Updated: 22 March, 2006
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BIO 10
- Biology Lab; Tuesday: 15:00 hours to 17:50 hours




Definition process of using energy in sunlight to convert water and carbon dioxide into carbohydrates and oxygen. The process in green plants and certain other organisms by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.
Exercise #1

Phenol Red Dye

This is a pH indicator. It measures the concentration of H+ ions present in the test sample (liquid). Water is considered neutral with a pH of 7.0. Any solution with a pH higher than 7.0 to 14.0 is considered alkaline (Basic or a base). Solutions with a pH less than 7.0 are said to be acidic.

Acid solution = yellow color

Neutral solution = orange-pink

Basic solution = dark pink

Carbon dioxide lowers the pH of water once it dissolves in it. This is because it forms a weak acid upon dissolving and that acid frees up H+ ions.

Principle 1 Placing a plant that is performing photosynthesis in a solution will result in the conversion of dissolved CO2 (carbon dioxide) to oxygen gas. Because photosynthesis uses CO2 to make energy in the presence of light and chlorophyll. Therefore, resulting in the water becoming less acidic and more basic.

Carbon dioxide is used during photosynthesis

Oxygen is released

Principle 2

Photosynthesis needs light energy to drive the reaction.

Sunlight contains many wavelengths (colors) of light, some are better for photosynthesis than others.

Starch and other complex sugars (which are generated by the joining of simple sugars such as glucose formed by photosynthesis) form in the presence of appropriate enzymes

CO2 enters the plants mainly through the Stomata - the small opening on the underside of most leaves. For plants that live in water, the CO2 just dissolves in from the surrounding media.

Greasing the surface of a leaf will prevent the entry of CO2 and interrupt photosynthesis.


IN: Water, Carbon Dioxide, Light Energy

Light + CO2 + H2O __> (CH2O)n + O2.

OUT: Glucose, Oxygen
Land Plants Stomata on the underside of the Leaf to allow movement of gases in and out.  
Water Plants No Stomata. Gases are dissolved in the water that then diffuses in to the cells.

Coleus Plants

Variegated Leaves

A variegated leaf is a leaf with green and non-green parts. The green parts of the leaf photosynthesise because they contain chlorophyll.

Total absence of plastid pigments causes a sector of a leaf or stem to have white patches. This condition is termed variegation (Metrosideros). Variegation is produced when there is a cell mutation (cytological chimera), and all cells produced from that mutant mother cell lack the pigments, either because plastids are not present or the plastid cannot complete the manufacture of the pigment apparatus. White, therefore, is where color is missing. The zones where chloroplasts are not present are zones where no photosynthesis will occur, hence a variegated leaf has a lowered potential to fix carbon dioxide into sugars, and as a consequence, a variegated plant also tends to grow more slowly.

Variegated leaves occur rarely in nature but are extremely common among indoor and outdoor ornamentals, where they have been saved as horticultural oddities. Species with variegated individuals are sometimes found in the understory of tropical rain forest, and this habitat is the source of a number of variegated house plants. The appearance of variegation in the tropical forest understory, if not simply by accident, has not been given a plausible explanation.

Photopigments Chlorophylls

Two types of chlorophyll are found in plants and the green algae.

* chlorophyll a and
* chlorophyll b

The difference in their structures is shown in the figure (red disks).

In the chloroplast, both types are associated with integral membrane proteins in the thylakoid membrane.

Both chlorophylls absorb light most strongly in the red and violet parts of the spectrum. Green light is absorbed poorly. Thus when white light shines on chlorophyll-containing structures like leaves, green light is transmitted and reflected and the structures appear green.


Chloroplasts also contain carotenoids. These are also pigments with colors ranging from red to yellow.

Carotenoids absorb light most strongly in the blue portion of the spectrum. They thus enable the chloroplast to trap are larger fraction of the radiant energy falling on it.

Carotenoids are often the major pigments in flowers and fruits. The red of a ripe tomato and the orange of a carrot are produced by their carotenoids.

In leaves, the carotenoids are usually masked by the chlorophylls. In the autumn, as the quantity of chlorophyll in the leaf declines, the carotenoids become visible and produce the yellows and reds of autumn foliage.

Many animals use ingested beta-carotene as a precursor for the synthesis of vitamin A.

Spectral Analysis

A spectroscope contains a diffraction grating that separates electromagnetic radiation into its component wavelengths. The spectroscope can be used to measure absorption or emission spectra.

Just as a geologist collects rocks or minerals and a botanist collects plants, an astronomer collects light. Astronomers usually cannot touch the objects they study, like stars or galaxies. But they can analyze the light these celestial objects radiate using a spectroscope. When an astronomer looks at a star through a spectroscope, he or she sees a colorful spectrum that is full of information.

Here is the NASA site that talks about this topic.

and this one for the kid in us!

Chromatography Paper chromatography is a technique used to separate a mixture into its component molecules. The molecules migrate, or move up the paper, at different rates because of differences in solubility, molecular mass, and hydrogen bonding with the paper. As the solvent touches the pigment extract, each pigment within the extract moves at a different rate. In the end there should be four spots on the paper, each representing one of the four pigments. (chlorophyll a, chlorophyll b, xanthrophylls, and carotenoids)

Pigments move at different rates according to their ability to dissolve in the solvent. The pigment that dissolves the best moves up the paper the fastest.

WHAT! When early microbes evolved, some species developed ways to convert sunlight into cellular energy and to use that energy to capture carbon from the atmosphere. The origin of this process, known as photosynthesis, was crucial to the later evolution of plants. The publication today of the analysis of the complete genome sequence of an unusual photosynthetic microbe provides important insights into studies of how that light harvesting mechanism evolved and how it works today.

The bacterium, Chlorobium tepidum, was originally isolated from a hot spring in New Zealand. It is a member of the green-sulfur bacterial group, so known because of the microbes' color and their dependence on sulfur compounds to carry out photosynthesis. Biologists say green-sulfur bacteria are important because they perform photosynthesis in a different way from that of other bacteria and that of plants.

For example, instead of the choloroplasts found in plants, green-sulfur bacteria have organelles called chlorosomes that help generate energy through an electron-transport chain in the microbe's cytoplasmic membrane. Inside the chlorosomes, the chlorophyll and carotenoid molecules that capture light differ from the molecules that other species use to perform photosynthesis. Also, green-sulfur bacteria carry out photosynthesis in the absence of oxygen and do not produce oxygen as a byproduct as plants do.

Excluding a few photosynthetic protists and cyanobacteria, plant cells are the only cells that contain chloroplasts. These organelles carry out the processes of photosynthesis, converting light energy into chemical energy and storing it as sugar. As well as producing food for ecosystems, photosynthesis releases oxygen molecules as byproducts, which replenish atmospheric oxygen used in cellular respiration and form a layer of ozone, O3, which shields the earth from solar ultraviolet rays.





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