Biol 211 Lab Exam

Null Hypothesis (H0)

The assumption that an experimental treatment has no effect, or that no significant difference exists between groups.

hypotheses can never be "proven"

Future experiments, newer technologies, or alternative interpretations can always potentially reject them down the road.

Graphs of Dependent variables

vertical y-axis.

Graphs of Independent Variables

horizontal x-axis

Why do we keep Experimental constants

Prevents unrelated variables from changing the dependent variable, ensures changes are due to the independent variable.

Purpose of an experimental control treatment

Confirms that the baseline experimental environment does not influence the dependent variable.

Impact of sample size (n) on standard error

Larger sample sizes and more replicates reduce experimental error, smaller SEM and a more accurate sample mean.

Standard Error of the Mean (SEM) bars overlap

The treatment means are considered likely similar

Standard Error of the Mean (SEM) bars do not overlap

The treatment means are likely different.

Criteria for choosing a line graph

Used when the independent variable on the x-axis is numerical and continuous (has infinite values between whole numbers).

Criteria for choosing a bar graph

Used when the independent variable on the x-axis is non-numerical or discontinuous/discrete.

Proper orientation and placement of a Table caption

Plotted directly ABOVE the table, numbered consecutively and separately from figures.

Figure caption

Plotted directly UNDERNEATH the graph, containing enough detail to make the figure completely self-explanatory.

Second stop of a micropipette

pressed during dispensing to remove any remaining fluid from the tip

First stop of micropipette

pressed before immersion to draw up the exact target volume.

method for carrying microscope

Grasp the arm firmly with one hand while supporting the base with the other hand.

cleaning microscope lenses

lens cleaner and specialized lens paper

iris diaphragm

Regulates the amount of light entering the condenser lens system.

Mechanism by which enzymes accelerate biochemical reactions

By binding substrates at the active site to lower the required activation energy of the reaction.

Units assigned to spectrophotometer absorbance values

None; absorbance is a unitless value.

absorbance

chemical measurement of light captured by a solution.

absorbency

the physical capacity of a material to soak up liquid.

Purpose and axis layout of a standard curve

Maps known pigment concentrations (x-axis) against measured absorbances (y-axis) to convert unknown absorbance values into concentrations.

Natural substrate and monomer products of beta-galactosidase

Substrate: Lactose (disaccharide). Products: Glucose and Galactose (monosaccharides).

Artificial substrate in enzyme lab

ONPG, needed because natural lactose and its products are colorless and cannot be tracked by a spectrophotometer.

color of ONPG cleavage by beta-galactosidase

Pale-yellow o-nitrophenyl (alongside colorless galactose).

role of adding 1.0 M Sodium Carbonate

stops the enzyme reaction. Converts pale-yellow o-nitrophenyl into dark-yellow o-nitrophenolate for better absorbance readings.

Dilution (D) formula

D = (Volume of Original Solution) / (Volume of Original Solution + Volume of Diluent).

Concentration of a diluted sample (Cd) formula

Cd = Cu * D (where Cu is undiluted concentration and D is dilution).

Fixed-volume stock solution dilution formula

V1C1 = V2C2

economic and environmental flaws of corn-derived ethanol

Low yield per hectare, heavy fertilizer pollution causing eutrophication, microbial N2O greenhouse emissions, and increased global food prices.

ecological caveat of sugarcane biofuel production

Rainforest land clearing destroys pristine habitats and releases massive stored carbon during biomass decay/burning.

biological purpose of fermentation for yeast cells

Regenerates/oxidizes NADH back to NAD+ to ensure the energy-yielding reactions of glycolysis can continue moving forward.

anaerobic ethanol fermentation

Glucose undergoes glycolysis to form Pyruvate, which is decarboxylated into Acetaldehyde (CO2 is released), then reduced into Ethanol.

The visible gas byproduct of yeast fermentation and its experimental use

Carbon dioxide (CO2), used in the lab as a direct estimate to measure the rate/volume of biofuel production.

