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Questions and Answers
How does the surface area to volume ratio (SA:V) change as the radius of a spherical cell increases?
How does the surface area to volume ratio (SA:V) change as the radius of a spherical cell increases?
Which of the following is NOT a consequence of a lower SA:V ratio in larger cells?
Which of the following is NOT a consequence of a lower SA:V ratio in larger cells?
Which of the following molecules would diffuse easily across a cell membrane?
Which of the following molecules would diffuse easily across a cell membrane?
What is the SA:V ratio for a cube cell with a side length of 2 cm?
What is the SA:V ratio for a cube cell with a side length of 2 cm?
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Which of the following statements about the SA:V ratio is TRUE?
Which of the following statements about the SA:V ratio is TRUE?
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Which of the following scenarios would lead to an increased SA:V ratio in cells?
Which of the following scenarios would lead to an increased SA:V ratio in cells?
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Why is it beneficial for cells to maintain a high SA:V ratio?
Why is it beneficial for cells to maintain a high SA:V ratio?
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Which of the following processes would increase the surface area of a cell without significantly increasing its volume?
Which of the following processes would increase the surface area of a cell without significantly increasing its volume?
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What is the primary function of the sodium-potassium pump in active transport?
What is the primary function of the sodium-potassium pump in active transport?
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Which of the following is NOT a characteristic of passive transport?
Which of the following is NOT a characteristic of passive transport?
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How does dialysis address kidney failure?
How does dialysis address kidney failure?
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What is the primary mechanism by which oxygen is transferred from water to the blood in fish gills?
What is the primary mechanism by which oxygen is transferred from water to the blood in fish gills?
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What is the key difference between endocytosis and exocytosis?
What is the key difference between endocytosis and exocytosis?
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What orientation do the hydrophilic heads of phospholipids have in the cell membrane?
What orientation do the hydrophilic heads of phospholipids have in the cell membrane?
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What is the effect of cholesterol on the cell membrane at high temperatures?
What is the effect of cholesterol on the cell membrane at high temperatures?
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Which type of molecules can easily cross the plasma membrane?
Which type of molecules can easily cross the plasma membrane?
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What factor primarily dictates a cell's function in relation to its size?
What factor primarily dictates a cell's function in relation to its size?
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What is a consequence of a cell becoming too large?
What is a consequence of a cell becoming too large?
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Which of the following formulas represents the total surface area of a cuboidal cell?
Which of the following formulas represents the total surface area of a cuboidal cell?
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What happens to the surface area-to-volume ratio as a cell increases in size?
What happens to the surface area-to-volume ratio as a cell increases in size?
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In a spherical cell, what is the formula for calculating the volume?
In a spherical cell, what is the formula for calculating the volume?
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What is the primary difference between passive transport and active transport?
What is the primary difference between passive transport and active transport?
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What is a concentration gradient?
What is a concentration gradient?
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Which of the following describes facilitated diffusion?
Which of the following describes facilitated diffusion?
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What is the main function of ion channels in a cell membrane?
What is the main function of ion channels in a cell membrane?
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What best describes osmosis?
What best describes osmosis?
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What is the role of the solvent in a solution?
What is the role of the solvent in a solution?
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Which of the following statements about diffusion is correct?
Which of the following statements about diffusion is correct?
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Which one of the following molecules is typically transported via facilitated diffusion?
Which one of the following molecules is typically transported via facilitated diffusion?
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What happens to a cell placed in a hypertonic solution?
What happens to a cell placed in a hypertonic solution?
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In which environment will water move into the cell?
In which environment will water move into the cell?
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What is plasmolysis?
What is plasmolysis?
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In an isotonic solution, the cell's water movement will:
In an isotonic solution, the cell's water movement will:
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Active transport requires:
Active transport requires:
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Which statement about osmotic environments is accurate?
Which statement about osmotic environments is accurate?
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What does the contractile vacuole do in protozoa?
What does the contractile vacuole do in protozoa?
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In a hypotonic solution, the cell will:
In a hypotonic solution, the cell will:
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Which of the following correctly describes isotonic conditions?
Which of the following correctly describes isotonic conditions?
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Which factor influences the direction of osmosis?
Which factor influences the direction of osmosis?
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When a cell is placed in a solution with a higher concentration of solute, it is said to be in a:
When a cell is placed in a solution with a higher concentration of solute, it is said to be in a:
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What is the primary effect of a hypotonic environment on animal cells?
