C1.2 respiration Flashcards
Difference btwn anaerobic and aerobic respiration + examples of each
Anaerobic:
- in absence of oxygen
- comparitively small release of ATP
- take place in CYTOPLASM
- mitochondria not required
- CO2 and lactic acid/ethanol as waste products
Consists of:
ALCOHOLIC fermentation
- C6H12O6 > 2C2H5OH + 2CO2
- incomplete breakdown of glucose
- 2 ethanol produced
LACTIC ACID fermentation
- Glucose > 2 pyruvic acid > 2 lactic acid
- releases 2 ATP from the breakdown of 1 glucose
Aerobic
- in the presence of oxygen
- release of large amounts of energy
- CO2 and H2O produced as byproducts
- mitochondria required
Properties of ATP that make it suitable energy currency within cells
Adenine Triphosphate is a nucleotide
- composed of a ribose sugar, adenine, and 3 phosphate groups
- there are high energy bonds btwn the 3 phosphate groups, although the bond btwn the last 2 phosphate are unstable, and when broken releases energy
Properties:
- soluble in water = can freely move through cytoplasm and other aqueous solutions in the cell
- stable at pH levels close to neutral (e.g. in cytoplasm)
- CANNOT pass freely through phosphlipid bilayer = its movement btwn membrane bound organelles can be controlled
- 3rd phosphate group easily removed and attached by hydrolysis and condensation reaction
- The hydrolysis of ATP to ADP produces sufficient energy for most cellular processes without excess energy being wasted as heat
Examples of life processes in the cell dependent on ATP
- Active transport across membranes,
- Movement of the whole cell
- Movement of components within the cell e.g. during mitosis and meiosis
Definition of cell respiration
The controlled release of ATP energy from organic compounds within cells.
- organic compounds are compounds that contain carbon, but not oxides or carbonates.
- glucose and fatty acids are the main organic compounds used, although other organic compounds can be used
Why can’t anaerobic respiration be used for long periods of time in humans?
- Although anaerobic respiration maximises the power of muscle contractions, lactic acid AND H+ ions are produced in this process.
- During long durations, H+ ion concentration would be too high, decreasing the pH of the blood, making the pH too low
Formula for calculating rate of respiration
Rate of reaction = (Change in rxnt or product)/time
e.g. decrease in oxygen or increase in CO2
4 stages of cellular respiration
GLKE
- glycolysis
- link reaction
- Krebs cycle (citric acid cycle)
- electron transport chain (oxidative phosphorylation)
Describe glycolysis in aerobic cell respiration
occurs in CYTOPLASM
1. Phosphorylation of glucose: 2 ATP molecules are hydrolysed. The 2 phosphates produce bind to glucose (6 carbon compound) forming an UNSTABLE 6-carbon compound. The energy level of the 6-carbon compound is raised, making it less stable and hence subsequent reactions are possible.
- Lysis: the 6-carbon compound breaks apart to form 2 3-carbon compounds (triose phophates)
- Reduction of NAD+: 2 molecules of NAD+ are converted to 2 molecules of NADH (the reduced form of NAD+), one for each 3-carbon compound. They take electrons and hydrogen from the 3-carbon compound. The 3-carbon compound is oxidised.
- Formation of ATP: as each 3-carbon compound is converted to pyruvate, 2 ATP are produced. The energy to convert ADP to ATP is from the energy released by the oxidation of the 3-carbon compound
End products: 2 pyruvate, 2 ATP, 2 NADH
Describe glycolysis in anaerobic cell respiration in animals and yeast.
The same 4 steps as normal glycolysis: phosphorylation, lysis, reduction of NAD+, formation of ATP.
occurs in CYTOPLASM
However, as glycolysis requires a constant supply of NAD+, if oxygen is not present then pyruvate is used to regenerate NAD+.
