BIOL 101 Guided Reading Questions GRQs Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment L4 GRQs Membrane Structure and Function Reading Objectives Describe cell membrane structure Differentiate molecules that can freely cross cell membranes vs those that can t Compare and contrast the different ways in which various substances cross membranes Make predictions about water movement during osmosis Apply the two mechanisms of chemical signaling to insulin signaling and sex hormone signaling Module 5 1 5 2 Membranes are fluid mosaics of lipids and proteins with many functions The spontaneous formation of membrane was a critical step in the origin of life 1 What is meant by the terms fluid mosaic and selective permeability when describing membranes fluid mosaic is a model of a cell membrane depicted as a mosaic of protein molecules suspended in fluid bilayer selective permeability property of biological membranes that regulates passage of substances across them 2 Why was the spontaneous formation of membranes such an important step in cell evolution a membrane that not only encloses a successful assembly of molecules but also regulates chemical exchanges with the environment is a basic requirement of life Module 5 3 Passive transport is diffusion across a membrane with no energy investment 1 Use the words diffusion and concentration gradient in a sentence Diffusion is the process of molecules moving from a higher concentration to a lower concentration This can occur within a solvent or across a membrane A concentration gradient contains stored energy that drives diffusion 2 How does the structure of the membrane relate to its selective permeability Think about the chemical properties of the inner core of the bi layer The cell membrane is selectively permeable due to its structure The phospholipids are arranged in a bilayer with the hydrophobic tails facing inward The tails are packed tightly together thus preventing any large molecules from diffusing through 3 Can O2 and CO2 diffuse easily across a membrane Why or why not Review and define the words polar and nonpolar if you need to Because the cell membrane is semipermeable only small uncharged substances like carbon dioxide and oxygen can easily diffuse across it Molecules of oxygen and carbon dioxide have no charge and pass through by simple diffusion Polar substances with the exception of water present problems for the membrane While some polar molecules connect easily with the outside of a cell they cannot readily pass through the lipid core of the plasma membrane 4 What do ions and polar molecules need to diffuse across the hydrophobic interior of a membrane they diffuse across the membrane through transport proteins BIOL 101 Guided Reading Questions GRQs Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment Module 5 4 Osmosis is the diffusion of water across a membrane 1 When water moves through a selectively permeable membrane down its concentration gradient this is termed osmosis 2 If I give you a 5 sucrose solution and a 10 sucrose solution in which solution is the free water less concentrated 10 sucrose solution 3 If the 5 and 10 solution were separated by a semi permeable membrane that sucrose could not move between the water would move towards the 10 solution Using Figure 5 4 to check your answer Module 5 5 Water balance between cells and their surroundings is crucial to organisms 1 Tonicity refers to the ability of a surrounding solution to cause a cell to gain or lose water 2 Tonicity of a solution is dependent on concentration of nonpenetrating solutes 2 Define Isotonic any external solution that has the same solute concentration and water concentration compared to body fluids In an isotonic solution no net movement of water will take place Hypertonic any external solution that has a high solute concentration and low water concentration compared to body uids Hypotonic a solution with a solute concentration lower than that of the cell 3 Practice If a cell is put into a solution that is hypertonic to its cytosol what would happen shrink or swell Why Where is the water more concentrated the net movement of water will be out of the body and into the solution A cell placed into a hypertonic solution will shrivel and die by a process known as plasmolysis water is more concentrated in solute and not in cell Modules 5 6 Transport proteins can facilitate diffusion across membranes 1 How is facilitated diffusion similar and different from diffusion both involve movement down the concentration gradient The difference is how the substance gets through the cell membrane 2 In our discussion of how cells use glucose as an energy resource we will see that cells can bring glucose in from the blood where the concentration is higher What kind of transport does glucose use facilitated diffusion 3 Water is a polar molecule but it is very small so it can diffuse slowly into cells What type of membrane protein would you expect to find in a cell to make it highly permeable to water aquaporin BIOL 101 Guided Reading Questions GRQs Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment Module 5 8 Cells expend energy in the active transport of solute 1 How do calcium ions move against their concentration gradient Primary active transport uses the energy of ATP to move molecules in this calcium ions against its concentration gradient The natural movement of ions is from high to low concentration This occurs through facilitated diffusion 2 How is this similar or different from facilitated diffusion It is similar it goes from high to low Module 5 9 Exocytosis and endocytosis transport large molecules across membranes 1 Compare and contrast exocytosis and endocytosis exocytosis movement of materials out of a cell by fusion of vesicles with plasma membrane endocytosis transport process through which a cell takes in large molecules or droplets of fluid 2 What are the distinctions between phagocytosis and receptor mediated endocytosis Phagocytosis is the taking in of large food particles while pinocytosis takes in liquid particles Receptor mediated endocytosis uses special receptor proteins to help carry large particles across the cell membrane Module 26 3 A widely used weed killer demasculinzes male frogs 1 Scientific Thinking What hypothesis were the scientists testing long term atrazine exposure will make amphibians
View Full Document
Unlocking...