Pathophysiology: Basics Lecture #1 PDF

Pathophysiology: Basics Lecture #1 Critical pathological processes at cell and tissue level.  The study of cells Basic structural and functional units of living organisms. Understanding cell biology is crucial as it form the foundation for comprehending various physiological...

Pathophysiology: Basics Lecture #1 Critical pathological processes at cell and tissue level.  The study of cells Basic structural and functional units of living organisms. Understanding cell biology is crucial as it form the foundation for comprehending various physiological and pathological processes in the human body.  Understanding the cell structure is crucial for understanding disease mechanisms and how cells communicate and collaborate within a system. Cells transmit, receive and interpret and use messages in various ways to ensure highly specialized cellular function. Well differentiated cell which resemble and effectively work together support the organisms integrity. When cells become less differentiated due to injury or mutation or communication breaks down theres injury or theres diseases like cancer. Each cell is a self contained system that undergoes the function of energy production and usage. Respiration, reproduction, and excretion Cells join together to form tissues, tissue, tissues join together to form organs and organs form body systems. To understand how organisms or organs and systems of the body work you really have to first understand the cell as your body is just a collection of individual cells doing highly specialized and similar functions.  Three theoretic tenents regarding cells^ 1. Cell is living entity  There are different domains of life There are 3 primary domains of life These domains of life are three distinict groups of organisms Distinct in cellular structure, genetic makeup, and evolutionary history. Bacteria and archea are prokaryotes - their cells don’t have nucleus. Cyanobacteria live in the water. Archea – one in particular are halophiles which live in hot water Eukaryotes do have a nucleus. This a genetic tree. Eukaryotes are the most familiar to us such as animals, fungi and plants. Proyarotic cell Simple Small Lack true nucleus No distinct nucleus Single circular chromosomes Lack membrane bound organelles – eukaryote cells have organelles that are membrane bound in prokaryotes they are not. They lack histones – which are proteins in eukaryotic cells which help organize and regulate DNA in the nucleus. Typically quite small 0.1-5 um. Larger than prokaryotes. The differences between prokaryotes and eukaryotes result in differences in their biochemical activities so the way that they reproduce, the way they create proteins, transport material across the cell membrane and the enzymes they create. The cells in our body always in motion and at work. Some of the things that can effect the number of human cells include the cell size and it’s function.  So cells vary greatly in size and function. For example red blood cells are very small and numerous while Neurons are large and powerful but much fewer in number. The number of cells in humans also depends on their cell turnover. So different cells have different lifespans and turnover rates. For example, red blood cells are replaced about very 120 days while some brain cells can last a lifetime. Finally tissue and organ specificity impacts the number of cells. So each tissue and organ type has a specific composition of cell types that contribute to it’s function so that will be reflected in the number of cells it has. Correct; B C is incorrect as bacteria are generally much smaller than animal cells (generalization)  Cells become specialized through the process of differentiation or maturation. So some cells eventually perform one kind of function ando ther cells perform other functions Cells with higly developed function such as movement often lack other properties. For example hormone production which is going to be more highly developed in other cells. So the cellular function that gets differentiate or specialized is done through a process of maturation and there are several functions. Movement – muscle cells can generate forces that produce motion. Muscles that are attached to bones produce limb movements. Muscles that enclose hollow tubes or cavities also move or empty contents when they contract. For example, the colon - so that’s smooth muscle – these are district maturated movement cells. Conductivity – is the chief function of the nerve cells, a stimulus creates an electrical potential across the cell membrane that is then propagated to other cells and cellular components. A third function is metabolic absorption, so all cells can take in and use nutrients and other substances from their surroundings but some cells are more specialized to take in greater number or variet of substances (kidney cells or epithelial cells of small intestine). Secretion – certain cells like mucus gland cells can synthesize new substances from substances they absorb then they secrete these new substances to be used elsewhere – think of your mouth that secretes saliva from muscus glands which then helps with digestion of food. Excretion – all cells create waste products that result from metabolic breakdown of nutrients, lysosomes are membrane bound