Levels of Organisation PDF

Levels of Organisation HEA1091 Learning Objectives  Explain the structure and function of a human cell, with an emphasis on its clinical significance in maintaining homeostasis.  Describe the roles of specific cell organelles, particula...

Levels of Organisation HEA1091 Learning Objectives  Explain the structure and function of a human cell, with an emphasis on its clinical significance in maintaining homeostasis.  Describe the roles of specific cell organelles, particularly the nucleus, mitochondria, and plasma membrane, in the context of cellular injury and repair.  Analyse the processes of energy production within the cell (ATP production via cellular respiration) and its relevance to hypoxia and shock in pre-hospital care. rom Atoms To The Complete Organism 3 What Are We Composed Of? Organisation What elements are we composed of? 96% of humans are the 4 key ones:  C  H  O  N 4 Cells Organisation The human body begins as a single cell, known as the zygote, which forms when the female egg cell (ovum) and the male sperm cell (spermatozoon) fuse during fertilisation. Following this, the zygote undergoes multiple rounds of cell division. As the foetus develops, these dividing cells begin to specialise, taking on different structures and functions while all still containing the same genetic material as the original zygote. A typical cell is composed of a plasma membrane that surrounds and protects the cell’s contents. Inside the cell,5 Basic components of a cell Nucleus Cytoplasm Membrane Endoplasmic reticulum Lysosomes DNA Phospholipi Golgi Centrosome d bilayer apparatus Nucleolus Fluid Mosaic Golgi Body Ribosomes Cytoskeleton The cell components Organisation Organelles bingo. Mark the organelles off as you encounter them! Nucleus Cytoplasm Lysosomes Ribosomes Nucleolus Golgi Apparatus Rough Endoplasmic Cell membrane Mitochondria Reticulum Smooth endoplasmic reticulum Vesicles Cytoskeleton Cytosol 7  u s e ol Cell Membrane l uc N Nucleus Ro Golgi Apparatus u gh Re End Cy Vesicles l tic op o to s ul l a t o um sm sk ia d r Cy i c el on h n et c i to o M Cytoplasm m e so o i b Lysosomes R s Smooth Endoplasmic Reticulum The plasma membrane is essential for the survival of the cell because it controls what substances enter and leave, keeping the internal environment stable. The plasma membrane is made up of two layers of phospholipids with proteins and sugars embedded in them. Cholesterol is also present in the membrane. Each phospholipid has a water- attracting (hydrophilic) head and a water-repelling (hydrophobic) tail. The phospholipids form a bilayer, with the hydrophilic heads facing outward and the hydrophobic tails inside, creating a barrier that influences what can pass through the membrane.  Cell Transportation In the last session, we explored passive transport. Now, let's dive deeper into facilitated and active transport. Particle size is important, as many small molecules, e.g. water, can pass freely across the membrane by simple diffusion, while large molecules cannot and may therefore be confined to either the interstitial fluid or the intracellular fluid Pores or specific channels in the plasma membrane allow certain substances to pass while blocking others. Even though the green and yellow particles are the same size, the membrane has channels that only permit the green particles to pass, excluding the yellow ones. Some substances, like glucose and amino acids, cannot diffuse through the semipermeable membrane on their own. Instead, they rely on specialised protein carriers in the membrane, which bind to specific substances in a lock-and-key fashion. Once bound, the carrier changes shape and releases the substance on the other side. Each carrier is specific to one substance, and because there are a limited number of carriers, only a certain amount can be transported at once—this is known as the transport maximum. Sodium Potassium Pump All cell membranes have this pump, which indirectly supports other transport mechanisms, like glucose uptake, and maintains the electrical gradient necessary for generating action potentials in nerve and muscle cells. This pump uses active transport to keep sodium (Na+) and potassium (K+) concentrations unequal across the membrane, consuming up to 30% of cellular ATP. Potassium is the main intracellular cation, and sodium is the primary extracellular cation. K+ tends to diffuse out of the cell, while Na+ diffuses in, so the pump continuously expels excess Na+ in exchange for K+ to maintain these gradients. Although we're skipping this section today, don't forget to come back to it —it'll be your secret weapon when exam time rolls around!  