Recognize that cells are composed primarily of a few elements (carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur), and describe the basic molecular structures and the primary functions of carbohydrates, lipids, proteins and nucleic acids.
Recognize that the work of the cell is carried out primarily by proteins, most of which are enzymes, and that protein function depends on the amino acid sequence and the shape it takes as a consequence of the interactions between those amino acids.
Describe how viruses, prokaryotic cells and eukaryotic cells differ in relative size, complexity and general structure.
Explain the function and importance of cell organelles for prokaryotic and/or eukaryotic cells as related to the basic cell processes of respiration, photosynthesis, protein synthesis and cell reproduction.
Compare and contrast passive transport (including osmosis and facilitated transport) with active transport, such as endocytosis and exocytosis.
Explain the process of mitosis in the formation of identical new cells and maintaining chromosome number during asexual reproduction.
MN Standard in Lay Terms
*Cells are primarily composed of six elements (carbon, hydrogen, oxygen, nitrogen, phosphorous, and sulfur). When put into molecules, these elemments help the cell to perform its functions.
*Enzymes are important proteins that regulate chemical reactions that occur in cells.
*Single cell organisms and multicellular organisms carry out cellular functions differently.
*Cell parts have specific functions that allow an organism to grow, survive, and reproduce.
*To carry out cellular functions, molecules must move through a cell membrane.
*Cells must divide to be efficient at cellular functions.
A cell is the basis unit of life; the process that occur at the cellular level provide the energy and basic structure organisms need to survive.
MN Standard Benchmarks
126.96.36.199.1 Recognize that cells are composed primarily of a few elements (carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur), and describe the basic molecular structures and the primary functions of carbohydrates, lipids, proteins and nucleic acids.
188.8.131.52.2 Recognize that the work of the cell is carried out primarily by proteins, most of which are enzymes, and that protein function depends on the amino acid sequence and the shape it takes as a consequence of the interactions between those amino acids.
184.108.40.206.3 Describe how viruses, prokaryotic cells and eukaryotic cells differ in relative size, complexity and general structure.
220.127.116.11.4 Explain the function and importance of cell organelles for prokaryotic and/or eukaryotic cells as related to the basic cell processes of respiration, photosynthesis, protein synthesis and cell reproduction. (Protein synthesis is addressed in 18.104.22.168.3; Respiration and photosyntheis addressed in 22.214.171.124.1 Interrelationships)
126.96.36.199.5 Compare and contrast passive transport (including osmosis and facilitated transport) with active transport, such as endocytosis and exocytosis. Addressed in Standard 188.8.131.52.1 homeostatsis.
184.108.40.206.6 Explain the process of mitosis in the formation of identical new cells and maintaining chromosome number during asexual reproduction.
Cells have particular structures that underlie their functions. Every cell is surrounded by a membrane that separates it from the outside world.
Most cell functions involve chemical reactions....
Breakdown and synthesis are made possible by a large set of protein catalysts called enzymes.
AAAS Atlas: See Benchmarks below
5C1: Every cell is covered by a membrane that controls what can enter and leave the cell.
5C1: In all but quiet primitive cells, a complex network of proteins provided organization and shape and for animal cells, movement.
5C2: Within the cells are specialized parts of the transport of material, energy capture and release, protein building, waste disposal, passing information and even movement.
5C3: the work of the cell is carried out by the many different types of molecules it assembles, mostly proteins,
5C4: The genetic information encoded in DNA molecules provides instruction for assembling protein molecules.
5C5: Complex interactions among the different kinds of molecules in the cell cause distinct cycles of activities such as growth and division. Cell behavior can also be affect by molecules from other parts of the organism or even other organisms.
Framework for K-12 Science Education
Systems of specialized cells within organisms help them perform the essential functions of life, which involve chemical reactions that take place between different types of molecules, such as water, proteins, carbohydrates, lipids, and nucleic acids. All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells. Multicellular organisms have a hierarchical structural organization, in which any one system is made up of numerous parts and is itself a component of the next level. Feedback mechanisms maintain a living system’s internal conditions within certain limits and mediate behaviors, allowing it to remain alive and functional even as external conditions change within some range. Outside that range (e.g., at a too high or too low external temperature, with too little food or water available), the organism cannot survive. Feedback mechanisms can encourage (through positive feedback) or discourage (negative feedback) what is going on inside the living system. 12LS1.A
In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. As successive subdivisions of an embryo’s cells occur, programmed genetic instructions and small differences in their immediate environments activate or inactivate different genes, which cause the cells to develop differently—a process called differentiation. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism. In sexual reproduction, a specialized type of cell division called meiosis occurs that results in the production of sex cells, such as gametes in animals (sperm and eggs), which contain only one member from each chromosome pair in the parent cell. 12LS1.B
Common Core Standards
Math standards can be easily incorporated into this topic.
