ATP use, synthesis and structure Outline why plants, animals and microorganisms need to respire, with reference to active transport and metabolic reactions; Describe, with the aid of diagrams, the structure of ATP; State that ATP provides the immediate source of energy for biological processes.

Uses for ATP http://www.bbc.co.uk/schools/gcsebitesize/science/videos/aerobic_video1.shtml Adenosine triphosphate is the body’s most common energy source. It is used in every cell in the body for activities such as: Active transport Maintaining body temperature Anabolic reactions (synthesis of smaller molecules into larger ones) Catabolic reactions (degradation reactions)

The Structure of ATP The structure of ATP is similar to that of a nucleotide. What two features are similar? ATP is water soluble and so is easily transported across membranes within a cell. Free electrons surround the phophate groups – these give the molecule its high energetic potential. Nitrogenous base 3 phosphate groups Adenine 5-carbon Ribose sugar

The Structure of ATP Adenosine Adenosine monophosphate (AMP) Adenosine diphosphate (ADP) Adenosine triphosphate (ATP)

ATP as a source of energy The phosphate “tail” of an ATP molecule is where the main source of energy is. Removal of a phosphate group by the process of hydrolysis (the addition of water) releases energy. When ATP is hydrolysed to ADP, 30.5KJ of energy is released. ADP can be further broken down into AMP, which also releases a small amount of energy. Pi + ADP

ATP as a source of energy The energy released as a result of hydrolysis can be channelled into other molecules and used directly by cells. Some energy is lost as heat. ATP is continually being brown down and reformed at a rate of 8000 cycles per day. 30.5KJ released

How is ATP synthesised? All living organisms use and synthesis ATP in different ways: Plants - photophosphorylation Yeast - glycolysis and fermentation Animals – glycolysis and respiration Varying amounts of ATP are produced in different reactions, as are the locations and requirements for oxygen. Plant and animal ATP synthesis both require the enzyme ATP snythase (ATPase).

Where does the energy come from? Photoautotrophs carry out photosynthesis to make large, complex molecules that contain chemical potential energy. This energy is used by these organisms, as well as consumers and decomposers. Respiration releases this energy, which is used to phosphorylate ADP to make ATP.

What does this diagram tell you What does this diagram tell you? Explain it to a partner in your own words.

The Stages of Respiration Glycolysis The link reaction Krebs cycle Oxidative phosphorylation

Stage Location Products of this stage Glycolysis Cystol (cytoplasm) Pyruvate The link reaction Matrix of Mitochondria Acetate Krebs cycle Decarboxylated and dehydrogenated acetate Oxidative phosphorylation Cristae of mitochondria ATP

The role of enzymes and coenzymes in respiration Respiration is an enzyme-controlled process. It relies on different enzymes and coenzymes. Dehydrogenase enzymes remove hydrogen from other molecules and make this hydrogen available to be passed on to coenzymes (this is important later). Decarboxylase enzymes hydrolyse the carboxyl group (COOH) from a molecule, usually producing CO2 FAD and NAD are coenzymes that act as hydrogen acceptors for the dehydrogenase enzymes. They are needed as enzymes are not as efficient at reduction reactions.

NAD A non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions NAD accepts two hydrogen atoms, along with their electrons. In this state, we say that NAD is reduced. When it loses electrions, it is oxidised.

Structure of NAD (nicotineamide adenine dinucleotide) Made of two linked nucleotides Nicotinamide ring can accept hydrogen atoms. These can split into hydrogen ions and electrons (later stage)