1. Topic 1.2 and 1.3 Review

2. 1.2 Ultrastructure of cells
Essential Idea: Eukaryotes have a much more complex cell structure than prokaryotes
Nature of science: Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)
Understandings
Prokaryotes have a simple cell structure without compartmentalization
Eukaryotes have a compartmentalized cell structure
Electron microscopes have a much higher resolution than light microscopes

3. 1.2 Ultrastructure of cells
Applications and skills
Application: Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll of the leaf
Application: Prokaryotes divide by binary fission
Skill: Drawing of the ultrastructure of prokaryotic cells based on electron micrographs
Skill: Drawing of the ultrastructure of eukaryotic cells based on electron micrographs
Skill: Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells

4. U 1.2.1 Prokaryotes have a simple cell structure without compartmentalization
The first cells most likely to evolve were prokaryotic cells
Prokaryotes are not compartmentalized and simple
A- 70S ribosomes
B- nucleoid region (DNA)
C- plasma membrane
D- cell wall
E- pili
F- flagella
G- cytoplasm C D E B A F G

5. S 1.2.1 Drawing of the ultrastructure of prokaryotic cells based on electron micrographs

6. S 1.2.1 Drawing of the ultrastructure of prokaryotic cells based on electron micrographs

7. A 1.2.2 Prokaryotes divide by binary fission
What is binary fission?
Binary fission is a simple process where the bacteria splits into two identical cells
Benefits?
Quick, easy
Negatives?
They are all genetically the same

8. U 1.2.2 Eukaryotes have a compartmentalized cell structure
What are some differences between eukaryotes and prokaryotes?
Eukaryotic cells contain a nucleus whereas prokaryotic cells lack a true nucleus
Eukaryotic cells have compartmentalization, why is this important?
It allows for enzymes and substrates to be located in areas of optimum pH, temperature, etc.

9. U 1.2.2 Eukaryotes have a compartmentalized cell structureF
A- rough endoplasmic reticulum
B- smooth endoplasmic reticulum
C- lysosomes
D- Golgi apparatus
E- vesicles
F- mitochondria
G- nucleus
H- nuclear membrane
I- nuclear pore
J- 80S ribosomes J
Single membrane A G H I C
Double membrane D B E

10. U 1.2.2 Eukaryotes have a compartmentalized cell structure
Plant cells have:
Chloroplasts
Double membrane
Large vacuole
Single membrane
Cell wall

11. S 1.2.2 Drawing of the ultrastructure of eukaryotic cells based on electron micrographs

12. S 1.1.2 Drawing of the ultrastructure of eukaryotic cells based on electron micrographs

13. S Interpretation of electron micrographs to identify organelles and deduce the function of specialized cells
What do you notice in these micrographs of pancreas cells?
A lot of ER and Golgi
Thus it will be making and shipping lots of proteins
A Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll of the leaf

14. A Structure and function of organelles within exocrine gland cells of the pancreas (last slide) and within palisade mesophyll of the leaf
What do you notice in these micrographs of palisade mesophyll cells?
Chloroplasts
Cell wall
Plasma membrane
Free ribosomes
Nuclear membrane
What does the micrograph tell us about the function of the palisade mesophyll?
Functions in photosynthesis

15. U 1.2.3 Electron microscopes have a much higher resolution than light microscopes
Resolution- ability of a microscope to show two close objects separately in the same image
Electron microscopes emit shorter wavelengths so produce a higher resolution
Light microscope
Electron Microscope
Resolution
0.25 μm
0.25 nm
Magnification
X 500
X 500,000

16. U 1.2.3 Electron microscopes have a much higher resolution than light microscopes
Transmission electron microscopes (TEM)
Use electrons
Non-living specimen (ultra thin sections)
Electrons transmitted through so can see into cells
Scanning electron microscopes (SEM)
Non-living specimen
Electrons not transmitted, surface image produced

17. U 1.2.3 Electron microscopes have a much higher resolution than light microscopes

18. 1.3 Membrane structure
Essential idea: The structure of biological membranes makes them fluid and dynamic.
Nature of science:
Using models as representations of the real world—there are alternative models of membrane structure. (1.11)
Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9)
Understandings
Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules
Membrane proteins are diverse in terms of structure, position in the membrane and function
Cholesterol is a component of animal cell membrane

19. 1.3 Membrane structure Applications and skills
Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutions
Skill: Drawing of the fluid mosaic model
Skill: Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model
Skill: Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model

20. S Analysis of evidence from electron microscopy that led to the proposal of the Davson-Danielli model
Developed by Davson-Danielli in the 1930s
States there was a bilayer of phospholipids in the center and a layer of proteins on the outside
Why did they develop this model?
Chemical analysis showed the membrane was made of proteins and phospholipids
Red blood cells membrane analysis showed there was twice as many phospholipids as membranes- supporting the phospholipid bilayer
Membranes let things in and out

