Respiration Flashcards
Respiration Equation
Glucose + Oxygen -> Carbon Dioxide + Water + Energy
Why is glucose NOT used directly?
- glucose broken down in many steps. involving many specific enzymes
if glucose is broken down in one step: - too much heat energy released causing enzymes to denature
How is mitochondria adapted to its function?
- Small organelle= large SA/vol ratio
- Short diffusion path for O2
- many cristae increase SA for ETC/ ATP synthase
- aqueous matrix (soluble enzymes)
Explain advantage of many cristae
- larger SA for electron carrier system
- provides more ATP for muscle contraction
What are the 4 stages of aerobic respiration?
- glycolysis (cytoplasm)
- link reaction (matrix of mitochondria)
- krebs cycle (matrix of mitochondria)
- electron transport chain (inner mitochondrial membranes)
Two ways that ATP can be generated
- Substrate-level phosphorylation- ATP generated directly through energy released via respiration reactions. This occurs in Glycolysis and the Krebs cycle
- Oxidative phosphorylation – ATP generated from the chemical energy released when a reduced hydrogen carrier or coenzyme (NADH2 or FADH2) has been oxidised at the Electron Transfer Chain.
Glycolysis
- Glucose (6C) activated by phosphorylation requires hydrolysis of 2 ATP to 2ADP to provide 2 phosphates
- Glucose phosphate then splits into 2 x triose phosphate
- TP (3C) oxidised to pyruvate (3C) and involves loss of H (via dehydrogenase enzyme) reduces hydrogen carrier NAD to NADH2
- ATP produced via substrate level phosphorylation
Produces:
2 net ATP
2 NADH
2 pyruvate ( leave mitochondria by AT)
The Link reaction
- Pyruvate is oxidised to acetate
- Hydrogen removed to form reduced NAD
- CO2 is lost via decarboxylation
- NO ATP is produced
- Acetyl co A produced
The Krebs cycle
- 2C Acetyl co A combines with 4C molecule to form 6C compound
- 6C compound loses CO2 and Hydrogen to convert to a 4C compound and 1x ATP (via substrate-level phosphorylation)
- The cycle can now continue.
Describe how oxidation takes place in glycolysis/ krebs?
- removal of H+
- by enzymes
- H accepted by NAD
- in krebs cycle FAD used
The Electron Transport Chain (ETC)
1.The reduced H carriers are oxidised losing Hydrogen.
2. The electrons pass down a series of electron carriers in a series of REDOX reactions.
3. As the electrons pass along the electron transport chain they lose energy, some of which is used to pump the H+ through the inner mitochondrial membrane into intermembrane space
4. Some of the energy is also lost as heat.
5. The H+ pass diffuse, down a proton gradient, into the matrix via ATP synthase enzymes and enough energy is provided to form ATP.
6. The electrons and H+ recombine with Oxygen gas to form water.
7. Oxygen is the final/terminal electron acceptor.
8. Without oxygen removing H+ and electrons, there would be a ‘back up’ of electrons along the ETC and the process of cellular respiration will come to a halt
Water is a waste product of aerobic respiration. Describe how water is formed at the end of aerobic respiration.
- oxygen is terminal/final electron acceptor;
- combines with electrons and protons (to form water);
Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.
*reduced NAD
* electrons transferred from coenzyme to coenzyme
* energy released as electrons passed on
* energy used to synthesise ATP from ADP and Pi
* H+ / protons pumped into inter membrane space;
* H+ / protons diffuse back through ATP synthase enzyme;
Describe how ATP is made in mitochondria.
- Substrate level phosphorylation
- link reaction produces reduced NAD
- Electrons released from reduced NAD
- (Electrons) pass along carriers
- Energy released
- Protons pumped into inter membrane space;
- ADP/ADP + Pi
- ATP synthase;
Describe the events of oxidative phosphorylation
- NAD/FAD reduced
- ETC on cristae
- electrons transferred from coenzyme to coenzyme
- energy released as electrons passed on
- protons pumped into intermembrane space
- protons flow back through enzyme
- energy used to synthesise ATP from ADP and phosphate
Anaerobic respiration
The Link reaction, Krebs cycle and electron transport chain stop as there is no Oxygen to act as the Final / terminal electron acceptor.
Glycolysis does not require Oxygen and can continue in the absence of Oxygen, however, for glycolysis to continue NAD must be regenerated.
The H from the reduced NAD in glycolysis is now accepted by pyruvate rather than passing through the electron transport chain.
The pyruvate is reduced to lactate in animals and ethanol & CO2 in plants.
Respirometer expected results
Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion
- oxidation of H+
- from pyruvate
- ATP produced in Krebs cycle;
- production of reduced NAD / FAD
- in matrix of mitochondria
- electrons fed into electron transport chain
- phosphorylation on cristae
- linked to ATP production
- ATP synthase
Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath.
- Equilibrium reached;
- Allow for expansion/pressure change in apparatus;
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration.
- Regenerates NAD /
Oxidises reduced NAD; - (So) glycolysis continues;
Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell.
- Less reduced NAD
- Oxygen is the final electron acceptor;
In many mammals, ‘uncoupling proteins’ help to maintain a constant body temperature during hibernation.
Suggest and explain how.
- Allow passage of protons/H+;
- (Energy) released as heat
Explain why a log scale is used to record the number of cells/bacteria.
Large range/difference/increase in numbers (of cells/bacteria);
Accept reference to exponential (increase)
