1. Prokaryotes Objective 1.2 Ultrastructure of cells
Image: Hospital-associated MRSA by NIAID on Flickr

2. Prokaryotes “Before nucleus:” evolutionary precursors to eukaryotes.
Escherichia coli (E. coli)

3. Prokaryotic Cell Parts
mesosome
cell wall
plasma membrane
pili
cytoplasm
nucleoid
ribosomes
flagella
Prokaryotic cell parts are not generally membrane-bound, so we don’t refer to them as organelles.
Cell structures animation:

4. Prokaryotic Cell Parts
mesosome
cell wall: protective protein-based coating (Gram + / Gram -)
plasma membrane: selectively permeable, controls entry & exit of materials to and from the cell.
pili: attach to other bacteria for DNA transfer
cytoplasm: contains enzymes for metabolic reactions
nucleoid: closed-loop of bacterial DNA in a condensed area
ribosomes: protein synthesis (transcription & translation)
flagella: whiplash-like motion causes movement
Cell structures animation:

5. Prokaryotic Cell Parts
mesosomes
These don’t really exist naturally as bacterial cell parts, and could be an example of a paradigm shift in thinking.
They were observed in some electron micrographs and thought to be in-folds of membrane used for division, respiration or making cell walls…
… turns out they are an
artifact of the
preparation method
for some electron
microscope images.
Cell structures animation:

6. Past-paper question: E. coli TEM image
Identify these structures: I.
II.
III.
IV.
Calculate the magnification of the image.
Image from IB Biology QuestionBank CDRom – get a copy here:

7. Past-paper question: E. coli TEM image
Identify these structures:
I. Plasma membrane
II. Cell wall / pili
III. Nucleoid
IV. Cytoplasm / ribosomes
Calculate the magnification of the image. 1. Measure the scale bar in mm.
2. Multiply x 1000 to convert to μm.
That is the magnification.
How long is the bacterium?
Image from IB Biology QuestionBank CDRom – get a copy here:

8. PROKARYOTES E P R O D U C
through
binary fission
two-parts
splitting

9. binary fission PROKARYOTES E through P R O D U C
The closed-loop DNA of the bacterium makes copies through semi-conservative DNA replication.
New plasmids are pulled to opposing poles by the spindle fibres.
The bacterium divides in two.

12. What about conjugation?

16. Eukaryotes Life with a nucleus
Image: Hela Cell nuclei via

20. Eukaryotic vs. Prokaryotic Cells
Eukaryotic Cells
DNA in ring form without protein
DNA with proteins: chromosomes/chromatin
DNA free in cytoplasm (nucleoid region)
DNA enclosed within a nuclear envelope (nucleus)
No mitochondria
Mitochondria
70s ribosomes
80s ribosomes
No membrane bound organelles
Membrane bound organelles

21. Animal
Cells

24. Page 24 in your textbook

25. EUKARYOTIC CELLS

26. NUCLEUS

27. Nucleus Structure: Double membrane, continuous with ER
Contains DNA and proteins
DNA wound around proteins organized into chromosomes
Perforated by pores
Nucleolus inside
Function:
DNA is code for proteins, genetic information
Nucleolus made up of ribosomal RNA, which makes up the ribosomes where protein synthesis happens
Pores allow mRNA and rRNA to leave nucleus

28. RIBOSOMES

29. Ribosomes Structure: Made of rRNA and protein Small and large subunits
Some are attached to endomembranous system, some are free
Function
Site of protein synthesis
Proteins made on bound ribosomes are secreted outside the cell
Proteins made on free ribosomes are used inside the cell.

30. ENDOMEMBRANE SYSTEM
Endoplasmic reticulum

31. Endoplasmic Reticulum
Smooth ER has no ribosomes, has enzymes embedded in the membrane
Rough ER has ribosomes
Smooth ER: synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons.
Stores Ca++ in muscle cells
Rough ER: synthesis of proteins and glycoproteins
Makes membrane proteins and phospholipids that makes up its own membrane

32. Golgi Apparatus

33. Golgi apparatus Function: Structure:
Flattened, membranous sacs called cisterns
Function:
Proteins and phospholipids are modified
Products leave in vesicles, these can go to other places in the cell or to the membrane for secretion.
Products are tagged chemically so they go to the correct places

34. Lysosome

35. lysosome Structure: Membranous sac with digestive enzymes
Only in animal cells
Functions:
Intracellular digestion of macromolecules
Recycling of damaged organelles called autophagy

36. Mitochondria Structure: more detail when we learn about respiration
Function: cellular respiration
Why I am obsessed with my mitochondrial function

37. Vacuoles Similar to lysosomes, have hydrolytic enzymes
Present in plant and fungi, protista
Functions:
Food vacuoles store food
Contractile vacuoles in protists control water and salts
Plants have central vacuole that gives internal support, stores organic molecules, pigments, poisons

41. chloroplast Structure: more detail when we learn about photosynthesis
Function - Photosynthesis

42. Page 24 in your textbook

43. Animal Cell vs. Plant Cell
Feature
Animal
Plant
Cell wall
Not present
Present- composed of cellulose
Carbohydrate storage
Glycogen
Starch
Chloroplast
Present in plant cells that photosynthesize
Vacuole
Small if present at all
Large, fluid filled vacuoles
Centrioles
Centrioles within a small centrosome area
No centrioles

46. Grab a whiteboard…quick quiz :)
A cell has cytoplasm, a cell wall, naked DNA and ribosomes. Based on this information, what type of cell could this be? A. A cell from a pine tree B. A grasshopper cell C. A human red blood cell D. A bacterium
Prokaryotic cells lack a true
a) ribosome
b) mesosome
c) cytoplasm
d) nucleus

47. Quick quiz….

49. Identify the labeled structures in this liver cell TEM image.
Calculate:
The magnification of the image
The maximum diameter of the nucleus
Source:

50. Identify the labeled structures in this liver cell TEM image.
golgi apparatus
plasma membrane
ribosome
vesicles
rough er
nucleus
Scale bar measures 33mm
Actual = Measured/magnification
Mag = 16,500x
Diameter measures 85mm
Actual = 5.15 µm
Calculate:
The magnification of the image
The maximum diameter of the nucleus
Source:

51. What you’ll see under your microscope
Today’s :ab
This is what your drawings should look like!