7th Grade 2nd Term Cell Biology PDF

www.tntextbooks.in Unit 4 Cell Biology Learning Objectives ™ To compare the plant cell with the animal cell and understand their similarities...

www.tntextbooks.in Unit 4 Cell Biology Learning Objectives ™ To compare the plant cell with the animal cell and understand their similarities and dissimilarities ™ To understand the cell as a fundamental unit of life ™ To know and understand the di!erent types of Human cells and their related functions ™ To know the functions of di!erent cell organelles ™ To compare di!erent cell organelles, their functions and know their similarities and specialties 57 VII Std Science Term-2 EM Unit 4 Folder.indd 57 20-07-2019 1.48.31 PM  www.tntextbooks.in Introduction ACTIVITY 1 Sona had a dinner, some hour later, she experienced a stomach pain and went to a Do you remember the lesson studied clinic. After examination, the Doctor told Sona in previous class, how will you find whether on object is living or non – living? Write it that she had eaten food contaminated with a down. An object is living or non – living? type of bacteria which might have caused food 1. Form a team and work together to poisoning. Bacteria are micro-organisms that write down some of the functions of life, can be seen only under microscope and not which you can remember. seen through nacked eyes. Salmonella species is _________________________________ a bacteria that can cause food-borne infection. 2. Do you think that an individual cell is living? Explain your answer _________________________________ 3. Write about various organelles of a cell which you know. _________________________________ 4.1 Cell as a fundamental unit of life: The building wall is made up of numerous bricks. In the similar manner, a bee hive is Our earth is a beautiful place where in composed of numerous hexagonal units. Some di!erent types of organisms happily coexist. of the organisms are represented by a single cell. From minute mosses to huge conifers, invisible Therefore, they show a simple organization. The bacteria to huge blue whale, all have a basic unit basic functional unit of an organism is called, a cell. called Cell. Let us study about the cell. Structure of a cell represent the arrangement Plant Plant Cell Human Animal Cell 58 VII Std Science Term-2 EM Unit 4 Folder.indd 58 20-07-2019 1.48.31 PM  www.tntextbooks.in of parts or organells in a cell. Function is the can see cells of onion and human through a activity of each part or organell in a cell. Cells microscope. Onion and man are examples for are the basic building blocks of an organism. multicellular organism. You learnt that atoms are the basic building blocks of matter in chapter three. Likewise, human body is made up of animal cell and plant is made up of plant cell. Unicellular organisms Some simple organisms, are made up Onion of only one cell. They are called unicellular organisms, which can be seen with the help of a microscope. There are many single – celled microscopic organisms. Have a look at the image. Chlamydomonas and an Amoeba, a single cell organisms which carryout entire functions. The body of all organisms are made up of tiny building blocks called, cells. Bacteria are also one celled Human unicellular organisms. Cell to organism Many cells function together to form tissues, di!erent tissues combined together to form an organ and di!erent organs to form an organ system, which leads to form an organism. Amoeba Organisms. Many types of organ systems function together in a body, e.g. respiratory system, digestive system, excretory system circulatory system etc. Organ System Many organs together form an organ Chlamydomonas system, which is concerned with a specific Multicellular Organism function. For example, Respiratory system, The cells are organized into tissues, organs which has organs like nostrils, nasal chamber, and organ systems in a multicellular organism. wind pipe and lungs that helps in the process of Macroscopic organisms are visible and consists respiration. In a plant, the root system consists of many cells. The body of macroscopic of primary root, secondary root and tertiary organisms involves various functions. You root, which does the function of conduction of 59 VII Std Science Term-2 EM Unit 4 Folder.indd 59 20-07-2019 1.48.33 PM  www.tntextbooks.in Organism Organ system Organ Tissue Cell !"#$%&'()* Organism Organ system Organ Tissue Cell !"#$%&'()* water, mineral and also fixation. have transport, protective and ground tissues. Organ Cell A collection of di!erent tissues worked The cell is a basic structural and functional together to perform a specific function or unit of life. Cell is the building unit of living functions is called an organ. Human body has organisms. You can see in a hand, how many di!erent organs like stomach, eye, heart, lungs types of cells are there to work together to etc., are made up of di!erent type of tissues. perform its functions. So, cell is known as the Plant have organs such as leaves, stems, and basic unit of life. roots. Tissue Tissue is a group of cells, organized for a Epidermal cells Bone cells specific function. Tissues have following features like same shaped cells or di!erent shaped cells to perform a common function. Human Muscle cells and other animals are made up of nervous, epithelial, connective and muscle tissues. Plants Nerve cells 60 VII Std Science Term-2 EM Unit 4 Folder.indd 60 20-07-2019 1.48.34 PM  www.tntextbooks.in one organelle stops its function, then the cell is ACTIVITY 2 programmed to die. Find out major organs that are part of the Cell Structure circulatory system of a human body and As we have mentioned listout their functions before, all cells have some common structure. 