Math 220.127.116.11 Make reasonable estimates and judgments about the accuracy of values resulting from calculations involving measurements.
Students can calculate the mass verses volume ratios they determine the speed of diffusion in the blue agar cells.
Math 18.104.22.168. Design simple experiments and explain the impact of sampling methods, bias and the phrasing of questions asked during data collection.
A variety of simple experiments can be designed involving cell size, mitotic rates and frequencies and others.
Common Core Language Arts: Students can write a laboratory report in the proper form and using their knowledge of technical writing skills. Common core standards addressed:
RST.9-10.1. Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions.
RST.9-10.2. Determine the central ideas or conclusions of a text; trace the text's explanation or depiction of a complex process, phenomenon, or concept; provide an accurate summary of the text.
RST.9-10.3. Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks, attending to special cases or exceptions defined in the text.
Students find it easier to understand that cells are the basic unit of structure (which they can observe) but have a harder time understanding that the cell is the basic unit of function (which has to be inferred from experiments) - Atlas Vol 1 pg 72
Many students express the belief that amino acids are produced by genetic translation (protein synthesis). The evidence suggests that at least four underlying factors contribute to error occurrence: (1) strong word association between the terms "amino acids" and "proteins", (2) confusion resulting from familiar and unfamiliar levels of generality and specificity, (3) conflict resulting from the dual roles of some proteins as participants in and products of translation, and (4) lack of knowledge about the actual origins of amino acids in cells. Implications for teaching are discussed. See this page.
Mrs. T. starts class by having students write down their favorite fast food meal.The students excitedly discuss where they like to eat and what they like to eat there. Then students search the Internet for the nutritional values of each of the food items. Most of the information is found on the restaurants website. Students are instructed to find the grams/calories of proteins, carbohydrates, and fats in the meal. They must calculate the percent of the calories that come from fat, protein, and carbohydrates. The students then list the foods they have eaten and determine the primary cellular function of each particular type of food biochemical. They determine, given recommended daily allowances for each food type, whether they are eating a healthy diet. They analyze and evaluate their favorite meal in their journals as they determine it's nutritional meal. "Are there better choices?" "Can the meal be modified in any way to make it healthier?" "What is missing and how can this affect cellular functions?" "Is there too much of anything? Students share their findings and discuss the consequences and/or benefits of eating that particular meal for every meal. he are particular conscious of the needs of individual cells for each of these biochemicals and discuss possible health effects of incomplete or unbalanced combinations of proteins, carbohydrates and fats.
Suggested Labs and Activities
22.214.171.124.1 Biochemical Properties.
Simple chemical laboratories exploring the biochemistry of foods and their relation to the needs of the cells as well as the cellular source of the foods can be very successful teaching tools. Students learn how to identify carbohydrates, protein and lipids and then determine which unknown is given to them in a test-tube. In the process of doing this they are able to explore common food items and discuss the source and use of the chemical in them. Samples of Tests used include:: carbohydrates - Benedicts solution detects monosaccharides by turning orange after heating; polysaccharides turn black in iodine; proteins turn yellow in nitric acid (or purple in Biuret's solution) and lipids dissolve in lighter fluid but not in water.
126.96.36.199.2 Enzymes as functional proteins.
One excellent activity demonstrating enzyme function is quite simple and yet very graphic. A starch solution is made. Students put about 5 ml of the solution in 2 test-tubes and then test one with Benedicts' solution and one with iodine. The tests will indicate that only starch is found in the tube. Then students take two more tubes of starch and spit into them. Wait 5 minutes and retest. Now the solution in the test tube tests positive with Benedicts solution indicating the presence of glucose. In order to expand this activity and demonstrate that denaturation of proteins involving a shape change decreases activity, the experiment can be repeated but this time, the spit (amylase) is boiled for 1 minute before it is added to the start solution. A discussion then ensues concerning how the glucose got into the test tube, where it came from and what the spit (and amylase) did to the starch. Following denaturation, the activity should be little to none. Students can discuss what this means on a biochemical level as the protein denatures and undergoes a shape change rendering it ineffective. Note: It is important to test the student spit for glucose with Benedicts solution as a control in this experiment since the presence of sugar in the mouth may skew the results.
