1.1 - IB Cell Biology Notes Statement Guidance

1.1.U1 According to the cell theory, living organisms are composed of cells.

1.1.U2 Organisms consisting of only one cell carry out all functions of life in that cell.

Students are expected to be able to name and briefly explain these functions of life: nutrition, metabolism, growth, response, excretion, homeostasis and reproduction.

1.1.U3 Surface area to volume ratio is important in the limitation of cell size. Be able to explain this, recognize appropriate graphs for this concept, and relate to Topic 1.4 – Cell Transport

1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.

1.1.U5 Specialized tissues can develop by cell differentiation in multicellular organisms.

Understand the process of differentiation from totipotent, pluripotent, multipotent, unipotent

1.1.U6 Differentiation involves the expression of some genes and not others in a cell’s genome.

1.1.U7 The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.

1.1.A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.

If IB names specific examples, then make sure you know them

1.1.A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.

Chlorella or Scenedesmus are suitable photosynthetic unicells, but Euglena should be avoided as it can feed heterotrophically.

1.1.A3 Use of stem cells to treat Stargardt’s disease and one other named condition.

Here they are giving you one to know and the other is your choice.

1.1.A4 Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues.

Compare and contrast, pros and cons of embryonic versus adult stem cells

1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)

Scale bars are useful as a way of indicating actual sizes in drawings and micrographs. This is all about practice and this is almost always a skill asked on the exams.

Flipped Notes Video

Topic 1 – Cells

1.1.U1According to the cell theory, living organisms are composed of cells.

1. State the three core ideas of cell theory: __________________________________________________________________

__________________________________________________________________

__________________________________________________________________

1.1.A1Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae. AND Nature of Science: Looking for trends and discrepancies - although most organisms conform to cell theory, there are exceptions. (3.1)

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2. For each atypical example outline how it challenges conventional cell theory

a. Striated muscle b. Giant algae c. Aseptate fungal hyphae

1.1.U2Organisms consisting of only one cell carry out all functions of life in that cell.

3. State the functions of life, as demonstrated by all living organisms.

Metabolism – __________________________________________________________________

Reproduction – __________________________________________________________________

Sensitivity – __________________________________________________________________

Homeostasis – __________________________________________________________________

Excretion – __________________________________________________________________

Nutrition – __________________________________________________________________

Growth – __________________________________________________________________

1.1.A2Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.

4. Below is an image of a paramecium. Label and annotate the image to indicate how it performs each of the functions of life.

5. Below is an image of a Chlorella. Label and annotate the image to indicate how it performs each of the functions of life.

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1.1.U3 Surface area to volume ratio is important in the limitation of cell size.

As an organism increases in size, its

surface area to volume ratio

_________________

Volume increases ______________ than

the surface area

1cm 2cm 3cm

3

1. Cell Biology (Core) – 1.1 Introduction to cells

Name:6. Explain why small cells are more efficient than big cells:

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

__________

http://www.bioknowledgy.info/ (Chris Paine)

7. What mechanisms other than cell division to cells use to maintain viable, efficient SA:Vol ratios?

1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.

8. Unicellular organisms carry out all the functions of life, multi-cellular organisms differentiate and show emergent properties.a. Describe what is meant by the term emergent properties.

b. Outline the advantages of cells differentiating to carry out specific functions.

1.1.U5Specialized tissues can develop by cell differentiation in multicellular organisms.

MULTICELLULAR ORGANISMS• Multicellular organisms consist of many cells.• These cells do not have to carry out many different functions.• Instead they can become specialised for one particular function and carry it out very efficiently.• This is called differentiation.

• eg: muscle cell, nerve cell, xylem cell• Each cell has all the genes for the organism BUT only certain genes are turned on, the ones

needed for that cells particular function. The others are switched off because the cell does not do that function.

Gene expression• Differentiation is the process during development whereby newly formed cells become more

specialized and distinct from one another as they mature• All cells of an organism share an identical genome – each cell contains the entire set of

genetic instructions for that organism• The activation of different instructions (genes) within a given cell by chemical signals will

cause it to differentiate

STEM CELLS Unspecialised and undifferentiated cells with 2 key qualities

1. Self renewal Can divide and replicate

2. Potency Capable of differentiation

3. Derived from embryos or from the placenta/umbilical cord

Stem cell type Description Examples

Totipotent

Pluripotent

Multipotent

1.1.U6Differentiation involves the expression of some genes and not others in a cell’s genome.

9. All cells in an organism share the same, identical, genome (i.e. they all possess the same genetic information).

a. In which type of cells is the entire genome active?

b. Describe how newly formed cells become specialised.

(Extension: refer to the packaging of genes in your answer – we will learn about this coming up)

1.1.U7The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.

10. Describe what is meant by the term stem cell.

11. Define the following types of stem cells. Giving an example of each:

a. Totipotent

b. Pluripotent

c. Multipotent

d. Unipotent

1.1.A3Use of stem cells to treat Stargardt’s disease and one other named condition.

