Cell Membrane Transport Lab: Step-by-Step Study Guidance

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Q1. What will happen to cells if placed in hypotonic, hypertonic, and isotonic solutions?

Background

Topic: Osmolarity and Tonicity

This question tests your understanding of how cells respond to different extracellular environments based on solute concentration differences.

Key Terms:

Hypotonic solution: Lower solute concentration outside the cell than inside.
Hypertonic solution: Higher solute concentration outside the cell than inside.
Isotonic solution: Equal solute concentration inside and outside the cell.
Osmosis: Movement of water across a semipermeable membrane from low to high solute concentration.

Step-by-Step Guidance

Recall that water moves by osmosis from areas of lower solute concentration to higher solute concentration.
For a hypotonic solution, consider what happens to water movement and cell volume.
For a hypertonic solution, think about the direction of water movement and its effect on the cell.
For an isotonic solution, determine if there is any net movement of water and how the cell's volume is affected.

Try solving on your own before revealing the answer!

Q2. Define Simple Diffusion.

Background

Topic: Simple Diffusion

This question checks your understanding of passive transport mechanisms across the cell membrane.

Key Terms:

Simple diffusion: Movement of molecules from an area of high concentration to low concentration without energy input or transport proteins.
Concentration gradient: Difference in concentration across a space.

Step-by-Step Guidance

Think about whether energy is required for simple diffusion.
Consider if a membrane protein is needed for this process.
Recall the direction molecules move relative to their concentration gradient.

Try solving on your own before revealing the answer!

Q3. Which solute(s) were able to pass through the 20 MWCO membrane?

Background

Topic: Membrane Permeability and Molecular Size

This question tests your understanding of how molecular weight cut-off (MWCO) affects solute movement across membranes.

Key Terms:

MWCO (Molecular Weight Cut-Off): The maximum molecular weight of solutes that can pass through a membrane.

Step-by-Step Guidance

Review the molecular weights of the solutes used in your experiment.
Compare each solute's molecular weight to the 20 MWCO value.
Identify which solutes have a molecular weight less than or equal to 20 and thus can pass through the membrane.

Try solving on your own before revealing the answer!

Q4. According to your results, which solute had the highest molecular weight?

Background

Topic: Molecular Size and Diffusion

This question asks you to interpret experimental data to determine which solute is the largest based on molecular weight.

Key Terms:

Molecular weight: The mass of one molecule of a substance, usually measured in Daltons or g/mol.

Step-by-Step Guidance

List the solutes used in your experiment and their molecular weights.
Compare the values to determine which is the highest.

Try solving on your own before revealing the answer!

Q5. Which solute displayed the highest rate of diffusion through the 200 MWCO membrane?

Background

Topic: Diffusion Rate and Membrane Permeability

This question tests your ability to analyze which solute moves fastest through a membrane with a specific MWCO.

Key Terms:

Rate of diffusion: How quickly a solute moves across a membrane.
MWCO: Determines which solutes can pass based on size.

Step-by-Step Guidance

Identify which solutes are small enough to pass through the 200 MWCO membrane.
Review your experimental data for the rates at which these solutes diffused.
Determine which solute had the highest rate based on your observations.

Try solving on your own before revealing the answer!

Q6. What is the relationship between the rate of diffusion and the size of the solute?

Background

Topic: Diffusion Principles

This question examines your understanding of how molecular size affects diffusion rates across membranes.

Key Terms:

Diffusion rate: Speed at which molecules move from high to low concentration.
Molecular size: The physical size or mass of a molecule.

Step-by-Step Guidance

Recall Fick's Law, which relates diffusion rate to molecular size.
Consider whether larger or smaller molecules diffuse faster through a membrane.
Think about how the size of the solute affects its ability to pass through pores in the membrane.

Try solving on your own before revealing the answer!

Q7. Define Facilitated Diffusion.

Background

Topic: Facilitated Diffusion

This question tests your understanding of how certain molecules cross the cell membrane with the help of proteins.

Key Terms:

Facilitated diffusion: Passive movement of molecules across the membrane via transport proteins.
Carrier protein: Membrane protein that assists in the transport of specific substances.

Step-by-Step Guidance

Consider whether energy is required for facilitated diffusion.
Think about the role of membrane proteins in this process.
Recall the direction of movement relative to the concentration gradient.

Try solving on your own before revealing the answer!

Q8. Did any of the substances travel against their concentration gradient in facilitated diffusion?

Background

Topic: Directionality of Transport

This question checks your understanding of whether facilitated diffusion can move substances from low to high concentration.

Key Terms:

Concentration gradient: Difference in concentration across a membrane.
Passive transport: Movement without energy input, typically down the gradient.

Step-by-Step Guidance

Recall the definition of facilitated diffusion and whether it requires energy.
Think about the direction substances move in passive transport processes.
Review your experimental results to see if any substances moved from low to high concentration.

