Podcast
Questions and Answers
What role does cholesterol play in the cellular membrane?
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?
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?
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?
Which component of the plasma membrane is involved in cell-to-cell recognition?
Which of the following is NOT a property of the lipid bilayer?
Which of the following is NOT a property of the lipid bilayer?
What is the function of glycolipids in the plasma membrane?
What is the function of glycolipids in the plasma membrane?
Which lipid class is characterized by having a glycerol backbone?
Which lipid class is characterized by having a glycerol backbone?
What contributes to the stability of the lipid bilayer structure?
What contributes to the stability of the lipid bilayer structure?
What role do peripheral membrane proteins primarily play in relation to the membrane?
What role do peripheral membrane proteins primarily play in relation to the membrane?
Which characteristic defines transmembrane proteins?
Which characteristic defines transmembrane proteins?
What type of proteins are anchored to membranes by hydrophobic carbon chains?
What type of proteins are anchored to membranes by hydrophobic carbon chains?
How do cytoskeletal filaments relate to peripheral proteins?
How do cytoskeletal filaments relate to peripheral proteins?
Which statement is true regarding the orientation of lipid-anchored proteins?
Which statement is true regarding the orientation of lipid-anchored proteins?
Which function is associated with membrane proteins involved in transport?
Which function is associated with membrane proteins involved in transport?
What is a common feature of both single-pass and multipass transmembrane proteins?
What is a common feature of both single-pass and multipass transmembrane proteins?
What primarily distinguishes integral membrane proteins from peripheral membrane proteins?
What primarily distinguishes integral membrane proteins from peripheral membrane proteins?
What occurs during the transition from E1 to E2 in the Na+/K+ ATPase mechanism?
What occurs during the transition from E1 to E2 in the Na+/K+ ATPase mechanism?
How do Na+ ions dissociate from the Na+/K+ ATPase during the E2 conformation?
How do Na+ ions dissociate from the Na+/K+ ATPase during the E2 conformation?
What happens to K+ ions during the transition from E2 to E1 in the Na+/K+ ATPase?
What happens to K+ ions during the transition from E2 to E1 in the Na+/K+ ATPase?
Which statement is true regarding the effect of certain drugs like ouabain on the Na+/K+ ATPase?
Which statement is true regarding the effect of certain drugs like ouabain on the Na+/K+ ATPase?
What drives the uphill transport of glucose into the cell at the apical end via the glucose-Na+ symport?
What drives the uphill transport of glucose into the cell at the apical end via the glucose-Na+ symport?
What role do microfilaments play in relation to membrane proteins?
What role do microfilaments play in relation to membrane proteins?
How does a hypotonic solution affect cells?
How does a hypotonic solution affect cells?
What is the primary function of the plasma membrane?
What is the primary function of the plasma membrane?
What happens when cells are placed in a hypertonic solution?
What happens when cells are placed in a hypertonic solution?
What distinguishes an isotonic solution for animal cells?
What distinguishes an isotonic solution for animal cells?
What is a key characteristic of the plasma membrane surrounding organelles?
What is a key characteristic of the plasma membrane surrounding organelles?
What is the process of osmosis primarily driven by?
What is the process of osmosis primarily driven by?
Which of the following best describes what happens to water during osmosis?
Which of the following best describes what happens to water during osmosis?
What is the primary energy source used by ATP-powered pumps during active transport?
What is the primary energy source used by ATP-powered pumps during active transport?
What characterizes the transport process via non-gated ion channels?
What characterizes the transport process via non-gated ion channels?
Which of the following best explains the concept of electrochemical gradient?
Which of the following best explains the concept of electrochemical gradient?
Which type of transporter does GLUT1 represent?
Which type of transporter does GLUT1 represent?
What primarily maintains the inside-negative electric potential of animal cell membranes?
What primarily maintains the inside-negative electric potential of animal cell membranes?
What differentiates gated channel proteins from non-gated channel proteins?
What differentiates gated channel proteins from non-gated channel proteins?
Which mechanism does a uniporter use to transport molecules?
Which mechanism does a uniporter use to transport molecules?
