Body Fluid Compartments and Cell Membranes Linda S. Costanzo, Ph.D.
|
|
- Augustus Todd
- 6 years ago
- Views:
Transcription
1 Body Fluid Compartments and Cell Membranes Linda S. Costanzo, Ph.D. OBJECTIVES: 1. Describe the major and minor body fluid compartments. 2. Compare the total cation and anion concentrations in meq/l in each compartment and comment on their relation to the law of macroscopic electroneutrality. 3. Compare the ion concentrations between the plasma water and the interstitial fluid in terms of the Gibbs-Donnan equilibrium. 4. Describe the cell membrane lipid bilayer structure and the role of the phosophlipids, cholesterol, and glycolipids in cell membranes. 5. Describe the concept of the fluid mosaic membrane model comparing integral and peripheral proteins. 6. Describe the role of the cytoskeleton in cell membrane protein localization and the unique role of glycoproteins. 7. Categorize types of membrane transport with respect to whether they are downhill or uphill and whether they are carrier-mediated. Suggested Reading: Physiology, edited by: R.M. Berne and M. N. Levy, Mosby, 6 th Ed. pp 5-7; Physiology, L.S. Costanzo, Saunders, pp 1-6, 8-12 I. VOLUME AND DISTRIBUTION OF BODY FLUIDS Water content (total body water, or TBW) comprises about 60% of body weight. The percentage varies between 50-70%, depending on gender and amount of adipose tissue. Males tend to have a higher percentage of water than females. Water content is inversely correlated with adipose tissue. Infants have up to 75% body weight as water, which is why severe diarrhea can be life-threatening. Water is distributed between two major compartments: intracellular fluid (ICF) and extracellular fluid (ECF), which are separated from each other by cell membranes. ICF is 2/3 of TBW and ECF is 1/3 of TBW. ECF is further sub-divided into two compartments, the interstitial fluid and plasma compartments, which are separated from each other by capillary walls. Interstitial fluid is 3/4 of ECF, and plasma water is 1/4 of ECF. Lymph, which is part of the ECF, is interstitial fluid that is collected in the lymphatic vessels and then returned to the plasma compartment. An additional minor compartment is the transcellular fluid, which is not part of ICF or ECF. Transcellular fluids are separated from the rest of the body fluids by a layer of cells, and they include gastrointestinal, peritoneal, pleural, and cerebrospinal fluids. Collectively, the volume of transcellular fluids is small, so they are ignored in the above summary numbers.
2 A simple tool is the rule. Approximately 60% of body weight is water (TBW), 40% of body weight is ICF, and 20% is ECF. (ICF is 2/3 of TBW, i.e., 40% of body weight; ECF is 1/3 of TBW, i.e., 20% of body weight.) II. COMPOSITION OF BODY FLUIDS A. Units A few tidbits on units. Please save for reference throughout the course! 1. Concentrations in body fluids are often expressed in molarity, such as mmol/l. 2. For electrolytes, we sometimes use equivalents, such as meq/l, which is the concentration in mmol/l x charge on the ion. Thus, for univalent ions, meq/l = mmol/l; for divalent ions, meq/l = 2 x mmol/l. For example, a Na + concentration of 1 mmol/l = 1 meq/l; a Ca 2+ concentration of 1 mmol/l = 2 meq/l.
3 3. Osmolarity is total solute concentration, expressed in units of mosmoles/liter. Osmolarity is concentration of solute particles, or concentration in mmol/l x number of particles that dissociate in solution (called g, the osmotic coefficient). For example, the osmolarity of 150 mmol/l NaCl = 150 mmol/l x 2 = 300 mosm/l (since NaCl dissociates into two particles in solution, i.e., g = 2). Osmolality is virtually the same thing as osmolarity, but expressed as mosmoles/kg H 2 0. Plasma osmolarity can be approximated as 2 x [Na + ]. 4. Substances like proteins are conventionally expressed in g/dl, where a dl (deciliter) is 100 ml and is also called %. 5. % can mean g per 100 ml. For example, 0.9% NaCl is 0.9 g NaCl/100 ml. It s weird, but that s what it means. Likewise, mg % can mean mg per 100 ml. For example, 5 mg% KCl means 5 mg KCl/100 ml. B. Composition The approximate ionic compositions of the plasma water, interstitial fluid, and intracellular compartments are shown in Table 1. Plasma water and interstitial fluid are ECF, while the muscle cell values represent ICF. Ion Interstitial fluid Plasma Water (meq/l) (meq/l) Muscle cell (meq/l) Cations Na K free Ca ~ 10-4 (rest bound) free Mg Total Cations Anions Cl HCO phosphates proteins other anions (ATP etc) Total Anions Table Note that the total ion concentration, in meq/l, for any compartment (e.g., plasma water) obeys the law of macroscopic electroneutrality,
4 i.e. the concentration of positive charges must always equal the concentration of negative charges. This law applies, and is always true, for any body fluid compartment. (Remember, macroscopic electroneutrality is not just a good idea it s the law!) 2. The individual ionic compositions of the ICF are very different from those of the ECF. For example, the Na + concentration is much lower in the ICF than in the ECF, while the K + concentration is much higher in the ICF than in the ECF. These differences in concentration across cell membranes are created and maintained by a cell membrane Na + /K + pump, that will be discussed in a subsequent lecture. The large Na + gradient across cell membranes that is created by the Na + /K + pump is, in turn, utilized by cells in many critical functions; for example, the Na + gradient is the basis of the upstroke of the action potential in nerve and muscle and is the energy source for the uphill transport of various other solutes (see later lectures). Also, the free Ca 2+ concentration is much lower in the ICF than in the ECF. Cell membrane Ca 2+ ATPase and Ca 2+ -Na + exchange help to keep intracellular free Ca 2+ in the submicromolar range. Also, a large fraction of the intracellular Ca 2+ is sequestered in cell organelles and is released only transiently in connection with important cell functions, such as muscle contraction, signal transduction, and release of hormones or neurotransmitter. 