chpt 1 & 2

What properties do all living things share?

• Made of cells

• Growth, development, reproduction (controlled by DNA)

• Capture & use energy

• Metabolism (photosynthesis, cellular respiration/fermentation)

• Respond to external environment & regulate internal environment

• Populations evolve over time (natural selection)

What are the levels of organization in nature, from smallest to largest? Describe each.

• Atom — individual unit of an element.

• Molecule — two or more atoms bonded together.

• Organelle — structures inside cells that perform specific tasks.

• Cell — smallest unit with all characteristics of life.

• Tissue — group of cells with a common function.

• Organ — group of tissues working together for a shared function.

• Organ System — group of organs with related functions.

• Multicellular Organism — an individual living thing.

• Population — group of individuals of the same species in a certain area.

• Community — all species occupying an area.

• Ecosystem — community + physical environment.

What roles do producers, consumers, and decomposers play in an ecosystem? How does energy movement differ from chemical cycling?

Producers

• Make their own food (glucose + other carbohydrates).

• Use photosynthesis to convert light → chemical energy.

• Examples: plants, algae.

Consumers

• Eat producers and/or other consumers.

• Cannot make their own food.

Decomposers

• Eat remains and wastes.

• Return nutrients to the soil → recycled back to producers.

• Examples: worms, fungi, bacteria.

Energy vs. Chemicals

• Energy movement is one‑way.

  • Sun → producers → consumers → lost as heat.

• Chemicals are cycled.

  • Carbon, nitrogen, water, minerals move through organisms and the environment repeatedly.

Explain the overall energy conversions in photosynthesis, cellular respiration, and fermentation. What organisms perform each?

Photosynthesis

• Converts light energy → chemical energy (glucose).

• Occurs in plants and some microorganisms (algae).

• Plants cannot use glucose directly for energy.

  • They store glucose as starch.

  • They can convert glucose + fructose → sucrose to transport it through the plant.

Cellular Respiration

• Converts glucose → ATP (usable energy).

• Occurs in almost all organisms.

• Eukaryotic cells perform full cellular respiration.

• Extracts energy from glucose more efficiently than fermentation.

Fermentation

• Occurs when oxygen is not available.

• Prokaryotes may perform only fermentation.

• Produces less ATP than cellular respiration.

What is the function of DNA in living organisms? How do DNA and RNA work together to make proteins?

DNA

• Acts as the cell’s instructions for making proteins.

• Holds the information needed to build, maintain, and run the cell.

• Instructions are stored in the sequence of nucleotides.

How DNA & RNA Work Together

1. DNA is copied into RNA

   • This process is called transcription.

   • RNA is a working copy of the DNA instructions.

2. RNA assembles proteins

   • RNA guides the order of amino acids.

   • Proteins then build and maintain cells and carry out cell activities.

Why this matters

• Proteins do almost everything in the cell.

• DNA → RNA → Protein is the core flow of genetic information.

What is a species? What are the classification categories of organisms from broadest to narrowest?

Species

• A particular type of organism whose members can breed with each other in nature
  and produce fertile offspring.

Classification Categories (broad → narrow)

1. Domain

2. Kingdom

3. Phylum

4. Class

5. Order

6. Family

7. Genus

8. Species

Example from your notes:

• Ursus americanus (American black bear)

  • Domain: Eukarya

  • Kingdom: Animalia

  • Phylum: Chordata

  • Class: Mammalia

  • Order: Carnivora

  • Family: Ursidae

  • Genus: Ursus

  • Species: Ursus americanus

What are the main differences between prokaryotic and eukaryotic cells? What are the characteristics of archaea, bacteria, protists, fungi, plants, and animals?

Prokaryotic Cells

• Simple structure

• No true nucleus

• Lack most organelles

• Smaller

• Only one type of organelle

• Always single‑celled

Eukaryotic Cells

• Complex

• Have a true nucleus

• Many organelles

• Larger

• Can be single‑celled or multicellular

Domains with ProkaryotesDomain Archaea

• Live in extreme environments

  • Salt lakes, boiling springs, etc.

• Microscopic, single‑celled

• Prokaryotic

Domain Bacteria

• Common and extremely diverse

• Live everywhere

• Microscopic, single‑celled

• Prokaryotic

Domain Eukarya (all eukaryotic)Protists (multiple kingdoms)

• Mostly single‑celled, some multicellular

• Examples: paramecia, amoeba

Kingdom Fungi

• Almost all multicellular

• Feed externally by secreting enzymes and absorbing nutrients

Kingdom Plantae

• Multicellular

• Make their own food via photosynthesis

• Includes herbaceous & woody plants

Kingdom Animalia

• Multicellular

• Feed internally

• Includes invertebrates & vertebrates (fish, amphibians, reptiles, birds, mammals)

What is evolution? How does natural selection cause evolution? How can this process eventually lead to a new species?