sacs inside cells,  these contain enzymes that break down or digest large molecules and turn them into waste products that are then released from the cell. Respiration – cells absorb oxygen which then used to transform nutrients into energy in the form of ATP or adenosine triphosphate. Cellular respiration or oxidation occurs in the organelles called mitochondria. Reproduction – tissue growth occurs as cells enlarge and reproduce and even without growth, tissue maintence requires that new cells are produced to replace cells that are lost normally through cellular death. Nowever not all cells are capable of continuous division. !!! So not all cells can reproduce Communication – it is vital for cells to survive as as society of cells. Appropriate communication allows the maintence of.a dynamic steady state or homeostasis. It allows for messaging and retrival of messaging so cells can work in conjuction and carry out functions as a whole. So some of these specialized functions are important to create specialized tissues that allow your body to do specialized activity. Some of the functions are shared by all cells and then some functions are for example, muscle cells can produce an activity that other cells cannot. CORRECT: D - Only some cells like mucus gland cells secrete – Only some cells can produce movement (muscle cell) Only some cells are capable of continuous reproduction Therefore correct answer is D – metabolic absorption as all cells can take in and use nutrients and substances but not all cells can absolutely do those other activities. Correct answer is D Cells do indeed communicate with eachother directly through various mechanisms such as chemical signals and irect cell to cell contact which is a critical function for maintaining homeostasis and coordinating cellular activities. The other statements are correctly describing common functions of cells, including energy generation, production and movement.  This is a human cell Fundamental features of eukaryotic human cell is… 1. the plasma membrane on outside 2. The cytoplasm: where organelles float 3. The various intracellular organelles that facilitate cellular function One of the most important organelles.  Nucleus is the control center of the cell in plants, animals and other complex organisms. Nucleus is surrounded by a double membrane and it houses the cell’s genetic material - the DNA which contains instructions for how the cell functions and how the cell grows. Its not just important of reproduction it is also important for the production, the scaffolding (provides an area for protein production), the instructions for creating proteins that enable the cell to do things. In the nucleus we have DNA organized into chromosomes. The nucleus is crucial of course for copying DNA so for DNA replication, and making RNA so transcription which further is important for producing proteins and folding proteins (they needa fold to function) which are vital for the cell to grow, carry out tasks effectively. So in simple terms its where the cell keeps it’s important instructions and manages the operation of the cell. The gel-like substance that fills interior of cells and surrounds all the organelles like nucleus. Primarily composed of water, salt, and proteins. Provides medium for chemical reactions and organelle movement within the cell. Many essential processes of cellular metabolism such as protein synthesis and energy production occur in the cytoplasm. It also serves as a scaffold for the cell’s structural components and helps maintain the cell shape and integrity of the cell.  Essentially the cytoplasm is the bustling environment where various cellular activities take place and it’s essential for the cell survival and function. Ribosomes are very tiny but crucial cellular structure responsible for protein synthesis in all living organisms. These can be found floating freely in the cytoplasm or attached to the cytoplasmic reticulum. They are composed of RNA (read mrna and link amino acids together) and protein molecules (the subunits). Ribosomes interpret all the genetic instructions from your mRNA and they assemble amino acids into proteins through a process called translation. So in order to produce proteins you have to read the DNA on your chromosomes, create a copy of that DNA called mRNA and then you have to translate the mRNA into a protein which is basically folding your unique pattern of amino acids into a protein. And the process of doing that activity is facilitated by ribosomes. Therefore ribosomes are critical for the production of every protein that’s made, this fundamental role makes ribosomes essential for growth, repair, and maintence – essentially everything that’s done in a cell. Their activity is very tightly regulate to ensure proper protein production according to the cells needs and it influences various biological processes and functions within an organism (growth,development and stress responses). Endoplasmic reticulum – complex network of membranes and they fold back and forth on one another. They are found in eukaryotic cells. There is rough ER and smooth ER  Rough ER is studded with ribosomes all over its surface. And this primarily involves protein synthesis and modification – so they play a crucial role in folding newly synthesized proteins and preparing