Chapter 5 Lipids and Nucleic Acids – Question and Answer Flashcards

A set of Q&A flashcards covering lipids (fats, phospholipids, steroids) and nucleic acids (DNA/RNA structure, components, and function) based on the notes from Chapter 5.

What is the main characteristic all lipids share?

They are nonpolar and hydrophobic.

Why are lipids insoluble in water?

Because they are nonpolar molecules that do not form hydrogen bonds with water.

What are the two smaller molecules that lipids commonly consist of in triglycerides?

Glycerol (a three-carbon alcohol) and fatty acids (long nonpolar hydrocarbon chains with a carboxyl group).

What bond links glycerol to fatty acids in triglycerides?

An ester linkage between a hydroxyl group of glycerol and the carboxyl group of a fatty acid.

What is the triglyceride?

The lipid formed from glycerol and three fatty acids; the most common form of fats, serving as a major energy source.

What is the defining structural difference of phospholipids compared to fats?

Phospholipids have two fatty acids and a phosphate-containing head group on glycerol, making them amphipathic.

In a phospholipid bilayer, which part is polar and interacts with water?

The phosphate-containing head is polar and hydrophilic; the tails are nonpolar and hydrophobic.

What determines membrane fluidity in animals vs plants?

In animals, cholesterol helps maintain membrane fluidity; in plants, seasonal changes in fatty acid saturation adjust fluidity (more unsaturated in winter, more saturated in summer).

How do animals maintain membrane fluidity across temperatures?

They use cholesterol to regulate membrane fluidity.

What is the structural skeleton of steroids like cholesterol?

A carbon skeleton of four fused rings (three six-membered rings and one five-membered ring).

What are two important roles of cholesterol?

Maintains membrane integrity in animals and serves as the precursor to other steroids.

How can cholesterol contribute to health risks?

Cholesterol contributes to atherosclerosis.

How do saturated and unsaturated fats differ in double bonds and packing?

Saturated fats have no double bonds and pack tightly (solid at room temperature); unsaturated fats have one or more double bonds and have kinks that prevent tight packing (usually liquid).

Why are unsaturated fats usually liquid at room temperature?

Double bonds create kinks in the fatty acid chains that prevent tight packing.

Why do plants vary the saturation of fatty acids with the seasons?

To maintain membrane fluidity: more saturated in summer to prevent excess fluidity, and more unsaturated in winter to keep membranes fluid.

What are the building blocks of DNA?

Nucleotides, each consisting of a nitrogenous base, a pentose sugar, and a phosphate group.

What are the three parts of a nucleotide?

Nitrogenous base, a pentose sugar, and a phosphate group.

What are the building blocks of RNA?

Nucleotides containing a nitrogenous base (A, C, G, U), a ribose sugar, and a phosphate group.

What sugar is found in DNA vs RNA?

DNA uses deoxyribose; RNA uses ribose.

Which bases pair in DNA, and what ensures the pairing?

A pairs with T and C pairs with G; hydrogen bonds stabilize the pairs.

What type of bond links nucleotides in a DNA strand, forming the backbone?

Phosphodiester bonds (dehydration synthesis forming sugar-phosphate backbone).

What is DNA’s overall structure and orientation?

DNA is a double helix with antiparallel strands (one runs 5'→3', the other 3'→5').

What is the end-to-end polarity of DNA called?

5' end and 3' end define the directional orientation of the strand.

What is the primary function of RNA?

To carry the genetic message from DNA to synthesize proteins; RNA can be single-stranded and, in some cases, act as an enzyme.