IBDP CORE>TOPIC 1.1 CELL THEORY, CELL SPECIALISATION AND CELL REPLACEMENT
UNDERSTANDINGS:
According to the cell theory, living organisms are composed of cells.
Organisms consisting of only one cell carry out all functions of life in that cell.
Surface area to volume ratio is important in the limitation of cell size.
Multicellular organisms have properties that emerge from the interaction of their cellular components.
Specialised tissues can develop by cell differentiation in multicellular organisms.
Differentiation involves the expression of some genes and not others in a cell’s genome.
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.
Organisms consisting of only one cell carry out all functions of life in that cell.
Surface area to volume ratio is important in the limitation of cell size.
Multicellular organisms have properties that emerge from the interaction of their cellular components.
Specialised tissues can develop by cell differentiation in multicellular organisms.
Differentiation involves the expression of some genes and not others in a cell’s genome.
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.
DAY 1
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2. Multicellular and unicellular organisms: The functions of life.
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Application: questioning the cell theory
Are there cells that do not follow the cell theory?
2. GIANT ALGAE: Acetabularia
The mature Acetabularia is 0.5 to 10 cm tall and has three anatomical parts: a bottom rhizoid that resembles a set of short roots; a long stalk in the middle; and a top umbrella of branches that may fuse into a cap. The single nucleus of Acetabularia is located in the rhizoid, and allows the cell to regenerate completely if its cap is removed. http://en.wikipedia.org/wiki/Acetabularia |
Application: Investigation of functions of life in Paramoecium and one named photosynthetic unicellular organism
CELLS AND MICROSCOPY
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Collect information on timeline of microscopy and prepare a movie for the same.
Include the differences between light and electron microscope You will work in groups. The movie has to be submitted on Monday. (29th Dec) check this link- http://www.youtube.com/watch?v=yf2oop3pbMY FINAL MOVIE BY THE GROUPS |
Light microscope
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Electron microscope
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SKILL: Calculation of magnification of drawings and the actual size of structures.
magnification-cell_measurement_2015.docx | |
File Size: | 1201 kb |
File Type: | docx |
The importance of the surface area to volume ratio as a factor limiting cell size. (ACTIVITY- LAB) (PSOW -1)
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We perform an activity as shown in the video beside to find the importance of surface area to volume ratio for a cell.
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Surface area to volume ratio as a factor limiting cell size
1.As size increases both surface area and volume increase,
2.However volume increases more / ratio of surface area to volume decreases as size of cell increases; 3.Rate of metabolism is a function of its mass to volume ratio; 4.Surface area limits/affects the rate at which substances can enter (or leave) the cell; 5.Volume determines the rate at which material is produced/used; 6.Oxygen/nutrients/substances will take too long to diffuse into/out of the centre of the cell if it is too big; 7.Excretory products would take too long to be eliminated; 8.Heat will take too long to be eliminated; 9.Example of cell adaptation to increase the ratio of surface area: volume e.g. root hair cell; |
Why doesn’t the cells grow to a large size?
1.The larger the size the smaller the surface area to volume relationship;
2.If a cell becomes too large it cannot absorb oxygen / CO2 (in plants) fast enough; 3.If a cell becomes too large it cannot absorb foods / nutrients fast enough; 4.If a cell becomes too large it cannot excrete waste products / CO2 fast enough; diffusion in the cell becomes too slow; 5.Centre of the cell is too far from the membrane; nucleus cannot control a cell above a certain size; 6.Heat not lost quickly enough; 7.Not enough mRNA / proteins / enzymes produced; 8.Large cells may be structurally weak; 9.Cell wall / membrane provides support; 10.Larger blood cells would not fit through capillaries; 11.Sperm / large cells might not move quickly enough; 12.Having many small cells allows differentiation; |
Multicellular organisms show emergent properties.
- Organisms can achieve more than the sum of what each part could achieve individually.
- Cells perform their task when they interact with each other rather than when they are alone.
Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.
Students watch the video and class discussion leading to cell differentiation
Differentiation is development in specific ways Cells carry out specialized functions Considering a differentiated cell in a multicellular organism- Cells have all genes so could develop in any way. Some genes are expressed but not others. The position / hormones / cell to cell signals / chemicals determine how a cell develops; A group of differentiated cells is a tissue |
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State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. (ACTIVITY- POSTER MAKING)
POSTER MAKING…. "STEM CELL THERAPY- BOON OR BANE"
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RUBRICS FOR THE POSTER MAKING
1. Innovativeness/Effectiveness- 2
2. Neatness/Clarity- 2
3. Correctness of the content- 3
4. Timely completion- 2
5. Overall appearance- 1
1. Innovativeness/Effectiveness- 2
2. Neatness/Clarity- 2
3. Correctness of the content- 3
4. Timely completion- 2
5. Overall appearance- 1
Home work assignment- Answer the following questions (submission 7th Jan)
1. what are stem cells?
2. Mention the types of stem cells.
3. Why are embryonic stem cells preferred?
4. What are the limitations of using embryonic stem cells?
5. List some of the incurable diseases that can be cured with stem cells.
1. what are stem cells?
2. Mention the types of stem cells.
3. Why are embryonic stem cells preferred?
4. What are the limitations of using embryonic stem cells?
5. List some of the incurable diseases that can be cured with stem cells.
APPLICATION:Use of stem cell to treat Stargardt's macular degeneration disease
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http://www.bbc.co.uk/news/health-15025009
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Outline one therapeutic use of stem cells.
- Stem cells are cells that retain the capacity to divide and have the ability to differentiate along different paths into all types of cells
- These cells are pluripotent/totipotent;
- Stem cells are derived from blastocysts/human embryos, left over from IVF/placenta/umbilical cord/some adult tissues;
- New techniques/technologies rely on replacing diseased/dysfunctional cells with healthy/functioning ones;
- Need to identify desired type of stem cell and grow in culture/special solutions/controlled conditions;
- Develop biochemical solution that will cause cells to differentiate into desired cell type;
- Develop means of implanting/integrating cells into patient’s own tissues so that they function with the body’s natural cells;danger of rejection of cells therefore need to suppress immune system;
- Must make sure new cells do not become overgrown/develop into cancerous tumours;
- E.g. retinal cells; replace dead cells in retina to cure presently incurable diseases such as glaucoma and macular degeneration;
- E.g. graft new skin cells; to treat serious burn victims;
- E.g. nerve tissue; help repair catastrophic spinal injuries / help victims of paralysis regain movement;
APPLICATION: Ethics of therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new born and from adult's own tissues.
Embryonic stem cells: The zygote divided to form about 12-16 cells are the embryonic stem cells. These cells can for any cell, however they have a high risk of developing tumour.
Cord stem cells:These cells are taken from the umbilical cord and can be obtained easily. They can be frozen and stored easily and used later.
Adult stem cells: Adult tissue like bone marrow shows limited cell differentiation capacity.
Cord stem cells:These cells are taken from the umbilical cord and can be obtained easily. They can be frozen and stored easily and used later.
Adult stem cells: Adult tissue like bone marrow shows limited cell differentiation capacity.
Stem cells can cause cancer.
Read the link …. How is the scientific community responsible for conveying information to the society.
Read the link …. How is the scientific community responsible for conveying information to the society.
References-
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All picture have been downloaded from Google images for educational purpose only
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All picture have been downloaded from Google images for educational purpose only