(1) Teachers should build from this in middle school and begin to ask students why they think they are important to be part of diet.
(2) There is very little research on middle school students understanding of proteins or structure of biological molecules. These intermediate understanding also require that middle school students develop an atomic model of matter by the end of middle school; it does not have be an advanced model, but it is hypothesized that students need to relate and distinguish the difference between an atom and a molecule and must realize all substances are composed of atoms and molecules—whether they are living or not.
(3) LIMIT: No detailed structures are expected to be understood or memorized. By high school should understand that proteins are basically a string of folded amino acids.
Ravit Duncan has evidence that middle school students can achieve some of the basic understanding of proteins described here.
(4) LIMIT: without much detail in description.
(5) LIMIT: But knowledge of this process is at a very limited level.
(6) So that they can realize can be broken down or built up from carbon atoms.
(7) LIMIT: Students should NOT be asked to memorize any structure in detail they should be able to recognize or describe the basic repeating units in these different types of molecules and understand the big conceptual ideas about these molecules’ structure and function.
(8) There is no evidence that this memorization of structure is helpful or beneficial. Any expectations for understandings about structure require prerequisite understanding of chemistry- students must certainly be able to distinguish the difference between and an atom and a molecule. If structural understands are to be focused on, it is better to focus on the fact that proteins are comprised of smaller carbon-based subunits, amino acids, that are chained together, and that nucleic acids are also comprised of smaller units that are carbon based, nucleotides, that are carbon based. Finally lipids are comprised of long chain of carbon atoms. All have properties and structures that are key to their function in cells. If student understand these larger molecules are comprised of smaller molecules they can understand the results and events in metabolism better and if this is applied to proteins they can better understand how genes influence protein structure. Even though understanding the structure of DNA is critical to understanding how it is replicated and how genes are expressed at a molecular level, students likely do not have to know these molecular mechanisms for an introductory biology class.
(9) LIMIT: We are not suggesting students memorized detailed molecular structures and properties, but instead understand a few basic chemical principles about biological molecules and how they relate to their critical functions inside of cells. This is an elaboration of the existing idea about structures and functions. Both Ravit Duncan and Aaron Rogat have evidence that high school student can learn these ideas in introductory biology in high school.
(10) They likely will not think of proteins as carrying out work inside of cells. But the teacher may be able to build from this understanding as a necessity of many living things.
(11) Pre-requisite knowledge: If breaking down food substances such as sugars are considered as exemplar work that proteins carry out, students must understand what chemical reactions are at a molecular level (e.g. that they are a rearrangement of atoms to form new molecules making up substances [the LP proposed by Smith et al. 2006 for the atomic molecular theory targets this understanding by the end of middle school]). Also, note that this idea also should connect to the digestion ideas in anatomy & physiology.
(12) Can expand later in high school.
(13) LIMIT: At this point the term enzyme does not have to be introduced, but the function of the chemical break-down of food substances inside of cells is a useful intermediate understanding for students to develop – later in high school such molecular events can be associated with enzymes.
(14) This is noted as a potential misconception as there is no research citing this problem, mainly because middle school curriculum generally does not focus on proteins carrying out work inside of cells. This is a predicted problem for students.
(15) In order to develop this idea, it is hypothesized that it is important for students to realize that chemical reactions take place in living organisms and that many biological activities are chemical reactions (e.g. breaking down food into small molecules, assembling biological molecules). Students must have an atomic molecular model for matter and understand that chemical reactions involve a rearrangement of atoms to form new substances with no atoms created or destroyed in the process.
(16) Proteins are not the only cellular molecules that carry out work in cells. Much research has pointed out the importance of RNA molecules in influencing cellular behavior and function, many of which act as an enzyme. However, the vast majority of research on the cellular functions of cells over the last 50-60 years has focused on the role of proteins. Thus understanding protein function is critical to developing a modern scientific view of how cells function.
(17) It is very important to connect ideas about protein structure and function with the genetics strand on regarding ideas that target DNA and gene function. Refer to genetics strand for details about protein structure and function.
(18) Prediction-type learning performances are particularly effective to demonstrate students' level of understanding of this idea (e.g., if a critical structure of the enzyme is changed, predict what will happen to its function).
(19) This anatomical understanding of how multi-cellular organisms are structured is a fundamental understanding and is key to understanding how and why changes in cell function affect structures and functions at higher levels of organization.
(20) In this way students can begin to understand why glucose production is important to produce in plants and why photosynthesis is so important and special.
