SCIENTIFIC METHODS

In this lab you will learn to form a hypothesis, conduct experiments around that hypothesis, and collect and analyze data.
One of the most important characteristics of modern science is its quantitative approach to solving problems. One of the first scientists to use quantitative methods was William Harvey, who discovered that blood circulated through the body. At the time Harvey began his work, anatomists believed that the liver produced blood from the food that the body consumed. The blood was then carried by veins to the heart, purified in the lungs, and then pumped to the various organs of the body, where it was consumed. Harvey measured that the left ventricle of the heart held roughly 100 ml of blood. He also measured that the heart beats an average of 64 times per minute.

CATALASE

Observing an enzyme

In this lab, you will study an enzyme that is found in the cells of many living tissues. The name of the enzyme is catalase (KAT-uh-LAYSS); it speeds up a reaction which breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances--water and oxygen.

By the Enzyme Lactase

Enzymes are important components of digestion because they break down large food molecules into smaller chemical subunits. One digestive enzyme, lactase, breaks down lactose (a disaccharide found in milk) into the monosaccharides glucose and galactose. In this investigation you will observe the effectiveness of a milk-treatment product that contains lactase by testing milk samples for the presence of glucose.

Amylase

In this experiment you will observe the action of the enzyme amylase on starch. Amylase is found in our saliva. Amylase changes starch into a simpler form: the sugar maltose, which will react positively with Benedict's solution.

Amylase

The seed is a remarkable structure that enables seed plants to survive unfavorable conditions. Each seed contains an embryo that can grow into a mature plant. In addition, the seeds of flowering plants have structures called cotyledons. The cotyledons store food for use by the embryo in the form of starch. Starch is long chains of glucose molecules. The embryo needs to break these chains, forming sugars it can use for energy. It does this by releasing the enzymes alpha-amylase and beta-amylase.

In this lab, you will investigate this enzyme action, by first testing a dry bean seed for the presence of glucose, then testing a been seed that has germinated.

Pepsin and Trypsin

During digestion, food is broken down in stages by a series of chemical reactions. These chemical reactions are catalyzed by digestive enzymes. A protease is an enzyme that breaks down proteins. Two proteases pepsin and trypsin, are secreted at different stages and at different sites during digestion. Each digestive enzyme works best at an optimum pH. The stomach has a pH of about 2, while the small intestine has a pH of between 7 and 8.

In this lab, you will determine, through observation, which protease is secreted into the stomach, and which is secreted into the small intestine.

In this lab, you will demonstrate the production of the enzyme invertase (sucrase) by yeast. The enzyme invertase catalyzes the hydrolysis of the disaccharide sucrose to invert sugar. Invert sugar is a mixture of glucose and fructose, which are both monosaccharides. Yeast cannot directly metabolize (ferment) sucrose. For the yeast to utilize sucrose as an energy source, it must first convert it to the fermentable monosaccharides glucose and fructose.

Benedict's solution is a test reagent that reacts positively with simple reducing sugars. All monosaccharides and most disaccharides are reducing sugars, possessing a free carbonyl group (=C=O). Sucrose is an exception in that it is not a reducing sugar. A positive Benedict's test is observed as the formation of a brownish-red cuprous oxide precipitate. Both glucose and fructose test positive with benedict's solution, sucrose does not.

TESTING FOOD FOR NUTRIENTS

In this experiment you will evaluate the nutrient content of unidentified food samples. You will use chemical reagents to test the unknown for specific nutrients.

Nutrients such as carbohydrates (sugars and starch) and proteins can be detected by the use of an indicator, which is a chemical that produces a characteristic color when a particular substance is present. Lipids can be detected by their ability to make paper translucent. In this lab, you will test foods for various nutrients, and compare your tests to standards, which are the results of tests that show a positive response for a known substance.

By burning pieces of food, the chemical energy stored in molecular bonds is released as heat and light. The heat can be measured in units called calories.

