Unit 1: Chemistry of Life Reading Guide

Vocabulary practice flashcards covering all key concepts, equations, and structures from Unit 1: Chemistry of Life, including the scientific method, biological statistics, basic chemistry, water properties, essential elements, and biological macromolecules.

Science

A systematic endeavour aimed at understanding the natural world through observation, experimentation, and logical reasoning.

Inquiry

The process of posing questions and seeking answers through systematic investigation, beginning with careful observations and data gathering.

Qualitative Observations

Observations in science that describe qualities, traits, or characteristics rather than numerical measurements.

Quantitative Observations

Observations in science that involve numerical measurements.

Inductive Reasoning

A form of reasoning that involves making generalizations based on specific observations.

Deductive Reasoning

A form of reasoning that uses logical inference to predict specific outcomes from general principles.

Hypothesis

A proposed explanation for a phenomenon or a tentative answer to a scientific question that can be tested through experimentation, typically written in the format: "If [cause], then [effect], because [rationale]."

Null Hypothesis ($H_0$)

A hypothesis stating that there is no significant relationship between the variables being studied, meaning any observed differences are due to random variation or chance.

Alternative Hypothesis ($H_1$)

A hypothesis proposing that there is a significant relationship between variables, implying that observed differences are due to the experimental treatment.

Scientific Law

A rule that describes an observable phenomenon that occurs consistently under specific conditions, often expressed mathematically.

Scientific Theory

A well-substantiated explanation supported by extensive evidence that explains the reasons behind a wide range of observations.

Independent Variable

The factor that is deliberately manipulated by the researcher; it represents the presumed cause in an experiment.

Dependent Variable

The factor that is measured or observed to assess the effect of the independent variable.

Positive Control

An experimental group exposed to a treatment known to produce a positive result, confirming that the experimental setup is capable of producing results.

Negative Control

An experimental group not exposed to the treatment that should not produce a result, helping identify external factors that might influence the outcome.

Constants

Factors that must be kept identical throughout the experiment across all groups to ensure that any effect on the dependent variable is due to the independent variable alone.

Statistics

A branch of mathematics used in biology to summarize, describe, and analyze experimental data to draw conclusions about biological phenomena.

Normal Distribution

A symmetric, bell-shaped distribution where most data points are concentrated around the middle (mean) value, with fewer data points appearing further from the center.

Mean

A measure of central tendency calculated by dividing the sum of all data points by the total number of data points.

Median

The middle value in a data set when the values are ordered from least to greatest.

Mode

The most frequently occurring value in a data set.

Range

A simple measure of variability calculated as the difference between the highest and lowest values in a data set.

Standard Deviation ($SD$)

A measure showing how much data points differ from the mean; in a normal distribution, $68\%$ of data falls within $1\,SD$, $95\%$ falls within $2\,SD$, and $99.7\%$ falls within $3\,SD$.

Standard Error ($SE$)

A statistical value ($SE = \frac{\sigma}{\sqrt{n}}$) that measures how accurately the sample mean estimates the population mean, decreasing as sample size increases.

Error Bars

Graphical representations of data variability; overlapping error bars suggest the difference may not be statistically significant, whereas non-overlapping error bars suggest a statistically significant difference.

Chi-Square ($\chi^2$) Test

A statistical test used to determine if there is a significant difference between observed ($O$) and expected ($E$) values in categorical data using the formula $\chi^2 = \sum \frac{(O-E)^2}{E}$.

Degrees of Freedom ($df$)

A statistical quantity calculated as the number of categories minus one ($n - 1$).

Matter

Anything that takes up space and has mass; makes up all living and nonliving things.

Element

A pure substance made of one kind of atom that cannot be broken down into simpler substances by chemical means.

Compound

A substance formed when two or more different elements combine in a fixed ratio, exhibiting properties different from its individual elements.

Essential Elements

Elements organisms need in large amounts to survive; carbon ($\text{C}$), hydrogen ($\text{H}$), oxygen ($\text{O}$), and nitrogen ($\text{N}$) make up $96\%$ of living matter.

