1. Biology A Tour of the Cell

2. Microscopy A cell is the smallest unit of life.
They can vary in size, shape and function (structure determines function).
The light microscope led the way to knowledge of the cell.

3. You will work with a light microscope in the lab.
Microscopes:
A light microscope magnifies objects (specimens) ~1000x their size. Most cellular structures CANNOT be seen.
You will work with a light microscope in the lab.

4. Electron microscopes give more detail and magnify a million times the object’s size.
However, the organism dies when using an electron microscope.
There are 2 types of electron microscopes:
A scanning electron microscope (SEM) gives a 3D image of a specimen/object.
A transmission electron microscope (TEM) transmits electrons to view the interior of an object.

5. SEM How the Scanning Electron Microscope works:

6. TEM
How the Transmission Electron Microscope works:

7. TEM
SEM

8. A history lesson:
Robert Hooke (1665) named the cell after looking at cork under the microscope.

9. Anton van Leeuwenhoek (LAY-von-hohk) (1670’s) developed a simple light microscope & discovered unicellular organisms and called them “little beasties”.
Rudolf Virchow (1855) stated that all cells came from pre-existing cells (a.k.a. Cell Theory).

10. The Cell Theory (Virchow) has 3 basic principles:
Cells are the basic units of life.
All organisms are made of 1 or more cells.
All cells arise from existing cells.

11. Cell Structures:
All cells have an enclosure called a cell, or plasma membrane.
This functions as the gate keeper and controls what enters and exits the cell.
It is mainly composed of phospholipids and proteins.

12. Within the cell is the cytoplasm
Within the cell is the cytoplasm. This is a semifluid substance that contains the organelles.
The organelles are small structures that have specific functions within the cells.

13. The cytoskeleton is a protein network within the cytoplasm that helps support the cell and helps the cell maintain or change its shape. It also
Anchors organelles
Enables the cell to move
Allows materials to move throughout the cell
Composed of microtubules & microfilaments

14. The nucleus is the control center of the cell
The nucleus is the control center of the cell
It is surrounded by the nuclear envelope
It contains the chromosomes. There are 46 chromosomes in the human nucleus (in every cell of the human body). The chromosomes are the DNA (genetic material).
The nucleus is only found in eukaryotic cells!

15. The nucleus contains the nucleolus
(if more than 1, nucleoli).
Nucleolus: makes ribosomes
Ribosomes
make proteins.

16. 2 Types of Cells Prokaryotic Cells Bacteria
NO organelles (membrane-bound structures)
Contained w/in cell membrane & cell wall, contain ribosomes, 1 circular chromosome in nucleoid region (NO nucleus) & plasmids (extra pieces of DNA)
Eukaryotic Cells
Protists, Fungi, Plants, & Animals
Contained w/in cell membrane (may have a cell wall)
Contain nucleus & other membrane-bound organelles
Means ‘true kernel’

17. There are 2 types of cells:
Prokaryotes: These are bacteria (in Kingdom Monera).
They are unicellular organisms.
These were the first cells. They are very small cells and are very simple cells.

18. 2. Eukaryotes: found in all other kingdoms except Monera.
These have a nucleus (as well as a cell membrane and the majority of the organelles being discussed, depending on the type of organism).

19. Animal Cell: http://www.animalport.com/img/Animal-Cell.jpg

21. Ribosomes make proteins from amino acids; can be found suspended within the cytoplasm or attached to the endoplasmic reticulum. (not really organelles; these are cellular components)
The endoplasmic reticulum (ER) is a network of membrane that produces materials for the cell. There are 2 types:
The rough ER contains ribosomes and functions in protein synthesis and makes new cell membrane.
The smooth ER makes lipids, process carbohydrates and breaks down toxins.

23. The golgi apparatus is composed of flat membranous save that modify, package and distribute molecules (warehouse of the cell).

24. Vacuoles are membrane-bound organelles that have various functions.
Some store food, water, proteins, ions, or wastes. Generally these are large and centralized.
Lysosomes contain digestive enzymes that break down large molecules and old organelles that the cell no longer needs.

