Intro to Metabolism
Learning Outcomes
Explain laws governing energy and energy transfers.
Describe enzymes and how they work.
Explain what is meant by selectively permeable.
Explain the differences between diffusion, facilitated
diffusion, and active transport.
Explain osmosis and be able to predict the net movement
of H2O molecules under various conditions
Describe endocytosis (e.g., phagocytosis) and exocytosis
Life Needs Energy
The Rules (Laws of Thermodynamics)
1) energy can not be created or destroyed,
but it can be changed from one form to another
2) when energy is changed from one form to another
there is always some loss of usable energy
(i.e., entropy increases).
Entropy Increases
Life Needs Energy
Potential Energy --- stored energy
Kinetic energy – energy of motion
In living systems, energy is stored
in the form of chemical bonds
Life Needs Energy
In living systems, energy is stored
in the form of chemical bonds
Products
Reactants
2H2
(hydrogen
)
4 hydrogen
atoms
+
+
O2
(oxygen
)
2 oxygen
atoms
2H2O
(water
)
4 hydrogen
atoms
+ 2 oxygen atoms
Energy Transformations
Potential energy
Reactants
Amount of
energy released
Energy
Products
When chemical bonds in molecules are broken down,
energy is released.
Energy Transformations
Potential energy
Products
Energy
Amount of
energy required
Reactants
To build complex molecules energy input is required.
Enzymes Facilitate Chemical Reactions
enzyme binding
to substrates
chemical rxn
completed
product
released
Enzymes Facilitate Chemical Reactions
Free energy
Transition state
Activation energy
without enzyme
Activation energy
with enzyme
Reactants
Products
Time
Metabolic Pathways Require Enzymes
Metabolism is the sum of all chemical reactions
occurring in a living system at any given time.
Metabolic pathways are specific subsets of chemical
reactions.
Most metabolic pathways are similar in all organisms.
We will look at two important metabolic pathways
– photosynthesis and respiration
Metabolic Pathways Require Enzymes
A series of chemical reactions
form a metabolic pathway.
Each reaction in the series
is catalyzed by a specific enzyme.
The end product of a pathway
can inhibit the enzyme
that starts the pathway.
X
Where in real life do we see enzyme inhibitors?
Many of the Drugs used in medicine are enzyme inhibitors
Example 1) Aspirin
blocks an enzyme called cyclo-oxygenase
that makes pro-inflammatory molecules that
activate inflammation responses by
the immune system
Where in real life do we see enzyme inhibitors?
Example 2) Lipitor
Lipitor and other “statins”
work by blocking an enzyme called
HMG-CoA Reductase that is required
for cholesterol synthesis
CHOLESTEROL
The Lipid Bilayer is a Barrier
Phospholipid Bilayers are selectively permeable
Non-polar or hydrophobic
molecules
can pass through
Polar or hydrophilic
molecules
can not
SO - How do we get stuff
in and out of the cell?
IN –
diffusion
facilitated diffusion
active transport
endocytosis
phagocytosis
OUT exocytosis
Diffusion:
Molecules move from high concentration
to low concentration.
Diffusion:
Molecules move from high concentration
to low concentration.
Osmosis
Osmosis is the diffusion of H2O across
a semi-permeable membrane
Movement of H2O depends on
what is dissolved in the H2O
Dissolved substance = solute
Flow of H2O
Osmosis
Osmosis
Facilitated Diffusion
Molecules move down their concentration gradient – no energy input required.
Extracellular Fluid
glucose
Cytoplasm
Facilitated Diffusion
Active Transport
Energy is required to move molecules against their concentration gradient
Extracellular Fluid
Cytoplasm
Active Transport
Endocytosis
Part of the plasma membrane encapsulates material outside the cell.
Phagocytosis
similar to endocytosis, but for uptake of LARGE particles.
Exocytosis
Vesicles from the Golgi apparatus fuse with the plasma membrane
and release material to the outside of the cell.