Animal:
- pyruvate is converted to lactic acid, oxidising NADH to NAD+ (NADH reduces pyruvate to lactate)This process is called anaerobic respiration, producing a net gain of 2 ATP, lactic acid, and regenerates NAD+
- NO RELEASE OF CO2, lactate as end product
Yeast:
- glycolysis of glucose produced 2 ATP, 2 pyruvate, and 2 NADH. Pyruvate is then converted to ETHANOL AND CO2, regenerating NAD+ and allowing glycolysis to continue
- ethanol and CO2 as end products
Describe the link reaction
Takes place in the mitochondrial matrix
- pyruvate moves from the cytoplasm to the matrix of the mitochondria
- Decarboxylation of pyruvate: Pyruvate loses CO2, to produce a 2-carbon ACETYL group. (2 CO2 produced, 1 for each molecule of pyruvate)
- Reduction of NAD+: Pyruvate is oxidised, losing electrons and hydrogen to NAD+ to create NADH
- Formation of Acetyl Coenzyme A: Coenzyme A attaches to the 2-carbon acetyl group to form Acetyl CoA.
End products: 2 CO2, 2 AcetylCoA
How do triglycerides contribute to the link reaction?
Triglycerides do not undergo glycolysis
- they are hydrolysed to form glycerol and fatty acids
- the fatty acids enter the mitochondrion and are converted to multiple acetyl coenzyme A molecules, which can be used in the Krebs cycle
Describe the Krebs cycle/citric acid cycle
Takes place in the mitochondrial matrix
- OXALOCETATE, a 4-carbon compound, combines with the acetyl group from AcetylCoA to form CITRATE, a 6-carbon compound.
- 2 decarboxylations of citrate, each decarboxylation forming 1 CO2. (4 CO2 in total)
- 4 oxidations of citrate (OR DEHYDROGENATION REACTIONS): citrate is converted back into oxalocetate through a series of intermediate enzyme-catalysed reactions. 3 intermediate products are oxidised, losing electrons and hydrogens to NAD+ to form NADH. 1 intermediate product is oxidised by FAD2+ to form FADH2.
- 2 ATP is produced in total, as each turn of the Krebs cycle provides enough energy to convert ADP and a phosphate to ATP through a condensation reaction
- SUBSTRATE LEVEL PHOSPHORLYATION
Essentially, citrate is converted back into oxalocetate through a series of decarboxylation and oxidation reactions.
Citrate > Oxalocetate
High energy > Low energy
End products: 2 ATP, 6 NADH, 2 FADH2, 4 CO2
Purpose of NAD+ and FAD2+
to oxidise Triose phosphate/pyruvate/citrate
- these oxidation reactions release energy, much of which is stored by NAD+ and FAD2+ when accepting H+ ions. These oxidation reactions are also known as DEHYDROGENTATION REACTIONS
- this energy is later used in the electron transport chain to produce ATP
- also used to convert pyruvate to lactic acid in anaerobic respiration
Describe the electron transport chain + oxidative phosphorylation
Reduced NAD from glycolysis, link reaction, and Krebs cycle, and FAD from Krebs cycle, carry electrons to the electron transport chain in the inner mitochondrial membrane.
NADH donates electrons to the first protein complex, FADH2 donates electrons to the second protein complex, regenerating NAD and FAD
The ETC breaks down the large-free energy drop from food to O2 to smaller steps that release energy in managable amounts.
- Electrons are passed along the ETC through a series of oxidtation-reduction reactions
- The multiprotein carriers alternate in reduced and oxidised states as they accept and donate electrons, causing electrons to drop in free energy as they go down ETC and is finally passed to oxygen (FINAL proton acceptor) to form H2O
- The movement of electrons provides the energy for the active transport of H+ from the mitochondrial matrix to intermembrane space to create a high conc. of H+ in the intermembrane space, establishing an electrical gradient across the membrane
- CHEMISOMOSIS: H+ then moves back across the membrane from a high conc. in intermembrane space to low conc. in matrix (facilitated diffusion), passing through ATP synthase (as H+ cannot freely pass through mitochondrial membranes). ATP synthase uses the exergonic flow of H+ ions to drive the phosphorylation of ADP to produce ATP.
- OXIDATIVE PHOSPHORYLATION
Role of oxygen in ETC
FINAL ELECTRON ACCEPTOR:
- oxygen accepts H+ ions to form H2O, maintaining the H+ gradient across the mitochondrial membrane
- If no oxygen is present, electron flow across ETC stops = no more NAD and FAD converted = no link reaction and Krebs cycle.
Hence oxygen greatly increases ATP yield/glucose of cell respiration
