- Essentials - quick revision through the whole topic
- Summary list for 1.1 Introduction to cells
- Mindmaps
- Skills video tutorial on calculating size
- Model answer
- Model answer
- Model answer
- Model answer
- Multiple Choice questions
- 1.1 Intro to cells quiz 1/1
- 1.1 Intro to cells (2) 1/1
Learn the biological vocabulary for 1.1 Introduction to cells and test yourself using these flash cards.
Summary list for 1.1 Introduction to cells
Cell theory
- According to cell theory, living organisms are composed of cells.
- Organisms consisting of only one cell carry out all functions of life in that cell, e.g. Paramecium, Chlorella.
- Identifying the characteristics of living things (Mr H. Gren - metabolism, response, homeostasis, growth, reproduction, excretion & nutrition).
- 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, (Emergent properties).
- Specialised tissues can develop by cell differentiation in multicellular organisms.
- Differentiation involves the expression of some genes and not others in a cell.
- Stem cells can divide and differentiate along different pathways in embryonic development which makes stem cells useful for therapeutic uses (e.g. Stargardt's disease).
- There are ethical concerns about the use of embryo stem cells.
Calculating magnification and size
- Calculate the magnification of an electron microscope image from a scale bar.
- Calculate specimen size using a scale bar.
- Calculate specimen size using magnification.
Mindmaps
These diagrams summarise the main sections of topic 1.1.
Test if you can draw something like these concept maps from memory.
Can you ask several questions about the points using command terms, e.g List, Describe, Outline, Explain,
Skills video tutorial on calculating size
How to calculate the size of a cell using the scale bar.
Calculating cell size using a scale bar from David Faure on Vimeo.
This is a tricky structured question which brings together several aspects of the topic 1.1
Explain the origins of multicellular organisms and its biological significance. [5]
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Try to write an answer first then compare your answer with the model answer shown below, and explained in the video.
[Many thanks to Catarina Gouveia, St. Dominic's International School, Portugal, for this question and mark scheme]
You previously looked at a video on cell size. Now see if you can do a true size calculation.
This question requires knowledge of converting to true size using magnification.
The size of a mitochondrion on an electron micrograph is 43 mm.
If the magnification of the micrograph is x20000 calculate the true size of the mitochondrion. (2 marks).
Show your calculation, you may gain marks for the method of the calculation even if your answer is incorrect.
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Multiple Choice questions
This quiz contains a set of multiple choice questions covering the topic.
Explanations of each answer are displayed after you click to check the answer(s).
START QUIZ!
The 'Cell theory' explains the nature of living things.
Which statement best describes Cell theory?
According to cell theory, living organisms are composed of cells.
Cells come from pre-existing cells and cells are the smallest using of life.
Cell theory covers most, but not all cases.
Which one of these statements is an exception?
Exceptions to cell theory are : multinucleated striated muscle the giant single celled Acetabularia algae.
Also, organisms consisting of only one cell carry out all functions of life in that cell. e.g. Paramecium, Chlorella.
There are seven processes which are said to be possessed by all living things.
This sweet pea plant has grown a tendril around some string, to help support its upward growth.
Which of the characteristics of living things is illustrated in this photo?
The characteristics of living things (Mr H. Gren - metabolism, response, , homeostasis, growth, reproduction, excretion & nutrition)
The fly is responding to the closing trap, and the trap has responded to the presence of the fly.
What is the importance of surface area to volume ratio to cells?
Surface area to volume ratio is important in the limitation of cell size.
When nerve cells form brain tissue they can store memories, create thoughts and coordinate movement.
If you only ever studied individual nerve cells you would never see these abilities which the brain has.
What is this type of property called?
Multicellular organisms have properties that emerge from the interaction of their cellular components. (Emergent properties)
The image shows a range of different cell types in the leaf of a Yucca plant.
How do stem cells form this range of cells?
What is the process called?
Specialised tissues can develop by cell differentiation in multicellular organisms.
Differentiation involves the expression of some genes and not others in a cell.
Stargardt's disease is vision loss caused by the death of both cone cells and rod cells in the part of the retina around the fovea. One potential treatment for Stargardt's disease is the use of human embryonic stem cells.
What are the properties of these stem cells, which other cells don't have, that makes them so useful for this treatment?
