chapter 3 bio 101
Which describes purines?
They are double-ring molecules. They are nitrogenous bases. They are found in both DNA and RNA.
Which of the following describes stereoisomers?
They are identical in terms of which atoms are bonded to each other, but differ in the spatial arrangement of their atoms. They have the same number and types of atoms.
Which of the following describes the D and L forms of an organic molecule?
They are mirror images of each other. They differ in how they rotate a plane of polarized light. They are enantiomers.
Which of the following statements about monosaccharides are true?
They are often used as building blocks to form larger carbohydrates. Because they have many C--H bonds, they are well suited for energy storage. They may contain as few as 3 carbon atoms.
Choose all statements that describe pyrimidines?
They are single-ring molecules. They are nitrogenous bases They include cytosine, thymine, and uracil.
Which describes denatured proteins?
They are usually inactive.
Which of the following is a common feature of DNA and RNA?
They both have a sugar-phosphate backbone
Select all statements that are true about structural isomers.
They differ in the actual structure of their carbon skeleton. They are composed of the same number and type of atoms. They have the same molecular formula.
Which describes functional groups?
They may be acidic or basic. They give definite chemical properties to the molecules to which they are attached They are small molecular groups that are attached to larger molecules. They may be polar or nonpolar.
Which of the following are functions of proteins?
They play a key role in the contraction of muscles. They can store ions, such as calcium and iron. They provide structural support for many animal tissues. They transport ions and molecules across cell membranes.
Of the following list, choose the functions of proteins in living cells.
They transport oxygen in the blood of vertebrates. They help the body recognize and destroy foreign microbes and cancer cells. They catalyze chemical reactions. They play a key role in moving materials within cells.
Changes in a protein's shape can alter its ability to function or even cause it to become completely inactive.
True
How can some organisms derive energy from cellulose even though they cannot produce the enzymes needed to digest it?
The necessary enzymes are produced by bacteria and protists that live in their digestive tract.
How are disaccharides formed?
Two monosaccharides are linked together through dehydration synthesis.
In the absence of other information, you can predict that an organic molecule with the empirical formula of C12H24O12 is a
carbohydrate
A molecule that has mirror-image versions is called a
chiral
is the structural carbohydrate found in many fungi and in arthropods.
chitin
Organic molecules with the same molecular formula may exist in different forms called
isomers
What is the primary structure of a protein?
sequence of amino acids in a polypeptide chain
Which of the following statements about enantiomers are true?
-They have the same carbon skeleton but differ in how the groups attached to the skeleton are arranged in space. -They are mirror images of each other.
A scientist determined the following information about a polypeptide: (1) it contains 35 amino acids in total, (2) it only contains 14 of the 20 common amino acids. How many different amino acid sequences are possible for this polypeptide?
14^35
Although many different amino acids occur in nature, only
20
Proteins are polymers made up of how many different amino acids?
20
If a polypeptide consists of 90 amino acids, how many different amino acid sequences are possible?
20^90
Which of the following accurately describes the chemical structure of a typical amino acid found in a protein?
A central carbon atom is bound to an amino group, carboxyl group, a side chain, and a hydrogen atom.
When a carbohydrate is formed by linking two monosaccharides by a condensation reaction, we get water plus which of the following?
A disaccharide
During a hydrolysis reaction which of the following occur?
A large molecule is broken down into 2 smaller molecules. An H atom is attached to one molecule and an -OH group is attached to another molecule.
Select the characteristics of a hydrolysis reaction.
A large molecule is broken down into two smaller molecules. Water is added to the reaction.
What is the difference between a polypeptide and a protein?
A protein is composed of one or more long, unbranched chains of amino acids, while a polypeptide is a single, long, unbranched chain of amino acids.
What are the isomeric forms of amino acids?
Amino acids have two enantiomers, the L and D forms.
Biological polymers are often made using dehydration (or condensation) reactions. During these dehydration reactions which of the following occur?
An H atom is removed from one molecule and an -OH group is removed from another molecule. A molecule of water is removed. Two separate molecules are joined together by a covalent bond.
In humans, how is glucose transported in the blood?
As a simple monosaccharide
Where are the peptide bonds located in a polypeptide?
Between the amino group of one amino acid and the carboxyl group of another
Although scientists generally recognize
Blank 1: 4 or four Blank 2: quaternary
In cells, DNA serves as a template for the synthesis of
Blank 1: RNA, mRNA, messenger RNA, or ribonucleic acid Blank 2: proteins or polypeptides
The two basic types of secondary structure are
Blank 1: alpha Blank 2: beta, beta-pleated, or beta pleate
The two major functional groups found in all amino acids are the basic
Blank 1: amino Blank 2: carboxyl
In addition to a pentose and a phosphate group, nucleotides contain a
Blank 1: nitrogenous Blank 2: base
The twenty common amino acids are grouped into the following 5 chemical classes:
Blank 1: nonpolar Blank 2: polar Blank 3: aromatic
Depending on the orientation of adjacent sections of a polypeptide, β sheets can be
Blank 1: parallel Blank 2: antiparallel
refers to a single, unbranched chain of amino acids, while a(n)
Blank 1: polypeptide Blank 2: protein
The two types of nitrogenous bases present in nucleotides are
Blank 1: purines Blank 2: pyrimidines
How are starch and glycogen similar?
Both are largely insoluble in water. Both are storage polysaccharides. Both are composed of α-glucose subunits.
How are starches and cellulose similar?
Both are polysaccharides. Both are insoluble.
Which of the following bonds is essentially nonpolar?