them for transport to other parts of the cell. The smooth endoplasmic reticulum doesn’t have ribosomes but it’s involved in lipid synthesis so our fats, detoxification of drugs and toxins and also calcium ion storag. So together the endoplasmic reticulum functions as a very dynamic interconnected system that supports cellular processes, particularly ensuring protein production in the rough ER and maintaining cellular homeostasis thorugh lipid synthesis and detoxification in the smooth endoplasmic reticulum Golgi complex – golgi apparatus – vital organelle in eukaryotic cells (not in prokaryotes) responsible for: Responsible for modifying, sorting, and packing proteins and lipids into tiny vesicles for transportation to their final destination either within the cell or outside of it. So thinking of the ribosome as the synthesis and folding – the production of the protein along with rough ER. With assistance of golgi apparatus – packages them into vesicles for transport elsewhere. Golgi apparatus consists of series of flattened membrane bound saces called cisternae.and they are organized into different functional regions – the cysts, the medial, and the trance. So golgi apparatus receive newly synthesized proteins form rough ER or lipids from the smooth er, they then undergo post-translational modifications. So when a protein is created it is created in what we call its rough form and then the golgi apparatus sometimes makes additional modifications. For example: glycosylation so we may add a sugar group to these proteins or whatever they are needed. And then they are sorted into different vesicles and delivered either to other cellular organelles within the cell or transported outside the cell by secretory vesicles which are basically little receptors that spit out or secrete proteins extracellularly. In addition to the golgi’s role in protein and lipid processing the golgi apparatus also plays a critical role in synthesising complex carbohydrates and they form lysosomes. In summary, the Golgi apparatus relies on the cytoskeleton for its structure, function, and transport processes. Lysosomes are membrane bound organelles in animal cells. Lysosomes contain digestive enzymes. Digestive enzymes – hydrochloric acid in stomach, these enzymes are capable of breaking down various molecules – bio-molecules: proteins, lipids, carbohydreates and nucleic acids. Lysosomes really serve as the cell’s digestive system they are the stomach and play a role in disposal of cellular waste, recycling of cellular components, and digesting material that are engulfed by the cell through phagocytosis. Lysosomes are obviously essential for maintain cellular health by ensuring proper nutrient recycling and eliminating any harmful substances. So it contributes to cell function and surivival..  Powerhouse of eukaryotic cells Generate energy Energy in cells is adenosine triphosphate Generating ATP occurs through aerobic respiration Mitochorina have double membrane structure like nucleus wit ha inner membrane that has folds called cristae allowing for large surface area in small space which is useful for energy production. Each of these folds allow more surface area to produce ATP. Mitochondria contain their own DNA and ribosomes so that suggests in evolutionary biology there may be semi-autonomous, their origins could have derived from an ancient symbiotic relationship with bacteria. Apart from energy production, mitochondria are involved in regulating cell membrabolism (regulating what happens in cell because it provides energy for those things to be done), Mitochondria is important in calcium signaling and apoptosis is programmed cell death. Mitochondria have crucial role in energy conversion which makes mitochondria essential for proper function and survivala of the cell and influencing the physiological processes in organisms. - Network of protein filaments found in the cytoplasm cells and the cytoskeleton provides structural support of the cell and enables cell movement and shape. Three main types of filaments : microtubules, actin filaments/microfilaments, and intermediate filaments. Microtubules maintain cell shape, form the mitotic spindle during cell division and serve as track for intracellular transport. Actin filaments or microfilaments involved in cell movement and contraction and support for processes like muscle contraction and cell divisions Intermediate filaments provide mechanical strength and stability and particularly in tissues subjected to mechanical stress. So some tissues in the body have more microtubules vs microfilaments vs intermediate filaments. C. Mitochondria is correct Mitochondria have the metabolic machinery necessary for cellular energy metabolism, the enzymes for therespiratory chain, electron transport chain is found in the inner membrane of mitochorina remember all the folds and that generates most of the cells ATP Also known as the cell membrane  Thin semi-permeable membrane that surrounds the cell. And particularly the cytoplasm Bounfary between inteori and exterior enviornemnt of cell. It is the wall and controls movement of substances into and out of cell. Palsma membrane composed of phospholipid bilayer Has embedded proteins and cholesterol molecuels to contribute to its structure and function Many roles of protein: