Biology- Respiration vs Photosynthesis


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Respiration - Aerobic

Respiration is the chemical process in which organic molecules are broken down to obtain ATP energy.

Few things to remember:

Glycolysis- (6C) Glucose is Phosphorylated by the addition of two ATP molecules. You get Two (3C) Triosephosphate molecules. Two H+ ions and two phosphates are released. 2 NAD are reduced and 2 ATP are produced. End products are two (3C) Pyruvate. Occurs in Cell Cytoplasm

Link reaction- Removal of CO2 and H+ and addition of CoA = AcetyleCoA molecule. Occurs in matrix of the mitochondria. Get reduced NAD.

Krebs cycle- Occurs in matrix of itochoondria. Acetyle CoA reacts with (4C) oxaloacetate to form (6C) citric acid. Unstable compond therefore releases 2 CO2 molecules,1 ATP molecule is made, get 3 reduced NAD, 1 FAD.

in total= (5 NAD, 1 FAD, 3 CO2, 1 ATP.) X by two since two pyruvate formed in glycolysis.

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Respiration - aerobic

Electron transport chain/Oxidative phosphorylation- all the hydrogen from the reduced NAD's enter a chain of reaction which ultimately yields energy in the form of ATP. Each H+ from NADH yields 3 ATP molecules and 2 ATP for each H+ from FADH molecule.

  • The H atom splits releasing e- which is then passed from one carrier to the next. This releases energy for the carrier to pump the H+ into the space of the mitochondrial membrane.
  • This increases the concentration of H+ therefore forming a concentration gradient
  • This electrical potential energy means that the H+ can flow back through the protein channels into the matrix
  • On these channels are ATPsynthase enzymes which use this energy to make ATP molecules.
  • Oxygen acts as a terminal electron acceptor as it accepts H+ e- forming H2O

In total- (10 X 3= 30) + (2 X 2= 4) + (4 ATP made directly)

all together 38 ATP molecules obtained and 34 are made in OXIDATIVE PHOSPHORYLATION

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When there is no oxygen available the end product of glycolysis reacts with hydrogen to form lactic acid. This has to be done since the NAD has to be regeneated to keep the cycyle going. Also it occurs in the cytoplasm instead of the mitochondria.

In plants the pyruvate loses CO2 to form ethanal (aldehyde) and accepts a hydrogen to from ethanol.

Both yield only 2 ATP molecules which is very poor comapred to aerobic respiration.

Also when these end products build, can become toxic and in plants this product cant be broken down therefore a high level of ethanol can be fatal.

However lactic acid can be broken down by the addition of O2 and converts it into CO2 and water.

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In photosynthesis light energy is converted into chemical energy.

LDR: Photophosphorylation- ATP is produce by using light

  • This occurs in the thylakoid membranes of the chloroplasts.
  • The chorophyll absorbs the light energy exciting the electrons to a higher energy level.
  • As these electrons pass from one carrier to the next, the energy produced is used to phosphorylates ADP + Pi into ATP.
  • water is split to replace the lost electrons in the chlorophyl. This also produces O2 as a waste gas and H+.
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LIR- Calvin cycle

  • These reactions can occur in the light or the dark
  • They take place in the stroma of the chloroplasts
  • CO2 is accepted by the molecule Ribulose bisphosphate(5C)
  • This forms a (6C) unstable molecule which breaks into two (3C) Triose phosphate by using 2 ATP and releasing 2 H+ reducing NADP.
  • Two TP molecules needed to make one Glucose molecule.
  • 1/6 of the TP is turned or used for glucose, 5/6 is used to regenerate RuBP
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