Week 2 - Lecture 4: Chemical Building Blocks

How many naturally occurring chemical elements exist?

There are $92$ natural chemical elements.

What is the definition of an atom?

An atom is the smallest unit of an element that has the chemical characteristics of that element.

Which subatomic particles compose an atom?

Protons, electrons, and neutrons.

What are the electrical charges of protons, electrons, and neutrons?

A proton is positively charged, an electron is negatively charged, and a neutron is neutral.

How do the numbers of protons and electrons compare in a single element?

A single element usually has an equal number of protons and electrons.

According to Figure 5.2, how many electron shells do hydrogen and carbon atoms have?

Hydrogen atoms have one electron shell, while carbon atoms have two electron shells.

Why do elements form chemical bonds with each other?

Elements form chemical bonds to fill their outer electron shells and become stable.

How do covalent bonds form?

Covalent bonds form when atoms share electrons to fill their electron shells.

How many covalent bonds can a single Hydrogen atom form?

$1$ covalent bond.

How many possible covalent bonds can an Oxygen atom form?

$2$ covalent bonds.

How many possible covalent bonds can a Sulfur atom form?

$2$ covalent bonds.

How many possible covalent bonds can a Nitrogen atom form?

$3$ covalent bonds.

How many possible covalent bonds can a Carbon atom form?

$4$ covalent bonds.

What sample molecule in Figure 5.4b is formed by Nitrogen bonding with three Hydrogen atoms?

Ammonia ($NH_3$).

What sample molecule in Figure 5.4b is formed by Carbon bonding with four Hydrogen atoms?

Methane ($CH_4$).

How do noncovalent bonds (NCBs) compare to covalent bonds in strength?

Noncovalent bonds are weaker than covalent bonds.

Why is a water ($H_2O$) molecule polar?

It has an uneven charge distribution, where the oxygen atom is slightly negative and the hydrogen atoms are slightly positive.

What physical state does hydrogen bonding give to water at room temperature?

Hydrogen bonding between water molecules is what makes water a liquid.

What is an ion?

An ion is an atom that has lost or gained electrons, causing it to become electrically charged.

What electrical charge does an atom acquire when it loses or gains an electron?

An atom that loses an electron becomes positive, while an atom that gains an electron becomes negative.

How do ionic bonds form?

Ionic bonds form between atoms or ions of opposite charge.

What happens to salt ($NaCl$) when it dissolves in water?

The ionic bond between $Na^+$ and $Cl^-$ breaks, and water molecules interact with the ions via noncovalent bonding.

What does it mean for oil molecules to be hydrophobic?

They are nonpolar, excluded from water, and tend to clump together.

Why are vinegar molecules classified as hydrophilic?

They are water-loving molecules held in solution by water molecules.

What are the four major classes of chemical compounds found in living organisms?

Sugars, nucleotides, amino acids, and fatty acids.

Which element is predominant in organic compounds?

Carbon.

According to Table 5.1, what is Hydrogen cyanide ($HCN$)?

A poison that is released in small amounts from some roots and fruit pits.

What is the chemical formula and primary use of Butane?

Formula: $C_4H_{10}$; Primary use: Component of natural gas used for camp stove burners.

What branched carbon compound serves as the building block of natural rubber?

Isoprene ($C_5H_8$).

What ring-shaped carbon compound with formula $C_6H_6$ is an important industrial solvent?

Benzene.

What is a monomer?

An individual small carbon-containing molecule with $20$ or fewer atoms.

What is a polymer?

A macromolecule made of joined monomers.

If five different monomers are available, how many different kinds of polymers six units long can be linked?

$15,625$ different kinds of polymers.

What chemical formula ratio defines a monosaccharide?

Composed of carbon, hydrogen, and oxygen in a $1:2:1$ ratio, expressed as $(CH_2O)_n$.

What is the molecular formula of glucose when $n = 6$?

$C_6H_{12}O_6$.

What disaccharide is formed when glucose and fructose combine, and through what reaction?

Sucrose (table sugar), formed via a dehydration reaction that releases a water molecule.

What type of reaction breaks monomers apart by adding a water molecule?

Hydrolytic reactions (hydrolysis).

What is glycogen?

A highly branched polysaccharide of glucose that serves as the main storage polysaccharide in animals and fungi.

What is the main storage polysaccharide in plants and green algae?

Starch.

Why is cellulose beneficial in human diet even though it cannot be digested?

It adds insoluble fiber to our diet, which is good for intestinal health.

What three structural components make up a nucleotide?

A 5-carbon sugar molecule, a base molecule, and a phosphate group.

How do ribose and deoxyribose differ structurally?

They are both five-carbon sugars, but they differ by only one oxygen atom.

Which base is incorporated into DNA molecules, but replaced by uracil in RNA molecules?

Thymine.

Where does ATP store energy for cellular processes?

ATP stores energy in the covalent bonds that link its phosphate groups.

What four groups are bonded to the central alpha carbon in an amino acid?

An amino group ($NH_2$), a carboxyl group ($COOH$), a hydrogen atom ($H$), and a side chain ($R$ group).

What type of covalent bond links amino acids into protein polymers?

Peptide bonds.

