BIO1 11_12 Q1 2021 Past Paper PDF

Unit 2: Cell Structure and Function Lesson 2.1 Prokaryotes and Eukaryotes Contents Introduction 1 Learning Objectives 2 Warm Up...

Unit 2: Cell Structure and Function Lesson 2.1 Prokaryotes and Eukaryotes Contents Introduction 1 Learning Objectives 2 Warm Up 2 Learn about It! 4 The Two Types of Cell 4 Prokaryotic Cell 4 Eukaryotic Cell 4 Distinguishing Features of Prokaryotic and Eukaryotic Cells 4 Presence of Nucleus 5 Cell Wall and Cell Membrane 5 Endomembrane System and Other Organelles 6 Ribosomes 7 The Shape of DNA and Number of Chromosome 8 Cell Size 9 Mode of Reproduction 10 DNA Replication 11 Transcription and Translation 11 Key Points 13 Check Your Understanding 13 Challenge Yourself 15 Photo Credit 16 Bibliography 16 Unit 2: Cell Structure and Function Lesson 2.1 Prokaryotes and Eukaryotes Introduction There are various types of houses. They come in different forms and sizes. Some people live in an apartment. Some prefer to live in a condominium. There are houses with two or more floors and some houses are bungalows. Some houses have several rooms or partitions like a mansion, and some houses like a studio-type condominium unit do not have partitions. If you were to choose, what type of house would you prefer? In your own opinion, how will you describe a “perfect” house? Like the different types of houses, different organisms also have varying types of cells. These cells also contain different structures that all contribute to the normal functions necessary for life, just like houses. This lesson will discuss prokaryotic and eukaryotic cells which are found in different organisms. 2.1. Prokaryotes and Eukaryotes 1 Unit 2: Cell Structure and Function Learning Objectives DepEd Competency In this lesson, you should be able to do the Distinguish prokaryotic and following: eukaryotic cells according to their Describe prokaryotic and eukaryotic cells. distinguishing features Compare and contrast the features of (STEM_BIO11/12-Ia-c-3). prokaryotic and eukaryotic cells. Warm Up Spot the Difference 15 minutes Spot the difference is a type of puzzle game, much like crosswords and Sudoku. In this activity, you have to look into the details of the given pictures and identify their differences. Materials a device with an internet connection marker manila paper projector and white screen laptop Procedure 1. Click the link below to play the game. Private Investigator “Private Investigator,” Hidden247.com (nd), https://web.archive.org/web/20170630142237/https://www.hi dden247.com/PrivateInvestigator.html, last accessed on May 12, 2020. 2.1. Prokaryotes and Eukaryotes 2 Unit 2: Cell Structure and Function 2. The game involves observing differences and finding evidence in order to win. 3. After the online game, form six groups. Each group should occupy a designated area in the classroom as assigned by the teacher. 4. Your teacher will show two pictures: pictures A and B. Refer to Fig. 2.1.1. 5. You will be given one minute to take a look at the picture and spot the difference between pictures A and B. 6. After one minute, your group must write all the differences that you observed between pictures A and B on a sheet of Manila paper. You will be given another minute to do that. 7. Post your Manila paper sheets on the board for checking. 8. The group with the most number of correct answers will be declared as a winner. Picture A Picture B Fig. 2.1.1. (A) A leaf section under the microscope, (B) Dividing sea urchin embryo Guide Questions 1. Were you able to solve the case in the online game that you played? If so, how did you solve it? 2. Did you encounter some difficulties in the activity? If so, what are the difficulties that you encountered? 