Integrated Science Notes 2024 Year 1 PDF

Integrated Science Notes 2024 Year 1 Chapter 5. Model & System – 5.1 Cell Structure & Function NAME TEACHER’S NOTES CLASS 1 INDEX NO. 1 Contents...

Integrated Science Notes 2024 Year 1 Chapter 5. Model & System – 5.1 Cell Structure & Function NAME TEACHER’S NOTES CLASS 1 INDEX NO. 1 Contents Page 5.1 Cell Structure and Function 5.1.1 The Cell Theory 7 5.1.2 Structure and Function of Cells 8 o Plant cell o Animal cell o Description of organelles 5.1.3 Specialised Cells 10 5.1.3.1 Cells in Unicellular vs Multicellular Organisms 10 5.1.3.2 Importance of Cell Specialisation 11 5.1.3.3 Examples of Specialised Cells 11 o Red Blood Cells o Root Hair Cell 5.1.4 Levels of Cellular Organisation 12 o Tissue o Organ o Organ System o Organism 5.1.5 Applying our Understanding to Today’s Context – Tissue and Organ 15 Transplant (IP only) 5.1.6 Stem Cells (FYI) 17 2  Unifying Ideas From Molecules to Organisms: Structures and Processes Cells are organised in specific ways to enable them to perform their function. Living systems at all levels of organization demonstrate the complementary nature of structure and function. Key Ideas Microscope drawings of cells are representations of what is observed. Models are used to represent cellular structures of plant and animal cells. Models serve as visualisation aids to explain functions of cellular structures. Models of typical plant and animal cells are used to represent their various forms. Models of typical plant and animal cells help us to infer the type of cell based on comparison of models with actual specimen. At the end of this topic, you will be able to: define cell theory identify structures of typical plant and animal cells from diagrams, photomicrographs and as seen under the light microscope using prepared slides and fresh material treated with an appropriate temporary staining technique: o chloroplasts o cytoplasm o cell membrane o cell vacuoles o cell wall o nucleus containing DNA o mitochondrion list the functions of the organelles identified above. compare the structure of typical animal and plant cells. infer whether an organism is an animal or a plant, based on its cellular composition show an understanding that typical plant and animal cells are models used to represent their various forms recognise that in multicellular organisms (e.g., plants and animals), cells are the basic building blocks state, in simple terms, the relationship between cell function and cell structure for the following specialised cells: o absorption – root hair cells o transport of oxygen – red blood cells differentiate between cell, tissue, organ and organ system. explain the significance of the division of labour, even at the cellular level 3 Introduction From the time of the ancient Romans, through the Middle Ages, and until the late nineteenth century, it was generally accepted that some life forms arose spontaneously from non-living matter. This process was termed Spontaneous Generation and was inspired by every day observations: maggots generated from rotting meat mice are generated from sweaty underwear and wheat eels, turtles are generated from sea sediments People thought that it was a natural phenomenon, what we call a fact: in rotten food we find maggots. There was an explanation to that fact, what we call a hypothesis: rotten food generates maggots. Francesco Redi (Italian physician and poet) doubted that hypothesis, because he had made an observation that added new information: around rotten food there are always flies. With the new information Francesco thought a new explanation (a new hypothesis) to why there were maggots in rotten food. He proposed that flies were doing something to the rotten food, and whatever flies were doing, made maggots appear on the food. He also proposed a way to see if this new explanation was better, a way to test it, an experiment. “if we allow flies to contact the rotten food we will see maggots appear…” “…if we stop them from contacting the food, maggots will not appear” Design of his experiment: He set up three equal bottles with meat inside: One bottle he would leave open. A second bottle he would seal with a cork to stop the flies from reaching the meat. A third bottle he would seal with a gauze, to let air pass but not flies. Because some people believed that whatever generated the maggots was in the air. 4  He then predicted what would be the expected results from his experiment. “If the meat is generating maggots by itself, I should see maggots in all the bottles” -he thought. “But, if the flies are responsible, then maggots will appear only in the open bottle”. He made the experiments and got the results he predicted. Maggots appeared on the meat the flies could get to and not on the ones they could not reach. From the experiments he concluded “omne vivum ex vivo” – all life comes from life. [Reference: https://sci-flies.com/spontaneous-generation/] Cell theory refers to the idea that cells are the basic unit of structure and function in living things. 