أحياء لغات الباب الثالث شرح بالفيديو 3ث Respiration In Living Organisms حصريا

الخميس 07-03-2013 13:49




The plants can convert the
light energy into chemical energy in the photosynthesis process &
store it in the form of high energy compounds as glucose which can
transferred from one cell to another & from living organism to
another.

Q. Differentiate between gaseous exchange (breathing) & cellular respiration.

Ans.

Gas exchange

It is the exchange of O2 and CO2 between the living organism
&the outer medium in unicellulars or through the respiratory system
in multicellulars.

Cellular respiration:

It is the process by which energy is extracted from the chemical
bonds in the food molecules, this energy is utilized in generating ATP
molecules, which is used in performing its vital activities of the
cells, and the best food material used in this process is glucose.



Structure of ATP High E. bones



Adenine Ribose
Three phosphate groups




Adenosine

1- A nitrogenous base called Adenine (A)

2- A molecule of pentose sugar (R)

3- Three phosphate groups

The weak bonds between phosphate groups are easy to be broken to release energy.

ATP ADP + 7 : 12 K.Cal.

The amount of the released energy is enough to cover the need
of simple cellular activities as keeping the body temperature constant.

The following equation summonses the process of cellular respiration & shows the amount of the released energy.


C6 H12 O6 + 6O2 respiration 6CO2 + 6H2O + 38 ATP.



Oxidation of glucose molecules during cellular respiration process takes place in three steps which are:

1- Glucolysis, {It takes place in cytosole (the clearest part of cytoplasm)}.

2- Krebs cycle (It takes place in mitochondria).

3- Electron transport (It takes place in the mitochondria).

Stages of glucose Oxidation



Hydrogen atoms are removed from the carbonic skeleton of the
glucose molecule, then pass to the hydrogen carriers (co-enzymes.)

2 NAD+ + 2H 2 NADH + H+{ receives one proton & 2e-}

2ADP+2PO4 2ATP

FAD + 2H Energy FADH2

Structure of the Mitochondria

It surrounded by double membrane.

The outer membrane is smooth but the inner membrane folded forming Cristae.

The Cristae contains enzymes,

electron carriers called cytochromes

& hydrogen carriers

The matrix is a dense fluid

contains enzymes, Co- enzymes,

H2O phosphate & other materials.



1- Glucolysis (Splitting of the glucose molecule)

In the Cytoplasm each glucose molecule is oxidized & split
into two molecules of Pyruvic acid (3C) through series of biochemical
reactions.

fermentation

C6H12O6 respiratory enzymes 2 C3H4O3 + 2 ATP

Glucose (6C) Pyruvic acid (3C)


Glucose change into Glucose 6 phosphate,then fructose 1-6 diphosphate

Fructose 1-6 diphosphate divided into two molecules of phosphoglyceraldehyde (PGAL)

PGAL is oxidized into two molecules of pyruvic acid but two
molecules of co-enzyme NAD+ are reduced into NADH & two molecules
of ATP are formed in the cell cytosole .

Glucolysis does not require O2 therefore it known as anaerobic respiration or fermentation step.


2- The Krebs cycle ( Oxidation steps (in the matrix) (by Sir Hans Krebs)

Each of The 2 Pyruvic acid molecules pass across the two
membranes of the mitochondria& changes into 2 molecules of acetyle
CO.(A) at the presence of CO.enzyme (A) & 2 molecules of CO2 release
and two molecules of 2NADH are formed.

Co.enzyme (A) act as carrier for the acetyle group from the Matrix to the Cristae.



fats molecules and amino acids are broken to form acetyle group it also combine with CO.enzyme (A) to form acetyle CO. (A).

The acetyle group & the Co-(A) are separated, Co.(A)
combine with another group while the acetyle group (2C) combine with
Oxalo acetic acid (4C) to form Citric acid (6C).

Citric acid (6C) passes through three intermediate compounds
the first is Ketoglutaric acid (5C)the second is Succinic acid
(4C)while the third is Malic acid (4C)which converted into Oxalo acetic
acid (4C).

Oxalo acetic acid (4C) which combine with the second acetyle
group to form Citric acid (6C) that repeat the cycle therefore kerbs
cycle is called Citric acid cycle.



During oxidation of the carbon atoms of the organic molecules energy is released & used in the formation of ATP from ADP.

Part of the energy is used to convert NAD+ into NADH (3
molecules in each cycle) & some energy is used to convert FAD into
FADH2 (1 molecule in each cycle).

Each glucose molecule initiates two Krebs cycles.

NAD = Nicotinamide Adenine Dinucleotide.

FAD = Flavin Adenine Dinucleotide



Q. GR.. Krebs cycle does not need Oxygen?

Ans. Because oxidation of organic molecules takes place by the
release of electrons, The released electrons & protons are received
directly by the Co-enzymes NAD+ & FAD.

Q. GR.. Krebs cycle does not need Oxygen but it can not start at the absence of oxygen !!!?

B- Electron transport:


½ O2 + 2H+ + 2 e- H2O

law energy water

electron vapour

When FAD & NAD+ receive hydrogen from the oxidized glucose
molecule FADH2 & NADH release the gained electrons down a chair of
electron acceptors called Cytochromes.

When the electrons descend step by step down the energy levels of the Cytochromes the energy is released.

This energy is used to form ATP molecules from ADP & E.

ADP + P energy ATP (Oxidative Phosphorilation)

When the electrons reach the lowest energy level of the
Cytochromes, they combine with protons (2H+) to form hydrogen molecules
(H2 ).

Oxygen is considered as the last receptor of the electrons in
the chain of electron transport because (H2) combine with half O2 to
form H2O.

That means 2 electrons combine with 2 protons and an O2 atom to
form one H2O molecule. ½ O2 + 2H+ + 2e- H2O

Oxidative Phosphorilation

It is the formation of ATP molecules from ADP molecules by using
the energy that released when the electrons descend step by step down
the energy levels of the Cytochromes during the electron transport .


Respiration occurs in the absence of O2 or the absence mitochondria it starts & finishes in the cytoplasm.

Glucose Oxidized into Pyruvic acid & 2ATP are produced.

Pyruvic acid reduced into either ethyle alcohol or lactic acid according to the type of the respiratory cell.

Pyruvic acid is not converted into acetyle group

❶ In yeast and plant seeds (Alcoholic fermentation)

C6H12O6 C2H5OH + CO2 + 2ATP

Glucose Ethyle alcohol carbon dioxide

❷ In animal cells and Bacteria ( Acidic fermentation )

C6H12O6 C3H6O3 + 2ATP

Glucose Lactic acid





C6H1 2O6


Glucose molecule (6C)

2NAD ADP


2NADH2 ATP


2 CH3CO-COOH

2 Pyruvic acids (3C)

2 NADH2 2 NADH2

2NAD
2 NAD


CO2

C2H5OH C3H6O3


Ethyle alcohol Lactic acid

(Alcoholic fermentation) ( Acidic fermentation )




Although Krebs cycle does not need O2

but it can not start at the absence of O2.



Comparison between aerobic and anaerobic respiratio