Bio 120 Structured Study Sessions (SSS) PDF

University Library Structured Study Sessions (SSS): Bio 120 Janelle and Steve October 1, 2024 Please note: This material ha...

University Library Structured Study Sessions (SSS): Bio 120 Janelle and Steve October 1, 2024 Please note: This material has been developed by your awesome Structured Study Sessions Peer Mentor and not your course professors! Selection of session materials is based on your peer mentor’s knowledge and experiences with taking the course and input from the SSS Peer Mentor Team.  University Library Question of the day… What is your name, and what is your favourite season?  University Library What are we going over today? § Plasma membrane structure – review § Membrane fluidity § Diffusion § Passive and active transport  University Library How would glucose pass through the plasma membrane? A. It would go right through the membrane via simple diffusion B. It would require a channel protein C. It would require a carrier protein D. It wouldn’t be able to pass through the membrane  University Library How would glucose pass through the plasma membrane? A. It would go right through the membrane via simple diffusion B. It would require a channel protein C. It would require a carrier protein D. It wouldn’t be able to pass through the membrane  University Library What best describes primary active transport? A. It directly uses the energy of ATP to move a molecule against its gradient B. It uses the concentration gradient of one molecule to move another molecule against its gradient C. It does not require any energy D. It always requires channel proteins  University Library What best describes primary active transport? A. It directly uses the energy of ATP to move a molecule against its gradient B. It uses the concentration gradient of one molecule to move another molecule against its gradient C. It does not require any energy D. It always requires channel proteins  University Library Plasma membrane § Made up of phospholipids and proteins § Phospholipids: hydrophilic head and hydrophobic tail § The membrane forms because the tails don’t want to be in contact with water § The proteins are embedded in the membrane and can move around within the phospholipids This Photo by Unknown Author is licensed under CC BY-SA-NC  University Library Membrane proteins – roles? § Transport of molecules across the membrane § Enzymes § Signal transduction § Cell surface attachment and recognition  University Library Membrane Fluidity § Some phospholipids have a bit more freedom of movement and associate with each other less than others. Other phospholipids associate with each other more tightly and have less freedom of movement Situations that make the membrane less fluid: § When the phospholipids have longer tails § When the phospholipids don’t have double bonds (saturated) Situations that make the membrane more fluid: § When the phospholipids have shorter tails § When the phospholipids have double bonds (unsaturated)  University Library Membrane fluidity regulation § Desaturases – add double bonds to the fatty acid. As temperature goes down, desaturase concentration goes up. § Cholesterol – only in animals  University Library Cholesterol in the membrane § Cholesterol is found only in animal cells § It works to regulate membrane fluidity at high and low temperatures At low temperatures: § Cholesterol gets in between the fatty acid tails and prevents them from tightly associating At high temperatures: § Cholesterol restricts the movement of fatty acid tails – decreasing fluidity This Photo by Unknown Author is licensed under CC BY-SA-NC  University Library What molecules can pass through the membrane? § Some molecules can pass directly through the plasma membrane – they don’t need any help from a protein. These include small, uncharged molecules like oxygen and carbon dioxide § Some molecules cannot pass directly through the membrane. These are typically larger molecules like glucose or, they have a charge like ions. These molecules will need help from a membrane protein in order to get across the membrane  University Library Diffusion - general § Diffusion refers to the idea that substances will want to spread out into available space (because this results in an increase in entropy, or randomness) § For example, if you cook food in your kitchen the smell will spread throughout your house. This is just the molecules causing the scent molecules spreading so they are not all clustered together in one area § This idea underlies the diffusion that happens across the cell membrane This Photo by Unknown Author is licensed under CC BY-SA-NC  University Library Passive transport § Passive transport is any membrane transport that does not require the input of energy § This means that the molecule being transported is moving down its concentration gradient § Examples are simple diffusion, facilitated diffusion, osmosis This Photo by Unknown Author is licensed under CC BY  University Library Simple diffusion § As we talked about earlier, small, uncharged molecules can move directly across the cell membrane. When this happens, it’s called simple diffusion § Simple diffusion is a type of passive transport – it doesn’t require any energy § The molecules move from an area where they are more concentrated to an area where they are less concentrated. This means that they are moving down their concentration gradient  University Library So, what exactly is a concentration gradient? § This occurs when a molecule has a higher concentration in one area than another § In our case, this could mean that a molecule has a higher or lower concentration inside the cell than outside membrane UP o a a down  University Library Osmosis § Movement of water across the membrane § Doesn’t require an energy input – water is always moving into an area with a higher solute concentration (either into the cell or out) § Either directly across membrane or through channels called