1. A Look at Cells
-the smallest unit of life that can carry out all the functions of a living organism
-not discovered until the invention of the microscope

2. UNICELLULAR
Some living organisms are unicellular, only made of only 1 cell; they are the smallest of all living organisms
Ex. bacteria
Many protists

3. Some living organisms are made of many cells-MULTICELLULAR
Ex. Plants, Animals, Fungi

4. Shape is related to Function
Blood Cell-hemocyte; round to move through vessels
Nerve-neuron; long to carry message to spinal cord
Muscle-for contraction and relaxation

5. Types of Cells: Prokaryote vs. Eukaryote
Prokaryotic cells- do not have a nucleus or other membrane-bound organelles.
cell’s DNA is suspended in the cytoplasm
most prokaryotes are microscopic, single-celled organisms
Bacteria are the ONLY prokaryotes!
Eukaryotic cells – have a nucleus and other membrane bound organelles
cell’s DNA is enclosed in the nucleus
Eukaryotes can be unicellular or multicellular organisms
Animals (including humans), plants, fungi, and protists are ALL eukaryotes!

6. Robert Hooke-1665
Gave the cell its name
Cork from an oak tree

7. Anton van Leeuwenhoek-1670
First “real” microscope
Living organisms in pond water
bacteria
protists

8. Robert Brown—1840 discovered the nucleus of a cell
Observed the epidermal cells of orchids and the anthers of Tradescantia
© Peter v. Sengbusch - Impressum

9. 3 men established The Cell Theory
M. Schleiden 1838, botanist, “all plants are made of cells”
T. Schwann 1839, zoologist, “all animals/organisms are made of cells”
R. Virchow 1855, physician, “all new cells come from other cells” (biogenesis)

10. The Cell Theory Cells are the basic units of all life
All organisms are made of 1 or more cells
All cells come from other cells

11. Found in ALL cells (prokaryote & eukaryote)
Basic Cell Structures
Found in ALL cells (prokaryote & eukaryote)
Cell Membrane-phospholipid and proteins
Cytoplasm-everything inside the cell except the nucleus/DNA
Cytoskeleton-system of fibers
DNA-the genetic material
Ribosomes-proteins are made on these

12. Typical Animal Cell

13. Typical Plant Cell

14. Plant Cell vs Animal Cell
Only in Plants
Only in Animals
Central Vacuole
Chloroplast
Cell Wall
Lysosome*
Centriole*
*scientists are continuing to make new discoveries so this could change.

15. Chloroplasts are found only in plant cells
Chloroplasts are found only in plant cells. They take in light energy and store it in carbohydrates during photosynthesis.
Note the cell wall and large central vacuole in this diagram of a plant cell. They are also found only in plant cells.

16. Centrioles are found only in animal cells
Centrioles are found only in animal cells. They were thought to be involved in cell division.
Lysosomes - contain digestive enzymes for breaking down toxins and worn out organelles, invading cells, or “food” for phages

17. Cell Membrane Function: Homeostasis 1. Controls what enters and leaves
2. Boundary separating the cell from its environment
*Figure p.82

18. Cell Membrane Structure:
1. Thin layer of lipids embedded with proteins
2. Semipermeable (a.k.a. selectively permeable)
3. 2 phospholipid layers called a bilayer
Hydrophilic (H2O loving) head
Hydrophobic (H2O fearing) tail

19. Cell Membrane

20. Cell Wall Cell Wall Location: outside of cell membrane Structure:
Found in plant, algae, fungi and
most bacterial cells
In plants and algae made of cellulose
In fungi made of chitin
In eubacteria made of peptidoglycan
In archaebacteria made of lipids
Function:
- Provides support and protection
- Helps maintain square shape

21. Cytoplasm
Function:
Contains or “suspends” structures called organelles inside the cell
Structure:
Jelly like base, consisting mainly of water and organic compounds called the cytosol
Other structures within the cytoplasm vary
Contains the cytoskeleton

22. Cytoplasm

23. Cytoskeleton
Function-provides support and a place to “anchor” other structures
Structure-composed of protein fibers;
3 types:
actin fibers – contract and expand to give the cell its shape
microtubules – “highway system”; transport information from nucleus to parts of the cell
intermediate fibers – framework for ribosomes/enzymes to be organized for metabolic pathways

24. Cytoplasm showing Cytoskeleton

25. Centrioles Location Animal cells only Structure
9 sets of 3 protein fibers.
Function
Aid in the the division of chromosomes in mitosis.