3. Based on the activity, what is the common answer of the class in terms of the difference between pictures A and B? 2.1. Prokaryotes and Eukaryotes 3 Unit 2: Cell Structure and Function Learn about It! The Two Types of Cell Like houses, cells come in different forms and sizes. A cell, the basic functional unit of life, is classified into two types: prokaryotic cell and eukaryotic cell. How can you differentiate a prokaryotic cell from a eukaryotic cell? Prokaryotic Cell A prokaryotic cell is a type of cell that does not have a nucleus and membrane-bound organelles within its cytoplasm. This type of cell is like a studio-type condo unit that does not have several compartments. Prokaryotes are small, single-celled organisms that have prokaryotic cells. These organisms are metabolically diverse because they can utilize different nutrients and energy sources and they can inhabit all types of environment on Earth. All bacteria that include the organisms of domains Archaea and Bacteria are considered as prokaryotes. Eukaryotic Cell The other type of cell that is characterized by the presence of nucleus and membrane-bound organelles within its cytoplasm is called a eukaryotic cell. Membrane-bound organelles of eukaryotic cells provide compartmentalization in the cell. This is comparable to a mansion that has several rooms or compartments. Domain Eukarya which includes protists, fungi, plants, and animals are examples of eukaryotes. Eukaryotes are organisms that consist of eukaryotic cells. Distinguishing Features of Prokaryotic and Eukaryotic Cells In the Warm Up activity, you were tasked to spot the differences between the given pictures. To spot the differences, you had to look into the details of the pictures. Cells are classified into two types because scientists spot certain differences between them. The details that the scientists looked into are the distinguishing features of prokaryotic and eukaryotic cells. 2.1. Prokaryotes and Eukaryotes 4 Unit 2: Cell Structure and Function Presence of Nucleus The main feature that distinguishes eukaryotic cells from the prokaryotic cells is the presence of a nucleus with a nuclear membrane that encloses the genetic materials (DNA or deoxyribonucleic acid) as seen in Fig. 2.1.2.. In a prokaryotic cell, the genetic materials (DNA) are concentrated in a region of the cytoplasm called the nucleoid. The term prokaryotic comes from the Greek terms pro- which means before and karyon or kernel that refers to the nucleus. On the other hand, the term eukaryotic comes from the Greek terms eu- meaning true and karyon or kernel. Fig. 2.1.2. The genetic material is enclosed in the nucleus of eukaryotes and in the nucleoid region of prokaryotes. Cell Wall and Cell Membrane The cell wall and the cell membrane share some functions in both prokaryotes and eukaryotes. The cell wall provides shape and rigidity to the cell and the cell membrane provides protection and plays an important role in the transport of materials. However, the cell wall is present in almost all prokaryotic cells, but not in most eukaryotic cells (these are not found in animals and most protists). Structurally, the cell wall of prokaryotes is made up of peptidoglycan – a complex sugar (polysaccharide) and a few amino acids. In eukaryotes, it is either made up of cellulose as in plants and chitin in fungi. 2.1. Prokaryotes and Eukaryotes 5 Unit 2: Cell Structure and Function As for the cell membrane structure, prokaryotes do not have sterols in the cell membrane but have a sterol-like lipid component called hopanoid. In eukaryotic cells, the sterols that are present in the cell membrane are cholesterol (animals), phytosterol (plants), and ergosterol (fungi). Endomembrane System and Other Organelles Another distinguishing feature of the prokaryotic and eukaryotic cells is the presence of the endomembrane system. This refers to the interacting organelles between the nucleus and the cell membrane. The endomembrane system includes the rough and smooth endoplasmic reticulum, Golgi apparatus, lysosome, endosome, and vacuole as shown in Fig. 2.1.3.. The endomembrane system is present in eukaryotic cells, but not in prokaryotic cells. Other organelles like mitochondria and chloroplast are also present in eukaryotic cells, but not in prokaryotic cells. Fig. 2.1.3. Endomembrane system and other organelles of a plant cell, which is an example of a eukaryotic cell 2.1. Prokaryotes and Eukaryotes 6 Unit 2: Cell Structure and Function The presence of organelles in eukaryotic cells provides compartmentalization. It increases the surface area-volume ratio of the cells, allows the occurrence of simultaneous cell activities without interference from each other, and allows separation of DNA in the nucleus, mitochondria, and chloroplast. Did You Know? All