Principles of Biology Flashcards

Questions and Answers

What are the four most common chemical elements in living organisms?

Carbon, Nitrogen, Oxygen, Hydrogen

Describe the structure of an atom with respect to the arrangement of protons, neutrons, and electrons.

An atom's center is the nucleus. Protons revolve around the nucleus, electrons are on the outer shells. Electrons are negative, neutrons are neutral, and protons are positive.

Explain the relationship between electron orbitals and energy shells.

The first shell has the lowest energy, the second shell has higher energy, and the third is the highest. There are 2 electrons in the inner shell, 6 in the second, and 8 in the last.

Predict the relative amount of potential energy in electrons that occupy orbitals in different energy shells.

The closest layer to the nucleus can contain 2 electrons, having the least potential energy. The second layer can hold up to 6 and has more potential energy. Signup and view all the answers

Explain the importance of valence electrons and the formation of chemical bonds.

Valence electrons make an atom stable when the outer shell is filled. They often link with electrons of other molecules that need an electron as well. Signup and view all the answers

Explain how covalent bonds, ionic bonds, and hydrogen bonds differ from one another.

Ionic bonds are the attraction of oppositely charged ions. Hydrogen bonds are the attraction between a hydrogen and an electronegative atom. Covalent bonds involve the sharing of electrons. Signup and view all the answers

Explain the difference between polar and nonpolar covalent bonds.

Nonpolar covalent bonds share electrons equally and are hydrophobic. Polar covalent bonds cause electrons to spend more time around one atom’s nucleus. Signup and view all the answers

Describe how a hydrogen bond forms.

Hydrogen bonds form between molecules that share electrons but have partial charges. They are represented by a dotted line and occur between already formed chemical bonds. Signup and view all the answers

List similarities and differences between hydrogen bonds and ionic bonds.

Both have charges, but ionic bonds have complete charges and are strong, while hydrogen bonds have partial charges, are usually weak, but stronger collectively. Signup and view all the answers

Explain how polar covalent bonds and hydrogen bonds contribute to the special properties of water.

The covalent bond in H2O makes oxygen partially charged, resulting in polarity. Hydrogen bonds form between partially charged atoms, contributing to water’s unique properties. Signup and view all the answers

Compare hydrophilic and hydrophobic.

Hydrophilic substances thrive in water, while hydrophobic substances do not mix with water. Signup and view all the answers

Explain the relationships among hydrogen ion concentration, acidity, and the pH scale.

The pH scale ranges from 1 to 14; a lower pH indicates higher hydrogen ion concentration and acidity, while a higher pH indicates lower concentration and basicity. Signup and view all the answers

Study Notes

Common Chemical Elements

Four most common elements in living organisms: Carbon, Nitrogen, Oxygen, Hydrogen.

Structure of an Atom

Atom's nucleus contains protons and neutrons.
Protons are positively charged, neutrons have no charge, and electrons are negatively charged, orbiting around the nucleus.
Electrons reside in outer shells, while protons and neutrons are in the nucleus.

Electron Orbitals and Energy Shells

Energy shells correspond to distance from the nucleus; the first shell is lowest energy, and subsequent shells increase in energy.
First shell holds a maximum of 2 electrons, the second holds 6, and the third holds 8.

Potential Energy in Electrons

Electrons closest to the nucleus (first shell) possess the least potential energy; those in outer shells (second and third) have progressively more.

Valence Electrons and Chemical Bonds

Atoms seek stability by filling their outer electron shell, leading to electron sharing or transfer to form bonds with other elements.

Types of Bonds

Ionic Bonds: Formed by the attraction between oppositely charged ions (cations and anions).
Covalent Bonds: Formed by sharing of electron pairs between atoms; most secure bond type.
Hydrogen Bonds: Weaker attractions between a hydrogen atom and an electronegative atom, important for molecular interactions.

Polar vs. Nonpolar Covalent Bonds

Nonpolar Covalent Bonds: Electrons are shared equally between atoms, typically hydrophobic.
Polar Covalent Bonds: Electrons are shared unequally, creating a dipole; one atom has a partial negative charge and the other a partial positive charge.

Formation of Hydrogen Bonds

Hydrogen bonds are established between polar molecules due to partial charges; represented by dotted lines.
They involve existing covalent bonds and create temporary attractions.

Similarities and Differences: Hydrogen Bonds vs. Ionic Bonds

Both bond types are charge-based; however, ionic bonds have full charges and are strong unless in water, while hydrogen bonds have partial charges and are relatively weak, forming between molecules.

Water's Unique Properties: Covalent and Hydrogen Bonds

Water (H2O) has a polar structure due to uneven electron sharing, with oxygen partially negative and hydrogen partially positive.
Hydrogen bonds form between water molecules and other electronegative atoms (N, O, F), contributing to water's unique properties.

Hydrophilic vs. Hydrophobic

Hydrophilic substances easily dissolve in water, while hydrophobic substances do not mix well with water.

pH Scale and Acidity

pH scale ranges from 1 (acidic) to 14 (basic), with 7 being neutral.
Acidic solutions have higher hydrogen ion concentration and lower pH values (1-6.999), while basic solutions have lower hydrogen ion concentration and higher pH values (8-14).
pH is determined on a logarithmic scale, reflecting a tenfold change with each unit.

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Test your knowledge on the fundamental concepts of biology with these flashcards. Learn about essential chemical elements and atomic structure. Perfect for biology students looking to reinforce their understanding.