Biology. Slide 1 / 74. Slide 2 / 74. Slide 3 / 74. Membranes. Vocabulary

Transcription

1 Slide 1 / 74 Slide 2 / 74 iology Membranes Vocabulary Slide 3 / 74 active transport carrier protein channel protein concentration gradient diffusion enzymatic activity facilitated diffusion fluid mosaic hypertonic hypotonic integral protein isotonic molarity osmosis passive transport peripheral protein phospholipid bilayer selectively permeable signal transduction

2 Membranes Unit Topics Slide 4 / 74 lick on the topic to go to that section Membranes, iffusion Osmosis Plasma Membranes Transport through Proteins Membranes, iffusion Slide 5 / 74 Return to Table of ontents Membranes Slide 6 / 74 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.

3 Membranes Remember we learned that a phospholipid has a hydrophilic and a hydrophobic end. When these phospholipids arrange to form a membrane that separates the inside and the outside of the shape, both the inside and the outside of the shape usually include water (think of a water balloon in a bathtub). Slide 7 / 74 So how can these phospholipids arrange themselves so that their hydrophobic ends are not near the water? Move them into a bilayer. Phospholipid ilayer Slide 8 / 74 The phospholipids do not form a single line, but instead form two parallel lines with their hydrophobic ends in between. Now the hydrophobic ends are protected from the water by the hydrophilic ends. Phospholipids are amphiphilic molecules: meaning they contain both hydrophobic and hydrophilic regions. We call this a phospholipid bilayer. 1 The section labelled is: Slide 9 / 74 amphiphilic hydrophobic hydrophilic

4 2 The sections labelled are: Slide 10 / 74 amphiphilic hydrophobic hydrophilic Selective Permeability Slide 11 / 74 Membranes allow for the intake of nutrients and the elimination of waste because they are selectively permeable. This means they can let some molecules pass through and not others. Homeostasis Slide 12 / 74 The formation of a membrane was one of the first steps in evolution 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.

5 3 The basic component of all membranes is Slide 13 / 74 proteins fats starches phospholipids 4 How many layers do plasma membranes have? one two three four Slide 14 / 74 5 Phospholipids arrange themselves so that their Slide 15 / 74 hydrophilic ends contact each other hydrophobic ends ends contact each other hydrophilic end of one layer meets the hydrophobic end of the other layer hydrophobic ends contact the enclosed volume of fluid

6 6 Plasma membranes allow all types of molecules to pass through. Slide 16 / 74 True False 7 cell's regulation of its internal environment is called Slide 17 / 74 selective permeability plasma membranes phospholipids maintaining homeostasis Passive Transport Slide 18 / 74 Some molecules pass through the membrane without the use of energy, this is called passive transport. 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?

7 Solutions Review Slide 19 / 74 Solutions are defined as homogeneous mixtures of two or more pure substances. The is the substance present in the greatest abundance. ll other substances are. dissolves the. In biology, the solvent is almost always. Expressing oncentrations of Solutions Slide 20 / 74 Molarity (M) Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different. Molarity is one way to measure the concentration of a solution. Molarity (M) = moles of the solute volume of solution in liters oncentration Practice Slide 21 / 74 alculate the concentrations below. Mass of Solute 5g 10g 20g Nal 20g Nal Volume of Solvent 100ml 100ml 100ml 200ml oncentration

8 Three Types of Passive Transport Slide 22 / 74 iffusion Osmosis Facilitated iffusion iffusion iffusion 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 reached. Slide 23 / 74 iffusion Slide 24 / 74 No energy is required to move molecules with their concentration gradient. 8.3mM O 2 9.5mM O 2 Which way will the O 2 move?

9 iffusion oncentration gradients are specific to each type of molecule meaning each type of molecule can diffuse in a different direction, some in and some out. Slide 25 / 74 iffusion is a spontaneous process and each type of molecule diffuses at its own rate. 7.2mM O2 7.2mM O2 9 mm O2 6 mm O2 Which way will the O 2 move? Which way will the O 2 move? 8 iffusion is the movement of molecules against their concentration gradient with their concentration gradient in their concentration gradient outside their concentration gradient Slide 26 / 74 9 ll molecules diffuse from the inside of the membrane to the outside of the membrane. Slide 27 / 74 True False

10 10 Each type of molecule diffuses at a different rate. True False Slide 28 / The membrane is permeable to water and to the simple sugars and fructose but completely impermeable to the sucrose. Which solute(s) will exhibit a net diffusion into the cell? Slide 29 / 74 sucrose fructose sucrose,, and fructose ell: 0.05M sucrose 0.02M environment 0.01M sucrose 0.01M 0.01M fructose E sucrose and 12 Which solute(s) will exhibit a net diffusion out of the cell? Slide 30 / 74 E sucrose fructose sucrose,, and fructose sucrose and ell: 0.05M sucrose 0.02M environment 0.01M sucrose 0.01M 0.01M fructose