Nucleus All human cells, except mature red blood cells, contain a nucleus. Some cells, like skeletal muscle cells, even have multiple nuclei. The nucleus is the largest organelle in the cell and is enclosed by the nuclear envelope, a membrane similar to the plasma membrane but with small pores that allow certain larger substances to move between the nucleus and the cytoplasm. The nucleus controls the cell’s metabolic activities and houses the body’s genetic material, DNA (deoxyribonucleic acid). In a non-dividing cell, DNA exists as a network of fine threads called chromatin, which condenses into chromosomes when the cell is preparing to divide. Additionally, the nucleus contains a small amount of RNA (ribonucleic acid), which is involved in protein synthesis. Inside the nucleus is a spherical structure called the nucleolus. It plays a key role in producing and assembling ribosome components, which are responsible for synthesizing new proteins. Ribosomes Ribosomes are tiny granules made up of ribosomal RNA and proteins. They create proteins from amino acids, using messenger RNA (mRNA) as a guide. When ribosomes are found free-floating or in small clusters in the cytoplasm, they produce proteins for use inside the cell, such as enzymes needed for cellular metabolism. Ribosomes are also attached to the outer surface of the nuclear envelope and rough endoplasmic reticulum, where they produce proteins for export outside the cell, like some hormones. Endoplasmic Reticulum The Endoplasmic Reticulum (ER) is an extensive network of interconnected membranous canals found within the cytoplasm. It exists in two forms: smooth and rough. The Smooth ER plays a key role in synthesizing lipids and steroid hormones, many of which are essential for maintaining and repairing the plasma membrane, as well as the membranes of various organelles. Additionally, the Smooth ER helps detoxify certain drugs and facilitates the conversion of glycogen to glucose when the cell requires energy. On the other hand, the Rough ER gets its name from the ribosomes attached to its surface. These ribosomes are responsible for synthesising proteins, some of which are destined to be secreted from the cell. For example, enzymes and hormones are  Golgi apparatus The Golgi apparatus is composed of stacks of closely folded, flattened membranous sacs and is found in all cells, though it is more prominent in cells that specialize in synthesizing and exporting proteins. Proteins produced in the Endoplasmic Reticulum (ER) are transported to the Golgi apparatus, where they undergo further processing and are packaged into membrane-bound vesicles. These vesicles are then stored until needed. When the cell requires the release of these proteins, the vesicles move to the plasma membrane, fuse with it, and expel their contents outside the cell in a process known as exocytosis (the process by which cells release substances to the outside by merging a vesicle with the cell membrane).  Lysosomes Lysosomes are small, membrane-bound vesicles that bud off from the Golgi apparatus. They contain a range of enzymes responsible for breaking down larger molecules, such as RNA, DNA, carbohydrates, and proteins, as well as cellular debris and fragments of organelles. These molecules are broken down into smaller components that can either be recycled for reuse by the cell or expelled as waste. In certain cells, like white blood cells, lysosomes also play a crucial role in digesting foreign materials, including harmful microbes, helping to defend the body against infection.  Cytoskeleton The cytoskeleton consists of an extensive and dynamic network of tiny protein fibres, including microfilaments, intermediate filaments, and microtubules. This intricate framework provides structural support for the cell, helping to maintain its shape and stabilizing the position of organelles within the cytoplasm. Beyond its structural role, the cytoskeleton is essential for intracellular transport, guiding the movement of materials such as vesicles, proteins, and organelles throughout the cell. Additionally, it plays a critical role in processes like cell division, enabling the separation of chromosomes, and in cell motility, facilitating changes in shape and movement in response to the environment.  Nucleolus The nucleolus is a dense region within the nucleus responsible for producing and assembling ribosomes, which are essential for protein synthesis. It creates ribosomal RNA (rRNA) and combines it with proteins to form ribosomal subunits, which are then sent to the cytoplasm to build functional ribosomes. The nucleolus plays a key role in cell growth and division, as ribosomes are critical for protein production. Its function is vital in tissues with high protein synthesis demands, such as muscle cells, and in systems like the immune system, where rapid cell production is necessary for responding to pathogens.  Vesicle A vesicle is a small, membrane-bound sac that transports materials within and outside the cell. Formed by the budding of membranes from organelles like the endoplasmic reticulum (ER) or Golgi apparatus, vesicles carry proteins, lipids, and other molecules. They are vital for processes such as secretion, where substances like neurotransmitters or enzymes are released, and for digestion, as lysosomes (a type of vesicle) break down waste or pathogens. Vesicles also store molecules for later use and help maintain cellular organization. Their functions are crucial in systems like the nervous system for neurotransmitter release, the digestive system for enzyme secretion, and the  Cytoplasm The jelly-like substance in which the organelles are suspended, known as cytoplasm, is composed of a mixture of water, ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste products. This complex environment provides the necessary medium for biochemical reactions and nutrient transport, supporting cellular function and maintaining homeostasis within the cell. The cytoplasm’s diverse composition enables it to serve as a reservoir of essential molecules, facilitating processes such as energy production, metabolism, and the removal of waste, all while Mitochondria