1. Chapter 4 – A Tour of the Cell
And comparison to viruses

2. Intro

3. Intro

4. Intro

5. Intro

6. Intro

7. State Standards
Standard 1.c. – Prokaryotic cells, eukaryotic cells (including those from plant and animals), and viruses differ in complexity and general structure
Standard 1.e. – The endoplasmic reticulum and Golgi apparatus play a role in the secretion of proteins

8. The Microscopic World of Cells
Organisms are either:
Single-celled, such as most bacteria and protists
Multicelled, such as plants, animals, and most fungi

9. The Microscopic World of Cells
The human body is made up of trillions of cells many of which are specialized
Muscle cells, Nerve cells, & blood cells…

10. The Cell Theory Cells were first discovered in 1665 by Robert Hooke.
The accumulation of scientific evidence led to the cell theory
- All living things are composed of one or more cells
- All cells are formed from previously existing cells

11. Microscopes provide windows to the world of the cell
The Light Microscope
Light passes through the specimen
Lenses enlarge, or magnify, the image
Magnification – the increase in the specimen’s apparent size
Resolving power – the ability to show 2 objects as being separate

12. Microscopes provide windows to the world of the cell
The Electron Microscope
Uses a beam of electrons
Resolving power is higher than the light microscope
Can magnify up to 100,000X

13. Microscopes provide windows to the world of the cell
Scanning Electron Microscope (SEM)
Used to study the details of the surface of the cell
Produces a 3D image
Used to study cell and organelle surfaces

14. Microscopes provide windows to the world of the cell
Transmission Electron Microscope (TEM)
An electron beam is aimed through a thin section
Used to explore the internal structures of the cell

15. The Two Major Categories of Cells

16. The Two Major Categories of Cells
There are 2 major categories of cells
- Prokaryotic cells
- Eukaryotic cells
Both cells
- Are surrounded by a plasma membrane
- Consist of cytoplasm and organelles and contain DNA
Prokaryotic and eukaryotic cells differ in several ways

17. The Size of Cells Most cells are 10-100 micrometers in size
Cell size and shape are related to their function
Ex: red blood cells, nerve cells, eggs

18. The Size of Cells
The lower limit of cell size is determined by the fact that a cell must be large enough to house the parts (DNA, organelles) it needs to survive and reproduce.
The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes.

19. Prokaryotic Cells Smaller than eukaryotic cells (2-8 um)
Enclosed by a plasma membrane that is usually surrounded by a rigid cell wall
The cell wall may be covered by a sticky capsule
DNA is found inside the cell but it is not housed in a nucleus
Ribosomes (70S) are present
Internal structures surrounded by membranes are not present

20. Structures of the Prokaryotic Cell
Nucleoid region – area where DNA is coiled in the cytoplasm. DNA is in direct contact with the rest of the cell
Plasmid – smaller circular DNA molecules
Ribosomes – where proteins are made
Plasma membrane – encloses the cytoplasm of the prokaryotic cell

21. Structures of the Prokaryotic Cell
Cell wall – rigid, composed of lipids, carbohydrates and protein. Protects the cell and maintains its shape
Cell Wall components determine if bacteria is classified as
gram positive (+)
or gram negative (-)..In general more toxic and resistant to antibiotics

22. Structures of the Prokaryotic Cell
Capsule – sticky outer coat that surrounds some prokaryotes. Protects the cell surface. Helps bacteria attach to surfaces
Pili – short surface projections found in some prokaryotes. Helps attach bacteria to surfaces
Flagella – long whiplike extensions found in some prokaryotes. Propel cell through liquid environments

23. The Role of Bacteria in the Nitrogen Cycle

24. Eukaryotic Cells Larger than prokaryotic cells (10-100 um)
More complex in structure
DNA housed in the nucleus
Ribosomes (80S)
Membrane bound organelles

25. Comparing Animal and Plant Cells
Animal cells contain centrioles, lysosomes, flagella
Plant cells contain a central vacuole, cell wall, chloroplasts

26. Comparing Eukaryotic and Prokaryotic Cells-
Prokaryotes
Eukaryotes
Differences
Commonalities

27. Comparing Eukaryotic and Prokaryotic Cells- Differences in parallel statements
Date back at least 3.5 BYA
Ex include: Bacteria & Archaeabacteria
Simpler Structure (all single celled organisms)
Naked DNA (not wrapped around histone proteins)
Circular Chromosomes
DNA in cytoplasm (nucleoid region)
70S ribosomes
No internal membrane compartments (no membrane bound organelles)-ex: no mitochondria, no Rough ER
Eukaryotic Cells
Descended from ancient prokaryotes 2.1 BYA
Ex organisms: plants, animals, fungi, protists
More Complex Structure (mostly multicellular organisms but some single celled organism)
DNA associated with histone proteins
Chromosomes linear
DNA separated from cytoplasm (in nucleus)
80S ribosomes
Internal membrane compartments (membrane bound organelles) –ex: yup mitochondria and Rough ER

28. Comparing Eukaryotic and Prokaryotic Cells-
Commonalities: Prokaryotes & Eukaryotes
Smallest units of Life (therefore has the characteristics of life Chapter 1!)
Requires energy (to run metabolic reactions of life)
Grows and develops
Independently reproduce
DNA stores genetic information
Can evolve over generations
Order: internal organization
Responds to environmental stimuli
Ribosomes build proteins for the cells
Contains plasma membrane to regulate what enters and leaves the cell
Filled with cytosol (fluid)