Chapter 2 - Chemical Composition of the Body

What is an ion?

An atom that has gained or lost one or more electrons and therefore has an electrical charge.

How does an atom become an ion?

By gaining or losing one or more electrons.

Why are ions electrically charged?

They have an unequal number of protons and electrons.

What does Cl⁻ represent?

A chlorine atom that has gained one electron.

What does Ca²⁺ represent?

A calcium atom that has lost two electrons.

What determines the function of a molecule?

Its structure.

What is a covalent bond?

A bond in which atoms share electrons.

What is an example of a covalent bond?

Methane (CH₄).

What is an ionic bond?

A bond formed by the attraction between oppositely charged ions.

What is an example of an ionic bond?

Sodium chloride (Na⁺Cl⁻).

What is a hydrogen bond?

A weak electrostatic attraction of hydrogen to oxygen or nitrogen.

What is an example of a hydrogen bond?

The attraction between H₂O molecules.

What are van der Waals forces?

Weak local forces of attraction between molecules.

What is an example of van der Waals forces?

Interactions between lipid molecules.

Which is stronger: covalent bonds or van der Waals forces?

Covalent bonds are stronger.

What is polarity?

An unequal distribution of electrical charge in a molecule, causing one area to be slightly positive and another slightly negative.

Why is water a polar molecule?

Shared electrons are closer to the larger oxygen atom, making the oxygen side slightly negative and the hydrogen side slightly positive.

What type of bonds exist within an H₂O molecule?

Covalent O-H bonds.

What type of bonds can form between H₂O molecules?

Hydrogen bonds.

What is a chemical solution?

A mixture consisting of a solvent and one or more solutes.

What is a solvent?

The substance that dissolves the solute.

What is a solute?

The substance that is dissolved in a solvent.

What is chemical concentration?

The amount of solute present in a given volume of solvent.

What is molecular weight (MW)?

The total mass of all atoms in a molecule, expressed in grams per mole.

What is a 1-molar (1 M) solution?

One mole of a compound dissolved in enough solvent to make 1 liter of solution.

How much glucose is needed to make 1 M glucose?

180 g of glucose in 1 L of water.

What is the molecular weight of glucose (C₆H₁₂O₆)?

180 g/mol.

What does "like dissolves like" mean?

Polar compounds dissolve in polar solvents, while nonpolar compounds dissolve in nonpolar solvents.

What are polar compounds?

Compounds with an unequal distribution of electrical charge.

What type of solvent dissolves polar compounds?

Polar solvents such as water.

What are nonpolar compounds?

Compounds without significant separation of electrical charge.

What type of solvent dissolves nonpolar compounds?

Nonpolar solvents such as fats.

What does hydrophilic mean?

"Water loving"; readily dissolves in water.

What is an example of a hydrophilic substance?

NaCl.

What does hydrophobic mean?

"Water fearing"; does not dissolve readily in water.

What is an example of a hydrophobic substance?

Fats.

What does amphipathic mean?

A molecule that has both hydrophilic and hydrophobic regions.

What is an example of an amphipathic molecule?

Phospholipids.

How do amphipathic molecules arrange themselves in water?

Hydrophilic regions face the water while hydrophobic regions face away from the water.

When NaCl dissolves in water, what are the solutes?

Na⁺ and Cl⁻.

When NaCl dissolves in water, what is the solvent?

Water.

Why does water dissolve NaCl?

Water is polar and attracts the charged Na⁺ and Cl⁻ ions.

What are the two ions in sodium chloride?

Na⁺ and Cl⁻.

What does pH indicate?

The acidity of a solution.

What primarily determines the acidity of a solution?

The concentration of free hydrogen ions ([H⁺]).

What is the equation for pH?

pH = -log[H⁺].

What does [H⁺] represent?

The concentration of free hydrogen ions.

What happens to pH when [H⁺] increases?

pH decreases and the solution becomes more acidic.

What pH is acidic?

pH < 7.

What pH is neutral?

pH = 7.

What pH is alkaline/basic?

pH > 7.

If a solution has a high [H⁺], is it acidic or basic?

Acidic.

If a solution has a low [H⁺], is it acidic or basic?

More basic/alkaline.

What are organic molecules?

