Cell Membrane Transport Lab Report

Categories: Biology

Report, Pages 5 (1091 words)

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Introduction

A cell is the most basic structural and functional unit of every organism. It is the smallest unit of life that is capable of reproduction (Reece, 2014). Inside the cell, there are many features that help not only the cell itself but the entire organism. For example, the mitochondria, which produces ATP; the nucleus that tells itself when to divide or help another cell, or a cell membrane that tells whether beneficial or harmful things can leave or enter the cell.

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Without these specific organelles, among many others, the body would not be able to function the way it is supposed to (Sung, 2010).

Another feature that all cells have in common is the cell membrane, also known as the Phospholipid Bilayer. This selective barrier controls the traffic of what gets into and out of the cell. The main components of this membrane are lipids and proteins. The most abundant lipids are phospholipids, which have both a hydrophilic and a hydrophobic region.

The head of the phospholipid is hydrophilic, attracted to water, while the tails are hydrophobic, repelling water. Cholesterol, proteins, and other lipids are also part of this membrane (Reece, 2014).

Cell membranes are selectively permeable, allowing some substances to pass through while excluding others. This selective permeability is crucial for maintaining the cell's internal environment. Passive and active transport processes are responsible for moving substances across the cell membrane.

Passive Transport

Passive transport is the diffusion of a substance across a membrane with no energy investment (Reece, 2014). It includes diffusion, facilitated diffusion, osmosis, and filtration.

Simple diffusion and facilitated diffusion rely on concentration gradients, with facilitated diffusion involving membrane-bound carrier proteins. Osmosis specifically deals with the movement of water to equalize solute concentrations, while filtration depends on pressure gradients.

Active Transport

Active transport, in contrast, utilizes energy to move solutes against their concentration gradient (Reece, 2014). It requires energy, typically in the form of ATP, to transport molecules using membrane-bound proteins. Vesicular transport, such as endocytosis and exocytosis, also falls under active transport.

In this lab report, we conducted various experiments to explore different aspects of cell membrane transport mechanisms and permeability.

Materials and Methods

The experiments were conducted using a Mac Book Air computer, and the simulations were part of PhysioEx 9.1, authored by Peter Zao, Timothy Stabler Ph.D, Andrew Lokuta Ph.D, Edwin Griff Ph.D, and Lori Smith Ph.D. The lab manual used for reference was "Human Anatomy and Physiology Laboratory Manual" by Elaine N. Marieb, published in 2016 (twelfth edition, Pearson Education). Specific exercises from the manual were referenced for each activity.

Results

Activity 1: Simulating Dialysis

The results of the dialysis experiment are presented in Chart 1 below:

Membrane MWCO	Solutes	20	50	100	200
NaCl	Diffusion Rate (mM/min)	0.00	0.0150	0.0150	-
NaCl	Concentration (9mM)	9mM	9mM	9mM	9mM
Urea	Diffusion Rate (mM/min)	0.00	-	0.0094	-
Urea	Concentration (9mM)	9mM	9mM	9mM	9mM
Albumin	Diffusion Rate (mM/min)	-	-	-	0.000
Albumin	Concentration (9mM)	9mM	9mM	9mM	9mM
Glucose	Diffusion Rate (mM/min)	-	-	-	0.0042
Glucose	Concentration (9mM)	9mM	9mM	9mM	9mM

Chart 1: Dialysis Results (average diffusion rate in mM/min)

In Activity 1, we simulated dialysis to test the diffusion of various solutes across membranes with different molecular weight cutoffs (MWCO). The results showed that the diffusion rate depends on both the solute and the MWCO. NaCl and urea diffused more as the MWCO increased, but albumin and glucose showed limited diffusion. Albumin and glucose had minimal diffusion even with a 200 MWCO membrane.

Activity 2: Simulating Facilitated Diffusion

The results of the facilitated diffusion experiment are presented in Chart 2 below:

Glucose Concentration	Number of Glucose Carrier Proteins	500	2000	5000	10000
Extracellular Glucose (mM)	5.0	5.0	5.0	5.0	5.0
Facilitated Diffusion Rate (mM/min)	0.005	0.017	0.030	0.042	0.054

Chart 2: Facilitated Diffusion Results

In Activity 2, we simulated facilitated diffusion of glucose with different numbers of glucose carrier proteins. The results demonstrated that as the number of carrier proteins increased, the facilitated diffusion rate of glucose also increased, indicating a direct relationship between carrier protein abundance and facilitated diffusion rate.

Activity 3: Simulating Osmosis

The results of the osmosis experiment are presented in Chart 3 below:

Solute Concentration	Initial Volume (mL)	Final Volume (mL)	Net Change in Volume (mL)
Isotonic Solution	3.0	3.0	0.0
Hypotonic Solution	3.0	4.2	+1.2
Hypertonic Solution	3.0	1.8	-1.2

Chart 3: Osmosis Results

In Activity 3, we simulated osmosis by placing red blood cells in isotonic, hypotonic, and hypertonic solutions. The results showed that in an isotonic solution, there was no net change in cell volume. In a hypotonic solution, the cells gained water and swelled, leading to a positive net change in volume. In a hypertonic solution, the cells lost water and shrank, resulting in a negative net change in volume.

Activity 4: Simulating Filtration

The results of the filtration experiment are presented in Chart 4 below:

Pressure (mm Hg)	Glomerular Filtration Rate (mL/min)
50	94
75	141
100	188

Chart 4: Filtration Results

In Activity 4, we simulated glomerular filtration in the kidney. The results showed that as the pressure increased, the glomerular filtration rate also increased, indicating a positive correlation between pressure and filtration rate.

Discussion

The experiments conducted in this lab report provided valuable insights into different aspects of cell membrane transport mechanisms and permeability.

In Activity 1, we observed that solute diffusion across a membrane depends on both the solute size and the molecular weight cutoff (MWCO) of the membrane. Smaller solutes like NaCl and urea could pass through larger MWCO membranes more easily, while larger solutes like albumin and glucose had limited diffusion, even with a 200 MWCO membrane.

Activity 2 demonstrated that facilitated diffusion of glucose is directly related to the abundance of glucose carrier proteins. As the number of carrier proteins increased, the facilitated diffusion rate of glucose also increased.

Activity 3 illustrated the concept of osmosis, where the movement of water is influenced by the solute concentration. In an isotonic solution, there was no net change in cell volume, while in a hypotonic solution, cells gained water and swelled, and in a hypertonic solution, cells lost water and shrank.

Activity 4 simulated glomerular filtration in the kidney, showing that an increase in pressure resulted in a higher glomerular filtration rate. This finding reflects the physiological importance of maintaining adequate filtration in the kidney to regulate waste removal and fluid balance.

Conclusion

In conclusion, this lab report explored various aspects of cell membrane transport mechanisms and permeability. The experiments demonstrated the selective nature of cell membranes in allowing the passage of different solutes and the influence of factors such as solute size, carrier proteins, osmotic pressure, and hydrostatic pressure on membrane transport processes. Understanding these mechanisms is essential for comprehending the fundamental processes that occur within living cells.