Biology 1110 Laboratory Practical One
How and why do plant cells respond differently than animal cells to hypotonic solutions?
The plant cell has a rigid cell wall which does not allow the cell to swell to the point of bursting.
Know the overall formula for photosynthesis.
6CO2 + 6H2O + light energy = C6H12O6 + 6O2.
What is an enzyme? substrate? active site? product?
A substance that speeds up a chemical reaction, but is not consumed by that reaction, is called a catalyst. The biological molecules that catalyze reactions in living organisms and cells are more specifically called enzymes. To catalyze a reaction, an enzyme will bind to one or more reactant molecules, known as its substrates. In some reactions, a single substrate is broken down into multiple products. The part of the enzyme where the substrate binds is called the active site (since that's where the catalytic "action" happens). Usually, the active site will be a pocket or cleft in the enzyme's surface, and it's often just a small part of the overall molecule.
What is meant by parfocal?
A. Parfocal means that the microscope is binocular. B. Parfocal means that when one objective lens is in focus, then the other objectives will also be in focus. C. Parfocal means that the microscope is self-cleaning and needs no maintenance.
What are the monomers for proteins?
For proteins, the monomers are amino acids.
Know differences in prokaryotic and eukaryotic cells.
Eukaryotic cells contain membrane-bound organelles, including a nucleus. Eukaryotes can be single-celled or multi-celled, such as you, me, plants, fungi, and insects. Bacteria are an example of prokaryotes. Prokaryotic cells do not contain a nucleus or any other membrane-bound organelle.
How do you prepare a wet mount of cheek cells?
Obtain a toothpick from the supply table. After gently scraping the inside of you cheek, gently scrape them onto the center of a clean glass slide. Place one drop of Methylene Blue (another type of stain) on top of the cheek cells. Hold a clean coverslip by the edges in your fingers, apply.
How are Rf values calculated?
R(f) = Distance pigment moved / distance from origin
What determines the shape of an enzyme or other protein? How can heat alter the shape? How can pH changes alter shape? Why?
The function of a protein is determined by its shape. The shape of a protein is determined by its primary structure (sequence of amino acids). The sequence of amino acids in a protein is determined by the sequence of nucleotides in the gene (DNA) encoding it.
How are monomers or subunits of organic compounds linked together to create polymers?
The monomers in all four of these groups are combined to make larger molecules in a reaction called condensation. This is where two molecules join to make a larger molecule and a small molecule. The small molecule in this case is water and so it's also called a "dehydration" reaction. The reverse of this reaction, where you break these molecules into smaller pieces combines water back into them and is called "hydrolysis".
Be able to describe the plasma membrane and types of transport proteins found in the membrane.
The plasma membrane is composed of a phospholipid bilayer, which is two layers of phospholipids back-to-back. There are two major classes of membrane transport proteins: carrier proteins and channel proteins. Carrier proteins (also called carriers, permeases, or transporters) bind the specific solute to be transported and undergo a series of conformational changes in order to transfer the bound solute across the membrane. Channel proteins, on the other hand, need not bind the solute. Instead, they form hydrophilic pores that extend across the lipid bilayer; when these pores are open, they allow specific solutes (usually inorganic ions of appropriate size and charge) to pass through them and thereby cross the membrane.
Photosynthesizing and non-photosynthesizing plants were monitored for carbon dioxide accumulation. In which leaf did carbon dioxide accumulate and why? Why did we set up tubes without leaves in this experiment?
Tubes without leaves were the controls; the carbon dioxide accumulated in the tube with a leaf and foil.
Be able to identify red blood cells in hypertonic and isotonic solutions.
When a red blood cell is placed in a hypertonic solution, it shrinks as water is drawn out of the cell and into the surrounding solution. If the same blood cell is placed in a hypotonic solution, the blood cell grows in size. Blood cells in isotonic solutions do not shrink or swell.
What are "polar" versus "nonpolar" compounds?
When you have a polar molecule, your bonds will not cancel out. This means that in a polar bond, the electronegativity of the atoms will be different. For nonpolar bonds the electronegativity of the atoms will be equal. In a polar bond you will have an unequal sharing of electron pairs which causes a molecular dipole.
Be able to identify elodea cells in hypertonic and hypotonic solutions.
