The document discusses how both volcanic activity and meteor impacts could have caused the extinction of dinosaurs by blocking out sunlight for months. This would have disrupted photosynthesis, the key process by which plants and other organisms generate energy from sunlight. Photosynthesis requires sunlight and produces oxygen, while cellular respiration in animals and plants uses oxygen and glucose to produce energy. These two processes are linked, as the glucose from photosynthesis provides an energy source for cellular respiration. The document poses assignment questions about how photosynthesis and respiration are linked to provide energy to organisms, how fermentation allows energy production without oxygen, and how enzymes catalyze reactions like photosynthesis and glycolysis.

1. Background
:
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

2. 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?
Your essays should be several paragraphs in length for each
question, be thoroughly paraphrased, and include appropriate
in-text citations and a reference list in APA format.