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What is a nucleic acid
Polymers of nucleotides which contain genetic information
How is DNA protected from mutations
By forming a double strand
What base pairs does DNA contain
Cytosine, Thymine, Guanine, Adenine
What is the function of mRNA
To transport information from nucleus to ribosomes
What is the function of tRNA
To bring the amino acid to a ribosome
What is the function of rRNA
To form part of the ribosome structure with proteins
What bases make up RNA
Adenine, Uracil, Guanine, Cytosine
What is the full name of DNA
Deoxyribonucleic acid
What is the full name of RNA
Ribonucleic acid
What is the general function of DNA and RNA
To build proteins and carry information
What is the function of DNA
To hold or store genetic information
What is the function of RNA
To transfer the genetic code from the nucleus to the ribosomes
What molecules make up a nucleotide
A pentose sugar, a nitrogen containing base and a phosphate group
Define nucleotides
Repeating monomers of DNA and RNA
What is the difference between an RNA and DNA sugar
DNA contains deoxyribose sugar with H and the second position, RNA contains ribose sugar with OH in the second position
What is the difference between DNA and RNA bases
RNA contains a uracil base instead of a thymine
Define and give examples of purines
A nitrogenous base molecules with a double ring structure, such as adenine and guanine
Define and give examples of pyrimidines
A nitrogenous base molecule with a single ring structure, such as cytosine, thymine and uracil
Describe a difference between the structure of DNA and RNA
DNA is double stranded in a double helix, RNA is relatively short single strands
What bond forms between nucleotides
A condensation reaction forms a phosphodiester bond
How can the double helix strands be described
As antiparallel strands
Describe the joining of two bases
Complementary base pairings are joined with hydrogen bonds
How many bonds does thymine and adenine have
2 hydrogen bonds
How many bonds does cytosine and guanine have
3 hydrogen bonds
Describe an RNA polymer
A relatively short, singular polynucleotide strand
Name the types of RNA
messenger RNA, transfer RNA and ribosomal RNA
Define a ribosome
A small organelle which are the site of protein synthesis and translation
Where are ribosomes found
Either free in the cytoplasm or attached to the rough endoplasmic reticulum
Describe the difference between prokaryotic and eukaryotic ribosomes
Eukaryotic ribosomes are 80s (60&40 subunits), prokaryotic ribosomes are 70s (30&50 subunits)
Describe the structure of a ribosome
A small and large subunit, where the large unit is the sight of translation
Who discovered DNA
Friedrich Miescher in 1800s
Who discovered the double helix structure of DNA
Watson and Crick in 1953
Describe why DNA nucleotides are added in the 5’ to 3’ direction
DNA polymerase is specific and the 5’ and 3’ ends of nucleotides are different shapes and therefore can only be complementary with the 3’ end of a developing strand
Describe how the structure of RNA differs from DNA
RNA is single stranded, contains ribose sugar, uracil instead of thymine
Suggest how changing the sequence of DNA nucleotides can affect the final product the DNA codes for
Different sequence of amino acids produces a different tertiary structure so the protein can no longer function
Describe why nucleotides can only be added in a 5’ to 3’ direction
DNA polymerase is specific and the 5’ and 3’ ends of nucleotides are different shapes and therefore can only be complementary with the 3’ end of a developing strand
How can drugs prevent DNA replication
By preventing complementary base pairing
What is the purpose of DNA replication
To copy the DNA so two new daughter cells can be produced with full copies of parental DNA
Describe semi-conservative replication
The process where one of the polynucleotide strands from the original DNA is used as a template
Why is semi-conservative replication important
To ensure genetic continuity, replacement and growth of cells
Describe the role of DNA helicase in semi-conservative replication
Breaking hydrogen bonds between base pairs, to unwind the DNA
Describe the role of DNA polymerase in semi-conservative replication
Catalyses condensation reactions to form a new strand
Describe semi-conservative replication
DNA helicase unwinds DNA, original polynucleotide acts as a template for free nucleotides, new nucleotides are joined by DNA polymerase
Who discovered semi-conservative replication
Meselson and Stahl
How did Meselson and Stahl discover semi-conservative replication
With 14N and 15N nitrogen
Why is semi-conservative replication important
To ensure genetic information is passed from one generation to the rest
How did Nitrogen show DNA replication
Combined densities in a N14 and N15 combination
What is a polynucleotide
