Carbon and the Molecular Diversity of Life

Flashcards covering carbon properties, functional groups, and the four major classes of organic macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

What is the primary reason carbon is considered the backbone of life?

Carbon is unparalleled in its ability to form large, complex, and diverse molecules.

Which three elements always compose organic compounds according to the lecture notes?

Carbon, oxygen, and hydrogen.

How many valence electrons does a carbon atom have, and how does it complete its outer shell?

Carbon has $4$ valence electrons and completes its outer shell by sharing $4$ electrons in $4$ covalent bonds.

What is the name of the one-atom-thick planar sheet of carbon atoms mentioned in the text?

Graphene.

In molecules with multiple carbons, what is the shape of a carbon atom bonded to four other atoms?

A tetrahedral shape.

What are hydrocarbons and what is their primary characteristic regarding energy?

Hydrocarbons are the simplest organic compounds containing only carbon and hydrogen; they can undergo reactions that release a large amount of energy.

What are the three types of isomers identified in the transcript?

1. Structural isomers, 2. Cis-trans isomers, and 3. Enantiomers.

Why are enantiomers important in the pharmaceutical industry?

Two enantiomers of a drug may have different effects, and usually only one isomer is biologically active, such as $S$-Ibuprofen being effective while $R$-Ibuprofen is ineffective.

Which functional group is characterized as being acidic because it can donate an $H^+$?

Carboxyl group ($-COOH$).

Which functional group is a base and can pick up an $H^+$ from the surrounding solution?

Amino group ($-NH_2$).

What is the function of the Sulfhydryl group ($-SH$) in proteins?

Two $-SH$ groups can react to form a covalent bond called a 'cross-link' which helps stabilize protein structure.

What reaction is used to synthesize a polymer by removing a water molecule?

Dehydration reaction (or dehydration synthesis).

What reaction is used to break down a polymer by adding a water molecule?

Hydrolysis.

What is the general molecular formula for carbohydrates?

$(CH_2O)_n$.

What is the difference between an aldose and a ketose sugar?

In an aldose, the carbonyl group ($C=O$) is at the end of the carbon skeleton; in a ketose, it is within the carbon skeleton.

What consists of a disaccharide and how are the monomers joined?

A disaccharide consists of two monosaccharides joined through a dehydration reaction to form a glycosidic linkage.

Differentiate between starch and glycogen in terms of where they are stored and their organisms.

Starch is the storage of glucose in plants (stored in plastids/chloroplasts), while glycogen is the storage of glucose in animals (stored in the liver).

Why are humans unable to digest cellulose, often referred to as 'insoluble fiber'?

Enzymes that digest starch are unable to break the $\beta$ linkages of cellulose because of their different shapes.

What defines a triglyceride (fat) structurally?

One glycerol molecule and three fatty acid chains joined by ester linkages.

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

Saturated fatty acids have the maximum number of hydrogen atoms and no double bonds, while unsaturated fatty acids have one or more double bonds (often creating a 'kink').

Describe the structure of a phospholipid and its behavior in water.

It has a glycerol attached to two fatty acids (hydrophobic tails) and a phosphate group (hydrophilic head); in water, they self-assemble into a bilayer.

What is the 'base steroid' from which the body produces other steroids like sex hormones?

Cholesterol.

What components make up the basic structure of an amino acid?

An alpha ($\beta$) carbon bound to an amino group, a carboxyl group, a hydrogen atom, and a variable R side group.

What are the four levels of protein structure?

1. Primary (aa sequence), 2. Secondary ($\beta$-helices and $\beta$-pleated sheets), 3. Tertiary (3D shape from R group interactions), 4. Quaternary (aggregation of multiple polypeptide chains).

Which specific interaction reinforces the 3D tertiary structure of a protein through covalent bonding?

Disulfide bridges.

What is the molecular cause of Sickle-Cell Disease?

A single amino acid substitution in the primary structure of the protein hemoglobin.

What are chaperonins?

Proteins that assist the proper folding of other proteins by providing a hydrophilic environment within a hollow cylinder.

What three components make up a nucleotide?

A Pentose (5-carbon sugar), a phosphate group, and an organic (nitrogenous) base.

Differentiate between Pyrimidines and Purines.

Pyrimidines (cytosine, thymine, uracil) have a single 6-membered ring; Purines (adenine, guanine) have a 6-membered ring fused to a 5-membered ring.

What sugar is found in DNA versus RNA?

DNA contains deoxyribose, while RNA contains ribose.

In which direction does a DNA or RNA chain 'grow'?

$5'$ to $3'$.

What are the structural components of ATP (Adenosine Triphosphate)?

Ribose, adenine, and three phosphate groups.