Core Biology Cheat Sheet 1 - Lab Safety/Steps PDF

Core Biology Cheat Sheet 1 - Lab Safety / Steps Micro Pipetting: Enables accurate delivery of small volumes, Terminology:...

Core Biology Cheat Sheet 1 - Lab Safety / Steps Micro Pipetting: Enables accurate delivery of small volumes, Terminology: Select the pipette based on volume delivering, PPE: Equipment minimizing hazards (e.g., gloves, goggles, masks, lab coats). Choose the correct pipette size for the syringe, Risk Assessment: Identifying hazards, evaluating risks, minimizing dangers (e.g., PPE, ○ 1 µL = a millionth of a litre protocols). ○ 10µL - use 1-10µL (1000µL is 1mL) COSHH Forms: Documents managing hazardous substances; handling, storage, ○ 20µL - use 2-20µL (100µL is 0.1mL) disposal instructions. ○ 100µL - use 21-100µL (10µL - 0.01mL) Accuracy: How close measurement is to true value. ○ 200µL - use 21-200µL (1µL - 0.001mL) Precision: Consistency of repeated measurements, regardless of accuracy. ○ 1000µL (1mL) 201-1000µL Micropipette: Tool for transferring small liquid volumes (e.g., microliters). ○ 5000µL (5mL) 1.01mL-5mL Dilution Curve: Graph showing concentration vs. measurable property (e.g., absorbance). Section 2-20 20-200 200-1ml Spectrophotometry: Measuring light absorbance at specific wavelengths. Absorbance: Light absorbed by substance; higher for concentrated solutions. Top tens hund thous Straight Line Equation: y=mx+cy = mx + cy=mx+c; relates two proportional variables Middle unit tens hund (e.g., absorbance vs. concentration). Spectrophotometer Steps Bottom. DP unit tens UV Spectroscopy: Measures light absorption by a chemical; higher concentration = higher absorbance. Protein Assay: nm (nanometre): Unit of length; 1 nm=10^−9 m Protein: Macromolecule of amino acids linked by peptide Absorption Formula: Absorbance = constant × concentration × pathway bonds; essential for biological functions. Examples: Enzymes, hormones, antibodies. length. Importance: Protein assays used in biomedical research, Cuvette: Tube for solutions; 1 cm light path; clear sides for light clinical diagnosis (e.g., metabolic, neurodegenerative transmission. diseases). Display: Top = absorbance; bottom = wavelength (adjustable). Beer’s Law: Wavelengths: Blue light: 400–450 nm, Red light: 700–750 nm, UV range: A=εcb 185–400 nm ε: Extinction coefficient. c: Concentration. Solution Colours: Lighter colour = lower setting; darker colour = higher b: Path length (1 cm). setting Absorbance = Extinction Coefficient × Concentration × Modes: Set to Abs for absorbance Path Length. Steps for Using a Spectrophotometer: Concentration = 1. Zero Calibration: Use distilled water or blank to set electrical zero. If given extinction coefficient in M: absorbency = E x C x L 2. Cuvette Handling: Hold frosted side; avoid grease; fill 1 cm from top; align If working out concentration from absorbance: arrow to reader. concentration = absorbance / E x L 3. Absorbance Reading: Insert solution, close lid, allow settling, press CAL to Standard Curve: Prepare protein solutions to create a zero, then measure. calibration curve for determining unknown concentrations. 4. Repeat for Solutions: Start with weakest solution, record absorbance. Steps 5. Plot Data: Graph absorbance on a calibration curve. Prepare Starch Solution Add Starch Solution to Tubes (control/blank). Colorimetric analysis, spectrophotometer, particular wavelength absorbed Add Iodine Solution: Add 1 drop of iodine to each solution, amount absorb proportional 2 concentration of absorbing substance Fill cuvettes with solutions starting from Tube 1 (lowest in solution (Beer’s Law). Linear relation between absorbance and concentration). concentration. Absorbance is directly proportional to concentration. A = - Set spectrophotometer to 610 nm. log10(I/Io) Blank spectrophotometer with Tube 8 (water). Io = This is the intensity of light passing through a solution that does not Record absorbance for each tube in a table. contain the compound. Calculate Starch Concentration: I = This is the intensity of light passing through the same solution except that Use formula: Concentration=initial starch concentration the compound is present. Prefix Sym Factor /dilution factor pH meter steps: Example for Tube 1:Dilution factor = 10/0.5=20 