bio chapters 1-4

What are the characteristics of life?

Living organisms are organized, use energy, maintain homeostasis, grow and develop, reproduce, respond to stimuli, adapt/evolve over generations, and contain genetic information. These characteristics distinguish living systems from nonliving matter.

What is biological organization?

The hierarchical arrangement of biological structures from smaller to larger levels. Each level can have properties that emerge from interactions among its components.

What is the order of biological organization from smallest to largest?

Cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.

What is a cell?

The smallest unit of life that can perform all necessary functions of life. Example: a muscle cell or bacterium.

What is a tissue?

A group of similar cells that work together to perform a specific function. Example: muscle tissue.

What is an organ?

A structure made of multiple tissues working together to perform a specific function. Example: the heart.

What is an organ system?

A group of organs that work together to perform major functions of an organism. Example: the digestive system.

What is an organism?

An individual living thing. Example: one human, oak tree, or bacterium.

What is a population?

All individuals of the same species living in the same area at the same time. Example: all the deer in a forest.

What is a community?

All the populations of different species living and interacting in the same area. Example: deer, trees, fungi, bacteria, and birds in a forest.

What is an ecosystem?

A community of organisms plus the nonliving environment with which they interact. Example: a forest community plus soil, water, sunlight, and temperature.

What is the biosphere?

All regions of Earth where life exists, including land, water, and parts of the atmosphere.

What is an atom?

The smallest unit of an element that retains the chemical properties of that element. It consists of protons, neutrons, and electrons.

What is a proton?

A positively charged subatomic particle found in the nucleus of an atom.

What is an electron?

A negatively charged subatomic particle found outside the nucleus. Electrons, especially valence electrons, are important in chemical bonding.

What is a valence shell?

The outermost electron shell of an atom. Its electrons are involved in chemical bonding.

What is valence?

The typical number of covalent bonds an atom can form based on its available valence electrons.

What are the typical valences of H, O, N, and C?

Hydrogen = 1 bond; Oxygen = 2 bonds; Nitrogen = 3 bonds; Carbon = 4 bonds.

What is a chemical bond?

An attractive interaction that holds atoms together in a molecule or compound. Important biological interactions include covalent bonds, ionic attractions, and hydrogen bonding.

What is a covalent bond?

A chemical bond formed when atoms share electrons. Covalent bonds can be nonpolar or polar depending on how equally the electrons are shared.

What is a polar covalent bond?

A covalent bond in which electrons are shared unequally because one atom attracts the electrons more strongly. Example: the O-H bonds in water.

What is a nonpolar covalent bond?

A covalent bond in which electrons are shared relatively equally between atoms with similar electronegativities.

What is an ionic bond?

An attraction between oppositely charged ions that results after electrons are transferred from one atom to another. Example: Na+ and Cl- in sodium chloride.

What is an ion?

An atom or molecule with a net electrical charge because it has gained or lost electrons.

What does it mean for an atom to disassociate?

For a compound or molecule to separate into smaller particles, often ions, when placed in a solution. For example, NaCl can dissociate into Na+ and Cl- in water.

What is a hydrogen bond?

A weak intermolecular force between a partially positive hydrogen and an electronegative atom, usually oxygen or nitrogen, in another molecule. Hydrogen bonding is especially important between water molecules.

Why is a hydrogen bond technically an intermolecular force rather than a true chemical bond?

It is an attraction between molecules rather than a strong covalent or ionic bond holding atoms together within a molecule.

Why are covalent bonds extremely common in biological molecules?

Carbon and other biological elements can share electrons through covalent bonds, allowing organisms to build stable molecules with complex structures, chains, branches, and rings.

What is electronegativity?

The tendency of an atom to attract shared electrons toward itself in a covalent bond.

What is water's molecular formula?

H2O.

Why is water a polar molecule?

Oxygen is more electronegative than hydrogen, so it pulls shared electrons closer to itself. This gives oxygen a partial negative charge and hydrogen partial positive charges.

What is a partial charge?

A slight electrical charge resulting from unequal sharing of electrons in a polar covalent bond. It is represented as δ+ or δ-.

