I. Chemical elements that make up an organism
Question 1: What are the chemical elements that make up an organism?
Case 1: According to the research of scientists, organisms contain many chemical elements. Please analyze the chemical elements that make up the organism according to the Comparison Table of Chemical Elements between Corn and Human Body (see extended data).
Description: design a question string to guide students to analyze the chemical elements that make up an organism according to the case.
What are the chemical elements that make up an organism? Is it the same as the non-biological world?
Are the chemical elements that make up an organism the same?
Which chemical elements are high in organisms? Which ones are very low?
Finally, it is summarized as follows:
1, basic elements: carbon, hydrogen, oxygen and nitrogen.
C is the most basic element.
2, a large number of elements: more than one in ten thousand.
Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, potassium, calcium, magnesium, etc.
3. Trace elements: essential and rare.
? Manganese, boron, zinc, copper, molybdenum, chlorine, etc.
Second, the important role of chemical elements that make up organisms.
Question 2: What are the important functions of chemical elements that make up organisms?
Note: After teachers ask questions, they can guide students to understand the physiological functions of chemical elements or read teaching material analysis by introducing specific examples. Summarized as follows:
1 constitutes compounds and protoplasm as the material basis of life activities.
Carbon, hydrogen, oxygen, nitrogen and phosphorus account for 97%.
2, affect the life activities of organisms.
For example, B promotes pollen germination and pollen tube elongation.
Molybdenum is an essential trace element for pasture growth (New Zealand grassland and molybdenum mine).
Third, the unity and difference between living and non-living worlds.
Case 2: Please compare the elements contained in biology and lithosphere, and see what conclusion can be drawn?
Average protoplasm content
Human body content
Lithospheric content
Carbon, hydrogen and oxygen.
93%
74%
Less than 1%
Description: Teachers guide students to analyze and summarize the unity and differences between biological and abiotic worlds.
1, unity: life elements can be found in nature.
2. Difference: The content of life elements is different between living things and non-living things.
Outline of blackboard writing
Chapter I Material Basis of Life
Section 1 chemical elements that make up organisms
I. Chemical elements that make up an organism
1. Basic elements: carbon, hydrogen, oxygen and nitrogen.
2. Macroelements: carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, potassium, calcium, magnesium, etc.
3. Trace elements: iron, manganese, boron, zinc, copper, molybdenum, chlorine, etc.
Second, the important role of chemical elements that make up organisms.
1. Constitute compounds and protoplasm as the material basis of life activities.
2. Affect the life activities of organisms.
Third, the unity and difference between living and non-living worlds.
1. Unity: Life elements are not special.
2. difference: the content is different.
Compounds that make up an organism
Question 1: In what form do the chemical elements that make up an organism exist in an organism?
Description: The teacher guides the students to analyze the chemical elements that make up the organism in what form (simple substance or combined state) exists in the body, and combines the compounds that the students know about the organism to analyze and summarize the compounds that make up the cells.
I. compounds that make up cells
Inorganic compound: water: 80-90%
Inorganic salt: 1- 1.5%
Organic compound: protein: 7- 10%.
nucleic acid
Sugar: 1- 1.5%
Lipids: 1-2%
Second, water.
Question 2: Water is very important to living things. What is the physiological effect of water on organisms and cells? How is this role reflected?
Description: To guide students to analyze water-related knowledge from the physiological function and existing form of water, we should not only inspire students to analyze by introducing examples, but also encourage students to analyze water-related knowledge by giving examples themselves. The summary is as follows:
1, content: max
(1) The content of different organisms is different: jellyfish 97%, soybean 60%.
(2) Different structures have different contents: 22% in bone, 76% in muscle and 86% in brain.
(3) Different growth stages have different contents: 72% for infants, 60% for adults and 50% for the elderly.
2, the form of existence:
(1) bound water (4,5%): bound to other substances in the cell.
(2) Free water (94,5%): it exists in a free form and can flow freely.
Such as: seed drying (water is free water)
3. Physiological function: Water is the source of life.
(1) Composition of nuclear organisms
(2) A good solvent is beneficial to the chemical reaction in vivo.
