greetings to everyone teacher janet here it is the start of a new academic year and i would like to wish a warm welcome to all our new form 4 students who will be studying biology for the next two years so biology is an interesting subject where we study a lot about the processes that go on in the human body and also about other organisms and the environment today we are going to discuss an interesting topic from form 4 chapter 2 of the biology kssm syllabus entitled cell biology and organization the subtopic is 2.1 cell structure and function so what are cells now cells are the smallest biological unit of life found in living organisms they are called the building blocks of life just as a house is made of bricks so an organism is made up of many cells for humans we are made up of trillions of cells now the interesting thing about a cell is that it is made up of many cellular components within such as these here and they all have different functions but they work together for the survival of the cell so that the cell can carry out the basic living processes like respiration excretion nutrition even movement for some cells such as white blood cells and sperm cells so the human body has about 200 different types of cells such as muscle cells ripple cells white blood cells nerve cells with a wide range of structures and functions and each cell is well adapted to carry out its function efficiently let's find out more about our basic unit the amazing cell [Music] now what are the learning standards or learning outcomes that a student must achieve okay after this video so um for topic 2.1 cell structure and function the first learning standard is you must be able to prepare microscope slides of animal and plant cells so this is a practical activity in the laboratory and the teacher will teach you how to prepare the microscope slides of animal cells like the cheek cell cell pp taken from the mouth of students and also for plant cells usually the plant cells that are observed under the microscope are the onion cells now the epidermal cells of the anion bowel okay so other than preparing this these micro scope slides you must be able to draw and label the structures okay inside the cells or the structures of the cells now identify the structures of animal and plant cells based on observations through a light microscope so light microscope is the normal type of microscope that we use in the laboratory which uses light to illuminate the slide okay so that you can see the structures clearly so this is not a very powerful microscope compared to the electron microscope which is able to enlarge the object okay produce an enlarged image of the object which is uh very to view the structures very clearly okay so uh we'll talk about that later now number three analyze the components of animal and plant cells as seen on micrographs so micrographs what are they so they are photographs taken by using a microscope like the electron microscope so graph becomes a microscope and photograph a photograph taken by using a microscope such as the electron microscope and it is actually a magnified photograph of an object and you can see this in the see these pictures in your form for textbook the micrographs so you must be able to recognize the components on the micrographs right now state the main functions of components of animal and plant cells as seen on micrographs right this will be discussed in video number two we'll discuss the functions of the components of animal and plant cells also the parts of the animal and plant cells such as the nucleus ribosome mitochondrion and so forth we'll discuss the structure and the functions of these components which are mostly organelles now so we'll talk about that later and then lastly we're going to compare and contrast the components of animal and plant cells to see the difference between animal and plant cells so this will also be in video number two part two okay you'll be in the second video after this so first let's discuss cell structure and function subtopic 2.1 right now all living things are made up of cells that are combined together okay so cells are like the building blocks of the bodies of organisms now the definition for cells are cells are the basic structural units of all living things right that means they are the units that are used to build up the structure of the body of living things or organisms such as human beings animals like cats fishes insects even worms and so forth they are all made up of cells okay so for a human being the number of cells in the body is about 30 trillion cells okay right next we have the word organelles organelles actually mean within inverted commas tiny organs but they are not organs okay because organs are bigger organs are made of many many cells so organelles are the tiny small or small structures in a cell which perform specific functions such as the nucleus mitochondrion chloroplast vacuum and so forth which we will study later now here you can see a nucleus right which has a spherical or round shape okay that's the control center of the cell and then in plant cells there is the chloroplast which is an organelle that carries out photosynthesis to produce organic food substances for the plant and then cells must have mitochondrion okay which is an organelle that is involved in respiration to produce energy okay for the cell to carry out its activities now what about the word cellular components so cellular components are parts of a cell that have different functions so they will include the organelles they include the organelles such as the nucleus mitochondrion ribosome and lysosome and other structures such as cell wall plasma membrane and cytoplasm so these other structures are not called