1. CELL THEORY
Topic 2.1
IB Biology
Miss Werba

2. TOPIC 2 - CELLS 2.1 CELL THEORY 2.2 2.5 CELL DIVISION
PROKARYOTIC CELLS
2.3
EUKARYOTIC CELLS
2.4
MEMBRANES
2.5 CELL DIVISION
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3. THINGS TO COVER Outline of cell theory Evidence for the cell theory
Unicellular organisms
Relative sizes of cells
Magnification
Surface area: Volume ratios and cell size
Emergent properties
Cell differentiation
Stem cells
Therapeutic use of stem cells
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4. CELL THEORY All living things are made of cells
2.1.1
2.1.2
CELL THEORY
All living things are made of cells
Cells are the smallest unit of life
Existing cells come from other cells
Cells contain a blueprint for their growth, development & behaviour
Cells are the site of all of the chemical reactions of life
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5. 2.1.1
2.1.2
CELL THEORY
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6. 2.1.1
2.1.2
CELL THEORY
Evidence:
With the invention of microscopes (Janssen) scientists could see cells (Hooke, Leeuwenhoek)
Pasteur demonstrated that cells couldn’t grow in sterile conditions (disproved abiogenesis)
Organelles and viruses cannot carry out all of the characteristics of other living things
Cell division is visible under a microscope
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7. FUNCTIONS OF LIFE Command term = STATE
2.1.3
FUNCTIONS OF LIFE Command term = STATE
Unicellular organisms carry out all the functions of life:
Movement
Respiration
Sensitivity or stimulus response
Composed of cells
Growth
Reproduction
Excretion
Nutrition
MRS C GREN
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8. CELL SIZE Use your logic to put these in the correct order!
2.1.4
CELL SIZE Use your logic to put these in the correct order!
Bacteria
Cell membrane thickness
Cells
Molecules
Organelles
Virus
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9. CELL SIZE Relative sizes
2.1.4
CELL SIZE Relative sizes
Cells (<100 μm) - generally plant cells are larger than animal cells
Organelles (<10 μm)
Bacteria (1μm)
Virus (100nm)
Cell membrane thickness (10nm)
Molecules (1nm)
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10. CELL SIZE Relative sizes
2.1.4
CELL SIZE Relative sizes
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11. CELL SIZE Magnification
2.1.5
CELL SIZE Magnification
Measurements need to be in the same units!
1mm =1000μm
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12. CELL SIZE Magnification – sample questions
2.1.5
CELL SIZE Magnification – sample questions
A red blood cell is 8μm in diameter. If drawn 100 times larger than its actual size, what diameter will the drawing be in mm?
If a mitochondrion has a length of 5µm and a student’s drawing of the mitochondrion is 10mm, what is the magnification of the drawing?
If a Sequoia sempervirens tree is 100m tall and a drawing of it is 100mm tall, what is the magnification of the drawing?
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13. CELL SIZE Magnification – sample answers
2.1.5
CELL SIZE Magnification – sample answers
0.8 mm
×2000
×0.001
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14. CELL SIZE Limitations Cells cannot grow indefinitely.
2.1.6
CELL SIZE Limitations
Cells cannot grow indefinitely.
They reach a maximum size and then they may divide.
If a cell becomes too large, it would develop problems.
These problems may include….?
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15. 2.1.6
CELL SIZE Limitations
The rate of metabolism varies with a cell’s volume
The rate of molecular exchange varies with a cell’s surface area
When a cell grows, volume grows quicker than surface area and the cell must divide or die
Many cells contains structures to increase their SA:Vol ratio
eg. microvilli
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16. WHAT MAKES US BETTER THAN BACTERIA?
2.1.8
WHAT MAKES US BETTER THAN BACTERIA?
Unicellular organisms are in the Kingdom Protoctista (Protists)
They evolved 3-4 billion years ago.
They remained the dominant life form until 600 million years ago.
Unicellular organisms are able to carry out all of the typical cellular processes within their single cell!
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17. WHAT MAKES US BETTER THAN BACTERIA?
2.1.8
WHAT MAKES US BETTER THAN BACTERIA?
Kingdom Plantae, Animalia and Fungi are all composed of eukaryotic cells
They are multicellular organisms – made up of many cells together.
These cells specialise so that all energy in the cell is not taken up by performing all cellular functions.
These cells group into tissues, organs and systems making us far more capable than a single bacterial cell.
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18. CELL DIFFERENTIATION Differentiation:
2.1.8
CELL DIFFERENTIATION
Differentiation:
process by which newly-formed cells specialize as they mature
Cells in multicellular organisms share the same genetic info (cf. cell division, reproduction, formation of blastocyst)
What is different between cells is gene expression
Chemical signals lead to differential gene expression and thus specialization of cells
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19. 2.1.8
CELL DIFFERENTIATION
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20. EMERGENT PROPERTIES Command term = STATE
2.1.7
EMERGENT PROPERTIES Command term = STATE
The combination of different cell types can give rise to emergent properties in multicellular organisms
Means that the whole organism is greater than the sum of its parts:
b/c of the varied gene expression
b/c of the complex interactions between cells
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21. STEM CELLS Command term = STATE
2.1.9
STEM CELLS Command term = STATE
Stem cells retain the capacity to divide
They are undifferentiated
They have the ability to differentiate along different pathways
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22. THERAPEUTIC USE OF STEM CELLS
2.1.10
THERAPEUTIC USE OF STEM CELLS
Stem cells have the potential for tissue repair and can theoretically treat a variety of degenerative conditions
In 1968, doctors performed the first successful bone marrow transplant.
Bone marrow contains somatic stem cells. It is transplanted routinely to treat a variety of blood and bone marrow diseases, blood cancers, and immune disorders.
More recently, peripheral blood stem cells (from the blood stream) and umbilical cord stem cells have been used to treat some of the same blood-based diseases.
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23. THERAPEUTIC USE OF STEM CELLS
2.1.10
THERAPEUTIC USE OF STEM CELLS
eg. Parkinson’s Disease, MS, strokes
all involve loss of neurons or other cells in the nervous system
could potentially use stem cells to replace them
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24. THERAPEUTIC USE OF STEM CELLS
2.1.10
THERAPEUTIC USE OF STEM CELLS
eg. Leukaemia
a cancer of white blood cells or leukocytes
chemotherapy is normally used to kill the abnormal cells; however, a bone marrow transplant is needed if it doesn't work.
The patient's existing bone marrow and abnormal leukocytes are first killed using chemotherapy and radiation.
A sample of donor bone marrow containing healthy, matched stem cells is introduced into the patient's bloodstream.
If the transplant is successful, the stem cells will migrate into the patient's bone marrow and begin producing new, healthy leukocytes to replace the abnormal cells.
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25. THERAPEUTIC USE OF STEM CELLS
2.1.10
THERAPEUTIC USE OF STEM CELLS
eg. Burn treatment
Therapeutic cloning can be used to regenerate skin cells in burns victims
Use the nucleus from the required cell to generate new cells with the correct genetic information – eg. skin cells
See Topic 4.4 for detailed process
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26. 2.1.10
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27. 2.1.10
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