ENZYMES AND METABOLISM

Biochemistry Assignment 3 Enzymes and Metabolism

Biochemistry Assignment 3 Enzymes and Metabolism

Task 1 (P4)

1.1 Define the term; cellular respiration.

We all need energy to function and we get this energy from the foods we eat. The most efficient way for cells to harvest energy stored in food is through cellular respiration, a catabolic pathway for the production of adenosine triphosphate (ATP). ATP, a high energy molecule, is expended by working cells. Cellular respiration occurs in both eukaryotic and prokaryotic cells.

1.2Fill in the following table

Type of respiration

What it requires/uses

What it produces

Aerobic

Oxygen in the air is necessary for aerobic respiration

Six molecules of carbon dioxide (CO2) and six molecules of water (H2O), plus 36-38 molecules of ATP and heat.

ATP, H2O and co2

Adenosine tri phosphate

Anaerobic

The use of an electron transport system in a membrane and the synthesis of ATP via ATP synthase.

In plants, yeasts, and bacteria, anaerobic respiration results in the production of alcohol and carbon dioxide, a process that is exploited by both the brewing and the baking industries 

1.3 Explain the process of Aerobic respiration with reference to the stages involved:

Glycolysis

Link reaction

Krebs cycle

Oxidative phosphorylation

Aerobic respiration requires oxygen in order to generate energy (ATP). Although carbohydrates, fats, and proteins can all be processed and consumed as reactant, it is the preferred method of pyruvate breakdown in glycolysis and requires that pyruvate enter the mitochondrion in order to be fully oxidized by the Krebs cycle. The product of this process is energy in the form of ATP (adenosine triphosphate), by substrate-level phosphorylation, NADH and FADH2

Simplified reaction:

C6H12O6 (aq) + 6 O2 (g) ? 6 CO2 (g) + 6 H2O (l) + heat

?G = -2880 kJ per mole of C6H12O6

The negative ?G indicates that the reaction can occur spontaneously.

The reducing potential of NADH and FADH2 is converted to more ATP through an electron transport chain with oxygen as the "terminal electron acceptor". Most of the ATP produced by aerobic cellular respiration is made by oxidative phosphorylation. This works by the energy released in the consumption of pyruvate being used to create a chemiosmotic potential by pumping protons across a membrane. This potential is then used to drive ATP synthase and produce ATP from ADP and a phosphate group.

Biology textbooks often state that 38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system). However, this maximum yield is never quite reached due to losses (leaky membranes) as well as the cost of moving pyruvate and ADP into the mitochondrial matrix and current estimates range around 29 to 30 ATP per glucose.

Aerobic metabolism is up to 15 times more efficient than anaerobic metabolism (which yields 2 mol ATP per 1 mol glucose). They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells.

Glycolysis

Glycolysis is a metabolic pathway that takes place in the cytosol of cells in all living organisms. This pathway does not require oxygen, and can therefore function under anaerobic conditions. The process converts one molecule of glucose into two molecules of pyruvate (pyruvic acid), generating energy in the form of two net molecules ...