5 Discovery of Cells – the First Microscope FYI The first time the word cell was used to refer to these tiny units of life was in 1665 by a British scientist named Robert Hooke. Hooke was one of the earliest scientists to study living things under a microscope. The microscopes of his day were not very strong, but Hooke was still able to make an important discovery. When he looked at a thin slice of cork under his microscope, he was surprised to see what looked like a honeycomb. Hooke made the drawing to show what he saw. As you can see, the cork was made up of many tiny units, which Hooke called cells. Hooke’s early microscope 300X Cork Cells. This was what Robert Hooke saw when he looked at a thin slice of cork under his microscope. Soon after Robert Hooke discovered cells in cork, Anton van Leeuwenhoek in Holland made other important discoveries using a microscope. Leeuwenhoek made his own microscope lenses, and he was so good at it that his microscope was more powerful than other microscopes of his day. In fact, Leeuwenhoek’s microscope was almost as strong as modern light microscopes. Using his microscope, Leeuwenhoek discovered tiny animals such as rotifers. Leeuwenhoek also discovered human blood cells. He even scraped plaque from his own teeth and observed it under the microscope. What do you think Leeuwenhoek saw in the plaque? He saw tiny living things with a single cell that he named animalcules (“tiny animals”). The figure below shows a brief timeline of the advances in microscope technology and how they have influenced our understanding of cells. The advances in microscope technology have deepened our understanding of cells. It enabled more things to be observed or seen within the cell, allowing for improved understanding of the cell. 6 5.1.1 The Cell Theory The Cell Theory is one of the fundamental theories of biology. For two centuries after the discovery of the microscope by Robert Hooke and Anton van Leeuwenhoek, biologists found cells everywhere. Biologists in the early part of the 19th century suggested that all living things were made of cells, but the role of cells as the primary building block of life was not discovered until 1839 when two German scientists, Theodor Schwann, a zoologist (studies animals), and Matthias Jakob Schleiden, a botanist (studies plants), suggested that cells were the basic unit of structure and function of all life. Later, in 1858, the German doctor Rudolf Virchow observed that cells divide to produce more cells. He proposed that all cells arise only from other cells. The collective observations of all three scientists form the Cell Theory, which states that: 1. all organisms are made up of one or more cells 2. the cell is the most basic unit of life 3. all cells come only from pre-existing cells 1. Every living thing is made of one or more cells. Living things are either unicellular (single cell) organisms or multicellular (many cells) organisms. Your body is composed of about 1014 cells. Amoeba (unicellular) Alga (multicellular – made of 4 cells!) Yeast cell (unicellular) Humans (multicellular) 2. A cell is the most basic unit of life. Cells make up the smallest level of a living organism such as yourself and other living things. All the life functions of an organism occur within cells. 7 3. All cells come only from pre-existing cells. In the mid-1800s, it became clear that all life must arise from pre- existing life — through reproduction. If cells are the fundamental units of life, they too must have a reproductive mechanism that maintains the amount of DNA (Deoxyribonucleic acid) in each cell. DNA contains the genetic instructions to make proteins. Reproduction is a characteristic of all living systems; because no individual organism lives forever, reproduction is essential to the continuation of every species. 5.1.2 Structure and Function of Cells All organisms are composed of cells—the fundamental unit of life. Most organisms are single cells, unicellular organisms. Other organisms, including humans, are multicellular. Multicellar and unicellular green algae Cells have many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to provide energy for the work that cells do and to make the materials that a cell or an organism needs. All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment. Scientist has formed a model of a generalized cell for both plants and animals. Cells have parts with specific functions: the nucleus, DNA, cytoplasm, cell membrane, and cell wall etc. Cells are very small so that materials such as nutrients and