Bio 161: Anatomy and Physiology Exam 1

Correct Answer:

It would dissolve and produce Mg²⁺ and two Cl⁻ ions.

Explanation:

When MgCl₂ dissolves in water, it dissociates completely into its constituent ions due to the polar nature of water molecules. The ionic compound splits into one magnesium ion (Mg²⁺) and two chloride ions (Cl⁻), maintaining electrical neutrality. This process is called dissociation or ionization and is typical of many soluble ionic compounds in aqueous environments.

Why Other Options Are Wrong:

It would not dissolve, and no ions would be produced.

This is incorrect because MgCl₂ is highly soluble in water and readily dissociates into ions. It does not remain intact in solution.

It would dissolve and produce Mg²⁺ and Cl⁻ ions.

While partially correct, this option is incomplete. It ignores the fact that two chloride ions are produced for every one magnesium ion due to the chemical formula MgCl₂.

It would dissolve and produce only Cl⁻ ions.

This is incorrect because both Mg²⁺ and Cl⁻ ions are produced during dissociation. You cannot have only the anion without the cation in a neutral compound.

Correct Answer:

DNA

Explanation:

DNA (deoxyribonucleic acid) is the molecule responsible for storing the genetic instructions used in the development, function, and reproduction of all living organisms. It contains the coded sequences for protein synthesis and is passed from generation to generation. Its double-helix structure allows for replication and long-term information storage.

Why Other Options Are Wrong:

RNA

RNA plays a key role in translating genetic information into proteins, but it does not store genetic information long term. It acts as a messenger and functional molecule.

protein

Proteins are the products of genetic instructions and perform various cellular functions, but they do not contain or store genetic information.

enzymes

Enzymes are specialized proteins that catalyze reactions. They depend on genetic information to be made but do not store that information themselves.

glucose

Glucose is a carbohydrate that stores energy, not genetic information. It plays no role in inheritance or genetic coding.

Correct Answer:

Proximal

Explanation:

Proximal describes a structure that is closer to the trunk or the point of attachment. For example, the shoulder is proximal to the elbow because it is nearer to the trunk. This directional term is commonly used in anatomy to compare relative positions of limbs and appendages.

Why Other Options Are Wrong:

Lateral

Lateral means farther from the midline of the body, toward the sides. It does not indicate closeness to the trunk.

Medial

Medial refers to a position nearer to the midline, not the point of attachment. It describes side-to-side relationships, not attachment points.

Distal

Distal is the opposite of proximal. It means farther away from the trunk or point of attachment, such as the fingers being distal to the wrist.

Correct Answer:

Study of body's structure and location of body parts.

Explanation:

Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. It specifically examines the form, location, and relationships of body parts, such as muscles, bones, and organs. This is different from physiology, which studies function, and pathology, which studies disease-related changes. Understanding anatomy provides the foundation for identifying how the body is organized and how systems interconnect.

Why Other Options Are Wrong:

Study of processes and functions of the body parts. This is incorrect because that definition describes physiology, not anatomy.

Study of structural and functional changes in tissues and organs that lead to disease. This is wrong because this describes pathology, not anatomy.

All of the above. This is inaccurate because anatomy specifically focuses on structure, not function or disease.

Correct Answer:

Axillary

Explanation:

The axillary region refers to the armpit, located at the junction of the upper limb and the trunk. This area is clinically significant because it contains lymph nodes, blood vessels, and nerves that serve the arm. The axillary region serves as a key anatomical landmark for both medical examinations and surgical procedures, making "Axillary" the correct term.

Why Other Options Are Wrong:

Cervical

The cervical region refers to the neck, not the armpit. It includes structures such as the cervical vertebrae and associated muscles. This makes it unrelated to the upper limb junction.

Brachial

The brachial region refers to the upper arm, extending from the shoulder to the elbow. Although close to the armpit, it is not the same region as the axilla.

Lumbar

The lumbar region refers to the lower back, specifically the area between the ribs and pelvis. It has no anatomical connection to the armpit or upper limb junction.

