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65 terms

CHAP 4

STUDY
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All of the genetic material in all living organisms is made from these basic building blocks of nucleotides.
Phosphate group, 5- carbon sugar, nitrogenous base
Identify three possible components of a DNA nucleotide.
deoxyribose, phosphate group, thymine
difference between ribonucleotides and deoxyribonucleotides
Ribonucleotides have a hydroxyl group bonded to their 2' carbon; deoxyribonucleotides have an H at the same location
The condensation reaction that forms nucleic acid polymers occurs between a _____ group on one nucleotide and a _____ group on a second nucleotide
phosphate, hydroxyl
In a nucleic acid polymer, the hydrogen bonds that help to hold regions of double-strandedness together occur between what parts of the nucleotide monomers?
nitrogenous bases
Nucleic acids are polymers made up of which of the following monomers?
nucleotides
Which of the following includes all of the pyrimidines found in RNA and/or DNA?
cytosine, uracil, and thymine
When nucleotides polymerize to form a nucleic acid _____.
a covalent bond forms between the sugar of one nucleotide and the phosphate of a second
Some viruses consist only of a protein coat surrounding a nucleic acid core. If you wanted to radioactively label the nucleic acids separately from the protein, you would use _____.
radioactive phosphorus
What is radioactive phosphorus?
...
What is gel electrophoresis used for?
to separate macromolecules by size or charge
DNA is composed of building blocks called _____.
nucleotides
In eukaryotic cells DNA has the appearance of a _____.
double helix
Which structure is not a component of a nucleotide?
Sulfhydryl Oxygen group
Which of the following statements about nucleotide structure is false?
The phosphate group is bonded to the nitrogenous base.
True or false? Guanine and uracil are examples of nitrogenous bases.
True
Which linkage forms the backbone of a nucleic acid?
A sugar-phosphate linkage
Which of the following statements about DNA structure is true?
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other
What is the complementary DNA sequence to 5' ATGCATGTCA 3'?
5' TGACATGCAT 3'
When double-stranded DNA is heated to 95°C, the bonds between complementary base pairs break to produce single-stranded DNA. Considering this observation, is the strand separation step required for replication of the Double Helix an endergonic or exergonic reaction? Why?
Endergonic. An input of energy is required
If a segment of DNA contains 28 percent T nucleotides, then the percentage of A nucleotides in that segment will be _____.
28 percent
Which of the following best describes DNA's secondary structure?
double antiparallel helical strands
In the context of chemical evolution, DNA's structure is interesting because it suggests a possible copying mechanism. What about DNA's structure facilitates copying?
The strands of the double helix are complementary.
Although DNA is the main hereditary material in all life-forms, it lacks one important characteristic of being a candidate for the first life-form. Why have researchers rejected the idea that DNA was found in the first life-form?
It does not function as a catalyst
A segment of nucleic acid that contains the sugar ribose and the nitrogenous bases A, G, U, and C would be called _____.
ribonucleic acid (RNA)
An RNA molecule that can catalyze chemical reactions is called a(n) _____.
ribozyme
Which of these scientists was not directly involved in the discovery of DNA's structure?
Sidney Altman
Who was directly involved in the discovery of DNA's structure?
Francis Crick
Rosalind Franklin
Maurice Wilkins
James Watson
RNA and proteins combine in cells to form structures called ribosomes. Ribosomes contain the active site for peptide bond formation. Based on their chemical structures, do you think protein or RNA molecules actually form the active site within the ribosome?
It could be either, because both molecules have catalytic properties.
Why do researchers think the first self-replicating molecule was RNA?
RNA has the capacity to provide a template and is known to catalyze reactions (although no existing self-replicating molecules of RNA have been discovered).
Many researchers who study the origin of life propose that the first life-form capable of templating its own replication and catalyzing self-replication was made of _____.
RNA
The work of Bartel's group on the ribozyme RNA replicase supports which conclusion?
An RNA world could produce molecules that could self-replicate
If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching strand?
3'-TAAACG-5'
If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain?
75; 100 nucleotide pairs are a total of 200 nucleotides. Because of base pairing, if there are 25 adenine there must also be 25 thymine. This leaves 200-50 = 150 nucleotides to be divided evenly between guanine and cytosine.
The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases.
hydrogen bonds; Nitrogenous base pairs are joined by hydrogen bonds.
A nucleotide is composed of a(n) _____.
phosphate group, a nitrogen-containing base, and a five-carbon sugar
Teeth and bones are made up of calcium phosphate crystals. Sometimes, fluoride ions interact with these crystals. The best way to determine the three-dimensional arrangement of the crystals and fluoride ions is to use _____.
X-ray diffraction; X-ray crystallography provides information about molecular structures.
What is X-Ray diffraction?
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A scientist is studying the arrangement of neurons and glial cells in brain tissue. She labeled structures with specific fluorescent tags. Which technique would provide the best spatial images of the tissue?
confocal microscopy; Confocal microscopy is used to produce three-dimensional images of tissues
What is confocal microscopy?
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An entomologist is comparing the minute surface structures on beetle antennae from various species. Which microscope would give him the greatest resolution?
scanning electron microscopy; SEM would provide the best detail on the antennal structures
What is scanning electron microscopy?
...
You are collecting information on Paramecium swimming motions in various solutions. Which type of microscope should you use?
compound light microscope; With this microscope, the Paramecium motions can be seen.
This figure illustrates the structural similarities and differences between eukaryotic and prokaryotic cells. What type of microscope was used to produce the images?
transmission electron microscope; The details inside the cells are visible by TEM; these include membranes and organelles.
What is a transmission electron microscope?
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Which statement is most accurate regarding similarities and differences between proteins and nucleic acids?
Proteins and nucleic acids both have a backbone and are formed by condensation reactions
Semi-conversative replication
means that half of the helical structure is old and the other half is new
Why would have DNA came after RNA?
DNA is more stable due its double-helices
Primary Structure of DNA
sequence of deoxyribosenucleotides; bases include adenine, thymine, cytosine, and guanine
Secondary Structure of DNA
Two anti-parallel strands twist into a double helix, stabilized by hydrogen bonding between complementary bases (A-T & G-C) and hydrophobic interactions.
Tertiary structure of DNA
None
Quaternary Structure of DNA
None
Primary structure of RNA
sequence of ribonucleotides; include A, U, G, C
Secondary structure of RNA
most common are hairpins, formed when a single strand folds back on itself to form a double-helix "stem" and a single-stranded "loop"
Tertiary structure of RNA
folds that form distinctive three-dimensional shapes.
Quarternary Structure of RNA
associations between several RNA molecules
first step of RNA synthesis
complementary bases are added to 3' end of growing strand and polymerize.
second step of RNA synthesis
continued base pairing and polymerization form a complete complementary strand
third step of RNA synthesis
complementary and template strands separate, forming independent molecules
what are substrates?
reactants
first step of enzyme action
Initiation: Reactants bind to the active site in a specific orientation
second step of enzyme action
transition state facilitation:interactions between enzyme and substrate lower the activation energy required.
third step of enzyme action
termination: products have lower affinityfor active site and are released. Enzyme is unchanged after the reaction.
Competitive inhibition
is when another molecule with a similar shape to the substrate occupying the activate site
enzymes lower activation energy
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