Evolution

• Evolution = changes in the traits of a population over many generations.

• Populations evolve — individuals do not.

How Natural Selection Works1. Individuals vary in inherited traits

• Members of a population are not identical.

• These differences are heritable (passed to offspring).

2. Some trait forms are better suited to the environment

• Certain traits increase survival or reproduction.

• Individuals with these traits are more likely to survive.

3. Survivors reproduce

• Those with advantageous traits leave more offspring.

• Their traits become more common in the next generation.

4. Over many generations…

• Well‑suited traits become more common.

• Poorly suited traits become less common.

• The population has evolved.

How Natural Selection Can Lead to a New Species

• If gradual changes accumulate over very long periods,
  and populations become genetically different enough,
  they may no longer be able to interbreed.

• At that point, a new species has formed.

What is scientific inquiry? What are the steps of the scientific method, and what happens at each step?

Scientific Inquiry

• A rigorous, formalized process of trial‑and‑error testing used to figure out how the universe works.

• It never proves anything with 100% certainty — data only supports or does not support a hypothesis.

Steps of the Scientific Method1. Observation

• You notice something in the natural world.

• This sparks curiosity or reveals a pattern.

2. Question

• You ask why or how something happens.

3. Hypothesis

• A testable explanation for the observation.

• Must be specific and measurable.

4. Prediction

• What you expect to happen if the hypothesis is correct.

5. Test / Experiment

• You design and run an experiment to test the prediction.

• Collect data carefully and systematically.

6. Results

• Analyze the data.

• Determine whether the results support or do not support the hypothesis.

• Never “prove” — only support.

Design an experiment to test a given hypothesis. Include experimental group, control group, independent variable, dependent variable, constants, and procedures.

Example Hypothesis

“Tomato plants given a supplement of club soda will grow taller than tomato plants not given club soda.”

Key Parts of the ExperimentIndependent Variable

• Amount of club soda supplement given to the plants.

Dependent Variable

• Plant height (measured over time).

Control Group

• Tomato plants that receive no club soda (only regular water).

Experimental Group

• Tomato plants that receive club soda as a supplement.

Constants (everything kept the same except the independent variable)

• Plant species and developmental stage

• Amount of light

• Soil source and chemical composition

• Total amount of liquid added

• Container size and spacing

• Atmospheric conditions

• People caring for and measuring the plants

• Duration of the experiment

• Measurement method

Procedure (must be planned BEFORE starting)

• Decide how plants will be set up (same pots, same soil, same location).

• Determine how often plants will be watered and how much club soda is added.

• Decide how height will be measured (e.g., cm from soil to top).

• Choose how long the experiment will run.

• Record data consistently.

• Analyze results statistically to determine whether club soda had an effect.

What is a scientific theory? How can scientific theories change over time?

What a Scientific Theory Is

• A broad explanation of how the natural world works.

• Supported by large amounts of evidence from many independent studies.

• Theories are both:

  • Explanatory (explain existing data/observations)

  • Predictive (predict what should happen in new experiments or natural observations)

How Theories Become Stronger

• Repeated testing and repeated observations.

• Evidence from multiple independent lines of inquiry converges.

• Peer review and scientific debate refine the explanation.

How Theories Can Change

• Theories are never final — they remain open to further testing.

• New evidence can:

  • Strengthen a theory

  • Modify/refine it

  • Weaken it

  • Or, in rare cases, replace it with a better explanation

Important Distinction

• Hypothesis ≠ Theory

  • Hypothesis: narrow, testable, based on a single experiment or question

  • Theory: broad, well‑supported explanation built from many studies

What is matter made of? What are elements and atoms? What are the charges, sizes, and locations of protons, neutrons, and electrons?

Matter Is Made of Elements

• Elements = pure, fundamental substances.

• Cannot be broken down by ordinary chemical means.

Atoms

• Smallest unit of an element that still retains that element’s properties.

• Made of protons, neutrons, electrons.

Subatomic ParticlesProtons

• Charge: + (positive)

• Size: same size as neutrons

• Location: nucleus

Neutrons

• Charge: none (neutral)

• Size: same size as protons

• Location: nucleus

Electrons

• Charge: – (negative)

• Size: much smaller than protons & neutrons

• Location: orbit in shells around the nucleus

What is a chemical bond? What are the characteristics of a compound?

Chemical Bond

• A union between two atoms.

• Forms when atoms transfer or share electrons.

