Bio 1001 Lab Final

What are three differences between a compound microscope and a stereoscope?

1) A stereoscope provides a 3D image, while a compound microscope provides a 2D image

2) A stereoscope does not have an inverted image, while a compound microscope does

3) A stereoscope has a larger working distance than a compound microscope

When should you use a stereoscope? A compound microscope?

Stereoscope- Dissecting. Range = 8x-40x

Compound microscope- Slides. Range= 40x-100x

What is the formula for total magnification?

Total magnification = (Magnification of objective lens) x (Magnification of ocular lens)

What is depth of field?

The thickness of the layer that is in focus simultaneously.

What happens to the depth of field as you move from lower to higher magnification?

The depth of field decreases.

What is resolving power?

The ability of a microscope to separate small points of a specimen in a sample. It is the clarity of an image in a microscope.

What does the iris diaphragm do?

It allows us to control the size of the column of light. If there is too much light, the image will have low contrast. If there is not enough light, there will be contrast, but the image will be too dark to see properly.

Why is centering the object being viewed important before moving to higher magnification?

If it is not centered, going to a higher magnification will cause the image to be out of the field of view, as increased magnification causes the size of the field of view to decrease.

For which of the lenses on the compound light microscope should you not use the coarse focus adjustment knob? Why?

The high objective lens and the oil immersion lens, because it could cause the slide to hit the lens and damage it.

What is the formula to determine cell size?

Specimen length/width = (Calibrated value of 1 o.d.) X (Specimen’s length in ocular divisions)

What is one use of the stereoscope?

Dissecting specimens. Large working space and 3D image help make it easier.

How do electron microscopes work?

They use a beam of electrons, bent and focused by electromagnetic lenses to form an image. They have very high resolving abilities.

How do the images in the SEM (Scanning electron microscope) and the TEM (Transmission electron microscope) vary from each other? What are useful applications for both?

The SEM shows a 3D image of the surface of a specimen - good for seeing tissue/organisms

The TEM shows a 2D image of the internal structures of a specimen - good for viewing organelles/viruses.

What is passive transport?

The movement of materials without the expenditure of cellular energy across cell membranes.

What conditions must be met for diffusion to occur?

Concentration gradient- areas of different concentrations side by side

Permeable membrane - membrane in which a solute can pass through

What is diffusion?

The movement of a solute particle from an area of higher concentration of that solute to an area of lower concentration of that solute.

Describe the test used to determine presence/absence of starch

Iodine is added. A light tan colour is negative. A blue/black/purple colour is positive.

Describe the test used to determine presence/absence of sugars

Benedict’s reagent is added. A blue colour is negative. A green, yellow, red or brown colour is positive.

Describe the test used to determine presence/absence of chloride ion

Silver nitrate (AgNO3) is added. Clear is negative. A white precipitate is positive.

What molecules were able to diffuse through the dialysis tubing? What ones weren't?

Chlorine and glucose were able to diffuse through the dialysis tubing, because their molecules are relatively small. Starch was not, because it is a large molecule.

What is osmosis?

The movement of a solvent, usually water, across a selectively permeable membrane, from a hypotonic solution to a hypertonic solution.

What is the tonicity of a cell?

The total solute concentration of a cell with respect to an external solution using the terms hypotonic, isotonic or hypertonic.

What NaCl solution is isotonic to potato cells? How do you know?

0.9% NaCl. This is clear, because there was very little weight change in the potato in the 0.9% NaCl solution. The initial water concentrations of the potato and the solution were nearly equal, so there was no need for water to be exchanged between them.

While observing percent weight change in potatoes, how can you tell osmosis occurred?

It is shown through the weight change of the potato. The potato gained or lost weight as water entered or left its cells.

What is the formula for percent weight change?

% weight change = (Final weight - Initial weight)/(Initial weight) x 100%

How does surface area affect diffusion?

The greater the outer surface (surface area) of a cell, the greater the number of molecules that can diffuse into the cell.

What kind of cell might need a higher surface area-to-volume ratio? Why?

Intestinal cells, because they exchange a lot of material with their surroundings. Their microvilli increase surface area without a larger increase in volume.

What happens during photosynthesis?

Light energy is trapped in photosynthetic pigments and used to split H2O into hydrogen and oxygen. The hydrogen from the split H2O is joined to CO2 to produce a simple carbohydrate.

What is the chemical equation of photosynthesis?

6CO2 + 6H2O -> C6H12O6 + 6O2

What is the chemical equation of cellular respiration?

