Biology Chapter: Plasma Membrane Structure
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Questions and Answers

What role does cholesterol play in the cellular membrane?

  • It stiffens the membrane by connecting phospholipids. (correct)
  • It acts as a signal molecule.
  • It forms the hydrophobic barrier of the bilayer.
  • It allows for cell communication.

    • What characteristic of phospholipids contributes to the formation of the lipid bilayer?

  • They are amphipathic with hydrophilic heads and hydrophobic tails. (correct)
  • They form single-layer membranes only.
  • They are all nonpolar molecules.
  • They spontaneously repel water.

    • Why is the hydrophobic core of the lipid bilayer important?

  • It allows the passage of water-soluble substances.
  • It prevents the diffusion of water-soluble (hydrophilic) solutes. (correct)
  • It facilitates the movement of lipids.
  • It enables cell division.

    • Which component of the plasma membrane is involved in cell-to-cell recognition?

    <p>Glycoproteins</p> Signup and view all the answers

    Which of the following is NOT a property of the lipid bilayer?

    <p>It has a hydrophilic core.</p> Signup and view all the answers

    What is the function of glycolipids in the plasma membrane?

    <p>To act as signal molecules.</p> Signup and view all the answers

    Which lipid class is characterized by having a glycerol backbone?

    <p>Phosphoglycerides</p> Signup and view all the answers

    What contributes to the stability of the lipid bilayer structure?

    <p>Hydrophobic interactions and van der Waals forces.</p> Signup and view all the answers

    What role do peripheral membrane proteins primarily play in relation to the membrane?

    <p>They interact with integral membrane proteins or lipid head groups.</p> Signup and view all the answers

    Which characteristic defines transmembrane proteins?

    <p>They can possess one or more membrane-spanning regions.</p> Signup and view all the answers

    What type of proteins are anchored to membranes by hydrophobic carbon chains?

    <p>Covalently attached lipid proteins.</p> Signup and view all the answers

    How do cytoskeletal filaments relate to peripheral proteins?

    <p>They interact indirectly through adapter proteins.</p> Signup and view all the answers

    Which statement is true regarding the orientation of lipid-anchored proteins?

    <p>They have an asymmetrical location relative to membrane faces.</p> Signup and view all the answers

    Which function is associated with membrane proteins involved in transport?

    <p>They provide a hydrophilic channel for solute transport.</p> Signup and view all the answers

    What is a common feature of both single-pass and multipass transmembrane proteins?

    <p>They possess at least one membrane-spanning region.</p> Signup and view all the answers

    What primarily distinguishes integral membrane proteins from peripheral membrane proteins?

    <p>Integral proteins penetrate the hydrophobic core of the bilayer.</p> Signup and view all the answers

    What occurs during the transition from E1 to E2 in the Na+/K+ ATPase mechanism?

    <p>The affinity for Na+ ions decreases.</p> Signup and view all the answers

    How do Na+ ions dissociate from the Na+/K+ ATPase during the E2 conformation?

    <p>They dissociate one at a time despite high extracellular Na+ concentration.</p> Signup and view all the answers

    What happens to K+ ions during the transition from E2 to E1 in the Na+/K+ ATPase?

    <p>They are released into the cytosol.</p> Signup and view all the answers

    Which statement is true regarding the effect of certain drugs like ouabain on the Na+/K+ ATPase?

    <p>They disrupt the Na+/K+ balance by inhibiting ATPase activity.</p> Signup and view all the answers

    What drives the uphill transport of glucose into the cell at the apical end via the glucose-Na+ symport?

    <p>The Na+ gradient established by the Na+ pump.</p> Signup and view all the answers

    What role do microfilaments play in relation to membrane proteins?

    <p>They assist in maintaining cell shape and stabilizing protein locations.</p> Signup and view all the answers

    How does a hypotonic solution affect cells?

    <p>Cells swell as water flows into them.</p> Signup and view all the answers

    What is the primary function of the plasma membrane?

    <p>To act as a permeability barrier.</p> Signup and view all the answers

    What happens when cells are placed in a hypertonic solution?

    <p>The cells will shrink as water exits.</p> Signup and view all the answers

    What distinguishes an isotonic solution for animal cells?

    <p>Has an equal total concentration of solutes to the cell interior.</p> Signup and view all the answers

    What is a key characteristic of the plasma membrane surrounding organelles?