3. The compositions of the plasma and interstitial fluid (both part of the ECF) are very similar, but not identical. The major difference in the composition of plasma and interstitial fluid compartments is that the plasma contains large, negatively charged proteins, while the interstitial fluid is essentially protein-free. This difference, in turn, accounts for the small differences in concentration of small, diffuseable ions (e.g., Na +, K +, Cl - ) in these two compartments. The reason for these differences is that the small ions are free to diffuse between the plasma and the interstitial fluid across the capillary membranes, while the large protein anions are restricted to the plasma. Because the law of macroscopic electroneutrality must be obeyed in both plasma and interstitial fluid compartments, the plasma (with its negatively charged protein) will have a slightly higher concentration of diffuseable cations and a slightly lower concentration of diffuseable anions relative to the interstitial fluid. This special equilibrium, due to the presence of protein on one side of the membrane, is called the Gibbs- Donnan equilibrium, which is discussed below. III. GIBBS-DONNAN EQUILIBRIUM
5 A. Hypothetical example Figure 2. This simplified drawing explains what happens when a Gibbs-Donnan equilibrium is established. Solution 2 has protein (Pr-), and Solution 1 has no protein. In the initial system (before Gibbs-Donnan equilibrium is established), there is 9 meq/l of NaCl in Solution 1 and 9 meq/l of NaPr in Solution 2. The anion Pr - is assumed to be impermeable across the membrane that separates the two solutions, but Na + and Cl - are freely permeable across the membrane. Since Solution 2 initially contains no Cl -, Cl - will begin moving from Solution 1 to 2 down its concentration gradient. To preserve macroscopic electroneutrality (the law!), an equal number of Na + must move with the Cl -. As the Na + concentration in phase 2 increases, Na + backflux from Solution 2 to Solution 1 will eventually prevent further net Na + diffusion, and eventually also stop the further movement of Cl -. Because of the presence of the impermeant protein and because of the requirement for electroneutrality of both solutions, neither Na + nor Cl - can achieve equal concentrations on both sides; however, at equilibrium (the Gibbs- Donnan equilibrium), they achieve a compromise position. This equilibrium condition is expressed as an equality of ion products: where the subscripts 1 and 2 refer to the two solutions, and x is the number of meq/l of Cl - and Na + that have moved from Solution 1 to Solution 2. Solving the equation, for this example, we find that x = 3. At equilibrium, [Na + ] 1 = 6 meq/l, [Cl - ] 1 = 6 meq/l, [Na + ] 2 = 12 meq/l, and [Cl - ] 2 = 3 meq/l. [Pr - ] 2 remains at 9 meq/l. Note that at equilibrium, macroscopic electroneutrality still holds! In this case [Na + ] 1 = [Cl - ] 1, = 6 meq/l and [Na + ] 2 = [Cl - ] 2 + [Pr - ] 2 = 12 meq/l. The equilibrium condition also defines a constant ratio, r, called the Gibbs-Donnan ratio. This is:
6 r = [Na + ] 1 /[Na + ] 2 = [Cl - ] 2 /[Cl - ] 1 In this hypothetical example, r = 0.5. B. Real life example Extending to real life, we are interested in the Gibbs-Donnan ratio for plasma (p) and interstitial fluid (i), where r for the common ions is: Substituting actual values in plasma and interstitial fluid from Table 1, we find that r = Again, this redistribution of small ions across the capillary membrane is due to the presence of negatively charged protein in the plasma but not in the interstitial fluid. IV. CELL MEMBRANE STRUCTURE The membranes that separate the ICF and ECF serve as physical barriers and also contain a variety of proteins involved in transport of substances between the ICF and ECF. In addition, membrane proteins act as enzymes, receptors for ligands such as hormones and neurotransmitters, and as antigens. The basic structure of the cell membrane is a lipid bilayer, which consists of phospholipids, cholesterol, and sphingolipids. The phospholipids present in cell membranes are characterized as amphipathic, i.e. part of their structure is non-polar and hydrophobic, and part of their structure is polar and hydrophilic. Such amphipathic molecules are most stable when they are sitting at the interface between an aqueous phase (polar) and a lipid or oil phase (non-polar). For example at the interface between oil and water, phospholipids form a monolayer with the polar head of the molecule in the aqueous phase and the non-polar long-chain fatty acid tails in the non-polar oil phase. Phospholipids can also form a stable structure separating two aqueous solutions (e.g., ICF and ECF); in this arrangement, the non-polar tails point toward each other to form a bilayer, and the polar heads make contact with the aqueous solutions on either side. This lipid bilayer is the backbone of the cell membrane and accounts for the typical membrane thickness of about 10 nm. lipid monolayer
7 lipid bilayer Figure 3. A. Typical Lipid Profile of a Cell Membrane Lipid Percent by Weight Phosphatidylcholine 17.5 Sphingomyelin 16.0 Phosphatidylethanolamine 16.6 Phosphatidylserine 7.9 Phosphatidylinositol 1.2 Phosphatidic acid 0.6 Lysophosphatidylcholine 0.9 Cholesterol 26.0 Glycolipids 11.0 Table Phospholipids - The first seven lipids in Table 2 are phospholipids. The most abundant of these provide the structural barrier. We have already discussed their critical amphipathic properties. Phosphatidylinositol is present mainly on the cytoplasmic (ICF) side of the bilayer and is of special functional importance because it serves as the substrate for phosphatidylinositol 4,5-diphosphate (PIP 2 ). PIP 2 in turn can be broken down to inositol 1, 4, 5 trisphosphate (IP 3 ) and diacylglycerol (DAG) by the activation of the enzyme, phospholipase C (PLC) The activation of PLC normally occurs as part of a signal transduction cascade in response to the binding of a ligand (e.g. a hormone) to a membrane receptor protein. Both IP 3 and DAG serve as cell second messengers. 2. Cholesterol helps to buffer the fluidity of the non-polar fatty acids of the phospholipids. If present in the proper amount, cholesterol prevents the membrane from becoming either too rigid (wax-like) or
