PSL 250 FINAL EXAM QUESTIONS WITH VERIFIED ANSWERS LATEST
UPDATE 2026
Homeostasis - Answers The ability of an organism to maintain a relatively constant
internal environment despite changing internal or external conditions.
Components of Homeostatic System - Answers Stimulus -> Receptor -> Control
Center -> Effector
Negative Feedback - Answers The resulting action will be in the opposite direction of
the stimulus (most common).
Positive Feedback - Answers A homeostatic mechanism where the response enhances
or amplifies the original stimulus, moving the system further away from the starting
point.
Stimulus - Answers A change occurs in the body.
Receptor - Answers Detects the change.
Control Center - Answers Processes the information and signals the effectors.
Effector - Answers Enhances the original change.
Amplification - Answers The response strengthens until a goal or endpoint is
reached.
Termination - Answers The loop ends once the goal is achieved.
Dissociate - Answers When a molecule splits into smaller particles (ions) in solution.
Anion - Answers A negatively charged ion (gained electrons).
Cation - Answers A positively charged ion (lost electrons).
Solvent - Answers The substance that does the dissolving.
Solute - Answers The substance that is dissolved.
Solution - Answers A uniform mixture of solute and solvent.
Acid - Answers A substance that releases hydrogen ions (H⁺) in solution.
Base - Answers A substance that accepts hydrogen ions or releases hydroxide ions
(OH⁻).
pH - Answers A scale (0-14) measuring the concentration of H⁺ ions in a solution.
pH Scale - Answers 0 is acidic and 14 is basic.
ATP - Answers Immediate energy source.
Energy Duration of ATP - Answers 2-3 seconds.
Phosphocreatine - Answers Rapidly regenerates ATP.
, Energy Duration of Phosphocreatine - Answers ~ 10 seconds.
Glucose - Answers Used in glycolysis/ respiration.
Energy Duration of Glucose - Answers Minutes to hours.
Glycogen - Answers Stored glucose for energy.
Energy Duration of Glycogen - Answers Up to several hours.
Fatty Acids - Answers Long-term energy.
Energy Duration of Fatty Acids - Answers Hours.
H+ Gradient - Answers Used to produce ATP by flowing back through the enzyme
ATP synthase.
ATP Synthase - Answers The specific enzyme that converts ADP and phosphate into
ATP using energy from the H+ gradient.
Passive transport - Answers Does not require cellular energy; substances move down
concentration gradient.
Simple diffusion - Answers No transport protein required for movement; small
nonpolar molecules.
Facilitated diffusion - Answers Transport protein required for movement of ions or
polar molecules.
Channel mediated diffusion - Answers Ion moves through a channel down its
concentration gradient.
Carrier mediated diffusion - Answers Small polar molecules moved by a carrier
protein that changes shape to transport them across the plasma membrane.
Active transport - Answers Requires expenditure of cellular energy; involves the
movement of a substance up its concentration gradient.
Primary transport - Answers Energy source is ATP.
Secondary transport - Answers Energy source is the movement of another substance.
Regeneration - Answers The replacement of damaged or dead cells with the same
type of cells.
Fibrosis - Answers The replacement of damaged tissue with scar tissue (dense
connective tissue, mainly collagen).
Skin color - Answers Color from hemoglobin, melanin, and carotene.
Hemoglobin - Answers Oxygen-binding protein in red blood cells.
Motor unit - Answers An alpha motor neuron and all muscle fibers it innervates.
Small motor units - Answers Less than 5 muscle fibers; precise movements; found in
eyes and hands.
UPDATE 2026
Homeostasis - Answers The ability of an organism to maintain a relatively constant
internal environment despite changing internal or external conditions.
Components of Homeostatic System - Answers Stimulus -> Receptor -> Control
Center -> Effector
Negative Feedback - Answers The resulting action will be in the opposite direction of
the stimulus (most common).
Positive Feedback - Answers A homeostatic mechanism where the response enhances
or amplifies the original stimulus, moving the system further away from the starting
point.
Stimulus - Answers A change occurs in the body.
Receptor - Answers Detects the change.
Control Center - Answers Processes the information and signals the effectors.
Effector - Answers Enhances the original change.
Amplification - Answers The response strengthens until a goal or endpoint is
reached.
Termination - Answers The loop ends once the goal is achieved.
Dissociate - Answers When a molecule splits into smaller particles (ions) in solution.
Anion - Answers A negatively charged ion (gained electrons).
Cation - Answers A positively charged ion (lost electrons).
Solvent - Answers The substance that does the dissolving.
Solute - Answers The substance that is dissolved.
Solution - Answers A uniform mixture of solute and solvent.
Acid - Answers A substance that releases hydrogen ions (H⁺) in solution.
Base - Answers A substance that accepts hydrogen ions or releases hydroxide ions
(OH⁻).
pH - Answers A scale (0-14) measuring the concentration of H⁺ ions in a solution.
pH Scale - Answers 0 is acidic and 14 is basic.
ATP - Answers Immediate energy source.
Energy Duration of ATP - Answers 2-3 seconds.
Phosphocreatine - Answers Rapidly regenerates ATP.
, Energy Duration of Phosphocreatine - Answers ~ 10 seconds.
Glucose - Answers Used in glycolysis/ respiration.
Energy Duration of Glucose - Answers Minutes to hours.
Glycogen - Answers Stored glucose for energy.
Energy Duration of Glycogen - Answers Up to several hours.
Fatty Acids - Answers Long-term energy.
Energy Duration of Fatty Acids - Answers Hours.
H+ Gradient - Answers Used to produce ATP by flowing back through the enzyme
ATP synthase.
ATP Synthase - Answers The specific enzyme that converts ADP and phosphate into
ATP using energy from the H+ gradient.
Passive transport - Answers Does not require cellular energy; substances move down
concentration gradient.
Simple diffusion - Answers No transport protein required for movement; small
nonpolar molecules.
Facilitated diffusion - Answers Transport protein required for movement of ions or
polar molecules.
Channel mediated diffusion - Answers Ion moves through a channel down its
concentration gradient.
Carrier mediated diffusion - Answers Small polar molecules moved by a carrier
protein that changes shape to transport them across the plasma membrane.
Active transport - Answers Requires expenditure of cellular energy; involves the
movement of a substance up its concentration gradient.
Primary transport - Answers Energy source is ATP.
Secondary transport - Answers Energy source is the movement of another substance.
Regeneration - Answers The replacement of damaged or dead cells with the same
type of cells.
Fibrosis - Answers The replacement of damaged tissue with scar tissue (dense
connective tissue, mainly collagen).
Skin color - Answers Color from hemoglobin, melanin, and carotene.
Hemoglobin - Answers Oxygen-binding protein in red blood cells.
Motor unit - Answers An alpha motor neuron and all muscle fibers it innervates.
Small motor units - Answers Less than 5 muscle fibers; precise movements; found in
eyes and hands.