Kilo k 103 Switch On: ensure it is in pH mode (hold Concentration = 1%/20=0.05%: Repeat for all tubes and mode button if needed). add concentrations to the table. Deka da 101 Use distilled water to rinse the probe before Plot Standard Curve: and after use to prevent contamination. Deci d 10-1 Calibrate: Use Excel to plot absorbance vs. starch concentration. Determine Sample X Concentration:Use the calibration Centi c 10-2 Place probe in a pH buffer solution. curve to find concentration of Sample X.Express result Press CAL; wait until the pH reading Milli m 10-3 in g/cm3. Determine concentration from graph. stabilizes (stops flashing). Measure pH: Enzyme Assay: Micro µ 10-6 Rinse the probe, place it in the test solution, Enzyme: Biological catalyst, usually a protein, speeds up Nano n 10-9 and press measure. specific reactions. Store Probe: Example: Pepsin (breaks down food in the stomach). Pico p 10-12 Rinse with distilled water. Disease Indicators: Enzyme function reveals early signs of disease. Place in electrode storage buffer (fully Make range of known Assays: Measure enzyme activity using absorption or submerged). fluorescence spectroscopy: Monitored via a colourimetric concentrations, Measure A of Never let the probe dry out. reaction (spectroscopy). solution of unknown concentration, Determine Switch Off: Turn off the pH meter after use. Rate of Reaction: Compare rates at different substrate concentration from graph. concentrations. Core Biology Cheat Sheet 2 - Moles Mass Molarity Equations to Know Terminology: Amount/Mass: The quantity of matter in a substance, measured in grams (g) or kilograms (kg). Example: 40 g of NaCl is the mass of sodium chloride. Volume: The space occupied by a substance, measured in liters (L) or milliliters (mL). Example: A beaker holding 500 mL of water shows its volume. Concentration: The amount of solute in a given volume of solution, measured in moles/L (M) or grams/L. Example: A 1M NaCl solution contains 1 mole of NaCl per liter of solution. w/v (Weight/Volume): The mass of solute (g) per 100 mL of solution. Example: A 5% w/v solution = 5 g of solute in 100 mL solution. v/v (Volume/Volume): The volume of solute (mL) per 100 mL of solution. C1V1=C2V2 Example: A 10% v/v ethanol solution = 10 mL of ethanol in 100 mL solution. C1 is the concentration of the stock solution (mol/L). Mole: A unit representing 6.022×1023 entities (Avogadro’s number). Example: V1 is the volume of the stock solution required (mL), 1 mole of NaCl = 6.022×1023 formula units. C2​ is the final concentration after dilution (mmol/L) V2​ is the final total volume of the solution (L) Molarity (M): The number of moles of solute in 1 liter of solution. Example: A 1M HCl solution contains 1 mole of HCl per liter. Avogadro’s Number: 6.022×1023, the number of entities (atoms, molecules, ions) in 1 mole. Example: 1 mole of carbon = 6.022×1023 atoms. Molar Solution A molar solution contains 1 mole of solute dissolved in 1 liter of solution. For example, a 1 M NaCl solution contains 1 mole (58.44 g) of NaCl dissolved in 1 liter of water. What is a 1% (w/v) solution? A 1% (w/v) solution contains 1 gram of solute per 100 mL of solution. For instance, dissolving 1 g of sugar in water and making up the volume to 100 mL results in a 1% (w/v) solution. Absorbance 1ml = 10-3L 1microlitre = 10-6L A = absorbance 1nanolitre = 10-9L C = concentration mmol/L=(mg/dL x10) over molecular weight (working out the range in mmol.l -1 when given a concentration in mg/ml - you have been given the molecular weight). Absorbance Calculations Beer-Lambert Law When given the absorbency and asked to find the concentration of dilution. The Beer–Lambert law states that there is a linear Concentration = absorbance / (extinction coefficient x path length) relationship between the absorbance and the Concentration = original concentration (g/ml) x new result. concentration of a sample. This makes it possible to If diluted further x by the next dilution rate as well. calculate the concentration of a sample from its When asked to find the absorbance of a concentration of dilution: absorbance. The absorbance is measured by a Absorbance = Extinction coefficient x concentration x path length spectrophotometer at a specific wavelength of