Biological Macromolecules (College Board AP® Biology): Flashcards
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Define monomer.
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Define monomer.
Monomer is a small molecule that is a repeating unit; many monomers join together to build a polymer.
Define polymer.
Polymer is a large molecule made of many repeated monomers joined together, often called a macromolecule in biology.
Name the monomer that builds each of these polymers: polysaccharides, proteins, and nucleic acids.
Polysaccharides → monosaccharides
Proteins → amino acids
Nucleic acids → nucleotides
Define hydrolysis.
Hydrolysis is a chemical reaction that breaks covalent bonds by adding water, splitting a larger molecule into smaller molecules.
In a hydrolysis reaction, how are the parts of the water molecule added to the monomers?
The hydrogen ion from the water is added to one monomer.
The hydroxyl group from the water is added to the other monomer.
Define dehydration synthesis.
Dehydration synthesis is a chemical reaction that forms a covalent bond, joining two smaller molecules and releasing a molecule of water.
In a dehydration synthesis reaction, what is removed from the two monomers?
A hydrogen ion is removed from one monomer.
A hydroxyl group is removed from the other monomer.
Together these form the water molecule that is released.
The joining of many monomers by dehydration synthesis to form a polymer is called .
The joining of many monomers by dehydration synthesis to form a polymer is called polymerization.
True or False?
Dehydration synthesis releases a molecule of water, while hydrolysis uses a molecule of water.
True.
Dehydration synthesis joins monomers and gives off water; hydrolysis adds water to break a bond.
True or False?
Hydrolysis builds polymers from monomers.
False.
Hydrolysis breaks down polymers into smaller molecules. Dehydration synthesis builds polymers from monomers.
Define nucleotide.
Nucleotide is the monomer of nucleic acids; many nucleotides join together to form a polynucleotide such as DNA or RNA.
What are the three structural components of a nucleotide?
A five-carbon (pentose) sugar
A phosphate group
A nitrogenous base
Which nitrogenous bases are found in DNA and which in RNA?
DNA: adenine, thymine, cytosine, guanine
RNA: adenine, uracil, cytosine, guanine (uracil replaces thymine)
What defines the 3′ end and the 5′ end of a nucleic acid strand?
The 3′ end has a terminal hydroxyl (–OH) group on carbon 3 of the sugar.
The 5′ end has a terminal phosphate group on carbon 5 of the sugar.
During nucleic acid synthesis, new nucleotides are always added to the of the growing strand.
During nucleic acid synthesis, new nucleotides are always added to the 3′ end of the growing strand.
What type of bond forms between nucleotides as a strand is built?
A strong covalent bond forms between the nucleotides of the growing strand.
DNA is structured as an antiparallel , with two strands running in opposite 5′ to 3′ orientations.
DNA is structured as an antiparallel double helix, with two strands running in opposite 5′ to 3′ orientations.
Which bases pair together in DNA, and what holds the pairs together?
Adenine pairs with thymine (A–T) and cytosine pairs with guanine (C–G).
The base pairs are held together by hydrogen bonds.
When RNA folds and base-pairs, which base pairs with adenine instead of thymine?
Uracil pairs with adenine (A–U).
Cytosine still pairs with guanine (C–G), as in DNA.
Give three structural differences between DNA and RNA.
DNA has the sugar deoxyribose; RNA has ribose
DNA contains thymine; RNA contains uracil
DNA is typically double-stranded; RNA is typically single-stranded
True or False?
DNA and RNA are polymers of bases.
False.
DNA and RNA are polymers of nucleotides. Describing them as polymers of bases is a common error.
Define amino acid.
Amino acid is the monomer of proteins, joining in linear chains to form polypeptides.
What four groups are covalently bonded to the central carbon atom of an amino acid?
A hydrogen atom
A carboxyl group (–COOH)
An amine group (–NH₂)
A variable R group
Define peptide bond.
Peptide bond is the covalent bond that forms between the carboxyl group of one amino acid and the amine group of the next, joining them in a chain.
Which two functional groups react to form a peptide bond, and what type of reaction is it?
The carboxyl group (–COOH) of one amino acid reacts with the amine group (–NH₂) of the next.
It is a dehydration synthesis reaction, so water is released.
What are the three possible chemical properties of an amino acid's R group?
Hydrophobic / nonpolar
Hydrophilic / polar
Ionic
True or False?
The interactions between R groups determine the structure and function of that region of the protein.
True.