11 13 When diffusion has occurred until there is no longer a concentration gradient, then has been reached. Slide 31 / 74 equilibrium selective permeability phospholipid bilayer homeostasis 14 When equilibrium is reached, what is the concentration of fructose outside the cell? Slide 32 / 74 ell: 0.05M sucrose 0.02M environment 0.01M sucrose 0.01M 0.01M fructose Osmosis Slide 33 / 74 Return to Table of ontents

12 Osmosis Slide 34 / 74 Osmosis is the diffusion of free water molecules across a selectively permeable membrane. Two ways to escribe Osmosis Slide 35 / 74 The water is moving with its concentration gradient from an area with lots of free water molecules to an area with fewer free water molecules. OR The water moves from areas of low solute concentration to areas of high solute concentration until the solute concentrations are in equilibrium. Osmosis Slide 36 / 74 solute molecule water molecule If the solution on the outside of the membrane has a higher solute concentration than the solution inside, we say that the outside solution is hypertonic. This means that water will diffuse from the inside solution to the outside solution. H 2 O

13 Osmosis If too much water leaves the cell, due to its being in a hypertonic solution, it can shrink or shrivel up. Slide 37 / 74 solute molecule water molecule H 2 O Osmosis If the solution on the outside of the membrane has a lower solute concentration than the solution inside the membrane we say that the outside solution is hypotonic. This means that water will diffuse from the outside solution to the inside solution. Slide 38 / 74 solute molecule water molecule H 2 O Osmosis Slide 39 / 74 solute molecule water molecule If too much water enters a cell due to its being in a hypotonic solution it can swell, and if it swells too much it can, or burst. H 2 O

14 Osmosis Slide 40 / 74 solute molecule If the solution on the outside of the membrane has an equal solute concentration to the solution inside the membrane we say that the outside solution is isotonic to the inside solution. water molecule H2 O This means that water will diffuse equally across the membrane in either direction. 15 The diffusion of water molecules across a selectively permeable membrane is called what? Slide 41 / 74 diffusion isotonic osmosis hypotonic 16 Water molecules diffuse from inside the plasma membrane to outside only outside the plasma membrane to inside only from areas of high solute concentration to areas of low solute concentration from areas of low solute concentration to areas of high solute concentration Slide 42 / 74

15 17 iffusion and osmosis are both types of active transport. Slide 43 / 74 True False 18 What type of environment has a higher concentration of solutes outside the plasma membrane than inside the plasma membrane? Slide 44 / 74 hypertonic isotonic normal hypotonic 19 What type of environment has an equal amount of solute on the inside and outside of the plasma membrane? Slide 45 / 74 hypertonic isotonic normal hypotonic

16 20 What type of solution has a greater flow of water to the inside of the plasma membrane? Slide 46 / 74 hypertonic isotonic normal hypotonic 21 The membrane is permeable to water and to the simple sugars and fructose but completely impermeable to the sucrose. Is the solution outside the cell isotonic, hypotonic, or hypertonic? Slide 47 / 74 Hypertonic Hypotonic Isotonic ell: 0.03M sucrose 0.03M environment 0.02M sucrose 0.04M 0.01M fructose 22 In which direction will there be a net osmotic movement of water? Slide 48 / 74 In Out No net osmosis ell: 0.05M sucrose 0.03M environment 0.02M sucrose 0.04M 0.01M fructose

17 Plasma Membrane of ells, Transport through Proteins Slide 49 / 74 Return to Table of ontents Plasma Membrane of ells Slide 50 / 74 Early cells were simple lipid bilayers, relying only on passive transport. Later cells developed more complex membranes that included proteins. These proteins act as doorways to allow for more molecules to enter and leave the cell. Most small molecules can diffuse without membrane proteins. Larger molecules need to be facilitated (helped) to diffuse across a membrane by these proteins. Phospholipid ilayer Remember that membranes are made up mostly of phospholipids. Slide 51 / 74 Phospholipids are molecules, containing hydrophobic and hydrophilic regions.

