Scientific Method
What is the first step in the scientific method where you identify something you want to learn or explain?
Asking a question or making an observation?
If a solution has a pH of 3, is it an acid, base, or neutral?
Acid
What element is found in all organic macromolecules?
Carbon
What would happen if the sequence of amino acids in a protein changed?
The protein’s shape and function could change (e.g., sickle cell anemia).
Water is called a polar molecule. What does that mean?
What is it has an uneven distribution of charge — oxygen is slightly negative, and hydrogen is slightly positive?
In an experiment testing the effect of light on plant growth, what is the independent variable?
Amount of light
What does the pH scale measure?
The concentration of hydrogen ions (H⁺) in a solution
Monomer of carbohydrates
Monosaccharides
Compare the function of DNA and RNA.
DNA stores genetic information; RNA carries and translates it to make proteins.
Why is it important to have a control group in an experiment?
What is to provide a baseline for comparison and ensure that observed changes are due to the independent variable?
A solution with a pH of 4 has how many times more hydrogen ions than a solution with a pH of 6?
100 times more hydrogen ions
What are the main functions of lipids in living organisms?
Long-term energy storage, insulation, and cell membrane structure.
What type of lipid makes up most of the cell membrane?
Phospholipid
A student claims that “plants grow taller because they like sunlight.” Explain why this statement is not scientific and how it could be rewritten as a testable hypothesis.
A testable version would be: If plants are exposed to increased light intensity, then their height will increase compared to plants grown in low light.
Enzymes function best at specific pH levels. What happens to an enzyme if the pH moves too far from its optimum?
denatures, altering the enzyme’s shape and reducing its activity
What type of bond forms between two amino acids?
Peptide Bonds
A researcher finds that an enzyme activity assay produced unexpected results—one sample showed no activity even though conditions were identical. Give two possible sources of error.
Possible errors include pipetting inaccuracies, contamination, temperature fluctuation, or incorrect substrate concentration.
Explain how the bicarbonate buffer system helps maintain blood pH when carbon dioxide levels rise during exercise.
CO₂ combines with water to form carbonic acid (H₂CO₃), which dissociates into H⁺ and bicarbonate (HCO₃⁻). (If pH drops (too acidic), bicarbonate binds H⁺ to form carbonic acid; if pH rises, carbonic acid releases H⁺ — maintaining homeostasis around pH 7.4)
How does the structure of a phospholipid help form the plasma membrane?
It has hydrophilic heads and hydrophobic tails that form a bilayer, separating water inside and outside the cell.