W4 Cellular energetics/Lec 6 Flashcards
Dr Nannetti
What is meant by catabolism?
Breaking down.
Large food molecules are broken down into smaller molecules (monomers)
What is meant by anabolism?
Building up.
What is cellular respiration?
A process that breaks down sugars and other metabolites to CO2 and water. Converts the energy released from food into the build-up of ATP.
What is ATP used in the cell for?
- An energy currency used to drive a variety of chemical reactions in cells (also GTP)
- Hydrolysis of high-energy phosphate bonds release energy to fuel cellular processes/reactions
Can ATP be recycled?
ATP can be converted into ADP and recycled back (same for GTP/GDP)
Cells break phosphate bonds of ATP to supply energy
What are the most common electron carriers? (coenzymes)
- NAD+ and FAD
What do coenzymes do during cellular respiration?
What are they reduced into?
What do they transfer?
They act as oxidising agents and are reduced into NADH and FADH2
Their reduced forms transfer protons and electrons to other molecules and represent stored energy used to synthesise ATP
What are the 4 stages of aerobic respiration?
Glycolysis
Link reaction (Pyruvate oxidation to form acetyl-CoA)
Krebs/ Citric acid cycle
Oxidative Phosphorylation
Where does Glycolysis occur?
In the cytoplasm
Where does the Link reaction, Krebs cycle and Oxidative phosphorylation occur?
In the mitochondrial matrix
What happens during Glycolysis?
The “Splitting of Glucose”
Glucose is broken down into 2 molecules of pyruvate
Generating 2 ATP and 2 NADH
Consists of 10 different reactions with 10 enzymes
Does Glycolysis require oxygen?
No. It is an anaerobic process
What happens to Pyruvate under anaerobic conditions?
What is restored?
Remains in cytosol (in the cytoplasm) and undergoes fermentation (Lactate or Ethanol production)
No energy production occurs but it restores the NAD+ consumed in glycolysis so it can continue
What happens to Pyruvate under aerobic conditions
Transported into the mitochondria for aerobic respiration to continue
What could also happen to Pyruvate to resynthesise glucose
Gluconeogenesis- An anabolic pathway to synthesise glucose (reverse to glycolysis).
Can occur when glycogen store starts to deplete
What happens during lactate fermentation?
Pyruvate is reduced to lactic acid. Occurs in muscle cells (human) when oxygen is not adequate (physical activities)
Lactic acid can build up causing cramps
What happens in ethanol fermentation?
What cells does it occur in?
Used to produce what?
Pyruvate is reduced to ethanol & CO2.
Occurs in bacteria and heat cells (NOT HUMAN)
Used to produce alcoholic spirits, bread
Mitochondria function
Contains enzymes responsible for ATP production (Krebs cycle, oxidative phosphorylation)
What happens during the link reaction (pyruvate oxidation)
Links glycolysis to Krebs cycle
In presence of O2, pyruvate produced by glycolysis is actively pumped into the mitochondrial matrix
Pyruvate converted to a 2 carbon acetyl group (acetate)
Attaches to Coenzyme A to form Acetyl Co-A
Electron picked up by NAD+ to form NADH
CO2 released outside the mitochondria
What happens during the Citric Acid (Krebs) Cycle?
Where does it occur?
What is the net gain?
-Occurs in the mitochondrial matrix
-Consists of a cycle 8 reactions.
-Acetyl CoA is added to oxaloacetate (4C) forming citric acid. In each cycle:
- The acetyl group of acetyl CoA is fully oxidised into CO2 and water
- Oxaloacetate is regenerated
- 2 turns for one glucose molecule (1 glucose generates 2 pyruvate/acetyl CoA
Net result: 4 CO2, 2 GTP, 6 NADH, 2 FADH2
What are the 2 stages of Oxidative Phosphorylation?
Electron transport chain and Chemiosmosis
What happens during Chemiosmosis?
Electrons are pumped from the matrix to the inter membrane space, generating a proton gradient across the inner membrane (chemiosmosis)
ADP is pumped into the matrix and ATP is pumped out by an antiport process
What happens during the Electron Transport Chain?
NADH and FADH2 transfer their high-energy electrons to the the electron transport chain.
Passage of electrons through the complex
Electrons drop in free energy as they go through the chain and are passed to O2 that combine with protons forming H2O
Which molecule enters the citric acid cycle?
Acetyl CoA
What process converts glucose into 2 molecules of pyruvate?
Glycolysis
How many ATP molecules are generated in glucose catabolism?
30-32 Net yield
