Exercises: Photosynthesis and respiration

1. a) Write the word equation for photosynthesis.

1. b) Write the word equation for aerobic respiration.

1. c) State where in a plant cell photosynthesis takes place and where respiration takes place.

State the name of the green pigment that absorbs light for photosynthesis, and name the two raw materials a plant takes in and the two products it makes.

Name three factors that can affect the rate of photosynthesis in a plant.

Pondweed in a beaker of water produces bubbles of oxygen. A student counts the bubbles per minute with a lamp at different distances from the beaker:

1. a) State the relationship between light intensity and rate of photosynthesis shown by the results.

1. b) Calculate the percentage drop in bubbles per minute when the lamp is moved from $10$ cm to $40$ cm.

1. c) Name one other factor that should be kept constant in the experiment.

1. d) Explain why the rate would eventually stop increasing even if the light became very bright.

Yeast cells respire in a sugar solution in a warm kitchen in Sligo, and the bread dough rises.

1. a) Write the word equation for anaerobic respiration in yeast.

1. b) Explain why the dough rises.

1. c) Compare the amount of energy released per glucose molecule in aerobic respiration and in anaerobic respiration.

1. d) Name the product of anaerobic respiration in human muscle cells during intense exercise.

A greenhouse owner in Co. Wexford grows tomatoes. She heats the greenhouse and adds extra carbon dioxide.

1. a) Explain how increasing the carbon dioxide concentration can increase the rate of photosynthesis.

1. b) Explain why raising the temperature too high would reduce the rate of photosynthesis, referring to enzymes.

1. c) Suggest why she also needs to water the plants well.

A sealed container holds a green plant in the light for several hours. The carbon dioxide concentration in the container is measured and found to stay constant.

1. a) Explain what this tells you about the rates of photosynthesis and respiration.

1. b) Predict, with a reason, what would happen to the carbon dioxide concentration if the container were placed in darkness.

1. c) Define the term "compensation point" in this context, and state what happens to the plant's growth if it is kept permanently below it.

A graph of the rate of photosynthesis against temperature rises steadily from $5^\circ\mathrm C$ to a maximum at about $30^\circ\mathrm C$, and then falls sharply to almost zero at $50^\circ\mathrm C$.

1. a) Explain the rise from $5^\circ\mathrm C$ to $30^\circ\mathrm C$.

1. b) Explain the fall above $30^\circ\mathrm C$.

1. c) On the same axes, predict the shape of the curve if the light intensity were halved, and justify your prediction.

Photosynthesis and respiration are described as "opposite processes" that together keep the levels of oxygen and carbon dioxide in the atmosphere steady.

1. a) Compare the two processes in terms of reactants, products and energy change.

1. b) Explain how the destruction of large areas of rainforest could upset this balance.

1. c) Explain why the energy stored by photosynthesis is the original source of energy for almost all food chains, including one in Dublin Bay with phytoplankton, small fish and seals.