light that If given extinction coefficient in M: the substance absorbs. absorbency = E x C x L Definition: Linear relationship between absorbance and E = extinction coefficient concentration of a substance. C = concentration in M (of in mM convert to M) Application: Calculate unknown concentrations using a L = path length in cm spectrophotometer at specific wavelengths. Genetics Terminology Incomplete Dominance: A genetic situation where the heterozygous phenotype is intermediate between the two Chromosome: Structure of DNA and protein carrying genetic information. homozygous phenotypes. Example: RR(red flowers) × rr Homologous: Chromosome pairs with the same genes but possibly different alleles. (white flowers) = RrRrRr (pink flowers). Allele: Variant form of a gene (e.g., AAA, aaa). Codominance: A situation where both alleles are fully Locus: Specific location of a gene on a chromosome. expressed in the heterozygote. Example: A and B alleles in Dominant: An allele that masks the expression of a recessive allele. blood type result in AB blood, where both A and B antigens Recessive: An allele expressed only when two copies are present (aaaaaa). are present. Monohybrid: Cross studying one trait with two alleles (e.g., BbBbBb). Lethal Allele: An allele that causes death when present in a Genetic Cross: Mating of two organisms to study inheritance patterns. specific genotype, often in the homozygous state. Example: Pedigree: Family tree diagram showing inheritance of traits. In mice, YY (homozygous yellow coat allele) is lethal. True-Breeding Organism: Produces offspring identical to itself when self-crossed (AA or aa). Dihybrid Cross: A genetic cross involving two traits with two Genotype: Genetic makeup of an organism (BB,Bb,bbBB, Bb, bbBB,Bb,bb). alleles each. Normal F2 Ratio: 9:3:3:1 (dominant-dominant, Phenotype: Physical expression of a trait (e.g., brown eyes). dominant-recessive, recessive-dominant, recessive- F1 Generation: First-generation offspring from a genetic cross. recessive). Example: AaBb×AaBb for seed shape and color F2 Generation: Second-generation offspring from self-crossing F1 individuals. in pea plants. Homozygous: Having two identical alleles (BB or bb). Epistasis: Interaction between genes where one gene Heterozygous: Having two different alleles (Bb). masks or modifies the effect of another. Example: In Gamete: Reproductive cell (sperm or egg) carrying one allele per gene. Labrador retrievers, the coat color gene (B/b) is modified by a Test Cross: Cross to determine if an individual is homozygous or heterozygous. second gene (E/e), resulting in black, chocolate, or yellow Multiple Alleles: More than two alleles exist for a gene (e.g., A,B,OA, B, OA,B,O blood coats. types). Gene: A gene is a segment of DNA found on chromosomes Mutation: Change in DNA sequence that may alter a gene or trait. that codes for proteins or RNA, determining traits and Continuous genetic traits: influenced by genes and environment; height, weight, skin regulating functions in an organism. Genes are inherited from colour, heart rate, leaf length. parents and can be dominant or recessive, influencing how traits are expressed. For example, the gene for eye color may have alleles for brown (BBB) or blue (bbb). Core Biology Cheat Sheet 3 - Titration and Buffering Basic Lab Rules Risk Assessment: All activities assessed; low Buffering and Titration risk if instructions followed. Buffer: Mixture maintaining solution pH near neutral (around 7). Preparation: Importance: Biochemical processes require stable pH; large pH changes can Read instructions carefully. cause diseases (e.g., acidosis, alkalosis). Arrive on time for safety briefings (latecomers may be Body Buffer Systems: denied entry). Carbonic acid/bicarbonate buffer. Personal Appearance: Phosphate buffer. Tie back long hair, secure loose clothing. Protein buffer. No open-toed shoes or sandals. pH Imbalance: Malfunctioning lungs/kidneys disrupt blood pH. PPE Requirements: Wear lab coat (done up), safety glasses, and gloves. Neutralization Reaction: Remove PPE when leaving the lab. Example: HCl+NaOH→NaCl+H2O Wash hands before leaving. Techniques to Find Neutralization Point: Prohibited Activities: Titration with indicator: Approximate endpoint. No