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

What is cellular respiration?

The process used by all living things to convert chemical energy locked up in sugars into metabolic energy for work in the cell.

What light conditions do photosynthesis and cellular respiration occur in?

Photosynthesis - in light only

Cellular respiration - in light and dark

Does photosynthesis produce or consume CO2? What about cellular respiration?

Photosynthesis - consumes CO2

Cellular respiration - produces CO2

How is the rate of photosynthesis measured?

By measuring the volume of oxygen gas produced, as oxygen gas in a by-product of photosynthesis.

How does light intensity affect the rate of photosynthesis?

As light intensity increases, rate of photosynthesis increases. In order for photosynthesis to occur, a strong light energy is needed. So, as light energy decreases, so does the rate of photosynthesis.

Describe the test used to determine addition/removal of CO2.

A bicarbonate indicator (red-brown liquid) is added. It turns yellow when CO2 is added (pH is lowered) and purple when CO2 is removed (pH is raised).

What effect does increasing CO2 have on the pH? How about decreasing CO2?

Increasing CO2 - causes some of the CO2 to react with water and form carbonic acid, therefore lowering the pH.

Decreasing CO2 - causes some carbonic acid present in the solution to break down to release CO2. The decrease of carbonic acid causes the pH to increase.

What is fermentation?

The production of ethanol and carbon dioxide by yeast under anaerobic conditions.

What is the chemical equation for fermentation?

C6H12O6 -> 2C2H5OH(ethanol)+ 2CO2

How would you determine if the yeast has carried out fermentation or aerobic cellular respiration?

Fermentation produces ethanol, so if there was ethanol present it would mean that fermentation was carried out. If there was no ethanol present, it would mean that respiration was carried out.

What effect does glucose have on the rate of fermentation?

Glucose increases the rate of fermentation, because it helps to fuel the fermentation.

Name and describe the 3 locomotory structures used by protists.

Cilia- Move by gliding and twirling quickly. Change directions without turning,

Flagella - The flagellum beats like a whip and pulls the protist forward.

Pseudopodia - Move by oozing. A bulge occurs in the outer covering, cytoplasm flows into the bulge and pulls the protist forward.

What locomotory structures are used by paramecium? Amoeba? Euglena?

Paramecium - Cilia

Amoeba - Pseudopodia

Euglena - Flagella

What is a mixotroph?

A protist that feeds using both autotrophic and heterotrophic methods, such as Euglena.

What colours of light were Euglena most and least attracted to? Why?

Euglena was most attracted to the blue and white. Euglena contains chlorophyll a, which is able to absorb light best from these wavelengths. It was least attracted to yellow and green, because chlorophyll does not absorb these wavelengths well.

What are the five atoms that make up DNA?

Carbon, hydrogen, oxygen, nitrogen and phosphorus.

What are DNA monomers called? What are they composed of?

They are called nucleotides. They are composed:

- Deoxyribose (a five carbon sugar molecule that connects to both the phosphate group and the nitrogenous base)

- Phosphate group (Contains phosphorus and oxygen and helps link one nucleotide to the next)

- Nitrogenous base (Made primarily of carbon, nitrogen, hydrogen and oxygen)

What are the four possible nitrogenous bases of DNA?

Adenine, cytosine, guanine and thymine.

What is the shape of a DNA molecule? How does it form?

A double stranded helix. It is formed by nucleotides pairing up using hydrogen bonds.

How do nucleotides normally pair up (i.e. what nucleotides pair together)?

Adenine always pairs with thymine and cytosine always pairs with guanine.

What is mitosis?

A process of cell division in eukaryotes where a single cell splits its replicated chromosomes to produce two genetically identical daughter cells.

What is meiosis?

A type of cell division that reduces the chromosome number by half, creating four genetically different haploid sex cells (sperm or eggs) from one diploid parent cell.

What is the sugar-phosphate backbone?

The structural framework of DNA and RNA, composed of alternating sugar (deoxyribose in DNA, ribose in RNA) and phosphate groups.

What is DNA extraction? What does the process typically involve?

The process of isolating DNA from cells so it can be analyzed or used in further experiments. The process typically involves breaking open cells, removing proteins and other cellular components and separating the DNA into a usable form.

Where in DNA located?

Within the nucleus. It is protected by cell membranes and proteins.

Why are strawberries well suited for DNA extraction?

Their cells are soft and easy to break open, and they contain a large amount of DNA.

