Chapter 12: Chapter 12: Respiration Respiration Leaving Certificate Leaving Certificate Biology Biology Higher Level Higher Level
Jan 03, 2016
Chapter 12: RespirationChapter 12: Respiration
Leaving Certificate BiologyLeaving Certificate Biology
Higher LevelHigher Level
RespirationRespiration• Internal versus external:
– Internal respiration is the enzyme-controlled release of energy from food
– External respiration is the exchange of gases with environment
• Aerobic versus anaerobic:– Aerobic respiration is the enzyme-controlled
release of energy from food using oxygen– Anaerobic respiration is the enzyme-controlled
release of energy from food without the use of oxygen
Aerobic RespirationAerobic Respiration
• Two stage process:1. Glycolysis
2. Krebs cycle & Electron Transport Chain
Stage 1: GlycolysisStage 1: Glycolysis• Oxygen-independent (can occur in presence
or absence of oxygen)• Occurs in cytosol• Glucose (a 6-carbon molecule) is changed into
two 3-carbon molecules (pyruvate)– This breaking down of glucose releases high energy
electrons – they are mopped up by NAD+ to become NADH
– NADH is an energy carrier but cannot release its energy to power metabolic reactions and so it needs to pass it on to ATP
– NADH powers the production of 3 ATP molecules– Glycolysis produces 2 molecules of ATP directlydirectly
Stage 1: GlycolysisStage 1: Glycolysis
GLUCOSEGLUCOSE
2ATP2ATP 2NADH2NADH
2ADP + 2P2ADP + 2P 2NAD2NAD++
2 PYRUVATE2 PYRUVATE
HH22OO Electron Transport
ChainMetabolism
Stage 2: Krebs CycleStage 2: Krebs Cycle• Oxygen-dependent (can only occur in the presence of O2)
• Occurs in the lumen of the mitochondrion (matrix)• Pyruvate enters mitochondrion and converted to 2-C
molecule (acetyl-coA) with release of NADH and CO2
• The acetyl-coA then joins with 4-C molecule from the previous Krebs cycle to form 6-C molecule
• The 6-C molecule is then broken down into 5-C molecule with release of CO2 and NADH
• The 5-C molecule is then broken down into 4-C molecule with release of ATP, CO2, 2NADH and 1FADH2
– The ATP goes to power metabolism
– The NADH and the FADH2 energy carriers go to the electron transport chain to pass their energy onto ATP molecules
– The 4-C molecule goes into the next Krebs cycle
Stage 2: Krebs CycleStage 2: Krebs CyclePYRUVATEPYRUVATE PYRUVATEPYRUVATE
Acetyl-CoA (2C)Acetyl-CoA (2C) Acetyl-CoA (2C)Acetyl-CoA (2C)
4C
2C +4C
6C
5C
4C
2C + 4C
6C
5C
CoA CoA
CO2
NADHCO2
2NADH
ATP CO2
NADHCO2
2NADH
ATP
CO2 NADH CO2 NADH
Metabolism Metabolism
Stage 2: Electron Transport ChainStage 2: Electron Transport Chain
• NADH molecules from glycolysis and Krebs cycle travel to the inner membrane (cristae) of mitochondrion
• The high-energy electrons release their energy slowly to power the production of ATP
• 3 ATP molecules are produced from each NADH
Stage 2: Electron Transport ChainStage 2: Electron Transport Chain
NADHNADH
NADNAD++
3ADP + 3P3ADP + 3P
3ATP
Inner mitochondrial membrane
Aerobic respiration Aerobic respiration produces a total of 38 produces a total of 38
ATP moleculesATP molecules
HH++ , 2e , 2e––
OO22 HH22OO
Metabolism
Anaerobic RespirationAnaerobic Respiration
• Anaerobic respiration occurs when no oxygen or limited oxygen is present
• Two stages:– Glycolysis– Lactic acid fermentation/Alcohol fermentation
Animals Animals and some and some bacteriabacteria
Plants, fungi, Plants, fungi, and some and some bacteriabacteria
Anaerobic RespirationAnaerobic RespirationGLUCOSEGLUCOSE
2ATP2ATP 2NADH2NADH
2ADP + 2P2ADP + 2P 2NAD2NAD++ + 4e + 4e-- + 2H + 2H++
2 x PYRUVATE2 x PYRUVATE
HH22OOElectron
Transport Chain
Metabolism
2 x Lactate2 x Lactate 2 x Ethanol2 x Ethanol
2CO2CO22NADH
NAD+
NADH
NAD+
Mandatory Experiment: To produce and test for alcohol
• Set up the apparatus as shown• Leave for a number of days, or
until the carbon dioxide is no longer produced
• Test for alcohol by filtering and taking 3 ml of filtrate; then adding 3 ml potassium iodide solution followed by 5 ml sodium hypochlorite solution
• Heat gently and the production of pale yellow crystals indicates the presence of alcohol