Cellular Respiration Flashcards
What is the main purpose of cellular respiration?
To break down food molecules to produce ATP
Cellular respiration includes catabolic reactions.
What is the key equation for cellular respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + Chemical Energy (ATP)
This equation summarizes the overall process of cellular respiration.
Where does energy originate in the context of cellular respiration?
From the Sun, captured via photosynthesis
Energy is stored in sugars.
How is energy in glucose harnessed during cellular respiration?
By transferring electrons through a series of redox reactions
This process powers ATP synthesis.
What are the three main stages of cellular respiration?
- Glycolysis
- Pyruvate Oxidation and Citric Acid Cycle
- Oxidative Phosphorylation
Each stage has distinct processes and occurs in different cellular locations.
Where does glycolysis occur?
In the cytosol
Glycolysis converts glucose into two pyruvate molecules.
What are the products of glycolysis?
2 ATP (net) and 2 NADH
Glycolysis is an anaerobic process.
What happens during pyruvate oxidation?
Pyruvate is converted into Acetyl-CoA
This occurs in the mitochondrial matrix.
What does Acetyl-CoA enter after pyruvate oxidation?
The citric acid cycle (Kreb’s Cycle)
This cycle produces NADH, FADH2, ATP, and CO2.
What is oxidative phosphorylation?
Involves the electron transport chain (ETC) and chemiosmosis
It is the final stage of cellular respiration.
What role do NADH and FADH2 play in oxidative phosphorylation?
They provide high-energy electrons to the electron transport chain
This process creates an electrochemical gradient.
What is chemiosmosis?
The movement of H+ down their concentration gradient through ATP synthase
This movement powers ATP production.
Who is the terminal electron acceptor in cellular respiration?
O2
It becomes reduced to H2O.
Fill in the blank: Glycolysis converts glucose into _______.
two pyruvate molecules
Each pyruvate molecule has 3 carbons.
True or False: Glycolysis can occur in the absence of oxygen.
True
This is why it is classified as an anaerobic process.
What are the two mechanisms of ATP production?
- Substrate-level phosphorylation
- Oxidative phosphorylation
Define substrate-level phosphorylation.
Direct transfer of phosphate to ADP
What is oxidative phosphorylation?
ATP synthase uses energy from the proton gradient
Which mechanism produces the most ATP?
Oxidative phosphorylation
What is the Electron Transport Chain (ETC)?
A series of protein complexes and mobile electron carriers involved in oxidative phosphorylation during cellular respiration
Occurs in the inner mitochondrial membrane in eukaryotes and the plasma membrane in prokaryotes.
What are the primary electron sources for the ETC?
Electrons harvested from glucose during glycolysis, pyruvate oxidation, and the citric acid cycle, carried by NADH and FADH2
NADH and FADH2 are oxidized back to NAD* and FAD.
What happens to NAD* and FAD after donating their electrons?
They are recycled back to glycolysis and the citric acid cycle to get reduced and repeat the cycle.
What are the key components of the ETC?
Complexes I, II, III, IV
These complexes facilitate the movement of electrons via redox reactions.
How do electrons move through the ETC?
Via a series of redox reactions through protein complexes, with each complex having a higher affinity for electrons than the previous one.
What happens to the energy of electrons as they move down the ETC?
They lose free energy, which is used to pump protons (H+) across the inner mitochondrial membrane.
What is created as a result of protons being pumped across the inner mitochondrial membrane?
An electrochemical gradient, known as the proton motive force.
What is the role of oxygen in the ETC?
It accepts electrons and combines with H* ions to form water (H2O), acting as the terminal electron acceptor.
What would happen to the ETC without oxygen?
The chain cannot operate, halting ATP production.
Fill in the blank: The energy released as electrons flow is used by Complexes I, III, and IV to pump _______ ions.
H+
What two types of potentials contribute to the proton motive force?
Chemical Potential and Electrical Potential
Chemical potential refers to the high concentration of H+ in the intermembrane space, while electrical potential refers to the positive charge in the intermembrane space relative to the matrix.
True or False: The electrons start at a very low energy level when they are associated with NADH or FADH2.
False
What happens to electrons by the time they reach the terminal electron acceptor?
They are at a very low energy level.
What drives the rotation of ATP synthase?
Protons flow back into the matrix through ATP synthase
This flow of H+ acts like a turbine, enabling ATP synthesis.
What is the primary function of ATP synthase?
Catalyzes the phosphorylation of ADP to ATP
ATP synthase converts ADP into ATP using the energy from the proton gradient.
Which electron carrier contributes more energy to proton pumping?
NADH
NADH enters the electron transport chain at Complex I, while FADH2 enters at Complex II.
At which complex does FADH2 enter the electron transport chain?
Complex II
FADH2 contributes less energy compared to NADH due to its entry point.
What ensures efficient energy capture in the electron transport chain?
The gradual energy drop of electrons
This process minimizes excessive heat loss during energy transfer.
What are the key molecules involved in respiration?
- NADH
- FADH2
- ATP Synthase
NADH and FADH2 shuttle high-energy electrons, while ATP synthase generates ATP.
What process allows ATP synthase to generate ATP?
Passive flow of H+ ions down their concentration gradient
This process utilizes the free energy released during the flow.
What is feedback inhibition in the context of respiration?
Products of the pathway inhibit upstream enzymes, ensuring regulation based on cellular energy needs.
What is lactate fermentation?
Produces lactic acid (in animals and some bacteria).
What is alcoholic fermentation?
Produces ethanol and CO2 (in yeast).
What is the primary reason fermentation exists?
To recycle NAD+ molecules.
Why does NADH accumulate in the absence of oxygen?
Because NADH can’t donate its electrons to the ETC.
What happens to NAD+ in the absence of oxygen?
NAD+ molecules become depleted, preventing glycolysis and the citric acid cycle from proceeding.
What is the end result of depleted NAD+ during respiration?
No ATP production.
Where does respiration occur in prokaryotes?
In the cytoplasm and plasma membrane.
What are the types of organisms based on their oxygen requirements?
Strict aerobes, strict anaerobes, and facultative anaerobes.
Fill in the blank: Fermentation is an alternative pathway when _______ is unavailable.
oxygen
What are Reactive Oxygen Species (ROS)?
Byproducts of aerobic respiration that can damage cells
ROS are harmful and require management by the cell’s antioxidant systems.
How are Reactive Oxygen Species (ROS) managed in cells?
Managed by antioxidant systems like enzymes (e.g., catalase)
Antioxidant systems help neutralize ROS to prevent cellular damage.
True or False: Anaerobic prokaryotes cannot use oxidative phosphorylation.
False
Some anaerobic prokaryotes use molecules other than O2 as the terminal electron acceptor.
Fill in the blank: Some anaerobic prokaryotes are able to use oxidative phosphorylation because they use _______ as the terminal electron acceptor.
[molecules other than O2]
