1. Cells: The Basic Units of Life
Chapter 4
Cells: The Basic Units of Life

4. Section 1: Organization of Life
Every living thing has at least one cell
Many living things exist as one cell
The average human has 100,000,000,000,000 cells!!!!

5. Cells: Starting Out Small
Most cells are too small to be seen without a microscope
Many organisms exist as single cells, while others exist as multiple cells
All multi-cellular organisms start out as a single cell
For multi-cellular organisms, not all cells look or act the same
i.e. there are 200 different kinds of cells in your body

6. Tissues (cells working together) and Organs (teams working together)
Tissue - a group of cells that work together to perform specific job in the body
Cells grouped together
Organ - two or more tissues working together to perform a specific job
i.e. stomach, intestines, heart, lungs, and skin
Plants also have different organs
i.e. stems, roots, and leaves

7. Organ Systems (a great combination) and Organisms (independent living)
Organ Systems - organs working together in groups to perform a particular job
Each system has its own special job to do
i.e. digestive - breaks down food, nervous - sends electrical impulses “messages” throughout the body
Organisms - anything that can live on its own
There are two types:
1) unicellular - a single cell living on its own
2) multicellular - organisms that can only exist as a group of cells

8. The Big Picture
Organisms can live on their own, but they usually do not live alone
Populations - a group of organisms that are of the same kind and that live in the same area

9. Communities - two or more different populations living in the same area
Ecosystems - the community and all of the nonliving things that affect it
i.e. water, soil, rocks, temperature, etc.

10. Section 2: The Discovery of Cells
Most cells are so tiny that they are not visible with the naked eye
The discovery of cells happened by accident
The first person to see cells was not even looking for them
How did this lead to the discovery of many different cell types?

19. Seeing the First Cells
In 1665, a British chemist named Robert Hooke built a crude compound microscope
He decided to look at a thin piece of cork
To his amazement the cork looked like hundreds of tiny boxes
He named these boxes cells, which means little rooms in Latin
Amazed by his discovery, Hooke used his microscope to look at feathers, fish scales, fly eyes, etc.
Hooke believed that cells were only found in plants

22. Seeing Cells in Other Life-Forms
In 1673, a Dutch merchant named Anton van Leeuwenhoek used his hand made microscope to look at pond scum
He was amazed when he saw many small “creatures” swimming around
He also looked at blood, tartar, and was the first person to see bacteria

25. The Cell Theory
In 1838 German scientist Matthias Schleiden , after many observations, concluded that all plant parts are made of cells
The next year, after many observations, German scientist Theodore Schwann stated that all animal tissues are made of cells
Schwann then wrote the first two steps of what would become the cell theory

26. This completed the Cell theory, which states;
About 20 years later, in 1858, Rudolf Virchow, a German doctor, saw that cells could not develop from anything except other cells
This completed the Cell theory, which states;
1) All organisms are composed of one or more cell
2) The cell is the basic unit of life in all living things
3) All cells come from existing cells

27. Cell Similarities
Cells come in many different shapes and sizes, and perform a variety of different functions
All cells have the following things in common:
1) Cell membrane - a barrier between the inside of the cell and the cell’s environment
2) Hereditary material (DNA) - controls all of the activities of the cell and contains the information for that cell to make new cells

30. Small size - most cells are too small to be seen with the naked eye
Cytoplasm and Organelles - the chemicals and structures that enable the cell to live , grow, and reproduce
Cytoplasm - the gel like fluid of the cell and everything in it
Organelles - the individual structures within the cell
Small size - most cells are too small to be seen with the naked eye

31. Benefits of Being Multicellular
Can you name some of the benefits of being multicellular?

32. Two Types of Cells
Of all the many different kinds of cells that exist, they can only be divided into two groups
1) Prokaryotic - cells that do not have a nucleus or membrane covered organelles
2) Eukaryotic - cells that have a nucleus and membrane covered organelles