eukaryotes have mitochondria except Giardia lamblia or Giardia duodenalis. This organism is a flagellated parasitic protist that colonizes the small intestine, causing giardiasis. Ribosomes Ribosomes are present in both prokaryotic and eukaryotic cells. These have the same function in both, which is protein synthesis. In terms of location and structure, however, they differ from one another. In a prokaryotic cell, all ribosomes are found in the cytoplasm. In eukaryotic cells, they can be found in the cytoplasm, outer nuclear membrane, rough endoplasmic reticulum, mitochondrion, and chloroplast. Generally, ribosomes are made up of large and small subunits. Each subunit is made up of rRNA (ribosomal ribonucleic acid) and proteins. Prokaryotic cells, mitochondria, and chloroplast contain 70S ribosomes while eukaryotic cells have 80S ribosomes. S or Svedberg unit is the unit of the sedimentation coefficient. 2.1. Prokaryotes and Eukaryotes 7 Unit 2: Cell Structure and Function The DNA structure of the prokaryotic and eukaryotic cells is different from one another. Will it affect the process of DNA replication, transcription, and translation? If so, how? If not, why did you say so? The Shape of DNA and Number of Chromosome DNA or deoxyribonucleic acid as shown in Fig. 2.1.4. is the genetic material in prokaryotic and eukaryotic cells. It codes for proteins and RNA. It also transmits information from one generation to the next generation. In prokaryotic cells, DNA is found in the nucleoid region of the cytoplasm. Prokaryotes, as well as the mitochondrion and the chloroplast, have covalent, closed, circular DNA that is not coiled in protein “spools” called histones. Most prokaryotes have only one chromosome and an extrachromosomal DNA called a plasmid. Fig. 2.1.4. In eukaryotes, the DNA is wrapped around histones to form nucleosomes. 2.1. Prokaryotes and Eukaryotes 8 Unit 2: Cell Structure and Function On the other hand, in eukaryotic cells, the linear DNA is coiled in histones and is found inside the nucleus. Eukaryotes have more than one chromosome so histones are essential in packaging DNA into nucleosomes and helping it to condense into chromatin. Through this, several chromatins can fit into the nucleus without the high risk of mechanical damage. Cell Size Prokaryotic cells are smaller compared to eukaryotic cells. Typical prokaryotic cells can range from 0.1 to 5µm in diameter while eukaryotic cells are typically 10 to 100µm in diameter. Despite their larger size compared to prokaryotic cells, eukaryotic cells can still perform metabolic activities efficiently due to the compartmentalization of cellular parts as discussed previously. Relative sizes of bacteria (prokaryote), plant cell (eukaryote), and animal cell (eukaryote) 2.1. Prokaryotes and Eukaryotes 9 Unit 2: Cell Structure and Function Prokaryotes are unicellular or are made up of only one cell. On the other hand, eukaryotes are either unicellular or multicellular. Most protists and yeast are unicellular eukaryotes. Plants, animals, most fungi and some protists are multicellular eukaryotes. Multicellular organisms are composed of more than one cell. Mode of Reproduction Most prokaryotic cells reproduce through binary fission and some reproduce through spores. Binary fission is a process of reproduction wherein one cell is divided into two new cells. In eukaryotic cells, individual cells reproduce through mitosis and meiosis. Mitosis (somatic or body cell division) and meiosis (sex cell division) are types of cell division in eukaryotic cells. Mitosis is the type of cell division that involves somatic or body cells. This process produces two identical, diploid daughter cells. It is important for growth, development, and tissue repair. On the other hand, meiosis involves sex cells or gametes. This process produces four, non-identical, haploid daughter cells. It is also known as gametogenesis or gamete formation which is important in sexual reproduction. Take note that many eukaryotic organisms are multicellular, meaning that the mode of producing more cells is not necessarily the way that these organisms reproduce. Eukaryotic cells undergoing mitosis 2.1. Prokaryotes and Eukaryotes 10 Unit 2: Cell Structure and Function DNA Replication