12. Complete the table to detail the use of stem cells in the treatment of specific conditions.

Condition Stargardt'sb macular dystrophy

Outline the condition and the problems it causes

Affects around one in 10,000

children

Recessive genetic (inherited)

condition

The mutation causes an active

transport protein on photoreceptor

cells to malfunction

The photoreceptor cells

degenerate

the production of a dysfunctional

protein that cannot perform energy

transport

that causes progressive, and

eventually total, loss of central

vision

Describe treatment of the condition using stem cells

The benefit of using stem cells

Stem cells are currently the only viable

treatment for this condition.

1.1.A4Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues. AND Nature of Science: Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5)

13. Complete the table to compare the different sources of stem cells available:

Comparison of stem cell sources

Embryo Cord blood Adult

Differentiation

Can differentiate into

any cell type

Limited capacity to

differentiate (without

inducement only

naturally divide into

blood cells)

Genetic damage

Due to accumulation of

mutations through the life of the

adult genetic damage can

occur

Compatibility

14. Therapeutic cloning remains a controversial area of medicine.a. Outline the main arguments for therapeutic cloning

b. Outline the main arguments against therapeutic cloning

So How Big are these Cell Things ? Reference p. 5-7in your text & Activity 4 & 5 in your workbook

Feature Actual Size Relative Size ComparisonMolecule 1 nm 1 dimeMembrane thickness 10nm 10x larger 3 text books stackedVirus 100 nm 100x Grade 8 studentBacteria 1um 1000x A large classroomOrganelle 10 um 10,000 x schoolAnimal cell 100 um 100,000x campus

*Molecules are too small to be seen with any time of microscope!Below is a table of the microscope sizes that you should be familiar with:

Unit Abbr. Metric Conversion Conversion factorKilometer km 1000m 103 m

m 1mCentimeter cm 102 m

mm 0.001mmicrometer um 0.000 001m

nm 10-9 mRecall SI Units and Unit Conversions:

Show your work for unit conversions THIS WAY AWAYS!!!

Try These below: 5mm = ? nm 4.4cm = ?nm 6.8mm=? um 3.5cm = ? cm 7.1 um = ? cm 1520nm = ?mm

1. Calculate the magnification of these scale bars:

2. Calculate the actual size of these images:

3. What would you need to do if you were only given a scale bar and asked to calculate actual size?Demonstrate by finding the length of this stoma in µm. Show your working.

4. a. Calculate the length of this epithelial cell. b. Calculate the diameter of the nucleus of this cell.

5. a. Calculate the diameter of the main body of this human egg cell AND the thickness of one section of the zona pellucida.

6. Calculate the length of this Elodea cell.

Written questions: (they might appear in this style in the exam)1. A student views an image of a cell magnified 50000 times. The image is 60mm long.

a. What is the actual length of the sample in the image?

b. Is the cell more likely to be a plant cell, animal cell, bacterium or virus? Explain why.

2. A sperm cell has a tail 50µm long. A student draws it 50mm long. What is the magnification?

Finding Total Magnification and the Diameter of the Field of View When using a Microscope

Total Magnification = (power of the eye piece) x (Power of the objective lens)

Field of View = diameter of circle you can see for each magnification

Using a ruler, you find the field of view for low power (4.5 mm)Then, from this measurement, the FOV for the other powers is calculated using the formula:

FOVx = FOV low x Maglow Ex: FOVmed = 4.5mm x (40/100) = 1.8 mm

Magx

Power Total Magnification Diameter of FOV in mm Diameter in umHigh 400x 0.45 mm 450 umMedium 100x 1.8 mm 1800 umLow 40x 4.5 mm 4500 um

Actual Size of Specimen: estimate how many could fit end to end across the diameter of the field of view, then use the following formula

Size of Specimen = diameter of FOV

# of objects the fit across

Drawing Magnification: this is used to determine how many times bigger your drawing is than the actual size

Drawing Magnification = drawing size

Actual size

Scale Bars: Images often carry a scale bar which is a line on the image that shows how long the line is in the real specimen. The easiest way to add a scale bar is to find the actual size of the specimen and then draw a line beside the specimen indicating the measurement

Practicing your new skills

Using one of the prepared slides practice drawing what you see in the space below. Make sure you title, label, size etc. as appropriate

1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)

15. The diagram below shows the characteristic rod-shaped structure of E. coli bacteria.

a. Calculate the magnification of the image.

16. Calculate the actual size of the structures delineated in yellow.

17. Calculate the magnification of these scale bars:

18. What is the magnification of these images?

a. Scale bar 10µm measures 40mm on the image.

b. Scale bar 5µm measures 25mm on the image.

19. A micrograph has a scale bar of 2µm, which measures 40mm on the image. Measuring the maximum length of the cell in the image, the ruler reads 180mm. How long is the cell?

20. A student views an image of a cell magnified 350 times. The image is 250mm long. What is the actual length of the sample in the image?

Citations:

Allott, Andrew. Biology: Course Companion. S.l.: Oxford UP, 2014. Print.

Taylor, Stephen. "Essential Biology 02.1 Cell Theory.docx." Web. 17 Aug. 2014. <https://www.box.net/shared/r2o3scijx1>.

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