Correct Answer:

B. a molecule and a compound; a molecule

Explanation:

H₂O is both a molecule (because it has covalently bonded atoms) and a compound (because it consists of two different elements: hydrogen and oxygen). H₂ is a molecule because it consists of two hydrogen atoms bonded together, but it is not a compound since both atoms are the same element.

Why Other Options Are Wrong:

A. a compound and an isotope; a molecule

H₂O is not an isotope, and H₂ is not related to isotopes in this context. Isotopes involve atoms of the same element with different numbers of neutrons.

C. an isotope and a molecule; an isotope

Again, neither H₂O nor H₂ involves isotopes here. This answer is factually incorrect in both cases.

D. a molecule and a compound; a compound

H₂ is not a compound—it only contains one element. Therefore, this answer is incorrect.

E. an isotope and a molecule; a molecule

H₂O is not an isotope. This option incorrectly classifies water as an isotope.

Correct Answer:

Receptors detect changes, Control Centers process information, and Effectors produce responses.

Explanation:

In a feedback mechanism, each component has a specific role that ensures homeostasis. Receptors act as sensors, detecting changes in the internal or external environment such as temperature or blood glucose levels. The Control Center, often the brain or endocrine glands, receives this input and interprets the information to determine an appropriate response. Effectors then carry out the action, such as muscles contracting or glands secreting, to restore balance. Together, this system maintains stability in the body.

Why Other Options Are Wrong:

Receptors produce responses, Control Centers detect changes, and Effectors process information. This is incorrect because receptors do not produce responses; their role is detection. The control center does not directly detect changes but instead interprets information from receptors. Effectors also do not process information—they act to create change.

Receptors process information, Control Centers produce responses, and Effectors detect changes. This is wrong because receptors cannot process information; they are sensors. The control center does not produce direct responses; it decides what the response should be. Effectors do not detect changes; their role is to execute actions determined by the control center.

Receptors and Effectors work together to process information while Control Centers detect changes. This is inaccurate because receptors and effectors have distinct roles, not shared processing responsibilities. The control center does not detect changes but processes the information supplied by receptors. This reverses their roles and creates confusion about how homeostasis functions.

Correct Answer:

Simultaneous transport of two substances across a membrane in opposite directions

Explanation:

Countertransport, also known as antiport, is a form of secondary active transport in which two substances move in opposite directions across a membrane. For example, the sodium-calcium exchanger moves sodium ions into the cell while simultaneously moving calcium ions out. This process relies on the gradient of one ion to power the movement of the other against its gradient. Countertransport is crucial for maintaining ionic balance and regulating cellular activities.

Why Other Options Are Wrong:

Transport of substances in the same direction across a membrane. This describes cotransport (symport), not countertransport. In cotransport, both substances move in the same direction, which is the opposite of countertransport.

Movement of substances down their concentration gradient. This describes simple diffusion or facilitated diffusion, not countertransport. Countertransport often moves at least one substance against its concentration gradient, powered by another’s gradient.

Active transport of a single substance across a membrane. This refers to primary active transport, like the sodium-potassium pump, not countertransport. Countertransport specifically involves the simultaneous movement of two substances, not just one.

Correct Answer:

The cell swells and may burst

Explanation:

In a hypotonic solution, the concentration of solutes outside the cell is lower than inside. Water moves into the cell via osmosis, leading to swelling. If too much water enters, the cell can burst—a condition known as lysis. This is particularly important in medical settings, as intravenous solutions must be carefully matched to cellular osmolarity.

Why Other Options Are Wrong:

The cell shrinks and loses water

This would occur in a hypertonic solution, not a hypotonic one. In a hypotonic environment, water enters the cell, not exits.

The cell remains unchanged

Cells only remain unchanged in isotonic solutions, where solute concentrations are equal inside and out. A hypotonic solution causes water movement into the cell.

The cell becomes rigid and stops functioning

While swelling may impair function, rigidity is not a typical result. Cells become rigid from structural changes or cell wall presence—not from osmotic swelling.