Breathing process

1. Breathing control centre are:

• located in two major regions (medulla oblongata + pons).
• in medulla - sets the basic rhythm,
• in pons - moderates it smoothing out the transition between inhalation + exhalation.
• send impulses to the diaphragm + external intercostals muscle.

2. The central chemoreceptors (lies near the breathing control centers):

• detet the changes in pH of the cerebospinal fluid (CSF).
• stimulate the breathing centre
• slow down or speed the rhythmic discharge of nerve impulses

3. Carotid bodies are

• found in the carotid artery in the neck.
• chemoreceptor with nerve endings in the wall of carotid artery
• monitors the changes of blood pH in the carotid artery.

4. Aortic bodies are

• found in aorta.
• chemoreceptors that monitor the changes of blood pH.
• nerve endings in the wall of aorta.

5. Aortic and carotid bodies:

• also called peripheral chemoreceptors.
• impulses are relayed to the breathing control centres.
• change of CO2 conc. in the blood triggers a series of chain reactions.
• blood CO2 conc. back to normal,
• negative feedback loop.

6. In the blood plasma:

• CO2 released by cellular respiration 
• reacts with H2O to form carbonic acid (H2CO2)
• dissociates to form hydrogen carbonate ions (HCO3+) and hydrogen ions (H+).
• increase in hydrogen ions (H+) conc.
• increase the acidity of the blood plasma,
• decreasing the pH.

7. In the region of medulla

• CO2 diffuses into CSF from the surrounding capillary.
• then reacts with H2O in the fluid to form carbonic acid (H2CO3).
• dissociates to form hydrogen carbonate (HCO3+) and hydrogen ions (H+).
• The acidity in the CSF increases
• resulting in the decreases in the pH.

8. When blood flows through Peripheral Chemoreceptors (from aortic + carotid bodies) + Central Chemoreceptor

à detect increase in H⁺ conc

à send impulses to breathing control centre (in medulla oblongata)

à sends impulses to diaphragm + external intercostals muscles to contract faster

à breathing rate increases (to expel excess CO2)

à lungs expand (for faster breathing)

à stimulates stretch receptors (in lungs)

à send impulses to the breathing control centre

à sends impulses (via parasympathetic nerve) to the diaphragm + external intercostals muscle

à to slow down the contraction

à breathing rate returns to normal

à negative feedback reaction.

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.