Slide 1 / 181 Slide 2 / 181 AP BIOLOGY Membranes & Proteins Slide 3 / 181 Membranes & Proteins Click on the topic to go to that section · Cell Membranes · Transport Proteins · Signaling Proteins · Enzymatic Proteins
Slide 4 / 181 Cell Membranes Return to Table of Contents Slide 5 / 181 Biological Membranes The term membrane most commonly refers to a thin, film-like structure that separates two fluids. Membranes act as a container for biological systems, surrounding protobionts, cells, and organelles. The video below shows experiments done at a laboratory in France to study the properties of lipids. The only substances used in the making of this video are lipids, water and dye . The lipids and dye were mixed and then injected into aqueous solution. Try to figure out some of the properties that make lipids useful as membranes by watching the video. Click here for the video Slide 6 / 181 Phospholipids The most important lipid that composes the majority of biological membranes is the phospholipid . The amphiphilic nature of these lipids cause them to naturally form a spherical bilayer.
Slide 7 / 181 Lipids and the Membrane Phospholipids form two parallel lines with their hydrophobic ends in between. The hydrophobic ends are protected from the water by the hydrophilic ends, creating a bilayer. In animals, cholesterol inserts itself into the membrane in the same orientation as the phospholipid. Cholesterol immobilizes the first few hydrocarbons in the phospholipid, making the bilayer more stable, and impenetrable to water molecules. Slide 8 / 181 Selective Permeability Membranes act as selectively permeable barriers, allowing some particles or chemicals to pass through, but not others. The properties of the phospholipid bilayer dictate what can pass through a membrane. Slide 9 / 181 Selective Permeability When phospholipids come together, they create a wall that is tightly packed with a core that is nonpolar. However, the individual molecules are not fixed and small gaps form as they fluidly move around in the membrane.
Slide 10 / 181 Selective Permeability So what molecules CAN pass through a membrane made of just phospholipids? Slide 11 / 181 1 Will O 2 pass through? Yes No Why? Slide 11 (Answer) / 181 1 Will O 2 pass through? Yes No Why? Answer 0 2 will pass through because it is neutral and very small, only 2 atoms big. [This object is a pull tab]
Slide 12 / 181 2 Will H 2 O pass through? Yes No Why? Slide 12 (Answer) / 181 2 Will H 2 O pass through? Yes No Why? H 2 O will pass through. Answer Even though there is a charge on water, it is partial and the molecule is extremely small. It is slow to diffuse because of its partial charge. [This object is a pull tab] Slide 13 / 181 3 Will Na + pass through? Yes No Why?
Slide 13 (Answer) / 181 3 Will Na + pass through? Yes No Even though sodium is a Why? Answer very small ion, it has a strong positive charge. The neutral, hydrophobic barrier prevents even the smallest ions from passing. [This object is a pull tab] Slide 14 / 181 4 Will C 6 H 12 O 6 pass through? Yes No Why? Slide 14 (Answer) / 181 4 Will C 6 H 12 O 6 pass through? Yes No Why? Glucose is a large Answer molecule that can not pass through the small gaps between the phospholipids. [This object is a pull tab]
Slide 15 / 181 Selective Permeability To recap... Large molecules or charged molecules will not make it through a lipid bilayer. Some examples: sugars, ions, nucleic acids, proteins Slide 16 / 181 How do cells get what they need? We know that cell membranes are made of lipid bilayers, and we know that cells require things like sugar and nucleic acids and proteins and sodium that can't pass through this barrier. So how do cells get the materials they need? Slide 17 / 181 Fluid Mosaic Proteins embedded in the cell membrane facilitate the movement of large or charged molecules through the barrier. By doing this, the internal chemistry of the cell becomes far different than its surroundings. The pattern of lipids and proteins in the cell membrane is referred to as the fluid mosaic model.