25. Chloroplasts, double-membrane-bound organelles, perform photosynthesis.
This is the process of making sugar (synthesis) in the presence of light (photo).
Plants (some bacteria & protists) make their own food (a.k.a. autotrophic).

26. The mitochondria is the “powerhouse of the cell” b/c it changes stored enter from food into useable chemical energy (ATP) for chemical reactions.
ATP = adenosine triphosphate (energy ‘currency’ of cells)
The chemical reactions are cellular respiration.

27. Cellular Structures
Cilia are short hair-like projections that are in the surface on the cell usually in large number. (NOT organelles)
Beat in unison and aid in the cell’s movement or in the movement of fluid over the cell.

28. Flagella are long tail-like projections that are on the surface of the cell. (NOT organelles)
Usually 1 to 3 of these.
In prokaryotic cells, they spin like propellers.
In eukaryotic cells, they move like whips.

29. Plants differ from animal cells. In plants:
A cell wall surrounds the cell membrane.
The cell wall is a rigid outer covering that protects and maintains the shape of the plant cell.
Fungi, algae (a type of protist) and bacteria also have cell walls but the composition is different.
Cell Wall

30. Plants LACK lysosomes.
Animals are heterotrophic, meaning they must consume food.
Animal cells:
LACK a cell wall but have cytoskeletons for structural support.
LACK chloroplasts
Contain small vacuoles (instead of a large centralized one)
Have lysosomes

31. BOTH Animal and Plant Cells Contain:
Organelles previously mentioned (nucleus, ER, mitochondria, ER, ribosomes, etc)
Cell membranes
DNA (in chromosomes)

32. SEMI-PERMEABLE MEMBRANE
Cell/plasma membrane is composed of a phospholipid bilayer (2 layers of phospholipids) with proteins interspersed.
Phospholipids have a hydrophilic head & hydrophobic tail
Fluid & flexible

33. Cell Membrane

34. Membrane Functions
Cell membranes are semipermeable. This means that some things pass through the membrane while others cannot pass through (this depends on the size & charge of the molecule).
Passive transport is the movement of a substance across a membrane without energy input.
Active transport is the movement of a substance across a membrane with the input of energy.

35. Concentration=[ ].
Molecules move from a higher [ ] gradient to a lower [ ] gradient.
A [ ] gradient is the difference between the [ ] of a particular molecule in 1 area and its [ ] in an adjacent area.
The rate of diffusion depends on temperature and size of molecules involved (molecules move faster at higher temperatures and smaller molecules move faster than larger molecules).
Once molecules are dispersed evenly, equilibrium is reached and diffusion stops.

36. Passive Transport
Diffusion is the movement of molecules from a higher concentration to a lower concentration.

37.
Facilitated diffusion is the diffusion of molecules with the help of a carrier protein embedded within a cell membrane.

38. Osmosis is the diffusion of water.
Diffusion, facilitated diffusion and osmosis are all type of passive transport. These do NOT require energy (occur spontaneously).

39. Active transport in cells usually occurs with the help of carrier proteins but REQUIRE energy. An example is the sodium-potassium pump (Na+/K+ pump).

40. When comparing 2 solutions with a membrane between them, there are 3 types of solutions:
Hypertonic: the fluid outside a cell has a higher [solute] than the cytoplasm inside the cell. In this case, water diffuses out of the cell.
Isotonic: the [solute] outside the cell= the [solute] inside the cell. In this case, no osmosis will occur.
Hypotonic: the fluid outside a cell has a lower [solute] than the cytoplasm inside the cell. In this case, water will move inside the cell.

42. Bulk Transport: 1. Exocytosis: exo=exit; cyto=cell
Wastes and cell products are packaged in vesicles by the golgi apparatus.
The vesicles fuse with the cell membrane and leave the cell

43. 2. Endocytosis: endo=within; cyto=cell
A portion of the cell membrane surrounds a substance outside of the cell & pinches off to form a vesicle
The vesicle moves inward and fuses with other organelles
This includes
Pinocytosis: cell drinking
Phagocytosis: cell eating

45. To review cell structures and reproduction, click on these links and do some activities: