ch 2- Comprehensive Biology: Molecules, Water, and Origins of Life

What are the five characteristics that define life?

The five characteristics are organization, metabolism, homeostasis, growth, and reproduction.

What is the theory of chemical evolution?

inputs of energy led to the formation of complex carbon-containing molecules, resulting in self-replicating molecules and the beginning of biological evolution.

What is an atom?

An atom is the smallest unit of an element, consisting of protons, neutrons, and electrons.

What does the atomic number represent?

The atomic number represents the number of protons in an atom.

What is the atomic number of carbon?

The atomic number of carbon is 6.

What is the difference between atomic mass and atomic weight?

Atomic mass is the total number of protons and neutrons, while atomic weight is the average mass of an element's isotopes relative to hydrogen.

What are isotopes?

Isotopes are atoms of the same element that have different numbers of neutrons, resulting in different atomic masses.

What happens to an atom's charge if it gains or loses an electron?

If an atom gains an electron, it becomes negatively charged (anion); if it loses an electron, it becomes positively charged (cation).

What are valence electrons?

Valence electrons are the electrons in the outermost shell of an atom that determine its reactivity.

How many valence electrons does carbon have?

Carbon has 4 valence electrons.

What type of bond forms when electrons are shared between atoms?

A covalent bond forms when electrons are shared between atoms.

What is an ionic bond?

An ionic bond is formed when one atom donates an electron to another, resulting in oppositely charged ions that attract each other.

What is electronegativity?

Electronegativity is a measure of an atom's ability to attract and hold onto electrons.

What type of bond is formed between sodium (Na) and chlorine (Cl)?

An ionic bond is formed between sodium and chlorine.

What is a hydrogen bond?

A hydrogen bond is a weak non-covalent interaction that occurs between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

What is the hydrophobic effect?

The hydrophobic effect describes how non-polar substances tend to aggregate in aqueous solutions to minimize their exposure to water.

What is the significance of bond length?

Bond length is the distance at which repulsive forces balance attractive forces between two bonded atoms, affecting molecular geometry.

How do single bonds compare to double bonds in terms of properties?

Single bonds are longer and allow for rotation, while double bonds are shorter and more rigid.

What is the role of enzymes in chemical bonds?

Enzymes are required to break strong covalent bonds.

What is the relationship between the number of bonds and the stability of an atom?

Atoms are most stable when their electron shells are filled, which often requires forming bonds with other atoms.

What are three essential properties of water that support life?

Cohesion, adhesion, and resistance to temperature changes.

How do Na+ and Cl- ions interact with water molecules?

They form ionic bonds; Na+ and Cl- attract the partial charges of O and H in water.

What is cohesion in the context of water?

Cohesion is the attraction between like molecules, keeping them associated.

What is adhesion in the context of water?

Adhesion is the interaction between different types of molecules due to electrostatic charges.

Why does water have a high resistance to temperature changes?

Significant increases in temperature are required to break the many hydrogen bonds present in water.

What is the Arrhenius definition of an acid?

An acid is a substance that increases the hydronium (H3O+) ion concentration when dissolved in water.

What is the Arrhenius definition of a base?

A base is a substance that increases hydroxide (OH-) ion concentration when dissolved in water.

What does the pH scale indicate?

The pH scale reveals whether a solution is acidic or basic, with lower pH indicating higher acidity.

How does a buffer function in biological systems?

Buffers minimize pH changes by interacting with added acids or bases to neutralize them.

What is the significance of carbon's four valence electrons?

They allow carbon to form four bonds, leading to diverse molecular structures.

What types of bonds can carbon form?

Carbon can form single, double, and triple bonds.

What are lipids characterized by?

Lipids have common chemical properties but not common structures, including cholesterol and fatty acids.

What effect do unsaturated fats have on lipid structure?

Unsaturated fats have double bonds that kink the chain, resulting in less closely packed lipids.

What are phospholipids?

Phospholipids are lipids that contain a phosphate head, essential for cell membranes.

What is the hypothesis of chemical evolution?

It suggests that life originated on Earth through the polymerization of small organic molecules.

What conditions did Oparin and Haldane propose were necessary for chemical evolution?

Conditions on early Earth that allowed for the production of organic molecules without oxygen.

What was the outcome of Stanley Miller's experiment?

The experiment detected complex organic molecules, supporting the hypothesis that chemical evolution can occur.

Where were organic monomers concentrated for polymerization?

In hydrothermal sea vents, where conditions were suitable for the formation of complex molecules.

What are the four major families of organic molecules in organisms?

Carbohydrates, proteins, lipids, and nucleic acids.

What is the significance of isomers in organic chemistry?

Isomers increase structural diversity, allowing for a variety of functions and properties.

What is the role of buffers in maintaining blood pH?

Buffers interact with acids or bases to maintain a neutral pH of around 7 in blood.

What are the characteristics that define life?

Complexity, ability to change, reproduce, acquire energy, and evolve.

What are Van der Waals forces?

Weak electrostatic attractions that occur between transient charge separations in molecules.