Trace Elements

Elements required by organisms in minute quantities, such as iron ($\text{Fe}$), iodine ($\text{I}$), and zinc ($\text{Zn}$).

Atomic Number

The number of protons in the nucleus of an atom, which uniquely identifies an element.

Atomic Mass

The average mass of an element's atoms, usually expressed in atomic mass units ($\text{amu}$).

Octet Rule

The principle that atoms tend to gain, lose, or share electrons to fill their valence shell with $8$ electrons, achieving stability like noble gases.

Electronegativity

A measure of an atom's ability to attract and hold electrons in a chemical bond, increasing from left to right and from bottom left to top right on the periodic table.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between atoms (e.g., $H_2$, $O_2$).

Polar Covalent Bond

A covalent bond in which electrons are shared unequally due to differences in electronegativity, creating partial charges on atoms (e.g., $H_2O$).

Ionic Bond

A chemical bond formed when one atom donates an electron to another, creating positively charged cations and negatively charged anions that attract each other.

Hydrogen Bond

A weak bond between a hydrogen atom in one molecule and an electronegative atom (such as oxygen or nitrogen) in another molecule.

Acid

A substance that increases the concentration of hydrogen ions ($H^+$) in a solution by donating protons when dissolved in water ($pH < 7$).

Base

A substance that reduces the concentration of hydrogen ions ($H^+$) in a solution by accepting protons or producing hydroxide ions ($OH^-$) ($pH > 7$).

Buffer

A mixture of a weak acid and its conjugate base that resists changes in $pH$ by absorbing or releasing $H^+$ or $OH^-$ ions (e.g., the bicarbonate buffer system in blood at $pH \approx 7.4$).

Cohesion

The attraction between water molecules due to hydrogen bonding, creating surface tension and allowing water drops to bead.

Adhesion

The attraction between water molecules and other types of molecules, helping water cling to surfaces such as plant cell walls.

Transpiration (Xylem Transport)

The process of moving water upward against gravity from roots to leaves through the xylem, enabled by cohesion between water molecules and adhesion to xylem walls.

Capillary Action

The ability of water to flow upward in narrow spaces without external forces, driven by the combined effects of cohesion and adhesion.

High Specific Heat

The property of water that allows it to absorb or release large amounts of heat with only a slight change in its own temperature, moderating climate and internal body conditions.

Evaporative Cooling

The cooling mechanism that occurs when evaporating water carries heat away from a surface, regulating temperature during sweating or transpiration.

Density of Ice

The unique property where solid water is less dense than liquid water because hydrogen bonds form a stable crystalline lattice, causing ice to float.

Solution

A homogeneous liquid mixture consisting of a dissolving agent (solvent) and a dissolved substance (solute).

Organic Compounds

Chemical compounds primarily composed of carbon atoms bonded to hydrogen, oxygen, nitrogen, and other elements, typically found in living organisms.

Inorganic Compounds

Compounds that do not primarily consist of carbon-hydrogen bonds, such as water ($H_2O$), carbon dioxide ($CO_2$), and sodium chloride ($NaCl$).

Tetravalency

The property of carbon having four valence electrons, enabling it to form four covalent bonds and produce complex molecular structures.

Catenation

The ability of carbon atoms to covalently bond to other carbon atoms, forming extensive chains and cyclic ring frameworks.

Hydrocarbons

Organic molecules consisting entirely of hydrogen and carbon atoms, serving as fuels and major components of lipids.

Functional Groups

Specific clusters of atoms within organic molecules that have characteristic properties and chemical reactivities.

Hydroxyl Group

A functional group written as $-\text{OH}$; characterizes compounds known as alcohols (e.g., ethanol).

Carbonyl Group

A functional group written as $>\text{C=O}$; characterizes ketones and aldehydes (e.g., acetone, propanal).

