Section 4: Carbon as The Molecular Basis of Life

SECTION 4 — CARBON: THE MOLECULAR BASIS OF LIFE (IMAT MASTER DECK)

Why is carbon considered the backbone of life?

It has four valence electrons and can form four stable covalent bonds.

How many covalent bonds can one carbon atom form?

Four.

Why is tetravalence important?

It allows carbon to build enormous, stable, complex molecules.

Can carbon bond to itself?

Yes, forming long chains, branched chains, and rings.

What types of carbon skeletons exist?

Straight chains, branched chains, rings, and combinations of these.

Why are carbon-carbon bonds stable?

They are strong covalent bonds.

Why is carbon more versatile than silicon in biology?

Carbon forms stable bonds at biological temperatures and supports far greater molecular diversity.

What is an organic molecule?

A molecule containing carbon bonded to hydrogen.

Are carbon dioxide and carbonates considered organic molecules?

No.

What is a hydrocarbon?

A molecule composed only of carbon and hydrogen.

Why are hydrocarbons generally hydrophobic?

C-H bonds are nonpolar.

What type of bonds are found in saturated hydrocarbons?

Only single covalent bonds.

What type of bonds are found in unsaturated hydrocarbons?

One or more double or triple bonds.

What is a saturated fat?

A lipid whose fatty acids contain only single bonds.

Why are saturated fats usually solid at room temperature?

Straight chains pack tightly together.

What is an unsaturated fat?

A lipid containing one or more double bonds.

Why are unsaturated fats usually liquid?

Double bonds create bends that prevent tight packing.

What is a cis double bond?

Hydrogen atoms are on the same side of the double bond.

What is a trans double bond?

Hydrogen atoms are on opposite sides of the double bond.

Which is healthier: cis or trans fats?

Cis fats.

Why are trans fats associated with cardiovascular disease?

They alter lipid metabolism and increase LDL cholesterol.

Why can't double bonds rotate freely?

The pi bond restricts rotation.

What is molecular diversity?

The enormous variety of molecular structures carbon can form.

Why is molecular shape important?

Shape determines biological function.

What is an isomer?

Molecules with the same molecular formula but different structures.

How many major classes of isomers are tested on the IMAT?

Three.

What are structural (constitutional) isomers?

Same formula but different covalent arrangements.

What are geometric (cis-trans) isomers?

Same covalent arrangement but different spatial arrangement around a double bond.

What are enantiomers?

Non-superimposable mirror images.

What creates an enantiomer?

A chiral carbon bonded to four different groups.

What is a chiral carbon?

A carbon attached to four different substituents.

Why are enantiomers biologically important?

Enzymes often recognize only one form.

Which amino acid configuration is used in proteins?

L-amino acids.

Which sugar configuration predominates in organisms?

D-sugars.

Why can two enantiomers have different biological effects?

Proteins and enzymes are themselves chiral.

What is a functional group?

A group of atoms responsible for characteristic chemical reactions.

Why do functional groups determine molecular behavior?

They affect polarity, acidity, and reactivity.

How many functional groups should you know for the IMAT?

Seven.

What is the hydroxyl group?

–OH.

Which functional group characterizes alcohols?

Hydroxyl.

Does the hydroxyl group increase water solubility?

Yes.

Why does the hydroxyl group increase polarity?

Oxygen is highly electronegative.

What is the carbonyl group?

C=O.

Where is the carbonyl group found in aldehydes?

At the end of the carbon skeleton.

Where is the carbonyl group found in ketones?

Within the carbon skeleton.

What functional group distinguishes sugars as aldoses or ketoses?

The carbonyl group.

What is the carboxyl group?

–COOH.

Why is the carboxyl group acidic?

It can donate H⁺.

What ion forms when a carboxyl group loses H⁺?

Carboxylate (–COO⁻).