Anaerobic Respiration (Fermentation)

1. Anaerobic respiration (fermentation):

    - respiration takes place in the absence of O2
    - occurs only in the cytoplasm.

    - produces: pyruvate, 2 NADH + 2 mol ATP 
    - pyruvate + NADH accumulate in cytoplasm

2. - pyruvate + NADH accumulate in cytoplasm
       --> causes tissues to run out of H acceptor (NAD+) - limited supply.

       --> glycolysis may not occur.

       --> need for an alternative H acceptor.

       --> pyruvate or acetaldehyde becomes the H acceptor.

       --> pyruvate can undergo both aerobic and anaerobic respiration.

3. In plants:

    - pyruvate undergoes alcohol fermentation --> produce ethanol,
    - occurs in roots of the plants (water logged conditions).

4. In animals:

    - pyruvate undergoes lactic acid fermentation --> produce lactic acid
    - occurs in the muscles during vigorous activity + strenuous exercise.

7. Fermentation products are used commercially.

    - Wine, methanol and formic acid are formed by alcohol fermentation.

    - Yogurt, cheese and soy sauce are formed by lactic acid fermentation.

Aerobic Respiration - Electron Transport System

1. Electron transport system = chain of e- acceptors (embedded in the inner membrane of the mitochondrion).

2.  e- transferred from NADH + FADH2 via several e- acceptors --> final e- acceptor (molecular O2).

3.  energy produced = ATP (thru oxidative phophorylation).

4.  inhibitors = cyanide + CO - inhibit the function of ETC.
5.  Cyanide + CO --> block activity of cytochrome oxidase --> inhibit the ETS --> no production of H2O --> no activation of ATP synthase --> no ATP production.

6.  ETS:

• accepts e- from energy carriers (NADH + FADH2) from glycolysis + Krebs cycle.
• consists of mostly cytochromes (proteins with prosthetic groups).
• produces H2O from O2 at the end
• 1 NADH produces 3 ATP
• 1 FADH2 produces 2 ATP.
• net energy gain = 34 ATP molecules.

 

Aerobic Respiration - Krebs cycle

1. Krebs cycle:

• biochemical reactions occurring in all living cells,
• in the inner membrane of mitochondria.
• involves a metabolic pathway (pyruvate --> CO2 + H2O) to generate energy.
• also called citric acid cycle or trycarboxilic acid (TCA) cycle.

2.  Acetyl CoA initiates the Krebs cycle (by combining with oxaloacetate (4C) --> citrate).

3.  Citrate is decarboxilated and dehydrogenated.

4.  Energy stored = NADH, FADH2 and GTP.

5.  2 mol of CO2 are released (as waste product).

6.  NAD + FAD = H acceptors.

7.  1 mol of  ATP is gained.

8.  provides H for use in ETC (as energy for formation of ATP).

Aerobic Respiration - Glycolysis

Aerobic respiration is a process:

1. which sugars are broken down - to release energy - in the presence of O2.
2. occurs in three stages: glycolysis, Krebs cycle, electron transport system.

Glycolysis:

1. takes place in cytoplasm of a living cell,
2. glucose --> 2 mol of pyruvate.
3. series of reactions catalysed by specific enzymes
4. involves two phases: energy investment phase and energy pay off phase.

5. Energy investment phase:

• glucose is broken down into 2 mol of PGAL
• 2 mol of ATP are utilized in this phase.

  

6.   Energy pay off phase:

• 2 mol of PGAL --> 2 mol of pyruvate.
• 4 ATP is formed by substrate level phosphorylation.
•  The net = 2 ATP + 2 NADH.

Experiment 14: Structure of flowers



Investigating...the flowers...and friends.

 

Must... must finish....must finish today!



Delonix regia in half.......







Hey!...Where's the ovary???

  

Concentrate....concentrate.........ohm..



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draw....draw.....draw....z z z z!



The orchid is cut into equal halves.







 

 



Alternative mechanism of C fixation occurs in C4 and CAM plants

C4 plants:

1. occurs both in mesophyll + bundle sheath cells.

2. CO₂ fixation is catalyzed by PEP carboxilase in mesophyll cells and sugar formation by RUBISCO in bundle sheath cells via Calvin cycle.

3. First product of CO₂ fixation is a 4C compound oxaloacetate in C4 plants.

CAM plant:

1. live in hot climatic conditions

2. both C₃ and C₄ cycles occur.

4. fix CO₂ during the night + synthesise sugar during the day.

5. G3P produced = used for the synthesis of sugars, amino acids and fatty acids.

6. Sugars formed = glucose, sucrose, starch + cellulose.

7. Lipids:

·  formed from glycerol + fatty acids.

·  Glycerol = formed directly from G3P

·  fatty acids = built from acetyl coenzyme A.

8. Protein formed by: conversion of G3P --> acetyl Co A (enters Krebs cycle) --> α-glutarate --> glutamate --> transamination --> form amino acids + proteins.

Dark Reaction (Light Independent Reaction)

1.   Dark reaction (Calvin cycle):

Þ    2^nd stage of photosynthesis

Þ    CO₂ - converted into sugar.

Þ    takes place in the stroma (of chloroplast + bundle sheath cells).

Þ    not dependent on light.

Þ    cyclic process of enzyme catalyzed reactions. 

2.   It involves three steps:

Þ    CO₂ fixation

Þ    reduction

Þ    regeneration.

3.   During CO₂ fixation:

Þ CO₂ combines with RuBP(5C) to form G3P (catalysed by Rubisco - also involved in the photorespiration process).

Þ  first product = glyceraldehyde 3 phosphate (G3P)

4.  ATP and NADPH are utilised (from light reaction).

5.  5 molecules of G3P are utilised for regeneration of RuBP.
4.  C₃, C₄ and CAM plants (have different anatomy + physiology)

5.  C₃ plants:

Þ    mesophyll cells have chlorophyll.

Þ    open their stomata during the night.

Þ    live in moderate climate.

6.  C₄ plants:

Þ    have mesophyll cells + bundle sheath cells.

Þ    have Krantz anatomy.

Þ    live in dry climatic conditions.

Þ    adapt themselves to prevent water loss by closing stomata during day time.