In a hypertonic medium it will shrink due to outward osmosis and partial dehydration. The cell membrane will separate from the cell wall (called plasmolysis). The cell will die. In a hypotonic environment, the cell will be in dynamic equilibrium. It will be a healthy, happy cell. In a hypotonic situation, there will be a net gain of water into the cell by inward osmosis. The cell will bulge , but NOT BURST, due to a rigid cell wall.
Explain how chromatography separates plant pigments.
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 a source of food, the yeasts were provided with either glucose, starch with amylase, starch alone, or distilled water. What served as the control? Which food seemed to be digested most quickly by the yeast? Which was digested most slowly? Why?
Yeast + water served as the control; glucose was digested most quickly; starch alone was digested most slowly because starch is not easy to digest (it's a polysaccharide.) and amylase helped break down a little of it so the yeast could digest it.
What is spectrophotometry?
Spectrophotometry is a method to measure how much a chemical substance absorbs light by measuring the intensity of light as a beam of light passes through sample solution. The basic principle is that each compound absorbs or transmits light over a certain range of wavelength.
What is meant by "depth of focus"?
The focal depth refers to the depth of the specimen layer which is in sharp focus at the same time, even if the distance between the objective lens and the specimen plane is changed when observing and shooting the specimen plane by microscope.
We used dialysis tubing to represent a cell membrane. Be able to describe which substances could cross the membrane and which could not and how we know. The glucose, water and iodine were all able to cross the membrane. Starch was not. How did you know?
The water in the larger beaker did not react to the Lugol's reagent; which meant that starch was not able to escape the "cell membrane".
Be able to calculate the total magnification of a scope with any objective.
To get the total magnification take the power of the objective (4X, 10X, 40x) and multiply by the power of the eyepiece, usually 10X.
What is meant by "compound light microscope"?
A compound microscope is a microscope which uses a lens close to the object being viewed to collect light (called the objective lens) which focuses a real image of the object inside the microscope.
Be able to define the following terms: solute, solvent, diffusion, osmosis, isotonic, hypertonic, hypotonic
A typical example of a solution is sugar dissolved in water: sugar is the solute and water is the solvent. diffusion: the movement of a substance from an area of high concentration to an area of lower concentration until an equilibrium is reached. hypertonic: concerning osmosis, a term used to compare one solution with another, a hypertonic solution has a higher concentration of solutes, when separated by a membrane that is permeable to the solvent and impermeable to the solute. In this instance the solvent will flow from the region of lower solute concentration (hypotonic) to the region of higher concentration (hypertonic) by the process of osmosis. e.g. most fresh water protists are hypertonic when compared with their environment. hypotonic: (see hypertonic for a detailed description) a solution that has a lower concentration of solutes than a hypertonic one. isotonic: (see hypertonic or hypotonic) when two solutions separated by a membrane permeable to the solvent but not the solutes are of equal concentration this results in no net movement of solvent across the membrane. osmosis: the phenomenon whereby water flows across a selectively permeable membrane from a hypotonic environment to a hypertonic environment.
Be able to recognize and identify differences in plant and animal cells.
Beyond size, the main structural differences between plant and animal cells lie in a few additional structures found in plant cells. These structures include: chloroplasts, the cell wall, and vacuoles.
Know the overall formula for Cellular Respiration. What is used? What is produced? How many molecules of ATP are generated in aerobic respiration and fermentation?
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (as ATP) USED is Glucose and oxygen, what is produced? Carbon Dioxide Water and 36 or 38 ATPs in Aerobic and only two ATPs in the anerobic process
Be able to describe the fermentation tube that was used to measure fermentation in yeast. What gas was accumulating in the top of the fermentation tube?
CO2.
For our lab experiments, what served as the enzyme? What was the substrate? What was the product?
Catalase was the enzyme used, the substrate was Hydrogen Peroxide, and the product was water and oxygen.
What are the monomers for carbohydrates?
Certain carbohydrates called polysaccharides are made up of monomers called Monosaccharides.
How did temperature affect catalase activity? How did pH affect catalase activity? What does it mean to denature an enzyme?
Change the pH and the enzyme stops working. Increasing the temperature to 60°C will cause a permanent change to the shape of the active site. This is why enzymes stop working when they are heated. We say they have become denatured.
What is chromatography?
Chromatography is a versatile separation technique widely used to obtain pure compounds from mixtures
To determine whether or not carbon dioxide was being released and accumulating, a pH indicator (bromothymol blue) was used. How/why does this pH indicator show an accumulation of carbon dioxide?
Color change to yellow
Know the parts and the function of the parts of the compound light microscope.
