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Biochemistry II

Page history last edited by Darrell Sharp 11 years, 11 months ago

ATP/ADP Cycle 

Interconversion of ATP and ADP

 


  

3.7 Respiration

 

 Homework Questions          Click4Biology 

 

 

 

3.7.1 Define cell respiration. 

 

Respiration is the process in cells of producing chemical energy (ATP) from organic compounds.

 

ATP/ADP Cycle

Adenosine triphosphate (ATP) is a molecule that releases energy when it is broken down into adenosine diphosphate and inorganic phosphate (Pi). The energy released by breaking down ATP is used for most cellular activities. ADP and Pi are recycled and used to make more ATP when energy is absorbed.

 

 

 

3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

 

Glycolysis

In the cytoplasm, the process of glycolysis breaks down glucose into two pyruvate molecules, and at the same time produces two ATP molecules:

 

    glucose --> 2 pyruvate

    2 ADP + 2 Pi --> 2 ATP

 

 

 

3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. 

 

Anaerobic Respiration: without molecular oxygen (O2

 

After glycolysis, pyruvate is broken down into lactate or into ethanol and carbon dioxide depending on the kind of species. This process is called fermentation:

 

   pyruvate --> lactic acid

            or

   pyruvate --> ethanol + carbon dioxide 

 

Fermentation does not produce ATP, but it does allow glycolysis to continue which does make a little ATP.

 

Examples:  

In humans, after strenuos exercise muscle cells are sore because of too much lactate from fermentation.

In yeast, ethanol and carbon dioxide from fermentation are used to make bread and beer.

 

 

 

3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP. 

 

Aerobic Respiration: with molecular oxygen (O2

 

In the mitochondria, pyruvate is broken down with oxygen to produce carbon dioxide and water. This reaction releases energy used to make a lot of ATP.

 

   2 pyruvate + 6O--> 6CO2 + 6H2O

        34ADP + 34Pi --> 34ATP 

 

 

 

3.8 Photosynthesis

 

 

                   Click4Biology 

 

 

 

3.8.1 State that photosynthesis involves the conversion of light energy into chemical energy.

 

 

Photosynthesis is the process of using light energy to produce chemical energy.

 

 

3.8.2 State that light from the Sun is composed of a range of wavelengths (colors).

 

 

Sunlight appears white in color, but is actually composed of different colors, or wavelengths. 

 

   Rainbow

    http://climate.met.psu.edu/data/frost/frosttraining.php

 

 

 

3.8.3 State that chlorophyll is the main photosynthetic pigment.

 

 

Pigments absorb specific wavelengths of light. Chlorophyll is a pigment in chloroplasts that absorbs light energy. 

 

 

3.8.4 Outline the differences in absorption of red, blue and green light by chlorophyll.

 

 

Chlorophyll molecules absorb red and blue light but reflect green light.

 

 

3.8.5 State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen.

 

 

Photosynthesis happens in two steps.

 

In the first step, the light-dependent reactions, light energy is absorbed by chlorophyll to produce ATP, and water molecules are broken down to produce molecular oxygen and hydrogen.

 

    12H2O --> 6O2 + 24H

    ADP + Pi --(light)--> ATP

 

 

 

3.8.6 State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules.

 

 

In the second step,  the light-independent reactions, ATP and hydrogen from the first step are used to 'fix' carbon dioxide into organic molecules like glucose. 

 

   24H + 6CO2 --> C6H12O6 + 6H2O

    ATP --> ADP + Pi

 

 

 

3.8.7 Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase in biomass.

 

 

Overall equation for photosynthesis:  6H2O + 6CO--> C6H12O6 + 6O2 

 

The rate of photosynthesis can be measured in three ways:

 

 

  • measure the amount of substrate CO2 that is used.
  • measure the amount of product O2 formed.
  • measure the amount of biomass increase

 

Note: the amount of biomass is the mass of the dry organic material of the organism. But because some organic molecules produced by photosynthesis are used for respiration, this measurement is only an indirect indication of the rate of photosynthesis.

 

 

 

3.8.8 Outline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis.

 

 

As temperature increases, the rate of the reactions increases, but, after an optimum temperature, the rate decreases.

 

As light intensity increases, the rate of the reactions increases, but eventually levels off as all the chlorophyll molecules are at maximum activity. Very high levels of light intensity can damage the chlorophyll systems.

 

As carbon dioxide concentration increases, the rate of the reactions increases, but the rate eventually levels off as the enzymes become saturated.

 

 

 
     

 

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