Steps of Questions, Unit 1 Flashcards
What are the stages of cancer developing ?
1) Most cancers originate from a cells undergoing successive mutations to the genes involved in cell division.
2) Cancer cells divide excessively and uncontrollably, because they do not respond to regulatory signals.
3) This results in a mass of abnormal cells called a tumour.
4) If cancer cells within the tumour fail o attach to each other, they spread through the body where they form secondary tumours.
Describe the stages of DNA replication of the leading strand.
1) The DNA double helix unwinds.
2) Hydrogen bonds between complimentary base pairs unzip, allowing the two strands to seperate. This forms a replication fork with two template strands.
3) A primer attaches to the 3’ end of each DNA template strand to start replication.
4) DNA polymerase adds complementary DNA nucleotides to the 3’ end of the new growing strand. The leading strand is replicated continuously.
Describe the stages of DNA replication in the lagging strand
1) The DNA helix unwinds.
2) Hydrogen bonds between complimentary base pairs unzip, allowing the two strands to seperate. This forms a replication fork with two template strands.
3) A primer attaches to the 3’ end of each DNA template strand to start replication.
4) DNA polymerase adds complementary DNA nucletoides to the 3’ end of the new growing strand. Lagging strand (5’-3’) is replicated in fragments.
5) Fragments of the lagging strands are joined together using the enzyme ligase.
What are the stages of PCR
1) DNA is heated to between 92-98°C to break the hydrogen bonds between complimentary bases, allowing the two strands to seperate.
2) DNA is cooled to between 50-65 °C which allows primers to bind to specific target sequences on the 3’ end of the template strands.
3) DNA is heated to between 70-80°C, allowd heat-tolerant DNA polymerase to replicate the target region of DNA. optimal conditions: 72°C
What are the stages of transcription
1) RNA polymerase moves along the DNA, unwinding the double helix and unzipping the hydrogen bonds between bases.
2) RNA polymerase adds complementary RNA nucleotides to the template strand of DNA to synthesize a primary mRNA transcript.
3) The primary mRNA transcript moves away from the DNA.
What are the stages of translation ?
1) A ribosome binds to the 5’ ends of the mature mRNA template at the mature mRNA’s start codon (5’ end)
2) Each molecule of tRNA carries a specific amino acid from the cytoplasm to the ribosome.
3) Codons on mRNA and anticodons on tRNA bind together using complementary base pairing.
4) The ribosome moves along the mRNA transcript, translating the genetic code into a sequence of amino acids - the order of codons on the mRNA determines the sequence of amino acids.
5) A peptide bond forms between the adjacent amino acids, to forma polypeptide chain.
6) tRNA molecule is removed from the ribosome as the polypeptide forms.
7) This process continues until a stop codon is reached
Give an account of enzyme activity under the heading of induced fit
- The substrate binds to the active site of the enzyme.
- The shape of tyhe active site is complimentary to the shape of the substrate.
- The active site changes shape to better fit the substrate after it binds.
-The induced fit of the active site lowers the activation energy, increasing the chance of the reaction being successful.
-Substrates have a high affinity for the active site so are attracted to the ezymes. Products have a low affinity for the active site so are released from the enzyme.
What controls metabolic pathways
-Metabolic pathways are controlled by the prescence or abscene of particular enzymes and the regulation of the rate of reaction of key enzymes
-Control of these pathways is brough about by controlling enzymes action by feedback inhibition.
-Feedback inhibition occurs when the end-product in the metabolic pathway reaches a critical concentration.
-The end-product then inhibits an earlier ezyme, blocking the pathway (usually the first enzyme in pathway)
-This prevents further synthesis of the end-product and also prevents wasteful conversions.
Describe glycolysis
-Glucose is broken down into two molecules of pyruvate
Energy investment phase - Two molecules of ATP are required for the phosphorylation of glucose and intermediates.
Energy Pay off phase - 4x molecules of ATP are produced and results in a net gain of 2x ATP, Dehydrogenase enzymes Remove hydrogen ions and electrons from intermediates and pass them to coenzyme NAD to form NADH
What happens in the citric acid cycle
1) The acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate.
2) During a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate, this results in the generation of ATP and the release of carbon dioxide.
Dehydrogenase enzymes Remove hydrogen ions and electrons from intermediates and pass them to coenzyme
NAD to form NADH which is then passed on to the electron transport chain (NAD is a coenzyme)
Outline what happens during the electron transport chain
1) NAD releases high energy electrons along the electron transport chain.
2) This energy allows hydrogen ions from NADH to be pumped across the inner mitochondrial membrane.
3) Hydrogen ions flow back through the membrane proteins ATP synthase which generates a high quantity of ATP.
4) Hydrogen ions and electrons combine with oxygen to form water.
Why is lactate produced ?
-During intense exercise muscle cells do not receive enough oxygen to support the electron transport chain.
-Under these anaerobic conditions pyruvate is converted to lactate which causes muscle fatigue.
-This regenerates the NAD required to maintain ATP production during glycolysis.
How is lactate produced?
-Lactate metabolism involves the transfer of hydrogen ions from NADH, produced during glycolysis, to pyruvate to produce lactate.
-This regenerates the NAD required to maintain ATP production during glycolysis.
When is oxygen debt repaid
Oxygen debt is the temporary lack of oxygen availability in muscle cells after/during intense exercise, body cannot provide enough oxygen to breakdown lactate.
-Oxygen debt is repaid when exercise is complete, this allows lactate to be converted back to pyruvate and glucose in the liver.
Describe what happens to pyruvate under aerobic conditions (fate of pyruvate)
Pyruvate is broken down to an Acetyl group that combines with coenzyme A to form Acetyl coenzyme A
