Experimental Design & Life
Scientists observe that a mysterious blob moves toward light. Which official characteristic of life does this observation support?
Responds to environmental stimuli
Two molecules have the same molecular formula but different structures. What are they called?
Isomers
Which carbohydrate is used for energy storage in animals, and which is used for energy storage in plants?
Glycogen in animals; starch in plants.
A substance moves from an area of high concentration to an area of low concentration. Is it moving up or down its concentration gradient?
Down its concentration gradient.
Name the four structures/components that are found in all types of cells, including prokaryotes.
Cell/plasma membrane, cytosol, ribosomes, DNA.
Scientists observe that a mysterious blob remains at 17°C both on the moon and in a laboratory on Earth. Which characteristic of life could this support?
Maintaining homeostasis / stable internal conditions
What two structural features does the review packet use to define an organic compound?
Contains carbon and has at least one C–H bond.
Glucose and fructose combine to form sucrose. What process joins them, and what molecule is removed during that process?
Dehydration synthesis/condensation; water is removed.
A molecule moves from high concentration to low concentration through a membrane protein without ATP. Name the transport process.
Facilitated diffusion.
Which organelle manufactures lipids and also stores calcium ions?
Smooth ER
Students test orange juice, apple juice, water, pineapple juice, and mango juice and measure the amount of vitamin C in each. Identify both the independent and dependent variables.
Independent: type of liquid. Dependent: amount of vitamin C measured.
A molecule contains only carbon-hydrogen bonds. Predict whether it is hydrophilic or hydrophobic and explain why.
Hydrophobic; C and H have similar electronegativity, so the bonds are nonpolar, making the molecule nonpolar.
Humans can digest starch but cannot digest cellulose for energy. Explain this difference using the type of glycosidic linkage and enzymes.
Starch has alpha linkages; cellulose has beta linkages. Humans do not make the correct enzyme to break cellulose’s beta linkages.
Compare simple diffusion, facilitated diffusion, and active transport in terms of whether each requires a transport protein and whether each requires ATP.
Diffusion: no protein, no ATP. Facilitated diffusion: protein, no ATP. Active transport: protein and ATP.
A cell has a cell wall, chloroplasts, and a large central vacuole. What type of cell is it, and which three structures support your conclusion?
Plant cell; cell wall, chloroplasts, central vacuole.
In an experiment measuring vitamin C in different liquids, orange juice is included because it is already known to contain vitamin C. What kind of control is it, and why is that useful?
Positive control; it should produce a positive result, showing that the procedure can detect vitamin C.
A large molecule is dismantled into smaller molecules by adding water. Name the process. Then name the opposite process that builds larger molecules.
Hydrolysis; dehydration synthesis/condensation reaction.
Compare saturated and unsaturated triglycerides in terms of carbon-carbon bonds, chain shape, physical state at room temperature, and usual source.
Saturated: all single bonds, straight, usually solid, usually animal sources. Unsaturated: one or more double bonds, bent, usually liquid, usually plants/fish.
A cell is placed in a solution that has a higher solute concentration outside the cell than inside. Identify the outside solution as hypertonic or hypotonic, predict the direction of water movement, and predict what happens to cell mass.
Hypertonic; water moves out of the cell by osmosis; cell mass decreases.
Explain how animal cells and plant cells use different strategies to maintain membrane fluidity when temperature changes.
Animals use cholesterol. Plants change the ratio of saturated to unsaturated phospholipids.
Students compare vitamin C levels in several juices. Name two variables that should be kept constant, identify what belongs on the X-axis, and identify what belongs on the Y-axis.
Constants: e.g. same volume/amount of juice and same freshness. X-axis: type of liquid. Y-axis: amount of vitamin C measured.
A fatty-acid-like molecule contains a carbon-carbon double bond. Explain how you would classify it as saturated or unsaturated, and explain what a cis double bond does to its overall shape.
Unsaturated; a cis double bond produces a bend in the chain.
A protein is boiled and can no longer perform its original function. Explain the entire chain of events from heat to loss of function.
Heat disrupts weak interactions between amino-acid R groups → protein unravels/loses its 3D shape → because shape determines function, the protein loses its function.
Diffusion and facilitated diffusion reach equilibrium. Explain whether molecular movement stops and what “equilibrium” actually means.
Movement does not stop. Molecules continue moving in both directions, but the concentrations are equal, so there is no net change.
At low temperatures, explain what cholesterol does in an animal membrane and what change plants make to their membrane lipids. Then explain why both changes help maintain fluidity.
Cholesterol prevents phospholipids from packing too closely. Plants use more unsaturated phospholipids, whose bends reduce close packing.