Nucleotides and nucleic acids And Enzymes Flashcards
What is a nucleotide made from?
Pentose sugar, nitrogenous base and a phosphate group
What are ATP and ADP and what are they used for?
Nucleotides used to store and transport energy in cells
What are the 2 purines?
Adenine and Guanine
What are the 3 pyrimidines?
Cytosine, Thymine and Uracil
What base does uracil replace?
Thymine
What is an RNA molecule made up of?
A single polypeptide chain
How do you phosphorylate a nucleotide?
Add one or more phosphate to it
What is ATP made from?
Adenine, ribose and 3 phosphates
What is ADP made from?
Adenine, ribose and 2 phosphates
How is energy in ATP/ADP released?
Bonds are broken
What do nucleotides form when joined together?
Polynucleotides
How is a phosphodiester bond formed?
Phosphate and sugart from different nucleotides form via a condensation recation
What does a chain of polynucleotides form?
A sugar-phosphate backbone
How do polynucleotides join?
Hydrogen bonds between bases
How many hydrogen bonds does C and G have?
3
How many hydrogen bonds does A and T have?
2
What does DNA helicase do? (Step 1)
Breaks hydrogen bonds and unzips DNA into 2 stands
How does the DNA sequence act as a template? (Step 2)
Free-floating nucleotides join exposed bases
How are the new DNA strands joined together with the original strands? (Step 3)
DNA polymerase
What is semi-conservative replication?
DNA replication where the final DNA molecule contains one original DNA strand and one new DNA strand
What is a gene?
A sequence of DNA nucleotides that code for a polypeptide
Where is mRNA made?
In the nucleus
what does mRNA carry?
Genetic code
Where is tRNA found?
Cytoplasm
What is an anticodon?
Three bases on the end of a tRNA molecule opposite to the amino acid
What does rRNA do?
Catalyses the formation of peptide bonds in amino acids
What does degenerate mean?
A codon can be used more than once with other codons to produce a different amino acid
What does the genetic code being universal mean?
The same base triplets code for the same amino acids in all living things
Outline the stages of transcription.
1) RNA polymerase attaches to DNA at beginning of gene
2) hydrogen bonds break
3) RNA polymerase lines up free nucleotides alongside template
4) U replaces T in complementary base pairing
5) mRNA formed
6) hydrogen bonds reform once RNA polymerase has passed
7) mRNA leaves through nuclear paws and attaches to ribosomes
Outline the stages of translation.
1) tRNA carries amino acids to a ribosome
2) TRA with anticodon complementary to start codon attaches to mRNA
3) second tRNA attaches to next codon
4) rRNA catalyses formation of peptide bonds
5) third tRNA Binds to next codon, and second tRNA MOVES AWAY
6) process continues
7) polypeptide chain moves away
What are enzymes?
Biological catalysts that speed up reactions
What does intracellular mean?
Within cells
What does extracellular mean?
Outside of cells
What is an example of an intracellular enzyme?
Catalase works inside cells to catalyse the breakdown of hydrogen peroxide
What is an example of an extracellular enzyme?
Amylase catalyses the breakdown of starch into maltose in the mouth
What type of protein are enzymes?
Globular
Define the lock and key model.
The substrate fits into the enzyme in the same way that a key fits into a lock
Defined the induced fit model
The enzyme alters the shape of its active site to fit the substrate more closely
Which theory is better, lock and key or induced fit?
Induced fit
What are the factors that affect enzyme activity?
• temperature
• pH
• enzyme concentration
• substrate concentration
How does temperature affect enzyme activity?
High temperatures means there’s more kinetic energy so there are more frequent collisions. If it gets too hot, the enzyme will denature
How does pH affect enzyme activity?
Above and below the optimum pH can break ionic and hydrogen bonds
How does enzyme concentration affect enzymes?
High concentration means more collisions
How does substrate concentration affect enzymes?
High concentration means more collisions
What a non-protein substance allows some enzymes to work
Cofactors
What do inorganic cofactors do?
Only help the enzyme and the substrate to bind together
What do organic cofactors do? What are they called?
Coenzymes that participate in the reaction and act as a second substrate
What is an enzyme inhibitor?
Molecules that bind to the enzyme and stop it from functioning
What is competitive inhibition?
They have a similar shape to the substrate and compete to bind to the active site
What is non-competitive inhibition?
Molecules bind to the allosteric site and change the shape of the active site, so the substrate cannot bind
What determines if an inhibitor can be reversed?
If it has a strong covalent bond, it cannot be reversed, if they have weaker hydrogen bonds, they can be reversed
How do anti-viral drugs stop viruses?
Reverse transcript, inhibitors prevent replication of the viral DNA
What is the metabolic pathway?
A series of connected metabolic reactions where the product of the first reaction takes part in the second reaction and so on
What is product inhibition?
Where the enzyme is inhibited by the product they produce