(21) LIMIT: Explain this as a transformation of energy from one type of chemical energy to another – but do not have to talk about ATP.
(22) Cellular respiration has to be linked to digestive and circulatory systems in anatomy & physiology so students understand where the sugar came from and how it is transported to cells all over the body.
(23) It might be best to identify what is needed for growth in elementary school, but wait until students have some molecular understanding of substances at the end of middle school before discussing photosynthesis or cellular respiration in any detail. There is abundant evidence that many students in middle school do not learn even the basics about photosynthesis using a macroscopic view of matter. Some suggest that students cannot develop deep understanding of photosynthetic processes with out a decently developed atomic molecular theory (NRC, 2007).
(24) It is hypothesized that students should be able to apply principles of conservation/transformation of energy in middle school to cellular respiration and photosynthesis (or other biological chemical reactions) to understand the importance of ATP at high school. They might also need to understand what bonds are, thus a fairly sophisticated model of matter needs to develop before learning about ATP in any deep way.
(25) These understandings can be described or identified in texts, or using drawings, models, or pictures. These ideas about reproduction are likely in anatomy & physiology or genetics progressions, but they are a prerequisite to understanding meiosis and mitosis in plants and animals.
(26) When describing and thinking about multi-cellular organisms be able to move between the cellular, tissue, and organ levels proficiently.
(27) This idea helps to support elaborate the ideas that some functions are carried out by all cells, but some functions are unique to some cells, this idea can also provide more opportunities to explore the role of protein in cell function and how they support cell function. [This idea should also be linked to the anatomy strand]
(28) This performance is looking for the presence of multiple connected cells in students’ drawings of these different tissues; they do not have to be accurate—just looking for the general understanding.
(29) It is critical for students to understand and apply conservation of matter here to both photosynthesis and cellular respiration (C. Anderson, personal communication).
(30) Only include this if you think student have the chemistry understanding to understand this as well the role of energy in rearranging molecules. Understanding of energy transformations and conservation of energy is also important here. Without these understandings, students will have a very limited understanding of this concept.
(31) LIMIT: Students would not need to know detailed descriptions of the molecular mechanisms involved in generating ATP would be required however.
(32) LIMIT: Students do not need to memorize the every detailed step. Such memorization is likely to cause students to miss the big picture about the purpose and end results of this mitosis. The same goes for meiosis.
(33) Not much here in the research.
(34) LIMIT: At middle school should focus on only a few sub-cellular structures and then add a few more structure in high school. I do not know of any evidence that focusing on all the cell parts in middle school (or even high school) help student understand how cell work or function. ER and Golgi are important, but if students have no understanding of proteins it is a waste of time. However, focusing on the nucleus as a storage place for DNA and the mitochondrion as a place to break down glucose and extract energy for cell use—along with the cell membrane as a structure for regulating the flow or substance in and out of a cell, might all be appreciated -- even by middle school students. Ultimately, even if proteins are understood by students as suggested above, I would still question the importance of talking about the Golgi and ER. Ribosomes are okay, because they are structures for building proteins, so this understanding supports one of the basic functions of life that cells must carry out.
(35) Focus on plant and animal cells – and perhaps protists like paramecium.
(36) LIMIT: No need to understand details of this replication at this time.
(37) LIMIT: May include cilia or flagella but only if it supports understanding of another idea like the role of proteins in carrying out the work of cells.
(38) This is a unique way to get at structure function relationships without it being a memorization game which is less informative about student understanding.
(39) The main point here is that viruses can use DNA or RNA as a code to generate more copies, however a virus is much, much smaller than a cell and it is not a cell. In terms of reproduction students must realize viruses are not self-sufficient and depend on a host cell to replicate while cells are self-sufficient and can reproduce on their own.
Authors and Reviewers
Dr. Aaron Rogat, Teachers College, Columbia University and the Consortium for Policy Research in Education (CPRE), New York (author)
Barbara C. Buckley, WestEd, California (reviewer)
American Association for the Advancement of Science (AAAS). (1993). Benchmarks for Science Literacy. Oxford University Press: New York.
Anderson, C. (n.d.). Personal communication.
Consortium for Policy Research in Education (CPRE). (2008). Pedagogical Content Knowledge Tools (PCK Tools). Cells and Organisms. University of Pennsylvania: Consortium for Policy Research in Education.
Driver, R., Squires, A., Rushworth, P., & Wood-Robinson, V. (1994). Making sense of secondary science: Research into children’s ideas. London and New York: Routledge.