188.8.131.52.3 and 184.108.40.206.4 Giant Cell
One interesting way to learn about the functions of the various organelles in a cell is to create a cell (to scale) using a large plastic cell membrane (drop cloths duct taped together can be inflated with a fan). Students enter the cell and bring with them a cell organelle that they have built (to scale with the membrane). Students then report on the function and use of the organelle in the cell while sitting in the cell. To contrast the size of prokaryotic cells and viruses, models can be built to scale much like the organelles are. (The virus will be very small and the prokaryotic cell "bacteria" will be about the size of the mitochondria). This would be a nice time to discuss the endosymbiotic theory of mitochondrial origin (See Gifted and talented).
220.127.116.11.4 and 18.104.22.168.5 Why Cells have to be Small
In this activity, an indicator (bromothymol blue) is added to non-nutrient agar which is poured into a cake pan. The students cut the agar into various sizes and then place them into a beaker filled with vinegar or very weak HCl. They record the time it takes for the agar to turn yellow and then compute the surface area to volume ratio of the various agar "cells". A discussion then ensues on how this can be applied to cells (prokaryotic and eukaryotic), how important molecules are moved around cells and the role of diffusion in cellular reactions.
22.214.171.124.5 Amoeba Activity
A culture of Amoeba provide an excellent way for student to observe endocytosis and exocytosis. No staining is necessary. A live cultures of amoeba in a wet mount and a good microscope with a working diaphragm is all that are needed. (Note: Do the activity as soon as possible after receiving the culture, take samples from the very bottom of the culture vessel and use the diaphragm to regulate the light so they can be seen clearly.) A video "Flex cam" mounted on a microscope can make a very nice demonstration activity of this phenomenon. To increase the inquiry appeal of this project, various food components can be included on the slide to see how the amoeba reacts to them. These may be stained with a stain to predict the digestion within the amoeba and follow the endocytosis, vacuoles and exocytosis involved.
126.96.36.199.6 Magnetic Chromosomes and Onion Root Tip
A good system for teaching mitosis is a "pop" bead system with magnets attached. The bead come in a variety of colors and the magnets in the middle act as centromeres in the process of DNA synthesis in interphase. The beads can be easily manipulated as each mitotic phase is simulated and individual chromosomes are color coded so they can be followed through the process. This concept can be very abstract and unless students are able to manipulate the chromosomes themselves it can be difficult to mentally visualize the process.
Another outstanding activity is the use of prepared slides with onion root tip. Students are asked to count the number of cells in interphase, prophase, metaphase, anaphase and telophase. Although these phases are not the focus of the standard, they do help to clarify the process as students struggle to understand the chromosome content of the cells. Through this process, (and with some practice and guidance in identification of the phases) students are able to determine the relative amount of time that a cell spends in each phase. The comparison can then be made to cancer cells. (cross reference for 188.8.131.52.5) In the case of cancer cells, the cell spends a much smaller time in interphase and consequently reproduces much more quickly with less chromosome integrity and a higher probability of mutation. A discussion can then take place concerning the importance of interphase and DNA synthesis and the detrimental effects on the cell when these processes are shortened.
Modeling: Models of cells can help student visualize the relative sizes of various structures and type of cells. Bead models of chromosomes can be infinitely effective in making abstract concepts a little more concrete and easy to visualize.
Inquiry: (Amoeba Activity and others). Through the use of inquiry based learning students are able to explore and construct learning themselves. This is a very authentic method of learning and also cross references well with NSE standard 184.108.40.206.1.
Microscopy with back-up camera to ensure students are viewing the correct structures. A Flex Cam can be very useful as a way of teaching microscopy and ensuring that students are viewing the correct structure. This can be done by the teacher for the whole class or by the student with the teacher looking on. The camera is mounted on the microscope and is easily removed. Using digital photography allows the filming of cells, protists etc, to be used at a later time or for lab tests. The images can be saved on a computer/CD.
Graphic Organizers: Can be very useful as students compare and contrast eukaryotic, prokaryotic and viral organisms.
Demonstration: 220.127.116.11.1 Demonstration of a jello mixture with fresh pineapple and another mixture with canned pineapple. Over several days, students make observations and journal about the differences in jello consistency.