DNA replication is the process of synthesizing a new DNA strand using an old DNA strand as a template. In both types of cell, it is an antiparallel and semiconservative process wherein both strands are replicated through complementary base pairing. However, the difference in the characteristics of DNA also result in different processes in prokaryotic and eukaryotic cells. DNA replication in eukaryotes takes a longer time than in prokaryotes because eukaryotes have more DNA than prokaryotes. In prokaryotic cells, DNA replication occurs in two opposing directions at the same time in the cytoplasm. On the other hand, eukaryotic cells have multiple points of origin and use unidirectional replication within the nucleus. DNA replication in prokaryotic cells and eukaryotic cells also differs in terms of enzymes involved in the process. For example, in eukaryotes, an enzyme called telomerase is involved in the replication of telomeres of the eukaryotic chromosome. Prokaryotic cells do not have telomeres so telomerase is not present and involved in their DNA replication. Prokaryotes continuously replicate their short DNA while eukaryotes only replicate their DNA during the S-phase of interphase in cell division. Transcription and Translation Transcription refers to the synthesis of RNA using DNA as a template. Translation then refers to the process of protein synthesis. In prokaryotic cells, transcription and translation can be done at the same time in the cytoplasm. Aside from that, there is no post-transcriptional processing because the DNA of prokaryotes does not have a non-coding part called introns. In eukaryotic cells, the transcription occurs in the nucleus and the translation occurs in the cytoplasm. Eukaryotic DNA contains exons (coding part) and introns (non-coding part). Post-transcriptional processing is done in eukaryotes to remove introns and come up with the final RNA. An unknown cell is discovered in a sulfur-rich area. The cell is about 750 µm in size but there are no partitions or compartments inside the cell. What type of cell is the unknown cell? 2.1. Prokaryotes and Eukaryotes 11 Unit 2: Cell Structure and Function Prokaryotic and eukaryotic cells vary in different ways. Table 2.1.1. summarizes the distinguishing features of both prokaryotes and eukaryotes. Table 2.1.1. Distinguishing features of prokaryotic and eukaryotic cells Distinguishing Features Prokaryotes Eukaryotes Presence of nucleus absent present Endomembrane system absent present Both are present in all The cell membrane is present prokaryotes. to all cells. Cell wall and cell The cell wall is made up of The cell wall is made up of membrane peptidoglycan and it has cellulose (plant cell) and hopanoid in the cell chitin (fungi). It has sterols in membrane. the cell membrane. Ribosome present , 70S ribosome present, 80S ribosome Shape of DNA and one covalently, closed, more than one linear DNA number of chromosome circular DNA with histone around 10-100µm in Cell size typically 1-5µm in diameter diameter one point of origin, multiple points of origin, DNA replication bidirectional unidirectional Transcription occurs in the Transcription and Both processes occur in the nucleus and translation translation cytoplasm. occurs in the cytoplasm Binary fission and spore Mode of reproduction Mitosis and meiosis reproduction 2.1. Prokaryotes and Eukaryotes 12 Unit 2: Cell Structure and Function Key Points ________________________________________________________________________________________ Cells are classified into two types: prokaryotic cell and eukaryotic cell. ○ Prokaryotic cells are found in prokaryotic organisms while eukaryotic cells are found in eukaryotic organisms. Examples of prokaryotes are Archaeans and Bacteria. Examples of eukaryotes are plants, animals, fungi, and protists. Prokaryotic and eukaryotic cells vary in terms of presence of nucleus, endomembrane system, cell wall and cell membrane, ribosome, shape of DNA and number of chromosome, cell size, DNA replication, transcription and translation, and mode of reproduction. ________________________________________________________________________________________ Check Your Understanding A. Write P if the statement applies to prokaryotes, E if it describes a eukaryote, and B if the statement is applicable for both prokaryotes and eukaryotes. 