(3) Conducive to the transport of intracellular substances
Third, inorganic salts.
Question 3: In what form do inorganic salts exist in organisms? What effects do inorganic salts have on cells and organisms? How do these physiological functions work?
Description: To guide students to analyze the relevant knowledge of inorganic salts from the aspects of their existing forms and physiological functions, we should not only inspire students to analyze by introducing examples (see the summary below), but also encourage students to analyze by examples themselves. The summary is as follows:
1, content: rarely.
2. Form of existence: ionic state
3. Physiological function
(1) is an important component of some complex compounds in cells.
Magnesium ion: chlorophyll; Iron ion: hemoglobin
(2) Life-sustaining activities
Calcium ion: activate prothrombin, and convulsion occurs when it is lacking.
(3) maintaining cell osmotic pressure and acid-base balance
Normal saline: to ensure the normal osmotic balance of cells.
Fourth, sugar.
Question 4: What do you know about sugar? What are the common characteristics of these sugars? What physiological effects do they have on cells and organisms?
Description: Guide students to analyze the classification of sugar from their own perception, and then guide students to analyze the elemental composition and physiological functions of sugar in the process of analyzing the common characteristics of sugar. Teachers will use concrete examples to help students analyze and understand the special physiological functions of sugar (see summary). Finally, it is summarized as follows:
1, component: carbon, hydrogen, oxygen
2. Classification (according to hydrolysis)
(1) Monosaccharide: non-hydrolyzable, pentasaccharide and hexasaccharide.
Glucose: the product of photosynthesis
Important energy substances of cells
Galactose: In milk
(2) disaccharide: two monosaccharides are produced after hydrolysis.
Plant disaccharides: sucrose, maltose
Animal disaccharide: lactose
(3) polysaccharide: various monosaccharides are generated after hydrolysis.
Plant polysaccharides: starch, cellulose
Animal polysaccharide: glycogen (liver glycogen, muscle glycogen)
3. Physiological function
(1) Ribose and deoxyribose are important components of nucleic acid.
(2) The main energy substances of biological life activities.
(3) Sugar is related to the structure of organisms.
Verb (abbreviation for verb) lipid
Question 5: What do you know about lipids? What are the common characteristics of these lipids? What physiological effects do they have on cells and organisms?
Description: Guide students to analyze the classification of lipids from their own perception, and then guide students to analyze the elemental composition and physiological functions of lipids in the process of analyzing their common characteristics. Teachers will use specific examples to help students analyze and understand the special physiological functions of lipids (see summary). Finally, it is summarized as follows:
1, component: carbon, hydrogen, oxygen, (nitrogen, phosphorus)
The ratio of C to H is high, and more energy is released through thorough oxidation.
2. Classification and physiological function
(1) fat: energy storage substance.
Keep body temperature constant, reduce friction and buffer external pressure.
(2) Lipid: phospholipid (the main component of membrane)
Keywords cephalin, lecithin ⅵ, protein,
Question 6: How much do you know about protein? What are the common features of these protein? What important physiological functions do they have for cells and organisms?
Description: Guide students to analyze the element composition and physiological function of protein from their own perception of protein, and on this basis, guide students to analyze the structural basis and structural characteristics of protein's function, and explain the relevant knowledge of protein in detail. Finally, it is summarized as follows:
Protein is called the embodiment of life activities. It is a very important component in various cell structures. It accounts for about 50% of the weight of stem cells, and it is a macromolecular compound or biological macromolecule.
1, with large relative molecular weight.
Thousands to hundreds of thousands of atoms with molecular weights of tens of thousands to millions.
Such as: lactoglobulin 30000 ~ 60000.
2. The molecular structure is very complicated
1, Species Diversity: Diversity in protein.
Analyze the reasons:
(1) The types, quantities and sequences of amino acids are different-the polypeptide chains are diverse.
(2) the spatial structure is diverse
2. Function is very important: the embodiment of all life activities.
(1) Important substances (structural proteins) that constitute cells and organisms;
(2) Some protein have catalysis (enzyme);
(3) Some protein have transport function (carrier protein);
(4) Some protein have regulatory function (hormone protein);
(5) Some protein have immune function (antibody).