Mitochondria are membrane-bound, sausage-shaped organelles often referred to as the "powerhouses" of the cell due to their critical role in energy production. Their structure includes a double membrane, with the inner membrane folded into structures called cristae. These cristae are densely packed with enzymes responsible for synthesising adenosine triphosphate (ATP), the cell’s primary energy currency. ATP releases energy when broken down, fuelling various cellular processes. The synthesis of ATP is most efficient during the final stages of aerobic respiration, a process that depends on oxygen. Cells that are highly metabolically active, such as liver cells, muscle cells, and spermatozoa, contain the highest number of mitochondria to meet their energy demands. Additionally, mitochondria play a role in other essential processes such as regulating Aerobic respiration Cellular respiration Organisation Split into 3 stages  Glycolysis – in cytoplasm  Krebs cycle – in mitochondrial matrix  Electron Transport Chain – Cristae (Folds of the inner membrane of mitochondria) of mitochondria 28  Imagine you're about to sprint for the bus. You see it at the end of the street, and you've got to move fast if you don't want to miss it. As you start running, everything feels fine at first—your legs are pumping, your breathing gets quicker, and you're powering through. But then, just as you're getting close, your muscles start to burn, and you feel that familiar ache in your legs. What's happening inside your body? Well, when you sprint, your body suddenly needs a lot more energy. Normally, your cells get energy by a process called aerobic respiration. This is the best way to make energy because it uses oxygen to break down glucose (the sugar in your body) and turns it into lots of adenosine triphosphate, or ATP—think of ATP as little energy packets your cells use to do everything. This process happens inside tiny power stations in your cells called mitochondria. Now, the catch with aerobic respiration is that it takes a bit of time and requires oxygen, which you get from breathing. When you're calmly walking, your body has no trouble getting enough oxygen to your cells to keep making ATP. But when you start sprinting, your muscles demand energy fast, and you can't breathe in enough oxygen quickly enough to keep up.  So, what does your body do? It switches to anaerobic respiration, a backup method that doesn't need oxygen. Instead of breaking glucose down fully into carbon dioxide and water (which happens in aerobic respiration), anaerobic respiration breaks it down into something called lactic acid. This process is quicker, but it's not as efficient. It only produces a little bit of ATP, which is why you can't sprint forever—you run out of energy quickly. And that lactic acid? That's what causes your muscles to ache after a hard run. Luckily, your body doesn't rely on anaerobic respiration for long. As soon as you stop running, you start breathing heavily, bringing more oxygen back into your body. This lets your cells switch back to aerobic respiration, which is a much better deal because it produces way more ATP and gets rid of waste products like carbon dioxide and water. Here's the cool part: aerobic respiration happens in three stages, and each stage takes place in a special part of the cell. The mitochondria, those little energy factories, are designed to make the most of every step of this process, using different environments inside the cell to make everything run smoothly. It's like having the perfect setup to get the biggest energy payoff possible from the food you eat.  ATP – The Cell's Energy Currency What is ATP? Full name: Adenosine Triphosphate ATP is a molecule that stores and provides energy for nearly all cellular processes. Structure of ATP ATP consists of: Adenine (a nitrogenous base) Ribose (a sugar molecule) Three phosphate groups linked together How does ATP work? ATP releases energy when the bond between its last phosphate group is broken. This transforms ATP into ADP (Adenosine Diphosphate) + inorganic phosphate (Pi), and energy is released. Role of ATP in the body: Provides energy for: Muscle contractions (important in paramedics' context, e.g., heart muscle) Active transport (moving substances across cell membranes) Chemical reactions (building and breaking down molecules) ATP as a Renewable Resource ATP is continuously recycled in cells, going from ATP to ADP and back. Glycolysis Organisation Glucose enters the cell Glucose is a 6C molecule It splits into two 3C pyruvate molecules Once it is energised by ATPs phosphorylating it (molecule gains energy through the addition of a phosphate group from ATP) The Net ATP payoff is 2 ATP 2 electron carriers, called NADH are also formed Produces:  Pyruvate 34  It all starts with glucose—the sugar you get from the food you eat. Once glucose enters your cells, the first step in turning it into usable energy is called glycolysis. Think of glycolysis as the opening act of a concert—it's the first part of the whole process, and it happens in the cytoplasm, the jelly-like substance inside your cells. The cool thing about glycolysis is that it's the same whether there's oxygen around or not—it works in both aerobic and anaerobic conditions. Imagine glucose as a shiny golden coin. Glycolysis breaks that coin in half. To do that, your body has to spend a bit of energy upfront (like paying a toll), but don't worry—you get a bigger reward in the end. The glucose is split into two smaller molecules called pyruvate, and along the way, some energy is released in the form of ATP (adenosine triphosphate). ATP is like your cell's energy currency, and it goes to fuel all sorts of important cellular activities, like muscle contractions or even maintaining the balance of chemicals inside your cells.  