Question: Whether it was volcanic activity that spewed sulfur dioxide and ash into the atmosphere, or a giant meteor that crashed into the Earth blasting dust and debris into the sky, both theories of what caused the dinosaurs to become extinct share one critical similarity — light from the sun was obliterated. The result of the months’ long darkness was the mass extinction of nearly 70% of all creatures on Earth.

Like the dinosaurs, humans cannot live without the sun. Not only does it provide light and warmth, it is also the energy source for arguably the most important chemical reaction on Earth: photosynthesis.

Answer the following assignment questions:

1. Explain how photosynthesis and respiration are linked in order to provide you with energy from the food you eat.

Include in your essay:

Complete descriptions of photosynthesis and aerobic respiration.
Describe how these two processes are linked between plants and animals based on the reactants and products (water, carbon dioxide, glucose and oxygen) of both pathways.
Include a description of how energy is transferred from sunlight to ATP, from ATP to sugars, and from sugars to your cells.

2. In the absence of oxygen some cells and organisms can use glycolysis coupled to fermentation to produce energy from the sugar created by photosynthesis.

Explain the role of fermentation in allowing an organism to generate energy for its cell(s) in the absence of oxygen.
Include any reactions required for this process, and explain how the energy from the sun ends up as chemical energy for the anaerobic organism or cell.

3. Cells use enzymes as biological catalysts to increase or accelerate the rate of reactions, such as those in photosynthesis or glycolysis. This allows reactions to occur under conditions that sustain life.

Explain how an enzyme catalyzes a reaction. Include in your essay the three main steps of the cycle of enzyme-substrate interactions.
How is enzyme activity regulated by the cell?