2025 aqa a level paper 1
-. Word equation for mitotic index
- How did the distance from the root tip affect mitotic
index - correct answerMitotic index = number of cells undergoing mitosis or with visible chromosomes
/total number of cells
Increased distance caused a decrease in mitotic index, less cells undergoing mitosis
Or vice versa
Increased distance caused an increase in the number of cells in interphase or cytokinesis
Unable to comment on number in cytokinesis and interphase respectively
Describe appearance and behaviour of chromosomes during prophase and anaphase - correct
answerProphase
- Chromosomes shortern, thicken and CONDENSES so becomes visible
- Chromosomes appear as two sister chromatids joined at a centromere
Anaphase
- Centromere divides
- Sister chromatids are pulled to opposite poles
- V shaped
Describe the structure of ATP. Outline how named enzymes break and synthesise ATP - correct
answerAdenosine triposphate consisting of (adenosine which consists of) adenine and ribose and three
(inorganic) phosphate groups
ATP is a nucleotide derivative
ATP Hydrolase/ATPase - Hydrolyses ATP to ADP and a Inorganic Phosphate (Pi)
ATP Synthase - synthesises ADP and Pi to form ATP in a condensation reaction.
And their processes an equations
Condensation
Hydrolysis
, ATP synthesis: Respiration and Photosynthesis
Should we mention the processes atp is used for? No right? I
Enzymes so complimentary etc.
Explain how you
breathe in - correct answerDiaphragm and External intercostal muscles con
tract, pulling the ribcage up and out
This increases the volume of the thoracic cavity, decreasing the pressure inside the alveoli, so air from
the atmosphere
moves into the lungs down the pressure gradient
Explain how you could use cell fractionation and ultracentrifugation to extract a sample of nuclei from
muscle tissue - correct answerHomogenisation - homogenise the muscle tissue to break up the
organelles and filter to remove debris
Place in cold, buffered, isotonic solution
Cold - to reduce enzyme activity
Isotonic to prevent enzymes bursting
Buffered to maintain a constant pH and prevent enzymes denaturing
Filter to remove large cell debris
Ultracentrifugation -
Spin in a centrifuge at a lower/high speed
Produces supernatant and dense pellet at the bottom
Pellet contains nuclei
Pellet at the bottom due to most dense
Nuclei at the bottom as they are heavy
Explain the role of organelles in production and release of enzymes in an animal cell(NOT transcription) -
correct answerGolgi Apparatus - modifies proteins, packages proteins into golgi vesicles for transport to
cell membrane and release of enzyme
Ribosomes - site of translation, forms 1 structure of enzyme (polypeptide chain of amino acids)
-. Word equation for mitotic index
- How did the distance from the root tip affect mitotic
index - correct answerMitotic index = number of cells undergoing mitosis or with visible chromosomes
/total number of cells
Increased distance caused a decrease in mitotic index, less cells undergoing mitosis
Or vice versa
Increased distance caused an increase in the number of cells in interphase or cytokinesis
Unable to comment on number in cytokinesis and interphase respectively
Describe appearance and behaviour of chromosomes during prophase and anaphase - correct
answerProphase
- Chromosomes shortern, thicken and CONDENSES so becomes visible
- Chromosomes appear as two sister chromatids joined at a centromere
Anaphase
- Centromere divides
- Sister chromatids are pulled to opposite poles
- V shaped
Describe the structure of ATP. Outline how named enzymes break and synthesise ATP - correct
answerAdenosine triposphate consisting of (adenosine which consists of) adenine and ribose and three
(inorganic) phosphate groups
ATP is a nucleotide derivative
ATP Hydrolase/ATPase - Hydrolyses ATP to ADP and a Inorganic Phosphate (Pi)
ATP Synthase - synthesises ADP and Pi to form ATP in a condensation reaction.
And their processes an equations
Condensation
Hydrolysis
, ATP synthesis: Respiration and Photosynthesis
Should we mention the processes atp is used for? No right? I
Enzymes so complimentary etc.
Explain how you
breathe in - correct answerDiaphragm and External intercostal muscles con
tract, pulling the ribcage up and out
This increases the volume of the thoracic cavity, decreasing the pressure inside the alveoli, so air from
the atmosphere
moves into the lungs down the pressure gradient
Explain how you could use cell fractionation and ultracentrifugation to extract a sample of nuclei from
muscle tissue - correct answerHomogenisation - homogenise the muscle tissue to break up the
organelles and filter to remove debris
Place in cold, buffered, isotonic solution
Cold - to reduce enzyme activity
Isotonic to prevent enzymes bursting
Buffered to maintain a constant pH and prevent enzymes denaturing
Filter to remove large cell debris
Ultracentrifugation -
Spin in a centrifuge at a lower/high speed
Produces supernatant and dense pellet at the bottom
Pellet contains nuclei
Pellet at the bottom due to most dense
Nuclei at the bottom as they are heavy
Explain the role of organelles in production and release of enzymes in an animal cell(NOT transcription) -
correct answerGolgi Apparatus - modifies proteins, packages proteins into golgi vesicles for transport to
cell membrane and release of enzyme
Ribosomes - site of translation, forms 1 structure of enzyme (polypeptide chain of amino acids)
