Biology Notes - Chapter 5: Cellular Functions

Biology Notes- Chapter 5 Cellular Functions Date: 10/16/2023 Plasma Membrane ● Cell membrane- boundary separating cell from its outer environment. The lipid bialyer (2 layers) is a highly complex biological machine regulating the body of a cell ● Trasmembrane (aka integral) proteins are within the membrane and go from 1 side of the membrane to the other side of the membrane. Peripheral proteins are only on 1 side of the membrane ○ Types of proteins inside the proteins- ion channels, pumps, receptors and enzymes, the interdependence of bilayer and proteins suggests that lipid bialyer and proteins co-evolved together ○ (head) Glycerol is a 3-carbon molecule with a carbon functional group attached, (tail) fatty acid, one tail is saturated fatty acid and the other is unsaturated fatty acid. Along with the bialyer membrane, we also have cholesterol in the membrane. Cholosertol function is to provide fluidity in the membrane. The phospholipids move around, they are not static. 2 ○ The structure- Bialyer membrane, 2 phosphoplipids, coming in such a way where the head is always facing the water, the tails are always hiding from the water, proteins across the plasma membrane (some translate or peripheral) and cholesterol to maintain the fluidity of the membrane Cell Membrane- Fluid Mosaic Model ● The fluic mosaic model has been used to describe the structure of plasma membrane. Mosaic- art work of different glasses put together. When you observe plasma membrane under a microscope, it looks like an artwork that’s why it’s called fluid mosaic model. ● Plasma membrane is selective permeability, it goes in and out very easily ● Non-polar and Non-charged-easily be transported across the plasma membrane. Non charged: means they have no electric charge. ● Polar and charged molecules will face difficulty in the transportation, so they will use the help from the proteins. Example: water is a polar molecule, sodium chloride ● Different types of proteins across the membrane: attachment protein, receptor protein, channel transport protein, active transport protein, junction protein, glycoprotein ○ Types of proteins inside the proteins- ion channels, pumps, receptors and enzymes, the interdependence of bilayer and proteins suggests that lipid bialyer and proteins co-evolved together ○ (head) Glycerol is a 3-carbon molecule with a carbon functional group attached, (tail) fatty acid, one tail is saturated fatty acid and the other is unsaturated fatty acid. Along with the bialyer membrane, we also have cholesterol in the membrane. Cholosertol function is to provide fluidity in the membrane. The phospholipids move around, they are not static. 3 Diffusion ● Water will have difficulty being transported across the membrane, but very few can sneak across the membrane. The ones that sneak across the membrane is becauseof osmosis. ○ Osmosis: diffusion of water across the plasma membrane. Water will be diffusing because it will always go from high concentration to low concentration ○ Osmosis is a passive process because water is going down the concentration radiant ○ Water always follows the high solute concentration ○ Passive transport: there is no involvement in ATP, no ATP is required. No ATP is required because they are going from high to low concentration ○ Substances that will diffuse across the plasma membrane and use the passive transport: GASES. Carbon and oxygen are being transported across the plasma membrane with the help of passive diffusion. ○ What type of molecules are gases? Nonpolar and noncharged examples: oxygen and carbon dioxide Cell Membrane- Fluid Mosaic Model ● Different types of proteins across the membrane: attachment protein, receptor protein, channel transport protein, active transport protein, junction protein, glycoprotein ● Different types of proteins across the membrane: attachment protein, receptor protein, channel transport protein, active transport protein, junction protein, glycoprotein ○ Types of proteins inside the proteins- ion channels, pumps, receptors and enzymes, the interdependence of bilayer and proteins suggests that lipid bialyer and proteins co-evolved together ○ (head) Glycerol is a 3-carbon molecule with a carbon functional group attached, (tail) fatty acid, one tail is saturated fatty acid and the other is unsaturated fatty acid. Along with the bialyer membrane, we also have cholesterol in the membrane. Cholosertol function is to provide fluidity in the membrane. The phospholipids move around, they are not static. 