    <p>It contains a unique set of essential proteins.</p> Signup and view all the answers

    What is the process of osmosis primarily driven by?

    <p>Differences in solute concentration.</p> Signup and view all the answers

    Which of the following best describes what happens to water during osmosis?

    <p>Water moves towards a low water concentration area.</p> Signup and view all the answers

    What is the primary energy source used by ATP-powered pumps during active transport?

    <p>ATP</p> Signup and view all the answers

    What characterizes the transport process via non-gated ion channels?

    <p>They allow the passage of ions down their concentration gradient.</p> Signup and view all the answers

    Which of the following best explains the concept of electrochemical gradient?

    <p>The combination of concentration gradient and electric potential affecting ion movement.</p> Signup and view all the answers

    Which type of transporter does GLUT1 represent?

    <p>Uniporter</p> Signup and view all the answers

    What primarily maintains the inside-negative electric potential of animal cell membranes?

    <p>Potassium efflux</p> Signup and view all the answers

    What differentiates gated channel proteins from non-gated channel proteins?

    <p>Gated proteins open in response to specific signals.</p> Signup and view all the answers

    Which mechanism does a uniporter use to transport molecules?

    <p>Facilitated diffusion down the gradient</p> Signup and view all the answers

    Which statement is true regarding the function of ATPases in active transport?

    <p>They move substances against a concentration or electric potential gradient.</p> Signup and view all the answers

    What is the primary role of the Na+/Ca2+ antiporter in cardiac muscle cells?

    <p>To maintain low intracellular Ca2+ concentration</p> Signup and view all the answers

    How do inhibitors of the Na+/K+ ATPase, like Digitalis, affect cardiac muscle contractions?

    <p>They increase the intracellular concentration of Ca2+</p> Signup and view all the answers

    What effect does ouabain have on the Na+/K+ ATPase?

    <p>It inhibits the pump and locks Na+ in</p> Signup and view all the answers

    What is the function of V-class H+ ATPases?

    <p>They acidify the lumen of specific organelles</p> Signup and view all the answers

    What is the mechanism of action for proton pump inhibitors?

    <p>They block the H+/K+ ATPase system irreversibly</p> Signup and view all the answers

    What causes a decrease in the strength of heart muscle contractions when the intracellular Na+ concentration increases?

    <p>Diminished activity of Na-Ca exchanger</p> Signup and view all the answers

    What is a potential therapeutic use of Na+/K+ ATPase inhibitors?

    <p>Management of congestive heart failure</p> Signup and view all the answers

    What role do cardiac glycosides like Digitalis play in the treatment of heart conditions?

    <p>They increase contractility of the heart muscle</p> Signup and view all the answers

    What is the rate limiting step in the de novo biosynthesis of pyrimidines?

    <p>Formation of carbamoyl phosphate from glutamine</p> Signup and view all the answers

    Which enzyme catalyzes the joining of carbamoyl phosphate and aspartate in pyrimidine biosynthesis?

    <p>Aspartate transcarbamoylase</p> Signup and view all the answers

    What role do ATP and CTP play in the activity of aspartate transcarbamoylase (ATCase)?

    <p>ATP stimulates and CTP inhibits</p> Signup and view all the answers

    In de novo purine biosynthesis, which of the following is primarily synthesized from ribose-5-phosphate?

    <p>IMP</p> Signup and view all the answers

    Which aspect of pyrimidine biosynthesis involves multiple active sites in the enzyme?

    <p>Formation of carbamoyl phosphate</p> Signup and view all the answers

    Which enzyme is primarily responsible for the synthesis of deoxyribonucleotides from ribonucleotides?

    <p>Ribonucleotide reductase</p> Signup and view all the answers

    Which nucleotide must be converted to deoxyuridine diphosphate before producing deoxythymidine triphosphate?

    <p>UDP</p> Signup and view all the answers

    In the salvage pathway for pyrimidine nucleotides, which kinase is known for phosphorylating uridine?

    <p>Uridine kinase</p> Signup and view all the answers

    Which of the following statements is NOT true regarding ribonucleotide reductase?

    <p>It directly synthesizes thymidine nucleotides.</p> Signup and view all the answers

    What is the end product of the synthesis pathway starting with uridine monophosphate (UMP)?

    <p>Deoxythymidine monophosphate (dTMP)</p> Signup and view all the answers

    What is the product of the decarboxylation of orotidylate?