8 too fluid (olive oil-like). 3. Glycolipids These lipids are linked to carbohydrate moieties that extend out from the bilayer into the ECF. They often act as membrane antigens (such as blood group antigens A and B) or, in some cases, as membrane receptors. B. Membrane Proteins Fluid Mosaic Model In this concept of membrane structure, proteins are thought to be either imbedded in or adsorbed onto the surface of the lipid bilayer (see figure below). They are not rigidly held in place (although there are exceptions, see below), but may diffuse in the plane of the bilayer. There are two main types of membrane protein: 1. Integral or intrinsic proteins these proteins usually span the bilayer and have hydrophobic amino acids that make contact with the fatty acid chains of the bilayer and hydrophilic amino acids that contact the ECF and the ICF. It requires detergent action to remove integral proteins from the lipid. Functionally, integral proteins may be receptors, enzymes, ion channels, carrier proteins etc. 2. Peripheral or extrinsic proteins these proteins are bound to either the interior or exterior membrane surface, and are associated with the membrane through hydrophilic interactions. Figure Localization of membrane proteins Some cell types require membrane proteins to be confined to specific regions of the membrane (for example, in epithelial cells, the Na + /K + - ATPase (Na + /K + -pump). Epithelial cells, such as those lining the intestinal mucosa, are polarized cells that sit between two different extracellular fluids; their apical membranes contact the aqueous fluid in the lumen of the intestine, while their basolateral membranes contact the interstitial fluid. For functional reasons that will be described later, the Na + /K + - ATPase is confined exclusively to the basolateral membrane. This can
9 occur because the Na + /K + - ATPase is linked to the membrane cytoskeleton via linking proteins, ankyrin and fodrin (see figure below). The linkage prevents the ATPase from diffusing from the basolateral to the apical cell membrane. Figure Membrane Glycoproteins Carbohydrate moieties can link to membrane proteins especially at the ECF side of the membrane. Growth, differentiation, and maintenance of many cell types depend on interactions between anchoring glycoproteins in the extracellular matrix, such as fibronectin, and specific glycoproteins on the cell surface, called integrins. The interaction sets off intracellular transduction events that, during early development, guide differentiation, and, at cell maturity, regulate cell division and programmed cell death (apoptosis). V. OVERVIEW OF MEMBRANE TRANSPORT The types of membrane transport are: Simple diffusion Facilitated diffusion Primary active transport Secondary active transport (cotransport and countertransport) Osmosis (of water) A. Energetics 1. Downhill transport means a substance is transported down an electrochemical gradient and requires no consumption of metabolic energy. Simple and facilitated diffusion illustrate downhill transport. 2. Uphill transport means a substance is transported against an electrochemical gradient and requires consumption of metabolic energy (either directly in the form of ATP or indirectly in the form of
10 an ion gradient). Primary and secondary active transport illustrate uphill transport. B. Carrier- or non-carrier mediated Transport is further characterized by whether it is carrier-mediated or not. Carrier-mediated transport includes all types except simple diffusion. The features of carrier-mediated transport include: saturation, stereospecificity, and competition. Saturation. Because carrier proteins have a limited number of binding sites for the transported solute, saturation of transport occurs. The point at which all binding sites are occupied by solute is called the transport maximum or T m. (T m is analogous to Vmax in enzyme kinetics.) Stereospecificity. Binding of solute to transporters is highly stereospecific. For example, in the small intestine, the transporter for glucose absorption recognizes the natural isomer, D-glucose,
11 but does not recognize or transport the L-isomer. (Simple diffusion, in contrast, does not distinguish between the natural and unnatural isomers.) Competition. Although transporters exhibit a high degree of stereospecificity, still they can be tricked into transporting chemically similar solutes. Thus, D-galactose can compete for the D-glucose transporter and, by occupying some of the glucose binding sites, inhibit D-glucose transport; this is an example of competitive inhibition. There is also a phenomenon of noncompetitive inhibition, in which compounds that are structurally unrelated to the transported compound bind to the transporter and prevent it from functioning. In the case of D-glucose transport, phloretin is a noncompetitive inhibitor. VI. PRACTICE PROBLEMS 1. A body fluid compartment has a Na + concentration of 15 mm; this compartment is most likely the: A. interstitial fluid compartment B. ICF C. plasma D. small intestinal lumen E. cerebrospinal fluid 2. A solution contains 0.5 mm MgCl 2. The concentrations of Mg 2+ and Cl - in meq/l are respectively: A. 0.5, 0.5 B. 1, 2 C. 2, 1 D. 1, 1 E. 0.5, 1 3. The Donnan ratio for diffusable ions between two solutions (Solution 1 relative to Solution 2) is found to be Accordingly, which of the following describes the Gibbs-
12 Donnan equilibrium condition for these two solutions? A. [Na + ] 1 = 140 mm, [Na + ] 2 = 155 mm B. [Cl - ] 1 = 106 mm, [Cl - ] 2 = mm C. [K + ] 1 = 4 mm, [K + ] 2 = 4.7 mm D. [Ca 2+ ] 1 = 2 mm, [Ca 2+ ] 2 = 2.5 mm E. [Mg 2+ ] 1 = 1 mm, [Mg 2+ ] 2 = 1.25 mm 4. The plasma contains anionic proteins that cannot cross the capillary membranes. When the plasma is in equilibrium with the interstitial fluid: A. the concentration of permeable anions is higher in the plasma than in the interstitial fluid. B. the concentration of permeable cations is higher in the interstitial fluid than in the plasma. C. the concentration of permeable anions will be the same in each fluid phase. D. the concentration of permeable cations will be the same in each fluid phase. E. the concentration of permeable anions is higher in the interstitial fluid than in the plasma. 5. An impermeable anion is in phase 1 which is in Gibbs-Donnan equilibrium with phase 2 containing only permeable ions. The following data are obtained: [K + ] 1 = 6 mm, [K + ] 2 = 3.6 mm, and [Cl - ] 1 = 100 mm. [Cl - ] 2 is then: A.100 mm B.110 mm C. 90 mm D. 167 mm E. 3.6 mm