What is the primary effect of a hypotonic environment on animal cells?
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Study Notes
Cell Membrane Structure
- The cell membrane is a phospholipid bilayer
- Proteins are embedded in the bilayer, acting as channels for transporting materials
- Glycoproteins, glycolipids, and cholesterol are components of the cell membrane
- Peripheral proteins and filaments of the cytoskeleton are also present
Cell Membrane Orientation
- Hydrophilic heads of phospholipids face the aqueous environments (inside and outside the cell)
- Hydrophobic tails of phospholipids face inwards, away from the aqueous environments
Cholesterol and Fluidity
- Cholesterol maintains membrane fluidity at high and low temperatures.
- High temperatures: reduces membrane fluidity
- Low temperatures: reduces tight packing of phospholipids, improving fluidity
Selective Permeability
- Some substances cross the membrane more easily than others.
- Small, nonpolar, hydrophobic molecules pass easily (e.g., hydrocarbons, CO2, O2, N2)
- Hydrophilic molecules, large molecules, and ions have difficulty crossing and often need protein assistance
Cell Size and Function
- Cellular metabolism depends on cell size.
- Cells need a high surface area-to-volume ratio to effectively exchange materials across the plasma membrane.
- Large cells have less surface area compared to volume, leading to inefficient material exchange
- Small cells have a higher surface area-to-volume ratio that facilitates effective material exchange
Formulas
- Cuboidal Cells: Total surface area (SA)= height × width × number of sides × number of boxes; Total volume (V)= height × width × length × number of boxes
- Spherical Cells: SA= 4πr²; V= 4/3 πr³ ; SA:V ratio= SA/V
Practice Examples
- Cells with higher SA:V ratios are more efficient for material exchange.
Concentration Gradient
- A difference in the amount of substance between two areas.
- Example: water with food coloring (food coloring is most concentrated at place of addition)
Diffusion
- Movement of particles from an area of high concentration to low concentration.
- This process continues until dynamic equilibrium (constant concentration) is reached
- Movement is driven by kinetic energy of particles
Facilitated Diffusion
- Passive transport process where specific proteins assist larger or non-lipid soluble molecules across the cell membrane
- Carrier and channel proteins help in moving these molecules.
- Examples: Glucose
Diffusion Through Ion Channels
- Membrane proteins transport ions such as Na+, K+, Ca2+, and Cl-.
- Ion channels are specific for a given ion and can be controlled using concentration gradients or other signals
Osmosis
- Net movement of water across a semi-permeable membrane (from high to low water concentration)
- Water moves down the concentration gradient
- An example of diffusion and passive transport.
Solutions
- Solvent: A substance that dissolves a solute
- Solute: A substance that is dissolved in a solvent(e.g., sugar, salt dissolved in water)
- Water is the common solvent in living organisms
Direction of Osmosis
- Isotonic: Equal solute concentration inside and outside the cell (water moves in and out at equal rates)
- Hypotonic: Lower solute concentration outside the cell (water moves into the cell)
- Hypertonic: Higher solute concentration outside the cell (water moves out of the cell).
Dealing with Osmosis
- Contractile Vacuoles (protozoa): Pump out excess water
- Plasmolysis (plant cells): Water loss, turgor pressure decreases, wilting
- Cytolysis (animal cells): High turgor pressure, cell explodes
Active Transport
- Movement of substances against the concentration gradient (from low to high concentration)
- Requires energy (ATP)
- Examples: Sodium-Potassium Pump, Endocytosis, Exocytosis
Endocytosis
- Cell membrane engulfs substances, forming vesicles to bring substance into the cell.
- Includes Phagocytosis (solids) and Pinocytosis (liquids)
Exocytosis
- Vesicles carrying substances fuse with the cell membrane, releasing their contents outside the cell.
- It's involved in the release of hormones and neurotransmitters
Dialysis
- A process that utilizes diffusion to filter waste materials from blood in a damaged kidney
- A machine filters out wastes from the blood by diffusion while healthy blood is returned to the body.
Fish Gill Function
- Water and blood flow in opposite directions (countercurrent exchange) across the gill surface.
- Oxygen moves from the water to the blood.
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Description
Test your knowledge on the structure and function of cell membranes. This quiz covers key components such as phospholipids, proteins, and the role of cholesterol in membrane fluidity. Assess your understanding of selective permeability and membrane orientation.
