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
where did glycolysis evolve from?
ancient prokaryotes before O2 in atmosphere
what are obligate anaerobes?
carry out only fermentation or anaerobic respiration (can’t survive in O2)
what are faculative anaerobes?
can make enough ATP to survive using fermentation or respiration
where is ATP synthase found
synthesizes ATP from ADP through chemiosmosis, membrane of mitochondria or cellular membrane for prokaryotes
explain the role of facilitated diffusion and active transport in oxidative phosphorylation
Facilitated Diffusion: Protons (H⁺) move through the ATP synthase complex (via the F₀ component) from the intermembrane space to the mitochondrial matrix down their concentration gradient. This movement provides the energy for ATP synthesis.
Active Transport: During the electron transport chain, protons are actively pumped from the matrix to the intermembrane space through the ETC complexes (I, III, and IV), using energy from the electrons passing through the chain. This creates the proton gradient necessary for ATP synthesis by facilitated diffusion.
Calculate the number of ATP produced by a cell via aerobic respiration
From Glycolysis:
2 ATP (directly from glycolysis) + 5 ATP (from NADH) = 7 ATP
From Pyruvate Processing:
0 ATP (no direct ATP from this step) + 5 ATP (from NADH) = 5 ATP
From Krebs Cycle:
2 ATP (directly from Krebs cycle) + 15 ATP (from NADH) + 3 ATP (from FADH₂) = 20 ATP
Total ATP (from all stages):
7 ATP (glycolysis) + 5 ATP (pyruvate processing) + 20 ATP (Krebs cycle) = 32 ATP
Explain why the electrons in NADH are responsible for making more ATP than the electrons in FADH2
NADH donates electrons at Complex I, which actively pumps protons, generating a larger proton gradient and leading to the production of more ATP (2.5 ATP per NADH).
FADH₂ donates electrons at Complex II, which does not pump protons, resulting in a smaller proton gradient and less ATP production (1.5 ATP per FADH₂).
know the cellular location of each stage of cellular respiration in eukaryotes and prokaryotes
- Glycolysis
Eukaryotes: Cytoplasm
Prokaryotes: Cytoplasm
Explanation: Glycolysis occurs in the cytoplasm of both eukaryotic and prokaryotic cells, where glucose is broken down into pyruvate. - Pyruvate Processing (Link Reaction)
Eukaryotes: Mitochondrial Matrix
Prokaryotes: Cytoplasm (since prokaryotes lack mitochondria)
Explanation: In eukaryotes, pyruvate is transported into the mitochondria, where it is converted into acetyl-CoA. In prokaryotes, pyruvate processing occurs in the cytoplasm because they don’t have mitochondria. - Krebs Cycle (Citric Acid Cycle)
Eukaryotes: Mitochondrial Matrix
Prokaryotes: Cytoplasm
Explanation: The Krebs cycle occurs in the mitochondrial matrix in eukaryotes. In prokaryotes, it takes place in the cytoplasm, as they do not have mitochondria. - Electron Transport Chain (ETC)
Eukaryotes: Inner Mitochondrial Membrane
Prokaryotes: Plasma Membrane
Explanation: In eukaryotes, the ETC is located in the inner mitochondrial membrane. In prokaryotes, which lack mitochondria, the ETC occurs in the plasma membrane. - ATP Synthesis (Via ATP Synthase)
Eukaryotes: Inner Mitochondrial Membrane
Prokaryotes: Plasma Membrane
Explanation: ATP synthase is located in the inner mitochondrial membrane in eukaryotes, where it uses the proton gradient to produce ATP. In prokaryotes, it is found in the plasma membrane, where it functions similarly to produce ATP.
Distinguish between aerobic respiration and fermentation
Aerobic Respiration:
- Requires oxygen.
- Involves glycolysis, pyruvate processing, the Krebs cycle, and the electron transport chain (ETC).
- Produces much more ATP (around 32 ATP per glucose molecule).
- Occurs in the mitochondria in eukaryotes and the plasma membrane in prokaryotes.
Fermentation:
- Occurs without oxygen.
- Only involves glycolysis, followed by the conversion of pyruvate to lactic acid or ethanol (depending on the type of fermentation).
- Produces less ATP (only 2 ATP per glucose molecule).
- Occurs in the cytoplasm.
Distinguish between ethanol and lactic acid fermentation
Ethanol Fermentation:
-Occurs in yeasts and some bacteria.
-Pyruvate is converted into ethanol and carbon dioxide.
-Common in processes like alcoholic fermentation (e.g., brewing, baking).
Lactic Acid Fermentation:
-Occurs in muscle cells (during intense exercise) and certain bacteria.
-Pyruvate is converted into lactic acid (lactate).
-Does not produce carbon dioxide.
Are carbohydrates the only energy source used by heterotrophs?
no :)
