Biology and Genetics

Biology and Genetics

Introduction to Biology and Genetics 3.1, 3.2

Observing Osmosis using Potato Cells

Abstract

This written presentation is a concise report on definition of osmosis and diffusion and its effect on potato cells. This information was used to conduct an experiment (Location: South East Essex College, Science department, 4th Floor, 08/10/2009 12:45pm) that investigates deciphering the water/salt content of three mystery solutions.

Three potato chunks approximately equal size were carved and introduced to each solution. The changes that occurred over a period of fifty minutes were recorded and are illustrated in table format and comparative graphs in this report.

Solution A proved to be hypotonic as it greatly increased in weight it had the most water, Solution B was isotonic as there was a small margin f change once the water had been absorbed and Solution C was Hypertonic (it has the most salt)

This information is a useful aid in understanding osmosis and diffusion and how it could be helpful in testing water for salt content.

Introduction

Diffusion describes the process when different sized molecules intermingle with their kinetic energy causing random motion. If two groups of different molecules are separated by a partition the molecules on either side's motion cause a large amount of collisions into the partition. If the partition is removed the random velocities of the molecules cause each group to intermingle and form equilibrium.

Osmosis is the diffusion of water from an area of high concentration to a low, it is a process found in living organisms. It is important because it is how water is transported in and out of living cells semi permeable membranes. Without it plants would not receive the nutrients they need or be able to survive in a changing environment.

In nature plants use osmosis to absorb water for photosynthesis. During osmosis the partly permeable membrane only allows small water molecules through for diffusion, leaving behind the large solute particles it cannot. Molecular diffusion (in this case transport of water molecules) can travel in both directions, in and out of the cells. The potato cells act in this way in an attempt to try to create equilibrium with their surrounding, so the last movement will be the transportation of molecules to the side with a lower concentration of water. . When a solution with a high salt concentration is added, the water from inside cells is drawn to it like a magnet causing the cells to shrink.

Potatoes are large bulbous vegetables made up of millions of cells in tight formation, for this reason it is easier to observe changes in size to more accurately produce comparable results when recording potato cells water potential.

This study was undertaken to distinguish three mystery solutions that each were an example of isotonic, hypotonic and hypertonic, by monitoring their effects on chunks of potato. An isotonic solution is a solution that has the same solute potential; hypotonic has a lower potential and hypertonic a higher.

Osmosis is a selective diffusion process driven by the internal energy of solvent molecules

Materials and Methods

Ø Potato + 3X Mystery Solutions

Ø Cork borer

Ø X3 Beakers

Ø Weigh boat

Ø Scales

Ø Stop watch

Ø Tweezers

Ø Thermometer

Ø Ruler

Location: South East Essex College, Science department, 4th Floor, 08/10/2009 12:45pm:

Using the cork borer three equal sized chunks of the potato were cut into cylinders. The three solutions labelled A to C were poured separately into the three beakers. The cylinders were weighed and measured. From the moment the stop watch was started a cylinder was dropped into the first beaker (Solution A) and in two minute intervals the second and third were dropped into solution B and C. This was to leave enough time to weigh and measure the size and temperature of each cylinder every time ten minutes had past for each. When the cylinders were taken out the solutions, tweezers were used to pick them out and then place them on weigh boat on scales.

Results of the Experiment:

Solution

A

B

C

Time (min)

Weight (g)

Temp (Kelvin)

Volume cm3

Weight (g)

Temp (Kelvin)

Volume cm3

Weight (g)

Temp (Kelvin)

Volume cm3

0

3.46

293.15

2.83

3.38

293.15

2.83

3.48

293.15

2.83

10

3.5

293.15

3.63

3.49

293.15

3.00

3.3

293.15

3.00

20

3.64

293.15

3.22

3.4

293.15

3.00

3.14

293.15

3.00

30

3.73

293.15

3.86

3.26

293.15

3.00

3.06

293.15

3.18

40

3.68

293.15

3.18

3.28

293.15

3.00

2.99

293.15

2.65

50

3.76

293.15

3.41

3.13

293.15

3.00

2.96

293.15

3.00

Discussion

The results (Figure 1, Figure 2) concluded that cylinder in solution A was hypotonic as the potato chunk greatly increased in weight, B was isotonic as there was small margin of change meaning the it was the most similar to the potato and C was hypertonic at it lost the most water due to its high salt concentration.