    <p>Uridylate</p> Signup and view all the answers

    Which enzyme is involved in the conversion of UMP to UTP?

    <p>Nucleoside diphosphokinase</p> Signup and view all the answers

    What role does CTP play in the regulation of pyrimidine biosynthesis?

    <p>It serves as a feedback inhibitor of ATCase.</p> Signup and view all the answers

    Which of the following statements about salvaged pyrimidine bases is true?

    <p>They do not have any phosphates.</p> Signup and view all the answers

    What is the initial component required to form a pyrimidine nucleotide?

    <p>PRPP</p> Signup and view all the answers

    Which of the following accurately describes the salvage pathway of pyrimidine nucleotides?

    <p>They are formed without the need for phosphates.</p> Signup and view all the answers

    Which substrate is used in the synthesis of UTP from UMP?

    <p>ATP</p> Signup and view all the answers

    What is the primary function of cytidine deaminase in pyrimidine metabolism?

    <p>It converts cytidine to uridine.</p> Signup and view all the answers

    What distinguishes purines from pyrimidines in their molecular structure?

    <p>Purines have a six-membered nitrogen ring fused to an imidazole ring.</p> Signup and view all the answers

    Which sugar component is found in RNA but not in DNA?

    <p>Ribose</p> Signup and view all the answers

    What is the role of the phosphate group in nucleotides?

    <p>To link nucleotides together through a phosphodiester bond.</p> Signup and view all the answers

    Which of the following correctly matches a nitrogenous base with its classification?

    <p>Thymine - Pyrimidine</p> Signup and view all the answers

    Which pathway for nucleotide synthesis involves recycling components from the breakdown of nucleic acids?

    <p>Salvage pathway</p> Signup and view all the answers

    What type of linkage connects the phosphate group of one nucleotide to the sugar of the next nucleotide?

    <p>Phosphodiester linkage</p> Signup and view all the answers

    What suffix is used for purine bases in nucleoside nomenclature?

    <p>osine</p> Signup and view all the answers

    Which component is NOT a part of a nucleotide?

    <p>Glycerol</p> Signup and view all the answers

    What are the two main pathways for nucleotide biosynthesis?

    <p>De novo and salvage pathways</p> Signup and view all the answers

    Which of the following nucleotides is a precursor to both adenine and guanine?

    <p>IMP</p> Signup and view all the answers

    What is the primary role of nucleotides in the cell?

    <p>Serving as precursors for DNA and RNA</p> Signup and view all the answers

    Which nitrogenous base is present in RNA but not in DNA?

    <p>Uracil</p> Signup and view all the answers

    The synthesis of deoxyribonucleotides involves a conversion of which type of nucleotides?

    <p>Ribonucleotides to deoxyribonucleotides</p> Signup and view all the answers

    Which processes are considered anabolic in nucleic acid metabolism?

    <p>Biosynthesis of nucleotides</p> Signup and view all the answers

    Which nucleotide is involved in cellular signaling as a secondary messenger?

    <p>cAMP</p> Signup and view all the answers

    What is the significance of the pentose sugar in nucleotides?

    <p>It forms the backbone of RNA or DNA</p> Signup and view all the answers

    What is the final product of purine nucleotide catabolism that is excreted in urine?

    <p>Uric acid</p> Signup and view all the answers

    Which enzyme is critically important for purine salvage in rapidly dividing cells?

    <p>Adenosine deaminase</p> Signup and view all the answers

    What is the first step in the degradation of guanosine?

    <p>De-ribosylation</p> Signup and view all the answers

    What disorder is associated with a deficiency in the enzyme adenosine deaminase?

    <p>Severe combined immunodeficiency (SCID)</p> Signup and view all the answers

    What is formed when dUTP is converted in the dUDP synthesis pathway?

    <p>dUMP</p> Signup and view all the answers

    Which enzyme's defects can lead to the condition known as gout?

    <p>PRPP synthetase</p> Signup and view all the answers

    Which deoxyribonucleotide is synthesized directly from dUMP?

    <p>dTTP</p> Signup and view all the answers

    What is a common symptom of infants suffering from severe combined immunodeficiency (SCID)?

    <p>Severe and recurrent infections</p> Signup and view all the answers

    How does dATP affect the activity of ribonucleotide reductase?