Which statement is true regarding the function of ATPases in active transport?
Which statement is true regarding the function of ATPases in active transport?
What is the primary role of the Na+/Ca2+ antiporter in cardiac muscle cells?
What is the primary role of the Na+/Ca2+ antiporter in cardiac muscle cells?
How do inhibitors of the Na+/K+ ATPase, like Digitalis, affect cardiac muscle contractions?
How do inhibitors of the Na+/K+ ATPase, like Digitalis, affect cardiac muscle contractions?
What effect does ouabain have on the Na+/K+ ATPase?
What effect does ouabain have on the Na+/K+ ATPase?
What is the function of V-class H+ ATPases?
What is the function of V-class H+ ATPases?
What is the mechanism of action for proton pump inhibitors?
What is the mechanism of action for proton pump inhibitors?
What causes a decrease in the strength of heart muscle contractions when the intracellular Na+ concentration increases?
What causes a decrease in the strength of heart muscle contractions when the intracellular Na+ concentration increases?
What is a potential therapeutic use of Na+/K+ ATPase inhibitors?
What is a potential therapeutic use of Na+/K+ ATPase inhibitors?
What role do cardiac glycosides like Digitalis play in the treatment of heart conditions?
What role do cardiac glycosides like Digitalis play in the treatment of heart conditions?
What is the rate limiting step in the de novo biosynthesis of pyrimidines?
What is the rate limiting step in the de novo biosynthesis of pyrimidines?
Which enzyme catalyzes the joining of carbamoyl phosphate and aspartate in pyrimidine biosynthesis?
Which enzyme catalyzes the joining of carbamoyl phosphate and aspartate in pyrimidine biosynthesis?
What role do ATP and CTP play in the activity of aspartate transcarbamoylase (ATCase)?
What role do ATP and CTP play in the activity of aspartate transcarbamoylase (ATCase)?
In de novo purine biosynthesis, which of the following is primarily synthesized from ribose-5-phosphate?
In de novo purine biosynthesis, which of the following is primarily synthesized from ribose-5-phosphate?
Which aspect of pyrimidine biosynthesis involves multiple active sites in the enzyme?
Which aspect of pyrimidine biosynthesis involves multiple active sites in the enzyme?
Which enzyme is primarily responsible for the synthesis of deoxyribonucleotides from ribonucleotides?
Which enzyme is primarily responsible for the synthesis of deoxyribonucleotides from ribonucleotides?
Which nucleotide must be converted to deoxyuridine diphosphate before producing deoxythymidine triphosphate?
Which nucleotide must be converted to deoxyuridine diphosphate before producing deoxythymidine triphosphate?
In the salvage pathway for pyrimidine nucleotides, which kinase is known for phosphorylating uridine?
In the salvage pathway for pyrimidine nucleotides, which kinase is known for phosphorylating uridine?
Which of the following statements is NOT true regarding ribonucleotide reductase?
Which of the following statements is NOT true regarding ribonucleotide reductase?
What is the end product of the synthesis pathway starting with uridine monophosphate (UMP)?
What is the end product of the synthesis pathway starting with uridine monophosphate (UMP)?
What is the product of the decarboxylation of orotidylate?
What is the product of the decarboxylation of orotidylate?
Which enzyme is involved in the conversion of UMP to UTP?
Which enzyme is involved in the conversion of UMP to UTP?
What role does CTP play in the regulation of pyrimidine biosynthesis?
What role does CTP play in the regulation of pyrimidine biosynthesis?
Which of the following statements about salvaged pyrimidine bases is true?
Which of the following statements about salvaged pyrimidine bases is true?
What is the initial component required to form a pyrimidine nucleotide?
What is the initial component required to form a pyrimidine nucleotide?
Which of the following accurately describes the salvage pathway of pyrimidine nucleotides?
Which of the following accurately describes the salvage pathway of pyrimidine nucleotides?
Which substrate is used in the synthesis of UTP from UMP?
Which substrate is used in the synthesis of UTP from UMP?
What is the primary function of cytidine deaminase in pyrimidine metabolism?
What is the primary function of cytidine deaminase in pyrimidine metabolism?
