Matter and Energy Pathways in Living
Systems
Pre-unit quiz
http://www.mcgrawhill.ca/school/learningcentres/mod/quiz/attempt.php?id=21081
Mitochondria:
- Only the cells of eukaryotic organisms contain the
mitochondria
- Enable cells to efficiently take energy from the food
- Smaller in size compared to the chloroplast
- Bound by two membranes, the inner membrane has a
fluid-filled space called the matrix (contains proteins and
chemicals required to break down carbohydrates and high
energy molecules)
- The inner membrane has a large fold called “cristae”
which provides a large surface area for the production of
ATP.
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Metabolic Pathways and Energy for Cellular Reactions
- Photosynthesis and Cellular Respiration seems to be exact
opposites, however they each represent a summary of
reactions.
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- Cellular Respiration is similar to a combustion reaction
that releases energy during the burning of wood.
- The process of cellular respiration occurs in step-by-step
sequences, in which the product of one reaction becomes
the starting reactant for another.
- These are called metabolic pathways.
- Metabolism refers to all the chemical reactions that occur
within a cell to support and sustain its life functions.
- Metabolism is broken down into Anabolic or Catabolic
Metabolic pathways.
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o Anabolic Pathways: Synthesize larger molecules from
smaller ones and require energy.
o Catabolic Pathways: break down larger molecules
into smaller ones and release energy.
- Both chemical reactions need to be activated before they
can begin. (heating can start the process, but would
destroy living cells)
- All metabolic reactions are catalyzed by enzymes.
o Enzymes: Specialized proteins that lower the energy
needed to activate biological reactions.
o Enzymes enable the reaction to proceed quickly.
o Each reaction has a specific enzyme that is catalyzed.
Oxidation and Reduction Reactions (Redox reactions)
- Oxidation: When an atom or molecule loses an electron
o LEO – lose electrons oxidation
- Reduction: When an atom or molecule gains an electron
o GER – Gain electrons reduction
- Oxidation and reduction reactions are linked because the
electrons that are lost by one atom or molecule cannot
exist on their own. They must combine with another atom
or molecule.
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- Thus, when one compound is oxidized (LEO), another
compound is reduced (GER).
- All atoms contain more energy in their reduced form than
they do in their oxidized form.
- Molecules in their reduced form contain a large amount of
available energy are known to have reducing power.
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