The temperature (Figure 4) remained a constant 20oC throughout the experiment maintained by the temperature of the room. The size (Figure 3) fluctuated slightly but not accurately as it was not symmetrical and one sample was accidentally dropped half way through the experiment. In the lab there may have been any number of residual chemicals on the floor and the impact of the sample hitting the floor would have disrupted the consistency of the findings. Next time it will be wise to cut the chunks larger, thus increasing the size of the reaction, making it easier to record observations. In addition to this using warmer water from the start should hasten the time of the experiment causing more kinetic collisions of the molecules.

4.1 Aerobic Respiration

C6H12O6+6O2à6CO2+6H2O

Glucose OxygenCarbon Dioxide Water

Figure 5 displays an equation that summarises Aerobic Respiration. It shows glucose breaking down in one simple step, ordinarily this would burn and create flames but inside of a cell the glucose is oxidised in a controlled way where the heat is regulated to prevent the cell being destroyed.

Aerobic Respiration is a complex process where food molecules are being broken down. Whilst they are being broken down energy is released and used to produce ATP (Adenosine Tri-Phosphate) out of ADP and inorganic phosphate. The heat produced in respiration is not high enough to burn the organism because it is released over many biochemical stages.

Figure 6 displays

Three main Stages:

Glycolysis or sugar splitting is the first stage of aerobic respiration. It takes place with or without oxygen present in the cytosol. Looking at the diagram opposite, one can see that Glycolysis starts with one molecule of glucose and ends with two Pyruvate (i.e. a three carbon compound derived from pyruvic acid).

Nicotinamide Adenine Dinucleotide (NAD [i.e. a nucleotide synthesised from Viteman B]) is reduced during this process and there is a net production of two ATP molecules.

This process takes a small amount of time to complete and does not require oxygen; this means it able to provide energy immediately.

Before Glycolysis begins, glucose is given activation energy which is provided by two molecules of ATP (See Figure 6). These break down into ADP (Adenosine Diphosphate) and inorganic phosphate. With the addition of phosphate the glucose is energised and first forms glucose 6-phosphate (or Neuberg ester which is fructose sugar phosphorylated on carbon 6). Then its forms Fructose

1, 6-disphosphate. At this point the cell has used two molecules of ATP (See Figure 6).

Fructose 1, 6-disphosphate then splits into two Glyceraldehyde 3-phosphate (G3P).

Each molecule of G3P is transformed into Pyruvate, during this process hydrogen atoms are removed (oxidisation). This process is linked with the production of ATP and the reduction of NAD+.

Each reaction that reduces oxygen (Redox) produces enough energy to synthesise two molecules of ATP. This means for every molecule of glucose broken down, four molecules of ATP are created, but because two molecules of ATP are used for activation energy the total is two.

If oxygen is available Pyruvate is converted to acetylcoenzyme which enters the Kreb Cycle (Figure 8). And the NADH can feed electrons into the electron transport system.

To keep a keep a consistent production of ATP the NADH must be oxidised back to NAD+.

If NADH releases hydrogen into the mitochondria, the oxygen is available for NAD+ to regenerate. Hydrogen moves into the electron transport system and creates six more molecules of ATP.

If oxygen is unavailable then the NAD+ is regenerated by fermentation where no more ATP molecules are generated. With this lack of oxygen Pyruvate can travel two different metabolic pathways: Alcoholic Fermentation (occurs in plants or lactate (lactic acid) fermentation.

Glycolysis

Krebs Cycle

Electron Transport System

ATP is when energy is released from glucose or other organic substrate with oxygen present.

In time glucose is broken down release energy. This energy is used to make ATP Adenosine Tri-Phosphate or ATP. ATP provides energy for processes such as muscle contractions. Aerobic respiration takes place in most life forms.

Very wise, glad your well.

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