EFFECT OF A HORMONE ON PLANT ROOT GROWTH

AUXIN [indole-3-acetic acid (IAA)]

The auxin, indole-3-acetic acid (IAA), is produced in the new leaves of a plant and then transported to the stem. The IAA initiates the formation of adventitious roots, which are roots that grow from a stem.
in this lab, you will be comparing the effects of different concentrations of an auxin on root growth, and the effectiveness of two methods of application. This lab will take approximately 10 days, not including the time needed to grow the bean seedlings.

CHLOROPHYLL FLUORESCENCE

When a pigment absorbs light, electrons of certain atoms in the pigment molecules are boosted to a higher energy level. The energy of an absorbed photon is converted to the potential energy of the electron that has been raised to an excited state. In most pigments, the excited electron drops back to its ground-state, or normal orbit, and releases the excess energy as heat. Some pigments, including chlorophyll, emit light as well as heat after absorbing photons.

In the chloroplast, these excited electrons jump from the chlorophyll molecule to a protein molecule in the thylakoid membrane, and are replaced by electrons from the splitting of water. The energy thus transferred, is used in carbohydrate production.

This release of light is called fluorescence. Chlorophyll will fluoresce in the red part of the spectrum, and also give off heat. In this lab, you will observe this fluorescence by seperating the chlorophyll from the thylakoid membrane.

The mix of pigments in a leaf may be separated into bands of color by the technique of paper chromatography.

In this experiment you will measure the effect of light intensity on the rate of photosynthesis. You will expose Elodea samples to various light intensities, and determine the relative rates of photosynthesis by observing changes in pH.

OBSERVING WATER TRANSPORT IN A CELERY STALK

As water evaporates from the leaves of a plant, more water is drawn up by osmosis from the tissues below to replace it. The replacement of water lost through transpiration is possible because water molecules have polar covalent bonds. This causes one end of the molecule to have a slightly positive charge and the other end to have a negative charge. Because of this, the water molecules act like "small magnets". The positive end of one water molecule sticks to the negative end of another in a long chain that is pulled upward against the force of gravity.

When enclosed in a narrow tube, such as the transport vessels of a plant, water molecules can withstand a large force without being pulled apart.

MEASURING PLANT TRANSPIRATION

Most plants loose 90% of the water taken into the roots as a result of the process of transpiration. Transpiration is the movement of water molecules from the plant into the air. Most water loss is through the stomata when they are open for photosynthesis. Environmental conditions can cause changes in the opening and closing of the stomata. Some environmental conditions will increase the rate of transpiration, while others will slow it down.
You will investigate four environmental conditions.

CARBON DIOXIDE PRODUCTION BY GERMINATING SEEDS

Living things need energy to carry on most of their processes. The cells of germinating seeds oxidize carbohydrates, in the process known as cellular respiration, to provide energy for growth. In this process, carbon dioxide is released as a byproduct. The balanced equation for cellular respiration (oxidation of glucose) is as follows:

C₆H₁₂O₆ + 6 H₂O + 6 O₂ ---> energy + 6 CO₂ + 12 H₂O

The increasing concentration of carbon dioxide, in a closed environment, can be observed using a pH indicator solution. As carbon dioxide dissolves in water, it produces carbonic acid. As the carbonic acid concentration increases, the pH lowers.

In this lab, you will observe the formation of carbon dioxide by germinating seeds using bromthymol blue solution as the indicator. As more carbon dioxide is absorbed, and the pH lowers, bromthymol blue turns from blue to green to yellow.

ENERGY RELEASE AND CELLULAR METABOLISM

Living things need energy to carry on most of their processes. The cells of germinating seeds oxidize carbohydrates, in the process known as cellular respiration, to provide energy for growth. The balanced equation for cellular respiration (oxidation of glucose) is as follows:

C₆H₁₂O₆ + 6 H₂O + 6 O₂ ---> energy + 6 CO₂ + 12 H₂O

In this lab, you will observe the release of heat energy and the formation of carbon dioxide by germinating seeds.

