Slide 1 / 74 Slide 2 / 74 Biology Membranes 2015-10-28 www.njctl.org Slide 3 / 74 Slide 4 / 74 Membranes Unit Topics Vocabulary Click on the topic to go to that section active transport integral protein · Membranes, Diffusion carrier protein isotonic · Osmosis channel protein molarity · Plasma Membranes concentration gradient osmosis Transport through Proteins diffusion passive transport enzymatic activity peripheral protein facilitated diffusion phospholipid bilayer fluid mosaic selectively permeable hypertonic signal transduction hypotonic Slide 5 / 74 Slide 6 / 74 Membranes, Membranes Diffusion Membranes are an arrangement of phospholipids that gather together to enclose a volume. Membranes act as a wall or a barrier separating the outside and the inside of that enclosed volume. Return to Table of Contents
Slide 7 / 74 Slide 8 / 74 Membranes Phospholipid Bilayer Remember we learned that a phospholipid has a hydrophilic and a The phospholipids do not form a single line, but instead form two hydrophobic end. When these phospholipids arrange to form a parallel lines with their hydrophobic ends in between. Now the membrane that separates the inside and the outside of the shape, hydrophobic ends are protected from the water by the hydrophilic both the inside and the outside of the shape usually include water ends. (think of a water balloon in a bathtub). Phospholipids are amphiphilic molecules: meaning they contain both So how can these phospholipids arrange themselves so that their hydrophobic and hydrophilic regions. hydrophobic ends are not near the water? Move them into a bilayer. We call this a phospholipid bilayer. Slide 9 / 74 Slide 10 / 74 1 The section labelled A is: 2 The sections labelled B are: B A amphiphilic A amphiphilic B hydrophobic A B hydrophobic C hydrophilic C hydrophilic B Slide 11 / 74 Slide 12 / 74 Selective Permeability Homeostasis Membranes allow for the intake of nutrients and the elimination of waste because they are selectively permeable. This means they The formation of a membrane was one of the first steps in evolution can let some molecules pass through and not others. of cells. The membrane separated the inside world and outside world but still allowed for the intake of nutrients and the elimination of waste. Regulating the amount of nutrients and waste passing through the membrane is called maintaining homeostasis.
Slide 13 / 74 Slide 14 / 74 3 The basic component of all membranes is 4 How many layers do plasma membranes have? A one B two A proteins three C B fats D four C starches D phospholipids Slide 15 / 74 Slide 16 / 74 6 Plasma membranes allow all types of molecules to 5 Phospholipids arrange themselves so that their pass through. A hydrophilic ends contact each other B hydrophobic ends ends contact each other True hydrophilic end of one layer meets the C False hydrophobic end of the other layer D hydrophobic ends contact the enclosed volume of fluid Slide 17 / 74 Slide 18 / 74 Passive Transport 7 A cell's regulation of its internal environment is called Some molecules pass through the membrane without the A selective permeability use of energy, this is called passive transport. B plasma membranes C phospholipids D maintaining homeostasis These molecules always move from areas of high concentration to areas of low concentration. This is referred to as moving "with the concentration gradient." Which direction with the molecules move?
Slide 19 / 74 Slide 20 / 74 Expressing Concentrations of Solutions Solutions Review Molarity (M) Solutions are defined as homogeneous mixtures of two or more pure substances. Two solutions can contain the same compounds but be quite different because the proportions of those compounds The _______________ is the substance are different. present in the greatest abundance. Molarity is one way to measure the concentration of a All other substances are ____________. solution. ___________ dissolves the ___________ . moles of the solute Molarity (M) = volume of solution in liters In biology, the solvent is almost always ___________ . Slide 21 / 74 Slide 22 / 74 Concentration Practice Three Types of Passive Transport Calculate the concentrations below. Mass of Volume of Concentration Diffusion Solute Solvent Osmosis 5g C 100ml ___________ Facilitated Diffusion 10g C ___________ 100ml 20g NaCl 100ml ___________ ___________ 20g NaCl 200ml Slide 23 / 74 Slide 24 / 74 Diffusion Diffusion Diffusion is the process where solute molecules move from areas of high concentration to areas of low concentration. Membranes act as the barrier between these two areas. Molecules will continue to diffuse across the membrane until an equilibrium is No energy is reached. required to move molecules with their concentration 8.3mM O 2 gradient. 9.5mM O 2 Which way will the O 2 move?