4.2 Plant and Animal cell comparison These are Why do plant cells 1. Cell membrane di!er from animal cells? 2. Cytoplasm, and They di!er from each 3. Nucleus (In most eukaryotic cells). other because they have to The structure of a typical plant and animal cell perform di!erent functions. shows following peculiarities: Now you know that there Cell membrane are many main similarities between plant and The boundary of an animal cell is the animal cells. Let us see how they di!er from one plasma membrane, which is also called as cell another as given in the picture (Activity 3). membrane 4.3 Human cells related to functions Cell wall - “Supporter and Protector” Different types of cells All animal and plant cells are enclosed or Our body is made up of many di!erent surrounded by a cell membrane as you learned kinds of cells. Each type of cell is specialized to before. However, as you might have noticed perform a specific function. Depending on the previously that, animal cells often have an function, cell has specific shape, size and may irregular shape, whereas plant cells have a much have some components which other type of more regular and rigid shape. cells do not have. Have a look at the di!erences Plant cells have an additional layer on the between nerve cells and red blood cells in the outer side of the cell membrane. This is called images. Even though there are many di!erent as the cell wall, that provides a frame work for types of cells, there are some components support and stability. common to all type of cells. Let us take a look at The cell wall is formed from various this in the next section. compounds, the main one being cellulose. What’s inside a cell? Cellulose helps to maintain the shape of the Inside a cell, there are many tiny structures plant cell. This allows the plant to remain rigid called cell organelles. These organelles are and upright even if it grows to great heights. responsible for providing needs of the cell. Each cell is interconnected with its neighboring They work to bring in food supplies, get rid cells through openings called Plasmodesmata. of waste, protection and repair of the cell, and help it to grow and reproduce. Each one has a specific function to do for the cell. And, if any Cell wall 61 VII Std Science Term-2 EM Unit 4 Folder.indd 61 20-07-2019 1.48.34 PM  www.tntextbooks.in. Small vacuole filled with both inorganic Large vacuole and organic molecules, filled with both inorganic along with water to support and organic molecules, the organelle along with water to support the organelle The cytoplasm Endoplasmic reticulum a includes all living network of membranous parts of cell with in tubules and is involved in the cell membrane protein and lipid synthesis. but excluding the nucleus. Mitochondria are organelles, They make most of the cell’s supp of adenosine triphosphate supply (ATP a molecule that cells use as (ATP), sou a source of energy. Their main job is to convert energy. Golgi body is a complex of vesicles and folded membranes, involved in secretion and intracellular transport. 62 VII Std Science Term-2 EM Unit 4 Folder.indd 62 20-07-2019 1.48.37 PM  www.tntextbooks.in ACTIVITY 3 Study the pictures given and write the di!erences between cells that you observe in the given table Animal Cell Mitochondria Centrioles Golgi apparatus Endoplasmic recticulum (Rough) Nucleous Nucleus Cytoplasm Plasma membrane 1. 2. 3. 4. 5. Specialised cell Structure Function Epithelial cells – they are They cover the surface of the mostly %at and columnar in body for protection shape Muscle cells – they are long and They can contract and relax spindle shaped allowing the cell for movement. Nerve cells are specialized to Nerve cells – the body of ner- carry and conduct messages vous cell is branched with an that coordinate the functions of elongated nerve fiber. the body. Red blood cells carry oxygen Red blood cells – Round, and collect carbon dioxide biconcave and disc shaped from various part of the body. 63 VII Std Science Term-2 EM Unit 4 Folder.indd 63 20-07-2019 1.48.41 PM  www.tntextbooks.in Protoplasm vs. Cytoplasm Stem Cells In particular, the material inside and outside Stem cells are quite amazing the nuclear membrane is known as Protoplasm. as they can divide and The %uid inside the nucleus is known as the multiply while at the same nuclear %uid or nucleoplasm and outside the time with their ability to develop into any nucleus is called as cytoplasm. other type of cell. Embryonic stem cells are very special as they can become absolutely Inside the cytoplasm any type of cell in the body, for example, Mitochondria - “Power house of the blood cell, nerve cell, muscle cell or