    <p>It inhibits the enzyme.</p> Signup and view all the answers

    What type of crystals are formed due to the excretion of uric acid?

    <p>Sodium urate</p> Signup and view all the answers

    Which enzyme is primarily responsible for converting ribonucleotides to deoxyribonucleotides?

    <p>Ribonucleotide reductase</p> Signup and view all the answers

    What is the underlying genetic cause of Lesch-Nyhan syndrome?

    <p>Defect in hypoxanthine-guanine phosphoribosyltransferase (HGPRT)</p> Signup and view all the answers

    Which purine nucleotides inhibit the synthesis of phosphoribosylamine from PRPP?

    <p>AMP and GMP</p> Signup and view all the answers

    What effect does high concentration of purines have on pyrimidine biosynthesis?

    <p>It stimulates pyrimidine synthesis.</p> Signup and view all the answers

    Which molecules regulate the selection of substrates in ribonucleotide reductase?

    <p>ATP, dATP, dTTP, and dGTP</p> Signup and view all the answers

    What type of mechanism does ribonucleotide reductase employ to convert ribonucleotides?

    <p>Free radical mechanism</p> Signup and view all the answers

    Which molecule serves as the source of sugar for purine nucleotides?

    <p>Ribose 5-phosphate</p> Signup and view all the answers

    What feedback mechanism affects the enzyme catalyzed by glutamine-PRPP amidotransferase?

    <p>Inhibited by AMP, ADP, and ATP</p> Signup and view all the answers

    Which amino acids contribute nitrogen atoms (N2) in purine biosynthesis?

    <p>Glutamine, Aspartate, and Glycine</p> Signup and view all the answers

    What is the primary consequence of AMP feedback inhibition in purine synthesis?

    <p>Inhibits AMP conversion from IMP</p> Signup and view all the answers

    How do salvage reactions benefit nucleotide synthesis?

    <p>They provide nucleotides from breakdown products.</p> Signup and view all the answers

    Which of the following is true about the regulation of AMP and GMP synthesis from IMP?

    <p>Both AMP and GMP provide feedback for their respective synthesis pathways.</p> Signup and view all the answers

    What role does PRPP play in purine nucleotide synthesis?

    <p>It serves as a source of sugar and is essential for synthesizing purine nucleotides.</p> Signup and view all the answers

    What is a characteristic of the salvage pathway in nucleotide synthesis?

    <p>It uses intermediates from nucleotide degradation to form nucleotides.</p> Signup and view all the answers

    What role does dATP play in the regulation of ribonucleotide reductase?

    <p>It functions as a general inhibitor for all substrates.</p> Signup and view all the answers

    How does the binding of dTTP to ribonucleotide reductase affect nucleotide synthesis?

    <p>It inhibits the formation of deoxypyrimidines.</p> Signup and view all the answers

    What condition is characterized by an elevation in serum uric acid concentration?

    <p>Hyperuricemia</p> Signup and view all the answers

    What is the primary consequence of increased uric acid levels in severe hyperuricemia?

    <p>Deposits of uric acid crystals in soft tissues.</p> Signup and view all the answers

    Which enzyme defect is associated with Lesch-Nyhan syndrome?

    <p>HGPRT</p> Signup and view all the answers

    Which of the following nucleotides would enhance the production of dUDP and dCDP when binding to the specificity site of ribonucleotide reductase?

    <p>ATP</p> Signup and view all the answers

    What normal serum uric acid concentration range is established for adults?

    <p>3-7 mg/dl</p> Signup and view all the answers

    What condition can result from a lack of feedback control of PRPP glutamylamidotransferase?

    <p>Hyperuricemia</p> Signup and view all the answers

    Study Notes

    Biomembranes: Structure and Transport Mechanisms

    • Biomembranes are composed of lipids and proteins
    • The composition and structure of a membrane determine its physical characteristics
    • Membranes separate compartments inside and outside cells, and between intracellular compartments
    • Membranes act as a permeability barrier
    • Membranes regulate the exchange of substances to maintain a steady internal environment
    • Membranes enable cells to signal and communicate to other cells

    Learning Outcomes

    • Describe the fluid-mosaic model of membrane structure
    • List various lipid and protein types in the membrane and their functions
    • Predict the movement of molecules in diffusion and osmosis
    • Explain how molecules/ions enter and leave cells
    • Describe and explain specific examples of membrane transport
    • Explain how combinations of transport proteins enable cells to perform essential functions

    Membrane Structure: Prokaryotes

    • Prokaryotic cells have a plasma membrane, without any internal membrane-bound compartments

    Membrane Structure: Eukaryotes

    • Eukaryotic cells are partitioned into smaller organelles (nucleus being the largest)
    • Each organelle usually has one or more biomembranes
    • Biomembranes in organelles carry out specific cellular functions

    CELL ARCHITECTURE: Structure: Triacylglyceride

    • Triacylglycerols are composed of glycerol attached to three fatty acids.

