AP Biology: Chapter 2/3 Flashcards

Key Concepts in Biology

• Hydrophobic substances, like vegetable oil, are nonpolar and repel water.
• Waxes are classified as hydrophobic molecules, contributing to waterproofing in various organisms.
• An atom is the smallest unit of an element, retaining the element's properties.
• Atoms of a particular element have identical numbers of protons in their nuclei, defining the element.
• Different atoms comprise various molecules, differentiated by varying numbers of subatomic particles.
• Neutrons and protons have equal mass, approximately 1 Dalton (also known as atomic mass unit or amu).
• Buffers stabilize pH levels by donating H+ when depleted and accepting H+ when in excess.
• The mass number of an element approximates the sum of its protons and neutrons.

Water and Its Properties

• Water molecules consist of two hydrogen atoms bonded to one oxygen atom via polar covalent bonds.
• The slight charges of water molecules lead to hydrogen bonds, a key reason for interactions between water molecules.
• A solution with 10^-7 moles of hydroxyl ions (OH-) per liter is neutral, indicating equal concentrations of H+ and OH-.
• For an atom with 16 neutrons, 15 protons, and 15 electrons, the approximate mass is 51 Daltons.
• Polar covalent bonds are likely when one of the atoms is significantly more electronegative.
• Many mammals regulate body temperature through sweating, a process involving the heat absorption when hydrogen bonds break.
• Atoms with eight electrons in their outer shell are considered stable, chemically inactive, or inert.

Chemical Interactions and Solutions

• A buffer system maintains consistent pH despite the addition of acids or bases.
• Atomic number indicates the number of protons in an atom's nucleus, which determines the element's identity.
• Blood interacting with respiring cells typically experiences a slight decrease in pH due to metabolic processes.
• Ice floats on water because hydrogen bonds create a stable structure that keeps ice molecules farther apart than those in liquid water.
• Pure, freshly distilled water has equal concentrations of H+ and OH-, resulting in a neutral pH of 7.
• Weak interactions such as ionic bonds, van der Waals interactions, and hydrogen bonds play crucial roles in molecular structure and function.

Elements and Nature

• Four elements—carbon, hydrogen, nitrogen, and oxygen—make up approximately 96% of living matter.
• The high surface tension of water is illustrated by the behavior of water striders, allowing them to walk on water.
• Water's densest point occurs at 4 degrees Celsius, an unusual property that influences aquatic ecosystems.
• Covalent bonds involve the sharing of outer-shell electrons, essential for forming stable molecules.
• Mixing two solutions with different pHs leads to a new pH that is the average of the two.
• Cohesiveness in water molecules arises from hydrogen bonding, enabling phenomena such as surface tension and capillarity.

Test your knowledge of key concepts from AP Biology Chapters 2 and 3 with this set of flashcards. Explore essential terms like hydrophobic substances, atoms, and their properties. Perfect for quick review or study sessions!