Eyepiece: The lens the viewer looks through to see the specimen. The eyepiece usually contains a 10X or 15X power lens. Diopter Adjustment: Useful as a means to change focus on one eyepiece so as to correct for any difference in vision between your two eyes. Body tube (Head): The body tube connects the eyepiece to the objective lenses. Arm: The arm connects the body tube to the base of the microscope. Coarse adjustment: Brings the specimen into general focus. Fine adjustment: Fine tunes the focus and increases the detail of the specimen. Nosepiece: A rotating turret that houses the objective lenses. The viewer spins the nosepiece to select different objective lenses. Objective lenses: One of the most important parts of a compound microscope, as they are the lenses closest to the specimen. A standard microscope has three, four, or five objective lenses that range in power from 4X to 100X. When focusing the microscope, be careful that the objective lens doesn't touch the slide, as it could break the slide and destroy the specimen. Specimen or slide: The specimen is the object being examined. Most specimens are mounted on slides, flat rectangles of thin glass. The specimen is placed on the glass and a cover slip is placed over the specimen. This allows the slide to be easily inserted or removed from the microscope. It also allows the specimen to be labeled, transported, and stored without damage. Stage: The flat platform where the slide is placed. Stage clips: Metal clips that hold the slide in place. Stage height adjustment (Stage Control): These knobs move the stage left and right or up and down. Aperture: The hole in the middle of the stage that allows light from the illuminator to reach the specimen. On/off switch: This switch on the base of the microscope turns the illuminator off and on. Illumination: The light source for a microscope. Older microscopes used mirrors to reflect light from an external source up through the bottom of the stage; however, most microscopes now use a low-voltage bulb. Iris diaphragm: Adjusts the amount of light that reaches the specimen. Condenser: Gathers and focuses light from the illuminator onto the specimen being viewed. Base: The base supports the microscope and it's where illuminator is located.
Yeast use fermentation to generate ATP. What is fermentation?
Fermentation is a metabolic process that converts sugar to acids, gases, or alcohol. It occurs in yeast and bacteria, and also in oxygen-starved muscle cells, as in the case of lactic acid fermentation.
What is meant by the visible light spectrum?
Generally, visible light is defined as the wavelengths that are visible to most human eyes.
What is meant by "inversion" related to microscope use?
Inversion is the reversal of an image projected by a microscope. Most microscopes used today are compound microscopes, meaning they have more that one lens involved in the magnification process.
Be able to give examples and characteristics of carbohydrates, lipids and proteins.
Lipids are a broad group of naturally occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The main biological functions of lipids include energy storage, as structural components of cell membranes, and as important signaling molecules. Proteins (also known as polypeptides) are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. Carbohydrates are generally divided into 3 saccharides: Monosaccharides , Disaccharides, and Polysaccharides. They consist ONLY of CARBON, HYDROGEN, and OXYGEN.
Does low power or high power have a larger field of view? How did we calculate the field of view of our scopes?
Low power has a larger field of view. 1) Look at your microscope eyepiece. After the eyepiece magnification you will see a F.O.V, number. (Example: 10x/22 The 22 is your Field Number) 2) Use the following formula to obtain the total diameter: Formula = Field Number Divided by Objective Magnification 3) Multiply your Answer by 1000 to convert to Microns (or move the decimal 3 spaces to the right.)
Know the basic premise of the 4 tests performed for organic compounds, and be able to identify a positive reaction and a negative reaction for each.
Lugol's iodine reagent (IKI) is useful to distinguish starch and glycogen from other polysaccharides. Lugol's iodine yields a blue-black color in the presence of starch. Glycogen reacts with Lugol's reagent to give a brown-blue color. Benedict's reagent contains blue copper (II) sulfate (CuSO4) which is reduced to red copper (I) oxide (Cu2O). The copper oxide is insoluble in water and precipitates out of solution. The color of the final solution may appear green to brick red depending on how many of the copper (II) ions are present. Sudan IV (C24H20N4O) is a red, fat-soluble dye used for staining lipids, triglycerides and lipoproteins. Biuret reagent, made of sodium hydroxide and copper (II) sulfate, is used for determining the presence of protein in a sample. The test relies on the reaction between copper ions and peptide bonds in an alkaline solution. A violet color indicates the presence of proteins. Proteins give a strong Biuret reaction because they contain a large number of peptide bonds.
Why is enzyme shape important to enzyme function?
Most enzymes are proteins and therefore their function is specific to their structure.