4 ○ Types of proteins inside the proteins- ion channels, pumps, receptors and enzymes, the interdependence of bilayer and proteins suggests that lipid bialyer and proteins co-evolved together ○ (head) Glycerol is a 3-carbon molecule with a carbon functional group attached, (tail) fatty acid, one tail is saturated fatty acid and the other is unsaturated fatty acid. Along with the bialyer membrane, we also have cholesterol in the membrane. Cholosertol function is to provide fluidity in the membrane. The phospholipids move around, they are not static. ○ If you have 2 particles, that can diffuse across the membrane they are independent of eachother. They have to diffuse in the space available to them Water ● Water is a very good solvent, nearly almost all of things can dissolve in water. Solute- things that can dissolve in water such as salt and sugar. ● Plasma membrane is selective permeability, it goes in and out very easily ● Non-polar and Non-charged-easily be transported across the plasma membrane. Non charged: means they have no electric charge. ● Polar and charged molecules will face difficulty in the transportation, so they will use the help from the proteins. Example: water is a polar molecule, sodium chloride ● Whenever you have high solute concentration, water will always follow it Osmoregulation ● Definition- Water balance between cell and its surroundings ● Tonicity- ability of a surrounding solution to a cause to gain water or lose water ● 3 types of solutions ○ Isotonic: (same) In an isotomic solution, the solute concentration is equal on both the inside and outside of the cell. 3 inside, 3 outside ○ Hyper: (more) In a hypertonic solution, the solute concentration in the surrounding solution is higher than that in the cell. When red blood cells 5 are placed in a hypertonic solution, they will lose their structure, it’s not good for our cell. 3 inside, 6 outside. The water will go out ○ Hypo: (less) the water will go in. 6 inside, 3 outside. In a hypotonic solution, the solute concentration in the cell is higher than the solution surrounding the cell. ○ Our cells are all in isotomic solution. Plant Cells ● Function of central vacuus, central vacuus is only in plant cells not animal cells. The central vacuus’s function is to hold water and nutrients. When plant cells lose their water, they will lose their structure. ○ In a hypotonic solution, plants need more water in them because the central vacuus will hold the water. When a lot of water is held, there will be pressure which is known as turgor pressure. ○ Turgor Pressure- Force exerted by the water entering (osmosis) the vacule, which then swells exerting internal force on the cell wall ○ Due to the turgor pressure, the plant cells maintain their turgidity, meaning they are normal and healthy all in a hypotonic solution ○ When plant cells are in an hypotonic solution, they are normal, but in an isotonic solution, it will become flaccid meaning its soggy and not stiff anymore ○ Water always follows high colute concentration ○ Paramecium lives in a hypotonic environment, they don’t die. When organisms are found in such extreme einvironemnts, they have inbuilt mechanism in them. Due to the contractile vacuoles, they are able to live in such extreme environements Active & Passive Transport ● Passive: No ATP needed as transport is down the concentration gradient ● Active: ATP is needed as transport is up the concentration gradient ○ Facilitate diffusion: The substances that go from 1 side to another side, we are providing them with a facility, and that facility is proteins, specifically channel proteins. 6 ○ The molecules are going to go from high to low concentration for facilitate diffusion. When you get things that go from high to low, it is always without the ATP (energy) ○ Facilitate diffusion use the help of the channel protein, where in regular diffusion, they don’t have any help from proteins Aquaporin ● In places where you need high transportation you need aquaporin ● Aquaporin definition: transport proteins, help substances diffuse across the membrane down their concentration gradients and requires no input of energy. ○ Aquaporin is in all living organisms, bacteria fungi plants animals. So that water can be transported fast as compared to diffusion. The transportation of water through aquaporins is passive, because no ATP is required ○ In active transport, a cell must expend energy to move a solute against its concentration gradient. ○ When substances go from low to high concentration, ATP is required. The solute particle binds to the transport protein, once it binds ATP gets bindalzied meaning the break down of ATP to transport