What distinguishes purines from pyrimidines in their molecular structure?
What distinguishes purines from pyrimidines in their molecular structure?
Which sugar component is found in RNA but not in DNA?
Which sugar component is found in RNA but not in DNA?
What is the role of the phosphate group in nucleotides?
What is the role of the phosphate group in nucleotides?
Which of the following correctly matches a nitrogenous base with its classification?
Which of the following correctly matches a nitrogenous base with its classification?
Which pathway for nucleotide synthesis involves recycling components from the breakdown of nucleic acids?
Which pathway for nucleotide synthesis involves recycling components from the breakdown of nucleic acids?
What type of linkage connects the phosphate group of one nucleotide to the sugar of the next nucleotide?
What type of linkage connects the phosphate group of one nucleotide to the sugar of the next nucleotide?
What suffix is used for purine bases in nucleoside nomenclature?
What suffix is used for purine bases in nucleoside nomenclature?
Which component is NOT a part of a nucleotide?
Which component is NOT a part of a nucleotide?
What are the two main pathways for nucleotide biosynthesis?
What are the two main pathways for nucleotide biosynthesis?
Which of the following nucleotides is a precursor to both adenine and guanine?
Which of the following nucleotides is a precursor to both adenine and guanine?
What is the primary role of nucleotides in the cell?
What is the primary role of nucleotides in the cell?
Which nitrogenous base is present in RNA but not in DNA?
Which nitrogenous base is present in RNA but not in DNA?
The synthesis of deoxyribonucleotides involves a conversion of which type of nucleotides?
The synthesis of deoxyribonucleotides involves a conversion of which type of nucleotides?
Which processes are considered anabolic in nucleic acid metabolism?
Which processes are considered anabolic in nucleic acid metabolism?
Which nucleotide is involved in cellular signaling as a secondary messenger?
Which nucleotide is involved in cellular signaling as a secondary messenger?
What is the significance of the pentose sugar in nucleotides?
What is the significance of the pentose sugar in nucleotides?
What is the final product of purine nucleotide catabolism that is excreted in urine?
What is the final product of purine nucleotide catabolism that is excreted in urine?
Which enzyme is critically important for purine salvage in rapidly dividing cells?
Which enzyme is critically important for purine salvage in rapidly dividing cells?
What is the first step in the degradation of guanosine?
What is the first step in the degradation of guanosine?
What disorder is associated with a deficiency in the enzyme adenosine deaminase?
What disorder is associated with a deficiency in the enzyme adenosine deaminase?
What is formed when dUTP is converted in the dUDP synthesis pathway?
What is formed when dUTP is converted in the dUDP synthesis pathway?
Which enzyme's defects can lead to the condition known as gout?
Which enzyme's defects can lead to the condition known as gout?
Which deoxyribonucleotide is synthesized directly from dUMP?
Which deoxyribonucleotide is synthesized directly from dUMP?
What is a common symptom of infants suffering from severe combined immunodeficiency (SCID)?
What is a common symptom of infants suffering from severe combined immunodeficiency (SCID)?
How does dATP affect the activity of ribonucleotide reductase?
How does dATP affect the activity of ribonucleotide reductase?
What type of crystals are formed due to the excretion of uric acid?
What type of crystals are formed due to the excretion of uric acid?
Which enzyme is primarily responsible for converting ribonucleotides to deoxyribonucleotides?
Which enzyme is primarily responsible for converting ribonucleotides to deoxyribonucleotides?
What is the underlying genetic cause of Lesch-Nyhan syndrome?
What is the underlying genetic cause of Lesch-Nyhan syndrome?
Which purine nucleotides inhibit the synthesis of phosphoribosylamine from PRPP?
Which purine nucleotides inhibit the synthesis of phosphoribosylamine from PRPP?
What effect does high concentration of purines have on pyrimidine biosynthesis?
What effect does high concentration of purines have on pyrimidine biosynthesis?
Which molecules regulate the selection of substrates in ribonucleotide reductase?
Which molecules regulate the selection of substrates in ribonucleotide reductase?
