IB Biology SL C1.3 Photosynthesis Question Bank

Chromatography is a technique used to separate the components of a mixture. The photosynthetic pigments from three organisms were separated by thin layer chromatography: spinach (Spinacia oleracea), a red alga (Porphyra) and a brown alga (Fucus).

An experiment on aerobic respiration was performed using a plant in a pot containing fertile soil. The apparatus was set up as shown in the diagram. Sodium hydroxide and limewater (calcium hydroxide) are both alkaline solutions. Limewater goes cloudy when carbon dioxide is bubbled into it.

Ozone gas in the atmosphere helps to block high-energy ultraviolet light (UV) from reaching the Earth's surface. Over the past few decades, the ozone layer has been decreasing, thus allowing through more UV.

The effect of this decrease in the ozone has been studied in different plants. An early study was undertaken on patience dock plants (Rumex patientia) to test the effect of atmospheric ozone levels decreasing by 38 %. The net photosynthesis (total photosynthesis minus total respiration) and respiration of the plants were measured during seven days of exposure to UV. The rates of photosynthesis and respiration are given in rates of carbon dioxide uptake per unit area of leaf.

A variegated Pelargonium plant was grown outdoors in a plant pot. Figure 1 shows one leaf of the Pelargonium. The plant was left in the dark for 24 hours to inhibit photosynthesis. After this time, a sketch was made of the leaf to show the colours (Figure 2), then part of the leaf was covered with black card (Figure 3). Following the exposure of the plant to sunlight for six hours, the black card was removed and the leaf tested for starch (Figure 4).

The graph shows the effect of light intensity on the rate of photosynthesis of a green plant at different $\mathrm{CO}_{2}$ concentrations. The temperature is kept constant at $25^{\circ} \mathrm{C}$.

What is the limiting factor at × ?

An experiment investigated the effect of temperature on the rate of photosynthesis of a plant. Results are shown for temperatures between $5^{\circ} \mathrm{C}$ and $25^{\circ} \mathrm{C}$.

How would further increases in temperature, up to $70^{\circ} \mathrm{C}$, affect the rate of photosynthesis?

The graph shows the rate of photosynthesis as light intensity increases at two different carbon dioxide ( $\mathrm{CO}_{2}$ ) concentrations.

What are the limiting factors of photosynthesis at regions X and Y on the graph?

Bromothymol blue is an indicator that is initially blue and turns yellow when $\mathrm{CO}_{2}$ is present. Tests were carried out varying the presence of a plant (Elodea canadensis) and a snail (Marisa cornuarietis) in an aquatic environment. What condition would produce a blue colour after sampling the water?

Thin-layer chromatography was carried out on red and brown algae to discover what photosynthetic pigments they contained. The results were compared with the known pigments found in spinach leaves.

The cells of a cnidarian, Acropora, contain single-celled, photosynthetic algae belonging to the genus Symbiodinium. The graph shows the effect of light intensity on the rate of photosynthesis by Symbiodinium. A line of best fit is shown on the graph.