    CELL ARCHITECTURE: Structure of Biomembranes

    • Biomembranes are primarily composed of phospholipids
    • Phospholipids are amphipathic with a hydrophilic head and hydrophobic tails.

    Structure of Biomembranes: Phospholipids

    • Phospholipids are amphipathic molecules.
    • Phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and phosphatidylinositol are important examples of phospholipids.

    Structure of Biomembranes: Phospholipid

    • Phospholipids arrange themselves in a bilayer structure:
      • Polar heads face outward towards the aqueous environment.
      • Nonpolar tails form the inner hydrophobic core.

    Plasma membranes: Functions

    • The lipid and proteins composition of a membrane determines its physical characteristics and functional properties
    • They isolate the cytoplasm from the external environment (acts as a permeability barrier).
    • They regulate the exchange of substances (helps the cell and organism maintain a steady internal environment).
    • They facilitate communication with other cells (signal transduction).
    • They also facilitate cell-to-cell recognition

    Cellular membrane

    • The fluid-mosaic model describes membrane structure and considers the fluidity and mosaic nature of the membrane.

    Cellular membranes are fluid mosaics of lipids and proteins

    • The fluid mosaic model describes the arrangement of lipids and proteins in the membrane, highlighting the membrane's fluidity and mosaic features.

    Components of the Plasma Membrane

    • Phospholipids have a hydrophilic head and hydrophobic tails, creating a barrier.
    • Cholesterol plays a role in stiffening by connecting phospholipids
    • Glycolipids are signal molecules
    • Glycoproteins have sugar chains (like antibodies) for cell-cell recognition

    Biomembranes: Lipid Composition and Structural Organisation

    • Phospholipids spontaneously form a sheet-like phospholipid bilayer in cells.
    • The hydrocarbon tails of the phospholipids within each layer (leaflet) form a hydrophobic core in the membrane.

    The Lipid Bilayer

    • The hydrophobic core of the lipid bilayer acts as a barrier, preventing the diffusion of water-soluble solutes.
    • Hydrophobic and van der Waals interactions maintain the stability of the bilayer structure

    Three Classes of Lipids in Biomembranes

    • Biomembranes are composed of phosphoglycerides, sphingolipids, and steroids (like cholesterol).
    • All these lipid classes are amphipathic, with a polar head group and a hydrophobic tail.

    Phosphoglycerides

    • Phosphoglycerides are derivatives of glycerol-3-phosphate.
    • A typical phosphoglyceride consists of two fatty acyl chains esterified to the glycerol phosphate and a polar head group attached to the phosphate group.

    Sphingolipids

    • Sphingolipids are derived from sphingosine, an amino alcohol with a long hydrocarbon chain.
    • Sphingolipids contain a long-chain fatty acid attached to the sphingosine amino group.
    • Sphingomyelin is an example of an abundant sphingolipid.

    Steroids: Cholesterol

    • Steroids have a four-ring hydrocarbon structure
    • Cholesterol is amphipathic because its hydroxyl group can interact with water.

    Lipid Composition Influences the Physical Properties of Membranes

    • Lipid composition affects membrane properties
    • Lipid composition influences membrane specialization
    • Membrane fluidity depends on the lipid composition and temperature.

    Lipid Composition of Membranes

    • Different membranes have different lipid compositions.
    • These differences in lipid composition often correspond to specializations of membrane functions like maintaining a particular fluidity that best suits the function.

    Membrane fluidity

    • Membrane fluidity depends on the lipid composition and temperature.

    Factors that affect membrane fluidity

    • Temperature affects membrane fluidity
    • Unsaturated hydrocarbon chains in phospholipids maintain membrane fluidity at lower temperatures.

    Membrane Lipids Are Distributed Unequally in the Exoplasmic and Cytosolic Leaflets

    • There is an asymmetry in lipid composition across the bilayer.

