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Questions and Answers
Which of the following statements accurately describes the role of GLUT proteins in facilitated diffusion?
Which of the following statements accurately describes the role of GLUT proteins in facilitated diffusion?
What effect does insulin have on GLUT4 in insulin-sensitive tissues?
What effect does insulin have on GLUT4 in insulin-sensitive tissues?
In facilitated diffusion, which factor is primarily responsible for the movement of glucose across the cell membrane?
In facilitated diffusion, which factor is primarily responsible for the movement of glucose across the cell membrane?
Which of the following statements about facilitated diffusion is incorrect?
Which of the following statements about facilitated diffusion is incorrect?
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What types of substances are primarily transported via the GLUT family of proteins?
What types of substances are primarily transported via the GLUT family of proteins?
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What is the definition of one osmole?
What is the definition of one osmole?
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How does the dissociation of a solute affect the osmole count?
How does the dissociation of a solute affect the osmole count?
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What happens to the concentrations of sodium ions inside cells compared to the extracellular fluid?
What happens to the concentrations of sodium ions inside cells compared to the extracellular fluid?
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What distinguishes active transport from simple diffusion?
What distinguishes active transport from simple diffusion?
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What is the relationship between glucose and osmoles in terms of its molecular weight?
What is the relationship between glucose and osmoles in terms of its molecular weight?
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In the context of solute dissociation, what is unique about sodium chloride's contribution to osmoles?
In the context of solute dissociation, what is unique about sodium chloride's contribution to osmoles?
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What is the primary function of active transport within cells regarding potassium and sodium ions?
What is the primary function of active transport within cells regarding potassium and sodium ions?
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Which of the following best describes simple diffusion?
Which of the following best describes simple diffusion?
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What triggers net movement of water across a selectively permeable membrane?
What triggers net movement of water across a selectively permeable membrane?
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How does osmotic pressure affect the movement of water in a sodium chloride solution?
How does osmotic pressure affect the movement of water in a sodium chloride solution?
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What happens to the cell when water moves across its membrane during osmosis?
What happens to the cell when water moves across its membrane during osmosis?
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What is the defining characteristic of the membrane involved in osmosis?
What is the defining characteristic of the membrane involved in osmosis?
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What occurs when there is zero net movement of water within a cell?
What occurs when there is zero net movement of water within a cell?
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Which factor can cause osmosis to slow down or stop?
Which factor can cause osmosis to slow down or stop?
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In the scenario of osmosis illustrated, which chamber includes pure water?
In the scenario of osmosis illustrated, which chamber includes pure water?
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Which statement correctly describes the role of osmosis in cells?
Which statement correctly describes the role of osmosis in cells?
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What is the role of ATPase activity in the sodium-potassium pump?
What is the role of ATPase activity in the sodium-potassium pump?
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How many sodium ions are extruded from the cell during one cycle of the sodium-potassium pump?
How many sodium ions are extruded from the cell during one cycle of the sodium-potassium pump?
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What happens when potassium ions bind to the carrier protein?
What happens when potassium ions bind to the carrier protein?
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Which ions are involved in the transport process of the sodium-potassium pump?
Which ions are involved in the transport process of the sodium-potassium pump?
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What is the electrochemical gradient's role in active transport?
What is the electrochemical gradient's role in active transport?
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What conformational change occurs in the carrier protein during ion transport?
What conformational change occurs in the carrier protein during ion transport?
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Which of the following correctly describes primary active transport?
Which of the following correctly describes primary active transport?
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What is the net ion movement during one cycle of the sodium-potassium pump?
What is the net ion movement during one cycle of the sodium-potassium pump?
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What is the osmotic pressure exerted by a concentration of 1 osmole per liter at 37°C?
What is the osmotic pressure exerted by a concentration of 1 osmole per liter at 37°C?
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How is 1 milliosmole per liter concentration related to osmotic pressure?
How is 1 milliosmole per liter concentration related to osmotic pressure?
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What is the calculated total osmotic pressure of body fluids at a 300-milliosmolar concentration?
What is the calculated total osmotic pressure of body fluids at a 300-milliosmolar concentration?
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Why is the measured osmotic pressure of body fluids lower than the calculated value?
Why is the measured osmotic pressure of body fluids lower than the calculated value?
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What is the average osmotic pressure of body fluids compared to the calculated value?
What is the average osmotic pressure of body fluids compared to the calculated value?
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What does the presence of many ions in body fluids imply about osmotic particles?
What does the presence of many ions in body fluids imply about osmotic particles?
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What is osmolarity primarily determined by?
What is osmolarity primarily determined by?
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Which statement accurately describes the effects of temperature on osmotic pressure?
Which statement accurately describes the effects of temperature on osmotic pressure?
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Study Notes
Facilitated Diffusion
- Facilitated diffusion allows substances like glucose and amino acids to cross cell membranes.
- At least 14 GLUT (glucose transporter) proteins identified, responsible for glucose transport in various tissues.
- GLUT proteins can also transport galactose and fructose, which have similar structures to glucose.
- GLUT4, activated by insulin, can increase glucose transport rates by 10- to 20-fold in insulin-sensitive tissues.
Osmosis Across Selectively Permeable Membranes
- Water is the most abundant substance to diffuse through cell membranes.
- Regular diffusion of water balances in both directions, keeping cell volume constant.
- A concentration difference can create net water movement across a membrane, affecting cell size—swelling or shrinking.
- Applying pressure to a sodium chloride solution can slow, stop, or reverse osmosis.
Osmotic Pressure
- Osmotic pressure defines how much pressure is needed to prevent water movement into a solution.
- At 37°C, a concentration of 1 osmol/L can exert approximately 19,300 mm Hg osmotic pressure.
- Actual osmotic pressure of body fluids averages around 5500 mm Hg, lower than calculated due to ion interactions in fluids.
Osmolarity and Osmolality
- Osmolarity expresses solution concentration in terms of particle numbers, measured in osmoles rather than mass.
- One osmole equals 1 gram molecular weight of a solute; for glucose, this is 180 grams.
- Dissociated solutes, like sodium chloride, yield more osmoles (e.g., 1 g of NaCl equals 2 osmoles).
Active Transport
- Active transport is key in moving ions against their concentration gradients.
- Sodium-potassium pump is a primary active transport mechanism transporting sodium ions out and potassium ions into cells.
- Active transport relies on energy, derived from ATP, to shift molecules uphill against gradients.
- An ATPase function in carrier proteins activates when specific ions are bound, triggering ATP cleavage and ion movement.
Example of Active Transport
- Sodium-potassium pump extrudes three sodium ions and brings two potassium ions into the cell, highlighting energy dependency and conformational changes of the carrier protein.
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Description
This quiz explores the postulated mechanisms behind facilitated diffusion, specifically focusing on glucose and amino acids' transport across cell membranes. It also highlights the various GLUT membrane proteins and their roles in transporting these molecules within different tissues.
