-
Oxidation
- a substance that loses one or more electrons (and hydrogen atoms)to another is said to have undergone oxidation.
- A substance that looses an electron is said to be oxidized- and has acted as a reducing agent
- If ATP get oxidized the energy is released and its said reduced to ADP
-
Reduction
- the gain of electrons and (hydrogen atoms)
- A substance that gains electrons is reduced
- - and has acted as oxidizing agent
-
Redox reaction
- the process by which electrons are transferred from one molecule to another
- Hydrogen atom = Hydrogen ion plus electron
- A substance oxidized - its electrons traveling energetically downhill
-
Electron carriers
- Molecules that serve to transfer electrons from one molecule to another in ATP formation.
- Have the ability to oxidize or reduce other compounds by accepting or giving up hydrogen ions and electrons
- 2 Electron carriers in Cellular respiration: NAD+ and FAD
-
NAD+ Electron Carrier
- Its positive charge indicates that it has one less electron than it does protons
- •During a redoxreaction, NAD+ picks up one hydrogen atom and one single electron
- NAD+ + electron -> NAD
- NAD + hydrogen atom -> NADH
- NAD+ empty state
- NADH loaded state
-
Cellular respiration
- C6H12O6+ 6O2+ 36 ADP + 36P →6CO2+ 6H2O + 36 ATPThree main phases:
- •Glycolysis - 2ATP
- •The Krebs cycle - 2 ATP
- •The Electron Transport Chain 34 ATP
- Total net gain 36 ATP (2 ATP from glycolysis used up transporting 2 NADH produced into mitochondria)
cellular respi - also called oxygen-dependent or aerobic energy transfer
-
Glycolysis
- •Occurs in the cytosol
- •Does not require oxygen
- •Is universally found in all organisms
- •Yield per glucose molecule:
- 2 ATP
- 2 NADH
- 2 molecules of pyruvic acid
-
The pyruvic acid ( the transition step)
- is a derivative of a glucose that was phosparilated( a phosphate groupd added from ATP) into glucose 6-phospate. The end products of glycolysis , glucose 6-phospate broken into 2 three carbon sugar molecules pyruvic acids.
- Each paruvic acid combines with coenzyme A, forming acetyl CoAacetyl CoA enters the Krebs cycle
- 2 CO2 produced
- 2 NADH produced
-
Krebs cycle
- This reaction occurs twice for each pyruvic acid
- Acetyl CoA combines with oxaloacetic acid to produce citric acid.
- •Occurs in the inner compartment of the mitochondria
- •Two electron carriers(NAD+and FAD) are used
- •Yield per glucose molecule:
- –6 NADH
- –2 FADH2
- –2 ATP
- - 4 CO2
-
ETC
- •Occurs inside the inner membrane of mitochondria
- •Electrons are delivered by NADH and FADH2
- •A series of protein carriers pass electrons from one to the other until the final receptor, O2, is reached
- •As electrons are passed from carrier to carrier, energy is released and used to form ATP
-
-
•When NADH and FADH2 arrive at the inner membrane, they donate electrons to the first protein carrier
- •Each protein carrier donates electrons to the next carrier in line
- •Electrons keep moving because each carrier has a greater affinity for electrons than its uphill neighbor
- •A series of redoxreactions occurs
- Net gain 34 ATP
-
ATP production
- •As electrons pass through carrier proteins, the energy released is used to actively transport H+ions across the membrane (outer comparment in mitochondria)
- •A hydrogen ion concentration gradient is established (Hydrogen pumped against its concentration gradient)
- •ATP synthase protein complexes use the potential energy in this concentration gradient to generate ATP from ADP
-
The Role of Oxygen
- Oxygen is the final acceptor of the electrons that move through the electron transport chain
- •Oxygen has a great affinity for electrons and ‘pulls’ the electrons down the chain
- •Oxygen atom + 2 electrons + 2H+= H20
- •Electrons have to be removed from the transport chain in order for the process to continue
-
-
•When oxygen is not available, cells turn to fermentation
- •During fermentation, the pyruvic acid formed by glycolysisis reduced to alcohol (and CO2) or an organic acid such as lactate
- •This reaction is important because it uses NADH and regenerates NAD+, which keeps glycolysis going
-
Alcoholic fermentation
- •Fungi and some plants perform this anaerobic energy conversion
- •When yeast grow in the absence of oxygen, they produce alcohol as a by-product of glycolysis
- •Releases carbon dioxide
- Pyruvic acids converted to acetaldehyde(later converted to alcohol) and it takes on electrons from NADH so NAD+ can be used again in glycolysis.
-
Lactate Fermentation
- •Animals and some bacteria perform this anaerobic energy conversion
- •Pyruvic acid is converted to lactic acid
- •Is a short-term means of supplying energy
- •2 ATP are produced for each glucose molecule
- Pyruvic acid accepts the electrons from NADH and becomes lactic acid
-
Fermentation in Human Muscle Cells
- •Muscle contractions require ATP
- •When oxygen delivery to muscle cells cannot keep up with activity level, muscles must generate ATP through fermentation
- •For brief periods of time, the body can produce a good deal of ATP just from glycolysis
- •Their role is to supply enough energy to meet our needs until aerobic respiration can take over
- Sore muscles - lactic build up
-
Stored Energy
- •Cells have the capacity to store small amounts of ATP and can stockpile a molecule called phosphocreatine(PCr)
- •PCr acts as a reservoir of phosphate groups that can be used to produce ATP
- •When a person first starts to exercise, the small reservoirs of ATP/PCr provide the energy
- •After a few minutes, aerobic respiration provides most of the energy
|
|