eating, drinking, chewing gum, smoking, applying Titration with pH meter: Accurate endpoint. cosmetics, or mobile phone use. Exceptions for photos: Remove gloves before using phone, then put on new gloves. Key Terms and Definitions Waste Disposal: Buffer: Solution that resists pH changes when acids or bases are added. General solids: Orange bags. Neutralization: Reaction between an acid and base to produce a salt and Pipette tips: Bench pot. water. Broken glass/Sharps: Special bin. Titration: Technique to determine unknown concentration by adding a Liquids: Liquid waste pots. standard solution until equivalence point. Behavior: Equivalence Point: Moles of acid = moles of base (neutralization complete). No running; handle chemicals and equipment carefully. Indicator: Substance that changes color at specific pH range (e.g., No unsupervised work in the lab. phenolphthalein). Fire Safety Rules pH Curve: Graph showing pH changes during titration (pH vs. volume added). Suspected Fire: Raise the alarm immediately. pKa: Logarithmic measure of an acid's dissociation constant; helps select If Alarm Sounds: indicators. Make experiment safe (e.g., turn off Bunsen burner). Remove PPE and evacuate to designated area. Evacuation: How to perform Titration Do not collect personal belongings. Set Up Equipment: Calibrate pH meter or prepare indicator solution. First Aid: Call ARU security for assistance or a first-aider. Perform Titration: Add titrant from a burette to analyte, record volumes and pH changes. Purposes Identify Endpoint: Use pH meter (accurate) or indicator (approximate). Buffering: Understand resistance of solutions to pH Analyze Data: Plot pH curve to confirm equivalence point and calculate changes. unknown concentration. Titration: Determine unknown concentrations of acids/bases. Reasons for Each Step pH Curve: Identify equivalence point and acid/base Calibrate Equipment: Ensures accurate pH readings. strength Add Slowly Near Endpoint: Prevent overshooting equivalence point. Use Indicator or pH Meter: Indicator gives approximate endpoint; pH meter provides precise data. What it tells us Plot pH Curve: Visualize titration progress and identify sharp pH change at Concentration: Exact amount of solute in solution equivalence point. (mol/L). Clean Equipment: Avoid contamination for reliable results Strength of Acid/Base: Through pKa or pH values. Buffer Capacity: How well a solution resists pH changes. Titration Titration with Indicator Neutralization Reaction: Acid reacts with a base to produce a salt Fill burette with 0.1 mol/L NaOH and water. Add 25 mL of HCl to a flask, and 3 drops of phenolphthalein. Example: HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l) Add NaOH slowly while swirling. Net Ionic Equation: H++OH−→H2O Stop when color changes, then add dropwise for consistency. Titration: Use n=C⋅V to calculate moles of NaOH added. Process to determine concentration of an acid or base using a standard solution. Titration with pH Meter Uses indicators or a pH meter to identify the equivalence point Calibrate pH Meter: Use pH 4.01 buffer solution. (moles of H+= moles of OH−). Add 25 mL of HCl to a beaker. pH Curve: Insert pH probe and record initial pH. Sudden pH change occurs near the endpoint. Start with larger increments (e.g., 5 mL), reduce to 0.5 mL, then Indicators change color within specific pH ranges. 0.1 mL near the endpoint. Record pH after each addition and mix thoroughly. Apparatus and Materials Plot pH Curve Graph pH (y-axis) vs. NaOH volume (x-axis). Phenolphthalein indicator (pink endpoint for strong acid/strong Endpoint is where pH changes sharply. base). Dilute HCl (unknown concentration). Indicator Selection: Standard 0.1 mol/L NaOH Strong Acid/Strong Base: Phenolphthalein or Methyl Orange. Burette, clamp, flasks, pH meter, buffer solution (pH 4.01). Weak Acid/Strong Base: Phenolphthalein. Strong Acid/Weak Base: Methyl Orange. Core Biology Cheat Sheet 4 - Mendelian Genetics Purpose Predicting offspring traits in breeding experiments. Mendel’s Laws Understanding inheritance of genetic disorders. Law of Segregation: Basis for modern genetics and molecular biology. Each organism inherits two alleles for each trait, one from each parent. Gamete formation, alleles separate so each gamete