Seven, nucleic acid: biological macromolecules
Nucleic acid is an acidic substance, which was originally extracted from the nucleus. Divided into two categories: DNA and RNA.
1, high molecular weight RNADNA
Molecular weight 104 106
Distributed cytoplasmic nucleus
2, the structure is complex
(1) Element composition: carbon, hydrogen, oxygen, nitrogen and phosphorus.
(2) structural unit: nucleotide
Classification: ribonucleotides: 4 species
Deoxynucleotides: four kinds.
(3) chemical structure: polynucleotide chain
(4) Spatial structure: the double helix structure of DNA.
(Note: Chapter 6 explains in detail)
3. Diversity: Every living thing is different.
4. Functional importance: the genetic material of all living things.
(1) controls the heredity and variation of organisms.
(2) Control the biosynthesis of protein.
Transition: Among the six compounds, protein is the embodiment of life activities, and nucleic acid is the regulator of life activities. Both of them are the most important biomacromolecules, while sugar and lipid mainly appear as energy substances and participate in the regulation of some life activities. Water and inorganic salts are auxiliary substances of life activities, and these six compounds together constitute the substance of cells, namely protoplasm.
Eight, protoplasm
Case 1: small experiment-scientists grind live hydra, extract various compounds, then mix them in real proportion and cultivate them in a suitable environment to predict whether they can get live cells. What can this experiment show?
Analysis: Of course not.
Protoplasm exists in living cells.
Protoplasm has a special structure.
Therefore: 1, the main components of protoplasm are protein and nucleic acid;
2. Protoplasm can show life activities (such as self-renewal);
3. Protoplasm differentiates into cytoplasm, cell membrane, nucleus and other structures.
In order to further understand the nature of life, we need to study the structure of cells.
Outline of blackboard writing
Section 2 Compounds that Make Up Organisms
I. compounds that make up cells
Inorganic compounds: water, inorganic salts.
Organic compounds: protein, nucleic acid, sugar, lipid.
Second, water.
1. Content: the highest
(1) The content of different organisms is different: jellyfish 97%, soybean 60%.
(2) Different structures have different contents: 22% in bone, 76% in muscle and 86% in brain.
(3) Different growth stages have different contents: 72% for infants, 60% for adults and 50% for the elderly.
2. Form of existence:
(1) bound water (4,5%): bound to other substances in the cell.
(2) Free water (94,5%): it exists in a free form and can flow freely.
3. Physiological function: Water is the source of life.
(1) Composition of nuclear organisms
(2) A good solvent is beneficial to the chemical reaction in vivo.
(3) Conducive to the transport of intracellular substances
Third, inorganic salts.
1. Content: Very little.
2. Form of existence: ionic state
3. Physiological function
(1) is an important component of some complex compounds in cells.
(2) Life-sustaining activities
(3) maintaining cell osmotic pressure and acid-base balance
Fourth, sugar.
1. Composition: carbon, hydrogen, oxygen
2. Classification (according to hydrolysis)
(1) monosaccharide:
3. Physiological function
(1) Ribose and deoxyribose are important components of nucleic acid.
(2) The main energy substances of biological life activities.
(3) Sugar is related to the structure of organisms.
Verb (abbreviation for verb) lipid
1. Component: carbon, hydrogen, oxygen, nitrogen and phosphorus.
2. Classification and physiological function
(1) Fat: energy storage substance, which can keep body temperature constant, reduce friction and buffer external pressure.
(2) Lipid: phospholipid (the main component of membrane)
Six, protein biological macromolecules
1. The relative molecular weight is large.
2. The molecular structure is very complicated
(4) Spatial structure: protein-one or more polypeptide chains form a spatial structure.
3. Species diversity: the diversity of protein.
Reason: (1) The types, quantities and sequences of amino acids are different-the polypeptide chains are diverse.
Function is very important: the embodiment of all life activities
(1) Important substances (structural proteins) that constitute cells and organisms;
(2) Some protein have catalysis (enzyme);
(3) Some protein have transport function (carrier protein);
(4) Some protein have regulatory function (hormone protein);
(5) Some protein have immune function (antibody).