organelles so the cell wall in plant cells plasma membrane and cytoplasm okay they are not not called organelles now so cellular components is just a general name for all the parts of the cell they have different functions and they include organelles now so the cellular components that can be seen under the light microscope which we have in the school laboratory right are plasma membrane cytoplasm nucleus cell wall large central vacuole in plant cells and chloroplast okay so take note that the first three plus one membrane cytoplasm nucleus are found in both plant cells and animal cells okay but the last three year cell wall large central vacuole and chloroplasts are only found in plant cells not in animal cells okay now we'll discuss more of this in the next slide right so in your textbook there are two practical activities that you can carry out activity 2.1 and 2.2 to prepare and then examine animal and plant cells under the light microscope so this is an example of a light microscope it has an eyepiece and then a few objective lenses of different power and then here's the stage where you put the the slide then below it is the light source it could be a light bulb connected to an electrical supply it could be a mirror that reflects the sunlight onto the stage okay then um so the aim of the light microscope is to produce a magnified image of the object that we want to see and using light to illuminate the stage okay to brighten up so that we can see the image clearly now so how do we prepare the cheek cells and what is the structure of the cheek sauce now firstly you have to gently scrape the inside of the cheek with a blunt toothpick cell ppm get the cell pp or cheek cells and then transfer the the cells on the tip of the toothpick into a drop of water on a clean glass slide actually the tip of the toothpick will you cannot see the cells on there also it look like there's nothing but actually once you have scraped the cheek with the toothpick the cells are already there huh so place the cells uh in a drop of water on a clean glass slide and cover cover with the coverslip and then stain the cheek cells with metalline bloom solution using a technique called the irrigation technique which your teacher will teach you and then examine the cheek cells under the light microscope and this is the result of our observation okay we have to know how to draw the structure of cheek cells which is a type of animal cells so firstly we can see that cheek cells do not have a fixed shape or a regular shape so this cheek cell has a different shape from this one huh and then there are three parts that we can see the plasma membrane which is the outer boundary then the cytoplasm which is stained uh like blue and the nucleus which is stained dark blue by the methylene blue solution in the cytoplasm you can see some dark spots those could be the organelles or tiny structures within the cell that carry out different functions so we'll discuss more of the organelles later so that's all you can see here of the the cheek cells under the light microscope which is not a very powerful microscope if you use another type microscope called the electron microscope you'll be able to see the organelles inside the cytoplasm okay more about that later now let's go on to the second type of cell which is the plant itself so for this we are going to uh use the epidermal cells of the onion to observe how a plant cell looks like now onion bulb okay you can cut it into half and then you can see a few layers of the scale leaves these are called scale leaves and they are not green in color because scale leaves are for storing organic food substances okay produced by the green leaves above the ground so the scale leaves are all under the ground the bulb is under the ground so it doesn't carry out photosynthesis so there's no chloroplast no green chloroplast which is a type of organelle that is green in color and carries out photosynthesis okay to produce the organic food substances for the plant so abnormal cells of onion remember of the onion butter does not have do not have chloroplasts okay because they are and they're not green in color so uh preparation is like this so first we get a scale leaf from the onion and then we remove the translucent epidermis from the inside of the scale so you take out one scale leaf is the inner side okay the epidermis on the inner side which is translucent that we take up not the one on the purple side not the epidermal cells on the purple side so add a drop of distilled water at the on the slide and then lay the onion epidermis on the water and then cover it with a coverslip and then again using the irrigation technique stain the cells this time with iodine solution okay now what do we observe under the light microscope so we can see that plant cells have a cell wall a plant cell has a cell wall and underneath it is the plasma membrane then you have the nuclear stained dark brown and the cytoplasm is stained light brown by the yellowish brown by the iodine solution okay then you may be able to see the vacuole which is a structure that contains water and other substances in the center of the cell okay so that's all that you can observe under the light microscope cellular plasma membrane nucleus cytoplasm and vacuum now how would the chloroplast look like under the light microscope so now we are going to discuss the structure of a leaf cell which is also a plant cell now let's discuss how the typical leaf cells would look like under the light microscope so for the leaf cells we can choose the leaf of use the leaf of hydrilla species or elodia species which are both aquatic plants that live submerged in the water in the pond water so why do we use the leaf of