5.2.2 Respiration Flashcards
Equation for respiration
C6H12O6 + 6O2 -> 6H2O + 6CO2
Why is respiration needed
ATP needed for:
- active transport
- anabolic reactions (e.g. building of polymers)
- movement
Respiration provides this ATP
Where does glycolysis occur
In the cytoplasm
Conditions for glycolysis
Anaerobic
First step of glycolysis
Two phosphate groups, provided by ATP, are attached to a glucose molecule
Hexose bisphosphate formed
Second step of glycolysis
Hexose bisphosphate is split into two triose phosphate molecules
Third step of glycolysis
Free inorganic phosphate ions in cytoplasm attach to triose phosphate, two triose bisphosphate molecule formed
Fourth step of glycolysis
Triose bisphosphate molecules are oxidised by dehydrogenation
Two pyruvate molecules formed
NAD accepts the hydrogens, reduced NAD formed
Four ATP molecules are produced using phosphates from triose bisphosphate (substrate level phosphorylation)
Products of glycolysis
2 ATP molecules
2 pyruvate molecules
2 reduced NAD molecules
Structure of the mitochondria
- outer mitochondrial membrane: seperates contents
- inner mitochondrial membrane: contains ETCs and ATP synthase
- matrix: enzymes for krebs cycle and link reaction, mitochondrial DNA
- cristae: increase surface area for oxidative phosphorylation
- intermembrane space: proteins pumped into this space by ETC
Where does the link reaction take place
In the matrix
Describe the link reaction
- pyruvate enters matrix by active transport
- undergoes oxidative decarboxylation: CO2 and hydrogen is removed
- hydrogen is accepted by NAD which forms reduced NAD (NADH)
- acetyl group is formed which combines with coenzyme A to from acetyl CoA
Where does the Krebs cycle take place
Matrix
First step of the Krebs cycle
- Acetyl CoA delivers acetyl group
- acetyl combines with 4 carbon oxaloacetate to from 6 carbon citrate
Second step of the Krebs cycle
Citrate molecule undergoes decarboxylation and dehydrogenation, one reduced NAD and one CO2 produced, 5 carbon compound formed
Third step of the Krebs cycle
5 carbon compound undergoes further decarboxylation and dehydrogenation, regenerating oxaloacetate
CO2 produced, 2 reduced NAD produced, ATP produced, reduced FAD (FADH2) produced
Why are coenzymes important in respiration
Required to transfer protons, electrons, functional groups
Needed for redox reactions, need to accept protons and electrons that are released
Where does oxidative phosphorylation take place
In cristae
Describe oxidative phosphorylation
- hydrogen atoms from NAD and FAD delivered to electron transport chains
- dissociate into electrons and protons, electrons used in synthesis of ATP by chemiosmosis
- energy released by electrons down ETCs is used to create proton gradient, diffusion of protons through ATP synthase
- end of ETC, electrons combine with protons and oxygen to form water, oxygen is final electron acceptor
- phosphorylation of ADP requires electrons moving, which requires oxygen
What is chemiosmosis
Diffusion of protons from high to low concentration through partially permeable membrane
- movement releases energy
- energy used to attach inorganic phosphate to ADP to form ATP
- depends on proton gradient, energy from high-energy electrons down ETC pumps protons
- proton gradient maintained by impermeability of membrane to protons
- protons can only move through channels linked to ATP synthase, movement provides energy to synthesise ATP
What organisms use alcoholic fermentation
Yeast and some plant root cells
Equation for alcoholic fermentation
Glucose -> ethanol + carbon dioxide
Equation for lactate fermentation
Glucose -> lactate
What organisms use lactate fermentation
Mammals