Embedded proteins can act as receptors, faciilate transport molecuels across membrane, cell signaling, maintaining cell shape or stability, overall plasmam membrane plays a critical role in regulating cellular processes and maintain homeostasis within the cell. It controls what gets in and what comes out. Cellular membrane made of phospholipids – they have hydrophilic and hydrophobic properties. This allows membrane to act allows membrane to act as a barrier to natural diffusion of water. Proteins embedded on either side of the membrane or through membrane have many important functions. Lipid rafts are specifically defined by their enrichment in cholesterol and sphingolipids, which differentiate them from other regions of the cell membrane that are primarily composed of phospholipids. While phospholipids are the main components of the cell membrane, lipid rafts are unique microdomains that have a distinct composition and play specialized roles in various cellular functions. We learn about cell biology as Conditions on a macro scale like disease processes occur from alterations in very micro processes In the cells – things that go wrong in cells. A lot of times it comes down to a protein issue in a singular cell or across an organ. As we go through functions of proteins keep in mind what might happen if one of these ceases to exist. Protein FUNCTIONS: 1. Transport/transport channel : proteins facilitate the movement of ions, molecules and larger substances across the membrane through channels, carriers, or pumps. What would happen in the heart if a protein was unable to move ions? Think of potassium and sodium across the cellular membrane, the electrical conductivity of the heart would stop and of course you would experience a pathological likely fata process of the heart. Another function is cell recognition, it is extremely important that cells are able to recognize and identify themselves and that they are a part of their body’s own tissue as well as foreign cells. This is crucial for immune response and tissue development. So think of what might if a cell is unable to recognize itself so think of autoimmune disorders in this case if cell cant recognize itself and continue its functioning this becasue the cell wont preform its normal function if it doesnt recognize themselves and immune system sees them as foreign and destroyed them. Signal transduction: proteins receive signals from the cell’s environment or receive a signal from another cell and then transmit this signal into the cell because this allows the cell to intiate a response. If we didn’t have proteins (signal transducers) that can take signals from outside of cells and transmit them inside the cell to cause a response we would have cells acting alone in isolation and not working in a coordination with all the other cells of the organ. Enzymatic activity (proteins act as enzymes) so proteins serve as enzymes that catalyze chemical reactions at the membrane surface, So proteins then allow digestion of nutrients or synthesis of important molecules. So if your enzymes don’t work you are not digesting nutrients and not expelling waste and of course we know on a large scale what the problem with that is that is if you are not able to bring in nutrients or expel waste from the body. Cell adhesion: so proteins are important for binding cells together, of course cells tuck together make tissues and tissues stuck together make organs an what happens if we don’t have proteins that will bind than you cannot maintain structural integrity and facilitate communication so you literally don’t have tissue and organs that form and are stuck together – they cannot function as one. Cellular receptors are proteins that sit on the plasma membrane – on the outside, they cana also be in the cytoplasm and they can also bein the nucleus but what they do is they recognize and bind with other small molecules called ligands. So proteins can be receptors, they bindto ligands, the region that the ligand binds to on the receptor is called the ligand binding site. Ex. Hormones are ligands that bind to the protein receptor and then it initiates some cascade of events.  The recognition and binding process dependson the chemical configuration of the receptor and its smaller ligand and it hasto fit together kind of like a lock and key so not any ligand will bind to any receptor. There are numerous receptors found in cells and ligand binding to the receptor can activate or inhibit activity so it can activate activity via a biochemical pathway. So basically you take a lock which is the receptor, you add a key – the ligand and when those connect together you produceo r you activate or inhibit some biochemical process which results in an intracellular message which allow the cell to carry out some activity. A lot of times that will open some type of channel, or it will close a channel, etc. - Plasma membranes not only serve as the outer boundary of a cell but they also allow groups of cells to be held together and adhesed together – cell to cell adhesion. - Allows multiple similar cells to form tissues and multiple tissues to form organs. - Once all cells arranged in right way they become linked together: - Cells linked together by: o Cell adhesion molecules (proteins): these are in plasma membrane. o Extracellular