Paper 3 Flashcards
Describe how the stimulation of a Pacinian corpuscle produces a generator potential.
[3 marks]
- Stretch mediated sodium ion channels in the membrane
- Increased pressure deforms sodium ion channels in the membrane
- Sodium ions channels open
- Sodium ions diffuse in
- Depolarisation occurs
What is meant by the all-or-nothing principle?
[2 marks]
- An action potential is only generated if threshold is exceeded
- High pressure can generate an action potential
What is the time period called where no new generator potential can be produced?
[1 mark]
- Refractory period
A student investigated the effect of different sugars on the ratio of respiration in yeast.
Yeast normally respires glucose.
For her first experiment:
• She completely filled a small test tube with yeast in glucose solution. She pushed the small test tube up inside a larger test tube.
• She inverted the larger test tube and placed it in a water bath at 30°C for 25 minutes.
• After 25 minutes she measured the length of the bubble of carbon dioxide produced in the small test tube.
Other than those stated, suggest TWO variables the student needed to keep constant in her investigation.
[1 mark]
- Concentration/mass of yeast
- Concentration/mass of glucose
- Concentration of oxygen
- Volume of yeast
- Volume of glucose
- pH
The student repeated the experiment using yeast in maltose solution. She found the rate of carbon dioxide production was slower than with yeast in glucose solution.
Suggest why.
[2 marks]
- Maltose is a disaccharide
- Takes time to be hydrolysed into glucose
Fill in the blanks
Cell surface membrane
Protein
Plasma B cell
Antigen
Active
Herd
Suggest why a vaccine wouldn’t be effective against HIV
HIV replicates inside T cells
Why do the following antibiotics not work against HIV?
Effects double stranded DNA
Effects murein
Genetic material in HIV is single stranded
No murein cell wall
Describe the relationship between the SA:V ratio of an organism and metabolic rate
Smaller mammals have a greater SA:V ratio
Smaller mammals lose more heat
Smaller mammals have a greater rate of respiration
Name two features of a fish gas exchange system that increase the SA
Lamellae
Gill filaments
Explain how you would reset the position of the coloured liquid to the right hand side
Open tap
Push syringe
Close tap
Explain why there is a high frequency of LS in the Faroe Islands
Inbreeding so small gene pool
Define the term population
A group of organisms of the same species occupying the same space at the same time that can interbreed
How does the graph show that succession has occurred?
Climax community reached in 1969
Habitat became less hostile as pioneer species altered the biotic/abiotic factors
What part of succession is the flat part and why are results not constant?
Climax community
Death of animals
