1. Topic 1: Cells

2. Cell Theory
Discuss the theory that living organisms are composed of cells.
The Cell Theory states that:
All organisms are composed of one or more cells.
All cells arise from pre-existing cells.
All vital functions of an organism occur within cells.
Cells are the most basic unit of life.
Cells contain hereditary information. Why?

3. Evidence for Cell Theory
What is Evidence?
What is a theory?
Evidence for Cell theory:
Living tissues= composed of cells
Cells of an organism can sometimes survive on their own but smaller cell components can NOT.
Classic experiments showed that spontaneous generation of life= impossible.

4. Exceptions to aspects of the theory?
Skeletal muscle – multinucleate cytoplasm
Some fungal hyphae- multinucleate cytoplasm.
Extracellular material (material outside the cell membrane), such as teeth and bone, forms a significant part of the body.
Some biologists consider unicellular organisms to be acellular.
Do you think these constitute exceptions to cell theory? Justify your answer.

5. State that unicellular organisms carry out all the functions of life.
Discussion: What are the necessary functions of life?
Metabolism
Response to stimuli
Homeostasis
Growth/development
Reproduction
Nutrition
Excretion of wastes
HW:Research each function of life in a Paramecium and Euglena. Create a Data Table for comparison.

6. Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using appropriate SI units.
Molecules (1 nm) (Smallest)
Cell membrane thickness (10 nm)
Viruses (100 nm)
Bacteria (1 µm)
Organelles (<10 µm)
Most cells (<100 µm) (Largest)
Interactive

7. Calculate linear magnification of drawings.
Drawings should show cells and cell ultrastructure.
Include:
A scale bar: |------| = 1 µm
Magnification: ×250
To calculate magnification:
Magnification = Measured Size of Diagram ÷ Actual Size of Object

8. As cell size increases, the surface area to volume ratio decreases
Explain the importance of the surface area to volume ratio as a factor limiting cell size.
The rate of exchange of materials (nutrients/waste) and energy (heat) is a function of its surface area. (Why?)
As cell size increases, the surface area to volume ratio decreases
This can make the exchange rate inadequate for large cells
Cell size, therefore, remains small

9. Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
Differentiation: becoming specialized in structure and function.
Supporting examples?
Multicellular organisms show emergent properties (What??)
See ex. Next slide…
Video:

10. Define tissue, organ and organ system.
Tissue: An integrated group of cells that share stucture and are adapted to perform a similar function.
Organ: A combination of two or more tissues which function as an integrated unit, performing one or more specific functions.
Organ system: A group of organs that specialize in a certain function together.

11. STEM CELLS Stem cells Retain the capacity to divide
Have the ability to differentiate along different pathways.
Therapeutic Use:
Many possibilities
Repair of damaged tissue
Actual uses
Restore neural insulation tissue in rats.
Use of umbilical cord blood stem cells for leukemia patients.
Sources and ethical issues:
Embryonic
placenta/umbilical cord
Many other tissues have stem cells
Pluripotent vs. totipotent/omnipotent
Video:

12. Stem Cell Uses Stargardt’s Disease-
Macular (eye) degeneration, causes central vision loss while periphial vision is still retained
Photreceptors in the retina deteriorate.
Stem cell treatment
using embryonic stem cells to grow new retina cells containing new photoreceptors.
These stem cells are transplanted into the patients retina to restore vision.
HW: Research another Stem Cell Treatment and record into your notebook

13. Prokaryotic Cells
Draw a generalized prokaryotic cell as seen in electron micrographs
The diagram should include:
the cell wall,
plasma membrane,
cytoplasm,
Pili
Flagella
Ribosomes
nucleoid ( region containing naked DNA).

14. State one function for each of the following: cell wall, plasma membrane, mesosome, cytoplasm, ribosomes and naked DNA.
Cell Wall: Maintains the cell's shape and give protection.
Plasma Membrane: Regulates the flow of materials (nutrients, waste, oxygen, etc.) into and out of the cell.
Mesosome: A tightly folded region of cell membrane. (has attached proteins for respiration/photosynthesis)
Cytoplasm: Holds and suspends the cell's ribosomes and enzymes.
Ribosome: Protein synthesis.
Nucleoid region: Contains the cell's genetic material (naked DNA)

15. Binary Fission Prokaryotic cells divide by binary fission Asexual
splits directly into two equal-sized offspring, each with a copy of the parent's genetic material.

16. Identify parts of a Prokaryote Using an Electron Micrograph

17. Harvard Animation Why are cells cool?

18. Eukaryotic Cells
Draw a diagram to show the ultrastructure of a generalized animal cell (liver cell) as seen in electron micrographs.
Should include free ribosomes, rough and smooth ER, lysosome, Golgi apparatus, mitochondria, and nucleus.