Try solving on your own before revealing the answer!

Q9. What are two ways to increase the rate of glucose transport?

Background

Topic: Factors Affecting Facilitated Diffusion

This question asks you to consider what variables can enhance the movement of glucose across the membrane.

Key Terms:

Transport protein: Protein that helps move substances across the membrane.
Concentration gradient: The difference in glucose concentration across the membrane.

Step-by-Step Guidance

Think about how increasing the number of transport proteins might affect glucose movement.
Consider how changing the concentration gradient could impact the rate of transport.
Review your lab data for any other factors that influenced glucose transport.

Try solving on your own before revealing the answer!

Q10. Did NaCl affect glucose transport?

Background

Topic: Interaction of Solutes in Transport

This question tests your understanding of whether the presence of NaCl influences the movement of glucose across the membrane.

Key Terms:

Competitive inhibition: When one solute interferes with the transport of another.

Step-by-Step Guidance

Review your experimental results for glucose transport in the presence and absence of NaCl.
Consider if the rate of glucose transport changed when NaCl was present.
Think about possible mechanisms for any observed effect.

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Q11. Did NaCl require a transport protein for diffusion?

Background

Topic: Membrane Permeability and Ion Transport

This question asks you to consider whether NaCl can cross the membrane by simple diffusion or needs a protein.

Key Terms:

Ion channel: Protein that allows ions to pass through the membrane.
Simple diffusion vs. facilitated diffusion: Whether a protein is required for movement.

Step-by-Step Guidance

Recall the properties of Na+ and Cl- ions and their ability to cross lipid bilayers.
Think about whether charged particles can diffuse freely through the membrane.
Review your lab results for evidence of protein involvement in NaCl transport.

Try solving on your own before revealing the answer!

Q12. Define Osmosis.

Background

Topic: Osmosis

This question tests your understanding of water movement across membranes in response to solute concentration differences.

Key Terms:

Osmosis: Diffusion of water across a semipermeable membrane from low to high solute concentration.

Step-by-Step Guidance

Consider whether osmosis requires energy input.
Think about the direction of water movement relative to solute concentration.
Recall the role of the semipermeable membrane in osmosis.

Try solving on your own before revealing the answer!

Q13. For NaCl, which MWCO membrane(s) provided for the net movement of water without movement of NaCl?

Background

Topic: Selective Permeability and Osmosis

This question asks you to identify which membranes allowed water to move but not NaCl, leading to osmosis.

Key Terms:

MWCO: Determines which molecules can pass through the membrane.
Osmosis: Water movement when solutes cannot cross the membrane.

Step-by-Step Guidance

Review the molecular weight of NaCl and the MWCO values of the membranes used.
Identify which membranes allowed water but not NaCl to pass.
Relate this to the observation of net water movement (osmosis).

Try solving on your own before revealing the answer!

Q14. Is osmotic pressure generated if solutes diffuse freely?

Background

Topic: Osmotic Pressure

This question tests your understanding of the conditions required for osmotic pressure to develop across a membrane.

Key Terms:

Osmotic pressure: The pressure required to stop osmosis.
Semipermeable membrane: Allows some molecules to pass but not others.

Step-by-Step Guidance

Recall what causes osmotic pressure to develop (difference in solute concentration across a membrane).
Consider what happens if both solute and water can move freely across the membrane.
Think about whether a pressure difference would be needed to stop water movement in this case.

Try solving on your own before revealing the answer!

Q15. Explain how solute concentration affects osmotic pressure.

Background

Topic: Osmotic Pressure and Solute Concentration

This question asks you to relate changes in solute concentration to changes in osmotic pressure.

Key Formula:

Where:

= osmotic pressure
= van 't Hoff factor (number of particles the solute dissociates into)
= molarity of the solution
= ideal gas constant
= temperature in Kelvin

Step-by-Step Guidance

Recall the formula for osmotic pressure and identify each variable.
Consider how increasing solute concentration () affects .
Think about the effect of temperature and the number of particles () on osmotic pressure as well.

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Q16. Define Filtration.

Background

Topic: Filtration

This question tests your understanding of how pressure forces fluid and solutes through a membrane.

Key Terms:

Filtration: Movement of water and solutes across a membrane due to hydrostatic pressure.
Hydrostatic pressure: The force exerted by a fluid against a surface.

Step-by-Step Guidance

Consider whether filtration is an active or passive process.
Think about the role of pressure in driving filtration.
Recall where in the body filtration is especially important (e.g., kidneys).

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Q17. Which MWCO membrane had the greatest filtration rate?

Background

Topic: Filtration Rate and Membrane Pore Size

This question asks you to analyze how membrane pore size affects the rate of filtration.

Key Terms:

Filtration rate: Volume of fluid filtered per unit time.
MWCO: Indicates pore size of the membrane.

