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A student stated:
- The rates of respiration with glucose maltose and sucrose were very similar.
- The yeast could not hydrolyse diasaccharides.
Evaluate the students statements.
The sensory neurone was stimulated electrically and the FURA-2 fluoresence in the synaptic bulb was measured. At the same time an electrode recorded the membrane potential in a postsynaptic neurone. The results of this study are shown below:
Strengths of electrical
stimulation Low Medium High
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FURA-2 fluoresence in
synaptic bulb Low Medium High
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Highest membrane potential
in postsynaptic neurone (mV) -60 +40 +40
The intesity of FURA-2 fluorescence is proportional to the concentration of Ca2+ ions.
The scientists concluded that changes in the concentration of Ca2+ ions in the presynaptic neurone caused an action potential in the post synaptic neurone.
Evaluate and explain the scientists' conclusion.
Algae are single-celled photosynthetic organisms. An investigation was carried out into the effect of CO2 concentration on the concentrations of ribulose diphosphate (RuBP) and glycerine 3-phosphate (GP) present in algae. Algae were grown in a solution containing a high concentration of CO2. The concentration of CO2 was then reduced. RuBP and GP concentration were measured for 2 minutes before and 3 minutes after the reduction in CO2 concentration.
Describe and explain the effect of reducing the CO2 concentration of RuBP and GP in the algae.
The student used a colorimeter to measure the concentration of each substance in the liquid surrounding the cells.
The colorimeter had an analogue display. The reading was indicated by a needle moving across the scale. The smallest divisions on the scale corresponded to 0.1 absorbance unit.
After the investigation the students suggested some improvements.
Match each of the improvements to the corresponding justification:
Improvements:
1) Use a colorimeter with a digital display showing absorbance units to three decimal places
2) Cheque the zero value of the colorimeter with purified water before use
3) For each concentration repeat the measurement of the rate of reaction three times and calculated mean ask 4) Students in several schools to carry out the same investigation
Justification:
A) To assess repeatability
B) To assess reproducibility
C) To reduce systematic error
D) To reduce random error (uncertainty)
E) To increase resolution
What type of graph (rate of uptake against concentration) would a substance entering a cell by diffusion produce?
What alternatively what type of graph would a substance entering a cell by active transport produce?
Which of the following statements A to D describes and explains the relative yield of ATP in anaerobic and aerobic respiration?
A) Anaerobic respiration produces less ATP per molecule of glucose because lactate is converted to pyruvate
B) Anaerobic respiration produces less ATP per molecule of glucose because NAD is not regenerated in oxidative phosphorylation
C) Anaerobic respiration produces more ATP per molecule of glucose because NAD is regenerated in oxidative phosphorylation
D) Anaerobic respiration produces more ATP per molecule of glucose because pyruvate is converted to lactate
Which of the following statements from A to D about water transport in plants is/are correct?
1- Transpiration happens as a consequence of the need for gas exchange.
2- There are cohesive forces between water molecules because they from hydrogen bonds with one another.
3- Water is drawn up from the stem due to adhesive forces between water molecules.
A) 1, 2 and 3
B) only 1 and 2
C) only 2 and 3
D) only 1
Which of the following statements A to D describes the movement of water across plant roots?
A) The Casparian strip blocks movement by the symplast pathway.
B) The symplast pathway requires water to cross partially permeable membranes.
C) Water moves from the soil to the root hair cells up a water potential gradient.
D) Water moves through the leaves only by the symplast pathway and across the roots only by the apoplast pathway.
Which of the following statements A to D does not correctly describe the structure or formation of plant vascular tissues?
A) Companion cells are linked to xylem vessels by plasmodesmata.
B) Mature sieve tube elements do not contain nuclei.
C) Phloem and xylem are formed by differentiation of vascular meristems.
D) Xylem vessels have non-lignified pits to allow movement in and out.
Which of the following statements A to D about microscopes is correct?
A) A light microscope with an eyepiece lens magnification of x10 and an objective lens magnification of x50 will have an overall magnification of x60.
B) Scanning electron microscopes and laser scanning confocal microscopes can both produce three dimensional images.
C) The maximum resolution of a scanning electron microscope is lower than that of a light microscope.
D) Transmission electron microscopes and laser scanning confocal microscopes can both produce three dimensional images
