Cellular Respiration Flashcards
How do cells obtain energy?
By breaking down complex molecules and
harvesting the energy released by the reaction
What is Fermentation?
Partial breakdown of sugars and other organic fuels
without the use of oxygen to provide energy for a cell.
What is Aerobic respiration
A cell obtains energy via a thorough breakdown of organic fuels in which oxygen is consumed
What happens during Aerobic respiration?
Organic compound + O2 → CO2 + H2O + energy
- Organic compounds = carbo’s, fats and protein molecules … can all be used as fuel!
What is an oxidisation-reduction reaction?
-Transfer of electrons during chemical reactions releases energy stored in chemical molecules, which is used to synthesise ATP
- Transfer of electrons from one reactant to another is called oxidation-reduction reaction (= “redox reaction”)
» Gain of electron = “reduction” (remember: e-)
» Loss of electron = “oxidation”
- Oxygen is highly electronegative (loves electrons), so it strips electrons away from other compounds
Oxidation is when you…
lose electrons
Reduction is when you
gain electrons
What happens if energy is released too fast? How does Cellular respiration combat this?
It cannot be efficiently harvested so Cellular respiration breaks down glucose (and other organic fuels) in a series of small steps instead of a single explosive step
- NAD+ slowly harvests H (and e-) from glucose and passes it down the electron transport chain
What are the stages of Cellular Respiration?
Glycolysis ->Pyruvate Oxidation->Citric Acid Cycle-> Oxidative Phosphorylation
Draw the cellular respiration diagram
in workbook, answer is in the back.
What is substrate level phosphorylation?
Some ATP is made by direct transfer of a phosphate group from an organic substrate to ADP by an enzyme, where the substrate has a phosphate group in it and, via the enxyme, it is transfered to ADP to create ATP and a product.
What is Glycolysis?
- Sugar splitting
- Substrates: Glucose & 2 ATP
- Products:
» 2 pyruvate
» 4 ATP (so net = 2)
» 2 NADH + 2 H+
» 2 H2O
What are the first three products in the cellular respiration cycle?
Pyruvate → Acetyl CoA → Citric Acid Cycle
What is the Citric Acid Cycle and how does it work?
If oxygen is present, pyruvate enters mitochondria, is converted to Acetyl CoA, which then fuels the CAC - Substrates » Pyruvate (Acetyl CoA) - Products » 3 CO2 » 4 NADH + 4 H+ and 1 FADH2 » 1 ATP
How many ATP’s are produced from substrate level phosphorylation?
4 ATPs, produced by substrate-level phosphorylation
» Glycolysis: 2 ATP
» Citric Acid Cycle: 2 ATP
ATP production from substrate level phosphorylation accounts 4% of the total energy, where does the rest come from?
Most of the energy recovered is in electron carriers (NADH and FADH2)
What is the Electron Transport chain?
ETC is series of molecules (mostly proteins) embedded in inner membrane of mitochondria
» Step-wise harvest of G from “falling” electron
» Doesn’t produce ATP, but uses the energy to push
H+ from the mitochondrial matrix to the intermembrane space
What is ATP synthase?
An enzyme that created ATP from the proteins that are tying to enter the mitochondria. It allos them in and takes a phosphate group from the protein to creat ATP.
What is Chemiosmosis?
ETC produces a H+ gradient across the mitochondrial membrane, which provides the energy to power the enzyme ATP synthase
During respiration, energy flows from…
» Glucose → NADH → ETC → proton gradient → ATP
How much ATP is made for each section of respiration and how much is made in total? What happens to the rest?
Glycolysis + Citric Acid Cycle: 4 ATP
» ETC & chemiosmosis: 26-28 ATP
» Total = 30-32 ATP (ie, ΔG = 219-234 kcal)
» So cellular respiration recovers ≈34% of the total energy in glucose
• Compare with 25% for internal combustion engine!
• The rest is lost as heat
Draw the final electron yield diagram
In back of workbook
What is the final electron acceptor of the ETC and what happens if there is none?
The final electron acceptor of the ETC is O2 … if there’s no O2, the ETC (and ATP production) stops!
Certain cells can still generate energy without O2, how?
via anaerobic respiration or fermentation