wastes can be exchanged efficiently between the inside and outside of the cell. Each living cell consists of a living material called protoplasm, which is made up of: nucleus and cytoplasm. Cytoplasm is jelly-like, containing mainly water. Both animal and plant cells contain sub-units called organelles. o An organelle is a structure in the cytoplasm in the cell. o Most organelles have a membrane surrounding it. 8  Fig 1 Drawing of a Generalised Animal Cell Fig 2 Drawing of Generalised Plant Cell Commented [GTMT1]: Students need to be able to describe the similarities and differences between a typical animal and plant cell in terms of what structures they have/do not have Read Science for Lower Secondary Textbook 1B, pages 38 -41 Organelle Description Commented [GTMT2]: Students need to know the function(s) of these organelles Thin outer layer that surrounds a cell Commented [GTMT3R2]: They also need to be able to Purpose: Regulates the movement of molecules in and out of the cell identify these organelles on a diagram Cell membrane Is partially permeable – only allows some substances to pass through it Protects the cell from its environment. Outer layer that surrounds the cell membrane in a plant cell. Made up of cellulose Cell wall (only in Purpose: Provides additional protection and support to the cell; giving a fixed plant cells) shape to the plant cell. Is fully permeable – allows all substances to pass through it The cell wall is stiff and rigid A jelly-like substance that fills the inside of cells Cytoplasm Purpose: It is where most cell activities occur Contains organelles and dissolved substances Where the cell's genetic information, or DNA, is stored Nucleus Purpose: Controls cell activities such as cell growth and repair This DNA is passed down from parents to offspring Small, oval shaped organelles Purpose: Breaks down food substances to release energy needed for cell Mitochondrion growth and reproduction. (Plural: Every type of cell has a different number of mitochondria. There are more Mitochondria) mitochondria in cells that have to perform lots of work and therefore need more energy, for example- your leg muscle cells, heart muscle cells etc. Contains green pigment called chlorophyll. Purpose: Convert sunlight (light energy), carbon dioxide, and water into sugars Chloroplast (only in (chemical energy). This process is called photosynthesis. The cell can then plant cells) transport the sugars to the mitochondria to release energy for the cell’s own use. A space within the cell enclosed by a membrane Purpose: Store food substances and water in the cell and they also facilitate Vacuole the removal of waste products. Plant cells usually have one large central vacuole. Animal cells have numerous small vacuoles. 9 5.1.3 Specialised Cells Cell Specialisation = Cells can be of different shapes, sizes and characteristics to adapt to perform their specific functions. 5.1.3.1 Cells in Unicellular vs Multicellular Organisms Not every cell in an animal or plant is identical. Your skin cell is different in shape and structure from your red blood cell. Both of them are also different from the generalised animal cells we just studied in the previous section. They all look different because they have different functions. We call these cells with a specific function, specialised cells. Their different structures help them carry out their functions. Unicellular organisms are made out of only one cell, so that cell does everything. It is not specialised. Multicellular organisms are made out of many cells. It is more efficient to have different groups of cells doing different functions (division of labour). Hence multicellular organisms have specialised cells. Difference between unicellular and multicellular organisms: Unicellular Organisms Multicellular Organisms Unicellular organisms, like bacteria, are able to Multicellular organisms need many different types of perform all life functions within one single cell. cells to carry out the same life processes. Each of these They can transport molecules, metabolize special types of cells has a different structure that helps nutrients, and reproduce within this one cell. it perform a specific function. Humans have many different types of cells with different jobs, such as blood cells that carry oxygen and nerve cells that transmit signals to all parts of the body. 5.1.3.2 Importance of Cell Specialisation Allows division of labour between different types of cells. The specialised cell becomes more efficient at its function, so the organism can perform multiple functions at the same time. 5.1.3.3 Examples of Specialised Cells 1 Red Blood Cells membrane haemoglobin depression due to the lack of nucleus – results in a biconcave shape Alga (multicellular) biconcave 10 Function: Transport