Diffusion

IntroductionDiffusion is the net movement of the same kind of molecules from an area of their higher concentration to their area of lower concentration.

The constant random motion of molecules is what enables diffusion to occur.

Molecules that are initially unequally distributed in a liquid or gas tend to move by diffusion throughout the medium until they are equally distributed. Diffusion is an important means of distributing materials within cells of passively moving substances through cell membranes.

In this experiment, the conditions that affect the rate at which various substances diffuse were observed.

Materials

6 cubes Sugar beet, strainer, water bath, 2-500-ml beaker 20% gelatin solution,3 test tubes, test tube rack, ice water, pencil, methylene blue.

MethodsA.2.

3. 4.

3 cubes of sugar beet were prepared and steamed for 10 seconds. Two 500ml beakers were filled with of water. 3 steamed and 3 unsteamed sugar beet were placed in each beaker.

4.The set-up was left undisturbed and was observed after 30 minutes and at the end of the period. B. 1. 3 test tubes filled with 10 ml of 20% gelatin were prepared and placed and placed in ice water for the gelatin to solidify.

2. Using a pencil, the level of the solidified gelatin in the test tube was marked. 3. 5ml of methylene blue was poured in each test tube to serve as dye. 4. Each test tube was placed in the locker (27C), oven (37C), and in the refrigerator (19C) for 48 hours.

Results and DiscussionA.Figure 1. Sugar beet at the start of the experiment

Unsteamed

Steamed

At the start of the experiment, the steamed sugar beet diffused faster than the unsteamed one covering the thin bottom part of the beaker.

Figure 2. Sugar beet after 30 minutes

Unsteamed

Steamed

After 30 minutes, the steamed sugar beet diffused in almost 20 ml part of the bottom; also a thick surface of the water was occupied by the diffused molecules. On the other hand, the molecules of the unsteamed sugar beet were occupying the bottom horizontally, and a thin part at the surface.

Figure 3. Sugar beet at the end of the period

Unsteamed

Steamed

At the end of the period, the steamed sugar beet were diffused in almost 50 ml part of the bottom; the remaining parts were filled with faint pink coloration. The water with unsteamed beet was characterized by faint pink coloration and the concentration at the bottom disappeared.

Every cell is surrounded by a selectively permeable membrane which regulates what gets into and out of the cell. Selectively permeable membranes are membranes which allow some substances to cross much more easily than other substances.

This living membrane is accountable for the difference in rate of diffusion of the 2 different set-ups. When you heat a beetroot, you disrupt the living membranes which prevents the passage of the anthocyanin molecules outside the cell.

B.Table 1. Temperature and Distance Readings

Storage Place

Temperature Readings (19C) (27C) (37C)

Distance Traveled by the dye (cm) 1.5 2 2.5

Inside the refrigerator Inside the locker Inside the oven

The temperature greatly affects the rate of diffusion. As the temperature increases, the rate of diffusion or the movement of molecules also increases.

Guttation

When leaves lose water as a liquid phase through special cells called hydathodes it is referred to as guttation.

These guttation "tears" appear at the leaf tips or margins and contain various salts, sugars and other organic substances. At night, transpiration usually does not occur because most plants have their stomata closed. When there is a high soil moisture level, water will enter plant roots.

The water will accumulate in the plant creating a slight root pressure. The root pressure forces some water to exude through special leaf tip or edge structures, hydathodes, forming drops. Root pressure provides the impetus for this flow, rather than transpirational pull.

Separation of Pigments

Introduction

All living organisms require energy for their metabolic processes. The ultimate source of this energy is the sun. Photosynthetic organisms, including plants convert light energy into the chemical energy of sugars, which can be used to power metabolism.

During photosynthesis, molecules referred to as pigments are used to capture light energy. In this experiment, the primary pigments of green plants were separated and identified using a technique called paper chromatography.

Materials

Papaya leaves, mortar and pestle, chromatography paper, test tube with cork, dropper, paper clip, solution containing a mixture of 95 parts of petroleum ether and 5 parts of acetone.

Methods

The extract of the papaya leaves was gathered by crushing the lamina in the mortar. The test tube was filled with 50 ml of the prepared solution. Drops of extract were placed 1cm above the part of the paper that touches the solution.

The paper was hang using a clip to ensure that it will not touch the sides of the test tube. The test tube was stopped using a cork. At the end of the period, the paper was secured for observation.

Results and Discussion

The paper shows the 3 main pigments separated from green plants using paper chromatography. The green part shows 2 types of chlorophyll- a and b. The top band of pigments in the separation are carotenoids called carotenes and appear yellowish-brown.

The chlorophyll pigments travels slower than the carotenoids.