carries only one allele. Monohybrid Cross Example: For a trait Bb, gametes will carry either BB or bb. A cross between two individuals to study the Law of Independent Assortment: inheritance of a single trait with two alleles (e.g., BBB Alleles for different traits segregate independently of each other during gamete and bbb). Example: Cross between a tall plant (TtTtTt) formation. and a short plant (tttttt) to determine height inheritance. Applies to genes on different chromosomes. Example: Seed color (yellow or green) and seed shape (round or wrinkled) are Trait: Height inherited independently. T t Dominant (TTT) = Tall Law of Dominance: Recessive (ttt) = Short Some alleles are dominant and mask the expression of recessive alleles. T TT Tt Genotype Ratio: Dominant traits are expressed if at least one dominant allele is present. 1:2:1(TT:Tt:tt). Example: BB and Bb result in the dominant phenotype, while bb expresses the Phenotype Ratio: recessive trait. t Tt tt 3:1(Tall:Short). Probabilities: Use the ratios to calculate the likelihood Ambiguity Cases of each outcome. Two healthy parents (CFcf×CFcf) have a son with cystic fibrosis. Their Tall offspring: 75%75\%75%. second son does not have the disease. Conclusion: Both parents must be Short offspring: 25%25\%25%. carriers (CFcf). CFCF: Normal (25%) CF cf Question Example CFcf: Carrier (50%) In a breeding of BbxBb producing 4 offspring. What is cfcf: Sufferer (25%) CF CFCF CFcf the chance exactly one pup is white and rest are Given he does not suffer (cfcfcf excluded), brown. (B=brown DOM) (b=white (REC)? only 3 outcomes remain: CFCF,CFcf,CFcf. Ans: create 4 punnett squares. 1 white, 3 brown. Carrier Probability: ⅔. cf CFcf cfcf Times the fractions all together. ¼ x ¾ x ¾ x ¾ =27/256 The second son (genotype unknown, CFCF or CFcf) has a child with a woman who is a carrier (CFcf). Chance that the 2nd sons child has cfcf if dad is CFcf is ¼ , but the chance that dad is CFcf is ⅔. Chance that his child is a sufferer = ¼ x ⅔ = 2/12 or 1/6 Hardy-Weinberg Formula Allele frequencies p= frequency of A Multiple Alleles - Question Example q= 1-p= frequency of a Breeding together any Genotype frequencies black or brown F1 what p2= frequency of AA is the probability of a 2pq= frequency of Aa white rabbit? q2= frequency of aa Four possible If a population is at equilibrium, the allele frequencies will not change over breeding combinations to generate F2: time. The formula can be used to calculate allele or genotype frequencies. Rules to be applied: 1. All organisms are diploid 2. Sexual reproduction only 3. No overlapping generations 4. Mating is random 7. No migration 8. No mutation Only one of the four possibilities results in a white ¼. 5. Population size is infinitely large Only 1 in 4 of that chance is white ¼ 6. Allele frequencies are equal in the sexes 9. No selection ¼ x ¼ = 1/16 Dihybrid Crosses Normal F2 ratio of dominant to recessive phenotypes This is a typical dihybrid cross involving two traits: from a true breeding monohybrid (AA x aa =F1 with 1. Seed shape: Aa) cross: 3:1 ○ RRR: Round (dominant) RY Ry rY ry ○ rrr: Wrinkled (recessive) Terms: 2. Seed color: Transformation: Uptake of foreign DNA from the ○ YYY: Yellow (dominant) RY RRYY RRYy RrYY RrYy environment into a cell's genome. Example: Bacteria ○ yyy: Green (recessive) absorbing antibiotic resistance genes. Conjugation: Direct transfer of genetic material between two Ry RRYy RRyy RrYy Rryy Round seeds (R_): 9/16 cells via a pilus. Example: Plasmid exchange in bacteria. Wrinkled seeds (rr): 3/16 Transduction: Transfer of DNA between cells by a virus rY RrYY RrYy rrYY rrYy (bacteriophage).Example: Viral infection carrying bacterial Yellow seeds (Y_): 12/16 Green seeds (yy): 4/16 genes to another bacterium.Polymorphism: The presence of If asking for a number of a ry RrYy Rryy rrYy rryy multiple alleles or genetic variations in a population. population times the fraction Example: Human blood types (A, B, O). by the population number: Genetic Drift: Random changes in allele frequency in a Out of 1000 offspring how many would you expect to have yellow wrinkled seeds: population, especially in small populations. Example: Loss of 3/16 x1000 = 187.5 = 188 seeds rare alleles due to a natural disaster.