Energy Cycles

In order for living organisms to survive, what do they have to be, and why?

They have to be active. Organisms grow, respond to changes in their environment and deal with threats from other organisms. They have to find or make food, and reproduce.

What does the activity of living organisms depend on?

Metabolic reactions or processes.

What are examples of metabolic activities in living organisms?

• Active transport, which is essential for the uptake of nitrates by root hair cells, loading sucrose into sieve tube cells, the selective reabsorption of glucose and amino acids in the kidney, and the conduction of nerve impulses.

• Anabolic reactions, such as the building of polymers like proteins, polysaccharides, and nucleic acids essential for growth and repair.

• Movement brought about by cilia, flagella, or the contractile filaments in muscle cells.

All of these metabolic activities require energy.

Since the universe began, what is the change in the total amount of energy?

The total amount of energy in the universe hasn’t changed from the time of the Big Bang, until now.

Why is the universe gradually cooling as it expands?

Because this energy is being dispersed over a large area. This is inevitable and irreversible.

What is the law of conservation of energy?

Energy cannot be created or destroyed, only transferred.

What is radiation from the sun used to do?

To fuel the metabolic reactions and processes necessary to keep organisms alive before, eventually being transferred back to the atmosphere as heat.

What do organisms make use of?

The energy in the bonds of organic molecules, such as glucose. These bonds are formed during photosynthesis in plants and other photosynthetic organs. Light is trapped by chlorophyll molecules. This energy is used to drive the synthesis of glucose from carbon dioxide and water.

What do all organisms need to do?

Respire.

What is respiration?

The process by which organic molecules, such as glucose, are broken down into smaller inorganic molecules, like carbon dioxide and water.

What are two of the most important chemical reactions in the living world?

• Photosynthesis.

• Respiration.

What is photosynthesis the reaction behind the production of?

Most of the biomass to provide the ATP needed to drive the metabolic reactions that take place in cells.

What is the relationship between photosynthesis and respiration?

They are intimately linked. The raw materials for one are the products of another so they are interrelated throughout the living world.

What is the symbol equation for photosynthesis?

6CO2 6H2O → C6H12O6 6O2.

What is the symbol equation for respiration?

C6H12O6 6O2 → 6CO2 6H2O.

What is a general rule in biochemistry?

That energy is used to break bonds, and energy is released when bonds are formed. The same quantity of energy is involved whether a particular bond is being broken or formed - the bond energy.

What does whether a reaction is exothermic or endothermic depend on?

The total number and strength of bonds that are broken or formed during the reaction.

What are the atoms in small inorganic molecules like water and carbon dioxide joined by?

Strong bonds that release a lot of energy when they form but require a lot of energy to break.

What do organic molecules like glucose and amino acids contain more bonds than?

Small inorganic molecules. These are weaker bonds compared with those in inorganic molecules and, therefore, release less energy when they form and require less energy to be broken.

In respiration, what is broken down?

Large organic molecules, forming small inorganic molecules.

In respiration, what is the total energy required to break all the bonds in a complex organic molecule less than?

The total energy released in the formation of all the bonds in the smaller inorganic products.

In respiration, what is the excess energy released by the formation of the bonds used to synthesise?

ATP

What do organic molecules contain?

Large numbers of carbon-hydrogen bonds, particularly lipids.

What does the sharing of electrons by carbon and hydrogen result in?

A non-polar bond which does not require a lot of energy to break. The carbon and hydrogen released then form strong bonds with oxygen atoms, forming carbon dioxide and water, resulting in the release of large quantities of energy.

What happens in photosynthesis when organic molecules are made from small inorganic molecules?

The energy required to build these molecules comes from the sun.