1. It has a circular genetic material. 2. Sterols are embedded in the cell membrane. 3. The process of translation occurs in the cytoplasm. 4. The cell wall is made up of peptidoglycan. 5. It undergoes binary fission to produce new cells. 6. It has a cell membrane that facilitates the entrance and exit of materials in the cell. 7. All of its ribosomes are found in the cytoplasm. 8. DNA is known as genetic material. 9. It has an endoplasmic reticulum. 10. DNA replication occurs during S-phase. 2.1. Prokaryotes and Eukaryotes 13 Unit 2: Cell Structure and Function B. Write the letter of the correct answer. 1. Which of the following is an advantage of prokaryotic cells over eukaryotic cells in terms of DNA replication? A. They have a more complex process of replication. B. They have a faster rate of DNA replication. C. They have more DNA compared to eukaryotic cells. D. They can produce DNA even without nutrients. 2. Which of the following processes will occur in eukaryotic cells but not occur in prokaryotic cells? A. DNA replication B. Protein synthesis C. Transcription D. Vesicular transport 3. What is the advantage of non-compartmentalization in protein synthesis of prokaryotes? A. DNA is replicated at a faster rate. B. More energy will be used to produce proteins. C. Transcription and translation can occur simultaneously. D. Translation occurs after transcription and DNA replication. 4. Why is the nuclear membrane important in eukaryotic cells? It ____________. A. controls different cellular processes. B. prevents leakage of genetic materials. C. allows other organelles to function separately. D. confines and protects the DNA to prevent any damage. 5. Why are histones not necessary in prokaryotic cells? Prokaryotes have __________________. A. closed circular DNA structure. B. additional DNA called plasmid. C. only one chromosomal DNA. D. more than one DNA that cannot be packaged by histones. 2.1. Prokaryotes and Eukaryotes 14 Unit 2: Cell Structure and Function C. Answer the questions correctly in 2-3 sentences only. 1. Discuss the importance of histones in a skin cell. 2. Compare and contrast bacterial cell wall and plant cell wall. 3. Describe the genetic material of Lactobacillus casei. 4. Explain why mitochondria and chloroplasts are similar to a bacterial cell. 5. Describe how transcription and translation occur in a protist cell. Challenge Yourself Answer the following questions correctly in 2-3 sentences only. 1. Why are mutations more common in prokaryotic cells than in eukaryotic cells? 2. What can possibly happen to the eukaryotic cell if there is no endomembrane system? 3. What type of cell will have a better chance of survival in an environment with limited nutrient and energy sources? Why did you say so? 4. A prokaryotic cell and eukaryotic cell are subjected to a high temperature which resulted in the denaturation of proteins. Which type of cell will be more affected? Explain your answer. 5. Construct a Venn diagram that shows the differences between prokaryotic and eukaryotic cells in terms of structure. Write 3 statements or phrases in each part of the diagram. 2.1. Prokaryotes and Eukaryotes 15 Unit 2: Cell Structure and Function Photo Credit Mitosis_(261_13)_Pressed;_root_meristem_of_onion_(cells_in_prophase,_metaphase,_anaph ase,_telophase) by Josef Reischig is licensed under CC BY-SA 3.0 via Wikimedia Commons. Bibliography Blake, Leesa, and Donald I. Galbraith. McGraw-Hill Ryerson Biology 11. Toronto: McGraw-Hill Ryerson, 2002. Campbell, Neil A. Biology (8th Edition), 2009. Campbell, Neil A., Michael L. Cain, Peter V. Minorsky, Jane B. Reece, Lisa A. Urry, and Steven Alexander Wasserman. Biology: a Global Approach. Harlow, Essex, England: Pearson Education Limited, 2018. Mader, Sylvia S. Concepts of Biology. New York: McGraw-Hill, 2011. Madigan, Michael T., Kelly S. Bender, Daniel H. Buckley, W. Matthew. Sattley, and David A. Stahl. Brock Biology of Microorganisms. Harlow, United Kingdom: Pearson Education Limited, 2017. Study.com. Study.com. Accessed February 4, 2020. https://study.com/academy/lesson/eukaryotic-and-prokaryotic-cells-similarities-and- differences.html. 2.1. Prokaryotes and Eukaryotes 16