13 6. In problem 5, at least one other permeable cation must also be present because: A. there must always be 2 different cations present. B. [K + ] 2 < [Cl - ] 2 which appears to violate macroscopic electroneutrality. C. [Cl - ] 1 must equal [Cl - ] 2. D. the permeable anion concentrations in phase 1 must always equal the permeable cation concentrations in phase 1. E. [Cl - ] 1 < [Cl - ] The main permeability barrier in the cell plasma membrane resides in the: A. peripheral proteins B. integral proteins C. lipid bilayer D. lipid monolayer E. phosphatidalinositol layer ANSWERS 1. B (a Na + concentration in this range can only be in the ICF given the choices) 2. D ( [Mg 2+ ] = (2 meq/mmole)(0.5 mmole/l) = 1 meq/l, [Cl - ] = (1 meq/mmole)(1 mmole/l) = 1 meq/l) 3. B (this is the only choice that expresses the correct Donnan ratio, viz. [Cl - ] 2 /[Cl - ] 1 = 100.7/106 = 0.95) 4. E (Since the interstitial fluid has no protein anions, electroneutrality must be satisfied by the permeable anions, which means that the latter will be higher in the interstitial fluid compartment). 5. D (Since: [K + ] 1 /[K + ] 2 = [Cl - ] 2 /[Cl - ] 1, then [Cl - ] 2 = (6)(100)/3.6 = 167 mm) 6. B (There must be a cation, M + (assuming a monovalent cation for simplicity) whose concentration in phase 2 is mm, so that [K + ] 2 + [M + ] 2 = [Cl - ] 2. This means that [M + ] 1 = mm. The impermeable anion concentration must then have been mm). 7. C
Cellular Physiology. Body Fluids: 1) Water: (universal solvent) Body water varies based on of age, sex, mass, and body composition
Membrane Physiology Body Fluids: 1) Water: (universal solvent) Body water varies based on of age, sex, mass, and body composition H 2 O ~ 73% body weight Low body fat; Low bone mass H 2 O ( ) ~ 60% body
More informationTransport through membranes
Transport through membranes Membrane transport refers to solute and solvent transfer across both cell membranes, epithelial and capillary membranes. Biological membranes are composed of phospholipids stabilised
More informationBIOL 158: BIOLOGICAL CHEMISTRY II
BIOL 158: BIOLOGICAL CHEMISTRY II Lecture 1: Membranes Lecturer: Christopher Larbie, PhD Introduction Introduction Cells and Organelles have membranes Membranes contain lipids, proteins and polysaccharides
More informationCellular Messengers. Intracellular Communication
Cellular Messengers Intracellular Communication Most common cellular communication is done through extracellular chemical messengers: Ligands Specific in function 1. Paracrines Local messengers (neighboring
More informationChapter 7: Membranes
Chapter 7: Membranes Roles of Biological Membranes The Lipid Bilayer and the Fluid Mosaic Model Transport and Transfer Across Cell Membranes Specialized contacts (junctions) between cells What are the
More informationWhat do you remember about the cell membrane?
Cell Membrane What do you remember about the cell membrane? Cell (Plasma) Membrane Separates the internal environment of the cell from the external environment All cells have a cell membrane Selectively
More informationInteractions Between Cells and the Extracellular Environment
Chapter 6 Interactions Between Cells and the Extracellular Environment Et Extracellular lll environment Includes all parts of the body outside of cells Cells receive nourishment Cells release waste Cells
More informationThe Cell Membrane. Lecture 3a. Overview: Membranes. What is a membrane? Structure of the cell membrane. Fluid Mosaic Model. Membranes and Transport
Lecture 3a. The Cell Membrane Membranes and Transport Overview: Membranes Structure of cell membranes Functions of cell membranes How things get in and out of cells What is a membrane? Basically, a covering
More information3.2.3 Transport across cell membranes
alevelbiology.co.uk 3.2.3 Transport across cell membranes SPECIFICATION The basic structure of all cell membranes, including cell-surface membranes and the membranes around the cell organelles of eukaryotes,
More informationMembrane Structure and Membrane Transport of Small Molecules. Assist. Prof. Pinar Tulay Faculty of Medicine
Membrane Structure and Membrane Transport of Small Molecules Assist. Prof. Pinar Tulay Faculty of Medicine Introduction Cell membranes define compartments of different compositions. Membranes are composed
More informationComprehensive and Easy Course Notes for BIOL1040 Exams and Assessment
Comprehensive and Easy Course Notes for BIOL1040 Exams and Assessment MODULE 1: PRINCIPLES OF CELL FUNCTION Membrane Structure & Function Cellular membranes are fluid mosaics of lipids and proteins Phospholipids
More informationCh7: Membrane Structure & Function
Ch7: Membrane Structure & Function History 1915 RBC membranes studied found proteins and lipids 1935 membrane mostly phospholipids 2 layers 1950 electron microscopes supported bilayer idea (Sandwich model)
More informationLipids and Membranes
Lipids and Membranes Presented by Dr. Mohammad Saadeh The requirements for the Pharmaceutical Biochemistry I Philadelphia University Faculty of pharmacy Biological membranes are composed of lipid bilayers
More informationChapter 7: Membrane Structure and Function
Chapter 7: Membrane Structure and Function Concept 7.1 Cellular membranes are fluid mosaics of lipids and proteins 1. Phospholipids are amphipathic. Explain what this means. Name Period Amphipathic means
More informationCells: The Living Units
Cells: The Living Units Introduction Life in general occurs in an aqueous environment All chemical processes essential to life occur within the aqueous environment of the cell and surrounding fluids contained
More informationMembrane transport. Pharmacy Dr. Szilvia Barkó
Membrane transport Pharmacy 04.10.2017 Dr. Szilvia Barkó Cell Membranes Cell Membrane Functions Protection Communication Import and and export of molecules Movement of the cell General Structure A lipid
More informationThe Plasma Membrane - Gateway to the Cell
The Plasma Membrane - Gateway to the Cell 1 Photograph of a Cell Membrane 2 Cell Membrane The cell membrane is flexible and allows a unicellular organism to move 3 Homeostasis Balanced internal condition
More informationMain Functions maintain homeostasis
The Cell Membrane Main Functions The main goal is to maintain homeostasis. Regulates materials moving in and out of the cell. Provides a large surface area on which specific chemical reactions can occur.
