AP BIOLOGY Membranes & Proteins Cell Membranes Membranes

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Transcript of AP BIOLOGY Membranes & Proteins Cell Membranes Membranes

UntitledAP BIOLOGY
Membranes & Proteins
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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
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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.
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.
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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.
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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.
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Selective Permeability
So what molecules CAN pass through a membrane made of just phospholipids?
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Yes No
Yes No
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because it is neutral and very small, only 2 atoms big.
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Yes No
Yes No
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H2O will pass through. 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.
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Even though sodium is a very small ion, it has a strong positive charge. The neutral, hydrophobic barrier prevents even the smallest ions from passing.
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Glucose is a large molecule that can not pass through the small gaps between the phospholipids.
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Selective Permeability To recap...
Large molecules or charged molecules will not make it through a lipid bilayer.
Some examples: sugars, ions, nucleic acids, proteins
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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?
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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.
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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.
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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.
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Carbohydrates and the Membrane
Glycoproteins have a carbohydrate attached to a protein and serve as points of attachment for other cells, bacteria, hormones, and many other molecules.
Glycolipids are lipids with a carbohydrate attached. Their purpose is to provide energy and to act in cellular recognition.
pr ot
ei n
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An integral protein forms a pore that allows specific substances to diffuse across the membrane, even if they are large or have charge.
Proteins Regulate What is in a Cell
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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
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5When 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
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5When 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
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6In osmosis, water molecules diffuse from A inside the plasma membrane to outside only
B outside the plasma membrane to inside only
C from areas of high solute concentration to areas of low solute concentration
D from areas of low solute concentration to areas of high solute concentration
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6In osmosis, water molecules diffuse from A inside the plasma membrane to outside only
B outside the plasma membrane to inside only
C from areas of high solute concentration to areas of low solute concentration
D from areas of low solute concentration to areas of high solute concentration
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7What 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
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7What 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
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8What type of solution has a greater flow of water to the inside of the plasma membrane?
A hypertonic
B isotonic
C normal
D hypotonic
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8What type of solution has a greater flow of water to the inside of the plasma membrane?
A hypertonic
B isotonic
C normal
D hypotonic
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9A red blood cell will lyse when placed in which of the following kinds of solution?
A hypertonic
B hypotonic
C isotonic
D any of these
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9A red blood cell will lyse when placed in which of the following kinds of solution?
A hypertonic
B hypotonic
C isotonic
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10Dialysis tubing is permeable to monosaccharides only. Which solute(s) will exhibit a net diffusion out of the cell?
A sucrose
B glucose
C fructose
E sucrose and glucose
environment 0.01M sucrose 0.01M glucose 0.01M fructose
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10Dialysis tubing is permeable to monosaccharides only. Which solute(s) will exhibit a net diffusion out of the cell?
A sucrose
B glucose
C fructose
E sucrose and glucose
environment 0.01M sucrose 0.01M glucose 0.01M fructose
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11Is the solution outside the cell isotonic, hypotonic, or hypertonic?
A Hypertonic
B Hypotonic
C Isotonic
environment 0.01M sucrose 0.01M glucose 0.01M fructose
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11Is the solution outside the cell isotonic, hypotonic, or hypertonic?
A Hypertonic
B Hypotonic
C Isotonic
environment 0.01M sucrose 0.01M glucose 0.01M fructose
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12The 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
12The process by which a cell ingests large solid particles, therefore it is known as "cell eating".
A Pinocytosis
B Phagocytosis
C Exocytosis
D Osmoregulation
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13Antibodies are embedded in cell membranes and bind to antigens on the surface of foreign cells. What type of molecule is an antibody?
A phospholipid
B glycolipid
C glycoprotein
D enzyme
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13Antibodies are embedded in cell membranes and bind to antigens on the surface of foreign cells. What type of molecule is an antibody?
