Name: Human Respiratory System
Uploaded: 2019-07-19
Duration: 4 min 39 s
Description: Fishes need gills for respiration, while frogs have skin as one of their respiratory organs. Check out this video for details about the respiratory organs in humans.

Question

Describe various pathways of glucose breakdown in organisms.

Accepted Answer

The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways – some use oxygen to break-down glucose completely into carbon dioxide and water, some use other pathways that do not involve oxygen. In all cases, the first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm. Further, the pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration.
Glucose ( $6 -$ carbon molecule) $\overset{I n c y t o p l a s m}{\to}$ Pyruvate ( $3 -$ carbon molecule) $+$ Energy $\to_{(i n y e a s t)}^{A b s e n c e o f o x y g e n}$ Ethanol ( $2 -$ carbon molecule) $+$ Carbon dioxide $+$ Energy

Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide. The other product is water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration. The release of energy in this aerobic process is a lot greater than in the anaerobic process.
Glucose ( $6 -$ carbon molecule) $\overset{I n C y t o p l a s m}{\to}$ Pyruvate ( $3 -$ carbon molecule) $+$ Energy $\to_{(i n m i t o c h o n d r i a)}^{P r e s e n c e o f o x y g e n}$ Carbon di-oxide $+$ Water $+$ Energy

Sometimes, when there is a lack of oxygen in our muscle cells, another pathway for the break-down of pyruvate is taken. Here the pyruvate is converted into lactic acid which is also a three-carbon molecule. This build-up of lactic acid in our muscles during sudden activity causes cramps.
Glucose ( $6 -$ carbon molecule) $\overset{I n c y t o p l a s m}{\to}$ Pyruvate ( $3 -$ carbon molecule) $+$ Energy $\to_{(m u s c l e c e l l s)}^{L a c k o f o x y g e n}$ Lactic acid ( $3 -$ carbon molecule) $+$ Energy

Describe various pathways of glucose breakdown in organisms.

Important Questions on Life Processes

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