Duncan, R. (n.d.). Personal communication.
National Research Council (NRC). (2007). Taking Science To School: Learning and Teaching Science in Grades K-8. Eds. Duschl, R, Shweingruber, H. and Shouse, A. National Academy Press: Washington DC.
Rogat, A. (n.d.), Unpublished data.
Smith, C. L., Wiser, M., Anderson, C. W., & Krajcik, J. (2006). Implications of research on children’s learning for standards and assessment: A proposed learning progression for matter and atomic-molecular theory. Measurement: Interdisciplinary Research and Perspectives, 14(1-2), 1-98.
Concept and Skill Progression forGenetics Three models are represented within each grade span: 1) classical model of genetics; 2) cellular processes related to reproduction; and 3) the molecular aspects of genetics. Additionally, the progression addresses five core ideas: 1) organization, location and function of DNA and genes; 2) relationships between genes, nuclear division, and passage of genetic information; 3) effects of DNA mutations and variation; 4) gene variation and implications for phenotypic variation; and 5) transmission of genetic information and patterns of inheritance. Core ideas 1 and 3 have specific relevance to molecular mechanisms, idea 2 relates specifically to cellular mechanisms, and ideas 4 and 5 relate to classical genetics; these all eventually need be coordinated.
Before instruction students typically have a theory of inherited kinship; with this they can distinguish some inherited characteristics verses socially determined characteristics. They are, however, likely to believe that daughters get their characteristics from mothers, and likewise sons from fathers. Students can identify some critical aspects of organisms required for living, including the ability to reproduce. Students are also likely to understand that all living things share some of these things in common, as well as physical attributes. They are unlikely, however, to attribute those to any common mechanism such as DNA or genes, even though they are likely to have heard about genes and DNA.
Conceptual Stepping Stones1
Elementary school students understand that siblings do not always look identical to each other or their parents, but have a combination of characteristics from their parents. They can apply this to people, animals, and even reptiles or insects. They may, however, believe that plants are not living and therefore do not have genes. Students can identify critical aspects of organisms needed to live, and know that genes somewhere inside living organisms provide information about an organism’s development. Students can explain that “information” in genes about how organisms look provide are passed on from one generation to another. They do not, however, understand how this works.
Early middle school students understand that genes are linked to a theory of kinship. They know that traits are physical characteristics of organisms that are influenced by genes (e.g. “a gene for eye color" is not actually an eye color, but has information about eye color). Students understand that mutations are changes in genetic information that can confer “different” traits or functions. Students may associate reproduction with copulation and may believe it only occurs in animals. Students are able to explain that genes are inside cells, but may believe they are in only a few cell types. Students understand that genes provide information about the development of traits or cellular entities, but likely believe genes are active “particles.”
Late middle school students understand the mechanism of how traits are passed between generations and relate kinship to genes. Students understand that genes are found in cells of all organisms and associate genes with chromosomes. They can explain that chromosomes carry genetic information from generation to generation during cell division. Students understand that for each trait we have two version of the gene (alleles). They understand that duplication of chromosomes occurs before cell division to maintain an equal amount of genetic information. They know there are two types of cell division: mitosis and meiosis, but may not properly connect these to specific cell types. Students realize egg and sperm fuse in sexual reproduction to produce a new cell that goes on to develop as the offspring. Students understand the role of genes in transmission of information and in influencing proteins and cell function. They understand that a mutation in genes can result in a change in proteins or cell function.
Culminating Scientific Ideas2
High School students understand the relationship of genes to phenotypes. Students can explain how events during cell division are important in explaining why we see certain gene combinations in predictable patterns. They understand only one copy of a trait needs to be present to show a dominant phenotype or both copies present to show a recessive phenotype. They can predict possible combinations of alleles (and potential phenotypes) for the progeny of two parents with a given set of alleles. Students can relate DNA duplication and nuclear division to the passage of DNA and consequently inherited traits. They understand that there are two types of division that cells can undergo (mitosis and meioses) and that these occur in different cell types and result in different end products in terms of the number of chromosomes or genes produced. Students recognize that all organisms have DNA and genes. Students can explain the role and function of genes in living organisms. They can relate and distinguish between chromosomes, genes, DNA, and nucleotides in animal and plant cells. They understand the order of nucleotides in a gene determine the structure of a protein, and consequently the function of a protein in cells. Students can explain how a mutation in a gene can affect the structure, function, or behavior of a cell or an organism by influencing the structure or function of proteins.