    Biomembranes: Protein Components and Basic Functions

    • Membrane proteins are the "mosaic" part of the membrane.
    • Membrane proteins are defined by their location within or on the surface of the membrane
    • The amount of proteins associated with biomembranes varies

    Protein Domains- Exoplasmic

    • Protein domains on the extracellular surface typically bind to other molecules.
    • Some domains bind to signaling proteins, ions, and small metabolites

    Protein Domains- Cytosolic

    • Cytosolic protein domains often form channels/pores for molecular movement
    • Some domains anchor the cytoskeleton or trigger intracellular signaling

    Proteins Interact with Membranes in Three Different Ways

    • Membrane proteins are classified into integral, lipid-anchored, and peripheral based on their relationship with the membrane.

    Integral membrane proteins

    • Integral proteins span the entire phospholipid bilayer.
    • Their hydrophilic parts interact with aqueous solutions.

    Integral membrane proteins cont. 

    • Most transmembrane proteins embedded in the membrane are glycosylated.

    Lipid-anchored membrane proteins

    • Lipid-anchored proteins are covalently bound to lipid molecules.

    Peripheral membrane proteins

    • Peripheral proteins are indirectly bound to the membrane or interact with integral proteins or lipid head groups
    • Peripheral proteins tend to be localized on either the cytosolic or exoplasmic face.

    Cytoskeletal Filaments

    • Cytoskeletal filaments are loosely associated with the membrane through peripheral proteins that maintain shape and cell structure.

    Secondary Structures in Transmembrane Proteins

    • Single-pass transmembrane proteins contain a single membrane-spanning alpha-helix.
    • Multi-pass transmembrane proteins contain multiple membrane-spanning alpha-helices.

    Transport Across Membranes

    Passive Transport: Diffusion

    • Simple diffusion allows small molecules across the membrane down their concentration gradients.
    • Facilitated diffusion uses membrane proteins to speed up diffusion of larger molecules unable to cross the membrane unaided.

    Active Transport

    • Active transport moves molecules against their concentration gradients.
    • It uses energy (such as from ATP hydrolysis).

    Transport: Non-gated Ion Channels

    • Non-gated ion channels are open much of the time.

    Non-gated Ion Channels

    • The inside of the plasma membrane has a negative electric potential (voltage).
    • Non-gated channels tend to be open much of the time and allow movement of specific ions.

    Transporters: Carriers & Channels

    • Uniporters transport a single substrate.
    • Symporters transport two or more molecules in the same direction,.
    • Antiporters transport two or more molecules in opposite directions

    Uniporter: Glucose Transporter GLUT1

    • GLUT1 is a uniporter that moves glucose into cells.
    • The concentration of glucose is generally higher in the blood than in the cell, driving glucose into the cell.

    Co-Transporters: Antiporters and Symporters

    • Symporters move two or more molecules in the same direction.
    • Antiporters move two or more molecules in the opposite directions.
    • Their movement is often coupled to the movement of a different molecule (like an ion) that is moving down its concentration gradient

    Co-transport by Symporters and Antiporters

    • This mechanism allows the movement of substances that are generally not easily transported

    SUMMARY - through the cell membrane

    • Passive and Active transport types exist.

    TRANSPORT SUMMARY

    • Summary about different transport methods (simple, facilitated, and active transports).

    TRANSPORT ACROSS MEMBRANES: ACTIVE TRANSPORT MECHANISMS

    • These proteins are called ATPases; they normally do not hydrolyze ATP into ADP and Pi unless ions or other molecules are simultaneously transported.

    Different Classes of Pumps Exhibit Characteristic Structural and Functional Properties

    • P, V, F, and ABC classes of ATP-powered pumps exist.
    • The types of molecules transported differs by class

    ATP-Powered Pumps: P-class

    • Na+/K+ ATPase, Ca2+ ATPases, and H+/K+ ATPase pumps are examples of P-class pumps.
    • They are involved in maintaining ionic gradients within cells.

    ATP-Powered Pumps: P-class (cont.)

    • Ca2+ ATPases have different cellular roles depending on location (muscle cell, etc.)

    ATP-Powered Pumps: P-class (cont.)

    ATP-Powered Pumps: F-class & V-class

    • F and V class pumps have structural similarities but function differently.
    • V-class pumps maintain low pH in intracellular organelles

    H+ Proton pump

    • ATPases transport H+ against a gradient in several different cellular locations.