these plants because these leaves are very thin they have only a few layers of cells so we can take out one leaf put it on a drop of water in a drop of water on a slide and then cover cover it with a coverslip and that's all you can see the leaf cells quite clearly under the microscope okay so let's look at the leaf cells of hydrilla species and elonia species under the light microscope okay you can see that it has each cell has a cell wall and then underneath is the plasma membrane then again you have the cytoplasm nucleus and vacuum and the additional structure is the chloroplast compared to the epidermal cell of onion bowel okay now so this is a the structure called the chloroplast which you can see is green in color and it is because the chloroplast which is an organelle that has a specific function in the cell it contains the pigment chlorophyll so chloroplast is the small structure in the cell so it's an organelle whereas chlorophyll is the green pigment of warner the green coloring substance that is used to absorb the sunlight sunlight so that the chloroplast can carry out photosynthesis huh so anyway remember this structure is called the chloroplast but the pigment inside is called chlorophyll okay so we can see clearly because the chloroplast is colored green and it's comparatively big okay compared to some organelles all right and so these are the structures that you can see or the cellular components that you can see okay for a leaf cell that's observed under the light microscope so we already discussed the structures of animal cells and plant cells as seen under the light microscope right so the light microscope usually has a magnification of 1000 times which is quite low all right and this allows us to observe only the larger cellular components like plasma membrane nucleus vacuum chloroplasts right however there's another type of microscope called the electron microscope which is able to magnify a cell more times many more times such as 2 million times to enable us to see the smaller cellular components especially the organelles like mitochondrion ribosome lysosome golgi apparatus rough endoplasmic reticulum smooth endoplasmic reticulum and centrioles right so this type of microscope with high magnification and resolution uses electron beams in place of light to produce the enlarged images of tiny objects as you can see here the images will be projected onto the computer screen and okay this the researcher or scientist will sit here and look at what is projected uh so the size of the electron microscope is definitely much much bigger than that of a light microscope and so its price is also definitely higher and you can find these electron microscopes in universities right not in the school so we are going to study the components of animal and plant cells as seen under the electron microscope all right and we are going to study the structure and functions of these components especially the organelles most of them are organelles right so let us first review what the components of animal and plant cells are like okay based on what is seen under the electron microscope [Music] i wonder what are the components of an animal cell let's find out [Music] [Music] plasma membrane cytoplasm nucleus [Music] nucleus smooth endoplasmic reticulum mitochondria [Music] lysosome centriole golgi approaches lastly tiny ribosomes [Music] [Music] plant cells what are the components of a plant cell [Music] cell wall plasma membrane nucleus [Music] nucleus cytoplasm vacuum [Music] chloroplasts [Music] rough endoplasmic reticulum [Music] ribosomes goji apparatus smooth endoplasmic reticulum [Music] and lastly mitochondria [Music] [Music] so in the previous two slides we managed to view the 3d model of the structure of an animal cell and a plant cell right now normally in the exam you are asked to draw any of the cellular components in a cell usually they will ask you to draw the 2d structure that means two-dimensional shapes or structures which have the breadth and the length and no depth so don't worry about drawing 3d structures but rather focus on being able to draw the structures like what is seen here in this two dimensional diagram all right so here's a struct the picture of an animal cell and the structure within all right so we are just going to have a quick look at the components of the cell and then uh discuss very briefly the functions right for example nucleus nucleus is a big organelle in the cell and it consists of the nuclear membrane which is a membrane that surrounds the nucleoplasm inside the nuclear membrane has paused called the nuclear pole so that substances can move in and out and then the nuclear plasma is the medium inside the nucleus and there's a dark black spot called a nucleolus okay with specific function so what is the general function of a nucleus a nucleus controls all the cellular activities in the cell it's the big boss in the cell and it has chromosomes which are thin thread-like structures like this that contain a molecule called the dna molecule or the oxy-ribonucleic acid molecule which determines the characteristics of the cell and also the is involved in the control of the metabolic functions right now next we have the plasma membrane that surrounds the cell so the plasma membrane controls the movement of substances into the cell and out of the cell then there's the cytoplasm which is a gel-like medium for to for the biochemical reactions in the cells to be carried out right next we have the mitochondrion which is known as the powerhouse of the cell powerhouse because it generates energy through the oxidation of glucose during cellular respiration generates energy for cellular activities okay and next we have the lysosomes which