matrix: space between the cells in a tissue (have proteins, and other molecules cells can all stick too keeping them close together) o Specialized cell junctions - These three ways are how cells physically attack to one another: o Crucial for maintain structure and facilitating communication so tissue and organ can act as one and it coordinates collective cellular behaviours. - Provides scaffold for cells to grow and move, allows ligands to travel to cells to signal them to promote differentiation and intracellular responses. - Tissues are not just cells all in one place, there is a material between tehm – the extracellular space is the space between cells, it is not empty space. - Extracellular matrix is the area around the cells, it is directly connected to the cells, it surrounds and holds the cells together in tissues. o It protects and supports the plasma membrane. - Fibroblasts are another organelle, a protein (maybe a cell?), which secretes the extracellular matrix. - The extracellular matrix contains glycoproteins, and other molecules – carbohydrates, sugars and an example are the protein collagen. o Collagen: a major component of the extracellular matrix that binds your tissues together. ▪ So we then think of what would happen if we are not able to produce collagen in the body (you need tissues to bind for wounds to heal) or we don’t produce it in sufficient amounts, or we think about the role of collagen in wound repair  - Collagen is important part of ECM so we don’t want to break it down. ▪ - We don’t want to promote inflammation and immune response activation for dry skin as it is not a wound. ▪ And we don’t want to inhibit angiogenesis and fibroblast proliferation – we want to fibroblast proliferation to happen as these proteins are very important to the cell membrane. ▪ The ECM contains hyaluronic acid so the answer is C. Hyaluronic acid is naturally occurring molecule. o It has a high-water binding capacity, found in the ECM and it keeps the skin moist which is essential for optimal conditions of healing, and it facilitates cell migration, prevents skin from drying out and supports enzymes involved in tissue repair. - Where cells come together we have different types of connection points. - We call these cell junctions. - Junctions typically talk about where two things come together so these are regions of cell membranes that come in direct physical contact with other cells of the same tissue. o Tight junctions ▪ Specialized junctions between adjacent cells, create a barrier that prevents the leakage of molecules between cells. This is where we want tightness, we want junction to be tight. ▪ Tight junctions are important in epithelial tissue where they maintain the integrity and polarity (different in internal envionrment and materials in the cell layers and outside the organ, prevent things from going into them) of the cell layers. Most organs of the body have a outer layer made of epithelial tissue which allows them a barrier to the organ itself, to more specialized tissue on the inside. o Desmosomes – anchoring junction, these hold adjacent cells together through intermediate filaments. ▪ Provide strong mechanical connections particularly in cells with high stress, high mechanical stress. I.e skin and heart muscles. ▪ Therefore, desmosomes anchor cells together that undergo high mechanical stress. o Gap junctions ▪ Channels between adjacent cells that allow for the nice passage of ions, small molecules and electrical signals and this is a simple form of coordinating activities of cells and tissues such as cardiac muscle and smooth muscle. So the tissue and organ is functioning as one as opposed to a delay in cascading a signal from one cell to the next. o Adherens Junctions ▪ Adherens junctions are protein complexes that bind adjacent cells together. They are anchored to the actin cytoskeleton within each cell, which provides mechanical strength and stability to the junction. o Hemidesmosomes – attach to cell intermediate filaments, connect cells to ECM. o Focal Adhesions – attach to cell actin filaments and connect cell to ECM. - Cells communicate through various mechanisms to coordinate activities and response to external stimuli. In image ligand binds to extracellular receptor. Add Ons to the points above: 1. Plasma membrane bound receptors - Specific molecules = ligands  2. Steroid hormones can pass through membrane due to hydrophobic nature. Bind to receptor causing cascade of events for example may act on DNA to change gene expression and lead to changes that cause production of proteins. Chemical signaling: - Paracrine signaling is when cells release ligands that act on nearby cells. o Same tissue, same type of cell that's nearby is acted on. - Autocrine signaling – cells respond to ligands that they themselves produce effecting their own behaviour - Hormonal signaling – endocrine cells release hormones into the bloodstream, and they act on distant cells that are targeted to specific organelles in the body. - Neurohormonal signaling – specialized neurons release hormones into the bloodstream to act as ligands on other cells.  - This shows 1. contact signaling via the plasma membrane bound receptors – cell close by gives a ligand), by signaling through secretion of molecules – so when cells create their own ligands that act on themselves or others, and then through gap junctions. - Receptor proteins can only response to specific signal molecules/ligands (lock and key hypothesis), when right ligand bind to receptor it tell the cell to do important task. (grow, make more cells, decide to live or die, change into different types of cells). - Basically like a cell getting a message telling it what to do. - A cell converts/transfuses an extracellular signal (the ligand binding to the receptor on plasma membrane) into a intracellular signal.  o This process initiates what we call a signalining cascade. It relays that signal into the interior, it amplifies it, and it distributes it during its transit. o The amplification of the signal is often achieved by stimulating enzymes and the steps in the cascade can be modulated by other things in the cell. - Different cell behaviours rely on these extracellular signals meaning the cell won’t do this activity unless it is told to via transduction from a ligand binding on the receptor. - Cellular metabolism is the sum of all the chemical reactions that are involved in maintaing cellular function. - It is just a word we give to describe all the reactions that occur inside of the cell. - Anabolism = energy using process of metabolism. Ana = upward, so this is the energy using processes of metabolism in which celluar structures are made. - Opposite of that is energy releasing processes known as catabolism, cata meaning downward, and catabolism occurs when celluar structures are broken down. o Metabolism provides the cell with the energy it needs to produce cellular structures (breaking down of nutrients like glucose creates ATP – catabolic, which then helps make cellular structures – anabolic). - Protein, fats, startches, carbohydrates, from food you ingest are hydrolyzed (broken/split by molecule of H2O). They break down into amino acids, fatty acids, glucose respectively and then they are absorbed and they are circulated and incorporated into the cell. - This is when they are used in the cell. They can be used for various vital celluar processes including the production of energy in the form of ATP. - ATP is basic unit of intracellular energy or fuel used by all cells. - Fuel/energy that drives all biological reactions necessary for cells to function. - Cellular function depends on cells ability to extract and then use the chemical energy in organic molecules. - When 1 mol of glucose metabolically breaks down into CO2 and water within the presence of oxygen – collects electrons at end of ETC (through cellular respiration), a total of 656 kilo cals of chemical energy is released. - So remember, no ATP, no energy, no work. - Our body is a big factory that turns the food we eat into energy to keep us moving all day. - Phase 1: digestion o When we eat food, our body breaks it down outside of our cell into small subunits and these are building blocks, they include protein, fat, and sugar (polysaccharides). - Phase 2: glycolysis o Inside our cells these building blocks are broken down into substance called pyruvate in the cytoplasm (gel – like subsstance inside the cell). o Pyruvate is changed into acetyl CoA. o This step doesn’t require oxygen – anerobic. o Small amount of energy (ATP formed). - Phase 3: Citric Acid Cycle o Happens in mitochondria – tiny energy factories o Acetyl CoA joins with other molecules in a cycle that produces a ton of energy particularly when there’s plenty of oxygen. ▪ Kreb cycle makes a ATP and multiple NADH that go to electron transport chain. ETC This process that uses oxygen is called oxidative phosphorylation (energy from e- that transfer from NADH to proteins in ETC create H+ gradient that provides energy for the transfer of ADP to ATP. o This process spits out waste products like CO2 which is then taken out of our body when we breathe– kreb cycle. ▪ Oxygen is final electron receptor when electrons travel through all proteins in ETC causing the H+ to travel across proteins and make a gradient, if no O2 then electrons would saturate the final protein and  more e- cannot enter the ETC and cause ATP formation. O2 excepts electrons and joins with H+ to make H20 o This whole process produces a lot of ATP. - This shows the phases of catabolism which leads from food to waste products. - These reactions produce our ATP which is used to power all other processes in the cell. - Transport across the membrane - This is how materials come into the cell and are removed from the cell. - When it mentions proteins above in transporters it is basically referring to ions/ligands that specifically fit in binding sites on receptor proteins. - Electrolytes account for about 95% of solutes in body fluids and they can be positively charged (cations) or negatively charged (anions). - PASSIVE TRANSPORT - One side has high conc. Of substance and an area with low, naturally its going to want to reach a place of homeostasis so of course these molecules move naturally without any energy from an area of high to low in an effort to balance concentration on either side of the membrane. - ACTIVE TRANSPORT o Requires energy in the form of ATP to drive molecules from areas of low concentration to high concentration. MY THINKING o Transport pupms actively pump substance from one side of the cell to other side. o