Why raw fermentation products must undergo downstream distillation

Ethanol becomes highly toxic to yeast at concentrations near 18%, requiring distillation to clear water and produce pure fuel.

step before yeast can metabolize complex starches or cellulose

The complex/structural plant carbohydrates must first be broken down into simple component sugars like glucose.

bacterial transformation

The process of bacterial cells taking up foreign DNA from their surroundings

Role and expression profile of the ampR plasmid gene

Encodes beta-lactamase to destroy ampicillin, expressed constitutively to allow selection of successfully transformed bacteria.

pGLO behavior in the absence of arabinose sugar (Repression)

AraC protein binds to the operator, physically blocking RNA polymerase from transcribing the GFP gene.

pGLO behavior in the presence of arabinose sugar (Activation)

Arabinose binds AraC, changing its shape so RNA polymerase can bind the promoter and transcribe GFP, making cells glow green under black light.

Ori (Origin of Replication) sequence

Essential for allowing the plasmid DNA to replicate itself inside the host cell before division.

How UV radiation damages DNA at the molecular level

Ionizes water molecules into free radicals, which react with nitrogenous bases to alter their chemical structure and ruin accurate replication base-pairing.

yeast cells make effective model organisms for human cellular study

They are rapidly growing unicellular eukaryotes that share complex, highly conserved molecular and DNA repair processes with human cells.

Positive controls in UV/Sunscreen lab

Aluminum foil (blocks all UV)

Negative controls in UV/Sunscreen lab

Clear plastic wrap (allows all UV through).

location of the Light-Dependent reactions

The thylakoid membrane inside the chloroplast.

location of the Calvin Cycle

The chloroplast stroma.

outputs of the Light-Dependent reactions

Oxygen gas (O2), ATP, NADPH.

inputs of the Light-Dependent reactions

Light energy, water, ADP, NADP+

inputs of the Calvin Cycle

Carbon dioxide (CO2), ATP, NADPH.

outputs of the Calvin Cycle

Carbohydrates (glucose), ADP, NADP+.

Energy shuttles linking light reactions to dark reactions

ATP and NADPH transfer captured light energy out of the thylakoids and into the stroma to power carbon fixation.

The status of direct text quotations in scientific reporting

Prohibited; all external background literature claims must be paraphrased into your own words.

CSE Reference structure for Journal Article

Author(s). Year. Title. Journal. Volume(issue): pages.

CSE Reference structure for a Textbook

Author(s). Year. Title. Edition. Publisher. Pages.

carbon source that produced the most ethanol biofuel

Sugarcane because its high percentage of simple carbohydrates/sugars that are easily fermented by yeast

carbon source that produced the least ethanol biofuel

Barley, complex plant parts containing a high proportion of starch and cellulose which yeast cannot ferment without previous breakdown.

result of pGLO bacterial transformation plates

Only transformed bacteria containing the ampR gene grew on the ampicillin media plates, and they only fluoresced green under UV black light if arabinose sugar was present to activate the promoter.

The independent variables in the enzyme experiment

The range of pH levels tested

dependent variables of enzyme experiment

The concentration of pigmented product formed.

rule about data interpretation in the Written Results section

You must only describe the key trends and summarize what the data show. you CAN NOT interpret or discuss the biological causes.

when talking to a lab partner about results to avoid plagiarism

Discuss the general ideas and trends together, but write every word of your individual report entirely in your own words.

caption of a summarized data figure must state about error bars

It must explicitly state what the bars indicate, such as standard error of the mean (SEM).

microscope lens system that gathers and focuses light onto the specimen

The condenser lens beneath the mechanical stage

used to adjust the physical height of the condenser lens

The condenser focus knob located below the stage.

component of a spectrophotometer that converts transmitted light energy into an electric current

The photocell which then sends the signal to the digital readout

purpose of using aseptic technique when plating yeast

To prevent contamination of the growth media plates and the yeast cultures by unwanted environmental microbes.

mutation

A permanent change to the genetic information (DNA sequence) of a cell.

radicals cause a mutation during replication

alter the chemical structure of nitrogenous bases, which ruins their ability to form correct base pairs when the strand is used as a template.

effect of a DNA sequence mutation on traits

It changes the mRNA sequence transcribed, which changes the amino acid sequence of the translated protein, altering its structure and function.

