Cell theory and microscope ib review
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Cell theory states that all organisms are made of cells. This is true in most cases but there are some notable exceptions, like skeletal muscle. This topic covers the cell theory, the exceptions to cell theory and how cells differentiate during cell growth. Using microscopes is part of the topic, as is measuring the size of cells. Show Learn the biological vocabulary for 1.1 Introduction to cells and test yourself using these flash cards. Cell theory
Calculating magnification and size
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, How to calculate the size of a cell using the scale bar. Calculating cell size using a scale bar from David Faure on Vimeo. Exam question on multicellular organisms 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] ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. 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] Explain the origins of multicellular organisms and its biological significance. [8] Multicellular organisms are organisms made from many cells. Multicellular organisms originated from a unicellular organism. Cells started to divide because growing bigger was not an advantage / it is limited by low SA:VOL ratio. The evolution of multicellular organisms allowed specialization of cells and tissues. Specialized tissues can develop by cell differentiation in multicellular organisms. Differentiation involves the expression of some genes in a cell’s genome and not others. Multicellular organisms can be bigger than unicellular organisms. Large size can allow the organism to reduce their metabolic rate. Large organisms can be more independent with regards to the environment / they can modify their enviroment. Extra exam question on cell function - - - click the + symbol to open it -- > This question requires knowledge of the functioning of single celled and multicellular organisms. Write your answer and then compare it with the model answer Distinguish between single celled condition and the multicellular condition. (4 marks). ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. Write your answer and then click on the "+" icon for a model answer. Distinguish between single celled condition and the multicellular condition. (4 marks). Distinguish between means give an account of the differences putting both comparators in each sentence.
Extra exam question on specialised cells - - - click the + symbol to open it -- > Exam style question on cell differentiation. This question requires knowledge of the mechanism of cell differentiation. Write your answer to the question and then compare your answer with the model answer. Explain how stem cells replicate to produce mature, specialised cells (4 marks) Command term hints: Explain means that you must include details of reasons and causes. ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. ........................................................................ .................................................................. Write your answer then click on the "+" icon to see a model answer Explain how stem cells replicate to produce mature, specialised cells (4 marks)
Extra exam question on calculating magnification - - - click the + to open it -- > 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. Show your calculation, you may gain marks for the method of the calculation even if your answer is incorrect. ........................................................................ .................................................................. ........................................................................ .................................................................. Click on the "+" icon to see a model answer of the calculation. 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). One method divides by the magnification first.
Another option is to convert the mm measurement into µm first. This avoids so many decimals.
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). The 'Cell theory' explains the nature of living things. Which statement best describes Cell theory? Cells divide by meiosis. Cells make up all living organisms. Cells are composed of C, H and O. Cells can carry out photosynthesis. 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? The theory of spontaneous generation has been disproven. Striated muscle cells don't have a nucleus. Human skin is made of layers of cells which are dead. Acetabularia algae are made from a single giant cell, not multiple small cells. 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? Response to the environment. Homeostasis. Excretion. Nutrition. 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? It limits the size of cells It controls the shape of cells. It affects the respiration rate in cells. It limits the amount of DNA in the cytoplasm. 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? A peripheral property. An integral property An emergent property. A powerful property. Multicellular organisms have properties that emerge from the interaction of their cellular components. (Emergent properties) Cell enlargement causes the differences, controlled by auxins. The process is cell apoptosis, cells change because of the nucleus. Mitosis causes stem cells to multiply and change. The process is cell differentiation, controlled by gene expression. 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? They are unspecialised and can differentiate to become any type of specialised cell. They can make antibodies to protect against disease in the eye. They have a large surface area to volume ratio which increases exchange of substances. They are able to detect light which helps repair the eye. 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? 80000 µm 80 µm 250 µm 20 µm 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. 6000µm 6.6 µm 0.6µm 60 µm 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? Stem cell research is a cheaper treatment than many other treatments. Stem cells could provide a treatment for Stargadts disease. Damaged nerve cells could be replaced by stem cells. Human tissues could be grown to replace damaged tissues. 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. Which phrases most accurately describe a multicellular organism? Many cells of varying types with no cell differentiation nor replacement. Many cells of varying types with cell differentiation and replacement. Many cells of the same type with cell replacement but no cell differentiation. Many cells of the same type with cell differentiation and replacement. 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? No change in gene expression or organelle function. No change in gene expression and a change in function of organelles. A change in gene expression and the formation of new organelles. A change in gene expression causing some organelles to produce different products. 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? A group of identical cells carrying out more than one function. A group of identical cells carrying out one function. A group of one or more types of cells carrying out one or several related functions. A small number of cells with one function. 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? Can utilise energy Can respire Can move Can produce energy 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? m mm μm nm m mm nm μm mm m μm nm μm nm m mm 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? 0.007 mm 30 μm 0.7 mm 70 μm 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? Taking repeats is more accurate. Counting repeats and calculating the mean gives more accurate results. I might make a mistake. They are not easy to count. 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. 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 sources, uses and etics of stem cell therapy. How is cell theory related to microscope?The invention of the microscope led to the discovery of the cell by Hooke. While looking at cork, Hooke observed box-shaped structures, which he called “cells” as they reminded him of the cells, or rooms, in monasteries. This discovery led to the development of the classical cell theory. What is the review of the cell theory?The Cell Theory Is a Unifying Principle of BiologyThe cell theory states that all biological organisms are composed of cells; cells are the unit of life and all life come from preexisting life. The cell theory is so established today that it forms one of the unifying principles of biology. What is cell theory IB biology?The cell theory states that: All living organisms are composed of cells. Multicellular organisms (example: humans) are composed of many cells while unicellular organisms (example: bacteria) are composed of only one cell. Cells are the basic unit of structure in all organisms. Cells are the smallest unit of life. What is Topic 1.1 cell theory?According to the cell theory, living organisms are composed of cells. Organisms consisting of only one cell carry out all the functions of life in that cell. Surface area to volume ratio is important in the limitation of cell size. |