What type of mechanism does ribonucleotide reductase employ to convert ribonucleotides?
What type of mechanism does ribonucleotide reductase employ to convert ribonucleotides?
Which molecule serves as the source of sugar for purine nucleotides?
Which molecule serves as the source of sugar for purine nucleotides?
What feedback mechanism affects the enzyme catalyzed by glutamine-PRPP amidotransferase?
What feedback mechanism affects the enzyme catalyzed by glutamine-PRPP amidotransferase?
Which amino acids contribute nitrogen atoms (N2) in purine biosynthesis?
Which amino acids contribute nitrogen atoms (N2) in purine biosynthesis?
What is the primary consequence of AMP feedback inhibition in purine synthesis?
What is the primary consequence of AMP feedback inhibition in purine synthesis?
How do salvage reactions benefit nucleotide synthesis?
How do salvage reactions benefit nucleotide synthesis?
Which of the following is true about the regulation of AMP and GMP synthesis from IMP?
Which of the following is true about the regulation of AMP and GMP synthesis from IMP?
What role does PRPP play in purine nucleotide synthesis?
What role does PRPP play in purine nucleotide synthesis?
What is a characteristic of the salvage pathway in nucleotide synthesis?
What is a characteristic of the salvage pathway in nucleotide synthesis?
What role does dATP play in the regulation of ribonucleotide reductase?
What role does dATP play in the regulation of ribonucleotide reductase?
How does the binding of dTTP to ribonucleotide reductase affect nucleotide synthesis?
How does the binding of dTTP to ribonucleotide reductase affect nucleotide synthesis?
What condition is characterized by an elevation in serum uric acid concentration?
What condition is characterized by an elevation in serum uric acid concentration?
What is the primary consequence of increased uric acid levels in severe hyperuricemia?
What is the primary consequence of increased uric acid levels in severe hyperuricemia?
Which enzyme defect is associated with Lesch-Nyhan syndrome?
Which enzyme defect is associated with Lesch-Nyhan syndrome?
Which of the following nucleotides would enhance the production of dUDP and dCDP when binding to the specificity site of ribonucleotide reductase?
Which of the following nucleotides would enhance the production of dUDP and dCDP when binding to the specificity site of ribonucleotide reductase?
What normal serum uric acid concentration range is established for adults?
What normal serum uric acid concentration range is established for adults?
What condition can result from a lack of feedback control of PRPP glutamylamidotransferase?
What condition can result from a lack of feedback control of PRPP glutamylamidotransferase?
Flashcards
Peripheral membrane proteins
Peripheral membrane proteins
Proteins indirectly bound to the membrane via interactions with integral proteins or lipid head groups. They are located on either the cytosolic or exoplasmic face of the plasma membrane.
Integral membrane proteins
Integral membrane proteins
Proteins embedded within the lipid bilayer, often spanning the entire membrane.
Lipid-anchored proteins
Lipid-anchored proteins
Proteins attached to the membrane via a covalently attached lipid, with the lipid embedded in the bilayer. The protein itself doesn't enter the bilayer.
Transmembrane proteins
Transmembrane proteins
Signup and view all the flashcards
Transport proteins
Transport proteins
Signup and view all the flashcards
Membrane asymmetry
Membrane asymmetry
Signup and view all the flashcards
Cytoskeletal filaments
Cytoskeletal filaments
Signup and view all the flashcards
Single-pass transmembrane protein
Single-pass transmembrane protein
Signup and view all the flashcards
Plasma Membrane Function
Plasma Membrane Function
Signup and view all the flashcards
Fluid Mosaic Model
Fluid Mosaic Model
Signup and view all the flashcards
Phospholipid Bilayer
Phospholipid Bilayer
Signup and view all the flashcards
Amphipathic
Amphipathic
Signup and view all the flashcards
Membrane Permeability
Membrane Permeability
Signup and view all the flashcards
Cell-cell recognition
Cell-cell recognition
Signup and view all the flashcards
Cholesterol in Membrane
Cholesterol in Membrane
Signup and view all the flashcards
Phosphoglycerides
Phosphoglycerides
Signup and view all the flashcards
Active Transport
Active Transport
Signup and view all the flashcards
ATP-powered pumps
ATP-powered pumps
Signup and view all the flashcards
Non-gated Ion Channels
Non-gated Ion Channels
Signup and view all the flashcards
Electrochemical Gradient
Electrochemical Gradient
Signup and view all the flashcards
Gated Ion Channels
Gated Ion Channels
Signup and view all the flashcards
Uniporters
Uniporters
Signup and view all the flashcards
Facilitated Diffusion
Facilitated Diffusion
Signup and view all the flashcards
Glucose Transporter GLUT1
Glucose Transporter GLUT1
Signup and view all the flashcards
What is the function of membrane proteins in cell shape?