aquaporins  University Library Osmosis – important terms Hypotonic Hypertonic Isotonic Hypotonic Hypertonic Isotonic i iii i iii iii  University Library What would happen to desaturase concentration when temperature decreases? A. It would decrease B. It would remain the same C. It would increase D. It would either increase or decrease  University Library What would happen to desaturase concentration when temperature decreases? A. It would decrease B. It would remain the same C. It would increase D. It would either increase or decrease  University Library A solution is hypertonic to a cell. How will water move? A. Water will move out of the cell B. There will be not net movement of water C. Water will move in circles around the cell D. Water will move into the cell  University Library A solution is hypertonic to a cell. How will water move:? A. Water will move out of the cell B. There will be not net movement of water C. Water will move in circles around the cell D. Water will move into the cell  University Library What organism would have cholesterol in its cell membrane? A. Wolf B. Paramecium C. Hibiscus flower D. Dragonfly  University Library What organism would have cholesterol in its cell membrane? A. Wolf B. Paramecium C. Hibiscus flower D. Dragonfly  University Library Facilitated diffusion § Still does not require any input of energy – uses concentration gradient § But this time the molecule can’t move through the phospholipids in the plasma membrane – for example, they might be ions § For ions to move through the plasma membrane, we need special channels called ion channels § Facilitated diffusion can also move molecules using carrier proteins. This would be for moving larger molecules like glucose.  University Library Facilitated diffusion examples § Sodium and potassium ion channels § These are used to generate electrical signals within the cell § These ion channels are specific to one ion because of the way they are built. For example, the diameter of the potassium channel is just right to allow potassium through, but is too larger to allow sodium through because of its hydration shell  University Library Active transport § This type of transport requires an input of energy because the molecule being transported is no longer moving down its concentration gradient § There are 3 types: primary active, secondary active, and vesicular  University Library Primary active transport § Uses carrier proteins § ATP is broken down by the membrane protein in order to generate energy for the transport of a molecule against its gradient § Protein undergoes conformational change This Photo by Unknown Author is licensed under CC BY-NC  University Library Primary active transport - example § Na-K ATPase This Photo by Unknown Author is licensed under CC BY-SA-NC  University Library Secondary active transport § Uses a carrier protein § Moves one molecule down its concentration gradient in order to move another molecule against its gradient § Does not directly use the energy of ATP – instead uses the energy stored in the concentration gradient of one of the molecules § Example is the sodium-glucose transporter  University Library Types of transporters § Uniport – moves one molecule § Antiport – moves molecules in different directions § Symport – moves molecules in the same direction § These are often thought of in terms of secondary active transport § But really they can apply to any type of membrane transport involving a carrier protein  University Library Potassium has a higher concentration inside the cell. It moves out of the cell via a channel protein. What type of transport is this? A. Primary active B. Simple diffusion C. Facilitated diffusion D. Secondary active  University Library Potassium has a higher concentration inside the cell. It moves out of the cell via a channel protein. What type of transport is this? A. Primary active B. Simple diffusion C. Facilitated diffusion D. Secondary active  University Library The Na-K-ATPase moves 3 sodium out of the cell and 2 potassium into the cell. This is an example of? A. Antiport B. Symport C. Uniport D. None of the above  University Library The Na-K-ATPase moves 3 sodium out of the cell and 2 potassium into the cell. This is an example of? A. Antiport B. Symport C. Uniport D. None of the above  University Library Endocytosis § 3 types: phagocytosis, receptor-mediated endocytosis, and pinocytosis § It is used to transport molecules that are too big to be transported using the membrane proteins  University Library Phagocytosis § Cell engulfs a bacterial cell or a large particle § The plasma membrane pushes out around the bacterial cell, eventually engulfing it and bringing it into a phagosome inside the cell This Photo by Unknown Author is licensed under CC BY-SA  University Library Receptor-mediated endocytosis § The molecule to be brought into the cell (the ligand) binds to a receptor on the cell’s surface § The receptor migrates to an indentation in the cell membrane called a clathrin-coated pit § This indentation folds inward and forms a vesicle, bringing the ligand into the cell This Photo by Unknown Author is licensed under CC BY  University Library Pinocytosis § Referred to as cellular drinking § It is less specific than receptor- mediated § The cell takes in some of the fluid surrounding it, so it gets any nutrients or molecules that were in that fluid § It is the same process, the membrane folds inward and forms a vesicle This Photo by Unknown Author is licensed under CC BY-SA  University Library Exocytosis § This is the process where large molecules (such as metabolic wastes) are expelled from the cell § A vesicle travels to the cell membrane and fuses with it, expelling its contents outside of the cell This Photo by Unknown Author is licensed under CC BY  University Library Kahoot! https://play.kahoot.it/v2/lobby?qui zId=fc05778d-061b-4540-a478- 4c58c18854f4  University Library Your university library is here to help library.usask.ca