A phospholipid
B glycolipid
C glycoprotein
D enzyme
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Osmosis In animal cells, water moves from areas of low solute concentration to areas of high solute concentration during osmosis. In plants, bacteria, and fungi, however, the cell wall exerts a force on the internal environment of the cell and affects the net flow of water through the cell membrane.
The effects of solute concentration and the pressure provided by the cell wall are incorporated into a quantity called water potential ( ).
Osmosis moves water from areas of high water potential to areas of low water potential.
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Water potential is calculated using the following equation:
Note: Animal cells do not have cell walls so pressure potential = zero
Water potential is measured in megapascals (MPa) or bar.
1 MPa = 10 bar
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14 An animal cell with a solute potential of -0.30 MPa (megapascals) is placed in a sucrose solution with a solute potential of -0.55 MPa. What is the net direction of osmosis?
A into the cell
C not enough information
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14 An animal cell with a solute potential of -0.30 MPa (megapascals) is placed in a sucrose solution with a solute potential of -0.55 MPa. What is the net direction of osmosis?
A into the cell
C not enough information
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15 A fungal cell with a solute potential of -2.5 bar is place in a saline solution with a potential of -1.2 bar. What is the net direction of osmosis?
A into the cell
C not enough information
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15 A fungal cell with a solute potential of -2.5 bar is place in a saline solution with a potential of -1.2 bar. What is the net direction of osmosis?
A into the cell
C not enough information
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16 In a given plant cell, the cell wall exerts 2.3 bar of pressure and the solute potential is -3.0 bar. Calculate the water potential.
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16 In a given plant cell, the cell wall exerts 2.3 bar of pressure and the solute potential is -3.0 bar. Calculate the water potential.
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-0.7 bar
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17 In a given animal cell, the solute potential is -0.25 MPa. Calculate the water potential.
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17 In a given animal cell, the solute potential is -0.25 MPa. Calculate the water potential.
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-0.25 MPa
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18 A turgid plant cell with a solute potential of -7.0 bar is placed in pure water. When the cell reaches osmotic equilibrium with its surroundings, what is the pressure potential of the cell?
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18 A turgid plant cell with a solute potential of -7.0 bar is placed in pure water. When the cell reaches osmotic equilibrium with its surroundings, what is the pressure potential of the cell?
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7.0 bar
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19 A bacterial cell with a solute potential of -9.0 bar is placed in a sucrose solution with a solute potential of -4.0 bar. No net movement of water occurs. What is the pressure potential of the cell?
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19 A bacterial cell with a solute potential of -9.0 bar is placed in a sucrose solution with a solute potential of -4.0 bar. No net movement of water occurs. What is the pressure potential of the cell?
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5.0 bar
Solute Potential
Solute potential is dependent upon type and concentration of solute. Its value can be determine using the following equation:
= -iCRTs
i =# of particles/ions in one molecule of solute after dissociation C = molar concentration (M) R = pressure constant (0.0831 L bar/mol K or 0.0083 L MPa/mol K) T = temperature (K)
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= -iCRTs
= -iCRTs
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= -iCRTs
= -iCRTs
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22 What does T equal for a solution at 260C?
= -iCRTs
22 What does T equal for a solution at 260C?
= -iCRTs
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299 K
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23 Calculate water potential (in bar) for a cell that contains 0.9M NaCl and is stored at 19oC.
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23 Calculate water potential (in bar) for a cell that contains 0.9M NaCl and is stored at 19oC.
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-43.7 bars
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24 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.
0.4 M NaCl 0.5 M Sucrose
37oC
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24 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.
0.4 M NaCl 0.5 M Sucrose
37oC
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-20.6 bars
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25 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.
0.4 M NaCl 0.5 M Sucrose
37oC
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25 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.
0.4 M NaCl 0.5 M Sucrose
37oC
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-12.9 bars
37oC
26 In what direction will the net flow of water occur?
A toward side A
B toward side B
C not enough information
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37oC
26 In what direction will the net flow of water occur?
A toward side A
B toward side B
C not enough information
A ns
w er
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27 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.