Slide 18 / 181 Proteins Regulate What is in a Cell Proteins are long chains of amino acids that fold up on each other to form useful structures in biological systems. Below is a ribbon diagram of an amino acid chain that forms a channel protein. Slide 19 / 181 Types of Membrane Proteins Peripheral proteins 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 . Proteins in the plasma membrane can drift within the bilayer. They are much larger than lipids and move more slowly throughout the fluid mosaic. Slide 20 / 181 Carbohydrates and the Membrane Glycoproteins have a Glycolipids are lipids with carbohydrate attached to a a carbohydrate attached. protein and serve as points Their purpose is to provide of attachment for other energy and to act in cells, bacteria, hormones, cellular recognition. and many other molecules. protein
Slide 21 / 181 Proteins Regulate What is in a Cell An integral protein forms a pore that allows specific substances to diffuse across the membrane, even if they are large or have charge. Slide 22 / 181 Review Membrane Transport Watch this video to review the way in which membranes can regulate by transport. Click here for a review of solute moving through membranes If further review is needed please see NJCTL's first year biology course. Membranes First Year Course Slide 23 / 181 5 When diffusion has occurred until there is no longer a concentration gradient, then _______________ has been reached. A equilibrium B selective permeability C phospholipid bilayer D homeostasis
Slide 23 (Answer) / 181 5 When diffusion has occurred until there is no longer a concentration gradient, then _______________ has been reached. A equilibrium B selective permeability C phospholipid bilayer D homeostasis Answer A [This object is a pull tab] Slide 24 / 181 6 In osmosis, water molecules diffuse from A inside the plasma membrane to outside only B outside the plasma membrane to inside only from areas of high solute concentration to areas of low C solute concentration from areas of low solute concentration to areas of D high solute concentration Slide 24 (Answer) / 181 6 In osmosis, water molecules diffuse from A inside the plasma membrane to outside only B outside the plasma membrane to inside only from areas of high solute concentration to areas of low C solute concentration from areas of low solute concentration to areas of D high solute concentration Answer D [This object is a pull tab]
Slide 25 / 181 7 What type of environment has a higher concentration of solutes outside the plasma membrane than inside the plasma membrane? A hypertonic B isotonic C normal D hypotonic Slide 25 (Answer) / 181 7 What type of environment has a higher concentration of solutes outside the plasma membrane than inside the plasma membrane? A hypertonic isotonic B C normal D hypotonic Answer A [This object is a pull tab] Slide 26 / 181 8 What type of solution has a greater flow of water to the inside of the plasma membrane? A hypertonic B isotonic C normal D hypotonic
Slide 26 (Answer) / 181 8 What type of solution has a greater flow of water to the inside of the plasma membrane? A hypertonic B isotonic C normal D hypotonic Answer D [This object is a pull tab] Slide 27 / 181 9 A red blood cell will lyse when placed in which of the following kinds of solution? hypertonic A hypotonic B isotonic C any of these D Slide 27 (Answer) / 181 9 A red blood cell will lyse when placed in which of the following kinds of solution? hypertonic A hypotonic B isotonic C Answer B any of these D [This object is a pull tab]
Slide 28 / 181 10 Dialysis tubing is permeable to monosaccharides only. Which solute(s) will exhibit a net diffusion out of the cell? A sucrose environment B glucose 0.01M sucrose 0.01M glucose Cell: 0.01M fructose 0.05M sucrose C fructose 0.02M glucose D sucrose, glucose, and fructose E sucrose and glucose Slide 28 (Answer) / 181 10 Dialysis tubing is permeable to monosaccharides only. Which solute(s) will exhibit a net diffusion out of the cell? sucrose A environment glucose B 0.01M sucrose 0.01M glucose Cell: 0.01M fructose 0.05M sucrose C fructose 0.02M glucose D sucrose, glucose, and fructose E sucrose and glucose Answer B [This object is a pull tab] Slide 29 / 181 11 Is the solution outside the cell isotonic, hypotonic, or hypertonic? Hypertonic A environment 0.01M sucrose 0.01M glucose Hypotonic B Cell: 0.01M fructose 0.05M sucrose 0.02M glucose Isotonic C
Slide 29 (Answer) / 181 11 Is the solution outside the cell isotonic, hypotonic, or hypertonic? A Hypertonic environment 0.01M sucrose 0.01M glucose B Hypotonic Cell: 0.01M fructose 0.05M sucrose 0.02M glucose C Isotonic Answer B [This object is a pull tab] Slide 30 / 181 12 The process by which a cell ingests large solid particles, therefore it is known as "cell eating". A Pinocytosis B Phagocytosis C Exocytosis D Osmoregulation Slide 30 (Answer) / 181 12 The process by which a cell ingests large solid particles, therefore it is known as "cell eating". A Pinocytosis B Phagocytosis C Exocytosis Answer B D Osmoregulation [This object is a pull tab]
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