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BBS1001 Case 7 A little tale from long, long ago
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Case 7: A little tale from long, long ago What are mitochondria? functions( citric acid cycle), structure, cellular respiration.
They convert the energy stored in molecules into a form the cell can use.
Function: Produce heat, helps building hormones and blood, they store calcium and mediate
cell growth and death.
Movement: Mitochondria move via the microtubule track. Microtubules are polymers of
tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic
cells.
Diameter: 1 micrometer
The space between the membranes is called the intermembrane space, and the
compartment enclosed by the inner membrane is called the mitochondrial matrix. The
matrix contains mitochondrial DNA and ribosomes
o Mitochondrial DNA: Encodes for proteins specifically needed in the mitochondria
itself. Inherited from the mother.
- Complexes are made of subunits mitochondrial DNA, normal DNA and nuclear DNA
Cristea: Inner membrane with inward protrusions, selectively permeable by
transport proteins. Much area for reactions to take place through loops.
Cellular respiration: The supply of adenosine triphosphate (ATP) using chemical
energy from fuels such as sugars. Glucose gets broken
down in carbon dioxide and water
Glycolysis (cytoplasm): The breaking down of
glucose.
Net: 2 ATP, 2 NADH and 2 pyruvates
Energy requiring fase: Uses 2 ATP to break glucose
into 2 3-carbon groups with a phosphate
Step 1. A phosphate group is transferred from ATP to glucose, making
glucose-6-phosphate, by hexokinase. The addition of the phosphate also
traps glucose inside the cell since glucose with a phosphate can’t readily
cross the membrane.
Step 2. Glucose-6-phosphate is converted into its isomer, fructose-6-
phosphate.
Step 3. A phosphate group is transferred from ATP to fructose-6-phosphate,
producing fructose-1,6-bisphosphate. This step is catalysed by the enzyme
phosphofructokinase.
Step 4. Fructose-1,6-bisphosphate splits to form two three-carbon sugars:
dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate.
They are isomers of each other, but only glyceraldehyde-3-phosphate can
directly continue through the next steps of glycolysis.
Step 5. DHAP is converted into glyceraldehyde-3- phosphate. The two
molecules exist in equilibrium. Thus, all of the DHAP is eventually
converted.
Phosphofructokinase: Catalyses formation of the unstable, two-
phosphate sugar molecule, speeds up or slows down glycolysis in
response to the energy needs of the cell.
, Energy releasing fase: They get formed to pyruvate. This produces each 2
ATP and 1 NADH.
Step 6. Two half reactions occur simultaneously: 1) Glyceraldehyde-3-
phosphate (one of the three-carbon sugars formed in the initial phase) is
oxidized, and
2) NAD+ is reduced to NADH and H+. The overall reaction is exergonic,
releasing energy that is then used to phosphorylate the molecule, forming
1,3-bisphosphoglycerate.
Step 7. 1,3-bisphosphoglycerate donates one of its phosphate groups to
ADP, making a molecule ATP and turning into 3-phosphoglycerate in the
process.
Step 8. 3-phosphoglycerate is converted into its isomer, 2-
phosphoglycerate.
Step 9. 2-phosphoglycerate loses a molecule of water, becoming
phosphoenolpyruvate (PEP), this is an unstable molecule, poised to lose its
phosphate group in the final step of glycolysis.
Step 10. PEP readily donates its phosphate group to ADP making a second
molecule of ATP. As it loses its phosphate, PEP is converted to pyruvate, the
end product of glycolysis.
Pyruvate oxidation (matrix) : converts pyruvate into acetyl Coa, a two-carbon
molecule attached to Coenzyme A—producing an NADH and releasing one carbon
dioxide molecule in the process.
pyruvate dehydrogenase complex:
Step 1. A carboxyl group is snipped off of pyruvate and released as a
molecule of carbon dioxide, leaving behind a two-carbon molecule.
Step 2. The two-carbon molecule from step 1 is oxidized, and the electrons
lost in the oxidation are picked up by NAD+ to form NADH.
Step 3. The oxidized two-carbon molecule—an acetyl group—is attached to
Coenzyme A CoA, an organic molecule derived from vitamin B5, to form
acetyl CoA. Acetyl CoA is sometimes called a carrier molecule, and its job
here is to carry the acetyl group to the citric acid cycle.
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