Problem 13 - Biology Today and Tomorrow with Physiology

Question

Match the terms with their most suitable description. $$ \text {hydrophilic } \quad \quad \text {a. protons \(>\) electrons} $$ $$ \text {atomic number } \quad \quad \text {b. number of protons in nucleus} $$ $$ \text {hydrogen bonds } \quad \quad \text {c. polar; dissolves easily in water} $$ $$ \text {positive charge } \quad \quad \text {d. collectively strong} $$ $$ \text {negative charge} \quad \quad \text {e. protons \(<\) electrons} $$ $$ \text {temperature } \quad \quad \text {f. measure of molecular motion} $$ $$ \text {\(\mathrm{pH}\) } \quad \quad \text { g. decays} $$ $$ \text {covalent bond} \quad \quad \text {h. electron sharing} $$ $$ \text {radioisotope } \quad \quad \text {i. reflects \(\mathrm{H}^{+}\) concentration} $$

Step-by-Step Solution

Answer

1. c, 2. b, 3. d, 4. a, 5. e, 6. f, 7. i, 8. h, 9. g.

Step 1: Match Hydrophilic

Hydrophilic refers to substances that are polar and dissolve easily in water. Therefore, the correct match is: hydrophilic - c. polar; dissolves easily in water.

Step 2: Match Atomic Number

The atomic number of an element is defined as the number of protons present in the nucleus of its atom. This gives us: atomic number - b. number of protons in nucleus.

Step 3: Match Hydrogen Bonds

Hydrogen bonds are individually weak, but collectively they can be quite strong and contribute significantly to the structure and properties of water and other compounds. Hence: hydrogen bonds - d. collectively strong.

Step 4: Match Positive Charge

A positive charge occurs when an atom has more protons than electrons. Therefore: positive charge - a. protons > electrons.

Step 5: Match Negative Charge

A negative charge happens when an atom has more electrons than protons. Thus, the match is: negative charge - e. protons < electrons.

Step 6: Match Temperature

Temperature measures the average molecular motion in a substance. Therefore, the corresponding description is: temperature - f. measure of molecular motion.

Step 7: Match pH

The pH scale measures the concentration of hydrogen ions ( H^{+} ), indicating how acidic or basic a solution is. Thus, the match is: pH - i. reflects ( H^{+} ) concentration.

Step 8: Match Covalent Bond

A covalent bond is formed by the sharing of electron pairs between atoms. Thus, it matches with: covalent bond - h. electron sharing.

Step 9: Match Radioisotope

Radioisotopes are isotopes that decay over time, emitting radiation. Hence, the appropriate match is: radioisotope - g. decays.

Key Concepts

Atomic Structure

The atomic structure is the foundation of understanding chemistry. At an atom's core lies the nucleus, which contains protons and neutrons. Protons are positively charged particles, and their number determines the atomic number of the element. This atomic number is essential because it identifies the element and defines its position on the periodic table. Each element has a unique atomic number, reflecting a different number of protons in its nucleus. Around the nucleus, electrons - negatively charged particles - move in orbitals, creating a space known as the electron cloud. When discussing atomic charges, it's important to note that:

• A neutral atom has an equal number of protons and electrons.
• An atom with more protons than electrons carries a positive charge, known as a cation.
• An atom with more electrons than protons carries a negative charge, called an anion.

Understanding atomic structure is crucial for exploring how atoms interact and bond with each other to form molecules, laying the groundwork for chemical reactions.

Chemical Bonds

Chemical bonds are the forces that hold atoms together in molecules. There are several types of bonds, with covalent and ionic being the most common.

• Covalent Bonds: These bonds form when two atoms share one or more pairs of electrons, creating a stable attraction between them. This type of bond is prevalent in organic molecules, like carbohydrates, proteins, and DNA.
• Ionic Bonds: Ionic bonds occur when an atom donates one or more electrons to another atom, resulting in positively and negatively charged ions that attract each other. This often happens between metals and non-metals and is typical in compounds like sodium chloride (table salt).
• Hydrogen Bonds: Although not as strong as covalent or ionic bonds, hydrogen bonds are crucial in many biological processes and properties of water. These bonds occur when a hydrogen atom, covalently bonded to a more electronegative atom like oxygen or nitrogen, experiences an attraction to another electronegative atom from a different molecule.

Chemical bonds determine the structure and properties of substances, influencing how they interact in chemical reactions.

pH Scale

The pH scale is a numerical representation that indicates how acidic or basic a solution is. It ranges from 0 to 14, with each number representing the potential of hydrogen ions \( \( H^{+} \) \) concentration. The scale is logarithmic, meaning each whole number change on the scale represents a tenfold change in \( \( H^{+} \) \) ion concentration.

• Acidic Solutions: These have a pH less than 7, indicating a higher concentration of \( \( H^{+} \) \) ions. Common examples include lemon juice and vinegar.
• Neutral Solutions: These have a pH of exactly 7, which means the concentration of \( \( H^{+} \) \) ions is equal to hydroxide ions \( \( OH^{-} \) \). Pure water is a prime example.
• Basic (or Alkaline) Solutions: These have a pH greater than 7, indicating a lower concentration of \( \( H^{+} \) \) ions. Many household cleaning products, like bleach, are basic.

Understanding the pH scale is essential for many scientific fields, including chemistry, biology, medicine, and environmental science, as it affects chemical behavior and biological processes.

Radioisotopes

Radioisotopes, or radioactive isotopes, are versions of elements with unstable nuclei that release energy in the form of radiation as they decay into more stable forms. This process often involves the release of alpha, beta, or gamma radiation. Some important uses and characteristics of radioisotopes include:

• Medical Applications: Radioisotopes are integral in medical diagnostics and treatment, such as in imaging techniques (e.g., PET scans) and in treating cancers through targeted radiation therapy.
• Carbon Dating: Isotopes like Carbon-14 are used to date ancient artifacts and geological samples by measuring the rate of decay and detecting the remaining isotopic content.
• Industrial Uses: Radioisotopes play a role in industrial applications, such as tracing the movement of materials, checking weld conditions, and in sterilization processes.

While radioisotopes provide numerous benefits, they must be handled carefully due to their radioactive nature, which can pose health and environmental risks if not properly managed.