Slide 25 / 74 Slide 26 / 74 Diffusion 8 Diffusion is the movement of molecules Concentration gradients are specific to each type of molecule meaning A against their concentration gradient each type of molecule can diffuse in a different direction, some in and B with their concentration gradient some out. in their concentration gradient C Diffusion is a D outside their concentration gradient spontaneous process and 9 mM O 2 each type of 6 mM CO 2 molecule diffuses 7.2mM O 2 at its own rate. 7.2mM CO 2 Which way will the O 2 move? Which way will the CO 2 move? Slide 27 / 74 Slide 28 / 74 9 All molecules diffuse from the inside of the membrane to 10 Each type of molecule diffuses at a different rate. the outside of the membrane. True True False False Slide 29 / 74 Slide 30 / 74 11 The membrane is permeable to water and to the simple 12 Which solute(s) will exhibit a net diffusion out of sugars glucose and fructose but completely the cell? impermeable to the sucrose. Which solute(s) will A sucrose exhibit a net diffusion into the cell? environment Cell: 0.01M 0.05M B glucose sucrose sucrose A sucrose environment 0.01M Cell: 0.02M 0.01M C fructose glucose B glucose 0.05M glucose sucrose 0.01M sucrose 0.01M C fructose D sucrose, fructose 0.02M glucose glucose, and glucose 0.01M D sucrose, fructose fructose glucose, and E sucrose and fructose glucose E sucrose and glucose
Slide 31 / 74 Slide 32 / 74 13 When diffusion has occurred until there is no longer a 14 When equilibrium is reached, what is the concentration concentration gradient, then _______________ has of fructose outside the cell? been reached. environment A equilibrium Cell: 0.01M 0.05M B selective permeability sucrose sucrose C phospholipid bilayer 0.01M 0.02M glucose glucose D homeostasis 0.01M fructose Slide 33 / 74 Slide 34 / 74 Osmosis Osmosis Osmosis is the diffusion of free water molecules across a selectively permeable membrane. Return to Table of Contents Slide 35 / 74 Slide 36 / 74 Osmosis Two ways to Describe Osmosis solute molecule The water is moving with its concentration gradient from water molecule an area with lots of free water molecules to an area with fewer free water If the solution on the outside of H 2 O molecules. the membrane has a higher solute concentration than the solution inside, we say that the OR outside solution is hypertonic. This means that water will diffuse from the inside solution to The water moves from areas of low solute the outside solution. concentration to areas of high solute concentration until the solute concentrations are in equilibrium.
Slide 37 / 74 Slide 38 / 74 Osmosis Osmosis If the solution on the outside of the membrane has a lower solute If too much water leaves the cell, due to its being in a hypertonic concentration than the solution inside the membrane we say that the solution, it can shrink or shrivel up. outside solution is hypotonic. This means that water will diffuse from the outside solution to the inside solution. solute molecule solute molecule water molecule water molecule H 2 O H 2 O Slide 39 / 74 Slide 40 / 74 Osmosis Osmosis solute molecule solute molecule water molecule water molecule If the solution on the outside of If too much water the membrane has an equal enters a cell due to its solute concentration to the being in a hypotonic H 2 O solution inside the membrane solution it can swell, we say that the outside solution and if it swells too much is isotonic to the inside solution. H 2 O it can _________, or burst. This means that water will diffuse equally across the membrane in either direction. Slide 41 / 74 Slide 42 / 74 16 Water molecules diffuse from 15 The diffusion of water molecules across a selectively permeable membrane is called what? A inside the plasma membrane to outside only outside the plasma membrane to inside only B A diffusion from areas of high solute concentration to C isotonic B areas of low solute concentration from areas of low solute concentration to C osmosis D areas of high solute concentration D hypotonic
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