Download The Krebs Cycle - County Central High School

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Cellular Respiration Notes
Use your textbook or cell phones to find the following information:
Define the following terms:
Glycolysis
Mitochondrion
Mitochondrial Matrix
Krebs Cycle
Oxidative ATP Synthesis
Alcohol Fermentation
Lactic Acid
Fermentation
Maximum O2
Consumption
Lactic Acid Threshold
A process for harnessing energy in which a glucose
molecule is broken into two pyruvate molecules in the
cytoplasm of a cell
A eukaryotic cell organelle in which aerobic cellular
respiration occurs
The fluid that fills the interior space of the
mitochondrion
A cyclic series of reactions that transfers energy from
organic molecules to ATP, NADH, and FADH2, and
removes carbon atoms as CO2
The production of ATP from a series of oxidation
reactions
A form of fermentation occurring in yeast in which
NADH passes its hydrogen atoms to acetaldehyde,
generating carbon dioxide, ethanol and NAD+
A form of fermentation occurring in animal cells in
which NADH transfers its hydrogen atoms to pyruvate,
regenerating NAD+ and lactic acid
The maximum volume of oxygen, in mL, that the cells
of the body can remove from the bloodstream in one
min/kg of body mass while the body experiences
maximal exhertion
The value of exercise intensity at which lactic acid
production increases
Glycolysis: Stage One of Cellular Respiration (pages 210-212)
Fill in the blank:
Both aerobic and anaerobic respiration begins with the process of glycolysis.
Glycolysis is Greek for sugar-splitting and this accurately describes what is
happening during this stage of cellular respiration. The carbon backbone of
glucose is essentially split in half. Glucose is a 6 carbon sugar and at the end of
glycolysis, it has been converted to a 3 carbon sugar called pyruvate.
Label 
Glycolysis does not require oxygen to work. It takes place in the cytoplasm of
the cell. There are 10 reactions in glycolysis that is each catalyzed by a specific
enzymes in the cytoplasm. During these reactions 2 ATP molecules are used and
4 ATP molecules are produces. Therefore, glycolysis produces a net total of 2
ATP. It also produces 2 NADH+ ions.
Label 
Explain the key events shown above: (page 211)
-
2 ATP molecules are used in the first stages
NAD+ ions remove H+ atoms from the pathway creating NADH and
release 2 H+ ions into the cytoplasm
4 ADP molecules join with 4 P molecules to form 4 ATP
When finished, the cell has taken a single glucose molecule and made 2
ATP, 2 NADH, and 2 pyruvate
ATP is now available for other cell functions
Fill in the table below: (page 211)
Reactants
Glucose
2 NAD+
2 ATP
4 ADP
Products
2 pyruvate
2 NADH
2 ADP
4 ATP
Write the net equation of glycolysis below:
1 glucose + 2 ADP + 2 P + 2 NAD+  2 pyruvate + 2 ATP + 2 NADH + 2 H+
Glycolysis only transfers about 2.2% of the free energy available in glucose to
ATP. Some of the energy is released as thermal energy but the vast majority is still
trapped in the 2 pyruvate and 2 NADH molecules.
Mitochondria
Draw and label a mitochondrion below:
Why is this organelle so important for cellular respiration?
It is important because it is where 3 of the stages occur and it is the power-house
of the cell creating large quantities of ATP
Stage 2: Pyruvate Oxidation
After glycolysis, the cell had formed:
- 2 ATP
- 2 NADH
-2 Pyruvate
Pyruvate oxidation connects stage one (glycolysis) and stage two (Krebs cycle).
There are three changes that occur in this stage, explain them below:
1. A CO2 is removed from each pyruvate and released as waste
2. The remaining 2 carbon portions are oxidized by NAD+ and H atoms from
pyruvate reduce NAD+ molecules. The remaining 2 carbon molecule
becomes an acetyl group.
3. CoA attaches to acetyl groups formed above to create a 2 carbon
molecule called acetyl-CoA
The products of pyruvate oxidation are:
1. CO2
2. NADH
3. acetyl CoA
Stage Three: The Krebs Cycle
Fill in the blank:
In 1937 Sir Hans Kreb discovered the series of metabolic reactions that became
known as the Krebs cycle.
The Krebs cycle is an 8 step process that is each catalyzed by a specific
enzyme.
Explain the key features of the cycle below:
-
the Krebs cycle occurs twice for each molecule of glucose processed
-
as acetyl-CoA enters the cycle the CoA is released
-
during one complete cycle, a total of 3 NAD+ and 2 FAD are reduced to
form 3 NADHs and 1 FADH2
-
during one complete cycle, 1 ATP is formed
-
during one complete cycle, 2 CO2 molecules are produced and released
as waste
MEMORIZE
ME!
Label 
By the end of the Krebs cycle, all 6 carbon molecules that were found in glucose
have now been oxidized into CO2 and released as waste from the cell. All that is
left of the original glucose is free energy in the form of ATP, NADH, and FADH2.
Stage 4: Electron Transport and Chemiosmosis (pages 216-218)
Fill in the blank:
NADH and FADH2 eventually transfer the hydrogen atom electrons they carry to
a series of compounds, mainly proteins, in the inner mitochondrial membrane
called the electron transport chain (ETC). The NADH gives up 2 high energy
electrons at the beginning of the ETC. At the same time, it releases 1 H+ ion into
the matrix. The electrons move down the ETC using carrier molecules and they
are releasing energy as they move. This energy is used to force a number of H+
ions from within the mitochondrial matrix across the inner membrane. By the
time the two electrons reach the last component of the ETC, they are in a low
energy state. Oxygen strips the two electrons from the final carrier in the chain
and together with two H+ ions, from the matrix form water. Oxygen acts as the
final electron acceptor in this electron transport process. This final step is the
reason many organisms require oxygen.
The electron transport chain has a similar process for FADH2 molecules that
come over to it. The ETC converts chemical energy of electrons into
electrochemical potential energy of an H+ gradient. This energy being formed
by H+ ions is what is used in chemiosmosis and ATP synthesis.
Chemiosmosis and ATP Synthesis
Remember back to photosynthesis:
- Chemiosmosis uses H+ ions travelling through a protein (ATP synthase) to create
energy (ATP)
Read and Highlight:
H+ ions from the ETC pass through ATP
synthase in the mitochondrial
membrane and this passage of ions
releases energy that allows ADP to
bind with a P ion to form ATP.
This specific formation of ATP is called
oxidative ATP synthesis because it
results from a series of oxidation
reactions.
After ATP is formed, it is transported
through both mitochondrial
membranes into the cytoplasm where
it is used to drive processes that require
energy like movement, active
transport, and other reactions in the
cell.
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