA – genetic material
Cytoplasm – gel like fluid within the cell
2 Types of cells
Prokaryotic (“before the nucleus”)
-cells that LACK a nucleus (they still have DNA) and organelles with a membrane
-only organelle they have is the ribosome (it lacks a membrane)
- ONLY found in bacteria
Eukaryotic (“true nucleus”)
-cells that HAVE a nucleus and organelles with a membrane
- EVERY organism has eukaryotic cells EXCEPT bacteria
The differences between prokaryotes and eukaryotes is HUGE – so much that there are 2 different
kingdoms just for PROKAROTES
Kingdom Archaebacteria
Kingdom Eubacteria
Kingdom Protista
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia
Prokaryotes (used to be in 1 Kingdom called Monera)
Eukaryotes