• Bonding allows atoms to fill their outer electron shells and become more stable.

Compound

• A substance made of two or more different elements bonded together.

• The elements are present in a fixed ratio.

  • Example: Water (H₂O) always has 2 hydrogens and 1 oxygen.

• Compounds have properties different from the individual elements that form them.

What is a chemical reaction? What are reactants and products? What does it mean for a reaction to be reversible?

Chemical Reaction

• A process where atoms in compounds rearrange.

• New compounds form by breaking old chemical bonds and making new ones.

• Matter is not created or destroyed (law of conservation of mass).

Reactants vs. ProductsReactants

• The substances you start with.

• Found on the left side of a chemical equation.

• Example from your notes:

  • 12 H₂O + 6 CO₂

Products

• The substances you end with after the reaction.

• Found on the right side of the equation.

• Example from your notes:

  • 6 O₂ + C₆H₁₂O₆ + 6 H₂O

Reversible Reactions

• Some reactions can go forward or backward.

• Products can revert back into reactants.

• Represented by a double arrow (⇌).

How are electrons arranged in an atom? How does this arrangement explain how atoms bond?

Electron Arrangement

• Electrons are arranged in shells around the nucleus.

• Shells can accept, give up, or share electrons until they are full.

• Most common elements follow the octet rule:

  • A full outer (valence) shell = 8 electrons.

Why Electron Arrangement Matters for BondingAtoms bond to fill their valence shells

• Atoms are more stable when their outer shell is full.

• If an atom’s valence shell is not full, it becomes reactive.

Two ways atoms fill their valence shells:

1. Ionic bonding

   • Electrons are permanently transferred from one atom to another.

   • Creates charged ions that attract each other.

2. Covalent bonding

   • Electrons are shared between atoms.

   • Sharing can be equal or unequal depending on electronegativity.

What is an ion? How do ionic bonds form? What is a salt?

Ion

• An atom or molecule with an electrical charge.

• Charge happens because of a transfer of electrons (gain or loss).

  • Losing electrons → positive ion (cation)

  • Gaining electrons → negative ion (anion)

Examples from your notes:

• Neutral sodium atom (Na):

  • 11 protons, 11 electrons → not stable

• Sodium ion (Na⁺):

  • 11 protons, 10 electrons → stable

• Neutral chlorine atom (Cl):

  • 17 protons, 17 electrons → not stable

• Chloride ion (Cl⁻):

  • 17 protons, 18 electrons → stable

Ionic Bonding

• One atom loses electrons, the other gains electrons.

• Opposite charges attract, forming the bond.

• These bonds are relatively easy to break because the attraction is the only thing holding them together.

Salt

• Any ionic compound.

• Examples: NaCl, KCl, NaBr.

• Many form crystal structures.

Compare and contrast the characteristics of polar covalent and nonpolar covalent chemical bonds. How does each type of bond form? Be able to recognize examples of compounds with each type of bond.

Covalent Bonds

What is a covalent bond?

A covalent bond forms when two atoms share electrons so both can fill their valence (outer) electron shells and become more stable.

Why atoms share electrons

• Atoms want full valence shells.

• If they can’t achieve this by gaining or losing electrons (ionic bonding), they may share electrons instead.

• Shared electrons count for both atoms.

Types of Covalent BondsSingle Bond

• 1 pair of electrons shared

• Example: H–H

Double Bond

• 2 pairs of electrons shared

• Example: O=O

Triple Bond

• 3 pairs of electrons shared

• Example: N≡N

• Strongest and shortest of the three

Polar vs. Nonpolar Covalent BondsNonpolar Covalent Bond

• Electrons are shared equally

• No charge separation

• Example: H₂, O₂, CH₄

Polar Covalent Bond

• Electrons are shared unequally

• One atom pulls electrons more strongly (higher electronegativity)

• Creates slight charges:

  • δ⁺ (slightly positive)

  • δ⁻ (slightly negative)

Example: Water (H₂O)

• Oxygen pulls electrons more strongly than hydrogen

• Oxygen becomes δ⁻

• Hydrogens become δ⁺

• This polarity gives water many special properties

What are hydrogen bonds in water? Describe the following characteristics of water: polarity of water molecules, cohesion, temperature-stabilizing effects, and solvent properties. Why does water have each characteristic and how is each important in living systems?

Hydrogen bonds are weak attractions between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of a neighboring water molecule. Four important properties that arise from hydrogen bonding are: cohesion, temperature stabilization (high heat capacity), solvent ability (universal solvent for polar molecules), and surface tension.