In addition to ATP, you also get something called NADH, which stands for nicotinamide adenine dinucleotide (in its reduced form). NADH acts like a helper molecule or "energy carrier" that will be used later in a different part of the energy-making process (electron transport chain (ETC)). It's full of energy potential, and it will head to the mitochondria (if there's enough oxygen) to help make even more ATP during the next stages of cellular respiration. Now, you don't get a ton of ATP from glycolysis—just 2 ATP molecules for every glucose molecule that's broken down. It's not a massive energy payoff, but it's quick and easy, and your cells can do it without needing any oxygen at all. That's why glycolysis is so important. Even if you're in the middle of an intense sprint and can't get enough oxygen to your muscles, glycolysis is still there, working away to make sure you get some energy. Once glycolysis is done, your body has a choice to make. If you're getting plenty of oxygen—like during a nice jog or when you're at rest—the pyruvate moves into your mitochondria, where the rest of the energy-making process continues through aerobic respiration. This is where you get the big energy payoff with lots more ATP.  After glycolysis, you’re left with two molecules of pyruvate from each glucose molecule. Pyruvate is like the final product of glycolysis, but it’s not quite ready for the Krebs cycle yet. The Krebs cycle can only accept a specific form of molecule to start the process—acetyl-CoA. When pyruvate enters the mitochondria (the powerhouse of the cell), a process occurs. This involves three main things: 1. Carbon dioxide (CO₂) is removed from the pyruvate. This is the first release of CO₂ in the entire process of respiration and is something we exhale as waste. 2. NADH is produced during this conversion. Remember, NADH is an energy carrier that will be used later in the electron transport chain to generate more ATP. 3. The remaining part of the pyruvate molecule is attached to a coenzyme (helper molecules that work with enzymes to speed up chemical reactions) called CoA to form acetyl-CoA. Krebs Cycle The Krebs cycle is a series of chemical reactions that take place in the mitochondria, to produce energy-rich molecules, and a small amount of ATP, while also releasing carbon dioxide as a waste product.  The first thing that happens is that acetyl-CoA (product of breaking down pyruvate) is handed off to a molecule (oxaloacetate) to form a new molecule called citric acid (this is why the Krebs cycle is also known as the citric acid cycle). From here, the citric acid is broken down, bit by bit, through a series of chemical reactions. As citric acid goes through these changes, two important things happen: 1. Energy is released. This energy isn’t in the form of ATP just yet, but instead it’s captured by special carriers, NADH and FADH2 (flavin adenine dinucleotide). These molecules (NADH and FADH2) act like treasure chests, storing up energy that will be used later on in the final step of the cellular respiration process—the electron transport chain, where the real ATP payoff happens. 2. Carbon dioxide (CO₂) is released as a waste product. This is the same CO₂ you breathe out, and it’s essentially the leftovers from breaking down the original glucose. Every time the cycle turns (the Krebs cycle is a continuous loop), a couple of CO₂ molecules are kicked out, making room for more reactions. Now, the goal of the Krebs cycle isn’t to make lots of ATP right away. Instead, it’s about preparing those energy carriers (NADH and FADH2) for their final job, which will come later. Still, the cycle does give you a small reward in the form of 1 ATP molecule per turn of the cycle—not bad, but the big prize comes later. After citric acid is broken down and all the energy has been captured, the cycle ends where it began—with oxaloacetate ready to grab another acetyl-CoA and start the process all over again. It’s a continuous loop, working tirelessly inside your mitochondria to process the fuel from your food and get you the energy you need. Why Is It So Important? The real magic of the Krebs cycle is that it sets up the final stage of energy production. By creating NADH and FADH2 (energy carriers ), the Krebs cycle powers the next step: the electron transport chain, where those treasure chests of energy get opened, releasing a huge amount of ATP that your body can use for things like running, thinking, or even just breathing. So, the Krebs cycle is like the middle part of a journey—taking the raw materials from glycolysis (acetyl-CoA), extracting energy, and preparing your cell for the final ATP-making stage. It may not give you all the ATP right away, but it’s a crucial step in making sure your cells have the power they need to keep you going! Oxidative Phosphorylation Organisation This step provides the biggest ATP payoff in aerobic respiration! It is split into 2 steps: Electron transport chain Chemiosmosis 41 Electron Transport Chain (ETC) Organisation You’ve