Endocytosis – taking substances into the cell. Endo – in, cytosis = cytoplasm o Exocytosis – exiting the cytoplasm, so expelling substances from the cell. - Rate of diffusion = how quickly the solute moves from area of high to low concentration. Influenced by: - Difference of electrical potential across the membrane: so charged molecules will have a faster rate of diffusion if the opposite side of hte membrane has the opposite charge. For example if the inside of the membrane is more negative, when sodium channels are open, sodium will have a faster rate of diffusion as the membrane potentiatl on the inside is negative which attracts the sodium. - Or size of solute: smaller = quicker diffusion - If membrane is permeable to solutes then solute moves from hgih conc to low conc, however if membrane is permeable to water and not the solute then water moves from area of high conc/low solute conc, to low water conc/high solute conc. - Osmotic pressure is essentially the "pull" that a solution exerts on water molecules due to the presence of solutes. Another way of thinking: Osmotic pressure is the pressure needed by a solution to prevent water from coming into the solution? if more solute conc. more pressure is needed to resist the nature osmotic gradient of water into the higher conc. Solution. - Tonicity - ability of extracellular solution to make water move in our out of cell by osmosis. o Isotonic ▪ Solution with same solute conc, as inside of cell, no net movement of water. o Hypertonic ▪ Solution with higher solute conc. Then inside cell, water moves out of cell, cell shrinks, o Hypotonic ▪ Solution with lower solute conc. Than cell, water moves in cell, cell swells and may burst. - Therefore. Administering non-isotonic solutions may damage cells - Solute concentrations effect the flow of water in osmosis. A solution with a higher concentration of solutes has a high osmotic pressure. - Hydrostatic pressure: pressure of blood against capillaries/pressure of fluid against wall or membrane - Oncotic pressure or colloid osmotic pressure is the osmotic pressure due to the presence of proteins in solution for example plasma proteins, so higher plasma protein conc, is gonna cause a backward flow of water into capillaries for example.  - These relate to osmosis as the movement of fluid/water depends on which one of these forces are greater, the force of fluid on the wall of a membrane/capillariy or the protein conc. Inside the cell/capillary driving water back in. - Balancing hydrostatic pressure and solute concentration is very important in our vasculature, for example maintain our intracerebral pressure (we need fluid in and out of capillaries – colloid osmotic pressure and hydrostatic pressure to be balanced and this involves osmosis). - The majority of molecular transfer depends actually on specialized membrane transport proteins that span the phospholipid bilayer. They provide a private channel for certain molecules/select molecules - Membrane transport proteins occur in many forms that present in all cell membranes. - The transport is sometimes called active mediated transport. o This is in contrast to passive transport. - Most of these transport proteins allow select passage. o Ex. Passage of sodium ions but not potassium. - Each type of cell membrane has its own transport proteins that determine which solutes can pass in and out of the cell or organelle. - Importantly, they use direct energy – ATP.  - There are two main classes of membrane transport proteins o Transporters and channels. o These proteins differ in the type of solute that they transport. - A transporter is specific, it allows only ions that fit that unique biding site on the protein. The transporter undergoes what we call a confirmational change to enable membrane transport. So imagine a specific ion like Ca+ is in ECM and binds to transporter protein that spans the cellular membrane and it undergoes a confirmational change meaning it physically changes it shapes and allows the solute (ca) to pass through. - A channel when it is open creates a pore across the lipid bilayer. This allows ions or certain polar molecules to diffuse directly across the membrane. - Transport by a channel is dependent on the size and electrical charge of the molecule o So ion channels are responsible for the elecctrical excitability of nerve and muscle cells and play a critical role in membrane potential. ▪ Membrane potential allows our muscle cells, nerve cells, and heart to function and let it beat (ion channels create aciton potential and electrical conductivity of heart allowing it to beat). - Transport occurs through creation of vesicles. - Vesicle can be formed when we bring material into cell – endocytosis. o Cellular membrane wraps itself around the particle coming into the cell, pinches itself off and now we have a membrane-bound vesicle that is brought into cell.. ▪ If fluid – pinocytosis ▪ If large/solid particle – phagocytosis o Lysosome is organelle that attaches itself to the vesicle and breaks vesicle down, this release the particles to be used within the cell.  ▪ Ex. Used in glycolysis if it is being used in metabolism to produce ATP. ▪ If it’s a toxin it will be broken down, destroyed, and neutralized – this woudn’t impact cellular function. - Exocytosis – release contents of vesicle, for example release waste product of metabolism. o Vesicle you are going to remove from cell, the vesicle replaces cell membrane because it goes to edge of membrane, attaches itself and then spits out products into ECM. - Mediated transport is how substance passed into or out of cell through active function meaning it requires ATP. - ANSWER IS B o Active transport uses metabolic energy in form of ATP. o Other ones describe passive transport (diffusion, osmosis).  - Transport across cell membrane is important in generating electrical impulses particularly generating action potentials in the heart so our heart can beat. - Refractory period: another action potential cannot be formed o Absolute: inactivation gate of NA+ channel is in effect o Relative: action potential COULD form but because of hyperpolarization of AP it is very hard to. - - Think of the image on side as zoomed in myocyte in the heart (muscle cell) - Action potential propagation: action potential moves down the membrane by “activating the adjacent part of membrane) - In resting state the normally, the inside of the nerve cell has a more negative charge compared to the outside (extracellularly). This is because there is more potassium ions inside and more sodium ions outside. o Resting potential/state we see the red line above as flat. - We will look at what happens to charge of the cell and the ions when action potential is propagated. - When the cell gets depolarized is when the cell gets a signal on the outside of the cell that opens their special little gates - the protein receptors on the surface – the transport proteins for example the channels. The channels let sodium ions rush into the cells from the outside (rmr more soidum outside, more K+ inside) o So this causes inside the cell to become more positive meaning the membrane potential depolarizes (potential increases). This makes cell less negative, more positive. o The sudden change in the charge inside the nerve creates a “wave of electricity – your action potential: quick burst of energy travelling along the nerve cell). o After sodium ions rush in and create this spike – this action potential, we need to restore things. ▪ Therefore potassium ion channels will open up, this is phase of repolarization, potassium ions flow out of the cell making the inside negative again and returns it to resting state. ▪ Now potassium is on the outside and sodium is on the inside, over a short period of time the channels are both open and sodium and potassium restore themselves again to their appropriate side of the membrane. ▪ This whole process happens very quickly. ▪ There is a refractory period when the sodium and potassium are going back to their place through leak channels on inside or outside. ▪ This refractory period is a period of time when another action potential cannot occur. A brief period of time where the nerve cannot conduct an impulse ▪ We will see implications for this later when looking at nerve cell dysfunction. - Cells in multicellular organisms have remarkable abilities beyond functioning individually. - They engage in intercellular recognition and communication through the signals that coordinate growth and development and responses to environment. - Cell adhesion ensures the tissues maintain structure and integrity which are vital to organ function and overall health. - Cellular memory is basically a developmental memory cells can pass on to their offspring so that those offspring can develop into the same differentiated cells as their parents - There are specialized patterns of gene expression that dictate each cell's unique role and function in the body and allow for proper tissue organization. - Terminally differentiated cells are cells that have reached their specialized state and typically do not divide any further. - Stem cells are not terminally differentiated and so they possess the unique ability to self- renew and differentiate into various specialized cell times that replenish damaged tissues and support growth and repair. - So together all of these cellular mechanisms underpin the complexity and functionality of organisms and they enable adaption, regeneration, and Maintenace of physiological processes. - Predominant tissues: o Epithelial tissue: covers most of the internal and external body surfaces and it is the most superficial layer of our organs. Most of the thingsi nthe body have an epithelial tissue layer. o Nerve tissue: highly specialized cells and neurons that propagate electrical signals throughout the body. o Muscle tissue: composed of myocytes that enable movement. o Connective tissue: extremely important for binding tissue and binding other organs together to create our body as we know it. - CORRECT: A - Baby is primarily affected by her muscles, brain, and nerves (seizure), these are areas typically use more energy than other part in your body. For cells to functio nthey have to extract and use energy contained within organic molecules (without mitochondria she cannot effectively use these molecules to make efficent amounts of energy) and this is created through metabolism. Catabloism is the pathway that breaks moleceulse down and releases energy. Mitochondria produce energy from carbs, lipids, proteins, and they transfer that energy via a transport molecule we know as ATP.