What is the pH scale and how do you classify acids, bases, and neutral solutions?

pH measures the concentration of hydrogen ions [H+] in a solution. The pH scale runs from 0 to 14: values less than 7 are acidic (higher [H+]), 7 is neutral, and values greater than 7 are basic (lower [H+]).

Compare acids and bases and explain how buffers work. Give an example of a biological buffer.

Acids donate H+ to solutions (increase [H+]); bases reduce [H+] often by providing OH− or accepting H+. Buffers resist pH change by accepting H+ when the solution becomes too acidic and donating H+ when it becomes too basic. A common biological buffer is blood plasma (bicarbonate buffer system).

What defines an organic compound and why are there so many types? What is a functional group?

An organic compound contains carbon (usually with hydrogen and other elements). Carbon’s ability to form four covalent bonds, to make chains, branches, rings, and to form single/double bonds leads to huge structural diversity. A functional group is a cluster of atoms attached to a carbon skeleton that confers specific chemical properties (e.g., hydroxyl, carboxyl, amino, phosphate, methyl).

List the four classes of large biological molecules and define polymer and monomer.

The four classes are proteins, carbohydrates, lipids, and nucleic acids. A monomer is a small building‑block molecule; a polymer is a large molecule made by linking many monomers. (Note: lipids are not true polymers, but glycerol + fatty acids are useful subunits to consider.)

What are dehydration and hydrolysis reactions? What are redox (electron transfer) reactions in cells?

Dehydration (condensation) reactions join monomers into polymers by removing water; enzymes catalyze bond formation. Hydrolysis breaks polymers into monomers by adding water; enzymes catalyze bond cleavage. Redox (electron transfer) reactions move electrons between molecules; as electrons transfer, small amounts of energy are released and cells harness that energy (often to make ATP).

Describe proteins: their monomers, major functions, what a polypeptide is, and the four aspects of protein shape. What is denaturation?

Proteins are polymers of amino acids (20 common amino acids). Major functions include structural support, enzymes (catalysts), transport, antibodies, and some hormones. A polypeptide is a chain of amino acids; proteins consist of one or more polypeptides folded into a functional shape. The four aspects of protein shape are: (1) primary sequence (amino acid order), (2) secondary structure (coils/β‑sheets), (3) tertiary folding (3D bends/folds), and (4) quaternary structure (multiple polypeptides assembled). Denaturation is the loss of a protein’s native shape (and function) due to changes in pH, temperature, or salinity; often irreversible (e.g., cooking an egg).

What are carbohydrates and what distinguishes monosaccharides, disaccharides, and polysaccharides? Give examples and roles.

Carbohydrates are carbon‑based molecules used for energy and structure. Monosaccharides are single sugars (e.g., glucose, fructose, ribose). Disaccharides are two monosaccharides joined (e.g., maltose, sucrose, lactose). Polysaccharides are long chains (e.g., starch — plant energy storage; cellulose — plant cell walls; glycogen — animal energy storage).

Describe lipids and the specific characteristics of fats (triglycerides), phospholipids, and steroids. What makes fatty acids saturated vs. unsaturated?

Lipids are hydrophobic molecules used for energy storage, membrane structure, and signaling (hormones). Fats (triglycerides) are glycerol + three fatty acids; long‑term energy storage. Phospholipids have hydrophilic phosphate heads and hydrophobic fatty‑acid tails and form bilayers (cell membranes). Steroids (e.g., cholesterol) are ringed lipids used in membranes and as hormone precursors. Saturated fatty acids have the maximum number of hydrogens (no double bonds) and are typically solid at room temperature; unsaturated have one or more double bonds (fewer H) and are typically liquid.

What are nucleotides and nucleic acids? What are adenosine phosphates and coenzymes? Name the two nucleic acids in cells.

A nucleotide consists of a nitrogenous base, a five‑carbon sugar, and one or more phosphate groups. Nucleic acids (polymers of nucleotides) store and transmit genetic information (DNA and RNA). Adenosine phosphates (e.g., ATP) are single‑nucleotide molecules that carry energy. Coenzymes (e.g., NAD

Define and differentiate: atomic number, mass number, atomic weight, isotope, and radioactive isotope.

• Atomic number = number of protons in an atom (defines the element).

• Mass number = total number of protons + neutrons in a specific nucleus.

• Atomic weight (atomic mass) = weighted average mass of an element’s isotopes (reported on periodic table).

• Isotope = atoms of the same element with different numbers of neutrons.

• Radioactive isotope = an isotope whose nucleus is unstable and decays, emitting radiation.

List the nitrogenous bases found in DNA and RNA.

• DNA bases: adenine (A), thymine (T), cytosine (C), guanine (G).

• RNA bases: adenine (A), uracil (U), cytosine (C), guanine (G).