More informationMembrane Structure and Function
Membrane Structure and Function Chapter 7 Objectives Define the following terms: amphipathic molecules, aquaporins, diffusion Distinguish between the following pairs or sets of terms: peripheral and integral
More informationCh 3 Membrane Transports
Ch 3 Membrane Transports what's so dynamic about cell membranes? living things get nutrients and energy from the envrionment this is true of the entire organism and each cell this requires transport in/out
More informationTransport across the cell membrane
Transport across the cell membrane Learning objectives Body compartments ECF and ICF Constituents Lipid Bilayer: Barrier to water and water-soluble substances ions glucose H 2 O urea CO 2 O 2 N 2 halothane
More informationThe Plasma Membrane - Gateway to the Cell
The Plasma Membrane - Gateway to the Cell 1 Photograph of a Cell Membrane 2 Cell Membrane The cell membrane is flexible and allows a unicellular organism to move 3 Homeostasis Balanced internal condition
More information10/28/2013. Double bilayer of lipids with imbedded, dispersed proteins Bilayer consists of phospholipids, cholesterol, and glycolipids
Structure of a Generalized Cell MEMBRANES Figure 3.1 Plasma Membrane Fluid Mosaic Model Separates intracellular fluids from extracellular fluids Plays a dynamic role in cellular activity Glycocalyx is
More informationChapter 3: Exchanging Materials with the Environment. Cellular Transport Transport across the Membrane
Chapter 3: Exchanging Materials with the Environment Cellular Transport Transport across the Membrane Transport? Cells need things water, oxygen, balance of ions, nutrients (amino acids, sugars..building
More informationChapter 9 - Biological Membranes. Membranes form a semi-permeable boundary between a cell and its environment.
Chapter 9 - Biological Membranes www.gsbs.utmb.edu/ microbook/ch037.htmmycoplasma Membranes form a semi-permeable boundary between a cell and its environment. Membranes also permit subcellular organization
More informationChapter 7: Membrane Structure and Function. Key Terms:
Key Terms: Selectively permeable Fluid mosaic model Amphipathic Phospholipid Bilayer Hydrophilic Hydrophobic Phosphate head Fatty acid tail Davson-Danielli Singer-Nicolson Freeze-Fracture EM Unsaturated
More informationDiffusion, Osmosis and Active Transport
Diffusion, Osmosis and Active Transport Particles like atoms, molecules and ions are always moving Movement increases with temperature (affects phases of matter - solid, liquid, gas) Solids - atoms, molecules
More informationConcept 7.1: Cellular membranes are fluid mosaics of lipids and proteins
Concept 7.1: Cellular membranes are fluid mosaics of lipids and proteins Lipids: Non-polar substances such as fat that contain C, H, O. Phospholipids: Lipid with phosphate group, very abundant in plasma
More informationLecture 36: Review of membrane function
Chem*3560 Lecture 36: Review of membrane function Membrane: Lipid bilayer with embedded or associated proteins. Bilayers: 40-70% neutral phospholipid 10-20% negative phospholipid 10-30% cholesterol 10-30%
More informationMembrane Structure and Function. Selectively permeable membranes are key to the cell's ability to function
Membrane Structure and Function Selectively permeable membranes are key to the cell's ability to function Amphipathic Molecules Have both hydrophilic and hydrophobic regions Phospholipids have hydrophilic
More informationThe Cell Membrane & Movement of Materials In & Out of Cells PACKET #11
1 February 26, The Cell Membrane & Movement of Materials In & Out of Cells PACKET #11 Introduction I 2 Biological membranes are phospholipid bilayers with associated proteins. Current data support a fluid
More informationBiomembranes structure and function. B. Balen
Biomembranes structure and function B. Balen All cells are surrounded by membranes Selective barrier But also important for: 1. Compartmentalization 2. Biochemical activities 3. Transport of dissolved
More informationCH 7.2 & 7.4 Biology
CH 7.2 & 7.4 Biology LABEL THE MEMBRANE Phospholipids Cholesterol Peripheral proteins Integral proteins Cytoskeleton Cytoplasm Extracellular fluid Most of the membrane A phospholipid bi-layer makes up
More informationChapter 2 Transport Systems
Chapter 2 Transport Systems The plasma membrane is a selectively permeable barrier between the cell and the extracellular environment. It permeability properties ensure that essential molecules such as
More informationPhospholipids. Extracellular fluid. Polar hydrophilic heads. Nonpolar hydrophobic tails. Polar hydrophilic heads. Intracellular fluid (cytosol)
Module 2C Membranes and Cell Transport All cells are surrounded by a plasma membrane. Eukaryotic cells also contain internal membranes and membrane- bound organelles. In this module, we will examine the
More informationChapter 7: Membrane Structure & Function
Chapter 7: Membrane Structure & Function 1. Membrane Structure 2. Transport Across Membranes 1. Membrane Structure Chapter Reading pp. 125-129 What are Biological Membranes? Hydrophilic head WATER They
More informationChapter 7: Membrane Structure & Function. 1. Membrane Structure. What are Biological Membranes? 10/21/2015. Why phospholipids? 1. Membrane Structure
Chapter 7: Membrane Structure & Function 1. Membrane Structure 2. Transport Across Membranes 1. Membrane Structure Chapter Reading pp. 125-129 What are Biological Membranes? Hydrophilic head WATER They
More informationDraw and label a diagram to show the structure of membranes
2.4 Membranes 2.4.1 - Draw and label a diagram to show the structure of membranes Phospholipid Bilayer - This is arranged with the hydrophilic phosphate heads facing outwards, and the hydrophobic fatty
More informationCell Membrane Diagram
Cell Membrane Diagram Draw a diagram of the cell membrane. Please include (and label): - Phospholipid bilayer (hydrophilic and hydrophobic) Protein channel An ion pump Cholesterol Gylcoproteins* Define
More informationMembrane Transport. Biol219 Lecture 9 Fall 2016
Membrane Transport Permeability - the ability of a substance to pass through a membrane Cell membranes are selectively permeable Permeability is determined by A. the phospholipid bilayer and B. transport
More informationThe table indicates how changing the variable listed alone will alter diffusion rate.
