Metric System and Measurement

Measurement and the Metric System

• Fundamental units of measurement include length (meter, m), mass (kilogram, kg), volume (liter, L), time (second, s), and temperature (Kelvin, K).
• The metric system is based on powers of ten.
• Converting to smaller units involves moving the decimal to the right, converting meters to centimeters.
• Converting to larger units involves moving the decimal to the left, converting milligrams to grams.
• Prefixes include kilo- (k) = 1000, hecto- (h) = 100, deka- (da) = 10, base unit (m, g, L) = 1, deci- (d) = 0.1, centi- (c) = 0.01, milli- (m) = 0.001.
• The Metric System (SI) is based on powers of ten, and the Imperial System is mainly used in the U.S.
• The Imperial System involves units like inches, feet, pounds, and gallons
• Conversion factors can be used to convert between metric and English units, for example, 1 inch = 2.54 cm, 1 pound = 0.4536 kg, and 1 gallon = 3.785 liters.
• Mass is measured using an electronic balance and recorded in grams (g); zero the balance first.
• Volume is measured using a graduated cylinder or pipette, measured at the bottom of the meniscus.
• Length is measured using a ruler or meter stick, recorded in meters (m), centimeters (cm), or millimeters (mm).

Meniscus and Variables

• A meniscus is the curved surface of a liquid in a container.
• Read a meniscus at eye level and at the bottom of the curve.
• The independent variable is changed or controlled such as, the volume of liquid.
• The dependent variable is measured in response such as, the mass of liquid.
• An independent variable is plotted on the x-axis of a graph.
• A dependent variable is plotted on the y-axis.

Graphs and Equations

• A bar graph is used for categorical or discrete data (e.g., different types of liquids).
• A line graph is used for continuous data (e.g., volume vs. mass).
• A line of best fit represents data points on a scatter plot, determines trends and makes predictions
• The equation for a straight line is y = mx + b, where m (slope) is the rate of change (e.g., density of water) and b (y-intercept) is the value of y when x = 0.
• Density is determined by Density (D) = Mass (m) / Volume (V) and is measured in g/mL or g/cm³.

Scientific Method

• The scientific method involves observation, question formulation, hypothesis proposal (a testable explanation), experimentation, data collection and analysis, conclusion drawing, and communication and replication.
• An independent variable is deliberately changed, like the type of sugar used in fermentation.
• A dependent variable is the factor measured in response to changes in the independent variable, like fermentation rate.
• A control group is used as a baseline comparison, such as yeast in water without sugar.
• A positive control produces a known result, confirming the experiment works correctly, like using glucose.
• A negative control should not produce a result, ensuring no contamination, like water without sugar.
• Controlled variables are kept constant to ensure reliability, such as incubation temperature.
• A hypothesis can never be proven true, only supported or refuted due to falsifiability; new evidence can contradict previous conclusions.
• An enzyme is a biological catalyst speeding up chemical reactions, where yeast produce enzymes like invertase and zymase to break down sugars during fermentation.
• Aerobic metabolism requires oxygen and produces more ATP, its equation shown by Sugar + O₂ → H₂O + CO₂ + Energy
• Anaerobic metabolism (fermentation) occurs without oxygen and produces less ATP, its equation shown by Sugar → Ethanol + CO₂ + Energy
• Aerobic metabolism is more efficient, occurring in the presence of oxygen, while anaerobic metabolism (fermentation) occurs when oxygen is absent, resulting in ethanol or lactic acid production.
• Yeast uses fermentation to break down sugars in the absence of oxygen, producing ethanol, CO₂, and energy.
• Glucose is expected to be metabolized at the highest rate because it is a simple sugar.
• The yeast + water trial serves as a negative control to ensure observed fermentation is due to sugar metabolism.
• Incubation allows yeast to activate and metabolize sugar before measuring CO₂ production and captures fermentation at an active stage.
• Sealing the test tube creates an anaerobic environment, ensuring fermentation instead of aerobic respiration occurs.

Spectrophotometry

• Absorbance (A) measures the amount of light absorbed by a solution, from 0 to 2.
• Transmittance (%T) measures the percentage of light passing through a solution, from 0% to 100%.
• Absorbance and transmittance are inversely related
• The color we see is determined by transmitted wavelengths
• A photon is a discrete packet of energy and is measured in nanometers (nm).
• The electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• The visible light spectrum is about 400 to 700 nm, with red about 630-700 nm, orange about 590-630 nm, yellow about 560-590 nm, green about 490-560 nm, blue about 450-490 nm, indigo about 420-450 nm, and violet about 400-420 nm.
• A spectrophotometer measures how much light a solution absorbs or transmits at different wavelengths and determines concentration by measuring absorbance.
• A blank contains only the solvent and removes background interference.
• To calibrate a spectrophotometer, select the correct wavelength, adjust the phototube output to 0% transmittance, and insert the blank to adjust to 0 absorbance.
• Absorbance is measured at different wavelengths to determine which wavelength the blue dye best absorbs.
• The maximum absorbance (λmax) indicates the wavelength where the dye absorbs the best light and is used to quantify unknown concentrations using a standard curve.
• The formula C1V1 = C2V2 is used to calculate final solution concentrations after dilution; where C1 and V1 is concentration and solution of the stock solution, and C2 and V2 is the concentration and volume of the new solution
• Equation ensures solute remains while changing the volume
• A standard curve is concentrations (x-axis) vs absorbance (y-axis): Prepare solutions, measure absorbance, then determine an unknown concentration by tracing it from the y-axis
• Increasing dye concentration increases absorbance
• Beer’s Law states absorbance is directly proportional to concentration.

