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 a fluid mosaic is a term used to describe a membrane s structure diverse protein molecules suspended in a fluid phospholipid bilayer this model illustrates the structure and function of a plasma membrane the boundary that encloses a living cell selective permeability means that it allows some substances to cross more easily than others these combinations 2 Why was the spontaneous formation of membranes such an important step in cell evolution a membrane can enclose a solution that is different in composition from its surroundings If that solution included self replicating molecules such as RNA and a beneficial assortment of other molecules cells as new membrane enclosed vesicles budded off 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 occurs by the concentration gradient where substances usually move from regions of higher concentration to regions of lower concentration could be passed on to daughter 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 hydrophobic core acts as a barrier to water soluble substances letting only certain molecules pass through it selective permeability is crucial for maintaining cellular homeostasis and regulating the internal environment in the cell 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 yes they can because they are small nonpolar molecules 4 What do ions and polar molecules need to diffuse across the hydrophobic interior of a membrane they need transport proteins Module 5 4 Osmosis is the diffusion of water across a membrane BIOL 101 Guided Reading Questions GRQs Complete and submit this GRQ as a PDF before lecture and before your online Mastering Assignment 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 in the 10 sucrose collusion 3 If the 5 and 10 solution were separated by a semi permeable membrane that sucrose could not move between the water would move toward 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 gain or lose water 2 Tonicity of a solution is dependent on its concentration of solutes relative to the concentration of solutes inside the cell 2 Define Isotonic equal solute levels Hypertonic higher solute levels Hypotonic lower solute levels 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 shrink because the cell will lose water the free water concentration is higher inside the cell Modules 5 6 Transport proteins can facilitate diffusion across membranes 1 How is facilitated diffusion similar and different from diffusion facilitated diffusion is the passage of a substance through a specific transport protein across biological membrane down its concentration gradient 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 active transport 2 How is this similar or different from facilitated diffusion the energy requirement for facilitated vs active transport differs facilitated diffusion is passive transport and moves substances down their gradient Active transport is reliant on energy and moves substances against the gradient Module 5 9 Exocytosis and endocytosis transport large molecules across membranes 1 Compare and contrast exocytosis and endocytosis a cell uses exocytosis to export bulky materials such as proteins or polysaccharides endocytosis is a transport process through which a cell takes in large molecules or droplet of fluid 2 What are the distinctions between phagocytosis and receptor mediated endocytosis a receptor mediated endocytosis enables a cell to acquire specific solutes phagocytosis is when a cell engulfs a particle by wrapping extensions called pseudopodia Module 26 3 A widely used weed killer demasculinzes male frogs 1 Scientific Thinking What hypothesis were the scientists testing the hypothesis the scientists were testing were that long term exposure to low levels of atrazine would affect the reproduction function in amphibians negatively causing demasculinization in frogs 2 What were the control and experimental groups control group male frogs not exposed to atrazine experiment group male frogs that were exposed to low levels of atrazine for three years 3 What was were the independent variable exposure to atrazine 4 What was were the dependent variables mating success 5 What were the results ong 2 of the 16 atrazine exposed males were successful in amplexus 6 This was a controlled laboratory study does it have any implications for the real world environment the findings
View Full Document
Unlocking...