Learn: Biological Macromolecules, Monomers, Polymers, and Lipids: Key Concepts for Biology

What are the four major biological macromolecules?

Carbohydrates, lipids, proteins, and nucleic acids.

What is a monomer?

A small molecular subunit that can be joined to form a larger molecule.

What is a polymer?

A large molecule made of repeating monomers joined together.

What is dehydration synthesis?

A reaction that joins molecules by removing a molecule of water.

What happens during dehydration synthesis?

A hydrogen from one molecule and a hydroxyl group from another combine to form water while a covalent bond forms between the molecules.

What is hydrolysis?

A reaction that breaks a polymer into smaller molecules by adding water.

How are dehydration synthesis and hydrolysis related?

They are essentially opposite processes; dehydration builds molecules by removing water, while hydrolysis breaks them apart by adding water.

Why are enzymes important in dehydration synthesis and hydrolysis?

They speed up these reactions.

What are the three major types of carbohydrates?

Monosaccharides, disaccharides, and polysaccharides.

What is the general formula for carbohydrates?

(CH2O)n.

What is a monosaccharide?

A single sugar molecule and the simplest form of carbohydrate.

What are common monosaccharides?

Glucose, galactose, and fructose.

What is the difference between an aldose and a ketose?

An aldose has an aldehyde group, while a ketose has a ketone group.

What is a triose?

A monosaccharide with three carbon atoms.

What is a pentose?

A monosaccharide with five carbon atoms.

What is a hexose?

A monosaccharide with six carbon atoms.

What is glucose's molecular formula?

C6H12O6.

What are glucose, galactose, and fructose?

Isomers because they have the same molecular formula but different structures.

What is an alpha glucose?

Glucose with the hydroxyl group on carbon 1 below the plane of the ring.

What is a beta glucose?

Glucose with the hydroxyl group on carbon 1 above the plane of the ring.

What is a disaccharide?

A carbohydrate made of two monosaccharides joined together.

What is a glycosidic bond?

A covalent bond that joins two monosaccharides.

What are the three common disaccharides?

Sucrose, lactose, and maltose.

What is sucrose made of?

Glucose and fructose.

What is lactose made of?

Glucose and galactose.

What is maltose made of?

Two glucose molecules.

What is a polysaccharide?

A long chain of monosaccharides linked by glycosidic bonds.

What are four important polysaccharides?

Starch, glycogen, cellulose, and chitin.

What is the main storage carbohydrate in plants?

Starch.

What is the main storage carbohydrate in animals?

Glycogen.

Where is glycogen mainly stored in animals?

Liver and muscle cells.

What is cellulose?

A structural polysaccharide that makes up much of plant cell walls.

Why can't humans digest cellulose?

Humans lack the enzyme needed to break its beta-1,4 glycosidic bonds.

What is chitin?

A nitrogen-containing polysaccharide found in arthropod exoskeletons and fungal cell walls.

What is the difference between starch and glycogen?

Both store glucose, but glycogen is more highly branched than starch.

What is the function of cellulose?

It provides structural support to plant cells.

What are lipids?

A diverse group of mostly nonpolar, hydrophobic molecules.

Why are lipids hydrophobic?

They contain many nonpolar carbon-carbon and carbon-hydrogen bonds.

What are four major types of lipids?

Fats, phospholipids, steroids, and waxes.

What are the main functions of fats?

Long-term energy storage, insulation, and protection.

What are the two main components of a fat?

Glycerol and fatty acids.

What is a triglyceride?

A lipid made of one glycerol molecule and three fatty acids.

What is an ester linkage?

The covalent bond formed between glycerol and a fatty acid.

What is a saturated fatty acid?

A fatty acid containing only single carbon-carbon bonds.

What is an unsaturated fatty acid?

A fatty acid containing one or more carbon-carbon double bonds.

What is a monounsaturated fatty acid?

A fatty acid containing one carbon-carbon double bond.

What is a polyunsaturated fatty acid?

A fatty acid containing two or more carbon-carbon double bonds.

Why are saturated fats usually solid at room temperature?

Their straight fatty acid chains pack closely together.

Why are unsaturated fats usually liquid at room temperature?

