Nature of Science
Define science in one clear sentence.
Science is the systematic study of the natural world through observation and experimentation to build evidence-based explanations.
List the six elements commonly called the "elements of life."
Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S).
Name the monomer for carbohydrates and give one example.
Monomer: monosaccharide. Example: glucose.
List the three main principles of cell theory.
Define homeostasis in one sentence.
Homeostasis is the maintenance of stable internal conditions within an organism or cell despite changes in the external environment.
Give an example of a hypothesis written in the correct "If..., then..." format about plant growth.
If tomato seedlings receive additional blue light each day, then their leaf surface area will increase compared to seedlings under white light.
Give three biological molecules (by name) that contain some of the 6 elements essential for life.
Glucose (C, H, O), amino acids/proteins (C, H, O, N, sometimes S), DNA (C, H, O, N, P).
Identify the monomer of proteins and list one major function of proteins in cells.
Monomer: amino acids. Function example: enzymes speed up biochemical reactions.
Name three structures that distinguish plant cells from animal cells.
Cell wall (rigid cellulose structure), chloroplasts (site of photosynthesis), and a large central vacuole (for storage and maintaining turgor pressure).
Differentiate between passive and active transport; give one example of each.
Passive transport moves substances down their concentration gradient without energy input (e.g., diffusion of oxygen across a membrane). Active transport moves substances against their concentration gradient and requires energy, usually ATP (e.g., sodium-potassium pump).
Explain the relationship between independent and dependent variables using the hypothesis: "If fertilizer amount increases, then plant height will increase."
The independent variable (IV) is the factor you change intentionally — fertilizer amount. The dependent variable (DV) is what you measure as a response — plant height. Changes in the IV are expected to cause changes in the DV.
List the organization levels from atom to organism in correct order (start with atom).
Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism.
For lipids and nucleic acids, state a common polymer (or type) and a primary biological role for each.
Lipids: triglycerides and phospholipids — primary roles: long-term energy storage (triglycerides) and membrane structure (phospholipids).
Nucleic acids: DNA and RNA — primary role: store and transmit genetic information.
Describe the function of the mitochondrion, ribosome, and Golgi apparatus in one sentence each.
Mitochondrion: produces ATP by cellular respiration to supply the cell with usable energy.
Ribosome: synthesizes proteins by translating mRNA into polypeptide chains.
Golgi apparatus: modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
Explain the difference between hypotonic, isotonic, and hypertonic solutions and predict the movement of water for a cell placed in each.
Hypotonic solution: lower solute concentration outside the cell → water enters the cell, which may swell or lyse (in animal cells).
Isotonic solution: equal solute concentration → no net water movement; cell volume remains stable.
Hypertonic solution: higher solute concentration outside → water leaves the cell, causing it to shrink (crenation in animal cells, plasmolysis in plant cells).
Differentiate between an observation and an inference; provide one example of each about a beaker of bubbling liquid.
Observation: a direct, factual statement about what you perceive. Example: "The liquid in the beaker is bubbling."
Inference: a logical interpretation or explanation of observations. Example: "A gas is being produced because a chemical reaction is occurring."
Explain what makes a molecule polar versus nonpolar and give one biological example of each.
Polar molecules have uneven electron distribution creating partial positive and negative charges (dipoles); they interact well with other polar molecules. Example: water (H2O).
Nonpolar molecules have even electron distribution and no significant partial charges; they do not mix well with polar substances. Example: fatty acids/lipids (hydrocarbon tails).
Compare relative energy storage of carbohydrates, lipids, and proteins — which stores the most energy per gram and why?
Lipids store the most energy per gram because they contain long hydrocarbon chains with many C–H bonds that yield large amounts of energy when broken. Carbohydrates provide quick energy and are more readily mobilized. Proteins are primarily for structure and function; they are used for energy mostly when carbohydrates and lipids are depleted.
Explain how the structure of the phospholipid bilayer (include roles of proteins, lipids, carbohydrates) determines membrane function.
Phospholipids have hydrophilic heads facing the aqueous inside and outside and hydrophobic tails facing inward, forming a semi-permeable barrier that prevents free passage of most polar molecules; membrane proteins provide specific transport channels, carriers, receptors, and enzymatic functions; membrane carbohydrates (attached to proteins or lipids) function in cell recognition and signaling. Together, these components allow selective transport, communication, and structural integrity.
Summarize the phases of the cell cycle (including interphase stages and mitosis).
Interphase: G1 (cell growth and normal functions), S (DNA replication — synthesis of sister chromatids), G2 (growth and preparation for mitosis).
Mitosis: prophase (chromatin condenses, spindle forms), metaphase (chromosomes align in middle of cell), anaphase (sister chromatids separate), telophase (nuclei reform), followed by cytokinesis (division of cytoplasm).
Describe the difference between accuracy and precision, and explain why having both matters when collecting experimental data.
Accuracy = how close measurements are to the true or accepted value. Precision = how consistent or reproducible repeated measurements are. Both matter because precise but inaccurate results are consistently wrong, and accurate but imprecise results are unreliable; ideally data are both accurate and precise to support valid conclusions.
Describe at least three unique properties of water and explain why each is important for living systems.
Cohesion/surface tension — water molecules stick to each other, enabling transport of water in plants and allowing some organisms to move on the surface.
High specific heat — water resists temperature change, buffering organisms and environments against rapid temperature shifts.
Universal solvent (polarity) — water dissolves many polar and ionic substances, allowing transport and chemical reactions to occur in cells.
Explain why proteins are the most diverse macromolecule and name which macromolecule humans do not obtain from food (and where it comes from).
Protein diversity arises from the 20 different amino acids that can be arranged in countless sequences and folded into varied 3D shapes, producing many functions (enzymes, structural proteins, transporters, signaling molecules).
Humans do not obtain functional nucleic acids (DNA/RNA) from food as usable genetic material; cells synthesize nucleic acids from nucleotide building blocks produced or recycled within the body.
Defend the claim that ribosomes are the most essential organelle by naming three other organelles that support ribosome function and explaining the support they provide.
Rough endoplasmic reticulum (RER) — provides a membrane-bound site where ribosomes synthesize proteins destined for secretion or membranes and helps initial folding.
Golgi apparatus — receives proteins from RER, modifies and packages them for transport to their final destinations.
Vesicles — transport newly made proteins from RER to Golgi and from Golgi to other locations (e.g., lysosomes, membrane, extracellular space). These organelles together enable ribosome-produced proteins to be processed, modified, and delivered where needed.
List and briefly describe the six types of transport across cell membranes with one example substance for two of them.
Simple diffusion — movement of small nonpolar molecules down their gradient (example: O2).
Facilitated diffusion — movement of polar or charged molecules through membrane proteins down their gradient (example: glucose via GLUT transporter).
Osmosis — diffusion of water across a selectively permeable membrane through aquaporins or lipid bilayer.
Ion channels — gated or ungated protein channels that allow specific ions to move down their electrochemical gradients (example: Na+ channels).
Active transport/pumps — protein pumps use ATP to move substances against their gradient (example: Na+/K+ ATPase).
Endocytosis/exocytosis — bulk transport of large particles or volumes into (endocytosis) or out of (exocytosis) the cell inside vesicles (example: phagocytosis of bacteria; secretion of neurotransmitters).