Seven, nucleic acid-biological macromolecules
DNA and RNA
1. Large molecular weight RNADNA
Molecular weight 104 106
Distributed cytoplasmic nucleus
2. The structure is very complicated
(1) Element composition: carbon, hydrogen, oxygen, nitrogen and phosphorus.
(2) structural unit: nucleotide
(3) chemical structure: polynucleotide chain
(4) Spatial structure: the double helix structure of DNA.
3. Diversity: Every living thing is different.
4. Functional importance: the genetic material of all living things.
(1) controls the heredity and variation of organisms.
(2) Control the biosynthesis of protein.
Eight, protoplasm
1. The main components of protoplasm are protein and nucleic acid;
2. Protoplasm can show life activities (such as self-renewal);
3. Protoplast differentiated into cytoplasm, cell membrane, nucleus and other structures.
Structure and function of key cells in teaching: 1. Study and discuss the life characteristics different from abiotic cells.
2. Selective permeability of cell membrane.
3. Chapter 2 The structure of mitochondria and chloroplasts laid the foundation for respiration and photosynthesis.
4. The structure and function of nucleus laid the foundation for Chapter 5.
Teaching difficulties: 1, the significance of cell volume and relative surface area to cells.
2, the structure and functional characteristics of the cell membrane, understand the fluidity of the membrane.
3. Understand the structure and function of chloroplasts, mitochondria and Golgi apparatus, and understand the relationship between organelles.
4. The dynamic relationship between chromatin and chromosome transformation.
Teaching process:
Q: The virus has two most important components-protein, which embodies life activities, and nucleic acid, a genetic material. But the virus can't live alone, and the virus can only reflect the characteristics of life after invading the host cell. What do the above facts show? Can you analyze the reason?
Summary: Considering from the material basis, the simple composition of virus is not enough to complete complex metabolism; From the structural basis, the virus does not have a cell structure-cell theory points out that the cell is the basic unit of structure and metabolic function. So the virus cannot metabolize independently. Viruses must be parasitic in living cell organisms to reflect life phenomena.
Question: According to junior high school knowledge, what kinds of cell biology can be divided into? What are their main differences in structure? Is there any common basic structure?
The courseware demonstrates several kinds of plant cells, human cells and prokaryotic cells.
Summarize the discussion results.
Part I: Structure and function of cells.
The biological world divides viruses without cell structure into a special world. Organisms with cellular structure are divided into prokaryotes and eukaryotes according to whether cells have nuclei or not.
It is clearly pointed out that high school students mainly study biological problems centered on eukaryotes.
Submicrostructure of eukaryotic cells: (structure observed under electron microscope)
Explain the microstructure and submicrostructure of cells.
Stimulate students' interest in exploring the submicroscopic structure of cells. What did people find under the electron microscope?
The courseware demonstrates the electron microscope photos of cell walls, cell membranes, nuclei, chloroplasts, mitochondria and ribosomes.
Guide students to read pictures: memorize the names of various structures and the morphological and structural characteristics of various structures; Pay attention to the difference between animal cells and plant cells.
The courseware demonstrates the pattern diagrams of animal cells and plant cells, and identifies the submicroscopic structure of cells. Compare the differences between cells and pay attention to error correction. Emphasize the common structure and unique structure of cells, and summarize the matters needing attention.
Question:
1, what's the difference? Will the tissues and cells of plants and animals have the same result when soaked in clear water? Why can plants carry out photosynthesis?
-All plant cells have cell walls; Some cells have chloroplasts or large vacuoles. Both animal cells and lower plant cells have centrosomes.
2. What are the similarities? What does this mean? What are the effects of these basic structures on life? How do these structures reflect the characteristics of life?
Learn the structure and function of each part of the cell respectively. (Emphasis on understanding the meaning of life)
I. Cell membrane
All cells have cell membranes, which shows their importance to life. According to the relative position of cell membrane, it can be inferred that cell membrane has protective effect on cells.
Students discuss: What facts can explain that the cell membrane is alive?
(Please refer to the extension materials for details)
How does cell membrane protect cells? What is the fundamental difference between the structure and composition of cell membrane and general membrane?
