Respiration tutorial Catherine Haworth

Use of ATP Cells need a supply of ATP molecules to act as an immediate energy source for many processes such as: active transport maintaining resting potential in neurones muscle contraction cell division and growth and most metabolic reactions

Need to respire Respiration is required to generate heat energy as well as supply ATP for muscle contraction (movement) in animals. Respiration is required to generate ATP for movement of sucrose in mass flow hypothesis in plants. Respiration is required to generate ATP for mitosis for replication in bacteria.

Structure of ATP ATPATP P P P P P P Adenine 3 phosphate groups ribose P P P P ADPADP 2 phosphate groups ribose Adenine

ATP = source of energy e.g. Used in movement of substances Used in physical movement

Mitochondria Greatly increases the surface area for attachment of enzymes For protein synthesis The outer membrane is permeable to small molecules such as sugars, salts and nucleotides The inner membrane is selectively permeable, which allows mitochondria to control the composition of the matrix Codes for protein Contains enzymes (proteins) ATP synthase

In micrographs the shape of mitochondia vary depending on which plane they are cut in.

StructureRole Matrix Fluid filled. Contains enzymes required for the link reaction and Krebs cycle. Cristae Folded inner membrane. Electron transport system takes place here. Cristae create a large surface area for ATP synthesis. ATP synthase (stalked particles) Enzyme required for phosphorylation ADP + Pi  ATP Outer membrane Controls the entry and exit of substances into and out of the mitochondria. Pyruvate, O 2, ATP move in; ATP and CO 2 move out.

Coenzymes in respiration NAD acts as a H carrier with the enzyme pyruvate dehydrogenase. Coenzyme A also works with pyruvate dehydrogenase to form acetyl coenzyme A. The enzyme will be inhibited by high NADH, ATP and acetyl coenzyme A. Can you think why this is useful?

The reactions occur in four stages: Glycolysis Link reaction Krebs cycle Electron transport chain

Overview animation Cellular respiration by Tom Diab Science Department, Saline High School

Glycolysis Link Krebs

Link Glycolysis Krebs Link

Krebs cycle Glycolysis Krebs Link

Glycolysis Krebs Link ETC Electron Transport Chain In the electron transport chain: Electrons are donated by reduced FAD and NAD along with H + ions. The electrons provide the energy needed to pump H + ions into the intermembrane space. A high concentration gradient of H + ions builds up and the only way the H + can return is via a pore linked to ATP synthase. This movement of H + ions is called chemiosmosis. It drives the synthesis of ATP. Once completed the H + ions and electrons join with oxygen to form water.

Intermembrane space H2OH2O Reduced NAD from link and Krebs NAD Matrix Reduced FAD from Krebs FAD H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H2OH2O ATP ADP + Pi ATP synthase O2O2

Roles of molecules in oxidative phosphorylation Electron carriers: – as they gain electrons they become reduced – as they lose electrons they become oxidised – energy released by the electrons as they pass along the chain is used to pump out H + ions Oxygen: the final electron acceptor, combines with H + ions to form water (H 2 O). Cristae: the infolded membrane, increases the surface area for enzyme attachment (site of ATPase). Chemiosmosis occurs across the membrane.

Aerobic respirationAnaerobic respiration ATPNADHFADH 2 Total ATPATP Glycolysis Link reaction (2  pyruvate) Krebs cycle (2 cycles) Total (  3)(  2) Total ATP

Aerobic respirationAnaerobic respiration ATPNADHFADH 2 Total ATPATP Glycolysis 4, Link reaction (2  pyruvate) Krebs cycle (2 cycles) Total 410 (X3)2(X2)382 Total ATP 43042

Theoretical versus real yield in aerobic respiration The theoretical yield is greater than the actual yield owing to: – leakage of H ions when passing across membrane – ATP is used in active transport of pyruvate – ATP is used to move H from cytoplasm into mitochondria

Lower yield because: no oxygen, no final electron acceptor, no oxidative phosphorylation no Krebs cycle no link reaction So only 2 ATP made in anaerobic respiration compared with 34 ATP in aerobic respiration

Anaerobic respiration in mammals versus yeast Both use glucose Reduced NAD is oxidised pyruvate  lactate pyruvate = H acceptor Enzyme: lactate dehydrogenase pyruvate  ethanal  ethanol ethanal = H acceptor Enzymes: ethanal dehydrogenase ethanol dehydrogenase

Respiratory substrate A respiratory substrate is a substance that can be respired to produce ATP. Lipids have the highest energy value (39 kJ g –1 ) due to the higher proportion of H to C and O. Carbohydrates and proteins have similar proportions of H to C and O, so have a similar energy value (17 kJ g –1 ).

Oxidative phosphorylation To the tune of californication: OE&feature=related More silly songs: qks