Chapter 5: The Structure and Function of Large Biological Molecules – Carbohydrates and Lipids

Flashcards covering carbohydrates and lipids from Campbell Biology Chapter 5 notes (structure, polymers, reactions, and lipid types).

What are the four classes of large biological molecules?

Carbohydrates, lipids, proteins, and nucleic acids.

Which three classes are polymers?

Carbohydrates, proteins, and nucleic acids (lipids are not polymers).

Define polymer and monomer.

A polymer is a long molecule built from many monomers; a monomer is a single building-block molecule.

What is dehydration synthesis?

A dehydration reaction where two monomers bond with the loss of a water molecule.

What is hydrolysis?

The breakdown of polymers by adding a water molecule; the reverse of dehydration synthesis.

What are monosaccharides?

The simplest sugars; used for fuel; can be converted into other molecules; can be polymerized; example: glucose.

What are disaccharides?

Carbohydrates formed when two monosaccharides join via a glycosidic linkage; examples include maltose and sucrose.

What are polysaccharides?

Polymers of sugars with storage or structural roles; examples: starch, glycogen, cellulose, chitin.

What is the most common monosaccharide?

Glucose.

What are aldoses and ketoses?

Monosaccharides classified by carbonyl group: aldose (aldehyde) and ketose (ketone).

What is the significance of ring forms in sugars?

In aqueous solution, many sugars form ring structures; they can exist in linear or ring forms.

What is a glycosidic linkage?

A covalent bond formed between two monosaccharides by dehydration.

What determines the structure and function of a polysaccharide?

The sugar monomers and the positions of glycosidic linkages.

Name two storage polysaccharides and two structural polysaccharides.

Storage: starch (plants), glycogen (animals). Structural: cellulose (plants), chitin (arthropods).

What is starch?

A storage polysaccharide in plants, consisting entirely of glucose; amylose is the simplest form.

Where is glycogen stored in animals?

In the liver and muscle cells.

What is cellulose?

A structural polysaccharide; major component of plant cell walls; polymer of glucose with beta linkages.

How do alpha and beta glucose differ?

They are two ring forms of glucose; alpha linkages in starch; beta linkages in cellulose.

Why is cellulose difficult to digest for humans?

Because it has beta-1,4 glycosidic linkages; humans lack digestive enzymes; ruminants have microbes; it's dietary fiber.

What is chitin and where is it found?

A structural polysaccharide found in arthropod exoskeletons; used for surgical thread that decomposes after healing.

Are lipids polymers?

No; lipids do not form polymers.

What is the unifying feature of lipids?

They have little or no affinity for water (are hydrophobic).

What are the three main lipid types?

Fats, phospholipids, and steroids.

What are fats composed of?

Glycerol and fatty acids; glycerol is a three-carbon alcohol; a fatty acid has a carboxyl group attached to a long hydrocarbon chain.

What is a triacylglycerol?

A fat molecule formed when three fatty acids esterify to glycerol.

How do fatty acids vary?

They vary in chain length and in the number and placement of carbon–carbon double bonds (saturation).

What is a saturated fat?

A fat composed of saturated fatty acids; no double bonds; solid at room temperature; common in animals.

What is an unsaturated fat?

A fat composed of unsaturated fatty acids; one or more double bonds; typically liquid at room temperature; common in plants and fish.

What is the major function of fats?

Energy storage; stored in adipose tissue.

What are essential fatty acids and omega-3?

Fatty acids that must be obtained dietarily; omega-3 fatty acids are essential for normal growth and may protect against cardiovascular disease.

What is a phospholipid?

A lipid with two fatty acids and a phosphate group attached to glycerol; hydrophobic tails and hydrophilic head.

What happens when phospholipids are in water?

They self-assemble into a bilayer with the hydrophobic tails inward; major component of cell membranes.

What are steroids and give examples?

Lipids with four fused hydrocarbon rings; examples include cholesterol, testosterone, estrogen; anabolic steroids are synthetic testosterone.