    ATP-Powered Pumps: F-class

    ATP-Powered Pumps: F-class - mitochondria

    ATP-Powered Pumps: F-class - chloroplast

    • F-class proton pumps are also known as ATP synthases in mitochondria and chloroplasts

    ATP-Powered Pumps: ABC-superfamily

    • The ABC superfamily is a large and diverse group of transmembrane proteins that transport a variety of molecules

    ATP-Powered Pumps: ABC-superfamily (cont.)

    • ABC proteins have a structural organization that is quite different.

    ATP-Powered Pumps: ABC-superfamily (cont.)

    Ca2+ ATPase Transporter

    • SERCA pumps are examples of Ca2+ ATPases

    Ca2+ ATPase Pumps Ca2+ lons from the Cytosol into the Sarcoplasmic Reticulum

    • Ca2+ homeostasis is crucial in skeletal muscle contraction and relaxation.

    Mechanism of Action of the Ca2+ ATPase: Step 1

    Mechanism of action of the Ca2+ ATPase: Step 2

    Mechanism of action of the Ca2+ ATPase: Step 3

    Mechanism of action of the Ca2+ ATPase: Step 4

    Mechanism of action of the Ca2+ ATPase: Step 5

    Mechanism of action of the Ca2+ ATPase: Step 6

    P-class ion pumps

    • All P-class ion pumps are phosphorylated
    • Operate in similar ways
    • P-class pumps include Na+/K+ ATPase, H+/K+ ATPase, and Ca2+ ATPase pumps

    Na+/K+ ATPase Transporter

    • Na+/K+ ATPase is an antiport pump
    • It is responsible for maintaining internal Na+ and K+ ion concentration in animal cells.

    Na+/K+ ATPase Maintains the Intracellular Na + and K + Concentrations

    • Na+/K+ ATPase is vital for maintaining specific ion concentrations in cells.
    • The structure and role of the Na+/K+ pump are important factors to consider

    Na+/K+ ATPase

    • Na+/K+ ATPase moves ions against their concentration gradients.
    • It requires ATP to achieve proper movement direction.

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase (cont.)

    Mechanism of action of the Na+/K+ ATPase

    • Specific drugs can interfere with the Na+/K+ pump

    Na+/Glucose Symport

    • Na+ and glucose are co-transported into cells.

    Na+/Glucose Symport (cont.)

    • The Na+ gradient drives glucose transport
    • The Na+/K+ pump maintains the Na+ gradient crucial for this process.

    Na+/Glucose Symport (cont.)

    • Glucose is transported against its concentration gradient using the Na+ gradient

    Inhibitors of the Na+/K+ Pump: Digitalis

    • Digitalis inhibits the Na+/K+ pump, which can impact calcium levels and the strength of heart contractions.

    Na+-Linked Antiporter Exports Ca2+ from Cardiac Muscle Cells

    • Na+/Ca2+ antiporters regulate Ca2+ homeostasis in cardiac muscle cells.

    Na+-Linked Antiporter Exports Ca2+ from Cardiac Muscle Cells (cont.)

    Na+-Linked Antiporter Exports Ca2+ from Cardiac Muscle Cells (cont.)

    Inhibitors of the Na+/K+ Pump: Ouabain

    • Ouabain blocks the Na+/K+ pump by binding to a specific area in the pump protein.

    H+ ATPases Transporter

    V-Class H+ ATPases Pump Protons Across Lysosomal and Vacuolar Membranes

    Inhibitors of H+ ATPases Pump

    • Proton pump inhibitors are useful against excessive stomach acid caused by ulcers.

    ABC- superfamily Transporters

    ABC Transporters

    ABC Transporters (cont.)

    ABC Transporters

    ABC Transporters

    ABC Transporters

    ABC Transporters: CFTR

    ABC Transporters- MDR proteins

    ABC Transporters

    ABC Transporters- Blood-brain Barrier

    Causes of defects in ABC Transporters

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    Biomembranes: Structure and Transport Mechanisms PDF

    Description

    Explore the essential functions and characteristics of the plasma membrane in this quiz. Delve into topics such as lipid bilayer formation, membrane proteins, and cell recognition. Test your understanding of cholesterol's role, glycolipids, and the stability of the membrane structure.

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