35. Prokaryotic Cells The world’s smallest cells and include bacteria
They DO NOT have a nucleus but they do have DNA
They have a single long, circular DNA molecule shape like a rubberband
They DO NOT have membrane covered organelles, but they do have ribosomes
Ribosomes assemble proteins for the cell
Prokaryotic cells (bacteria) were probably the first type of cell on Earth
Some scientists think they have existed for about 3.8 billion years

38. Eukaryotic Cells
All living things that are not prokaryotic cells are made of one or more eukaryotic cells
Have a nucleus and membrane covered organelles
About 10 times larger than prokaryotic cells and more complex
Appeared about two billion years ago
Contains linear shaped DNA molecules
All eukaryotic cells have a cell membrane, and some have an additional cell wall

42. Section 3: Eukaryotic Cells - The Inside Story
Eukaryotic cells are very complex
Everything, from the structures covering the cells to the organelles inside them, performs a task that helps to keep the cell alive

43. Holding It All Together
Cell Membrane
All cells are covered by a cell membrane
It is made of phospholipids
The membranes job is to
1) Keep the cytoplasm inside
2) Allow nutrients in and wastes out
3) Interact with things outside the cell
Cell Wall
Provides strength and support to the cell membrane
It is made of cellulose
Plants and algae have cell walls
Allows plants (i.e. trees) to defy gravity

44. The Cell’s Library Nucleus
The largest and most visible organelle in a eukaryotic cell
Covered by a membrane through which materials can pass
The “control center” of the cell
Stores DNA
DNA contains information on how to make all of the cells proteins
Every chemical reaction important to life involves some kind of protein
Contains the nucleolus
Nucleolus stores materials used to make ribosomes

47. Protein Factories Ribosomes The smallest but most abundant organelles
ALL cells have ribosomes
Ribosomes attach amino acids together to make proteins, because all cells need proteins to live
Amino Acids - the building blocks of proteins
Ribosomes are not covered by a membrane

48. The Cell’s Delivery System
Endoplasmic Reticulum - a membrane covered compartment that makes lipids and other materials for use inside and outside the cell
It also breaks down drugs and other chemicals that could damage the cell
It is an internal delivery system
Substances enter the ER and can move from one place to another through it’s series of tubes
There are two types:
1) Rough ER - has ribosomes attached to it
Proteins made by these ribosomes enter the rough ER
2) Smooth ER

53. The Cell’s Power Plants
Mitochondria
Produces most of the cell’s ATP (Adenosine Triphosphate)
Energy stored in food (glucose) is used to make ATP in the mitochondria
Mitochondria are surrounded by two membranes
The inner membrane has many folds and is where most of the ATP is made
Mitochondria must have oxygen to make ATP
The main reason we breath air is to supply our mitochondria with oxygen
Contains it’s own DNA

57. Chloroplast - “Green Structure”
Produces sugar (glucose) from sunlight during the process of photosynthesis.
This sugar is used by the mitochondria in plants and algae to produce ATP
Chloroplasts are also surrounded by two membranes and contain flatten sacks (thylakoids) stacked upon each other (grana), that contain chlorophyll
Thylakoids contain a green pigment (chlorophyll) that traps sunlight’s energy, which is used to make sugar (glucose)
This process is called photosynthesis
Contains it’s own DNA

61. The Cell’s Storage Centers
Vesicle - any membrane covered compartment used for storage or transport
Vacuoles - membrane covered chamber where water and other liquids are stored
Plants cells have a very large vacuole
Animal cells have vacuoles, but they are too small to be seen
Contractile vacuole - special type of vacuole found in some freshwater unicellular organisms
It allows the organism to “squeeze” excess water out of it’s cell

62. plantvacuolesfigure1.jpg.webloc

64. Packages of Destruction
Lysosomes - special vesicles in animal cells that contain enzymes
Enzymes - a type of protein that allows chemical reactions to occur more quickly
They destroy worn out organelles, get rid of wastes and protect the cell from foreign invaders

65. Plant or Animal Plant Animal Outer boarder - Cell Wall Chloroplasts
Large Central Vacuole
*Lysosomes
*Outside boarder - cell membrane