Light Microscopes

• Microscope framework provides support.
• The stage holds the slide.
• A light source illuminates the specimen from below.
• The ocular lens (eyepiece) magnifies the image.
• Objective lenses provide magnification levels, such as 4X, 10X, 40X, and 100X
• A condenser lens focuses light onto the specimen.
• A diaphragm lever controls light intensity and contrast.
• Coarse and fine adjustment knobs are for focusing
• The base should be supported with one hand, the arm held closely to the torso with the other hand, and never more than one at a time.
• Magnification enlarges the specimen's image.
• Resolution distinguishes two adjacent points.
• Contrast is the brightness difference between the specimen and background, which is enhanced using dyes or adjusting the diaphragm.
• Firstly, the 4X (low power) objective lens should be used initially when searching for a sample.
• Objective lens magnification includes: Scanning (4X) is 4X; Low Power (10X) is 10X; High Power (40X) is 40X; Oil Immersion (100X) is 100X
• Total magnification equals Ocular Lens × Objective Lens Magnification, that is, 10X x 40X = 400X
• Rotate the 10X objective lens, set the iris diaphragm, use the coarse focus knob, the fine focus knob, adjusting the diaphragm lever.
• The coarse adjustment knob is only to be used with low power (4X or 10X) bring a specimen into rough focus.
• The coarse adjustment knob with high power (40X or 100X) must NOT be used.
• An ocular micrometer is a small ruler inside the eyepiece for measuring microscopic specimens and determining the specimen size
• The number of ocular spaces spanning the sample calculates the actual size; space distance varies with various objective lenses
• Specimen Size = Number of ocular spaces × Measurement per space (based on lens)
• At 40X = 25 μm; 100X = 10 μm; 400X = 2.5 μm per space.
• Depth of field is the vertical range in focus.
• Lower magnification provides greater depth of field, while higher magnification provides a shallower depth of field.

Cell Differences

• Plant cells have a rigid cell wall, contain chloroplasts, have a large central vacuole, and are typically rectangular
• Animal cells lack a cell wall, lacks chloroplasts, have small vacuoles (if any), are more rounded or irregular in shape.

Organic Molecules

• Carbon is the backbone of organic molecules that can form four covalent bonds due to its valence electrons.
• A functional group is a specific group of atoms that gives the molecule distinctive properties; can be identified where atom groupings attach.
• Common functional groups include Hydroxyl (-OH), Carboxyl (-COOH), Amino (-NH₂), Phosphate (-PO₄³⁻), Sulfhydryl (-SH), Carbonyl (C=O), and Methyl (-CH₃).
• Monomers are small and join to create larger molecules, while polymers are larger molecules composed of smaller monomers
• Carbohydrates can be recognised by their ring structure; proteins look for amino groups, carboxyl groups and peptide bonds; Lipids look for long hydrocarbon chains and glycerol; Nucleic acids features sugar, phosphate groups and nitrogenous
• A molecular formula shows only the number and type of atoms and structural ones show how atoms are arranged and bonded within the molecule.
• Elements are listed by Carbon, Hydrogen, then Oxygen, then increasing electronegativity.
• Ball and stick model rods are covalent bonds and balls are atoms.
• Ball-and-stick have colours for the atoms such as: Carbon is black, Hydrogen is white, Oxygen is red, Nitrogen is blue, Phosphorus is orange and Sulfur is yellow
• Isomers share the same molecular formula with different structures, however their structural formula still differ
• Structural isomers connect differently; cis-trans (geometric) isomers have a different spatial arrangement; Enantiomers are mirror images
• Carbohydrates are polar (hydrophilic) due to hydroxyl (-OH) groups.
• Proteins Varies based on R-group and can be polar and non polar
• Lipids are mostly nonpolar (hydrophobic) due to long hydrocarbon chains
• Nucleic Acids are polar (hydrophilic) due to phosphate groups
• Monomers and functional groups include carbohydrates (Hydroxyl), Proteins (Amino, Carboxyl), Lipids (Carboxyl, Hydroxyl, Phosphate), Nucleic Acids (Phosphate, Hydroxyl, Amine)
• Atoms in macromolecules: Carbohydrates (C, H, O), Proteins (C, H, O, N, sometimes S), Lipids (C, H, O, sometimes P), Nucleic Acids: C, H, O, N, P
• General formula for carbohydrates is (CH₂O) , where "n" is the number of carbon atoms.
• Kinds of lipids: Glycerol (3 fatty acids), Phospholipids (2 fatty acids and phosphate), Steroids (Four fused carbon rings), Waxes (alcohol bond to fatty acid)
• Saturated fats are solid and straight, unsaturated fats are liquid and bent.
• Amphipathic molecules have polar and nonpolar regions.
• Amino side group, carboxyl side group, hydrogen atom and R group (varies down below) are all apart of the amino acid
• What Makes the R group chemical uniqueness: Chemical properties, folding and funcxning

Polypeptides and Nucleic Acids

• N-terminus: Amino group (-NH₂)
• C-terminus: Carboxyl group (-COOH)
• Backbone sequebces for polypeptides that repeats.
• Nucleuic acid:Phosphate group (-PO₄³⁻), and Nitrogenous base (A, T, G, C, or U)
• Sugars in RNA are: Ribose sugars, and they replace thymine for Uracil instead
• Difference between purities and pyrimidines: Adeline, Gwanine and Cytosine,thymine and Uracil belong to structure.