-
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:
- Exergonic
- 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
- Glycolysis
- 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?
Cytosol
-
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 CO2
- The 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?
Mitochondrial matrix
-
What does one Citric Acid produce?
- 2 CO2
- 1 ATP (GTP)
- 3 NADH
- 1 FADH2
- CoA 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
-
Oxidative Phosphorylation
- Generates ATP by adding P to ADP
- This is where the majority of ATP is produced
- Two steps:
- -Electron Transport Chain
- -Chemiosmosis
-
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
- Glycolysis
- Pyruvate Oxidation
-
Chemiosmosis
- 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
-
ATP Synthase
- 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?
- 31%
- 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
-
Hibernation
- 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
-
Anaerobic Respiration
- 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
-
Fermentation
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.
-
Biosynthesis
- 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
|
|