been on a journey to turn glucose into energy for your body. First, you went through glycolysis, where you broke down glucose into pyruvate, grabbing some ATP and energy gems called NADH along the way. Then, in the Krebs cycle, your body processed the pyruvate further, creating even more NADH and another energy carrier, FADH2. These two molecules are like your treasure chests filled with high-energy electrons. But now, it’s time to unlock the real power hidden in 42 them. Welcome to the Electron  Imagine this: you're now standing in front of a giant power plant, and inside it are a series of machines (protein complexes) working together. These machines are embedded in the inner membrane of the mitochondria—the powerhouse of the cell. Your NADH and FADH2 molecules are the keys to starting the power plant. Here's what happens next:  Back in glycolysis and the Krebs cycle, when your body broke down glucose, the processes didn’t just make NADH and FADH2—they also loaded them with something very important: high-energy electrons. These electrons are the real treasure, because it’s their energy that will eventually be used to make ATP. Your NADH and FADH2 molecules hand over their high-energy electrons to the first machine (Protein complexes) in the chain. These electrons are like little sparks of energy that jump from one machine to the next down the line. As they move through the chain, they release energy at each step. As the electrons hop from one protein complex to the next, the energy they release is used to pump protons (H+) from inside the mitochondria to the space between the inner and outer mitochondrial membranes (The mitochondria have two membranes: the outer membrane, which surrounds the organelle, and the inner membrane, which is folded to increase surface area. The inner membrane is where energy production happens.). This builds up a lot of protons (H+) outside, like a dam holding back water. You’re creating a proton gradient (more H+ ions outside the inner mitochondrial membrane than inside), a build-up of potential energy just waiting to be used!  At the end of the electron transport chain, the electrons need somewhere to go. They can't just float around forever. Luckily, there’s a solution: oxygen. Oxygen acts like the final electron acceptor, combining with the electrons and protons (Hydrogen) to form water (H₂O). That’s why oxygen is so important for cellular respiration—without it, the whole chain would get backed up and stop working. Now, with a bunch of protons built up on one side of the membrane, they want to flow back into the mitochondria to even things out. But they can’t just pass through anywhere—they have to go through a special enzyme (an enzyme is a protein that speeds up chemical reactions in the body) called ATP synthase. As the protons rush through this enzyme, it spins like a turbine in a dam, generating a ton of ATP! This is called chemiosmosis, and it’s the final step in making energy. By the time the Electron Transport Chain finishes its job, all the NADH and FADH2 you collected earlier have been used to create a large amount of ATP—far more than you got from glycolysis or the Krebs cycle. This ATP is the energy that powers everything you do, from thinking to running to breathing. Anaerobic respiration  Glucose still enters the cell  Still converted in Pyruvate lycolysis: First, glucose (a 6-carbon molecule) is broken down into two molecules of pyruvate (each a 3-carbon molecule) through a process called glycolysis ebs cycle/Citric Acid Cycle/ Tricarboxylic Acid (TCA) Cyc In this oxygen-deprived state, the cell still needs to produce energy, so it converts pyruvate into lactate (lactic acid) using the enzyme lactate dehydrogenase. This conversion helps regenerate a molecule (NAD+) needed for glycolysis to continue, allowing the cell to keep producing a small amount of energy.  Pyruvate into Lactate (Lactic Acid Lactate Dehydrogenase Glycolysis requires a constant supply of NAD+ to accept electrons and form NADH. During aerobic respiration, NADH is oxidised back into NAD+ in the electron transport chain. In anaerobic conditions, the electron transport chain isn't functioning efficiently due to the lack of oxygen. To keep glycolysis running, the conversion of pyruvate into lactate helps regenerate NAD+. This regeneration of NAD+ ensures that glycolysis can continue, and cells can still produce small amounts of ATP even without oxygen.  When lactate is produced during anaerobic respiration, H+ ions are also produced. Normally, the body can clear lactate and neutralise the extra H+, but if lactate levels rise too quickly or the body’s ability to clear it is compromised, these H+ ions accumulate in the blood. This increase in H+ ions lowers the pH of the blood, leading to a condition called acidosis, specifically lactic acidosis. It indicates that tissues are not receiving adequate oxygen, and prolonged oxygen deprivation can lead to tissue damage or death. Learning Objectives  Explain the structure and function of a human cell, with an emphasis on its clinical significance in maintaining homeostasis.  Describe the roles of specific cell organelles, particularly the nucleus, mitochondria, and plasma membrane, in the context of cellular injury and repair.  Analyse the processes of energy production within the cell (ATP production via cellular respiration) and its relevance to hypoxia and shock in pre-hospital care.