Biol 1500: 4&5

What is organic chemistry?

The study of carbon-containing compounds.

Why is carbon especially important in biology?

Carbon can form four covalent bonds, allowing it to build stable and diverse molecular structures.

How many covalent bonds can carbon typically form?

Four.

What elements can carbon commonly bond with?

Hydrogen, oxygen, nitrogen, sulfur, phosphorus, and other carbon atoms.

What is a carbon skeleton?

The carbon framework of an organic molecule.

How can carbon skeletons vary?

They can differ in length, branching, double-bond position, and ring structure.

Why does carbon's ability to bond with itself create molecular diversity?

Carbon can form chains, branches, rings, and varied three-dimensional structures.

What is a hydrocarbon?

A molecule containing only carbon and hydrogen.

Why are hydrocarbons generally hydrophobic?

Their carbon-hydrogen regions are largely nonpolar and do not mix well with water.

Why are hydrocarbons energy-rich?

C–H bonds store chemical energy that can be released during reactions.

What are isomers?

Molecules with the same molecular formula but different structures and properties.

What are structural isomers?

Isomers that differ in the covalent arrangement of their atoms.

What are cis-trans isomers?

Isomers that differ in spatial arrangement around an inflexible double bond.

What are enantiomers?

Molecules that are mirror images of each other around an asymmetric carbon.

Why can enantiomers have different biological effects?

Biological receptors and enzymes are three-dimensional, so one enantiomer may fit a target better than the other.

Why is molecular shape important in biology?

Molecules interact through complementary shape, charge, polarity, and bonding patterns.

What are functional groups?

Specific groups of atoms attached to a carbon skeleton that influence an organic molecule's chemical behavior.

Why are functional groups important?

They can alter a molecule's polarity, acidity, charge, and reactivity.

What does a hydroxyl group do?

It is polar, can form hydrogen bonds, and is characteristic of alcohols.

What does a carbonyl group do?

It occurs in aldehydes and ketones and is important in sugars.

What does a carboxyl group do?

It is acidic, can donate H⁺, and can become negatively charged.

What does an amino group do?

It is basic and can accept H⁺, becoming positively charged.

What does a sulfhydryl group do?

It can form disulfide bridges in proteins.

What does a phosphate group do?

It adds negative charge and is important in ATP and cellular signaling.

What does a methyl group do?

It is nonpolar and can affect gene expression and molecular shape.

Which functional group is characteristic of alcohols?

Hydroxyl.

Which functional group is characteristic of thiols?

Sulfhydryl.

Which functional group behaves as a base?

Amino.

Which functional group behaves as an acid?

Carboxyl.

Which functional group plays a major role in energy transfer?

Phosphate.

What is ATP?

Adenosine triphosphate, a molecule that stores potential energy in its phosphate groups.

How many phosphate groups does ATP have?

Three.

What happens when ATP is hydrolyzed?

ATP is converted to ADP and inorganic phosphate, releasing usable energy.

Why are ATP's phosphate groups reactive?

They carry negative charges.

What is the central idea of Chapter 4?

Structure creates function.

What did Stanley Miller's experiment demonstrate?

Organic molecules can form abiotically under simulated early-Earth conditions.

What happens to carbon atoms around a double bond?

Double bonds restrict rotation and place the attached atoms in the same plane.

Why can two molecules with the same molecular formula have different biological effects?

They can have different structures or three-dimensional arrangements.

What is a macromolecule?

A very large biological molecule.

What is a polymer?

A long chain made from repeating smaller units called monomers.

What is a monomer?

A smaller molecular unit that can be joined to form a polymer.

Which three major biological molecule classes are polymers?

Carbohydrates, proteins, and nucleic acids.

Are lipids true polymers?

No. Lipids are not true polymers but are grouped together because of their hydrophobic behavior.

What reaction builds polymers from monomers?

A dehydration reaction.

What happens during a dehydration reaction?

Monomers are joined while water is removed.

What reaction breaks polymers apart?

Hydrolysis.

What happens during hydrolysis?

Water is added to break a bond between monomers.

What role do enzymes play in building and breaking biological molecules?

They speed up the chemical reactions that assemble or break molecules.

Why can a small number of monomers produce enormous molecular diversity?