are max of bags containing enzymes all right hydrolytic enzymes enzymes that can hydrolyze or break down complex organic molecules that protein and lipids so these lysosomes these lysosomes can digest complex organic molecules and also break down bacteria and also damage components in the cell like damage mitochondria okay then next we have the rough endoplasmic reticulum which is continuous with the nuclear membrane and the rough endoplasmic reticulum has ribosomes on it okay small particles called ribosomes so the function of the rough endoplasmic reticulum is that it transports proteins synthesized by these ribosomes and the orange particles here all right so it's for transport of proteins synthesized by ribosomes whereas the ribosomes synthesizes a ribosome will synthesize proteins all right so ribosomes are the site for synthesis of proteins okay which are then transported by the rough endoplasmic reticulum right and then next we have the smooth endoplasmic reticulum which is also for transport so the smooth endoplasmic reticulum does not have any ribosomes on it its function is to synthesize and transport glycerol and lipids it also carries out detoxification of drugs right in the body now next we have the golgi apparatus here all right which is has a c-shaped structures so the goji apparatus modifies packs and transports proteins and carbohydrates which we'll discuss in this we'll discuss in the next video then we have the central so centrioles are involved in cell division okay they form fibers called spindle fibers during cell division but they're only found in animal cells centrals are only found animal cells and not implant cells okay and then we may have small vacuums in the cell which are backs like sex or bags sac sex or bags containing certain substances inside right so this is the structure of an animal cell and we will discuss in more detail the structure and functions in the coming video lastly the structure of a plant cell right so as i said you have to draw know how to draw the mitochondrion golgi apparatus and so forth so you can i suggest that you draw the structure of an animal cell and plant cell as is seen here because this diagram is well drawn for you okay with the accurate uh drawing of the structures and the various structures like rough endoplasmic reticulum smooth endoplasmic reticulum and so forth okay so you can draw the structure of the plant and animal cell the last two slides here in your notebook now going on to the plant cell here what is the difference between the plant cell and animal cell okay plant cells have a few structures here that are not found in the animal cell okay but plant cells have some common structures like mitochondrion mitochondrion golgi apparatus rough endoplasmic reticulum nuclear smooth endoplasmic reticulum which are similar all these are same are found also in the the animal cell okay now what does a plant cell have that is not found in the animal cell plant cells have of course the chloroplast okay so the chloroplast is an organelle that's involved in uh the process of photosynthesis so it contains the pigments called chlorophyll to absorb sunlight and then convert the light energy into chemical energy which is thought in the food substances like glucose right so i put a star here to say that it is only found in the plant cell because animals cannot produce their own food they don't produce their own organic food substances through photosynthesis so they don't have chloroplasts okay now another structure that's only found in plant cells is the big central vacuum in the cell huh so this big vacuum is found in the matured plant cells and it consists of two parts the membrane surrounding the cell set inside is called torno plus and inside there is the cell set of fluid okay that contains water and mineral salts and so forth and also sugars amino acids so what's the function of this big vacuum in the plant cell it stores the water sugar mineral salts and mineral salts in the cell set and also when it is full of water the vacuum will press on the cell walls cell wall of the plant cell and make the plant cell become turgid or firm and hard so this will give support to the plant cell and also overall it gives support it gives support to the plant right now we'll find out more about the function of vacuola in the next lesson and lastly plant cells have something else i'll call the cell wall okay the outer layer called the cell wall which is not found in animal cells so the cell wall is made of cellulose okay which is a tough substance and cellulose is a type of polysaccharide right in the same group as starch and glycogen the polysaccharide made up of simple units of called the glucose glucose or glucose molecules so what is the function of the cell wall so it is rigid and tough so it helps to maintain the shape of plant cells so plant cells have a fixed shape for example a rectangular shape and the cell wall also provides support to the plant cells right okay so other than that the other organelles the function of the other organelles have been mentioned so plant cells have a big vacuum chloroplast and cell wall that is not found in animal cells the rest of the organelles that we've discussed are found both in plant cells and animal cells okay such as mitochondrion golgi apparatus rough endoplasmic reticulum nucleus smooth endoplasmic reticulum so that's all for this lesson do share like and subscribe if you find this lesson useful and we will meet again in the next video when i discuss about the i discuss the functions and the structure of the organelles in more detail so this is this topic is important for example usually comes out in the structured questions for spf goodbye for now and take care