cellular respiration Flashcards
what is catabolic?
break down molecules, releasing energy
what is anabolic?
build complex molecules, consume energy
what is cellular respiration
- breakdown of organic fuels to make ATP (glucose/C6O12O6 + 6O2 -> 6CO2 + 6H2O + 30-32ATPs)
- energy ultimately comes from the sun
- potential energy stored in chemical bonds of food molecules -> energy currency of the cell
what is aerobic cellular respiration?
in the presences of oxygen, involves mitochondria
what are the stages of cellular respiration?
1) glycolysis
2) citric acid cycle (krebs cycle)
3) electron transport chain
what is ATP?
adenisone triphosphate
what is ADP?
adenosine diphosphate
how can you go between ATP and ADP and vice versa?
phosphorylation
how is potential energy stored in organic molecules?
covalent bonds
structure of mitochondria
Structure of a Mitochondrion
The mitochondrion is a double-membraned organelle with a unique structure that allows it to efficiently carry out its role in energy production.
Outer Membrane
Structure: Smooth and semi-permeable.
Function: It separates the mitochondrion from the rest of the cell, allowing small molecules and ions to pass through.
Inner Membrane
Structure: Folded into cristae, which increase the surface area.
Function: The inner membrane houses the electron transport chain (ETC) and the ATP synthase complexes. This is where ATP is produced via oxidative phosphorylation. The folds (cristae) maximize surface area, allowing for more ATP production.
Matrix
Structure: The inner compartment, enclosed by the inner membrane, contains enzymes, DNA, and ribosomes.
Function: The matrix is the site of the citric acid cycle (Krebs cycle), where energy is extracted from nutrients and transferred to electron carriers like NADH and FADH₂.
Intermembrane Space
Structure: The area between the outer and inner membranes.
Function: The intermembrane space is crucial for creating a proton gradient during the electron transport chain, which is used to drive ATP synthesis.
How Form Fits Function
Double Membrane Structure:
The double membrane provides compartmentalization, essential for the different stages of cellular respiration to occur in separate regions (matrix and inner membrane).
Cristae (Inner Membrane Folds):
The folds increase the surface area for the electron transport chain and ATP synthase complexes, enabling efficient ATP production.
Matrix Enzymes:
The enzymes in the matrix are essential for the Krebs cycle to break down nutrients and transfer energy to electron carriers like NADH, which are then used in the electron transport chain to make ATP.
Proton Gradient in the Intermembrane Space:
The creation of a proton gradient across the inner membrane is crucial for the synthesis of ATP via ATP synthase. This gradient is generated by the movement of protons during the electron transport chain.
In short, the mitochondrion’s structure—with its double membrane, cristae folds, matrix, and intermembrane space—is intricately designed to optimize energy production in the form of ATP, which is vital for cellular functions.
Understand the role of NAD+ and FADH in harvesting energy from organic molecules
- NAD+ and FAD serve as electron carriers that collect high-energy electrons from organic molecules during glycolysis and the citric acid cycle.
- They are reduced to NADH and FADH₂, which then carry the electrons to the electron transport chain.
- The energy from the electrons is used to create a proton gradient across the mitochondrial membrane, which powers ATP production.
- NADH generates more ATP than FADH₂ due to its entry point in the electron transport chain being higher, allowing it to pump more protons and create more ATP.
- Thus, NAD+ and FADH₂ are crucial in transferring energy from nutrients into a form (ATP) that cells can use for various functions.
- electron shuttles remove electrons from food and transfer to shuttles to electron transport chain
- NAD+ picks up electrons (e-)+ protons (H+) -> NADH
Substrate-Level Phosphorylation vs. Oxidative Phosphorylation
Substrate-level phosphorylation directly transfers a phosphate from a high-energy molecule (like PEP or succinyl-CoA) to ADP to form ATP, occurring in the cytoplasm (glycolysis) and mitochondrial matrix (Krebs cycle). It produces a small amount of ATP.
Oxidative phosphorylation, on the other hand, occurs in the inner mitochondrial membrane. It generates a large amount of ATP by using electron transport and a proton gradient created by NADH and FADH₂. This process involves ATP synthase and is the major source of ATP in cells.
In short, substrate-level phosphorylation provides quick, small ATP, while oxidative phosphorylation is more efficient, producing large amounts of ATP.
what are the catabolic pathways
fermentation, aerobic respiration
what is fermentation
partial degradation of sugars or other organic fuel in oxygen
what is alcohol fermentation
pyruvate -> ethanol
1) CO2 released from pyruvate -> acetaldehyde
2) acetaldehyde is reduced by NADH -> ethanol
what is lactic acid fementation?
pyruvate reduced directly by NADH -> lactate, regenerating NAD+ with no release of CO2
what are redox reactions?
oxidation-reduction
- transfer of one or more electrons from one reactant to another
- loss of electrons from one substance: oxidation
- addition of electrons: reduction
- reducing agent: electron donor
- oxidizing agent: electron acceptor
what is glycolysis?
series of reactions that breaks down glucose into 2 pyruvate molecules, which may go on to enter the citric acid cycle, + nets 2 ATP and 2 NADH per glucose molecule
what are the inputs and outputs of glycolysis?
input: glucose
outputs: 2 pyruvate + 2 ATP + 2 NADH
what links glycolysis to rest of cellular respiration?
- The acetyl-CoA produced from pyruvate processing enters the citric acid cycle, where more energy is extracted (in the form of NADH, FADH₂, and ATP) and further transferred to the electron transport chain for oxidative phosphorylation.
- Therefore, pyruvate processing serves as the crucial link between glycolysis and the citric acid cycle, ensuring the flow of carbon and electrons needed to generate ATP in the later stages of cellular respiration.
what is the krebs cycle?
1) acetyl-CoA combines with oxaloacetate forming citrate (citric acid)
2) series of chemical reactions - citrate oxidized releasing CO2, generating NADH + FADH2 as high-energy electron carriers
3) ATP production: direct production of one ATP (or GTP) per cycle
4) regeneration of oxaloacetate: prepares cycle to start again
what are the inputs and outputs of the krebs cycle?
inputs: 2 pyruvate -> 2 acetyl CoA, 2 oxaloacetate
into krebs cycle
outputs: 2 ATP, 8 NADH, 6 CO2, 2 FADH2
Explain the fate of the electrons released in glycolysis, pyruvate processing, and the Krebs cycle
Glycolysis: Electrons from glucose are transferred to NAD+, forming NADH, which carries them to the ETC.
Pyruvate Processing: Electrons from pyruvate are transferred to NAD+, forming NADH, which also carries them to the ETC.
Krebs Cycle: Electrons are transferred to NAD+ and FAD, forming NADH and FADH₂, which carry them to the ETC for ATP production.
Electron Transport Chain: The electrons are used to create a proton gradient, driving ATP synthesis and combining with oxygen to form water.
what happens during oxidative phosphorylation?
26-28 ATP made
1) electron transport chain
2) proton gradient formation
3) ATP synthesis via ADP synthase
- NADH + FADH2 transfer electrons to the electron transport chain. electrons move down the chain, losing energy
- electrons are passed to O2, reducing it to H2O
- along the electron transport chain, electron transfer causes protein complexes to move H+ from mitochondrial matrix in eukaryotes to the intermembrane space, storing energy as a proton-motive force
- as H+ diffuses back into the matrix through ATP synthase, its passage drives the phosphorylation of ADP to form ATP (chemiosmosis, use energy stored in protein gradient to drive ATP synthesis)
- ATP synthase found in membrane of mitochondria