The mathematical formula for calculating the Standard Error of the Mean (SEM)

SEM = sqrt( sum( (mean - x)^2 ) / ( n * (n - 1) ) )

microbiota

physical community of microorganisms themselves

microbiome

collective microorganisms plus all of their genes and genetic material.

abundant thing in human GI tract

Bacteria

microbial density in stomach

Low numbers in the highly acidic enviroment

microbial density in small intestine

moderate numbers

microbial density in large intestine

highest concentration/density

developmental periods of the human gut microbiota

Starts at birth in newborns (most critical development phase), stabilizes during childhood (ages 2 to 10), and becomes highly stable and diverse in adulthood.

environmental factors of early life microbiota colonization

Method of childbirth (vaginal vs. C-section), early diet, geographical environment, and exposure to antibiotics.

The definition and biological indicators of Gut Dysbiosis

An unhealthy microbial imbalance in the gut caused by poor diet, antibiotic usage, infections, or genetics. results in a compromised mucus layer, intestinal inflammation, and irregular immune function.

physiological mechanism of Colonization Resistance in a healthy gut

Beneficial microbes physically take up space and consume nutrients, blocking potential pathogenic bacteria from establishing themselves.

The definition and clinical purpose of Fecal Microbiota Transplantation (FMT)

Shifting a healthy donor's fecal microbes into a patient's GI tract to restore a balanced microbial community.

Synbiotics

Formulated mixtures of prebiotics and probiotics.

Postbiotics

Dead microbes

Probiotic

Live beneficial microbes.

Prebiotic

Dietary fibers that boost beneficial microbe activity.

The basic physical definition and category types of microplastics

Microscopic plastic polymers under 5mm in size, categorised as fragments, fibers, or microbeads.

Secondary microplastics

Fragments resulting from the breakdown of larger plastics.

Primary microplastics

Intentionally manufactured to be small

chemical mechanisms of environmental plastic degradation

1. UV Photodegradation (solar radiation breaks polymer chains). 2. Mechanical Abrasion (physical forces). 3. Thermal Degradation (heat breakdown).

The surface area to volume (SA:V) chemical hazard of microplastics

Their small size high surface area to volume ratio, allowing them to act as a 'chemical sponge' that concentrates toxins like oil and DDT/PCBs.

Primary exposure pathways for microplastics entering human systems

Inhalation of airborne synthetic microfibers, dietary ingestion of contaminated food/water, and accidental ingestion of indoor dust.

Observed cellular and biological pathologies caused by microplastic toxicity

Immune cells react to them as foreign objects, causing oxidative stress inside cells, DNA damage, lipid damage, protein damage, and impaired energy metabolism.

health risks with high microplastic exposure

Chronic tissue inflammation, elevated risk of asthma, IBS, hypertension, and neurodegenerative conditions like Alzheimer's and Parkinson's.

role of prokaryotes in chocolate production

drive the multi-stage fermentation of raw, bitter cocoa beans to yield essential flavor compounds and alter bean color from white/purple to brown.

The continuous chain of microbial succession during cocoa bean fermentation

1. Anaerobic Phase (yeasts convert sugars to ethanol/CO2). 2. Lactic Acid Phase (LAB produces lactic acid/butter flavors). 3. Acetic Acid Phase (AAB converts ethanol to acetic acid).

The primary physical and chemical effect of the Acetic Acid Bacteria (AAB) phase

The heat produced and the acid penetration kill the cocoa bean embryo, which is necessary for flavor development.

The chemical consequences of over-fermenting cocoa beans

The pH rises too high, inducing aerobic spoilage and producing off-flavors described as hammy or putrid.

The biological mechanism of flavor development inside the cocoa bean

Microbial enzymes break down storage proteins into hydrophilic amino acids and peptides, which interact with sugars to form chocolate flavor profiles during roasting.