1. The Cell
Chapter 4

2. Cells Marks the boundary between the “living and the dead”
Structural and functional unit of an organism
Smallest structure capable of performing all of the functions necessary for life

3. What is a cell? Why do we care? We have TRILLIONS of them!! (@65)
Every organism is composed of one or more cells
Basic unit of structure and
function in organisms
All come from pre-existing cells
Cell Theory

4. Why are Cells so Small????
Large cells have far less surface for each unit of volume than do small cells

5. All cells……. Have an outer plasma membrane Contain DNA
Enclosed within the cell somewhere
Contain cytoplasm

6. Plasma Membrane All cells surrounded by a plasma membrane
Phospholipid bilayer
forms spontaneously whenever a collection of phospholipids is placed in water

7. Cytoplasm material inside a cell is the cytoplasm
Everything between the plasma membrane and the region of DNA
Gives cells their shape
Assist in movement of cell and organelles

8. Microscopes Compound light microscope
Multiple lenses increase magnifying power

9. Two basic kinds of cells
Prokaryotic
Nothing separates the DNA from internal cell parts
Eukaryotic
Contain organelle sacs
Nucleus – contains the DNA

11. Eukaryotic Cells

12. Examples of Eukaryotic Cells:
Animal
Plant
Fungi
Protozoa

13. Organelles Organelles act as their own separate “organs”
They physically isolate chemical reactions inside cells
Animals and plants will differ in their organelles

16. Nucleus Encloses the DNA of a eukaryotic cell Contains chromosomes
Functions:
Prevents DNA from getting entangled with structures in the cytoplasm
Outer membranes act as a boundary

17. Components of the nucleus
Nuclear pores
Nuclear envelope
Nucleolus
Nucleoplasm
DNA
Chromosomes
Chromatin

18. Nuclear envelope
Double-membrane system composed of lipid bilayer (with pores)
Bilayers surround the fluid part of nucleus (nucleoplasm)
Continuous with the endoplasmic reticulum

19. Nucleolus
Dense mass located within the nucleus
Produces ribosomes

20. Ribosomes Site of protein synthesis
Occurs in the cytoplasm
Attached to the endoplasmic reticulum
Differ between prokaryotes and eukaryotes
Why is this important from a health aspect?

21. Endomembrane System Helps modify proteins into final form
Lipids are assembled
Compartmentalizes the cell
Main components:
1. Nuclear envelope
2. Endoplasmic reticulum (ER)
3. Golgi body
4. Various vesicles (transport)

22. 1. Nuclear envelope Merges with the membrane of the ER
Consists of membranous channels and saccules

23. 2. Endoplasmic Reticulum
Channel that snakes through the cytoplasm
Lipids assembled and polypeptide chains modified into final proteins
Can be rough or smooth
Dependant on the attachments of ribosomes
Rough ER
Processing and modification of proteins
Smooth ER
Synthesizes phospholipids

24. 3. Golgi Body (Apparatus)
Series of flattened sacs
Collects, sorts, packages, and distributes materials such as proteins and lipids
Contain enzymes that put the finishing touches on proteins and lipids

25. 4. Vesicles
Enzymes from golgi apparatus sort and package the molecules into vesicles
Tiny sac that moves through cytoplasm
Function in transport, storage, or digestion of substances
Two main types:
Lysosomes
Peroxisomes

26. Lysosome A lysosome is a membrane-enclosed sac
contains digestive enzymes to break down:
Macromolecules
damaged organelles

27. Put it all together……

28. Organelles That Contain DNA
Eukaryotic cells contain cell-like organelles that, besides the nucleus, also contain DNA
these organelles appear to have been derived from ancient bacteria that were then assimilated by the eukaryotic cell
they include the following organelles:
Mitochondria
Chloroplasts

29. Energy-Related Organelles
organelles specialize in converting energy to a form that can be used by the cell
Requires solar energy
Dissipates as heat
Chloroplasts
Use solar energy to synthesize carbohydrates
Carbohydrates then broken down in the…..
Mitochondria
Produce ATP molecules

30. Energy-Related Organelles
Photosynthesis
Cellular Respiration
The chemical energy of carbohydrates is converted at ATP

31. DNA in mitochondria?? mtDNA Inherited solely from mother
First set of DNA to be sequenced
Endosymbiotic theory
Helps in evolutionary inheritance

32. Organelles That Contain DNA
The theory of “endosymbiosis”
states that some organelles evolved from a symbiosis
one cell of a prokaryotic species was engulfed by and lived inside of a cell of another species of prokaryote

33. Organelles That Contain DNA
Other evidence supporting endosymbiotic theory:
Mitochondria are about the same size as modern bacteria
The cristae in mitochondria resemble folded membranes in modern bacteria
Mitochondrial ribosomes are similar to modern, bacterial ribosomes in size and structure
Mitochondria divide by fission, just like modern bacteria

34. Cytoskeleton – Cytoplasm
System of interconnected fibers, threads, and lattices in the cytosol
Extend from nucleus to the plasma membrane
Gives cells their shape
Assists in movement of cell and organelles
Assemble and disassemble as needed

35. The three protein fibers of the cytoskeleton

36. The Cytoskeleton: Interior Framework of the Cell
Centrioles
complex structures that assemble microtubules in animal cells and the cells of most protists
anchor locomotory structures
such as flagella or cilia

37. The Cytoskeleton: Interior Framework of the Cell
vacuoles
membrane-bound storage centers
central vacuole
filled with water and dissolved substances

38. Outside the Plasma Membrane
Cell walls
found in plants, fungi, and many protists
comprised of different components than prokaryotic cell walls
function in providing protection, maintaining cell shape, and preventing excessive water loss/uptake

39. Outside the Plasma Membrane
Extracellular matrix (ECM)
takes the place of the cell wall in animal cells and is comprised by a mixture of proteins secreted by the cell
collagen and elastin proteins
Form a protective layer over the cell surface
fibronectin protein
Connects the ECM to the plasma membrane
integrins
Connected to fibronectin
Proteins that extend into the cytoplasm of the cell

41. Plant Cells
Cell wall
Central vacuole
Chloroplasts

42. Fungal Cells Mold or yeast Spores Cell wall
Unicellular or multicellular

43. Protozoa Cells
No cell wall
Unicellular
Motility

44. Prokaryotes
Archae
Bacteria

45. “Micro”organisms

46. Characteristics of Cells
Prokaryotic cells
~1.0 µm in diameter
All are microorganisms
Unicellular
Bacteria and Archaea
no nucleus
no membrane-bound organelles

47. Prokaryotes – General cell structure
Nucleoid
Pili
Fimbriae
Flagella
Cell wall
Glycocalyx
Ribosomes