- protein synthesis - the process of assembling amino acids at the ribosome using the sequence coded for by a messenger RNA molecule.
- enzymes - a catalyst used in living organisms and made of proteins. Causes a chemical reaction to occur more rapidly and at a lower temperature. Decreases the activation energy.
- carbohydrate - a molecule made of Carbon, Hydrogen and Oxygen which is used for energy. Examples include glucose (monosaccharide), sucrose (disaccharide) and starch (polysaccharide).
- protein - Amino acids strung together by peptide bonds are a protein. They work based on "Shape" and therefore can be denatured by heat, acidity change or anything else that modifies the shape. Proteins are the basic building blocks of life.
- amino acid - a molecule composed of primarily of Carbon, Hydrogen, Oxygen and Nitrogen. A string of amino acids is a protein. There are 20 amino acids in nature. The type and order of the amino acids are the foundation of different proteins.
- lipid - composed of Carbon, Hydrogen and Oxygen. These atoms are assembled into glycerol and three fatty acids. Lipids are used in life for long term energy storage.
- nucleic acid - composed of Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus. Nucleic acids include DNA and RNA. They are used in the cell as the "directions" which code for the production of proteins.
- mitochondria - a cell part which transforms energy to a usable form for the cell..
- chloroplast - a cell part which converts light energy to chemical energy.
- ribosome - a cellular organelle responsible for the assembly of proteins. The site of translation in protein synthesis.
- nucleus - Contains the DNA of the cell and is the site of DNA replication and the site of transcription in protein synthesis.
- cell membrane (eukaryotic and prokaryotic) - cytoplasmic barrier
- nuclear membrane (eukaryotic) - nuclear barrier
- cell wall - Outer part of the cell which function in shape and as a cytoplasmic divider.
- Diffusion: The process of molecules moving from areas of high concentration to areas of low concentration.
- Osmosis: The movement of water molecules through a membrane from areas of high water concentration to areas of low water concentration.
- Facilitated (diffusion) transport: The process of moving from areas of high concentration to areas of low concentration through a protein in the cell membrane. Requires no energy as it is passive but since it moves through a protein "door" it can become "saturated".
- prokaryotic - examples are bacteria and blue green algae. These cells have no membrane bound organelles. Therefore instead of a nucleus , they have a nucleoid or naked circular DNA.
- eukaryotic - these organisms include plants cells, animal cells, fungi and protists. They have membrane bound organelles (cell parts).
Flex Cam - Available from "The Scope Shoppe" and other vendors works well to assure that students can see the organisms and structures on microscope slides.
Cell Size lab with Vernier probes can be used to measure the rate of diffusion in different size agar cubes simulating different cell sizes.
18.104.22.168.3 Connection to math by showing students the relative sizes of eukaryotic and prokaryotic cells with manipulative' or just drawings.
Assessment of Students
Include questions designed to probe student understanding of concepts, both formative and summative. Identify taxonomic level of questions.
Before looking at single celled organisms a drop of pond water through a microscope students discuss/write what they would see if they had a more powerful microscopes. How does the insides of the single celled organisms compare to inside of animals.
22.214.171.124.3 Summative Assessment - students draw venn diagram (or other graphic organizer) to compare viruses, prokaryotic and eukaryotic cells.
126.96.36.199.4 Formative Assessment Matching index cards with pictures, cell parts, and function for mitochondria, chloroplast, and nucleus
Assessment of Teachers
1. Explain how the food we eat is converted into molecules our body needs.
POSSIBLE ANSWER: Begin with digestion of fats, proteins and carbohydrates. Mention the enzymes pepsin, amylase, bile etc. Then mention absorption by the digestive system, transport in the blood to the cells responsible for production. Then the further use of either protein synthesis directly, using DNA and RNA templates (transcription and translation) or protein synthesis indirectly in the production of enzymes which produce fats and carbohydrates.
2. If our body makes molecules such as starch and fat which are not proteins, how do you explain that since you know that DNA only codes for protein?
ANSWER: DNA codes for proteins; enzymes are proteins; enzymes catalyze the reactions needed to make the other molecules.
3. How is a eukaryotic cell able to carry out cellular chemical reactions which depend on the diffusion of molecules when it is so large in relation to a prokaryotic cell which is so small. How are eukaryotic cells able carry out metabolic functions and chemical reactions efficiently?
