Bio

What characteristics are shared by all living organisms?

Are made of cells, composed of a common set of molecules, carry out metabolism, contain genetic information, use a universal molecular/genetic code, regulate their internal environment, reproduce, and exist in populations that evolve.

Why is the cell considered a fundamental unit of life?

Because living systems are cellular. Cells provide the physical organization necessary for metabolism, regulation, genetic information, and reproduction.

What is metabolism and why is it a characteristic of life?

Metabolism is the set of chemical processes through which organisms acquire, transform, and use matter and energy.

What is abiogenesis?

Abiogenesis refers to the origin of life from nonliving matter through chemical evolution.

What did the Miller-Urey experiment demonstrate?

It demonstrated that certain organic molecules, including amino acids, could form under experimentally simulated conditions.

How did photosynthesis influence the history of life?

Photosynthesis increased the availability of O₂ in Earth’s environment, enabling the evolution of aerobic metabolism.

Why is increased atmospheric oxygen evolutionarily important?

Oxygen can serve as an electron acceptor in aerobic metabolism, yielding more ATP and allowing for greater activity, larger bodies, and more energetically expensive processes.

What is endosymbiosis?

Endosymbiosis is the evolutionary process in which one organism lives within another and the relationship becomes integrated into the biology of the host.

How did multicellularity evolve?

Through cellular specialization within cell colonies, allowing cells to perform specialized functions.

What factors contributed to the Cambrian explosion?

Higher O₂ levels, efficient aerobic respiration, evolution of predation, and Hox gene duplication.

What evidence supports the idea that all life shares a common origin?

Living organisms share cells, metabolism, genetic information, and the universal genetic code.

What is the relationship between genes, genomes, and genetics?

Genes are units of genetic information; genomes are complete genetic information; genetics is the study of heredity.

How does natural selection produce evolutionary change?

Natural selection changes the genetic composition of populations as individuals with favorable traits reproduce more.

What mechanisms can produce evolutionary change?

Natural selection, sexual selection, genetic drift, gene flow, and mutation.

What is the basic logic of the scientific method?

Observation → question → hypothesis → prediction → experiment → data → statistical analysis → conclusion → replication.

What is inductive reasoning?

Reasoning from specific observations to general conclusions.

What is deductive reasoning?

Reasoning from a general principle or hypothesis to specific predictions.

What must a hypothesis generate?

Testable predictions.

What is a null hypothesis?

It states that there is no effect, difference, or relationship.

Why do scientists use null hypotheses?

To evaluate if observed data are inconsistent with the null hypothesis.

What is a controlled experiment?

An experiment that controls variables other than the factor being tested.

What is a comparative experiment?

An experiment that compares different conditions/groups to determine variable impacts.

Why are uncontrolled variables a problem?

They create alternative explanations for results.

Why are experiments involving animals relevant to human biology?

Different organisms share evolutionary ancestry and biological mechanisms.

What are the three major subatomic particles?

Proton (+1 charge, 1 Da mass, located in nucleus), Neutron (0 charge, 1 Da mass, located in nucleus), Electron (-1 charge, ~0 mass, located in orbitals).

What determines an element’s identity?

The number of protons, known as the atomic number.

What is the atomic number?

The number of protons in the nucleus.

What is the mass number?

Mass number = protons + neutrons.

If an atom has 17 protons and 18 neutrons, what are its atomic number and mass number?

Atomic number = 17; Mass number = 35.

What is an isotope?

A form of an element with a different number of neutrons.

Compare oxygen-16 and oxygen-18.

Oxygen always has 8 protons; Oxygen-16 has 8 neutrons, while Oxygen-18 has 10 neutrons.

What is a radioisotope?

An unstable isotope that releases energy through radioactive decay.

Why can radioactive decay sometimes create a different element?

It may change the number of protons, altering elemental identity.

What determines where an element appears on the periodic table?

Elements are arranged by increasing atomic number.

Why do elements in the same column have similar chemical properties?

They have similar valence-electron configurations.

What is the valence shell?

The atom’s outermost occupied electron shell.

Why are valence electrons important for chemistry?

They participate in chemical bonding and influence reactivity and molecular structure.

How does valence-shell configuration influence placement on the periodic table?

Elements in the same group have related valence-electron configurations, resulting in similar chemical behavior.

What is the octet rule?

Atoms tend to achieve a stable outer shell with eight valence electrons.

Why does bonding help a reactive atom achieve stability?

It allows atoms with incomplete valence shells to attain more stable configurations.

Why are atoms with unfilled outer orbitals more reactive?

They have less stable valence configurations.

What is a covalent bond?

A bond formed when atoms share one or more pairs of electrons.

Why are covalent bonds strong?

Shared electrons are attracted to the positively charged nuclei of both bonded atoms.

What is a single covalent bond?

A bond in which two atoms share one electron pair (2 electrons).

What is a double covalent bond?

A bond in which two atoms share two electron pairs (4 electrons).

What is a triple covalent bond?

A bond in which two atoms share three electron pairs (6 electrons).

Rank single, double, and triple covalent bonds by strength.

Single < Double < Triple.

Why does covalent-bond geometry matter biologically?

