Metabolism part 1
Transcript Metabolism part 1
Metabolism is essentially how the
cell is able to use glucose and turn it
into energy to carry on life processes.
Note: Do Not spend any time on
photosynthesis. We will not be
covering that cycle in this class.
• The definition of metabolism is the sum of all
chemical reactions that occur in a living cell. This
includes things like, protein synthesis, DNA
replication, cell growth and division, etc.
• These chemical reactions are divided into two
– Catabolism, which are the decomposition reactions in a
living organism. In other words, they are the reactions
responsible for the breakdown of complex organic
compounds into simpler ones. An example is the
breakdown of glucose.
– Anabolism, which are the synthesis reactions in
a living organism. In other words, they are the
reactions that complex organic molecules from
simpler ones. So DNA made from nucleotides.
• Catabolism and Anabolism coupled
reactions. That means that you can’t have
one without the other. For example, glucose
is broken down so that ATP can be made.
4 stages of metabolism
• There are 4 basic stages of metabolism that
we’ll discuss. They are:
• 1. Digestion;
• 2. Movement of nutrients across the cell
• 3. Glycolysis;
• 4. Kreb Cycle and electron transport chain.
• Digestion is the process in which nutrients are broken
down into small molecules that can be utilized by the cell.
• Enzymes (specialized proteins) are needed to speed up
these chemical reactions.
• Each enzyme has a specific job in the process of digestion.
– For example, amylase is an enzyme found in saliva. It’s job is to
break down starch.
In addition, each enzyme has a unique physical shape. It
is like a lock and key. Only the right shape of key will
open the lock. With enzymes, only the right enzyme can
work an a particular substance.
– For example, amylase can recognize, bind to, and break down
starch but it can’t synthesize ATP.
• Most enzymes are named by using their function as the
first half of the name and adding the suffix –ase on the end.
So when you see a word with –ase on the end you’ll know
that it is some kind of enzyme.
• Dehydrogenase: removes water
• Transferase: transfers a chemical group from one compound to
• ATP synthase: synthesizes ATP
• Bacterial cells make exoenzymes to help break down
nutrients for their use. An exoenzyme is an enzyme that is
made by the cell and excreted outside of the cell. The
exoenzym is then used to break down large molecules
outside of cell into molecules small enough to be
transported across the cell membrane.
See pages 193-196 for a figures and more detailed
• Transport refers to the movement of nutrients from outside
the cell to the inside of the cell. There are 4 types of
transport utilized by cells.
• 1. Passive Diffusion: the nutrient moves down the
concentration gradient. In other words, it moves from an
area of high concentration to an area of low concentration.
This type of transport requires No Energy.
• 2. Facilitated Diffusion: uses a carrier molecule to bring
the nutrient into the cell. The carrier molecule is one of
those proteins that it found in the cell membrane. Like
enzymes, it is specific for the nutrient that it can bind to
and bring into the cell. This type of transport requires No
• 3. Active Transport: movement of nutrients
against the concentration gradient. Active
transport requires the help of proteins in the cell
membrane and ATP. Again, this type of transport
• 4. Endocytosis: substance engulfed by cell
membrane. This type of transport is utilized by
some eukaryotic cells, such as some white blood
cells that work to clean up bacterial infections.
• In the next lecture we will focus on glycolysis,
Kreb Cycle, and the electron transport chain.
• Then we will look at how they function in aerobic
respiration, anaerobic respiration and
fermentation. Make sure you review the location
in the cell in which cellular respiration occurs for
both prokaryotic and eukaryotic cells.