What is the function of membrane proteins in cell shape?
Signup and view all the flashcards
ECM and Intracellular Changes
ECM and Intracellular Changes
Signup and view all the flashcards
Plasma Membrane Barrier
Plasma Membrane Barrier
Signup and view all the flashcards
Plasma Membrane Permeability
Plasma Membrane Permeability
Signup and view all the flashcards
Organelle Membranes
Organelle Membranes
Signup and view all the flashcards
Osmosis
Osmosis
Signup and view all the flashcards
Hypotonic Solution
Hypotonic Solution
Signup and view all the flashcards
Isotonic Solution
Isotonic Solution
Signup and view all the flashcards
Na+/K+ ATPase: E1 to E2
Na+/K+ ATPase: E1 to E2
Signup and view all the flashcards
Na+/K+ ATPase: E2 to E1
Na+/K+ ATPase: E2 to E1
Signup and view all the flashcards
Na+/K+ ATPase: Role of Drugs
Na+/K+ ATPase: Role of Drugs
Signup and view all the flashcards
Na+/Glucose Symport: Location
Na+/Glucose Symport: Location
Signup and view all the flashcards
Na+/Glucose Symport: Mechanism
Na+/Glucose Symport: Mechanism
Signup and view all the flashcards
Digitalis effect on heart
Digitalis effect on heart
Signup and view all the flashcards
Na+/Ca2+ Antiporter Function
Na+/Ca2+ Antiporter Function
Signup and view all the flashcards
Digitalis and Congestive Heart Failure
Digitalis and Congestive Heart Failure
Signup and view all the flashcards
Ouabain Mechanism
Ouabain Mechanism
Signup and view all the flashcards
V-Class Proton Pumps
V-Class Proton Pumps
Signup and view all the flashcards
Proton Pump Inhibitors
Proton Pump Inhibitors
Signup and view all the flashcards
Carbamoyl Phosphate Synthetase II (CPS II)
Carbamoyl Phosphate Synthetase II (CPS II)
Signup and view all the flashcards
Aspartate Transcarbamoylase (ATCase)
Aspartate Transcarbamoylase (ATCase)
Signup and view all the flashcards
What is the rate-limiting step in pyrimidine biosynthesis?
What is the rate-limiting step in pyrimidine biosynthesis?
Signup and view all the flashcards
How is ATCase regulated?
How is ATCase regulated?
Signup and view all the flashcards
What are the two main steps in de novo pyrimidine biosynthesis?
What are the two main steps in de novo pyrimidine biosynthesis?
Signup and view all the flashcards
Deoxyribonucleotide
Deoxyribonucleotide
Signup and view all the flashcards
Ribonucleotide Reductase
Ribonucleotide Reductase
Signup and view all the flashcards
dTMP Synthesis
dTMP Synthesis
Signup and view all the flashcards
Salvage Pathway
Salvage Pathway
Signup and view all the flashcards
Kinase
Kinase
Signup and view all the flashcards
Orotidylate (OMP)
Orotidylate (OMP)
Signup and view all the flashcards
Uridylate (UMP)
Uridylate (UMP)
Signup and view all the flashcards
PRPP (Phosphoribosylpyrophosphate)
PRPP (Phosphoribosylpyrophosphate)
Signup and view all the flashcards
What is the source of the sugar in pyrimidine nucleotides?
What is the source of the sugar in pyrimidine nucleotides?
