I am writing an essay on the subject of, 'The metabolism of green plant cells in relation to energy exchange process.'

Can anyone advise of key ideas to include please?

This is a very, very complicated subject. Look here:
http://en.wikipedia.org/wiki/Metabolism
Notice the chart on the right? That is just a part of the pathway.

Start with that article, it will lead you to others.

When writing an essay on the metabolism of green plant cells in relation to energy exchange processes, there are several key ideas that you can include. These ideas will help you provide a comprehensive understanding of the topic. Here are some key points to consider:

1. Introduction to metabolism and energy exchange: Begin by explaining what metabolism is and why it is essential for green plant cells. Discuss the significance of energy exchange processes, which involve the conversion of light energy into chemical energy through photosynthesis.

2. Overview of photosynthesis: Explain the process of photosynthesis in green plants, including the light-dependent and light-independent reactions. Highlight the role of chlorophyll and other pigments in capturing light energy.

3. Energy storage: Discuss how green plant cells store energy in the form of chemical compounds, such as glucose and starch. Explain the role of ATP (adenosine triphosphate) as an energy currency in cells and its importance in providing energy for various cellular activities.

4. Cellular respiration: Describe the process of cellular respiration, which involves the breakdown of glucose to release energy. Explain how this process complements photosynthesis by utilizing the stored energy to produce ATP.

5. Metabolic pathways: Mention the various metabolic pathways that occur in green plant cells, such as glycolysis, the citric acid cycle, and the electron transport chain. These pathways contribute to the synthesis and breakdown of different molecules, ultimately influencing energy exchange processes.

6. Regulation of metabolism: Highlight the importance of metabolic regulation to maintain a balance between energy production and consumption. Discuss factors that influence the metabolic rate, such as temperature, light intensity, and the availability of nutrients.

7. Interconnection with other cellular processes: Explain how metabolism is interconnected with other cellular processes, such as growth, reproduction, and response to environmental stimuli. Discuss how energy exchange processes in green plant cells impact overall plant physiology.

Remember to support your essay with scientific literature, academic journals, and reputable online resources. While the Wikipedia page you provided is a good starting point for understanding the topic, it is recommended to dig deeper by exploring primary sources and scientific articles for a thorough understanding of the subject matter.