C--H
Identify the two major classes of nucleic acids.
DNA and RNA
Which type of interaction involves the formation of a covalent bond between two different amino acid side chains?
Disulfide bridge
Which of the following are six-carbon sugars?
Galactose Fructose Glucose
Which of the following are common monosaccharides found in nature?
Glucose Fructose Galactose
Which polysaccharides function primarily to store energy?
Glycogen Amylose Amylopectin
How are starch and cellulose different?
Most organisms do not produce the enzymes needed to digest cellulose. Only starch functions primarily for energy storage. Starch is composed of α-glucose chains and cellulose is composed of β-glucose chains. Only starch is composed of α-glucose subunits.
Protein denaturation may be caused by an increase in which of the following?
Ionic concentration Temperature pH
Which of the following describes chitin?
It is a polymer of N-acetylglucosamine, a substituted version of glucose. It is found in the exoskeleton of arthropods and the cell wall of fungi. It is cross-linked by proteins to form a tough structural material.
In most plants, how is glucose transported from one part of the plant to another?
It is combined with another monosaccharide to form a disaccharide.
Select all the characteristics of cellulose.
It is composed of β-glucose subunits. It forms long fibers that are strong and resistant to digestion by most animals. It is the main component of plant cell walls.
If the interactions that maintain the 3-dimensional shape of a protein are disrupted so that the polypeptide chains completely unfold, how is this protein described?
It is denatured.
Choose the features of glycogen.
It is similar to amylopectin. It has a longer average chain length than pant starches.
Which of the following are disaccharides?
Maltose Sucrose Lactose
Which of the following describe monosaccharides?
Monosaccharides are composed of carbon, hydrogen, and oxygen. Monosaccharides are the simplest carbohydrates.
Why does cellulose work well as a structural material?
The long unbranched β-linked chains of cellulose can make very tough fibers.
Which of the following molecules have the ability to serve as templates to produce precise copies of themselves?
Nucleic acids
What type of bond forms between two amino acids during dehydration synthesis?
Peptide bond
What are the three basic components of a nucleotide?
Phosphate group Nitrogenous base Pentose sugar
Carbon-oxygen and carbon-nitrogen bonds are described as which of the following?
Polar covalent Formed by an unequal sharing of electrons
What are the three major structural components of an amino acid?
Side chain (R) Carboxyl group Amino group
From the list below, select all that are polysaccharides.
Starch Glycogen Cellulose
What is a main difference between starch and glycogen?
Starch is found in plant cells and glycogen is found in animal cells.
Six-carbon sugars can exist in two forms depending on whether they are dissolved in water or not. What are those two forms?
Straight chain Ring
The tertiary structure of a protein is determined primarily by interactions involving which of the following?
The R groups of the amino acids
Which part of an amino acid is always acidic?
The carboxyl group
How are the nucleotides in a single polynucleotide chain linked together?
The phosphate group of one nucleotide is covalently linked to the sugar of the next nucleotide.
The 20 common amino acid are classified into five chemical classes based on which of the following?
Their R groups
The unique properties of the 20 common amino acid are determined by which of the following?
Their R groups
When a six-carbon sugar is dissolved in water, it generally forms
a ring.
Glucose can exist in two forms depending on the orientation of the carbonyl groups in its ring form. These two forms are
alpha and beta glucose.
What are the building blocks of proteins?
amino acids
When two amino acids are linked together, a peptide bond is formed between the
amino, carboxyl
Most plant starch is composed of α-glucose subunits linked together in branched chains called
amylopectin
A starch that is composed of α-glucose subunits linked together in unbranched chains is
amylose
The two enantiomeric forms of amino acids are the
d, l
When two amino acids are linked, an -OH group is removed from one of the molecules, and a hydrogen atom is removed from the other molecule. This type of reaction is called
dehydration.
Changes in a protein's environment can cause the protein to unfold and lose its shape in a process called
denaturation.
Two amino acids joined together by a peptide bond form a(n)
dipeptide
True or false: Protein structure is usually not affected by changes in the temperature, pH, or ionic concentration of the surrounding solution.
false
The simplest carbohydrates are called
monosaccharides
unique among macromolecules, _____________________ acids are able to serve as templates to produce precise copies of themselves
nucleic
The building blocks of nucleic acids are monomers called
nucleotides
A polypeptide can have several adjacent sections that exhibit a β sheet secondary structure. Depending on their orientation, the β sheets can be
parallel or antiparallel.
The 5' end of a nucleotide chain is composed of a(n)
phosphate group.
A long molecule built by linking together a large number of small, similar molecules termed monomers is a(n)
polymer.
Long polymers made of monosaccharides that have been linked through dehydration synthesis constitute a type of macromolecules generally known as
polysaccharides
The way two or more polypeptides fit together to form the final overall shape of a protein is called
quaternary
When a protein is made of two or more polypeptide chains, the overall arrangement of those polypeptide chains is called
quaternary
Individual polypeptides within a protein are referred to as the protein's
subunits
structure is determined by how regions with secondary structure are arranged in space to produce the final overall shape of each polypeptide chain.
tertiary
Altering the sequence of amino acids in a polypeptide chain by just a single amino acid can have drastic effects on
the protein's function.
A particular enzyme usually recognizes only a single specific stereoisomer
true
True or false: If the sequence of amino acids in a polypeptide chain is altered by a single amino acid, this could have drastic effects on both the shape and function of a protein.
true
The protein hemoglobin is made of
two α-chain subunits and two β-chain subunits.
What are the two basic types of secondary structure in proteins?
α- helix and β-pleated shee