Step-by-Step Guidance

Review the MWCO values of the membranes used in your experiment.
Recall how pore size affects the ease with which fluid and solutes pass through.
Identify which membrane allowed the most fluid to pass in the shortest time.

Try solving on your own before revealing the answer!

Q18. What is the relationship between pore size and filtration rate?

Background

Topic: Filtration Principles

This question tests your understanding of how the size of membrane pores influences the rate at which filtration occurs.

Key Terms:

Pore size: Diameter of openings in the membrane.
Filtration rate: Speed of fluid movement through the membrane.

Step-by-Step Guidance

Consider how increasing pore size might affect the movement of water and solutes.
Think about whether larger pores allow for faster filtration rates.
Relate this to your experimental observations.

Try solving on your own before revealing the answer!

Q19. Which solute did not appear in the filtrate using any of the membranes?

Background

Topic: Selective Filtration

This question asks you to identify which solute was too large to pass through any of the membranes used.

Key Terms:

Filtrate: The fluid that has passed through the membrane.
MWCO: Determines which solutes can pass based on size.

Step-by-Step Guidance

List the solutes used and their molecular weights.
Compare each solute's size to the MWCO values of the membranes.
Identify which solute was excluded from the filtrate in all cases.

Try solving on your own before revealing the answer!

Q20. What happens when you increase the driving pressure?

Background

Topic: Filtration and Pressure

This question tests your understanding of how changes in pressure affect the rate of filtration.

Key Terms:

Driving pressure: The force pushing fluid through the membrane.
Filtration rate: Volume of fluid filtered per unit time.

Step-by-Step Guidance

Recall the relationship between pressure and fluid movement across a membrane.
Consider how increasing pressure might affect the rate at which fluid and solutes are filtered.
Relate this to your experimental observations.

Try solving on your own before revealing the answer!

Q21. How do you think blood pressure affects filtration in the kidneys?

Background

Topic: Renal Physiology and Filtration

This question asks you to apply your understanding of filtration to a physiological context (the kidneys).

Key Terms:

Glomerular filtration: The process by which the kidneys filter blood, removing excess wastes and fluids.
Blood pressure: The force of circulating blood on the walls of blood vessels.

Step-by-Step Guidance

Recall how filtration occurs in the glomerulus of the kidney.
Consider how changes in blood pressure might affect the rate of filtration.
Think about the consequences of increased or decreased filtration rates for kidney function.

Try solving on your own before revealing the answer!

Q22. Define Active Transport.

Background

Topic: Active Transport

This question tests your understanding of how cells move substances against their concentration gradients using energy.

Key Terms:

Active transport: Movement of molecules across a membrane from low to high concentration using energy (usually ATP).
ATP: Adenosine triphosphate, the energy currency of the cell.

Step-by-Step Guidance

Consider whether energy is required for active transport.
Think about the direction of movement relative to the concentration gradient.
Recall examples of active transport in cells (e.g., sodium-potassium pump).

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Q23. With 1 mM ATP added to the cell interior, was all the Na+ moved into the extracellular space? Why or why not?

Background

Topic: Active Transport and ATP Dependence

This question asks you to analyze whether the addition of ATP was sufficient for complete sodium transport and why.

Key Terms:

Sodium-potassium pump: An active transport protein that moves Na+ out and K+ into the cell using ATP.
ATP: Provides energy for the pump to function.

Step-by-Step Guidance

Recall the mechanism of the sodium-potassium pump and its ATP requirement.
Consider whether 1 mM ATP is sufficient for all Na+ to be transported out.
Think about possible limiting factors (e.g., number of pumps, ATP availability, saturation).

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Q24. Describe the effect of decreasing the number of sodium-potassium pumps.

Background

Topic: Active Transport Capacity

This question tests your understanding of how the number of transport proteins affects the rate of active transport.

Key Terms:

Sodium-potassium pump: Moves Na+ out and K+ into the cell using ATP.
Transport capacity: The maximum rate at which a substance can be moved across the membrane.

Step-by-Step Guidance

Consider how the number of pumps relates to the rate of sodium and potassium movement.
Think about what happens to transport rate if the number of pumps decreases.
Relate this to your experimental observations or theoretical understanding.

Try solving on your own before revealing the answer!

Q25. How are you able to show the movement of sodium is due to active transport and not simple diffusion?

Background

Topic: Distinguishing Active Transport from Diffusion

This question asks you to identify experimental evidence that sodium movement is active, not passive.

Key Terms:

Active transport: Requires energy and moves substances against their gradient.
Simple diffusion: Passive movement down the concentration gradient.

Step-by-Step Guidance

Consider whether sodium moves against its concentration gradient in your experiment.
Think about the effect of removing ATP on sodium movement.
Identify any other evidence that distinguishes active transport from diffusion (e.g., specificity, saturation).