Problem discussion: students design experiments;
(1) proved the existence of the membrane. (plasma wall separation; The microprobe feels resistance; Electron microscope observation. )
(2) To study the structure of cell membrane, experimental materials are needed. What kind of biomaterials should we choose? Why? How to make the cell membrane?
Train students to attach importance to evidence and reasons when drawing conclusions or speculating. The basic quality of clear organization when expressing opinions. )
This paper introduces the method of obtaining cell membrane (see extended materials for related contents). Let students understand the thinking of scientists in designing experiments.
(3) How to determine the composition of cell membrane qualitatively and quantitatively?
Observation method: the cell membrane was observed by electron microscope: the thickness of dark, bright and dark three-layer structure was about 75~ 100 angstrom (see extended data).
Experimental methods: Scientists determine the chemical composition of cell membrane through chemical analysis:
Fact 1: The membrane is easily dissolved by lipid solvents. Easily dissolved by protease. (Disappeared after processing. )
Fact 2: Lipids easily cross cell membranes.
Fact 3: Its components can be confirmed by indicators: phospholipid molecules and protein molecules.
For ordinary students, students can be guided to draw conclusions by analyzing the above data, and at the same time understand the ideas and methods of experimental design.
1, ingredient: phospholipid, protein.
2. Structure:
Problem discussion: (Cultivate students' analytical reasoning ability. )
These two substances belong to hydrophilic substances and hydrophobic substances respectively. How should these two substances be arranged?
Structural characteristics of (1) phospholipid molecule: phospholipid molecule is divided into hydrophobic end and hydrophilic end.
What would a layer of molecules look like if they were arranged in a plane? (It does not conform to the fact that there is a water environment inside and outside the cell membrane, which leads to the fact that cells cannot exchange substances normally. If it is two floors, how will it be arranged? Why?
(2) What is the relationship between hydrophilic proteins and phospholipid molecules?
According to the information given above, which layer is lipid, dark layer or bright layer? Which layer is protein substance? Based on what?
Understand the observation that the dark center inside and outside glows.
Due to the limitation of observation technology, scientists' understanding of cell membrane is basically hypothesis and speculation, and understand the difference between theory and hypothesis. In order to express the structural characteristics of cell membrane intuitively, scientists have designed some biological models according to the hypothesis. Among them, it is widely accepted: liquid mosaic model-highlighting liquid structure
(1) bilayer phospholipid molecule-basic skeleton
(2) protein covers, inlays and runs through "bones".
Q: What is the important difference between this structure and the general "membrane"? What effect will the structural characteristics of cell membrane have on its physiological function?
Hydrophilic substances can be close to the membrane, but they can't pass through it at will!
Phospholipid molecules are not connected with each other, and the molecules are always in motion-liquid flow.
One of the two fatty acids in phospholipid molecules is always unsaturated, so the long chain of fatty acids bends at the double bond. When a molecule rotates, it will displace adjacent molecules, which may create an instantaneous gap and create opportunities for the diffusion of substances. (-If there is a concentration difference between the two sides of the membrane, lipid substances with relatively small molecules or not repelled by phospholipid molecules can diffuse. )
The diameter of ions should be relatively small and should be diffused according to the concentration difference. But this is not the case. Why?
Effect of protein on cell membrane:
Protein is an amphoteric compound. Therefore, charged ions do not easily cross the cell membrane. Some ions or small molecular organics outside the cell may interact with some protein on the membrane, resulting in temporary changes of related protein molecules. There will be a temporary "tunnel" or membrane-piercing movement in the protein. As a result, the corresponding ions or small molecules have the opportunity to cross the cell membrane. These protein molecules on the membrane are called carriers.
Physiological function of perianth formed by glycoprotein;
(1) Protection and lubrication function
(2) cell recognition:
Experiment 1: Take a yellow sponge and a red sea sponge from lower multicellular animals. Break up separately and mix well. Let stand and cultivate for a period of time. Results: Cells recombined to form yellow sponge and red sponge. There is no mixed color sponge.
Experiment 2: Immune response of human ABO blood group. (choose to tell)
By learning the functions of protein (such as information transmission between cells; Material exchange and immune response of cells. ), which is helpful for students to understand the distribution characteristics and functions of protein.