The monomers can be arranged in many different sequences and structures.

What is the recurring principle connecting Chapters 4 and 5?

Structure determines function.

What are carbohydrates?

Molecules that include sugars and polymers of sugars and serve as fuel and building materials.

What is a monosaccharide?

A simple sugar and major cellular fuel.

What is a disaccharide?

A carbohydrate made from two monosaccharides joined by a glycosidic linkage.

What is a polysaccharide?

A polymer made from many sugar monomers.

What is a glycosidic linkage?

A covalent bond between sugar monomers.

What is maltose made from?

Two glucose molecules.

What is sucrose made from?

Glucose and fructose.

What determines the properties of a carbohydrate made from the same monomers?

The location and orientation of the linkages.

What are trioses, pentoses, and hexoses?

Monosaccharides classified according to whether they contain three, five, or six carbon atoms.

What is the difference between an aldose and a ketose?

They differ in the location of the carbonyl group.

What happens to many monosaccharides in water?

They form rings rather than remaining linear.

What is starch?

The main storage polysaccharide of plants.

Where do plants store surplus starch?

In plastids such as chloroplasts.

What is glycogen?

The main storage polysaccharide of animals.

Where is glycogen stored mainly?

In liver and muscle cells.

What is cellulose?

A structural polysaccharide and major component of plant cell walls.

What is the difference between starch and cellulose linkages?

Starch uses α-glucose linkages, while cellulose uses β-glucose linkages.

Why can humans digest starch but not cellulose without microbial help?

The different glucose linkages require different digestive enzymes.

What is chitin?

A structural polysaccharide that strengthens arthropod exoskeletons and many fungal cell walls.

What are lipids?

Diverse hydrophobic molecules that mix poorly with water because they contain large hydrocarbon regions.

What are three major types of lipids discussed in lecture?

Fats, phospholipids, and steroids.

What are the major functions of fats?

Long-term energy storage, insulation, and cushioning.

What are the major functions of phospholipids?

They form biological membranes.

What is the basic structure of a phospholipid?

Two hydrophobic fatty acid tails and a hydrophilic phosphate-containing head.

What does amphipathic mean?

Having both hydrophilic and hydrophobic regions.

Why do phospholipids form bilayers in water?

Hydrophilic heads interact with water while hydrophobic tails avoid water and point inward.

What is a triglyceride?

A molecule made from glycerol and three fatty acids.

What is glycerol?

A three-carbon alcohol that forms the backbone of fats.

What is a fatty acid?

A molecule with a carboxyl group attached to a long hydrocarbon chain.

What is an ester linkage?

The linkage joining fatty acids to glycerol in fats.

Why does fat store a lot of energy?

Fat contains energy-rich hydrocarbon regions and stores more energy per gram than carbohydrate.

What is a saturated fatty acid?

A fatty acid with no double bonds and the maximum number of hydrogens.

What is an unsaturated fatty acid?

A fatty acid containing one or more double bonds.

What effect does a cis double bond have on a fatty acid?

It creates a kink that prevents tight packing.

How do double bonds affect fat behavior?

They change molecular packing and melting point.

What is hydrogenation?

A process that can convert unsaturated fats and may produce trans fats.

What are steroids?

Lipids containing four fused carbon rings.

What is cholesterol?

A steroid that is part of animal cell membranes and is a precursor for other steroids.

What are steroid hormones?

Hormones synthesized from steroid structures such as cholesterol.

What are proteins?

Biological molecules that perform a huge range of cellular functions.

What are some functions of proteins?

Catalysis, defense, storage, transport, signaling, movement, and support.

What is an enzyme?

A protein that speeds up a chemical reaction.

What are amino acids?

The monomers that build proteins.

What do all amino acids have in common?

They contain an amino group and a carboxyl group and differ in their R groups.

What is an R group?

The variable side chain of an amino acid that determines its chemical properties.

What types of R groups can amino acids have?

Nonpolar, polar, acidic, or basic side chains.

What determines how a protein folds and functions?

Its amino acid sequence.

What is a peptide bond?

A bond between the carboxyl group of one amino acid and the amino group of another.

How are amino acids joined to form polypeptides?

Through dehydration reactions that form peptide bonds.

What are the two ends of a polypeptide?

An amino end and a carboxyl end.