oxygen from the lungs to all parts of the body. Explanation on how the structural adaptation helps Commented [GTMT4]: Students need to know what Structural adaptation structural adaptations the cells have, as well as how to the cell carry out its function explain the importance of the adaptation to the cell’s Allows it to bind to oxygen, enabling the transport of function contains haemoglobin (red pigment) oxygen to the rest of the body Able to store more haemoglobin, and therefore able has no nucleus to transport more oxygen Increases surface area to volume ratio, increasing rate circular and biconcave in shape of oxygen diffusion flexible and elastic membrane Able to squeeze through narrow capillaries 2 Root Hair Cells Function: absorb water and mineral salts from soil into the root of a plant. Explanation on how the structural adaptation helps the cell Structural adaptation carry out its function Increases surface area to volume ratio, to absorb water and long narrow extension mineral salts at a higher rate releases more energy for the root hair cell to absorb mineral numerous mitochondria salts 11 The following shows some other types of specialised cells found in humans. Commented [GTMT5]: The main specialised cells students should know at this level are red blood cells (animal cell) and root hair cells (plant cell). The rest is extra information in case they’re interested 5.1.4 Levels of Cellular Organisation Commented [GTMT6]: Students need to state: why cellular organisation is needed in multicellular organisms We have seen how multicellular organisms are made up of many different types of specialised cells with the levels of cellular organisation (cells-tissues-organ- different functions. organsystem-organism) These cells must all coordinate with each other to sustain life. identify which level a structure in the body belongs to (e.g. given an image of blood, they should be able to identify it Hence, cells are organised in a manner that allows them to work together for the organism to survive: as an tissue) a. Cells that perform the same function work together and form a tissue b. Tissues that perform different but related functions work together to form an organ c. Various organs work together to form an organ system d. Several different organ systems make up an organism This is called cellular organisation. It shows how cells (the basic unit of life) are organised in a multicellular organism Tissues Definition: A tissue is a group of cells with similar structures which work together to perform a specific function. Example: a group of muscle cells form muscle tissue; red blood cells and white blood cells form blood, which is a tissue. Organ Definition: An organ consists of more than one type of tissue working together to perform a specific function. Examples: heart, stomach, brain, lungs, kidneys, leaf and roots in plants Organ system Organ system: An organ system consists of a group of organs working together for a common purpose. Examples: circulatory system. transport system, respiratory system, excretory system, reproductive system Organism Various systems together make up the entire body of an organism. 12 Examples of cellular organisation in humans 13  All systems make up the organism and are interdependent. Commented [GTMT7]: picture on top shows the various organ systems that make up a human (an organism) cell tissue organ system organism Read Science for Secondary Textbook 1B, pages 42 - 46 14 5.1.5 Applying our Understanding to Today’s Context - Tissue & Organ Transplant [For IP only] A transplant is an organ, tissue or a group of cells removed from one person (the donor) and surgically transplanted into another person (the recipient or host) or moved from one site to another site in the same person. Transplants – such as a liver transplant – can save lives. They can also restore function to improve quality of life. For example, transplanting the clear tissue that covers the eye (cornea) is not necessary for life, but can restore sight. The donated organ may be from a deceased donor, a living donor, or an animal. In some cases an artificial organ is used. Living organ donation involves the donation of one of a paired organ (such as kidneys) or a portion of an organ (such as a lobe of the liver or lung). The donor's organ system is still able to function after the donation. Living donors are often related to the patient, but that is not always the case. Transplants can be for: organs – heart, kidney, liver, lung, pancreas, stomach and intestine tissue – cornea, bone, tendon, skin, pancreas islets, heart valves, nerves and veins cells – bone marrow and stem cells limbs – hands, arms and feet. A skin graft is a common example of a transplant from one part of a person’s body to another part. A transplant between two people can cause a rejection process where the immune system of the recipient or host attacks the foreign donor organ or tissue and destroys it. To reduce the risk of rejection of the donated organ, the recipient will probably need to take immunosuppressive medication for the rest of their life. What about blood? Can we donate blood? Will there be rejection? Hospitals are always looking for donors for blood, platelets and bone marrow cells as the donor can still lead a healthy life after the donation of these cells and tissues. 