gland Cell”. cell. So they are utilized by the Scientist Do you remember learning about the food and Medicos, to cure and prevent some as the energy source for the body? Just as wood diseases like Spinal cord injury. is burnt to release the stored potential energy to make a fire to heat some water. The food that you ate to be broken down in order to release the energy which can be used by your body to function. Mitochondria are responsible to do this function. Very active cells have more mitochondria than cells that are less active. Which type of cell, do you think, will have more mitochondria, a muscle cells or a bone cell? Cytoplasm - I am the “Area of Mitochondrian is an oval or rod shaped Movement”. double membrane bounded organelle. Aerobic When you look at the temporary mounts respiratory reactions take place with in the of an onion peel, you can see a large region of mitochondrion to release energy. So it is known each cell an enclosed by the cell membrane. This as “the Power House” of the cell. The energy region takes up very little stain. It is called the produced within the mitochondrion is used for cytoplasm. all the metabolic activities of the cell The cytoplasm includes all living parts of the cell with in the cell membrane, excluding the nucleus. The cytoplasm is made up of the cytosol and cell organelles. The cytosol is a watery, jelly- like medium made up of 70% - 90% water and usually colourless. Cell organelles and structures present in a cell are endoplasmic reticulum, vacuole, ribosome, golgi body, lysosome, mitochondria, centriole, chloroplast, surrounded by plasma Mitichondrion membrane and cell wall. 64 VII Std Science Term-2 EM Unit 4 Folder.indd 64 20-07-2019 1.48.44 PM  www.tntextbooks.in Chloroplast- “Food Producers”. Various range of these Do you notice the green organelles plastids impart di!erent present in plant cells and absent in animal cells. colours to various parts of Chloroplasts are the only cell organelles that plant. Chromoplast impart can produce food from the colour to %ower and fruits. As fruits ripen, sun energy. Only plants with chloroplasts change to chromoplasts. chloroplast are able to do Starch is converted to sugar. photosynthesis because they contain the very important Golgi Complex- I need a break green pigment, chlorophyll. Membrane bounded sacs are stacked on top Chlorophyll can absorb radiant energy from of the other with associated secretory vesicles are the Sun and convert it to the chemical energy collectively known as golgi complex. Functions which can be used by the plants and animals. of golgi complex are the production of secretory Animal cells lack chloroplasts and are unable to substances, packaging and secretion. This is the do photosynthesis. secret behind the change in the colour and taste of fruits Leaf Cells in a leaf Chloroplast Observing chloroplast in algae Collect some algae from pond and separate out thin filaments of them. Place a few filaments on a slide. Observe it under the Lysosome- “Suicidal Bag”. microscope. Take the help of given figure and draw the picture of chloroplast that you have Everything I touch, I destroy observed under the microscope. Chloroplast You will find organelles called as is a type of plastid. which are present only in lysosomes, which are very small to view using plant cells. Plastids are mainly of two types a light microscope. They are the main digestive - chromoplasts (coloured) and leucoplasts compartments of the cell. They lyse a cell, hence (colourless). they are called “suicidal bag”. 65 VII Std Science Term-2 EM Unit 4 Folder.indd 65 20-07-2019 1.48.44 PM  www.tntextbooks.in Rough endoplasmic reticulum are rough due to the ribosomes attached to the membrane. which helps in the synthesis of protein. Smooth endoplasmic reticulum. It is a network of tubular sacs without ribosomes on the membrane. They play a role in the synthesis of lipids, steroids and also transport them within Lysome the cell. Centrioles Nucleus - Everyone do what I say. They are generally found close to the nucleus and are made up of tube-like structures. Acting like the “Brain” of the cell Centrioles or centrosomes are present only in ™ Plant and animal cells have a nucleus inside animal cells and absent in plant cells. It helps the cytoplasm. It is surrounded by a nuclear in the separation of chromosomes during cell envelope. One or two nucleolus and the division. chromatin body are present inside the nucleus. During cell division, the chromatin body is organised into a chromosome. Storage of genetic material and transfers heredity characters from generation to generation are the functions of chromosome. Functions of Nucleus ™ In controls all the processes and chemical reactions that take place inside the cell. Structure of a Centriole ™ Inheritance of character from one generation Endoplasmic reticulum - You guys, be to another. quiet, I have so much work to do It is an inter membranous network made up of %at or tubular sacs within the cytoplasm. Endoplasmic reticulum is of two types. They are rough endoplasmic reticulum and smooth endoplasmic reticulum. Nucleus Endoplasmic reticulum 66 VII Std Science Term-2 EM Unit 4 Folder.indd 66 20-07-2019 1.48.46 PM