Half of a double helix strand
What starts the semi-conservative replication process
Unwinding of the double helix
What bonds does DNA polymerase form
Phosphodiester bonds
What structure are enzymes
Globular
What is enzymes effects on rate of reaction
Speeds the up as they are biological catalysts
How do enzymes act as biological catalysts
By reducing activation energy without being used up or changed
What is the active site on an enzyme specific to
A specific substrate
Define intracellular enzymes
Produced and functioning inside the cell
Define extracellular enzymes
Secreted by cells and catalyse reactions outside the cells
What do enzymes and substrates react with
Induced fit
How does the induced fit theory work
Substrate reacts with amino acids around the active site changing the tertiary structure to allow substrate to fit
Describe catabolic reactions
Breakdown of complex molecules into simpler products
Give examples of catabolic reactions
Cellular respiration and hydrolysis
Define anabolic reactions
Reactions involving building a more complex molecule from simpler ones
Give examples of anabolic reactions
Protein synthesis and photosynthesis
What happens when temperature of enzymes increases
Kinetic energy increases meaning more successful collisions so more enzyme substrate complexes form
Define denaturing
Ionic and hydrogen bonds break which changes the tertiary structure of the active site so is no longer complementary to the substrate
Name all limiting factors affecting enzymes
Temperature, pH and enzyme concentration
What happens when the enzyme goes above optimum temperature
It denatures
What happens to an enzyme either side of optimum pH
It denatures
What happens to enzymes when their concentration increases
Rate of reaction is faster as you increase concentration
Why does rate of reaction increase when enzyme concentration increases
Higher chance of successful concentrations
What happens when the enzyme concentration to rate graph plateau’s
Something other than active sites becomes the limiting factor
What does an increase in SA mean in terms of reactions
Increased rate of reactions
Define a competitive inhibitor
Molecules with a similar structure to substrate and can fit into active sites, preventing formation of enzyme substrate complexes
Increase in substrate concentration does what too competitive inhibitors
Reduces their chance of forming an enzyme substrate complex
Define a non competitive inhibitor
Molecules which bind to the enzyme at an alternative site, altering the shape of the active site
What site does non-competitive inhibitors attach to
Allosteric site
How does a non-competitive inhibitor denature the enzyme
By causing change to tertiary structure
What is the effect of substrate concentrations on non-competitive inhibitors
Nothing, inhibitors always have an effect
How do you calculate rate of reaction
Gradient of a graph
What is an exopeptidase
Hydrolyses peptide bonds between amino acids, near the ends of a polypeptide to remove singular amino acids or dipeptides
What are endopeptidases
Hydrolyse peptide bonds within a polypeptide forming smaller peptides to increase SA
Name the control variables of an enzyme experiment testing temperature
pH, enzyme concnetration
Explain the effects of increasing conc. of substrates on the rate without an inhibitor
More successful collisions between substrate and active site, forming more enzyme substrate complexes, so enzyme concentration is the limiting factor
Explain why different enzymes are required to do different things
Enzymes are specific, and substrates are different shapes
State the control variables for investigating pH of an enzyme
Substrate/enzyme concentration, temperature
Name the monomer for proteins
Amino acids
What elements do amino acids contain
Nitrogen, carbon, hydrogen, oxygen
What groups does an amino acid contain
Amine (NH2), carboxyl (COOH) and residual (R)
How many residual groups are there in nature
20
What can proteins form in cells
Enzymes, cell membrane proteins, transport proteins, hormones
What does the sequence, type and number of amino acids determine
Shape and function of proteins
How many amino acids are there in nature
20
Name the properties that change with the residual group
Molecule size, hydrophobic, hydrophilic and charge
Describe formation of a peptide bond
Removal of an OH from the carboxylic group and a hydrogen removed from the amine group of the other amino acid
What reaction forms a peptide bond
Condensation reaction
Define a dipeptide
The condensation of two amino acids
Define a polypeptide
The condensation of 3 or more amino acids
What are the two main structures of a protein
Globular and fibrous
Name a protein with a globular structure
Enzymes
Name a protein with a fibrous structures
Keratin
Describe globular proteins
Compact, roughly spherical and soluble proteins