Signup and view all the flashcards
What are the sources of nitrogen in pyrimidine biosynthesis?
What are the sources of nitrogen in pyrimidine biosynthesis?
Signup and view all the flashcards
CTP (cytidine triphosphate)
CTP (cytidine triphosphate)
Signup and view all the flashcards
What is the role of ATP in pyrimidine biosynthesis?
What is the role of ATP in pyrimidine biosynthesis?
Signup and view all the flashcards
How is pyrimidine synthesis regulated?
How is pyrimidine synthesis regulated?
Signup and view all the flashcards
What is nucleic acid metabolism?
What is nucleic acid metabolism?
Signup and view all the flashcards
De novo vs. Salvage Pathways
De novo vs. Salvage Pathways
Signup and view all the flashcards
Purine Synthesis
Purine Synthesis
Signup and view all the flashcards
Pyrimidine Synthesis
Pyrimidine Synthesis
Signup and view all the flashcards
What are deoxyribonucleotides?
What are deoxyribonucleotides?
Signup and view all the flashcards
Purine Degradation
Purine Degradation
Signup and view all the flashcards
Pyrimidine Degradation
Pyrimidine Degradation
Signup and view all the flashcards
Purines
Purines
Signup and view all the flashcards
Pyrimidines
Pyrimidines
Signup and view all the flashcards
Nucleosides
Nucleosides
Signup and view all the flashcards
Nucleotides
Nucleotides
Signup and view all the flashcards
De novo Pathway
De novo Pathway
Signup and view all the flashcards
3’ - 5’ phosphodiester linkage
3’ - 5’ phosphodiester linkage
Signup and view all the flashcards
What is the difference between DNA and RNA?
What is the difference between DNA and RNA?
Signup and view all the flashcards
Purine Catabolism
Purine Catabolism
Signup and view all the flashcards
Adenosine Deaminase (ADA)
Adenosine Deaminase (ADA)
Signup and view all the flashcards
Severe Combined Immunodeficiency (SCID)
Severe Combined Immunodeficiency (SCID)
Signup and view all the flashcards
Uric Acid Build-up
Uric Acid Build-up
Signup and view all the flashcards
Gout
Gout
Signup and view all the flashcards
Lesch-Nyhan Syndrome
Lesch-Nyhan Syndrome
Signup and view all the flashcards
Purine Salvage
Purine Salvage
Signup and view all the flashcards
HGPRT Deficiency
HGPRT Deficiency
Signup and view all the flashcards
Thymidylate Synthase
Thymidylate Synthase
Signup and view all the flashcards
Deoxyribonucleotide Biosynthesis
Deoxyribonucleotide Biosynthesis
Signup and view all the flashcards
Regulation of Nucleotide Biosynthesis: Purines
Regulation of Nucleotide Biosynthesis: Purines
Signup and view all the flashcards
Regulation of Nucleotide Biosynthesis: Pyrimidines
Regulation of Nucleotide Biosynthesis: Pyrimidines
Signup and view all the flashcards
ATCase Feedback Inhibition
ATCase Feedback Inhibition
Signup and view all the flashcards
dUDP to dUMP
dUDP to dUMP
Signup and view all the flashcards
dUMP to dTMP
dUMP to dTMP
Signup and view all the flashcards
PRPP
PRPP
Signup and view all the flashcards
Purine Synthesis: Nitrogen Sources
Purine Synthesis: Nitrogen Sources
Signup and view all the flashcards
Branch Point in Purine Synthesis
Branch Point in Purine Synthesis
Signup and view all the flashcards
Regulation of Purine Synthesis
Regulation of Purine Synthesis
Signup and view all the flashcards
AMP
AMP
Signup and view all the flashcards
dATP regulation
dATP regulation
Signup and view all the flashcards
Specificity site
Specificity site
Signup and view all the flashcards
Hyperuricemia
Hyperuricemia
Signup and view all the flashcards
Purine salvage pathway
Purine salvage pathway
Signup and view all the flashcards
PRPP glutamylamidotransferase
PRPP glutamylamidotransferase
Signup and view all the flashcards
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.Â
- 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
Additional Resources
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
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.
