Two main pathways of cellular respiration
- Aerobic Respiration
- Anaerobic Respiration (fermentation- which is different from anaerobic)
What is the energy harvested during respiration used for?
To regenerate ATP
Cellular respiration can be described as:
- Catabolic- you're breaking stuff down
- deltaG<0- products will have lower free energy than reactants
Why is energy harvested in a stepwise manner
If glucose was oxidized all at once, too much energy would be lost
How are hydrogen atoms transferred to oxygen?
- They are passed to an electron carrier.
- NAD+ is the main electron carrier and is essentially a shuttle (NADH reduced)
Stages of Cellular Respiration
- Pyruvate Processing
- Citric Acid Cycle
- ETC & Oxidative phosphorylation
Reactants and Products of Glycolysis
- Glucose + 2 ATP + NAD+ --->
- 2 Pyruvate + 4 ATP (2 Net ATP) + 2 NADH
Reactants and Products of Pyruvate Processing
- Pyruvate + Coenzyme A + NAD+-->
- Acetyl CoA + CO2 + NADH
Reactants and Products of Citric Acid Cycle
- Acetyl CoA + H2O + 3 NAD+ + FAD ->
- 2 CO2 + H2O + 3 NADH + FADH2 + GTP (ATP)
Reactants and products of ETC & Oxidative Phosphorylation
- NADH + FADH2 + 1/2 O2 + ADP + Pi ->
- ATP + H2O + NAD+ + FAD
Where does glycolysis take place?
What does glycolysis do?
- Splits glucose into 2 molecules of pyruvate
- Requires 2 ATP but gives off 4 ATP (net yield of 2 ATP)
What happens to the pyruvate after glycolysis?
It is shuttled into the mitochondria
Initial input/Product of glycolysis
Outputs from glycolysis process
Inputs from glycolysis process
What is the net yield of ATP from glycolysis
Gain 2 ATP
Net yield of NADH
Gain of 2 NADH
3 steps in Pyruvate Processing
- Using a transport protein:
- The carboxyl group is removed to give off CO2The remaining 2-carbon is oxidized and the electrons lost is used to turn NAD+ into NADH
- Coenzyme A is added to form acetyl CoA (which has high potential energy
Inputs of pyruvate processing
- 2 pyruvate
- 2 coenzyme A
- 2 NAD+
Outputs of pyruvate processing
Net yield of NADH in pyruvate processing
Gain of 2 NADH
Where does the Krebs Cycle (Citric Acid Cycle) occur?
What does one Citric Acid produce?
- 2 CO2
- 1 ATP (GTP)
- 3 NADH
- 1 FADH2CoA and oxaloacetate are recycled
Where is most of the energy from glucose in cellular respiration?
- Most of energy extracted from glucose is tied up in NADH and FADH2
- It is in the electron carriers
A molecule that is phosphorylated...
has increased chemical potential energy; it is primed to do cellular work
During glycolysis for each mole of glucose oxidized to pyruvate:
2 moles of ATP are used and 4 moles of ATP are produced
- Generates ATP by adding P to ADP
- This is where the majority of ATP is produced
- Two steps:
- -Electron Transport Chain
Electron Transport Chain
- Collection of molecules embedded in the mitochondrial inner membrane
- Electrons are dropped off by NADH and FADH2
- Still not ATP Production from this
How does the electron transport chain work?
Electron carriers alternate between reduced and oxidized states as they accept and donate e-
What is the final electron acceptor in the electron transport chain?
Oxygen which also picks up 2 H+ ions to form H2O
Which pathways generate reduced electron carriers?
- Citric Acid cycle
- Pyruvate Oxidation
- Diffusion of ions (H+) down their electrochemical gradient to generate ATP
- Exergonic flow of electrons is used to pump H+ across the membrane (into the intermembrane space)
- -generates a gradient= proton motive force
What does the chemiosmotic synthesis of ATP require?
The electron transport in the inner mitochondrial membrane be couple to proton transport across the same membrane
- Uses energy of the H+ gradient to power ATP synthesis
- -Located in the mitochondrial inner membrane
How does ATP Synthase work?
- H+ ions flow through ATP synthase down their concentration gradient
- -bind to active sites and cause conformational change= rotor spins
- -this activates catalytic sites that generate ATP
During aerobic respiration, electrons travel downhill in which sequence?
Food -> NADH -> Electron Transport Chain -> Oxygen
What is the actual yield of ATP after cellular respiration?
What is the theoretical yield?
In cellular respiration, the energy for most ATP synthesis is supplied by?
A proton gradient across a membrane
What percentage of potential energy of glucose is transferred to ATP?
- The rest is given off as heat
Why are carbohydrates and fats considered high energy foods?
They have a lot of electrons associated with hydrogen
- Animals can reduce the efficiency of respiration
- Brown fat contains cells full of mitochondria
- -the inner membrane contains an uncoupling protein which allows H+ to flow back down their concentration gradient without generating ATP
- -This allows the oxidation of stored fuel to generate heat without buildup of ATP
What would happen if animals couldn't hibernation?
ATP would accumulate (since the animal's metabolism is low) and respiration would be shut down due to control mechanisms
Drugs known as uncouplers facilitate diffusion of protons across the membrane when such a drug is added, what happens to ATP synthesis & oxygen consumption, if the rates of glycolysis and citric acid cycle same?
ATP synthesis will decrease, oxygen consumption stays the same
- Still uses an electron transport chain but oxygen is not the final electron acceptor
- Other substances can include Iron, Sulfate ion, or carbon dioxide
- Can also use different electron donors.
- -glucose doesn't have to be the starting material
Process to generate energy without using oxygen or an electron transport chain
What does fermentation use to allow glycolysis to continue if no oxygen is present?
- Metabolic pathway to regenerate NAD+
- (you need NAD+ to pick up electrons, so glycolysis can keep running)
What happens in alcohol fermentation
- Pyruvate is reduced to ethanol
- NADH is going to be oxidized to be NAD+
What is alcohol fermentation used for?
Used by some bacteria and yeast to make beer, wine, liquor, and bread.
What happens in lactic acid fermentation?
Pyruvate is reduced directly by NADH to form lactate
Why do muscles use lactic acid fermentation?
Muscle cells use this process when supply of oxygen can't keep up with energy demand
What is happening when you are deprived of oxygen?
- Lack of ATP production
- No oxygen means nothing to pick up electrons at the electron transport chain and electrons back up
Why can't your cells just switch over to fermentation?
It doesn't produce enough ATP to sustain your energy requirement for your body
A gram of fat produces 2x the ATP generated from 1 g of carbohydrate. Why?
Why does this make it hard to lose weight?
- There are more hydrogens in fat
- Since fat produces 2x ATP, you have to work out twice as hard to burn it.
- Simple compounds are modified, converted into other compounds, or joined together to form macromolecules.
- It is anabolic because it requires energy
How is cellular respiration regulated?
- Follows principles of supply and demand
- Prevents cell from wasting energy making something it already has
- The main mechanism of control is feedback inhibition
What is the probably effect on ATP production of a low-calorie diet?
ATP production would remain constant as stored fats or other body molecules are oxidized
You have a friend who lost 7 kg (15 lbs) of fat on a regimen of strict diet and exercise. How did the fat leave her body?
It was released as CO2 and water