19. An Animal Cell

20. Liver cell electron micrographs (objective 1.2)
1. Nucleus 2. Mitochondria 3. Cell border 4. Nucleoli 5. Red blood cell

21. Define organelle.
An organelle is a discrete structure within a cell, and has a specific function.
Describe the functions of the following organelles: (see p. 114/ch.7 of Campbell…)
mitochondrion
golgi body
endoplasmic reticulum
vacuole
lysosome
ribosome In contrast to the other organelles, they are not surrounded by a membrane.
centriole (Unique to animal cells)
chloroplast

22. Cisternae: 0.5µm thick, l-3µm diameter
EUKARYOTE CELL ULTRASTRUCTURE
Summary of the major cell organelles:
Practice: What are the respective magnifications of the cell as a whole and of each of its organelles in the following cell picture?
ORGANELLE
MAIN FUNCTIONS
DIMENSIONS
Nucleus
Cell division, protein synthesis
10 µm diameter
Mitochondrion
Respiration pathways
1.0 to 12.5 µm
Chloroplast
Photosynthetic pathways
5 to 10 µm diameter
Lysosome
Digestion, recycling & isolation
0.5 to 3.0 µm diameter
Golgi apparatus
Secretion, reprocessing, lysosome synthesis
Cisternae: 0.5µm thick, l-3µm diameter
Endoplasmic Reticulum (ER)
Support, Golgi apparatus synthesis.
26 to 56 nm thick
Ribosome
Protein synthesis
20 nm diameter

23. Ribosomes: protein synthesis
State one function of each of these organelles: ribosomes, rough endoplasmic reticulum, lysosome, Golgi apparatus, mitochondrion and nucleus.
Ribosomes: protein synthesis
Rough endoplasmic reticulum (rER): Packages proteins
Lysosome: digests old cell parts, macromolecules (food) and engulfed viruses/bacteria
Golgi apparatus: Modifies, stores and routes products of the endoplasmic reticulum.
Mitochondrion: cellular respiration.
Nucleus: contains genetic material

24. Compare prokaryotic vs. eukaryotic cells.
Prokaryotic cells vs. Eukaryotic cells
Contain naked DNA vs. DNA associated with protein
DNA in cytoplasm vs. DNA enclosed in a nuclear envelope
No membrane-enclosed organelles vs. membrane-enclosed organelles (e.g., mitochondria, chloroplasts)
70S vs. 80S ribosomes

25. Describe three differences between plant and animal cells.
Only plant cells have:
Cell walls
Chloroplasts
Large central vacuoles and tonoplast
Plasmodesmata
Starch granules for storage of carbohydrates
Only animal cells have:
Centrioles
Lysosomes
Glycogen for storage of carbohydrate
Also: Plant cells usually have much less cholesterol in their plasma membranes.

26. Roles of extracellular components (2.3.6)
Animal cells
Extracellular matrix (secreted glycoproteins)
Support
Adhesion
Movement
Plant cell wall (see next slides)

27. Structure and function of organelles within exocrine gland cells of the pancreas and within palisade mesophyll cells (1.2)

28. and within palisade mesophyll cells (1.2)

29. Plant cell wall Main component= cellulose
Cellulose molecules are arranged in bundles called microfibrils.
give the cell wall great tensile strength and allow high pressures to develop inside the cell.
Functions= structure, support, protection.

30. Membranes Draw a diagram of the fluid mosaic model.
Diagram should show
the phospholipid bilayer,
cholesterol,
glycoproteins,
Integral proteins
peripheral proteins.

31. Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes.
Hydrophilic
-”water loving”
-phosphate heads
Hydrophobic
-”water-fearing”
-fatty acid tails

32. Functions of membrane proteins
Hormone binding sites.
Enzymes
Cell adhesion
Attachment to the cytoskeleton and extracellular matrix
Cell communication
Signal transduction
Cell-cell recognition
Channels for passive transport
Pumps for active transport.
Electron carriers

33. Define diffusion
Diffusion: the passive movement of particles from a region of higher concentration to a region of lower concentration, as a result of the random motion of particles.
Animation

34. Define Osmosis
Osmosis: the passive movement of water molecules, across a selectively permeable membrane, from a region of lower solute concentration to a region of higher solute concentration. (i.e. the diffusion of water)
Remember: Lowers solute concentration = higher water concentration!!!
Hypertonic (hyperosmotic)
Hypotonic (hypoosmotic)
Isotonic (isoosmotic)
effect of osmosis on cell animation

35. Explain passive transport across membranes in terms of diffusion.
Simple diffusion
facilitated diffusion.
No ATP used
Channel proteins (integral membrane proteins)
Down concentration/electrochemical gradient
Specific
ex. Ion Channels in neurons

36. Explain the role of protein pumps and ATP in active transport across membranes.
Active transport is the movement of substances across membranes using energy from ATP.
moves substances against a concentration gradient.
Carrier proteins– protein pumps
Active transport animations:

37. Types of transport

39. Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus, and plasma membrane.
Proteins synthesized by ribosomes
enter the rough endoplasmic reticulum.
Vesicles bud from rER and carry the proteins to the Golgi apparatus.
Golgi apparatus modifies the proteins.
Vesicles bud off from the Golgi apparatus and carry the modified proteins to the plasma membrane.

