Nucleic Acid And Protein Synthesis Flashcards
What are the key features of DNA in living organisms?
The ability to store information - the information needed is a set of instructions for controlling the behavior of cells.
The ability to copy itself accurately-whenever a cell divides it must pass on exact copies of the “genetic material’ to each of its daughter cells so no information is lost.
Define a nucleotide.
A molecule consisting of a nitrogen containing base, pentose sugar and a phosphate group. The monomers from which DNA and RNA molecules are made up of are nucleotides.
Define a polynucleotide.
A chain of nucleotides joined together by phosphodiester bonds. DNA and RNA are examples of poly nucleotides.
What are nucleic acids?
Nucleic acids are biological organic molecules that control all processes in the cell. Together the macromolecules DNA and RNA are known as nucleic acids.
What are the four nitrogen containing bases found in DNA and RNA?
DNA-adenine, thymine, guanine, cytosine
RNA-adenine, uracil, guanine, cytosine
Describe the difference in the structure of nitrogenous bases.
Adenine and guanine are purines whereas the other three bases thymine, cytosine and uracil are pyrimidines. Purine has two rings in its structure. pyrimidine has one ring. Two purines cannot bind together as it will be larger molecules than pyramids and there is just enough room between the two sugar phosphates for one purine and one pyramidine base molecule.
What is a pentose sugar?
Five carbon atoms are called pentoses. Two pentoses are found in nucleic acids. Ribose and deoxyribose. Nucleic acid containing ribose is RNA. One containing deoxyribose is DNA. As the name suggests deoxyribose is almost the same as ribose except it has one fewer oxygen atom in its molecule. The carbon atom one is attached to a nitrogenous base.
What molecule gives the nucleic acids their acidic nature?
Phosphoric acid is the source of the phosphate group (PO4-) so it gives nucleic acids their acidic character. The phosphate group is used to link molecules of pentose sugars by condensation reactions to form the sugar phosphate backbone of nucleic acids by forming 3, 5 phosphate bonds.
Describe the structure of ATP.
ATP is not part of DNA or RNA but it is very similar to a nucleotide. (Book says it is a nucleotide). ATP is made up of three components: adenine, ribose and phosphate.
What is adenosine?
Adenine plus ribose forms a sugar base called adenosine. Adenosine can be combined with one, two or three phosphate groups to give in turn adenine monophosphate (AMP), adenosine diphosphate (ADP) or adenosine triphosphate (ATP). Do not confuse adenosine with adenine and thymine with thiamine (a vitamin).
What is a dinucleotide molecule?
The molecule formed by joining two nucleotides is called a dinucleotide. The bond formed is called a phosphodiester bond. The term diester is used because the phosphate group involved now has two extra bonds, one to each of the sugars it is connected to. The sugars and phosphates are linked by phosphodiester bonds to form a backbone from which the bases stick out sideways at right angles to the backbone.
What is the DNA structure held together by?
DNA molecules are made up of two polynucleotide strands lying side by side running in opposite directions. Each chain is a right-handed helix. The two chains coil around each other to form a double helix. The chains run in opposite directions (5’ to 3’) and (3’ to 5’).
Which bonds are involved in the structure of the DNA molecule and what are their functions?
Each polynucleotide chain has a sugar phosphate backbone made up of phosphodiester bones with bases projecting at right angles.
The bases in one chain are attracted to the bases of the other chain by hydrogen bonding between the bases. This holds the chains together.
What is complementary base pairing?
The hydrogen bonding of A with T in DNA or A and U in RNA and of C with G in both DNA and RNA. A links with T by two hydrogen bonds. C links with G by three hydrogen bonds. Because the bases are complementary the sequence of bases in one strand determines the sequence of bases in the other strand. Adenine and uracil have two hydrogen bonds between them.
When does a complete turn of the double helix take place?
A complete turn of the double helix takes place every 10 base pairs.
What are the three types of RNA?
mRNA-messenger RNA
tRNA-transfer RNA
rRNA-ribosomal RNA.
Transfer RNA and ribosomal RNA fold up into complex structures but messenger RNA remains as an unfolded strand.
What is meant by an antiparallel strand?
Antiparallel means one strand ends with 3 prime whereas the complementary strand has 5 prime.
What are the similarities between RNA and DNA?
- Both are polynucleotides and macromolecules
- Both can be found in the nucleus
- Both contain sugar phosphate backbone
- Both contain nitrogenous bases (cytosine, guanine and adenine ).
- The sugars are linked to phosphate groups at one end and nitrogen base at the other end.
- Both have phosphodiester bones.
What are the differences between RNA and DNA?
DNA has two polynucleotides strands whereas RNA has a single polynucleotide strand.
DNA is a double helix structure whereas RNA is not a helix structure and is just as straight chain.
DNA is a deoxyribose and the carbon number two attaches to a hydrogen whereas in ribose sugar the carbon at the number two attaches to OH.
In DNA there is a thymine base and no uracil whereas in RNA there is uracil and no thymine.
In DNA there was hydrogen bonding between all bases whereas in RNA there is either none or some hydrogen bonding between some bases.
In DNA the ratio between A and G and C to T is equal to 1 whereas in RNA the ratio between A to G and c to u varies.
DNA is a longer molecule than RNA.
RNA is of three types whereas DNA is only of one type.
During which phase of the cell cycle does the DNA replicate?
DNA replicates during the s phase of the cell cycle.
What is replication controlled by?
Replication is controlled by enzymes.
What is DNA replication?
Every time a cell undergoes cell division all of its DNA is copied. This process is called DNA replication.
What is the first stage in DNA replication?
In the first stage the enzyme DNA helicase attaches to the DNA molecule. DNA helicase causes the hydrogen bonds between complementary bases to break. This causes the two polynucleotide strands to separate from each other. (This is the unzipping).
What is the second stage in DNA replication?
In the second stage free nucleotides(from the cytoplasm) line up there were complimentary bases on the DNA strands. At this stage the free nucleotides are only held together by hydrogen bonds between the complementary bases. They are not bonded to each other by phosphodiester bonds. At this stage a second enzyme now attaches. This enzyme is called DNA polymerase. DNA polymerase moves down the molecule and
What is semi-conservative replication?
Each of the single polynucleotide DNA strands acts as a template for the formation of a new strand - the original strand and the new strand then join together to form a new DNA molecule. This method of replicating DNA is called semi-conservative replication because half of the original DNA molecule is kept (conserved) in each of the two new DNA molecules.
What is the role of DNA polymerase?
What are activated nucleotides or nucleoside triphosphates?
In the nucleus there are free nucleotides to which two extra phosphates have been added. These free nucleotides with three phosphate groups are known as nucleoside triphosphates or activated nucleotides. The extra phosphate activates the nucleotides enabling them to take part in DNA replication.
What is the role of DNA polymerase?
A molecule of DNA polymerase attaches to each of the single template strands. It adds one new nucleotide at a time which is held by hydrogen bonding to the strand being copied. DNA polymerase can only copy in the 5 to 3 direction along each strand. DNA polymerase simply follows the unwinding process, copying the DNA as it is unwound.