OBSERVING GROWTH RATE IN A CULTURE OF DUCKWEED

In this lab you will prepare a culture of duckweed, observe the growth, and graph the data. Duckweed is a small common aquatic floating plant with leaf like lobes, and roots extending down into the water. Each lobe is actually considered a separate plant.
The growth of the plants occurs by mitosis and can be quantified by counting the number of new buds found on the plant after a period of time. A population of plants establishing itself in a new area will exhibit the S-shaped curve that we see so many times in science.

OBSERVING THE EFFECT OF pH ON THE GROWTH OF DUCKWEED

In this lab you will prepare six cultures of duckweed each at a specific pH, observe the growth, and graph the data. Both biotic and abiotic factors influence the growth of individuals and populations. The pH of an aquatic environment is an abiotic factor which can dramatically influence the growth of plants. You will be able to determine the optimal pH for the growth of duckweed.
Duckweed is a small common aquatic floating plant with leaf like lobes, and roots extending down into the water. Each lobe is actually considered a separate plant.
The growth of the plants occurs by mitosis and can be quantified by counting the number of new buds found on the plant after a period of time. A population of plants establishing itself in a new area will exhibit the S-shaped curve that we see so many times in science.

GENETICS LABS

EXTRACTING DNA

From an onion

In this lab, we will be using the chemical properties of DNA, and its attraction to something polar, to extract it from the cells of onions.

A cross between individuals that involves one pair of contrasting traits is called a monohybrid cross. First we will use Punnett square diagrams to predict the results of various monohybrid crosses. We will then examine ears of corn Purple results from the dominant allele (P), and yellow from the recessive allele (p). We will be making observations and assumptions for both the genotype or genetic make-up, and the phenotype or external appearance.

A dihybrid cross is a cross between individuals that involves two pairs of contrasting traits. Predicting the results of a dihybrid cross is more complicated than predicting the results of a monohybrid cross. All possible combinations of the four alleles from each parent must be considered.

We will examine a dihybrid cross involving both color and texture. Purple (P), is dominate to yellow (p), and smooth texture (S) is dominant to wrinkled (s). Both parent plants are heterozygous for both traits.

OTHER LABS

MODELING THE SURFACE AREA TO VOLUME RATIO OF A CELL

Cells are limited in how large they can be. This is because the surface area and volume ratio does not stay the same as their size increases. Because of this, it is harder for a large cell to pass materials in and out of the membrane, and to move materials through the cell.
In this lab, you will make cube shaped models to represent cells. The dimension along one side will be doubled with each model. You will then calculate the surface area, volume, and the ratio between the two.

In this lab, you will look at epithelial cells in both plants and animals. Epithelial cells form the skin of the body surfaces and the linings of the inner surfaces. These cells are specialized for transportation of substances and protection. The individual cells of these layers may be shaped like cubes, columns, or be flat, depending on their location and function.

In this lab you will be observing plant cells (onion) in the various stages of mitosis, and make time calculations based on the data you collect.

In this lab, you will create conditions in which cabbage will become fermented, in the presence of certain bacteria, and will turn into sauerkraut.

The selectively permeable membrane you will use to study osmosis is the membrane within an eggshell. It allows water to pass through in response to concentrations of the solutions on either side of the membrane.

Brine shrimp are small arthropods which live in tidal pools, estuaries, and salt lakes. The salt concentration of these environments can vary greatly. In this experiment, you will hatch brine shrimp eggs in different salt concentration solutions to find the optimal salt concentration for brine shrimp eggs to hatch. This lab will take 5 days to complete (not including the solution preparation).
The unit of concentration you will be using is parts per thousand (ppt). In a solution, this is the number of volume units of solute (sea salt) per 1000 volume units of solvent (water).

A spirometer is the instrument used in the health profession to accurately measure lung capacity. Lung capacity provides information about the general health of the lungs.
In this lab, you will measure three indices of lung capacity using a balloon. Vital capacity is the maximum amount of air that is held in the lungs. The expiratory reserve is the amount of air that remains in the lungs after a normal exhalation. The tidal volume is the amount of air exchanged during a normal breath. While not as accurate as a spirometer, the balloon measurements do provide a good indication of your lung capacity.

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