BABS1201 Lecture Notes - Lecture 9: Oxidative Phosphorylation, Acetyl-Coa, Citric Acid Cycle
17 May 2018
School
Department
Course
Professor
BABS1201
13TH APRIL 2018
METABOLISM II
× In the bacterial cell, the two major steps of glycolysis and the Krebs cycle take place in the
cytoplasm, and oxidative phosphorylation takes place in the surrounding cell membrane
× In the eukaryotic cell, glycolysis takes place in the cytosol, and the Krebs cycle takes place
in the mitochondrial matrix (the fluid area of the mitochondria). Oxidative phosphorylation
takes place in the inner membrane
× Cellular respiration in eukaryotes occurs in the mitochondria, an organelle which has an
inner membrane, consisting of convolutions called cristae- this is where oxidative
phosphorylation takes place
× Our focus in cellular respiration- glycolysis
× What enzyme is produced by cells to convert a complex carbohydrate such as starch to
glucose? Amylase
× In the same way, proteins are converted to amino acids by proteases, and lipids are
converted to fatty acids by lipases
× Glycolysis is the breakdown of a molecule of glucose into two molecules of pyruvate
× Stages of glycolysis:
1. Investment stage-
1. Two molecules of ATP are consumed for each molecule of glucose
2. Glucose is converted to fructose-1,6,-biphosphate (do not need to recall
these names)
3. Fructose-1,6,-biphosphate is cleaved into two 3-carbonunits of
glyceraldehyde-3-phosphate
2. Harvesting stage-
1. Four molecules of ATP and two molecules of NADH are gained from each
initial molecule of glucose- this ATP is a result of substrate-level
phosphorylation
2. Glyceraldehyde-3-phosphate is oxidised to pyruvate
3. Conversion of pyruvate molecules into acetyl CoA:
- Pyruvate undergoes a transition stage before entering TCA cycle
- Three enzymes convert pyruvate into acetyl-Coenzyme A with the
help of a molecule of coenzyme A and NAD+
- For each molecule of pyruvate, 2 NADH is generated, and 2 CO2 are
released
- TCA cycle- aka the tricarboxylic acid cycle, citric acid cycle or Krebs cycle
× Function of the TCA cycle- to generate the reducing agents NADH and FADH2
for electron transport chain function
× Eight enzymes completely oxidise acetyl-Coenzyme A
× Acetyl-CoA gets oxidised and reduces NAD+ to NADH, and FAD to FADH2,
with carbon dioxide as a waste by-product
- Oxidative phosphorylation
× NADH and FADH2 provide electrons to establish a proton gradient across a
membrane, resulting in an electrical potential difference across the
membrane
× A proton motive force drives protons across the membrane, through the
proton channel of ATP synthase, resulting in ATP synthesis
- Electron transport chain & chemiosmosis
× ETC consists of four large protein complexes and two smaller mobile
carriers- the function of the protein complexes is just facilitated diffusion,
providing ports for the travel of ions across a membrane)
Document Summary
In the bacterial cell, the two major steps of glycolysis and the krebs cycle take place in the cytoplasm, and oxidative phosphorylation takes place in the surrounding cell membrane. In the eukaryotic cell, glycolysis takes place in the cytosol, and the krebs cycle takes place in the mitochondrial matrix (the fluid area of the mitochondria). Oxidative phosphorylation takes place in the inner membrane. Cellular respiration in eukaryotes occurs in the mitochondria, an organelle which has an inner membrane, consisting of convolutions called cristae- this is where oxidative phosphorylation takes place. In the same way, proteins are converted to amino acids by proteases, and lipids are converted to fatty acids by lipases. Glycolysis is the breakdown of a molecule of glucose into two molecules of pyruvate. Pyruvate undergoes a transition stage before entering tca cycle. Three enzymes convert pyruvate into acetyl-coenzyme a with the help of a molecule of coenzyme a and nad+