Molecules that contain carbon and hydrogen.

What are the four major types of organic molecules?

Carbohydrates, lipids, proteins, and nucleic acids.

What elements are carbohydrates primarily made of?

Carbon, hydrogen, and oxygen (C, H, O).

What is the general formula for many carbohydrates?

CₙH₂ₙOₙ.

What are carbohydrates?

Organic molecules including sugars and starches that are important for energy storage and production.

What are the main functions of carbohydrates?

Energy storage and energy production.

What is a monosaccharide?

A single sugar molecule; an example is glucose.

What is glucose?

A monosaccharide with the formula C₆H₁₂O₆ that is an important energy source.

What is galactose?

A monosaccharide with the same formula as glucose (C₆H₁₂O₆) but a different arrangement of atoms.

What is a disaccharide?

A carbohydrate formed by linking two monosaccharides.

What is sucrose?

A disaccharide made from glucose and fructose.

What is a polysaccharide?

A carbohydrate made of many sugar units.

What is glycogen?

A polysaccharide made of glucose units that serves as a high-energy storage molecule.

What happens to glycogen when energy is needed?

Glucose units can be released for use by the body and into the blood.

What are lipids?

Organic molecules that include fatty acids, triglycerides, phospholipids, and steroids.

What elements are lipids primarily made of?

Mostly carbon and hydrogen.

What type of bonds are common in lipids?

Nonpolar covalent bonds.

Why do lipids have low solubility in water?

They contain many nonpolar bonds and regions.

What are the major functions of lipids?

Energy storage, membranes, hormones, and insulation.

What are the major types of lipids discussed in Chapter 2?

Fatty acids, triglycerides, phospholipids, and steroids.

What are the subunits used to form triglycerides?

Glycerol and fatty acids.

What are the subunits used to form phospholipids?

Glycerol, two fatty acids, and one or more charged groups.

What is a triglyceride?

A lipid formed from glycerol and fatty acids; an important form of stored body fat.

What is a phospholipid?

An amphipathic lipid containing glycerol, two fatty acids, and a charged group; an important component of cell membranes.

What is the hydrophilic region of a phospholipid?

The polar, charged head region.

What is the hydrophobic region of a phospholipid?

The nonpolar fatty acid tail region.

What is a micelle?

An aggregate of amphipathic molecules arranged so their hydrophilic regions face water and hydrophobic regions face inward.

What is cholesterol?

A steroid lipid that helps promote membrane fluidity and serves as a starting material for steroid hormones.

What are proteins?

Polymers made from amino acid monomers.

What elements are commonly found in proteins?

Carbon, hydrogen, oxygen, nitrogen, and sulfur, plus small amounts of other elements.

What are the functions of proteins?

Enzymes, cell attachment, cytoskeleton, muscle contraction, hormones, and many other functions.

What is an amino acid?

The monomer/subunit used to build proteins.

What three major components does every amino acid have?

An amino group, a carboxyl group, and a variable side chain (R group).

What determines the identity/properties of an amino acid?

Its variable side chain (R group).

What is a peptide bond?

A covalent bond that connects neighboring amino acids.

What is a polypeptide?

A chain of amino acids connected by peptide bonds.

How are many protein bonds formed?

Through dehydration reactions.

What are the four levels of protein structure?

Primary, secondary, tertiary, and quaternary.

What is primary protein structure?

The linear sequence of amino acids in a polypeptide chain.

What is secondary protein structure?

Local folding of a polypeptide into structures such as alpha helices and beta sheets.

What type of bond stabilizes secondary protein structure?

Hydrogen bonds.

What is an alpha helix?

A helical form of secondary protein structure stabilized by hydrogen bonds.

What is a beta-pleated sheet?

A sheet-like form of secondary protein structure stabilized by hydrogen bonds.

What is tertiary protein structure?

The overall three-dimensional shape formed when a polypeptide folds and bends.

What interactions contribute to tertiary protein structure?

Hydrogen bonds, ionic bonds, van der Waals forces, and covalent bonds between side chains.

What is quaternary protein structure?

A structure formed when two or more polypeptide chains bond together.

Does every protein have quaternary structure?

No. Only proteins made of two or more polypeptides have quaternary structure.