BIO152 Lecture 3: Macromolecules

Flashcards covering key concepts from BIO152 Lecture 3 on biological macromolecules, including carbohydrates, lipids, proteins, and nucleic acids.

What four main classes of large biological molecules make up all living things?

Carbohydrates, lipids, proteins, and nucleic acids.

How does a dehydration reaction synthesize a polymer?

It connects two monomers by covalently bonding them together through the loss of a water molecule.

What chemical reaction breaks down polymers into individual monomers?

A hydrolysis reaction, which adds a water molecule to break the covalent bond between monomers.

What type of covalent bond joins two monosaccharides to form a disaccharide?

A glycosidic linkage.

How do starch and glycogen differ in their location and biological function?

Starch is a storage polysaccharide in plants stored as granules within chloroplasts, whereas glycogen is stored primarily in animal liver and muscle tissues to release glucose when energy demand rises.

Why can human enzymes digest starch but not cellulose?

Starch is composed of $\alpha$ glucose monomers forming $\alpha$ glycosidic linkages, which digestive enzymes can hydrolyze. Cellulose consists of $\beta$ glucose monomers forming $\beta$ linkages that human digestive enzymes cannot break down.

What structural polysaccharide is used to form arthropod exoskeletons and fungal cell walls?

Chitin.

Why are lipids hydrophobic?

Lipids consist mostly of nonpolar hydrocarbon chains, which have little to no affinity for water.

Where do humans and other mammals store their fat, and what functions does this tissue serve?

Fat is stored in adipose cells. Adipose tissue functions in energy storage, cushioning vital organs, and insulating the body.

In a phospholipid molecule, which parts are hydrophilic and which are hydrophobic?

The phosphate head group is hydrophilic, while the two fatty acid tails are hydrophobic.

What is the key structural feature common to all steroids?

A carbon skeleton consisting of four fused rings.

What are the common functional groups present in every amino acid monomer?

An amino group ($\text{-NH}_2$ or $\text{-NH}_3^+$) and a carboxyl group ($\text{-COOH}$ or $\text{-COO}^-$) attached to a central $\alpha$ carbon.

What type of bond links amino acids together into polypeptides?

A peptide bond, formed through a dehydration reaction between the carboxyl group of one amino acid and the amino group of another.

What interactions drive the formation of secondary protein structures like $\alpha$-helices and $\beta$-pleated sheets?

Hydrogen bonds formed between repeating constituents of the polypeptide backbone.

What types of side-chain (R group) interactions stabilize the tertiary structure of a protein?

Hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals interactions, and covalent disulfide bridges.

What quaternary structures are illustrated by collagen and hemoglobin?

Collagen is a fibrous protein composed of three helical polypeptides coiled like a rope. Hemoglobin is a globular protein consisting of four polypeptides (two $\alpha$ and two $\beta$ chains).

What specific amino acid alteration causes sickle-cell disease?

A single amino acid substitution where valine replaces glutamic acid at the 6th position in the $\beta$ subunit of hemoglobin.

What is protein denaturation and what conditions can cause it?

Denaturation is the process where a protein unravels and loses its native shape and biological activity, caused by alterations in pH, salt concentration, temperature, or other environmental factors.

What components make up a nucleoside versus a nucleotide?

A nucleoside consists of a nitrogenous base and a sugar. A nucleotide consists of a nucleoside plus a phosphate group.

How do pyrimidines and purines differ in their chemical ring structures?

Pyrimidines (cytosine, thymine, uracil) have a single six-membered ring. Purines (adenine, guanine) have a six-membered ring fused to a five-membered ring.

In this phospholipid structure diagram, what chemical feature creates the bend in the hydrophobic tail?

A kink is created by a cis double bond in the hydrocarbon chain of the fatty acid.

Identify the non-covalent and covalent interactions stabilizing the tertiary structure in this diagram.

Hydrogen bonds, hydrophobic and van der Waals interactions, ionic bonds, and covalent disulfide bridges between R groups.

According to this diagram, what three steps take place inside a chaperonin to assist protein folding?

1. An unfolded polypeptide enters the hollow cylinder. 2. The cap attaches, inducing a shape change that creates a hydrophilic folding environment. 3. The cap detaches and the correctly folded protein is released.

What sequence of events in gene expression is illustrated in this diagram?

1. Synthesis of mRNA from DNA in the nucleus. 2. Movement of mRNA into the cytoplasm. 3. Synthesis of protein by a ribosome using mRNA.

Based on this figure, what structural difference distinguishes deoxyribose from ribose?

Deoxyribose has a hydrogen atom ($\text{-H}$) at the $2'$ carbon position, whereas ribose has a hydroxyl group ($\text{-OH}$) at the $2'$ position.