Stem cells can divide and this help researchers to grow them in the lab.
They can differentiate along different pathways in embryonic development which makes stem cells useful for therapeutic uses (e.g. Stargardt's disease) because they can be grown into many different tissues.
The electron microscope image below shows a scale bar marked with 100µm.
The large 'goblet cell' in the centre is producing mucous which will protect the surface of the epithelium.
What is the diameter of the goblet cell?
Calculate specimen size using a scale bar?
You can often estimate the size using the scale bar and your thumb?
More accurately, measure the scale bar length in mm, measure the diameter of the cell, in mm
divide cell diameter by scalebar and multiply by 100µm
The image below shows erythrocytes and leucocytes.l.
Using the scale bar and the ruler placed on the image, estimate the magnification of the image.
Which answer is the best estimate
Calculate the magnification of an electron microscope image from a scale bar?
Convert the ruler measurement to the same units written on the scale bar, in this case 25mm is 25000µm
then divide the ruler measurement 25000 by the number on the scalebar, 25.
The blood cells below were imaged using an electron microscope.
The magnification is x3000 and the ruler measures the central cell as being 2 cm in diameter.
Estimate the actual size of this white blood cell.
Calculate specimen size using magnification?
First change the size measurement into µm units = 20000µm
Then divide by the magnification. 20000 / 3000 = 20 / 3 = 6.6 µm
If you know someone with a disease that might be cured by stem cell therapy then you might be a supporter of this research. You probably also know that some other people have deep concerns.
Which of the following is not a potential benefit of the use of stem cells?
There are ethical concerns about the use of embryo stem cells.
The research is expensive, and potential treatments are also likely to be expensive, and probably not available to all.
Many people who are against stem cells say that it is because cells are taken from human embryos, which have the potential for human live, and should be protected. There are other sources of stem cells, they argue.
Click the '+' symbol to open the next quiz.
START QUIZ!
Which phrases most accurately describe a multicellular organism?
Comment: The multicellular condition allows for differentiation into cells of different types and also replacement of cells when injured or damaged.
Which two processes are involved in cell differentiation?
Comment: During differentiation genes may be activated or repressed causing the formation of different proteins by the ribosomes but other organelles such as mitochondria continue to function in the same way
Which is the best definition of a tissue?
Comment:Tissues may have one or several cell types and one or more functions
Which of the following could be used to distinguish a living from a non-living object?
Comment: Inanimate objects can move, produce and utilise energy but the process of respiration is exclusive to living systems
Human red blood cells are circular and 0.6 μm in diameter. A photograph of a red blood cell is shown as an illustration in a book with a diameter of 1.2mm. What is the magnification of the diagram?
Comment: Convert 1.2 mm into μm by multiplying x 1000 = 1200 μm (so that both units are the same). Then you can see that 0.6 x 2000 = 1200. Or use the formula Magnification = Image size/true size. If the photograph is larger than the cell, the magnification could not be 0.5x which would make it smaller. Eliminate obviously incorrect answers.
Which is the correct order of SI units, beginning with the largest?
Comment: SI units always have a differential of 1000. The unit without the prefix is the standard SI unit (metre, m). B and D are clearly wrong, eliminate those answers first.
The image below is of Dracaena leaf upper epidermis cells.
Which of the following is the best estimate of the length (from top to bottom) of an epidermal cell?
Comment: The cells are approximately the same height as the scale bar length. So 70µm is the best estimate.
If you wished to gain a more precise estimate of the size of the epidermal cells in the photo above, which phrase best describes the reason that you would count several rows and not only one?
Comment: Repeats are used to calculate means when there is variation (in this case, of length). A,B and C could also be considered correct but D is the most valid answer.
Drag and drop activities
Test your construction of biological explanations using the drag and drop questions below.
The multicellular nature of many organisms.
Drag and drop the correct term into the gap to describe differentiation.
functions proteins tissues differentiation gene expression types stem
In a multicellular organism, there are specialised that develop from cells by . Differentiation involves altering gene , genes that code for needed for cell development are expressed in the cells, hence the cells have varied due to the of protein synthesised.
Correct terminology is needed to discuss cell development.
Click the '+' symbol to open the next explanation.
If you want to review key terminology and have some fun with your revision try this word shoot game.
It will help you remember the terms through repetition.
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