Carboxyl Group

A functional group written as $-\text{COOH}$; acts as an acid and characterizes carboxylic acids or organic acids (e.g., acetic acid).

Amino Group

A functional group written as $-\text{NH}_2$; acts as a base and characterizes amines (e.g., glycine).

Sulfhydryl Group

A functional group written as $-\text{SH}$; characterizes compounds known as thiols (e.g., cysteine).

Phosphate Group

A functional group written as $-\text{OPO}_3^{2-}$; characterizes organic phosphates (e.g., glycerol phosphate).

Methyl Group

A nonpolar functional group written as $-\text{CH}_3$; characterizes methylated compounds (e.g., 5-methyl cytosine).

Monomer

A small, basic molecular unit that can join together with other units to form a polymer.

Polymer

A large molecule composed of repeating monomer units bonded together.

Dehydration Synthesis and Hydrolysis

Complementary metabolic reactions: dehydration synthesis covalently joins monomers into polymers by removing water, while hydrolysis breaks polymers into monomers by adding water.

Carbohydrates

Organic macromolecules composed of carbon, hydrogen, and oxygen usually in a $1:2:1$ ratio, functioning as primary fuel and structural material.

Monosaccharide

The simplest carbohydrate unit consisting of a single sugar molecule, such as glucose, fructose, or galactose.

Disaccharide

A carbohydrate formed by the condensation of two monosaccharides through a dehydration reaction (e.g., sucrose, lactose, maltose).

Polysaccharide

A macromolecule composed of long chains of repeating monosaccharide units joined together.

Starch

A storage polysaccharide in plants composed of glucose monomers.

Glycogen

A storage polysaccharide of glucose found in animal tissues.

Cellulose

A major structural polysaccharide of plant cell walls that provides rigid physical support.

Chitin

A structural polysaccharide found in the exoskeletons of arthropods and the cell walls of fungi.

Amino Acid Structure

The molecular subunit of proteins, containing an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), a hydrogen atom, and a variable side chain ($\text{R}$) attached to a central carbon.

Essential Amino Acids

The $9$ amino acids that cannot be synthesized by the human body and must be acquired through the diet.

Peptide Bond

A covalent bond formed by a dehydration reaction between the amino group of one amino acid and the carboxyl group of another.

Four Levels of Protein Structure

The hierarchical organization of proteins: primary (amino acid sequence), secondary ($\alpha$-helices and $\beta$-sheets), tertiary (3D shape from R-group interactions), and quaternary (assembly of multiple polypeptides).

Nucleic Acids

Macromolecules (DNA and RNA) that store and transmit genetic information, constructed from monomer units called nucleotides.

Nucleotide Structure

The monomer building block of nucleic acids, consisting of a pentose sugar, a phosphate group, and a nitrogenous base.

Pyrimidines

Single-ring nitrogenous bases including cytosine (C), thymine (T), and uracil (U).

Purines

Double-ring nitrogenous bases including adenine (A) and guanine (G).

Phosphodiester Linkage

The covalent bond that connects the phosphate group of one nucleotide to the sugar of an adjacent nucleotide, establishing a $5'$ to $3'$ directionality.

Triglyceride Structure

A lipid macromolecule composed of one glycerol molecule linked to three fatty acid chains via ester bonds.

Fatty Acid Saturation

Classification of fatty acids based on double bonds: saturated fatty acids contain only single bonds and are solid at room temperature, while unsaturated fatty acids contain one or more double bonds and are liquid at room temperature.

Trans Fats

Lipids created by hydrogenating oils that raise bad cholesterol ($\text{LDL}$) and lower good cholesterol ($\text{HDL}$), increasing heart disease risk.

Phospholipid Bilayer

A two-layered membrane structure composed of phospholipids, oriented with hydrophilic phosphate heads on the outer surfaces and hydrophobic fatty acid tails sequestered inside.

Steroid Skeleton

A lipid structural core characterized by four fused carbon rings, serving as the basis for hormones and cholesterol.