What is cohesion?

The attraction between molecules of the same substance. Water molecules are cohesive because hydrogen bonds cause them to attract one another.

What is adhesion?

The attraction between molecules of different substances. Water can adhere to surfaces such as the walls of plant xylem.

What is surface tension?

The resistance of a liquid's surface to being stretched or broken. Water has high surface tension because of strong cohesion caused by hydrogen bonding.

Why does water have high cohesion?

Water is polar, so neighboring water molecules form hydrogen bonds. These attractions cause water molecules to stick together.

Why is cohesion important in plants?

Cohesion helps maintain a continuous column of water in xylem. As water evaporates from leaves, cohesive forces help pull other water molecules upward.

Why is adhesion important in plants?

Water adheres to the walls of narrow xylem vessels, contributing to capillary action and helping water move upward through plants.

What is specific heat?

The amount of heat energy required to raise the temperature of a substance by a certain amount.

What does high specific heat mean?

A substance requires a large amount of energy to significantly increase its temperature. Water has a high specific heat because energy is needed to disrupt hydrogen-bond interactions.

Why is water's high specific heat biologically important?

It helps organisms and aquatic environments resist rapid temperature changes, making internal and environmental temperatures more stable.

What is heat of vaporization?

The amount of energy required to convert a liquid into a gas.

Why does water have a high heat of vaporization?

Many hydrogen bonds must be disrupted for water molecules to escape into the gas phase, requiring substantial energy.

What is evaporative cooling?

Cooling that occurs when high-energy water molecules evaporate from a surface, carrying heat energy away. Sweating cools the body through evaporative cooling.

Why is ice less dense than liquid water?

Hydrogen bonds arrange water molecules into an open structure when water freezes, spacing molecules farther apart than in liquid water.

Why does ice float?

Ice is less dense than liquid water, so it floats.

Why is floating ice important for aquatic life?

Floating ice forms an insulating layer on the surface of water, slowing heat loss and allowing liquid water below to remain habitable for aquatic organisms.

What is a solvent?

The substance that dissolves another substance to form a solution. Water is the major biological solvent.

What is a solute?

The substance that is dissolved in a solution. In salt water, salt is the solute.

What is a solution?

A homogeneous mixture in which a solute is dissolved in a solvent.

Why is water an excellent solvent?

Water is polar, so its partial charges allow it to interact with and surround ions and other polar molecules, helping dissolve them.

What does hydrophilic mean?

"Water-loving." A substance that interacts favorably with water, usually because it is polar or charged.

What does hydrophobic mean?

"Water-fearing." A substance that does not interact favorably with water, usually because it is nonpolar.

What are hydrophobic interactions?

The tendency of nonpolar molecules or regions to cluster together in water because they do not interact favorably with polar water molecules.

What does nonpolar mean?

Having a relatively even distribution of electrical charge with no significant partial positive or negative regions.

Why don't nonpolar molecules dissolve well in water?

Nonpolar molecules cannot form strong favorable interactions with polar water molecules, so they tend to separate from water.

How can water participate in chemical reactions?

Water can be a reactant or product. It is added during hydrolysis to break bonds and removed during dehydration synthesis when molecules are joined.

What is hydrolysis?

A reaction in which water is added to break a covalent bond, often breaking a polymer into smaller molecules.

What is pH?

A logarithmic measure of hydrogen ion concentration in a solution. The equation is pH = -log[H+].

What is an acid?

A substance that increases the concentration of H+ in a solution. Acids have pH values below 7.

What is a base?

A substance that decreases H+ concentration or increases OH- concentration. Bases have pH values above 7.

What is a neutral solution?

A solution in which H+ and OH- concentrations are equal. Pure water is approximately neutral at pH 7 at 25°C.

What happens to H+ concentration as pH decreases?

H+ concentration increases. Lower pH means greater acidity.

What happens to H+ concentration as pH increases?

H+ concentration decreases. Higher pH means lower acidity and greater basicity.

What happens to OH- concentration as pH decreases?