The chemical properties of the R groups, and how they interact, shape the protein and so determine its function.
The specific sequence of amino acids in a protein is called its structure.
The specific sequence of amino acids in a protein is called its primary structure.
How does the secondary structure of a protein form?
From local folding of the amino acid chain, caused by hydrogen bonding along the polypeptide backbone.
This forms shapes such as α-helices and β-pleated sheets.
Which types of interaction produce the tertiary structure of a protein?
Hydrogen bonds
Hydrophobic interactions
Ionic interactions
Disulfide bridges
Define quaternary structure.
Quaternary structure is the level of protein structure that arises from interactions between multiple polypeptide chains, e.g. in hemoglobin.
All levels of protein structure together determine the function of a protein.
All four levels of protein structure together determine the function of a protein.
True or False?
A single change in the primary structure of a protein can affect its function.
True.
The primary structure is specific to each protein; altering one amino acid in the sequence can change the protein's shape and therefore its function.
Give three examples of the roles proteins perform in cells.
Any three of: enzymes, hormones, transport proteins (e.g. hemoglobin), structural proteins (e.g. keratin, collagen), contractile proteins (e.g. myosin), and membrane or immune proteins.
Define monosaccharide.
Monosaccharide is a simple sugar, the monomer unit from which carbohydrates are built.
Define polysaccharide.
Polysaccharide is a complex carbohydrate made of many monosaccharides joined by covalent bonds; it may be linear or branched.
How do monosaccharides join together to form a polysaccharide?
By dehydration synthesis: a covalent bond forms between two monomers and a molecule of water is released.
This repeats many times to build the polysaccharide.
Complex carbohydrates can be either linear or in shape.
Complex carbohydrates can be either linear or branched in shape.
What determines the properties and function of a carbohydrate?
The type of monomer it is built from, and the nature of the covalent bonds joining the monomers together.
What is the function of cellulose, and where is it found?
Cellulose is a structural polysaccharide.
It is found in plant cell walls, where it provides strength.
Which polysaccharides are used for energy storage in plants and in animals?
Starch is the storage polysaccharide of plants
Glycogen is the storage polysaccharide of animals (and fungi)
True or False?
Cellulose and starch have different functions because they have different structures.
True.
Structure determines function: cellulose is structural while starch is a storage molecule, even though both are polysaccharides of glucose.
True or False?
Monosaccharides are the monomers of polysaccharides.
True.
Monosaccharides (simple sugars) join by covalent bonds to form polysaccharides (complex carbohydrates).
What type of bond joins monosaccharides together in a polysaccharide?
A covalent bond, formed by dehydration synthesis.
Monosaccharides are the monomers of carbohydrates and are also known as sugars.
Monosaccharides are the monomers of carbohydrates and are also known as simple sugars.
Why are lipids described as nonpolar and hydrophobic?
Their structure means they do not carry regions of charge, so they are not attracted to water and do not dissolve in it.
Define saturated fatty acid.
Saturated fatty acid is a fatty acid whose hydrocarbon chain contains only single bonds between the carbon atoms.
Define unsaturated fatty acid.
Unsaturated fatty acid is a fatty acid whose hydrocarbon chain contains at least one carbon–carbon double bond, which causes the chain to kink.
The double bonds in an unsaturated fatty acid cause the carbon chain to .
The double bonds in an unsaturated fatty acid cause the carbon chain to kink.
Why are saturated fats solid at room temperature while unsaturated fats are liquid?
Saturated fatty acid chains are straight, so they pack together tightly → solid.
Unsaturated chains are kinked, so they cannot pack together tightly → liquid.
True or False?
The more double bonds a fatty acid has, the more liquid the lipid is at room temperature.
True.
More double bonds means more kinks, so the chains pack together less tightly and the lipid is more liquid at room temperature.
Give two functions of fats in living organisms.
Energy storage and support of cell function
Thermal insulation, e.g. to help keep mammals warm
What is the function of steroids as a class of lipid?
Steroids are hormones.
They support physiological functions including growth and development, energy metabolism, and homeostasis.
The lipid provides essential structural stability to animal cell membranes.
The lipid cholesterol provides essential structural stability to animal cell membranes.
What is the role of phospholipids in cells?
Phospholipids group together to form the lipid bilayers found in plasma and cell membranes.
True or False?
All lipids function only as long-term energy stores.
False.
Lipids have varied functions: energy storage and insulation (fats), acting as hormones (steroids), membrane stability (cholesterol), and forming membranes (phospholipids).
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