Most of the energy harvested from organic molecules during glycolysis and the Krebs Cycle is stored as high energy electrons present in the molecules of NADH and FADH2 . Molecules, such as, NADH and FADH2 give up their high energy electrons in the third stage of cellular respiration, which consists of the electron transport chain and ATP-synthase. During this stage most of the cell's energy, in the form of ATP, is produced.
Embedded in the inner membrane of the mitochondria are specialised proteins that form the Electron Transport Chain (ETC).
Electrons from the products of the Krebs Cycle, namely, NADH and FADH2 move through the ETC. Hydrogen ions and electrons break off their carrier molecules (NADH or FADH2) and once released, electrons facilitate the movement of hydrogen ions across the inner membrane through the proteins of the ETC from the mitochondrial matrix to the intermembrane space. When the electron has spent all its energy moving down the ETC it binds to an oxygen atom. When the oxygen atom has accepted two electrons two hydrogen ions bond to the oxygen atom to form water, as shown on the left.
The movement of hydrogen ions from the mitochondrial matrix to the intermembrane space causes a large build up of hydrogen ions in the intermembrane space. This huge difference in ion concentration between the mitochondrial matrix and the intermembrane space is a source of potential energy. Hydrogen ions move down a concentration gradient through the ATP-synthase protein. This provides the energy to drive the reaction ADP + Pi => ATP thus creating 32 ATP molecules.
Inputs for the Electron Transport Chain are NADH, H+, ADP, FADH2, O2
Outputs: NAD+, ATP, FAD, H2O
1) During cellular respiration, birds flying use oxygen.
2) In aerobic respiration the final product of the electron transport chain combines with
3) The process that produces the largest number of ATP molecules is
4) a) The breakdown of glucose in aerobic respiration can be represented as occurring in three stages
as indicated on the right. Identify product Z.
b) Where does the electron transport stage take place?
5) Which of the following takes place during the electron transport stage of cellular respiration.
a) Electrons are passed along electron acceptors/a series of cytochromes.
b) Oxygen captures electrons, which are combined with hydrogen.
c)Carrier molecules give up hydrogen as it is passed along.
6) 2,4-dinitrophenol is a chemical that is toxic to mitochondria. When added to mitochondria this chemical allows
electron transport to occur but prevents the phosphorylation of ADP to ATP. The chemical achieves this by
breaking the essential link between electron transport and ATP synthesis. This toxin causes mitochondria to
produce heat instead of ATP. The greater the amount of toxin added, the quicker is its action.
a. If mitochondria are poisoned with 2,4-dinitrophenol by what process could a plant cell produce more
ATP?
7) The overall equation for aerobic cellular respiration is given below
C6H12O6 + O2 => 6CO2 + 6H2O;
Where is water produced in this reaction?
8) Consider the diagram on the right.
a)
The ETC is located in the
b) Water is formed in the
c) ATP synthase is located in the
d) Hydrogen ions are pumped from the
into the
e) The energy to pump hydrogen ions against a concentration gradient comes from