OH- concentration decreases.

What happens to OH- concentration as pH increases?

OH- concentration increases.

What is the pH 10x rule?

Each one-unit change in pH represents a 10-fold change in H+ concentration.

How much more H+ does pH 4 have than pH 5?

pH 4 has 10 times more H+ than pH 5.

How much more H+ does pH 3 have than pH 6?

pH 3 has 1,000 times more H+ because the difference is 3 pH units and 10^3 = 1,000.

How much more H+ does pH 2 have than pH 7?

pH 2 has 100,000 times more H+ because the difference is 5 pH units and 10^5 = 100,000.

What happens to H+ and OH- when a solution becomes more acidic?

H+ increases and OH- decreases.

What happens to H+ and OH- when a solution becomes more basic?

H+ decreases and OH- increases.

What is the main cause of water's emergent properties?

Water's polarity causes hydrogen bonding between water molecules, and these many weak interactions produce large-scale properties such as cohesion, adhesion, high specific heat, and high heat of vaporization.

What is the main structure-to-property relationship for water?

Polar O-H bonds → partial charges → hydrogen bonds between water molecules → emergent properties that support life.

What is organic chemistry?

The study of carbon-containing compounds, especially those with carbon skeletons and carbon-hydrogen bonds.

Why is carbon important to living organisms?

Carbon has four valence electrons and can form four stable covalent bonds, including bonds with other carbon atoms. This allows it to form chains, branches, rings, and diverse biological molecules.

How many covalent bonds does carbon typically form?

4.

How many covalent bonds does hydrogen typically form?

1.

How many covalent bonds does oxygen typically form?

2.

How many covalent bonds does nitrogen typically form?

3.

What is a carbon skeleton?

The arrangement of carbon atoms that forms the basic framework of an organic molecule.

What shapes can carbon skeletons form?

Carbon skeletons can form straight chains, branched chains, rings, and structures containing single, double, or triple bonds.

Why can carbon form such a wide variety of molecules?

Carbon has four valence electrons and can form four covalent bonds. It can bond to itself and many other elements, allowing chains, branches, rings, and multiple bonds.

What are the four major biological macromolecule categories?

Carbohydrates, lipids, proteins, and nucleic acids. All are carbon-based biological molecules.

What is an organic molecule?

A carbon-based molecule associated with biological chemistry, commonly containing carbon-hydrogen bonds and carbon skeletons.

What is an incomplete organic molecule diagram?

A molecular structure in which some bonds or atoms are not shown. You can use typical valences to determine how many bonds an atom needs.

How do you determine missing bonds in an organic molecule?

Identify the atom, count the bonds already present, compare them with its typical valence, and add the number of bonds needed to reach that valence.

How many bonds does a double bond represent?

Two covalent bonds between the same two atoms.

How many bonds does a triple bond represent?

Three covalent bonds between the same two atoms.

What are isomers?

Molecules with the same molecular formula but different structures or arrangements of atoms.

Why are isomers biologically important?

Different structures can produce different shapes, chemical properties, and biological functions even when molecules have the same molecular formula.

What is a structural isomer?

A molecule with the same molecular formula as another molecule but a different covalent connectivity of atoms.

How do structural isomers differ?

The atoms are connected to different atoms or arranged into different carbon skeletons.

What is a cis-trans isomer?

An isomer with the same molecular formula and connectivity but different spatial arrangements around a carbon-carbon double bond.

Why can cis-trans isomers occur around double bonds?

Double bonds restrict rotation, so groups attached to the double-bonded carbons can remain in different spatial arrangements.

What does cis mean?

Groups of interest are located on the same side of a double bond.

What does trans mean?

Groups of interest are located on opposite sides of a double bond.

What is an enantiomer?

One of a pair of non-superimposable mirror-image molecules.

What is a chiral carbon?

A carbon attached to four different groups, allowing two non-superimposable mirror-image arrangements.

Why are enantiomers important in biology?

Biological molecules such as enzymes and receptors have specific three-dimensional shapes, so one enantiomer may interact differently with a biological target than its mirror image.