Unit 5 - Respiration Flashcards
Respiration
Process by which energy stored in complex organic molecules is released and immediately transferred to ATP
Energy is released through hydrolysis (making new bonds)
Why do animals need energy
Active transport Endo/exocytosis Synthesis of protein DNA replication Cell division Movement Activation of a chemical (phosphorylation)
Catabolic
Releasing energy
Anabolic
Energy consuming
ATP
Intermediary between catabolic and anabolic reactions
Relatively stable, only broken down by hydrolysis by enzyme catalysis (energy released can be controlled)
Easily moved around a cell when in solution
Hydrolysis of ATP
Catalysed by ATPase
ATP is hydrolysed to produce ADP then again to produce AMP
ATP –> ADP (-30.5), ADP –> AMP (-30.5), AMP —> A (-13.8)
Structure of ATP
Ribose attached to adenine (phosphodiester bond)
3 inorganic phosphate groups
Phosphorylated nucleotide
Processes in aerobic respiration
Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation
Glycolysis
Occurs in cytoplasm
Phosphorylation —> hexose biphosphate (2 phosphate groups from 2 ATP)
Hexose biphosphate splits into two
Oxidation (removal of H atoms) - accepted by NAD to make NADH
Breaks down glucose into pyruvate (3C), 2 NADH and 2 ATP
Where does glycolysis occurs
Cytoplasm
Why are ATP used in the first stage of glycolysis
Provide activation energy
Where does oxidative phosphorylation occur
Cristae
Role of ATP in the cell
Universal currency of energy
Phosphates can be removed by hydrolysis to release 30 kJ/mol energy
Energy used in metabolic reactions
Energy released in small quantities to prevent cell damage
Where does the Kreb’s cycle occur
Matrix of mitochondria
Coenzymes in leaf
NAD and FAD can be reduced to NADH and FADH2 and act as hydrogen carriers
NADPH reduces molecules by adding e-
ATP phosphorylates
Coenzyme A carries acetate to Kreb’s cycle
Link reaction
Pyruvate is decarboxylated to acetate (+ CO2)
Combines w/ CoA to make acetyl coenzyme A
Happens twice for glycolysis
Produces 2 NADH
Kreb’s cycle
CoA is recycled back to link reaction
Acetate combines with oxaloacetate to make citrate
Decarboxylated 2x to give orig. 4C compound, oxaloacetate
Produces 6 NADH, 2 FADH2 , 2 ATP and 4 CO2 (substrate level phosphorylation)
Which cofactor is part of the ETC
Fe^2+
What’s found in the matrix
Enzymes NAD FAD Oxaloacetate Mitochondrial DNA Mitochondrial ribosomes
Mitochondrial DNA
Codes for mitochondrial enzymes and other proteins
Mitochondrial ribosomes
Where proteins are assembled
Where can fatty acids be used in respiration
Fatty acids can produce acetate and enter the Kreb’s cycle directly
Where can glycerol be used in respiration
Can be converted to pyruvate and enter the link reaction
Where does the link reaction occur
Matrix of mitochondrion
Theoretical yield of ATP from 10 NADH
25
Total theoretical yield of ATP per pyruvate
25 - NADH
2 - FADH2
1 - Krebs cycle
2 - glycolysis
=30
Why is the yield of ATP not 100%
ATP has to be used for active transport of pyruvate and NADH
RQ
Vol. of CO2/ Vol. of O2 per unit time
RQ value for glucose
1
RQ value for amino acids
0.8/0.9
RQ value for triglycerides
0.7
Investigating respiration rates of yeast
Put a known vol. and conc. of a substrate sol. into a tt
Add a known vol. of buffer soln. - keep pH constant
Place tt in water bath (25 degrees)
Add known mass of dry yeast
After yeast has dissolved, place a bung on the tt which is attached to a gas syringe (should be set to 0)
Start the stopwatch
Record vol. of CO2 produced at regular intervals and calculate rate
Using a respirometer to measure O2 consumption
Set up respirometer - one w/ glass beads and the other w/ woodlice of same vol.
Add KOH to both - absorbs CO2 produced
Use syringe to set fluid in manometer to known level
Measure distance travelled by liquid in manometer - gives you vol. of O2 used up (pi r^2 h - need diameter of capillary tube)
Why does the liquid move in the manometer
As the organisms use up the O2, the pressure decreases causing coloured liquid in manometer to move.
Limitation of using respirometer
Difficult to accurately read the meniscus of the fluid in the manometer
Substrate level phosphorylation
ATP is formed by the direct transfer of Pi to ADP
Only occurs in Glycolysis and Kreb’s cycle
Substrate level phosphorylation in glycolysis
2 ATP per each glucose, when Trios-biphosphate is converted to pyruvate
4 - 2 = 2
Substrate level phsophorylation in Kreb’s cycle
1 per each turn
Occurs when 5C compound is converted to oxaloacetate
NAD vs FAD
NAD used in all stages but FAD only in Kreb’s
NAD accepts 1 H, FAD accepts 2 H’s
NADH is oxidised at the start of the etc releasing e- and H+ while FADH2 is oxidised further along the chain
NADH synthesises 3 ATP but FADH2 synthesises 2 ATP
Oxidative phosphorylation
FADH2 and NADH deliver H to etc in cristae
H dissociates into H+ and e- (used in synthesis of ATP through chemiosmosis)
Energy is released as e- travel down etc, creates a proton gradient
At end of etc, e- combines w/ H+ and O2 –> water
Etc cannot operate w/out oxygen
Obligate anaerobes
Cannot survive on the presence of oxygen at all
Facultative anaerobes
Synthesie ATP by aerobic respiration if oxygen is present but can switch to anerobic e.g. yeast
Obligate aerobes
Can only synthesise ATP in the presence of oxygen e.g. mammals
Fermentation
Produces ATP through substrate level phosphorylation only, no involvement of electron transport chain
Alcoholic fermentation
Occurs in yeast and some root cells
Glycolysis occurs and pyruvate is decarboxylated to ethanal
Ethanal accepts H+ from NADH to produce ethanol and NAD (recycled)
Produces ethanol and CO2
Lactate fermentation
Carried out in animal cells and produces lactate
Glycolysis occurs as normal
Lactate dehydrogenase causes pyruvate to accept H from NADH and is converted to lactate and NAD (recycled)
Allows glycolysis to keep occurring
Where is lactic acid converted back to glucose
Liver but requires oxygen –> oxygen debt after exercise
Why can lactate fermentation not occur indefinitely
Reduced ATP isn’t enough to sustain vital processes
Accumulation of lactic acid leads to fall in pH, proteins denature (respiratory enzymes)