18 2 Types of Membrane Proteins Slide 52 / 74 The plasma membrane also contains two types of proteins: Peripheral proteins are not embedded in the membrane, but instead stay on only one side of the membrane. Integral proteins pass through the hydrophobic core and often span the membrane from one end to the other, also called transmembrane proteins. Fluid Mosaic The plasma membrane is sometimes referred to as a fluid mosaic. Slide 53 / 74 Fluid because the phospholipids can move sideways within the membrane and do not stay in one stationary position. Proteins can also move around in the membrane but they are much larger than lipids and move more slowly. Fluid Mosaic The plasma membrane is sometimes referred to as a fluid mosaic. Slide 54 / 74 Mosaic means the membrane contains many different proteins spread throughout.

19 23 Which of the following statements about the role of phospholipids in forming membranes is correct? Slide 55 / 74 They are completely insoluble in water. They form a single sheet in water. They form a structure in which the hydrophobic portion faces outward. They form a selectively permeable structure. 24 Which best describes the structure of a cell's plasma membrane? proteins sandwiched betweeen two layers of phospholipids Slide 56 / 74 proteins embedded in two layers of phospholipids phospholipids sandwiched between two layers of proteins a layer of protein coating two layers of phospholipids 25 The fluid-mosaic model of membrane structure refers to. the fluidity of phospholipids and the pattern of proteins in the membrane Slide 57 / 74 the fluidity of proteins and the pattern of phospholipids in the membrane the ability of proteins to switch sides in the membranes the fluidity of hydrophobic regions, proteins, and the mosaic pattern of hydrophillic regions

20 Membrane Protein Functions Slide 58 / 74 Proteins serve several important functions in the cell membrane. Transport Signal transduction ell-cell recognition Enzymatic activity Transport Slide 59 / 74 Proteins can act as doorways for nutrients and waste. There are two types of transport which require proteins: Facilitated iffusion (a type of passive transport) ctive Transport (requires energy) Facilitated iffusion Slide 60 / 74 Small molecules like O2 and O2 readily diffuse through all plasma membranes because they are small and non-polar; they can squeeze between the phospholipids. However... Larger molecules and ions, charged particles, cannot squeeze between the phospholipids, they need the help of a transport protein. This is called Facilitated iffusion.

21 Facilitated iffusion Slide 61 / 74 Just like regular diffusion, particles in Facilitated iffusion move from an area of high to low concentration. Unlike regular diffusion these particles move through the membrane with the help of a integral protein. Since the substances are going with their concentration gradient, this is a type of Passive Transport: no energy is needed. Examples of Transport Proteins Slide 62 / 74 hannel proteins are one type of transmembrane transport protein that provide corridors that allow a specific molecule or ion to cross the membrane. arrier proteins are another type of transmembrane transport protein that change shape slightly when a specific molecule binds to it in order to help move that molecule across the membrane. Examples of Transport Proteins Slide 63 / 74

22 26 Which of the following molecules is most likely to diffuse freely across the lipid bilayer of the plasma membrane without the involvement of a transport protein? Slide 64 / 74 E carbon dioxide sodium ion N all of the above 27 Which of the following processes includes all others? Slide 65 / 74 osmosis diffusion of a solute across a membrane facilitated diffusion passive transport 28 Facilitated diffusion moves molecules. Slide 66 / 74 against their concentration gradients using energy against their concentration gradients without the use of energy with their concentration gradients using energy with their concentration gradients without the use of energy

23 29 arrier proteins are an example of integral proteins. Slide 67 / 74 True False ctive Transport Slide 68 / 74 ctive Transport uses energy to move solutes through a transport protein against their concentration gradients. arrier proteins can be used in active transport for specific molecules. energy omparing Facilitated iffusion and ctivetransport Slide 69 / 74 Passive Transport ctive Transport (REQUIRES ENERGY) lick here for a comparison of the different forms of membrane transport

24 30 Which one of the following is not in some way involved in facilitated diffusion? Slide 70 / 74 E a concentration gradient a membrane a protein an energy source all of the above are components of facilitated diffusion 31 ctive transport moves molecule. against their concentration gradients using energy against their concentration gradients without the use o energy with their concentration gradients using energy with their concentration gradients without the use of en Slide 71 / Which protein can be used for both active and passive transport? carrier protein channel protein any integral protein any transmembrane protein Slide 72 / 74

25 Membrane Protein Functions Slide 73 / 74 Proteins serve several important functions in the cell membrane. Transport Signal transduction Some proteins are used to gather information about the cell's surrounding environment. ell-cell recognition Some proteins are used to recognize viruses, bacteria, or other cells that have attached to the cell they are in. Enzymatic activity Some proteins are used to catalyze (speed up) reactions. lick here for an animation about Membrane Proteins Slide 74 / 74 iffusion Facilitated iffusion ctive Transport No Energy arrier Protein Transmembrane Protein hannel Protein High Low Energy Required Low High