The Ultrastructure of Cells (1.2)
IB Diploma Biology
1.2.4 Electron microscopes have a much higher resolution than light microscopes.
• Resolution: making separate parts of
an object distinguishable by the eye
• Beams of electrons have shorter
wavelengths than visible light; so
much higher resolution
Eye
Light
micro.
Electron
micro.
mm
0.1
Resolution
µm
nm
100
100,000
0.0002
0.2
200
0.000001
0.001
1
1.2.1 Prokaryotes have a simple cell structure without compartments
Prokaryotes
“Before nucleus:” evolutionary precursors to eukaryotes.
Escherichia coli (E. coli) http://en.wikipedia.org/wiki/Escherichia_coli
1.2.1 Prokaryotes have a simple cell structure without compartments
Prokaryotic Cell Parts
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:
http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.swf
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: https://store.ibo.org/biology
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: https://store.ibo.org/biology
1.2.3 Prokaryotes divide by binary fission.
PROKARYOTES
E
P
R
O
D
U
C
E
through
binary
fission
two-parts splitting
PROKARYOTES
binary
fission
E through
P
R
O
The closed-loop DNA of the
bacterium makes copies through
D semi-conservative DNA replication.
U
New plasmids are pulled to
opposing poles by fibers.
C
E
The bacterium divides in two.
http://www.youtube.com/watch?v=gEwzDydciWc
1.2.7 Draw the ultrastructure of prokaryotic cells based on electron micrographs.
So after absorbing all of that information, all you have
to do is put it in the diagram!
Annotate: to add brief notes
to a diagram or graph.
1.2.2 Eukaryotes have a compartmentalized cell structure.
1.2.8 Draw the ultrastructure of eukaryotic cells based on electron micrographs.
The Cell membrane is the boundary of the cell.
• It acts as a “gatekeeper”, preventing the entry or exit of
some molecules and facilitating the movement of others.
• It is a phospholipid bilayer
• It is permeable to oxygen and carbon dioxide
• It is impermeable to water and charged particles, they
must enter through special proteins embedded in the
membrane
More in 2.4
http://commons.wikimedia.org/wiki/File:Cell_membrane_detailed_diagram_en.svg
The Nucleus contains
the chromosomes which
comprise most of the
DNA in a cell
- It is the largest
organelle
- It has a double layer
membrane
- mRNA, transcribed
from DNA in nucleus,
exits through pores
- Some cells have
multiple nuclei
Rough Endoplasmic Reticulum
Spot the
difference?
Smooth Endoplasmic Reticulum
http://images.wellcome.ac.uk/
The ‘spots’ are the
difference!
The Rough
Endoplasmic Reticulum
is peppered with
ribosomes that give it
the rough appearance
Proteins synthesized
here are secreted
Smooth ER is site of lipid
production
I shall name it………
The internal reticular apparatus!!
Pretty catchy… no?*
Camillo
Golgi
*Everybody thought that was a
terrible name, so they called it the
Golgi apparatus instead
http://commons.wikimedia.org/wiki/File:C_Golgi.jpg
http://commons.wikimedia.org/wiki/File:Golgi_in_the_cytoplasm_of_a_macrophage_in_the_alveolus_(lung)_-
The Golgi Apparatus is a
flattened stack of membranes
responsible for the packaging
and delivery of proteins
Lysosomes are simple, membrane-bound organelles full of
enzymes that digest engulfed bacteria and viruses and
large molecules for recycling.
The Mitochondrion (pl. Mitochondria)
• The ‘power house’ of the cell
• Has a smooth outer membrane and a
folded inner membrane
• Where aerobic respiration occurs
Mitochondria in mammalian lung cells
Free Ribosomes:
• 80s sized in
eukaryotes (v. 70s
size in prokaryotes)
• Proteins
synthesized for
use within the cell
(i.e. enzymes used
in the cytoplasm)
Chloroplasts
• Site of Photosynthesis in Plant Cells
• Stacks of Thylakoids
Vacuoles & Vesicles:
•
•
•
•
Animal cells sometimes have small vacuoles for digestion
Unicellular organisms have contractile vacuoles for expelling water
Plant cells have large vacuoles that hold water and food
Vesicles are small lipid sacs used for transport
Centrioles & Microtubules:
• Centrioles are bundles of
microtubules found in Animal Cells
• Microtubules separate
chromosomes in cell division and
make-up cilia and flagella
1.2.8 Draw the ultrastructure of eukaryotic cells based on electron micrographs.
State: Give a specific name, value or other brief answer without
explanation or calculation.
Animals
Plants
Have a cell wall
Don’t have a cell wall
Have chloroplasts in photosynthetic cells
Don’t have chloroplasts anywhere
Carbohydrate stored as starch and plant
oils
V. Carbohydrate stored as glycogen and
animal fat
Rigid Shape (due to cell wall)
Flexible shape
Have a large permanent storage vacuole
May have small, temporary vacuoles
Compare: Give an account of similarities and differences between
two (or more) items, referring to both (all) of them throughout
Prokaryotic
Eukaryotic
Small cells
Relatively larger cells
Always unicellular
Some multicellular, some unicellular
No nucleus: DNA a ‘naked’ loop in
the nucleoid region
DNA in chromosomes in a
membrane-bound nucleus
Ribosomes smaller (70s)
Ribosomes larger (80s)
No mitochondria, respiration in cell
membrane and mesosomes
Mitochondria, where aerobic
respiration occurs
Cell division by binary fission
Cell division by Meiosis or Mitosis
Reproduction asexual (some gene
exchange can occur via conjugation)
Reproduction Sexual or asexual
1.2.5 The structure and function of organelles within the exocrine gland cells of the
pancreas.
Exocrine gland cells of the Pancreas secrete digestive
enzymes into small intestine
• Enzymes are
proteins, so these
cells must produce
proteins in large
quantities
• Organelles involved:
•
•
•
•
Rough ER
Vesicles
Golgi Apparatus
Plasma membrane
1.2.6 The structure and function of organelles within palisade mesophyll cells of the leaf.
Palisade mesophyll cells carry out most of the
photosynthesis in plant cells
• Organelles involved:
• Chloroplasts
• Mitochondria
• Large Vacuole
1.2.9 Interpret electron micrographs to identify organelles and deduce the function of
specialized cells.
Identify the labeled structures in this liver cell TEM image.
Source: http://www.udel.edu/biology/Wags/histopage/empage/empage.htm
What can you
see?