Carrier: (protein) A tool distributed on a membrane, which is specially used to transport specific substances.
Student summary: through the above study, summarize the structural characteristics of cell membrane.
Prove that cell membrane has fluidity and the significance of cell membrane fluidity to cells;
(1) The formation and development of paramecium food vacuole.
(2) The formation of pseudopodia when amoeba preys and moves; Leukocyte phagocytosis bacteria; Cystic drinking water and secretion;
(3) Cell membrane fluidity
(4) Cell fusion in the process of cell hybridization
Human-mouse cell hybridization experiment: protein on the fluorescent labeled membrane has a clear boundary with (red and green) cells. After 37℃ 10 minutes, the boundary disappears, and the protein of red and green fluorescent labels is evenly distributed, and no boundary can be seen.
Student summary: What life process can the cell membrane complete by flowing?
It provides a basis for cell absorption, secretion, repair, fusion, movement, predation, deformation and so on. )
3. Characteristics of cell membrane: ① The structural feature is fluid.
② Functional characteristics have selective permeability.
Through learning, let students know the difference between biofilm and general non-biofilm, and understand the life characteristics of biofilm.
Students discuss the relationship between the fluidity of cell membrane and the permeability of functional selection.
4. Ways of various substances passing through the membrane: (Please refer to "Cell ultrastructure". ppt”)
Students discuss biological models:
(1) What happens when a drop of red ink drops into a bowl of water? What kind of physics does it belong to? Principle?
(The condition of free diffusion is that there is a concentration difference between the two solutions. )
Pay attention to correction: emphasize two-way diffusion and summarize the different diffusion speeds.
(2) If there is a semipermeable membrane between two solutions with different concentrations-solvent molecules can pass freely, but solute molecules can't, what is the result of the diffusion of solvent molecules in the solution? (occurs against the direction of concentration)
(3) Can all kinds of nutrients needed by cells penetrate the cell membrane by diffusion? What can't? Why? What types of substances are diffusion limited to?
Summary:
Diffusion belongs to passive transportation. According to whether the carrier is needed to help diffusion, it can be divided into: auxiliary diffusion and free diffusion. Because the diffusion of water molecules is carried out against the concentration difference, the diffusion of water molecules is also called infiltration.
Problem: Diffusion is a passive absorption mode that cells rely on concentration difference. What are its advantages and disadvantages?
How do cells absorb ions and small organic molecules?
Explain the characteristics of active transportation: analogy with similar cases in life. Let students know the characteristics of active traffic.
List the facts of active transportation:
(1) The iodine concentration in kelp cells is 30 times higher than that in seawater; Other algae can even be 2 million times as large as seawater;
(2) The potassium ion in red blood cells is 30 times that in plasma.
(3) The types and proportions of elements absorbed by different plants are different.
Students summarize and fill in the form:
way
Transmission direction
Carrier assistance
energy consumption
forms of matter
free diffusion
infiltration
Assist in proliferation
Active migration
Conclusion: The protective effect of membrane is a kind of biological protection. Once the cell dies, this effect will disappear.
Question:
(1) What is the biological significance of cell membrane protecting cells?
(The intracellular environment is stable and harmful substances are blocked. Ensure the timely supply of raw materials and timely elimination of products to meet the needs of metabolism. )
(2) What are the structural and functional characteristics of cell membranes that are different from those of non-biological membranes?
(structural fluidity, functional selectivity permeability. )
5. Cell endocytosis and exocytosis: the way in which macromolecules that cannot penetrate the cell membrane "enter and leave the cell".
Key point: This substance has never penetrated the cell membrane, and its principle is to use the fluidity of the cell membrane.
6. Function of cell membrane: biological protection.
Cell membrane is closely related to cell material exchange, cell recognition, secretion, excretion and immunity.
There is a cell wall composed of cellulose and pectin secreted by cells outside the plant cell membrane. It has mechanical support and protection for cells.
Fact: Plant cells whose cell walls have been removed by cellulase no longer maintain their original shape. Such cells will burst like red blood cells when placed in clean water.