15 Ethical Issues Commented [GTMT8]: IP should be able to debate the ethical issues surrounding organ/tissue transplants. More information from the TB is given in the next few pages The major ethical concerns regarding organ transplant stem from the issue of a shortage of organs. The number of patients on the waiting list for organ donation far exceeds the number of available donors. The shortage of organs available for transplant gives rise to moral and ethical issues surrounding the procurement and distribution organs: Should those who have a better chance for survival be given priority over other patients needing organ transplants? Should parents of young children be given priority? Should those whose lifestyle choices (smoking, drinking, drug use, obesity, etc.) damaged their organ(s) be given the opportunity of an organ transplant? Should incentives, either monetary or non-monetary, be offered in order to encourage organ donation? Should those who made the decision to donate organs of a loved one who has been declared dead receive any kind of financial compensation? Does “transplant tourism” – the concept of traveling to developing countries to obtain organs exploit the poor and what does this mean for distributive justice? Should prisoners on death row be given the option of donating organs upon their death, or even be offered the option of trading a kidney or bone marrow in exchange for a life sentence in prison without parole? 16 Science Textbook 2B Pg 71 & 72 17 18  FYI Stem Cells What are Stem Cells? Stem cells are the non-specialised cells that grow, divide, and mature into all the other specialized cells in our body. There are a few different types of stem cells that get most of the attention. Embryonic stem cells are found in embryos at a very early stage (less than a week old). These cells can either create more stem cells, or turn into any other type of cell in the body. This makes them very valuable and important for research and stem cell treatments. Adult stem cells are found in much smaller numbers throughout the body’s tissues. Scientists originally believed that adult stem cells could only replicate into the same types of cells (for example, if you found them in bone marrow, they could only lead to blood cells), but that has since been proven wrong. Adult stem cells are less versatile than embryonic stem cells, but they can still be used to regenerate and heal other types of cells. 19  FYI The Wonders of Stem Cells (Enrichment) Although the process does seem rather strange, more fit for a sci-fi movie than a doctor’s office, stem cells have opened up a new world for medical research and alternative treatments. Imagine that you are suffering from heart disease, and things aren’t looking good for your future. Scientists can take the stem cells they have cultivated, inject them into the diseased tissue of the heart, and allow the stem cells to naturally replicate and heal the damaged tissues. This can be far more effective than any other invasive treatment, and far less risky. Stem Cell Transplants Bone marrow transplants can heal cells that have been damaged by chemotherapy, or those that suffer from autoimmune diseases, leukaemia, and other types of serious, life-threatening conditions. Diabetes has been known to decimate the pancreas, but stem cells could potentially regenerate those damaged tissues and reduce the life-threatening dangers of diabetes. Therapeutic Cloning One of the most recent and exciting developments in stem cell research is called therapeutic cloning. In therapeutic cloning, a nucleus is removed from an unfertilized egg and the somatic cell of a donor. The donated nucleus is put into the egg and allowed to divide – forming a blastocyst. This creates a line of pure stem cells that are identical to the genetic code of the original egg. Source: http://stemcells.nih.gov/info/basics/1.htm 20  FYI Monozygotic (identical) twins are natural clones. Clones contain identical sets of genetic material in the nucleus—the compartment that contains the chromosomes—of every cell in their bodies. Thus, cells from two clones have the same DNA and the same genes in their nuclei. Dizygotic(fraternal) twins are not natural clones. They do not share the same genetic materials. 21