Cellular Metabolism Flashcards
Function of coenzyme Q10
Found in inner mitochondrial Membrane and helps make ATP. Also counters harmful effects of free radicals
Cycle Names of Aerobic Cellular Metabolism: 4 steps
- Glycolysis
- Pyruvate Decarboxylation
- Krebs cycle
- Electron Transport Chain
Autotrophs
Organisms that are capable of using the sun’s energy to create organic molecules (glucose) that can store energy in their bonds. Example: plant
Photosynthesis
anabolic process by plants
Heterotrophs
Organisms that derive their energy by breaking down organic molecules made by plants and harness the power that is held in the bonds of these molecules. Example: humans (catabolic process)
Glucose formula
C6H12O6
Formation of Glucose by autotrophs (Endothermic Process)
Breaking of C-O bonds in CO2 and O-H bonds in H2O. Atoms are rearranged into glucose and energy is stored in chemical bonds
Photosynthesis Formula
6 CO2 + 6 H2O + ENERGY –> C6H12O6 + 6 O2
Cellular Respiration Formula
C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + ENERGY
3 Energy Carriers
- ATP
- NAD+
- FAD
These molecules act as high-energy electron shuttles between cytoplasm and mitochondria.
Adenosine triphosphate (ATP) Function
Primary energy currency of cell. Rapid formation and degradation allow for energy to be stored and released as needed.
ATP Structure
- Nitrogenous base adenine
- sugar ribose (2’ has OH)
- three phosphate groups (Energy stored here)
NAD+ & FAD functions
- coenzymes capable of accepting high-energy electrons during glucose oxidation.
- electrons come in the form of hydride ions.
- They pass thru the electron transport chains and allow ATP to be generated from their stored energy.
- They are first Reduced during glycolysis and Kreb’s cycle (NADH and FADH2) (gain electrons
- They are then Oxidized during Electron transport chain (Back to NAD+ and FAD)
Energy in ATP is liberated through 2 processes
- Glycolysis
2. Cellular Respiration
Glycolysis- definition
Series of reactions that break glucose into 2 smaller organic molecules
Location of Glycolysis
Cytoplasm.
Occurs WITH or WITHOUT oxygen
Inputs of glycolysis (reactants)
- Glucose
- 2 ATP
- 2 NAD+
Outputs of glycolysis (product)
- Two Pyruvates
- 4 ATP
- 2 NADH
Net Reaction for glycolysis
Glucose + 2 ADP + 2 Pi + 2NAD+ –> 2 Pyruvate + 2ATP + 2 NADH + 2 H+ + 2H2O
Total ATP production
Glycolysis makes 4 ATP molecules, but the process uses 2 ATP molecules so the net production is 2 ATP molecules.
Substrate-level Phosphorylation
The direct generation of ATP from ADP and Pi
Fate of pyruvate based on character of cell environment:
- Aerobic Organisms ( Use of O2)- undergoes further oxidation
- Anaerobic Organisms (Oxygen free)- undergoes process of fermentation.
Obligate/facultative aerobes/ anaerobes
Obligates- require that designated environment
Facultative- prefer an environment over the other but can survive in either.
Fermentation
- oxygen free process.
- Reduces pyruvate to either ethanol or lactic acid.
- Oxidizes NADH to NAD+
- Term “fermentation” included glycolysis plus reduction of pyruvate.
Alcohol Fermentation
- Occurs in yeast and some bacteria
- FIRST-Pyruvate (3C) is decarboxylated to acetaldehyde (2C).
- SECOND- Acetaldehyde (2C) is reduced by NADH to ethanol (2C). Generating NAD+
Lactic Acid Fermintation
- Occurs in some fungi and bacteria, and humans in times of O2 scarcity
- Pyruvate (3C) is reduced to lactic acid (3C)
- NADH is oxidized into NAD+
- Lactic Acid decreases the local pH.
Cori Cycle
- Conversion of Lactic acid back to pyruvate in order for cellular respiration to continue
- Oxygen debt: amount of oxygen needed to do this.
3 Key phases of Cellular Respiration
- Pyruvate decarboxylation
- Citric Acid cycle ( Kreb’s cycle)
- Electron Transport Chain
Pyruvate Decarboxylation
- Step doesn’t need O2 but it only occurs when cell commits to aerobic respiration.
- Pyruvate is transported from cytoplasm into mitochondrial matrix.