Rate of Diffusion (flux) Concentration gradient substance x surface area of membrane x lipid solubility = Distance (thickness of membrane) x molecular weight Table 3-1: Factors Influencing the Rate of
More informationMolecular Cell Biology. Prof. D. Karunagaran. Department of Biotechnology. Indian Institute of Technology Madras
Molecular Cell Biology Prof. D. Karunagaran Department of Biotechnology Indian Institute of Technology Madras Module 4 Membrane Organization and Transport Across Membranes Lecture 1 Cell Membrane and Transport
More informationPHYSIOLOGY 2017: OPTO 5344 Lecture 1. Transport across the cell membrane Constanzo 1. I. Introduction
PHYSIOLOGY 2017: OPTO 5344 Lecture 1. Transport across the cell membrane Constanzo 1 I. Introduction Fig. 1 Composition and size of cells and organelles (Ganong, 21 st edition) Water - 70-85% of cell mass
More informationChapter 4 Cell Membrane Transport
Chapter 4 Cell Membrane Transport Plasma Membrane Review o Functions Separate ICF / ECF Allow exchange of materials between ICF / ECF such as obtaining O2 and nutrients and getting rid of waste products
More informationMembranes. Chapter 5
Membranes Chapter 5 Membrane Structure The fluid mosaic model of membrane structure contends that membranes consist of: -phospholipids arranged in a bilayer -globular proteins inserted in the lipid bilayer
More informationMembrane Transport. Anatomy 36 Unit 1
Membrane Transport Anatomy 36 Unit 1 Membrane Transport Cell membranes are selectively permeable Some solutes can freely diffuse across the membrane Some solutes have to be selectively moved across the
More informationMembrane Structure. Membrane Structure. Membrane Structure. Membranes
Membrane Structure Membranes Chapter 5 The fluid mosaic model of membrane structure contends that membranes consist of: -phospholipids arranged in a bilayer -globular proteins inserted in the lipid bilayer
More informationCell Membranes and Signaling
5 Cell Membranes and Signaling Concept 5.1 Biological Membranes Have a Common Structure and Are Fluid A membrane s structure and functions are determined by its constituents: lipids, proteins, and carbohydrates.
More informationConsider the structure of the plasma membrane (fig. 8.6)- phospholipid bilayer with peripheral and integral proteins.
Topic 8: MEMBRANE TRANSPORT (lectures 11-12) OBJECTIVES: 1. Have a basic appreciation of the chemical characteristics of substances that impact their ability to travel across plasma membranes. 2. Know
More informationGateway to the Cell 11/1/2012. The cell membrane is flexible and allows a unicellular organism to move FLUID MOSAIC MODEL
Gateway to the Cell The cell membrane is flexible and allows a unicellular organism to move Isolates the cell, yet allows communication with its surroundings fluid mosaics = proteins (and everything else)
More informationLecture Series 4 Cellular Membranes. Reading Assignments. Selective and Semi-permeable Barriers
Lecture Series 4 Cellular Membranes Reading Assignments Read Chapter 11 Membrane Structure Review Chapter 12 Membrane Transport Review Chapter 15 regarding Endocytosis and Exocytosis Read Chapter 20 (Cell
More informationPLASMA MEMBRANE. Submitted by:- DR.Madhurima Sharma PGGCG-II,Chandigarh
PLASMA MEMBRANE Submitted by:- DR.Madhurima Sharma PGGCG-II,Chandigarh LIPID COMPONENTS OF THE PLASMA MEMBRANE The outer leaflet consists predominantly of phosphatidylcholine, sphingomyelin, and glycolipids,
More informationCell membrane & Transport. Dr. Ali Ebneshahidi Ebneshahidi
Cell membrane & Transport Dr. Ali Ebneshahidi Cell Membrane To enclose organelles and other contents in cytoplasm. To protect the cell. To allow substances into and out of the cell. To have metabolic reactions
More informationBiology 2201 Unit 1 Matter & Energy for Life
Biology 2201 Unit 1 Matter & Energy for Life 2.2 Cell Membrane Structure Primary Membrane Function: Homeostasis Conditions in the cell must remain more or less constant under many different conditions
More informationCell Transport. Movement of molecules
Cell Transport Movement of molecules TEKS Students will investigate and explain cellular processes, including homeostasis and transport of molecules Homeostasis The maintaining of a stable body system
More informationMembrane Transport II (Osmosis) Linda S. Costanzo, Ph.D.
Membrane Transport II (Osmosis) Linda S. Costanzo, Ph.D. OBJECTIVES: 1. Be able to define and calculate osmolarity 2. Describe osmosis across a semipermeable membrane and the volume changes that will occur
More informationChapter 8 Cells and Their Environment
Chapter Outline Chapter 8 Cells and Their Environment Section 1: Cell Membrane KEY IDEAS > How does the cell membrane help a cell maintain homeostasis? > How does the cell membrane restrict the exchange
More informationThe Cell Membrane & Movement of Materials In & Out of Cells PACKET #11
1 The Cell Membrane & Movement of Materials In & Out of Cells PACKET #11 Introduction I 2 Biological membranes are phospholipid bilayers with associated proteins. Current data support a fluid mosaic model
More informationTransport Across the Cell Membrane 11/5/07
11/5/07 "The difference between the internal and external chemical composition of a cell represents a degree of order, that can be maintained only by a barrier to free movement into and out of the cell.
