Chapter Four Flashcards
What is the purpose of nucleic acids?
Storage and transmission of genetic information
within the code of DNA gives us the code for RNA/proteins - transcription is DNA to RNA - (gene expression)
what are the monomers of nucleic acids?
nucleotides
Explain the differences of nucleotides vs nucleosides
Nucleotides are made of three things, a pentose sugar, a nitrogenous base and a phosphate group
Nucleosides are made of two things, a pentose sugar and a nitrogenous base
What does transmission and storage mean in relation to nucleic acids?
The storage of genetic information means that within our code of DNA contains the instruction for transcribing into RNA then translating proteins.
How are DNA and RNA different (four ways)
DNA and RNA have different pentose sugars (deoxyribose ribose)
DNA is double stranded and RNA is single stranded
They have slightly different nucleosides (#2)
They have different pyrimidine bases DNA = C-T’s RNA = C-U’s
How do you know what carbon is which one in a sugar?
you start from the oxygen and count to the right
What are the two types of nitrogenous bases? Briefly explain their structure and explain which ones are which.
Two types are purines and pyrimidines
Purines are a double fused ring structure of six carbon and are Adenine and Guanine
Pyrimidines are a single ring six carbon structure and are Cytosine, Thymine and Uracil
Draw out the three basic parts of a nucleotide.
phosphate group attached to a penta-sugar attached to a nitrogenous base
How are nucleotides joined together and broken apart?
Condensation reaction/ hydrolysis reaction
What is a phosphodiester linkage?
the bond created when a condensation reaction happens between two nucleotides on their 5 prime and 3 prime carbons.
the phosphate group links the 5’ and 3’ carbons
Why does DNA/ RNA grow only in the 5’ to 3’ direction?
Because of the shape of the enzymes / proteins can only perform their actions in one specific direction, and generally because of its antiparallel nature
Never add a nucleotide to a five prime end, only the three prime end
Five prime end has the phosphate group and the three prime has the hydroxyl at the end of the connection
How do two strands of DNA stay together?
through the process of complimentary base pairing —- when purine base ends bond with pyrimidine base ends through hydrogen bonds to hold them together
How many hydrogen bonds between A-T? 2
How many hydrogen bonds between C-G? 3
Is base pairing only possible in DNA?
No it can also happen in RNA as it can occur between different regions and as expected it changes in 3‐D structure
What is the basic structure of DNA that we can see across the board in all species?
A double helix that has a sugar-phosphate backbone and nitrogenous base rungs
the genetic info info is carried in the base rungs
Why is base pairing between RNA/DNA so important?
because the complimentary base pairing can change the structure of the DNA or RNA and when something has its structure changed its function also changes.
base pairing between RNA and DNA is also possible, and becomes very important in transcription of DNA to RNA
Describe how an RNA nucleic acid is paired.
single strand but can fold on itself in specific regions
Why is DNA so important? (two reasons)
it encodes hereditary information from generation to generation and also duplicates itself by process of replication
It transcripts into RNA and translates in protein formation
Name three other nucleotides.
ATP - energy transfer
GTP - energy transfer in protein synthesis
cAMP - essential to action of hormones and transmission of
info in the nervous system
Describe the antiparallel nature of the DNA double helix.
the outer sugar phosphate “strands’ of DNA run anti parallel which means they run in opposite directions one has the 5’ Carbon at the top and the other has it at the bottom
Is all of our DNA transcripted? What about replicated?
It is all replicated but not all translated, about 90% is.
Difference between translation and transcription.
Transcription is a process that turns DNA into RNA
Translation is a process of RNA to Protein.
What two famous experiments that didn’t support the concept of spontaneous generation.
Redi’s meat jars (three jars, one with cheese cloth, nothing, and lid
Louis Pasteur (put nutrient medium in sterile flask and then broke one of the necks off the flask and microorganisms only showed up in one)
How old are the oldest proto cells we have found as fossils?
3.5 billion years old.
What are the two theories for how life first appeared on earth?
Chemical Evolution - conditions were conducive to form simple molecules amino acids, purines pyrimidines led to formation of simple life forms
Life outside earth - simple life forms came from a meteorite and they actually found amino acids nucleotide bases, and sugars
What came first nucleic acids, proteins or something else?
It is likely that catalytic RNA was the first (not actually RNA of what we know it as), because these parts of the macromolecules couldn’t just go together, they had to have something to speed up their reaction.
It is said that RNA could have acted as a catalyst for its own replication and synthesis of proteins
Evidence to back this up is that the 3D shape of certain RNA molecules look similar to enzymes
What are riboenzymes?
catalytic RNA’s that speed up reactions involving their own nucleotides
Evidence for an RNA world (5 things)
- the 3D shape of certain RNA molecules look similar to enzymes
- polypeptide linkages are catalyzed by riboenzymes
- enzyme called reverse transcriptase in retroviruses catalyze synthesis of DNA from RNA
- short naturally occurring RNA molecules catalyze polymerization of nucleotides in experiments
- artificial riboenzyme developed that catalyzes assembly of short RNA into larger molecules that is the exact copy of itself
Why would a membrane have been critical in the evolution of life?
because it allowed cells to compartmentalize/ concentrated and separate the internal from the external, maintaining a chemical composition different from the outside
Why do fatty acids form a lipid bilayer around a liquid compartment in water?
because the hydrophobic tails want to touch and the hydrophilic tails are drawn to the water so it naturally creates the basics of a proto cell
Explain what the first proto cell may have looked like.
A bilayer would form around a piece of RNA in water, but it would still allow small molecules to pass through like sugars and nucleotides, so that if the RNA was capable of self replication, other nucleotides could enter and be incorporated into more complex polynucleotides
What is replication?
duplication of genetic material
what is spontaneous generation?
creating life from inaniment objects/ nature
what is the Miller / Urey experiment?
their hypothesis - organic chemical compounds can be generated under conditions similar to those that existed in the atmosphere of primitive earth
Step 1. Heat chemicals to form atmosphere of methane, ammonia, hydrogen, and water vapor,
Step 2. provide energy with electrical sparks (simulating lightning)
Step 3. Cool gases in the rain contains new compounds
Step 4. Collects and analyze condensed liquid