40. Exocytosis
Describe how the fluidity of the membrane allows it to change shape, break and reform during exocytosis.
In exocytosis vesicles fuse with the plasma membrane. The contents of the vesicles are then expelled. The membrane flattens out again.
animations:

41. Endocytosis
Describe how the fluidity of the membrane allows it to change shape, break and reform during endocytosis
In endocytosis part of the plasma membrane is pulled inwards.
A droplet of fluid becomes enclosed when a vesicle is pinched off.
Vesicle can then move through the cytoplasm carrying its contents.

42. Cell Division
State that mitosis is division of the nucleus into two genetically identical daughter nuclei.
New cells are produced by the division of existing cell, remember the cell theory.
Interphase: DNA replication and transcription occurs. Also, normal cell life.
Mitosis: Cell begins to divide.
Cytokinesis: The cell finishes dividing and the cytoplasm splits between them.

43. Mitosis

44. Interphase Beginning of Cell Cycle
Interphase is an active period in the life of a cell when many biochemical reactions occur:
protein synthesis (transcription and translation)
DNA Replication
Increase in number of mitochondria and/or chloroplasts etc.

45. Interphase continued…
Phases of Interphase
G1 = growth, protein synthesis, increase mitochondria/
chloroplasts
S = DNA Replication
G2 = growth, increase in organelles, preparation for cell division.

46. What controls Cell Cycle?
Cyclins
Control Cell Cycle
Proteins that ensure that tasks within the Cell Cycle are performed at the correct time and moves the cell on to the next stage of the cycle when appropriate
Four groups of Cyclins (1 per stage)
How do they do it?
Cyclins bind to enzymes called cyclin-dependent kinases
These kinases become active and attach phosphate groups to other proteins which triggers a reaction that carries out tasks specific to one of the phases of the cell cycle
Unless these cyclins reach a threshold concentration, the cell does not progress to the next phase in the cell cycle.

47. Describe the events that occur in the four phases of mitosis…
Prophase
the mitotic spindle (made from microtubules) starts growing (going from pole to pole).
Condensation of Chromosomes
Chromatin coils up to form distinct chromosomes.
Process is called Supercoiling
(Each chromosome contains two identical sister chromatids, attached to each other at the centromere region.)
The nuclear envelope starts breaks down.

48. …Describe the events that occur in the four phases of mitosis…
Metaphase
each chromosome attaches to two spindle microtubules (one going to each pole) at the centromere.
line up at the equator
mitotic spindle is fully developed
some microtubules are attached to chromosomes and reach to the equator; others go from pole to pole.

49. …Describe the events that occur in the four phases of mitosis…
Anaphase
the spindle microtubules pull the sister chromatids to opposite poles
each sister chromatid becomes one new chromosome of the daughter cell.

50. Telophase
each sister chromatid reaches its pole (becoming a chromosome).
nuclear envelope starts to reform. Spindle microtubles deteriorate.
Cytokinesis (division of the cytoplasm) takes place.

51. Summary of Mitosis

52. Summary of mitosis continued

53. In your journal
Explain how mitosis produces two genetically identical nuclei. (an IB standard)

54. Outline the differences in mitosis and cytokinesis between animal and plant cells. (limit this to the lack of the centrioles in plant cells and the formation of the cell wall.)
Animals:
Centrioles
No cell wall
Plants:
No centrioles
Cell wall (cell plate) is formed between cells as vesicles transport cell wall materials to middle.

55. Cancer cells do not respond to cell cycle regulation
State that mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumors.
Cancer cells do not respond to cell cycle regulation
Mutagens– Agents that produce changes in genes involved in controlling the cell cycle
Produce Oncogenes that cause uncontrolled Cell Division
Tumor: benign (don’t spread) or malignant (do spread)
Result from uncontrolled cell division
Metastasis – spreading of cancer cells to other areas
(Cancer Warrior– angiogenesis resources)
(Video: Cancer Warrior-- angiogenesis)

56. Cancer
(Cancer Warrior– angiogenesis resources)
(Video: Cancer Warrior-- angiogenesis)

57. Characteristics of Viruses
State that a virus is a non-cellular structure consisting of DNA or RNA surrounded by a protein coat.
Characteristics of Viruses
not considered living
no metabolism.
Unable to reproduce without a host
Others?

58. Explain three advantages of using light microscopes.
color instead of monochrome (black and white) images.
large field of view.
Facilitate preparation of sample material.
Allow for the examination of living material and the observation of movement.
Relatively inexpensive

59. Outline the advantages of using electron microscopes.
1) higher resolution and magnification than light microscopes.
Resolution refers to the ability to distinguish two objects as seperate entities.
Magnification refers to the ability to increase the size of a viewed object.
2) May provide a three dimensional view.
Scanning Electron Microscopes (SEM) provide images of the specimen's surface
Transmission Electron Microscopes (TEM) provide images of a sample's interior. The resolution of an SEM is approximately half that of a TEM.
TEM SEM