What are the four levels of protein structure shown in Figure 5.17?

Primary structure, secondary structure (alpha helix and beta pleated sheets), tertiary structure, and quaternary structure.

What is the key structural difference between saturated and unsaturated fatty acids?

Saturated fatty acids contain no double bonds in their chains, while unsaturated fatty acids contain one or more double bonds.

What occurs during partial hydrogenation of vegetable oil?

Hydrogen gas ($H_2$) and catalysts convert double bonds, straightening fatty acid chains into trans fats or saturated lipids with a solid/semisolid consistency.

How are phospholipids arranged in a cell membrane bilayer?

Hydrophilic phosphate heads face outward toward water, while hydrophobic fatty acid tails remain together in the interior away from water.

There are __________ natural chemical elements.

92

An atom is the smallest unit of an element that has the __________ characteristics of that element.

chemical

Subatomic particles called __________ carry a positive charge.

protons

Subatomic particles called __________ carry a negative charge.

electrons

Subatomic particles that carry no charge are called __________.

neutrons

Hydrogen atoms have __________ electron shell(s), whereas carbon atoms have two.

one

Elements form chemical bonds in order to become __________.

stable

Covalent bonds are formed when atoms __________ electrons.

share

The outermost shell of an oxygen atom has six electrons but can hold a maximum of __________ electrons.

eight

By sharing their electrons, two hydrogen atoms fill their single electron shell to hold a total of __________ electrons.

two

A single hydrogen ($H$) atom can form a maximum of __________ covalent bond(s).

1

An oxygen gas ($O_2$) molecule is formed by sharing __________ pairs of electrons between two oxygen atoms.

two

Sulfur ($S$) can form a maximum of __________ possible bonds, as shown in hydrogen sulfide ($H_2S$).

2

Nitrogen ($N$) can form a maximum of __________ possible bonds, as shown in ammonia ($NH_3$).

3

Carbon ($C$) can form a maximum of __________ possible bonds, as shown in methane ($CH_4$).

4

Non-covalent bonds are __________ than covalent bonds.

weaker

In a water molecule ($H_2O$), the oxygen atom is slightly negative, and the hydrogen atom is slightly __________.

positive

Hydrogen bonding between water molecules is what makes water a __________.

liquid

An atom that loses an electron acquires a __________ charge.

positive

An atom that gains an electron acquires a __________ charge.

negative

Ionic bonds form between atoms of __________ charge.

opposite

When salt dissolves in water, the __________ pole of the water molecule orients toward the positive sodium ion ($Na^+$).

negative

Oil molecules are hydrophobic because they are excluded from water and tend to __________ together.

clump

Vinegar molecules are held in solution by water molecules because they are __________.

hydrophilic

Carbon compounds present in living organisms are referred to as __________ compounds.

organic

Hydrogen cyanide ($HCN$) is a poison released in small amounts from some roots and __________.

fruit pits

Butane ($C_4H_{10}$) is a component of natural gas used for __________.

camp stove burners

Isoprene ($C_5H_8$) serves as a building block of natural __________.

rubber

Benzene ($C_6H_6$) is an important industrial solvent where carbon atoms form __________.

rings

Monomers are individual small molecules containing __________ or fewer atoms.

20

If five different monomers are available, they can be linked to make __________ different kinds of polymers that are each six units long.

15,625

Monosaccharides are simple sugars composed of carbon, hydrogen, and oxygen in a ratio of __________.

1:2:1

The molecular formula for glucose, where $n=6$ in $(CH_2O)_n$, is __________.

$$C_6H_{12}O_6$$

Glucose combines with fructose to form the disaccharide sucrose through a __________ reaction.

dehydration

Hydrolytic reactions break monomers apart with the addition of a __________ molecule.

water

The main storage polysaccharide in animals and fungi is __________.

glycogen

The main storage polysaccharide in plants and green algae is __________.

starch

Although it cannot be broken down in our digestive system, __________ adds insoluble fiber to our diet.

cellulose

A nucleotide is composed of a 5-carbon sugar, a base molecule, and a __________ group.

phosphate

Ribose and deoxyribose are both five-carbon sugars that differ by only one __________ atom.

oxygen

DNA molecules incorporate the nitrogenous base __________ instead of uracil.

thymine

RNA molecules incorporate the nitrogenous base __________ instead of thymine.

uracil

ATP stores energy in the covalent bonds that link its __________ groups.

phosphate

An amino acid contains an amino group ($NH_2$), a carboxyl group ($COOH$), and a side chain ($R$ group) bonded to a central __________ carbon.

alpha

Amino acids are covalently joined together by __________ bonds to form polypeptide chains.

peptide

Working proteins that perform chemical operations in cells are called __________.

enzymes

Saturated fatty acids contain __________ double bonds in their hydrocarbon chains.

no

Unsaturated lipids are liquid at room temperature because __________ in the fatty acid chains prevent close packing.

bends

During partial hydrogenation, some unsaturated lipids are converted to __________ fats, which retain double bonds but have straightened chains.

trans

Every phospholipid consists of a hydrophilic head group containing a glycerol and a phosphate, along with two hydrophobic __________ tails.

fatty acid