Cellular Respiration

1
Cellular Respiration

• The second stage of cellular respiration is the
  Krebs cycle, which operates only when oxygen is
  available.
• Because it depends on oxygen, it is an aerobic
  process.
• It is named after its discoverer Hans Krebs.
• The Krebs cycle takes place in the innermost
  compartment of the mitochondrion called the matrix

2
Mitochondrion
3
Hans KrebsDiscovered Krebs cycle in 1937Won
Nobel Prize in 1953
4
Cellular Respiration

• Pyruvic acid molecules, produced by glycolysis,
  enters the matrix and are broken down through
  chemical reactions resulting in the production of
  citric acid.
• Because this is the first product made, it is
  also called the Citric Acid Cycle.
• Along with the production of citric acid, it also
  releases carbon dioxide (CO2).

5
Cellular Respiration

• During the cycle, energy is released by the
  breaking and rearranging of carbon bonds and is
  captured in ATP, NADH, and FADH2.
• Once the Krebs cycle is complete, the cell goes
  on to derive the majority of its ATP from the
• electron transport chain.

6
Cellular Respiration Krebs cycle
7
Steps in Cellular Respiration Location What goes in What comes out ATP Results
(1) Glycolysis Anaerobic process Cytoplasm (cytosol) one Glucose 2 ATP to start 2 pyruvic acids 2 NADH 4 produced for a net gain of 2 ATP
(2) Krebs cycle (Citric Acid cycle) Aerobic process Mitochondrial Matrix 2 pyruvic acids C02, 4 NADH, 2 FADH2 2 ATP
(3) Electron Transport Chain   Inner Mitochondrial Membrane (cristae) NADH, FADH2, oxygen Water NAD (recycled) FAD (recycled) 32-34 ATP
Total       36-38 ATP
8
(No Transcript)
9
Cellular Respiration

• Electron Transport Chain
• The electron carriers produced during glycolysis
  (NADH) and the Krebs cycle (NADH and FADH2) bring
  high-energy electrons to the electron transport
  chain.
• The passing of electrons through the electron
  transport chain causes H ions to build up in the
  intermembrane space, making it positively charged
  relative to the matrix.

10
Cellular Respiration

• Electron Transport Chain
• The charge difference across the membrane forces
  H ions through channels in enzymes known as ATP
  synthases. As the ATP synthases spin, a phosphate
  group is added to ADP, generating ATP.
• At the end of the chain the electrons are taken
  up by oxygen molecules, along with hydrogen
  atoms, to make water.
• This is why oxygen is known as the final electron
  acceptor.

11
Cellular Respiration

• Electron Transport Chain
• The electron transport chain is the stepwise
  process of cellular respiration that is
  responsible for producing
• Water (with the help of oxygen we breathe)
• 32 to 34 ATP (thanks to the proton, H ,
  gradient)
• NAD and FAD (which are recycled to be used
  again in the Krebs cycle and glycolysis)

12
Cellular Respiration

• Electron Transport Chain
• This process happens in the mitochondria along
  the inner membrane called the cristae.

13
Cellular Respiration

• Electron Transport Chain
• To put things in perspective think about how we
  breathe in oxygen with our lungs, transport it
  with red blood cells in our arteries to cells,
  and the oxygen is ultimately used inside the
  mitochondria of every cell to accept electrons at
  the end of the electron transport chain.

14
Cellular Respiration

• Electron Transport Chain
• For Prokaryotes, which dont have mitochondria,
  this process happens in the cell membrane.

15
Cellular Respiration Electron Transport
16
Cellular Respiration
17
Cellular Respiration
18
Fermentation

• Fermentation is an anaerobic process that
  converts NADH back to NAD, thus producing
  energy.
• Eukaryotic cells
• (1) Lactic Acid Fermentation
• Lactic acid is produced in muscles during
  rapid exercise.
• This is because the body cannot supply enough
  oxygen to the tissues to produce the needed ATP.

19
Fermentation

• A buildup of lactic acid causes a burning
  sensation in the muscles.
• (2) Alcoholic fermentation
• It occurs in yeast.
• It produces alcohol and carbon dioxide(CO2).
• The CO2 is what causes dough to rise, air
  spaces in bread, and bubbles in alcoholic
  drinks.

20
Fermentation

• Prokaryotic cells
• Some types of bacteria produce alcohol and CO2.
• Other kinds of bacteria produce lactic acid.

21
Fermentation