L13. Obtaining Energy from Food Flashcards
direct burning in a nonliving system vs stepwise oxidation - direct burning
- large activation energy is overcome by the heat from a fire
- all the free energy is released as heat (none is stored)
direct burning in a nonliving system vs stepwise oxidation - stepwise oxidation
- also cellular respiration
- small activation energies are overcome by enzymes that work at body temperature
- some of the free energy is stored in activated carrier molecules
how are the activated carriers ATP and NADH are used
- the energy from food breakdown (oxidation and favorable) is transferred to ATP and NADH
- the energy from ATP is then coupled with ATP synthesis
- energy from other carriers drive oxidative phosphorylation
what is oxidative phophorylation
- takes place in inner mitochondrial membrane
- it is when the cell uses energy from activated carriers to drive ATP production
what are the three stages to breaking down food molecules
- mouth, gut, and lysozymes
- cytosol
- mitochondria
three stages to breaking down food molecules - mouth, gut, and lysozymes
large macromolecules are digested and converted into simple monomers via enzymes
three stages to breaking down food molecules - cytosol
- glucose enters via glucose/Na+ symporter
- gradual oxidation breakdown of simple monomers via glycolysis
- glycolysis takes 1 glucose and converts it into 2 pyruvates
- also produces ATP and NADH
three stages to breaking down food molecules - mitochondria
- pyruvate enters the mitochondria matrix and is converted into Acetyl CoA
- acetyl CoA then goes into the citric acid cycle and this makes a large amount of NADH
- electrons from NADH is passed to the electron transport chain
- this causes oxidative phosphorylation to begin, producing a large amount of ATP
explain the location of the reactions for aerobic respiration
- glycolysis: cytosol
- citric acid cycle and oxidative phosphorylation: mitochondria
three stages to breaking down food molecules: cytosol - explain ATP and NADH in glycolysis
- 2 ATP is required and produces 4 ATP with a net ATP of 2
- also produces 2 NADH
three stages to breaking down food molecules: cytosol - glycolysis in absence of O2
products are ethanol or lactic acid fermentation
three stages to breaking down food molecules: cytosol - glycolysis in presence of O2
pyruvate goes to mitochondria
three stages to breaking down food molecules: cytosol - how does glycolysis initiate the breakdown of sugars
- the breakdown of glucose provides energy for ATP synthesis from ADP and Pi
- during ATP synthesis, substrate-level phosphorylation occurs
- NADH electron is then donated to the electron transport chain (for aerobic organisms)
three stages to breaking down food molecules: cytosol - substrate level phosphorylation
Pi is transferred from substrate molecules (sugar intermediates) to ADP
three stages to breaking down food molecules: cytosol - explain NAD+
- an intermediate in catabolic reactions that generate ATP through the oxidation of food molecules
- it is an oxidizing agent (takes e-)
- kept high in the cell
three stages to breaking down food molecules: cytosol - NADPH
- operates with enzymes that catalyze anabolic pathways
- it is a reducing agent (gives e-)
- kept low in the cell
three stages to breaking down food molecules: cytosol - anaerobic metabolism
- anaerobic organisms use glycolysis
- pyruvate and NADH remain in the cytosol
- after glycolysis, fermentation begins
- NADH will give up an electron to be turned into NAD+
three stages to breaking down food molecules: cytosol - define fermentation
energy-yielding pathways that break down sugar in absence of O2
three stages to breaking down food molecules: anaerobic metabolism - what does pyruvate convert to after fermentation
- muscle cells: lactate
- yeast: ethanol and CO2
three stages to breaking down food molecules: cytosol - explain how reactions are coupled for glycolysis
- during step 6: an energetically favorable C-H bond is oxidized and it drives the unfavorable NADH synthesis and the formation of a high-energy phosphate bond
- during step 7: an energetically favorable hydrolysis of the phosphate bond drives ATP synthesis
three stages to breaking down food molecules: cytosol - explain the ΔG° for ATP formation to be coupled
since the transfer of Pi is favorable, the ΔG° for hydrolysis of the phosphate bond must be more negative for the donor than the acceptor
three stages to breaking down food molecules: cytosol - what is gluconeogenesis
- it makes glucose from pyruvate (opposite of glycolysis)
- it is costly and anabolic
- uses many of the same enzymes as glycolysis but uses specific enzymes to bypass the three irreversible steps in glycolysis
three stages to breaking down food molecules: cytosol - example of an enzyme in gluconeogenesis
- phosphofructokinase
- it is allosterically regulated
- activated by ADP, AMP, and Pi
- and inhibited by ATP
three stages to breaking down food molecules: mitochondria - explain the pyruvate dehydrogenase complex
converts pyruvate to acetyl CoA and CO2
three stages to breaking down food molecules: mitochondria - explain how fatty acids are converted to acetyl CoA
- lipases cleave the bonds that link fatty acids to glycerol
- the fatty acids are then coupled to coenzyme A
- fatty acyl CoA is then oxidized in a four-enzyme cycle, generating one molecule of acetyl CoA and one each of NADH and FADH2
three stages to breaking down food molecules: mitochondria - explain the citric acid cycle
- it does not use O2 but it requires it for the turnover of NADH to NAD+ (keeps electron transport chain running)
- it completely oxidizes carbon atoms from acetyl CoA to CO2
three stages to breaking down food molecules: mitochondria - explain GTP and FADH
- produced from the citric acid cycle
- they are both activated carriers (donates electrons)
- they have high-energy electrons stored and it can be used to produce ATP via oxidative phosphorylation (the only step that directly requires O2)
three stages to breaking down food molecules: mitochondria - explain the process of oxidative phosphorylation
- NADH and FADH2 transfers electrons to the electron transport chain via electron carriers embedded in the inner mitochondrial matrix
- in the chain, the energy released will be used to drive H+ efflux across the inner membrane
- this creates a gradient and will be used to ATP synthesis (ADP phosphorylation)
- electrons are added to O2 and it will be combined with H+ to generate H2O
- creates more ATP than glycolysis
