IB Biology SL C1.3 Photosynthesis Questions

Practise IB Biology SL C1.3 by explaining light energy conversion, pigment evidence, wavelength spectra and limiting-factor experiments.

Exam points

Analyse pigment and chloroplast evidence to explain how light energy is captured and converted in photosynthesis.
Trace carbon dioxide reduction using water-derived hydrogen and light-derived energy to form glucose and storage carbohydrates.
Explain that water is split by light-driven photolysis and is the source of oxygen released during photosynthesis.
Separate photosynthetic pigments by chromatography, describe the procedure and calculate or interpret Rf values to identify pigments.
Interpret chlorophyll and accessory-pigment absorption spectra across wavelengths, including reflected light.
Compare absorption and action spectra to explain how pigment wavelength absorption relates to photosynthetic rate.
Interpret limiting-factor graphs, calculate photosynthesis rates and evaluate controlled experiments using plotted evidence.
Interpret carbon-dioxide and temperature data to separate effects on uptake and judge predicted plant-growth changes.

Covered syllabus points

C1.3.1—Light energy → chemical energy C1.3.2—CO₂ → glucose C1.3.3—Oxygen as by-product C1.3.4—Photosynthetic pigment separation C1.3.5—Absorption of specific wavelengths C1.3.6—Absorption vs. action spectra C1.3.7—Limiting factors investigation C1.3.8—CO₂ enrichment experiments

[Maximum number: 5]

Describe how leaf cells make use of light energy.

[Maximum number: 4]

Outline the production of carbohydrates in photosynthesis.

Light is absorbed by chlorophyll;
OR chlorophyll absorbs more red and blue light.
Absorbed light energy is converted to chemical energy.
Some of the energy is used for production of ATP.
Water molecules are split/photolysis.
Produces oxygen as waste product / hydrogen / NADPH.
Plants absorb/fix $\mathrm{CO}_{2}$ from air or water.
ATP/energy is needed to produce carbohydrates/starch.

[Maximum number: 1]

A photosynthesis experiment was carried out using an aquatic plant. The image shows the contents of the test tube after being exposed to light and room temperature for 30 minutes.

What explains the presence of bubbles?

Oxygen is formed when carbon dioxide combines with chlorophyll.

Carbon dioxide is formed during the light-dependent reaction.

Oxygen is released when light splits water molecules in chloroplasts.

Carbon dioxide is released from dissociation of sodium hydrogen carbonate.

[Maximum number: 1]

What does the $R_{f}$ value in thin layer chromatography represent?

The distance travelled by the pigment front in a fixed time period

The distance from the origin to the solvent front at the end of the experiment

The ratio of distances travelled by the pigment and solvent fronts

The concentration of the pigment applied to the chromatography plate

[Maximum number: 1]

Which type of light is least useful for photosynthesis in terrestrial plants?

Blue

Green

White

Red

[Maximum number: 2]

Explain the relationship between the action spectrum and the absorption spectrum in photosynthetic plants.

[Maximum number: 1]

Global atmospheric carbon dioxide levels are rising. A study was carried out to test if the temperature dependence of photosynthesis was altered by elevated atmospheric $\mathrm{CO}_{2}$ . Maize plants were grown in natural sunlight in controlled environmental chambers at different temperatures using current atmospheric and doubled $\mathrm{CO}_{2}$ levels.

The graph below shows daily patterns of $\mathrm{CO}_{2}$ exchange at three different temperatures. Open shapes ( $\mathrm{o}, \Delta, \mathrm{v}$ ) represent current atmospheric $\mathrm{CO}_{2}$ levels and closed shapes ( $\bullet, \mathbf{\Delta}, \mathbf{m}$ ) represent elevated $\mathrm{CO}_{2}$ levels.

State the temperature that resulted in the highest rate of photosynthesis under current atmospheric conditions.

$31^{\circ} \mathrm{C}$

[Maximum number: 2]

Using the data in the graph, discuss whether rising carbon dioxide levels in the atmosphere will increase growth rates in maize.

data does not support idea that rising $\mathrm{CO}_{2}$ levels will increase growth rates in maize
(at all temperatures) there appears to be no difference between exchange rate at current or elevated $\mathrm{CO}_{2}$ levels
temperature has larger effect on growth of maize
so if rising $\mathrm{CO}_{2}$ levels causes more of a greenhouse effect/larger temperature increase, this will affect growth of maize

All question bank results loaded

a	leaf cells contain chloroplasts;
b	light is absorbed by chlorophyll (in chloroplasts);
c	other pigments absorb different wavelengths;
d	light energy is used in photosynthesis;
e	(light is needed) to combine water and carbon dioxide/fix carbon dioxide;
f	carbon compounds/organic compounds/glucose/starch/carbohydrate are produced;
g	blue and red light is absorbed;
h	perform photolysis OR split water molecules;

Covered syllabus points

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8