Proteins + Nucleic Acids Flashcards
How can an enzyme be phosphoralated? (2)
- Attachment of phosphate
- Hydrolysis of ATP
Explain how selection occurs in living organisms? (5)
- Variation due to mutations
- Due to different environmental conditions/selection pressures
- Selection for advantageous allele to survive + reproduce
- Which leads to change in alleles frequency
- Occurs over a long period of time
What is directional selection? (4)
- Selection for only one extreme
- Organisms with advantageous alleles will have increased reproductive success
- Alleles are passed onto future generations
- Overtime, frequency increases
What is stabilising selection? (3)
- Selection against both extremes
- Only mean phenotype will have reproductive success so alleles are passed onto future generations
- Over time, frequency of mean alleles increases
Definition of:
- Phenotype
- Genotype
- Characteristics
- Genetic constitution of an organism/ All the alleles in an organism
Describe 2 aseptic techniques used when transferring a sample of broth culture onto an agar plate? Explain?
1) Open petri dish as little as possible - to prevent unwanted bacteria contaminating the dish
2) Wear gloves/mask - to prevent contamination from bacteria on hands/mouth
3) Flame the loop/neck of culture - to maintain a pure culture of bacteria
Define ‘gene mutation’
Explain how a gene mutation can have:
- No effect on an individual
- A positive effect on an individual
Change in the bases resulting in the formation of new alleles
No effect:
- Genetic code is degenerate
- Change in amino acid but no effect on tertiary structure
Positive effect:
- Results in change in polypeptide that positively changes the properties
- May result in increased reproductive/survival success
Define the term exon
Base sequence coding for polypeptide
What are mutagenic agents? Includes? (3)
Increase the rate of spontaneous mutations
- High energy ionising radiation
- DNA reactive chemicals
- Biological agents
Consequences of a mutation? (2)
- May alter secondary structure - change in hydrogen bonds affecting alpha helices + beta-pleated sheets
- May alter tertiary structure - change position of H, ionic, disulphide bonds which changes active site of enzyme + make the protein non-functional
Types of mutations in DNA? What is it? (3)
- Substitution - silent mutation, sometimes degenerate
- Addition - frameshift
- Deletion - frameshift
Meaning of:
- Universal
- Degenerate
- Non-overlapping
- Same 3 bases on mRNA/DNA code for the same amino acid in all organisms
- More then 1 codon/triplet codes for the same amino acid
- Each base is only part of 1codon/triplet
Describe translation? (6)
- mRNA binds to ribosome
- TRNA’s anticodon binds to start codon of mRNA
- TRNA carries a specific amino acid
- TRNA is released as ribosome moves across mRNA strand
- Peptide bond forms between amino acids using energy from ATP
- Ribosome releases polypeptide when stop codon is reached
Describe transcription? (5)
- DNA helicase breaks hydrogen bonds
- Only 1 strand is used as a template
- RNA nucleotides are attracted to complimentary exposed bases (A+U, G+C)
- RNA polymerase joins adjacent nucleotides forming phosphodiester bonds through condensation reaction
- Pre-mRNA spliced to remove introns
Definition of:
- Allele
- Gene
- Histone
- Different version of a gene
- DNA base sequence that codes for a polypeptide
- A protein that linear DNA coils around
Definition of:
- Genome
- Proteome
- Loci
- All the DNA/alleles/genes in a cell
- Full range of proteins that a cell produces
- Position of a gene within a chromosome
Properties of tRNA? (5)
Role?
- Cloverleaf structure
- Shorter then DNA + mRNA
- Single stranded
- Has hydrogen bonds
- 3 bases are called anticodons
To carry a specific amino acid to the ribosome during translation
Differences between eukaryotic + prokaryotic DNA? (3)
- E is linear whereas P is circular
- E are associated with histones
- E contains introns
Who proposed models of structure of DNA + DNA replication?
Watson + Crick
Give 2 properties of water that are impotant in the cytoplasm of cells? Explain?
Polar molecule - acts as a solvent
Reactive - takes place in hydrolysis
Function of:
- Phosphate
- Nitrates/Nitrites
- Chloride
- Components of DNA, RNA, ATP
- Taken up from the soil by plant roots
- Used in regulating water potential of small intestine
Function of:
- H+
- Iron
- Sodium
- Affects pH
- Allows transport of oxygen to repair tissues
- Used in co-transport of glucose + amino acids
Explain the properties that makes water important for organisms? (5)
1) A metabolite in respiration
2) A solvent so metabolic reactions can occur
3) High specific heat capacity so buffers change in temperature
4) High latent heat of vaporisation so provides cooling effect
5) Cohesion so supports columns of water in plan
Descibe how ATP is resynthesised in cells?
Is made by ADP + Pi by ATP synthase during respiration
How is ATP a suitable energy source for cells? (4)
- Releases small amounts of energy
- Releases energy instantaneously
- Can be rapidly re-synthesised
- Does not leave cell
What does ATP contain?
What is ATP used for? (2)
Adenine, ribose sugar, 3 phosphate groups
Used as an energy source in cells, to phosphoralate molecules to make them more reactive
What is the Meselson-Stahl experiment?
1) Two samples of bacteria were grown (14N + 15N)
2) A sample of DNA was taken from each + spun in a centrifuge
3) DNA from the heavy nitrogen settled lower than the light nitrogen
4) Both bacteria samples was put in light nitrogen + replicated + centrifuged
5) Will be even lighter - 15N/14N, 14N/14N, 15N/14N, 14N/14N
How does semi-conservative replication work? (4)
- DNA helicase breaks hydrogen bonds between bases causing them to unwind
- Each strand acts as a template
- New DNA nucleotides are attracted to exposed complimentary bases on template strand
- DNA polymerase joins adjacent nucleotides togther forming a phosphodiester bond
How is DNA’s structure related to it’s function? (5)
- Sugar-phosphate backbone + double helix - provides strength + stability
- Long molecule - stores lots of information
- Weak hydrogen bonds - allows easy separation for semi-conservative replication
- Helical structure - compact
- Double stranded - replication can occur because each strand acts as a template
Why is 5’ and 3’ important? (2)
- Important when making proteins as it ensures only 1 strand is read to make protein
- Important in DNA replication as DNA polymerase only has a complimentary active sote to the 5’ end
Differences between DNA and mRNA? (4)
- DNA is longer
- Has hydrogen bonds
- Deoxyribose sugar
- Has Thymine as a base
Suggest how the increase in temperature of the water caused the release of the red pigment? (2)
- Causes proteins to denature
- Which damages surface membrane