What is the ploidy of strawberries?

Strawberries are octoploid.

Why is detergent added to the DNA extraction buffer when extracting strawberry DNA?

The detergent breaks open the strawberry’s cell, allowing the DNA inside to be extracted.

Why do we use isopropanol in the extraction of strawberry DNA?

Isopropanol precipitates the strawberry’s DNA

What is the central dogma of molecular biology?

It describes the flow of genetic information within a cell: DNA → RNA → Protein.

Name and briefly describe the two main steps of the central dogma.

Transcription - DNA is used to make RNA

Translation - RNA is used to build proteins

What is transcription?

The process by which a segment of DNA is used as a template to make a complementary strand of messenger RNA (mRNA).

What is the structure of RNA? How does RNA differ from DNA?

RNA is single stranded. It differs from DNA in the sugar, a ribose instead of deoxyribose, and in one of the nitrogenous bases, Uracil in place of Thymine.

Describe the process of transcription.

An enzyme called RNA polymerase binds to a specific region of the DNA called the promoter. RNA polymerase then unwinds the DNA and reads one strand, building the mRNA strand by adding RNA nucleotides that are complementary to the DNA template. As RNA polymerase moves along the DNA, it elongates the mRNA strands until it reaches a termination signal, at which point transcription ends and mRNA is released to be used in translation

What is translation?

The process by which genetic code carried by mRNA is used to build a protein.

Where does translation take place?

In the ribosome.

Describe the process of translation.

The ribosome reads the mRNA sequence in codons. Transfer RNA (tRNA) molecules bring the correct amino acids to the ribosome, matching their anticodon to the codon on the mRNA. The ribosome links the amino acids in the correct order to form a polypetide chain, which then folds into a functional protein. Translation occurs until the ribosomes reaches a stop codon, signaling the end of the protein.

What is a codon? What do they signify?

A set of three bases in mRNA. Each codon corresponds to a specific amino acid.

Where do transcription and translation occur in prokaryotes? How about in eukaryotes?

In prokaryotes, they occur in the cytoplasm, and can happen simultaneously. In eukaryotes, transcription occurs in the nucleus, where the DNA is stored. Translation occurs in the cytoplasm.

What does the cutting of the DNA sequences down the middle represent in the process of transcription?

It represents the unzipping of the DNA sequence.

What does it means when DNA strands are said to be “complementary”?

It means that two strands contain complementary nitrogenous bases. For example, if one strand has ACGT, a complementary strand would have TGCA.

How do the triplets in the mRNA dictate the final protein sequence?

The triplets are codons, and each codon corresponds to a specific amino acid. The sequence of codons determines the order of amino acids in the protein.

Name and briefly describe the two phases of the cell cycle.

Interphase- When cells grow, and also when chromosomes are duplicated

Mitotic phase- Involves two events: the division of the nucleus and the division of the cytoplasm

What are the four phases of the life cycle of a somatic cell?

G1, S, G2 and M.

What are the five stages of mitosis?

Prophase, prometaphase, metaphase, anaphase and telophase.

What are meristematic areas?

Specialized regions in plant cells that are capable of cell division.

What is the longest phase of mitosis? What is the shortest phase?

The longest phase is prophase, because complex changes are needed to prepare the chromosomes for separation. The shortest is anaphase, as sister chromatids are quickly pulled to opposite poles.

Briefly describe the 4 observable phases of mitosis.

Prophase- Chromosomes condense and the mitotic spindle forms

Metaphase- Chromosomes align at the cells equator

Anaphase- Sister chromatids are pulled apart to opposite poles

Telophase/cytokinesis- Restore the nucleus and divide the cytoplasm

How does telophase differ between plant and animal cells?

In plant cells, a cell plate forms which then turns into a cell wall, creating two new, separate cells.

In animal cells, a cleavage furrow forms and pinches inward to create two new, separate cells.

Why did we choose the tip of the garlic root for observing cells in mitosis?

The tip of the cell is a region of rapid cell division, therefore it is the site of mitosis in garlic root.

What stage of the cell cycle would you expect cells in the garlic root above the tip to be in?

Interphase, because interphase is the longest phase of the cell cycle.

What stage of mitosis is the most abundant in garlic root cells? Which stages do you not see as much? How does that relate to the length of each stage in mitosis?

Most of the cells are in prophase, because it is the longest stage. There are quite a few in metaphase as well, as that stage is moderately long. The least viewed are anaphase and telophase, because these stages are quite short.