0.2 M NaCl 0.2 M Sucrose
0.1 M NaCl 0.3 M Sucrose
25oC
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27 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side A.
0.2 M NaCl 0.2 M Sucrose
0.1 M NaCl 0.3 M Sucrose
25oC
ns w
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28 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.
0.2 M NaCl 0.2 M Sucrose
0.1 M NaCl 0.3 M Sucrose
25oC
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28 In the U-tube experiment illustrated below, calculate the solute potential (in bar) of Side B.
0.2 M NaCl 0.2 M Sucrose
0.1 M NaCl 0.3 M Sucrose
25oC
A ns
w er
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29 In what direction will the net flow of water occur?
A toward side A
B toward side B
C not enough information
25oC
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29 In what direction will the net flow of water occur?
A toward side A
B toward side B
C not enough information
25oC
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Just as individual cells utilize their membranes to maintain homeostasis, so must multicellular organisms maintain a balance in their internal conditions.
Let's look at the mammalian urinary system as an example. Its ability to conserve water is a key adaptation to terrestrial life.
The fundamental unit of the kidney is a nephron. Nephrons rely on solute concentrations to power the reabsorption of water and other nutrients.
Homeostasis in Multicellular Organisms
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Loop of Henle
As the filtrate descends the loop of Henle, increasing osmolarity of the interstitial fluid (fluid between the cells) causes water to diffuse outward.
As the filtrate ascends back up the tubule, decreasing osmolarity enables the facilitated diffusion of NaCl from the filtrate. Some active transport of NaCl also occurs.
The filtrate then enters the collecting ducts where more water is reabsorbed through osmosis.
The water and nutrients are then passively transported back into the blood supply.
Collecting Duct
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30 As the filtrate descends the loop of Henle, the extracellular solute potential ________________ causing the transport of ____________ across the membrane.
A increases, salts
B decreases, salts
C increases, water
D decreases, water
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30 As the filtrate descends the loop of Henle, the extracellular solute potential ________________ causing the transport of ____________ across the membrane.
A increases, salts
B decreases, salts
C increases, water
D decreases, water
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31 Natural selection should favor the highest proportion of nephrons in which of the following species?
A a mouse species living in a tropical rain forest
B a mouse species living in a temperate rain forest
C a mouse species living in a desert
D they would all possess the same proportion of nephrons
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31 Natural selection should favor the highest proportion of nephrons in which of the following species?
A a mouse species living in a tropical rain forest
B a mouse species living in a temperate rain forest
C a mouse species living in a desert
D they would all possess the same proportion of nephrons
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32 Antidiuretic hormone (ADH) is released to maintain homeostasis in response to low blood osmolarity. Which of the following is false regarding this hormone?
A It decreases the active transport of NaCl in the ascending tubule
B It increases the collecting ducts' permeability to water
C It results in a more concentrated urine
D It is a response to increases in perspiration
Slide 60 (Answer) / 181
32 Antidiuretic hormone (ADH) is released to maintain homeostasis in response to low blood osmolarity. Which of the following is false regarding this hormone?
A It decreases the active transport of NaCl in the ascending tubule
B It increases the collecting ducts' permeability to water
C It results in a more concentrated urine
D It is a response to increases in perspiration
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Larger molecules and ions that cannot squeeze between the phospholipids need the help of a transport protein. This is called Facilitated Diffusion .
In Facilitated Diffusion, particles move from an area of high to low concentration with the help of a transport protein. Since the substances are going with the natural concentration gradient, this is a type of Passive Transport: no energy is needed.
Facilitated Diffusion
In facilitated diffusion, transport proteins speed the passive transport of molecules across the plasma membrane.
Transport proteins allow passage of hydrophilic substances across the membrane.
Channel proteins, are one type of transmembrane transport proteins that provide corridors that allow a specific molecule or ion to cross the membrane.
Carrier proteins, are another type of transmembrane transport proteins that change shape slightly when…