26. Nucleus Found ONLY in eukaryotes!!! Function:
Control headquarters for the cell (brain)

27. Nucleus Structure: Found in the cytoplasm
Contains the genetic material-chromosomes- made of DNA & proteins
Surrounded by a double membrane-nuclear envelope/membrane
Inside is a nucleolus that makes ribosomes

28. Nucleus

29. Nucleus

30. DNA

31. DNA Structure-complementary strands in a double helix
All cells contain DNA at some point in their life cycle
Structure-complementary strands in a double helix
Function-carries the genetic code
Replicates itself to pass the genetic code on to its daughter cells

32. Organelles—A Closer Look
Nucleolus
Location
Within the nucleus
Structure
knot of chromatin
Function
Produces ribosomes

33. Nuclear Envelope/Nuclear Membrane
Structure- double lipid bilayer. It has small holes called nuclear pores.
Function- encloses genetic material (DNA) in eukaryotic cells and the holes allow mRNA to leave during transcription

34. Ribosomes Structure-spheres composed of RNA and protein
Function-site of protein synthesis
Free ribosomes make proteins that remain inside the cell
Attached ribosomes make proteins that become part of the cell or are exported from the cell

35. These are free ribosomes (in the cytosol)
These are free ribosomes (in the cytosol). Other ribosomes are attached to the ER

36. Ribosomes

37. Ribosomes

38. Endoplasmic Reticulum Rough
Structure:
Network of membranes near nucleus
Contains ribosomes on surface
Function: Transports proteins that were made by the attached ribosomes through the cell to the golgi.

39. Endoplasmic Reticulum Smooth
Structure:
Network of folded membranes throughout cell
Contains no ribosomes on surface
Function:
Makes lipids and breaks down toxic substances.

40. Endoplasmic Reticulum

41. Golgi Apparatus Location In the cytoplasm Structure
Closely stacked, flattened membrane sacs
Function
Stores, packages, and transports products inside for use outside
Vesicles (a bit of the golgi pinches for transport of stored materials).

43. Vesicles Location inside or outside of the plasma/cell membrane
Structure
bits of membrane from the plasma membrane or the golgi apparatus
Function
Vesicles fuse with the cell membrane may be used to release or transport chemicals in or out of the cells.
Exocytosis out of the cell
Endocytosis into the cell

44. Lysosome (not found in plants)
Structure-
Saclike
Contains digestive enzymes
Function-
Digests food particles
Digests old organelles

45. Vacuole Location cytoplasm Structure sac of fluid surrounded by
a membrane
Plants: Large in size
Animals: small in size
Function
Sites of storage of water, ions and some nutrients.
Plants: allows plants to maintain turgor pressure, holds water to prevent wilting.
In plants, this is referred to as the Large Central Vacuole—animal cells do not have these, only small ones.

46. Mitochondria (found in all eukaryotic cells)
Structure-
Oval
Inside is a complex matrix of folded membranes to increase surface area.
Function-
Changes energy stored in food into a more useful form
Energy storing molecule called adenosine triphosphate (ATP is formed)
*skeletal muscle cells, for example, have lots of mitochondria since the cells need lots of energy!

49. Chloroplast. Location Plant cells and some protists Structure
Double phospholipid bilayer. Inner layer
Stacks = grana
Non stacked area = stroma
Function
Capturing radiant energy and converting it to chemical energy.
Chlorophyll is the green pigment that traps the energy from the sun

50. Flagella and Cilia Location outside of cells Structure
Cilia: short hair-like
Flagella long whip-like
Function
Locomotion = movement
Cilia: tiny, flutters of movement.
Flagella: one big wave motion will cause a large amount of movement

51.  Some Cell Web Sites for Further Study 