30 Energy Transformations in Cells

Key Idea: Photosynthesis uses energy from the sun to produce glucose. Glucose breakdown produces ATP, which is used by all cells to provide the energy for metabolism.

` During photosynthesis light energy is converted into chemical energy in the form of glucose. Glucose is used by plants and animals to provide the energy for cellular respiration. ` During cellular respiration ATP is formed through a series of chemical reactions. The ATP provides the energy to drive life's essential processes. ` Heterotrophs (organisms that cannot make their own food) obtain their glucose by eating plants or other organisms.

Photosynthesis is a chemical process that captures light energy and uses it to convert water and carbon dioxide into glucose and oxygen. Light energy Oxygen Note: Heterotrophs depend on organic molecules (food) to provide the glucose for cellular respiration.

Carbon dioxide + water

Photosynthesis

Glucose *

Pi

ATP

The hydrolysis of ATP provides the energy for metabolic reactions. Each mole of ATP hydrolysed releases 30.7 kJ of energy. Some energy is stored in chemical bonds, while some is lost as heat.

ADP + Pi

Water Other uses of glucose

Fuel

Respiration

A photosynthetic plant cell

Oxygen

Cellular respiration is a chemical process in which the step-wise breakdown of glucose provides the energy to form high energy ATP from ADP and inorganic phosphate (Pi).

Heat energy

1. (a) How does ATP supply energy to power metabolism?

(b) In what way is the ADP/ATP system like a rechargeable battery?

2. What is the immediate source of energy for reforming ATP from ADP?

3. (a) What is the ultimate source of energy for plants?

(b) What process do plants use to store or fix this energy?

4. (a) What is the ultimate source of energy for animals?

(b) What process do animals (and plants) use to extract the energy from this source?

Carbon dioxide