It influences a molecule’s three-dimensional shape, affecting its biological function.

What is electronegativity?

The attractive force an atomic nucleus exerts on electrons.

What is a nonpolar covalent bond?

A bond in which electrons are shared approximately equally between atoms.

What is a polar covalent bond?

A bond in which electrons are shared unequally due to differences in electronegativity.

Does a polar covalent bond mean the atoms have full charges?

No, they have partial charges (δ+ and δ−).

Why is O–H polar?

Oxygen is more electronegative than hydrogen, causing shared electrons to spend more time near oxygen.

How does an ionic interaction form?

An electron is transferred from one atom to another, producing oppositely charged ions that attract each other.

What is a cation?

A positively charged ion that has lost electrons.

What is an anion?

A negatively charged ion that has gained electrons.

What happens when calcium reacts with chlorine?

Calcium loses two electrons and forms Ca²⁺, while each chlorine gains one electron to form Cl⁻, resulting in CaCl₂.

What is a hydrogen bond?

An attraction between a hydrogen atom in a polar covalent bond and a strongly electronegative atom.

Why is an individual hydrogen bond weak compared with a covalent bond?

Hydrogen bonds arise from partial charges rather than direct electron sharing.

Why are hydrogen bonds biologically important?

Large numbers of hydrogen bonds stabilize biological structures.

What are hydrophilic interactions?

Interactions involving substances that interact favorably with water.

What are hydrophobic interactions?

The tendency of nonpolar molecules to aggregate together rather than interact favorably with water.

Why do nonpolar molecules tend to aggregate in water?

They cannot form favorable interactions with water, so clustering reduces their exposure to the aqueous environment.

What are van der Waals forces?

Weak, temporary attractions caused by fluctuations in electron distribution.

Why do van der Waals forces matter despite each interaction being weak?

Many weak interactions can collectively contribute significantly to molecular structure and stability.

What constitutes a chemical reaction?

Atoms collide with sufficient energy to combine or change their bonding partners.

What happens to atoms during a chemical reaction?

Atoms are rearranged.

State the law of conservation of energy.

Energy cannot be created or destroyed; it can only be transferred or transformed.

State the law of conservation of matter.

Matter cannot be created or destroyed in a chemical reaction; atoms are rearranged into new combinations.

Why is water a polar molecule?

Because it contains polar O–H covalent bonds and has a bent geometry, leading to an overall dipole.

Why does water's shape matter?

It determines whether bond polarities cancel, influencing water's strong interactions with other polar substances.

How many hydrogen bonds can one water molecule participate in?

Up to four hydrogen bonds.

What is specific heat?

The amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

Why does water have a high specific heat?

Much added energy is absorbed by disrupting hydrogen bonds, rather than increasing molecular motion.

What is the biological importance of water's high specific heat?

It helps stabilize temperatures in aquatic environments and organisms.

Why does water require a lot of energy to evaporate?

Hydrogen bonds must be disrupted sufficiently for molecules to escape into the gas phase.

What is the heat of vaporization?

The amount of heat required to convert a substance from liquid to gas.

Why does sweating cool the body?

Evaporation removes heat from the body due to the energy required for water to change states.

Why does ice float on liquid water?

Hydrogen bonds organize water into a more open structure upon freezing, increasing volume and decreasing density.

Why does ice floating matter biologically?

It insulates aquatic environments, allowing them to remain habitable during cold conditions.

What is cohesion?

Attraction between molecules of the same substance.

What is adhesion?

Attraction between different substances.

What is surface tension?

A consequence of strong cohesive forces at a liquid’s surface.

Explain how hydrogen bonding produces cohesion.

Hydrogen bonds form between partial charges in water molecules, leading to cohesive properties.

What does it mean to say water is a solvent?

Water can dissolve many substances, facilitating chemical reactions.

Why can water dissolve ionic compounds?

Water's partial charges interact with ions, facilitating their separation from ionic lattices.

Why are polar molecules generally more soluble in water than nonpolar molecules?

Polar molecules can form favorable interactions with water, whereas nonpolar molecules cannot.

Why are water's solvent properties important inside cells?

Cells require water for molecules to dissolve, move, and react with one another.

What is a mole?

A mole is an amount of substance containing approximately 6.02 × 10²³ particles.

What is Avogadro's number?

6.02 × 10²³ particles/mol.

What is molar mass?

The mass of one mole of a substance, expressed in g/mol.

What is the molar mass of H₂O?

≈ 18.02 g/mol.

How do you convert grams to moles?

moles = mass in grams / molar mass in g/mol.

How do you convert moles to grams?

grams = moles × molar mass.

What is molarity?

M = moles of solute / liters of solution.

Why must volume be in liters when calculating molarity?

Because molarity is defined as moles per liter.

A solution contains 0.20 mol glucose in 2.0 L. What is its molarity?

M = 0.10 M.

A student dissolves 5.85 g NaCl in 500 mL solution. What is the molarity?

M = 0.200 M.

What does 10 mM mean?

10 mM = 0.010 M = 10^{-2} M.

How many molecules are present per liter in a 10 mM solution?

6.02 × 10²¹ molecules/L.