substances from 1 side of the membrane to another side of the membrane. Once the substance is transported, it will come back to its original structure so that it can transport more substances ➔ Big substances that our cells have to bring out and bring them back in: (cytoplassum is inside the cell) PROTEINS. ○ Excoytosis- is used to export bulkly molecules such as proteins & polysacchrides (OUT) ○ Endocytosis- is used to take in large molecules (IN) examples, phagocytosis and phenocytosis. Phaogocytosis- to bring in solid substances. Phenocytosis- to bring in liquid substances. Receptormediated endocytosis- uses membrane receptors for specific solutes ○ LDL- low density lip protein is bad because it sticks to the blood vessels and arteries and results in a heart attack. Liver takes the LDL inside it 7 through LDL receptors, every liver cell in our body has the LDL receptor. Its taken in through the coated pit. ○ Receptors on your cells that will be involved in taking in substances: receptor-mediated endocytosis Enzymes, then Attachment Proteins ● Attachment proteins attach to the extracellular matrix and cytoskeleton. It can also coordinate internal and external changes Receptor Proteins ● Signal molecules bind to receptor proteins, receptor protein relay the message by activating other molecules inside the cell. They send the signal from 1 side to another side Junction Proteins ● Form intercellular junctions that attach adjacent cells ● they hold 2 cells together so that there’s communication through the cells Glyco Proteins ● Serve as identification tags and may be recognized by membrane proteins of other cells. When one cell binds to another cell, transfer of things will take place, so before they bind they have to see their ID, make sure they match, then communicate with eachother ● Proteins that have carbohydrate attached to them Enzymes ● All enzymes are proteins, but not all proteins are enzymes. Enzyme example: sucrase breaks down sucrose. Sucrose is known as a reactant or substrate. Sucrase breaks down sucrose into glucose and fructose. Glucose and fructose are the products of break down. 8 ● When we talk about how the enzymes work, thereis an energy barrier which is the activation energy, energy absorbed to break and make bonds. ● Enzymes are protein catalysts that decrease the activation energy needed to begin a reaction. ● Catalysts are substances that participate in areaction without being consumed in the reaction ● Enzyme Specificty: A specific enzyme catalyzes each cellular reaction. An enzyme’s substrate fits specifically in its active site. The active site is on the enzyme. Active site is the location where the substrate side binds to the enzyme. Enzyme is the lock, active site is the key hole, and the substrate is the place. Sucrase will break down sucrose into glucose and fructose. ● All enzymes are proteins, some RNA molecules also function as enzymes. There is an energy barrier that must be overcome for a chemical reaction to occur. Activation energy is the barrier that protects the highly ordered molecule. For example, sucrose is a complex molecule that needs to be broken down into glucose and fructose, so the activitation has to bring it down, with the help of enzymes. Enzymes are protein catalysts that decrease the activation energy needed to begin a reaction. ● When you dont have an enzyme, the activation barrier is very big, but when you add the enzymes, the activation is very small. ● For every substrate or reactant, you have a specific enzyme, for instance for every lock you need a specific key to open it. Example: the enzyme sucrase is needed to break down sucrose. ENzyme and substrates must fit appropriately, this is known as induced fit. Hydrolysis to break down with water. Water will be added and the enzyme will break it down into its substrate ● After our bodys have enough glucose and fructose, there is a stopping done by a special category of molecules called competitive inhibitor. ● Compoetitive inhibitor stops the process of breaking a molecule back into its substrate. A non competitive inhibitor alters an enzyme’s function by changing its shape. The competitive’s goal is block the active site to stop the process. Non competitive bind somewhere else and start the active site again.Either you block the active site( compepttive), or you destroy the active site. (Noncompepetive) 9 ● The product, the first enzyme will break it down with a couple enzymes involved, once you have that product your body will use it, if you have enough and cant break down more or your body will send a message to stop the process