More informationMembrane Structure and Function. Cell Membranes and Cell Transport
Membrane Structure and Function Cell Membranes and Cell Transport 1895 1917 1925 Membrane models Membranes are made of lipids Phospholipids can form membranes Its actually 2 layers - there are proteins
More informationCHAPTER 8 MEMBRANE STUCTURE AND FUNCTION
CHAPTER 8 MEMBRANE STUCTURE AND FUNCTION Plasma Membrane Plasma membrane is selectively permeable, (allowing some substances to cross more easily than others) PM is flexible bends and changes shape
More informationCh. 7 Diffusion, Osmosis, and Movement across a Membrane
Ch. 7 Diffusion, Osmosis, and Movement across a Membrane Diffusion Spontaneous movement of particles from an area of high concentration to an area of low concentration Does not require energy (exergonic)
More informationThe Cell Membrane (Ch. 7)
The Cell Membrane (Ch. 7) Phospholipids Phosphate head hydrophilic Fatty acid tails hydrophobic Arranged as a bilayer Phosphate attracted to water Fatty acid repelled by water Aaaah, one of those structure
More informationTransport of Solutes and Water
Transport of Solutes and Water Across cell membranes 1. Simple and Facilitated diffusion. 2. Active transport. 3. Osmosis. Simple diffusion Simple diffusion - the red particles are moving from an area
More informationMembranes. Chapter 5. Membrane Structure
Membranes Chapter 5 Membrane Structure Lipid Bilayer model: - double phospholipid layer - Gorter & Grendel: 1925 Fluid Mosaic model: consist of -phospholipids arranged in a bilayer -globular proteins inserted
More informationCell membranes. Stef Elorriaga 4/11/2016 BIO102
Cell membranes Stef Elorriaga 4/11/2016 BIO102 Announcements Lab report 2 is due now Quiz 2 is on Wednesday on cells, part of the cells, plasma membrane, and enzymes Outline of the day Activity on the
More informationEH1008 Biomolecules. Inorganic & Organic Chemistry. Water. Lecture 2: Inorganic and organic chemistry.
EH1008 Biomolecules Lecture 2: Inorganic and organic chemistry limian.zheng@ucc.ie 1 Inorganic & Organic Chemistry Inorganic Chemistry: generally, substances that do not contain carbon Inorganic molecules:
More informationThe phosphate group replaces the fatty acid on C number 3 of a triacylglycerol molecule O O CH 2 O C R CH 2 O P O X OH.
Phosphoacylglycerols (Phospholipids) Phosphoacylglycerols are fatty acid esters of glycerol which also contain a phosphate group and other specific groups The phosphate group replaces the fatty acid on
More informationMolecular Organization of the Cell Membrane
Molecular Organization of the Cell Membrane A walk from molecules to a functional biostructure Cell Membrane Definition An ultrastructure separating connecting the cell to the environment 1 Coarse chemical
More informationLecture Series 4 Cellular Membranes
Lecture Series 4 Cellular Membranes Reading Assignments Read Chapter 11 Membrane Structure Review Chapter 12 Membrane Transport Review Chapter 15 regarding Endocytosis and Exocytosis Read Chapter 20 (Cell
More informationMcCance: Pathophysiology, 6th Edition
McCance: Pathophysiology, 6th Edition Chapter 01: Cellular Biology Test Bank TRUE/FALSE 1. Eukaryotic cells are characterized by a lack of a distinct nucleus, whereas prokaryotic cells have intracellular
More informationMembrane Structure and Function
BIOL1040 Page 1 Membrane Structure and Function Friday, 6 March 2015 2:58 PM Cellular Membranes Fluid mosaics of lipids and proteins Phospholipids - abundant Phospholipids are amphipathic molecules (has
More informationPlasma Membrane Structure and Function
Plasma Membrane Structure and Function The plasma membrane separates the internal environment of the cell from its surroundings. The plasma membrane is a phospholipid bilayer with embedded proteins. The
More informationCellular membranes are fluid mosaics of lipids and proteins.
Study Guide e Plasma Membrane You should be able to write out the definitions to each of the following terms in your own words: plasma membrane fluid mosaic integral proteins peripheral proteins receptor
More informationRama Abbady. Odai Bani-Monia. Diala Abu-Hassan
5 Rama Abbady Odai Bani-Monia Diala Abu-Hassan Lipid Rafts Lipid rafts are aggregates (accumulations) of sphingolipids. They re semisolid clusters (10-200 nm) of cholesterol and sphingolipids (sphingomyelin
More informationPlasma Membrane Function
Plasma Membrane Function Cells have to maintain homeostasis, they do this by controlling what moves across their membranes Structure Double Layer of phospholipids Head (polar) hydrophiliclikes water -
More informationMEMBRANE STRUCTURE AND FUNCTION
MEMBRANE STRUCTURE AND FUNCTION 2.4.2 Membranes organize the chemical activities of cells Membranes provide structural order for metabolism Form most of the cell's organelles Compartmentalize chemical
More informationBio 111 Study Guide Chapter 5 Membrane Transport and Cell Signaling
Bio 111 Study Guide Chapter 5 Membrane Transport and Cell Signaling BEFORE CLASS: Reading: Read the whole chapter from pp. 100-119. There are many great figures in this chapter. Make sure you study all
More informationClassification of Lipids
Classification of Lipids Neutral Lipids Amphipathic Lipids Amphipathic Lipids Most cell-membrane lipids are one of two main classes of amphipathic hydrolyzable lipids. Glycerophospholipids (phosphoglycerides):
More informationPaper 12: Membrane Biophysics Module 15: Principles of membrane transport, Passive Transport, Diffusion, Fick s law
Paper 12: Membrane Biophysics Module 15: Principles of membrane transport, Passive Transport, Diffusion, Fick s law LEARNING OBJECTIVES OF MODULE: We would begin this module by considering some general
More informationTerminology. Terminology. Terminology. Molarity number of moles of solute / Liter of solution. a) Terminology b) Body Fluid Compartments
Integrative Sciences: Biological Systems A Fall 2011 Body Fluids Compartments, Renal Clearance and Renal Excretion of Drugs Monday, November 21, 2011 Lisa M. Harrison-Bernard, Ph.D. Department of Physiology;
More informationBIOH111. o Cell Biology Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system
BIOH111 o Cell Biology Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system Endeavour College of Natural Health endeavour.edu.au 1 Textbook
More informationChapters 9 and 10 Lipids and Membranes
Chapters 9 and 10 Lipids and Membranes Lipids- a class of biological molecules defined by low solubility in water and high solubility in nonpolar solvents. Lipids contain or are derived from fatty acids.