ANSWER: Eukaryotic cells have membrane bound organelles. The reactions are carried out in these "compartments" therefore decreasing the volume in which the diffusion needs to take place. In addition, many of the enzymes are attached to the surfaces of membranes and also work in enzyme complexes (many related enzymes together) to increase the efficiency of the chemical reactions of life.
Struggling and At-Risk
Memorization or cell parts and functions can be particularly difficult. These seems to correlate with difficult life experiences and emotional upheaval. Repetition is important in this area but not to the point of boredom. Cell parts can be studied in a variety of ways through art; coloring cells, creating cells with styrofoam and plastic bags. Games such as jeopardy are also helpful and seem to be well received. Experience suggests repeated exposure, practice, and formative assessments such as quizzes will help the inevitable memorization portion of this standard.
Although Struggling and At-Risk students may appear similar to Special education students in their needs, the underlying cause of the problem is radically different. These students may need more individual support and guidance. Humor, stories and personal anecdotes work well. For these students, the turmoil of their daily lives is often more important than learning. Therefore teachers must very clearly state the reason for the lessons and connect them to real life situations as frequently as possible.
Vocabulary may be difficult, especially with words that have similar prefixes (eg. chromosome, chromatid, chromatin etc). A word wall is a way to keep students thinking about the vocabulary and comparing the definitions side by side.
Students research the roles of saturated and unsaturated lipids in nutrition and health. Share their recommendations for healthy amounts and types of fats.
188.8.131.52.5 Advanced students may also have the opportunity to pursue the process of a deeper level of cell division as they look at diseases. Students research different types of cancer and include the connection to cell division and cancer.
Students research the roles of saturated and unsaturated lipids in nutrition and health. Share their recommendations for healthy amounts and types of fats.
Advanced students may also have the opportunity to pursue the process of a deeper level as they look at diseases. For example, cancer, essentially a disease of mitosis, can be explored in a variety of different tumor cells. Data can be obtained and compared and possible mitotic mechanisms can be inferred.
Analogies can be difficult as these students often have different life experiences than the American born students. One way to overcome this is to provide the experience first (activities, inquiry learning, laboratories etc) and then refer back to those common experiences in teaching the concepts.
184.108.40.206.3 Make comparisons of objects to give students an idea of the different sizes of viruses, prokaryotic and eukaryotic cells. Memorization of some cell parts and functions as well as processes such as transcription and translation can be particularly difficult. Repetition is important in this area but not to the point of boredom. Cell parts can be studied in a variety of ways through art; coloring cells, creating cells with styrofoam and plastic bags. Games such as jeopardy are also encouraged. Experience suggests repeated exposure, practice, and formative assessments such as quizzes will help but vary the delivery to decrease boredom and loss of interest.
220.127.116.11.3 & 18.104.22.168.4 Students can build models of a eukarotyic cell.
22.214.171.124.5 Using a badminton net, have students throw things through the holes. Discuss why some objects (big objects )can't get through the holes while other (smaller) objects can get through.
Another way to explain concentration gradient and diffusion, use a marble rolling down a slide and to explain active transport, use a marble rolling up a slide.
126.96.36.199.6 Give the students pieces of paper explaining each step. Have the students place the papers in order of a flow map for the steps of protein synthesis. This is also an excellent strategy for the stages of mitosis.
When walking into a room, school administrators should see a wide variety of hands-on inquiry based experimentation. Students may be testing foods to see if they are made of carbohydrate, lipid or protein. They may be peering into a microscope as they observe the real life workings of an amoeba as they offer it a variety of substances to eat. They should always be engaged and active and discussing their observations between themselves and with the teacher although there may also be occasion for lecture followed by a good discussion.
Food laboratories are particularly interesting for students to share with parents. At meal time students can check out the labels on their food and discuss the content of fat, protein and carbohydrate. (188.8.131.52.1) In this food conscience society, parents may find this interesting and will add their knowledge and sometimes misconceptions. Students can then research them and discuss what they find at home and in class.
Several popular diet claims and plans can be explored. The nutritional strategy of these diets can be analyzed and compared to recommended daily allowances.
Discussions of family history such as diseases like cancer can be very informative as this is essentially a disease of cellular replication (184.108.40.206.6). A discussion about family experiences and therapies can be quite informative. Students can then go on to hypothesize how a chemotherapeutic agent works and what differences can be taken advantage of between cancer and normal cells.