- Each Pyruvate loses a CO2
- Remaining acetyl (2 C) binds to coenzyme A . FORMING acetyl-CoA
- For each pyruvate an NAD+ is reduced to NADH
Results of pyruvate decarboxylation
2 acetyl-coA (2 C)
2 CO2
2 NADH
Citric Acid Cycle
- First acetyl-CoA (2 C) combines with oxaloacetate (4 C) forming Citrate (6 C).
- Each cycle releases 2 CO2
- Doesn’t directly generate much energy, only 1 ATP per cycle.
- But can generate high-energy electrons, 3 NADH and 1 FADH2 per cycle
Total Product of Krebs Cycle
- 6 NADH
- 2 FADH2
- 2 ATP (from GTP)
Electron Transport Chain
- Here we use oxidative phosphorylation to use the energy from the reduced NADH and FADH2
Oxidative Phosphorylation
- process by which electrons from NADH and FADH2 are passed along an assembly line of carriers that release free energy with each transfer.
- That free energy is put into ATP production.
- Carriers are enzymes known as cytochromes
Cytochromes
- enzymes used as carriers of electron in electron transport chain.
- each contain a central iron atom that undergo reversible redox reactions as electrons bind and release.
- Because iron can be present in more than one oxidation state, it’s a likely candidate to participate in redox reactions.
3 Complexes of Cytochromes
- NADH dehydrogenase (complex I)
- b-c1 complex (Complex III)
- Cytochrome oxidase (complex IV)
Process of Electron Transfer
- First: NADH gives electron directly to Flavin mononucleotide (FMN- part of complex I).
- Electrons are then passed to carrier Q (ubiquinone- a hydrophobic molecule, NOT an enzyme)
- Carrier Q passes electrons to complex III, which are then donated to complex IV.
- Oxygen then takes the electrons from complex IV-protein cytochrome a3 along with 2 protons and makes water.
- NOTE- if oxygen is in debt, electrons cannot be picked up from cytochrome a3.
Amount of ATP produced from each NADH
3 ATP molecules from each NADH.
EXCEPT 2 ATP molecules from NADH produced in cytoplasm.
Amount of ATP produced from each FADH2
2 ATP molecules are generated, because electrons are given to complex II, Succinate-Q-oxidoreductase, So electrons travel a shorter distance to get to oxygen and so less energy is extracted from them.
Cyanide
Poison that blocks the final transfer of electrons to O2.
Dinitrophenol (DNP)
Poison that destroys the mitochondriaon’s ability to generate a useful proton gradient that is necessary for effective ATP generation.
Proton Gradient
-necessary in inner mitochondrial membrance and links the oxidation of NADH and FADH2 to ADP phosphorylation.
Proton-Motive Force
- Created by the carriers giving up electrons causing free protons to pass and accumulate into the mitochondrial matrix.
- ETC then pumps these ions out of the matrix and into the intermediate space at each protein complex.
- This causes the intermembrane to be positive and acidic.
- so electrochemical gradient drives H+ passively back across the inner membrane into the mitchondrial matrix.
ATP synthases
Enzyme complexes are used for H+ ions to pass back into the matrix and the energy released allows for phosphorylation of ADP back to ATP.
ATP production per Glucose Molecule
Glycolysis:(8 ATP) -2 ATP Used -4 ATP made (substrate) -2 NADH--> 4 ATP (oxidative) Pyruvate decarboxylation - 2NADH--> 6 ATP (oxidative) Cirtric Acid Cycle -6 NADH --> 18 ATP (oxidative) -2 FADH2--> 4 ATP (oxidative) - 2 GTP --> 2 ATP (substrate)
Total of 36 ATP
Alternate Energy Sources (3)
Carbohydrates
Fats
Protein
Carbohydrates
Sugar polymers are broken down during digestion and stored in the liver for later use in a form known as glycogen.
Fats
- Stored in adipose tissue as triglycerides.
- for long term storage, the fatty acids are esterified and it become glycerol.
- Glycerol can be converted to PGAL (intermediate in glycolysis) but real energy of fats is stored in the fatty acids.
Proteins
Used only when carbohydrates are insufficient.
Amine moiety is removed resulting in an acid that can be converted into acetyl-CoA or intermediates of TCA cycle.
Beta-oxidation
Fatty acid is first activated in cytoplasm in a process requiring 2 ATP, then transported to mitochondria matrix and undergoes rounds of generating acetyl-coA.(total of 24 rounds) generated 24 NADH and 24 FADH2, close to a 100 ATP production
Transaminases
Removes the amine moiety from amino acids resulting in molecules known as alpha-keto acids, that are able to convert into acetyl-CoA