Double bonds create bends that prevent the fatty acid chains from packing tightly.

What is a phospholipid?

A lipid made of glycerol, two fatty acids, and a phosphate-containing group.

Why are phospholipids important?

They form the basic structure of cell membranes.

What does amphipathic mean?

Having both a hydrophilic region and a hydrophobic region.

Which part of a phospholipid is hydrophilic?

The phosphate-containing head.

Which part of a phospholipid is hydrophobic?

The fatty acid tails.

What is a steroid?

A lipid with a characteristic structure of four fused carbon rings.

What is cholesterol?

A steroid lipid that is an important component of animal cell membranes and a precursor for other steroids.

How does cholesterol affect membrane fluidity?

It helps maintain appropriate membrane fluidity by preventing the membrane from becoming too rigid or too fluid.

What are proteins?

Macromolecules made of amino acid monomers that perform many functions in cells.

What is an amino acid?

The monomer that makes up proteins.

What are the main parts of an amino acid?

An amino group, carboxyl group, hydrogen atom, and variable R group attached to a central carbon.

What determines the properties of an amino acid?

The structure and chemical properties of its R group.

How many common amino acids are used to build proteins?

20.

What is a peptide bond?

A covalent bond that joins two amino acids.

What is a polypeptide?

A chain of amino acids joined by peptide bonds.

What is protein primary structure?

The specific sequence of amino acids in a polypeptide.

What is protein secondary structure?

Local folding of a polypeptide into structures such as alpha helices and beta-pleated sheets.

What is protein tertiary structure?

The overall three-dimensional shape of a single polypeptide.

What is protein quaternary structure?

The arrangement of multiple polypeptide subunits into one functional protein.

What types of interactions help determine protein shape?

Hydrogen bonds, ionic interactions, hydrophobic interactions, and disulfide bonds.

What is a disulfide bond?

A strong covalent bond formed between the sulfur atoms of two cysteine amino acids.

What is denaturation?

The loss of a protein's normal shape and function due to changes in conditions such as temperature or pH.

Why is protein shape important?

A protein's shape determines how it interacts with other molecules and therefore its function.

What are major functions of proteins?

Enzymatic activity, transport, structure, movement, defense, signaling, and storage.

What is an enzyme?

A protein that acts as a biological catalyst and speeds up chemical reactions.

What is the active site of an enzyme?

The region of the enzyme where the substrate binds and the reaction occurs.

What are nucleic acids?

Macromolecules that store, transmit, and help express genetic information.

What are the two types of nucleic acids?

DNA and RNA.

What is the monomer of nucleic acids?

A nucleotide.

What are the three parts of a nucleotide?

A five-carbon sugar, a phosphate group, and a nitrogenous base.

What is the sugar in DNA?

Deoxyribose.

What is the sugar in RNA?

Ribose.

What are the nitrogenous bases in DNA?

Adenine, thymine, cytosine, and guanine.

What are the nitrogenous bases in RNA?

Adenine, uracil, cytosine, and guanine.

Which base replaces thymine in RNA?

Uracil.

What are purines?

Nitrogenous bases with two carbon-nitrogen rings: adenine and guanine.

What are pyrimidines?

Nitrogenous bases with one ring: cytosine, thymine, and uracil.

What is the structure of DNA?

A double helix made of two nucleotide strands.

What is the structure of RNA?

Usually a single-stranded nucleic acid.

What holds the two DNA strands together?

Hydrogen bonds between complementary nitrogenous bases.

What bases pair together in DNA?

Adenine pairs with thymine, and cytosine pairs with guanine.

What bases pair together in RNA?

Adenine pairs with uracil, and cytosine pairs with guanine.

What is complementary base pairing?

The specific pairing of nitrogenous bases: A with T in DNA and C with G.

What is the function of DNA?

It stores hereditary genetic information.

What is the function of RNA?

It helps use genetic information to make proteins.

What is a phosphodiester bond?

A covalent bond that connects nucleotides together in a nucleic acid strand.

What is the difference between DNA and RNA?

DNA contains deoxyribose and thymine and is usually double-stranded; RNA contains ribose and uracil and is usually single-stranded.