More informationChapter 3b Cells Membrane transport - Student Notes
Chapter 3b Cells Membrane transport - Student Notes 1 Transport are permeable Some molecules the membrane; others do 2 Types of Membrane Transport processes No cellular required Substance its processes
More informationMembrane Structure & Function (Learning Objectives)
Membrane Structure & Function (Learning Objectives) Review the basic function and biochemical composition of the plasma membrane. Learn the fluid state of membranes and the movement of its lipids and proteins.
More informationBoundary Lipid bilayer Selectively Permeable Fluid mosaic of lipids and proteins Contains embedded proteins
1 Boundary Lipid bilayer Selectively Permeable Fluid mosaic of lipids and proteins Contains embedded proteins 2 Phosphate head hydrophilic Fatty acid tails hydrophobic Amphipathic Phosphate attracted to
More informationMembrane Structure and Function
Membrane Structure and Function What You Must Know: Why membranes are selectively permeable. The role of phospholipids, proteins, and carbohydrates in membranes. How water will move if a cell is placed
More information1. Double bilayer of with imbedded, dispersed 2. Bilayer consists of, cholesterol, and glycolipids
Bio Chapter 7.3 Cellular Movement Notes I. Background Information A. - a mixture in which the (molecules being ) never settle out in the (water). B. In a 25% Koolaid solution, how much water is there?
More informationCell Membranes Valencia college
6 Cell Membranes Valencia college 6 Cell Membranes Chapter objectives: The Structure of a Biological Membrane The Plasma Membrane Involved in Cell Adhesion and Recognition Passive Processes of Membrane
More information1.4 Page 1 Cell Membranes S. Preston 1
AS Unit 1: Basic Biochemistry and Cell Organisation Name: Date: Topic 1.3 Cell Membranes and Transport Page 1 1.3 Cell Membranes and Transport from your syllabus l. Cell Membrane Structure 1. Read and
More informationMembrane Structure and Function
Chapter 7 Membrane Structure and Function PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from
More informationLipids are macromolecules, but NOT polymers. They are amphipathic composed of a phosphate head and two fatty acid tails attached to a glycerol
d 1 2 Lipids are macromolecules, but NOT polymers. They are amphipathic composed of a phosphate head and two fatty acid tails attached to a glycerol backbone. The phosphate head group is hydrophilic water
More informationThe Cell Membrane and Homeostasis What is the cell membrane? A quick review A. Cell Membrane and Cell Transport. Unit 2: Cells and Cell Transport
Unit 2: Cells and Cell Transport Cell Membrane and Cell Transport Name: Directions: Go to https://shimkoscience.weebly.com/ and on the Biology page, find the document labelled Cell Membrane and Cell Transport
More informationMembrane Structure and Function - 1
Membrane Structure and Function - 1 The Cell Membrane and Interactions with the Environment Cells interact with their environment in a number of ways. Each cell needs to obtain oxygen and other nutrients
More informationChapter 7 Membrane Structure and Function. The plasma membrane surrounds the living cells from their surroundings.
Chapter 7 Membrane Structure and Function The plasma membrane surrounds the living cells from their surroundings. Only 8 nm thick (8,000 to equal the thickness of a sheet of paper) Controls passage of
More informationCells and Their Environment Chapter 8. Cell Membrane Section 1
Cells and Their Environment Chapter 8 Cell Membrane Section 1 Homeostasis Key Idea: One way that a cell maintains homeostasis is by controlling the movement of substances across the cell membrane. Homeostasis
More information[S] [S] Hypertonic [H O] [H 2 O] g. Osmosis is the diffusion of water through membranes! 15. Osmosis. Concentrated sugar solution
Concentrated sugar solution Sugar molecules (Water molecules not shown) 100ml 100ml Hypertonic [S] g [H2 Hypotonic [H O] 2 O] [H 2 O] g Semipermeable Dilute sugar solution (100ml) Time 125ml Osmosis 75ml
More informationLecture Series 5 Cellular Membranes
Lecture Series 5 Cellular Membranes Cellular Membranes A. Membrane Composition and Structure B. Animal Cell Adhesion C. Passive Processes of Membrane Transport D. Active Transport E. Endocytosis and Exocytosis
More informationPlasma Membrane Structure and Function
Plasma Membrane Structure and Function Chapter 7 Image from: http://www.biologie.uni-hamburg.de/b-online/ge22/03.gif Slide show modified from: http://www.explorebiology.com/pptap/2005/ http://facstaff.bloomu.edu/gdavis/links%20100.htm
More informationA. Membrane Composition and Structure. B. Animal Cell Adhesion. C. Passive Processes of Membrane Transport. D. Active Transport
Cellular Membranes A. Membrane Composition and Structure Lecture Series 5 Cellular Membranes B. Animal Cell Adhesion E. Endocytosis and Exocytosis A. Membrane Composition and Structure The Fluid Mosaic
More information