21. S Analysis of the falsification of the Davson-Danielli model that led to the Singer-Nicolson model
Electron micrographs of cell membranes were produces in the 1950s
Showed two dark lines separated by a lighter line
Evidence against Davson-Danielli
Globular proteins located in center of phospholipid bilayer as seen in freeze fracture electron micrographs
Protein analysis showed proteins could extend from one side to the other due to hydrophobicity
Fluorescent-tagged membrane proteins were shown to move within the membrane
This lead to the Singer-Nicolson Model or Fluid Mosaic Model

22. U Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules
Phospholipid structure
Phosphate head- hydrophilic (water loving)
Two fatty acid tails- hydrophobic (water hating)
They are amphipathic
Why do they form a bilayer?
Due to their amphipathic nature when phospholipids are placed in water they form a bilayer with the hydrophobic tails facing away from the water and hydrophilic head facing toward the water- micelle

23. S 1.3.1 Drawing of the fluid mosaic model
Integral proteins
Embedded in the bilayer
Peripheral proteins
Attached to one of the outer surfaces
Glycoproteins
Proteins with a sugar unit attached

24. U 1.3.2 Membrane proteins are diverse in terms of structure, position in the membrane and function
Hormone binding sites
Has a specific shape that binds a hormone, causes a change in shape, allows for a message to be sent to the interior of cell
Ex: Insulin receptor
Enzymatic activity
Can be exterior or interior and catalyze reactions, sometimes working in metabolic pathways
Ex: Cytochrome oxidase
Cell adhesion
Can provide permeant or temporary connections between cells (junctions- tight junctions or gap junctions)
Ex: Cadherin
Cell-to-cell communication
Proteins can have carbohydrates attached that allow for cellular recognition
Ex: Glycoproteins
Passive transport channels
Proteins that span the membrane and allow for movement from high to low concentrations
Ex: Nicotinic acetylcholine receptor (receptor for a neurotransmitter)
Active transport pumps
Proteins that move molecules across the membrane with the use of ATP
Ex: Calcium pump

25. U 1.3.3 Cholesterol is a component of animal cell membrane
Cholesterol is a steroid
It is hydrophobic but had one hydrophilic end
Thus it can fit in the membrane
Cholesterol limit the movement of the phospholipids
Allows membranes to function at a wider temperature range

26. A Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutions
Since they limit the movement of phospholipids cholesterol reduces the fluidity of membranes
It also reduces permeability of the membrane to some hydrophilic particles like sodium and hydrogen ions
This allows animals to maintain concentration differences of these ions
Plant cells do not have cholesterol in their cell membranes
They depend on saturated and unsaturated fatty acids to maintain fluidity in their membranes

27. Topic 1.5 Review Origins of Cells
Essential Idea: There is an unbroken chain of life from the first cells on Earth to all cells in organisms alive today

28. 1.5 The origins of cells
Nature of science: Testing the general principles that underlie the natural world—the principle that cells only come from pre-existing cells needs to be verified. (1.9)
Understandings:
Cells can only be formed by division of pre-existing cells
The first cells must have arisen from non-living material
The origin of eukaryotic cells can be explained by the endosymbiotic theory
Applications and Skills:
Application: Evidence for Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth

29. U 1.5.1 Cells can only be formed by division of pre-existing cells
What are the parts of the cell theory?
Cells come from preexisting cells
Cells are the basic unit of structure and function
All living organisms are composed of one or more cells
What DNA evidence supports this?
Most organisms use the 64 codons of the genetic code
What process did scientist originally think was how cells formed?
Spontaneous generation

30. U 1.5.1 Other evidence to support this:
Cells are complex and no other natural mechanisms for producing cells has been suggested
Populations of cells cannot increase without cell division
Viruses do not consist of cells so they can only reproduce inside of host cells

31. U 1.5.2 The first cells must have arisen from non-living material
Unless cells came from somewhere else in the universe they must have come from non-living material
Hypothesis for how life might have started
Miller-Urey Experiment- production of carbon based compounds (amino acids and sugars)
Deep sea vents- assembly of carbon compounds into polymers
Membrane formation- naturally molecules would form bilayers
DNA as a molecule of inheritance

32. U 1.5.3 The origin of eukaryotic cells can be explained by the endosymbiotic theory
What is the endosymbiotic theory?
Mitochondria and chloroplast were once free living and were incorporated into a prokaryotic cell through what process?
Endocytosis
What type of symbiotic relationship was this?
Mutualistic
What are some special things mitochondria and chloroplast have that support this theory?
They have their own circular DNA
They have their own 70S ribosome
They transcribe their own DNA
They can only reproduce from pre-exiting mitochondria and chloroplasts
Double membranes

34. A Evidence for Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth
What famous experiment did Louis Pasteur perform?
Swan-neck flask Experiment
Explain
Conclusion- swan-neck prevented organisms in the air from entering thus no organisms appeared spontaneously