Transcript Chapter 5

The Working Cell: Energy Formation and Usage
Energy—The capacity to perform work.
Two Types:
Potential- stored energy that is not doing work but
can. Example: racehorse in starting gate, gas in
car tank, couch potato watching tv
Kinetic- energy of motion. Example: racehorse
running down track, car moving down road, couch
potato studying Biology
Two Laws of Energy:
1. Energy cannot be created or destroyed, it can only be
converted from one form to another.
2. During conversion, some energy is lost as heat. This
increases the “entrophy”, or disorder, of the universe.
Ultimate source of all energy is the:
SUN
Nearly all energy
processes can be
traced back to the sun.
plants start the process
by absorbing the light
and turning it into sugars
that are passed down
the food chain.
ATP used to power cellular work.
ATP = Adenosine Tri-Phosphate
-nucleotide
-energy is located in between phosphate bonds
-by removing a phosphate the ATP molecule releases
energy much like a spring after you have compressed it.
- ATP – P = ADP (Adenosine di-phosphate) + a free P
Body recycles the entire supply of ATP about 1 x every minute.
One teaspoon of ATP provides enough energy to do about 15
minutes of moderately strenuous activity.
Average Joe uses about 408 lbs of ATP/24 hr period.
We can recycle the free P by using some of the energy released
during the first reaction to reattach it to an ADP molecule.
This process is called “phosphorylation” and is important
in helping keep the energy process in your body going.
Build ATP with energy
harvested from fuel
molecules in the cell…
like glucose.
Break down ATP
to provide the
cell with energy to
carry out various
cell functions.
Enzymes…Again!!
Review:
-catalysts…speed up chemical reactions
-belong to protein class of macromolecules
-lower the activation energy of reactions
Specific shapes of enzymes only allow them to catalyze one
type of reaction.
ENZYMES ARE NOT INTERCHANGABLE.
Sometimes products
are formed by enzymesubstrate reactions like
proteins formed by
amino acids joining.
Each reaction has a specific enzyme that will fit with a
SUBSTRATE at the ACTIVE SITE and cause the reaction to
happen.
Enzyme/Substrate complex is much like a lock and key. Any
change in the shape of one prevents the lock from opening.
Sometimes substrates are
broken down by enzymesubstrate reactions (like complex
carbohydrates such as table
sugar being broken down to
glucose)
http://karimedalla.files.wordpress.com/2012/10/enzyme5.gif
Inhibitors can block reactions
from happening.
Competitive Inhibition (a)
-inhibitors take the place of
the enzyme. They mimic the shape
and combine with the substrate at the
active site before the enzyme does
preventing the enzyme and substrate
to combine properly.
Example: same key fits two different
locks, but only turns one of them
http://www.tokresource.org/tok_classes/biobiobio/biomenu/enzymes/competiti
ve_inhibit_c_la_784.jpg
Non-Competitive Inhibition (b)
-inhibitors attach to the enzyme at a site remote to the
active site which doesn’t affect the substrate but does
change the shape of the active site so the substrate no
longer fits the puzzle.
Example: key gets smashed and no longer fits the lock
so it cannot turn it
Practical Application of Enzymes:
Penecillin, the “wonder drug”
produces an enzyme that inhibits the
formation of a cell wall in bacteria. Without
the protection of a cell wall, white blood cells
can attack the bacteria. Since humans don’t
share enzymes with bacteria, we can
use it without causing harm to any body
cells.
Cyanide inhibits O2
movement in all
organisms.
http://www.thenutritionpost.com/w
p-content/uploads/2011/08/bugspray.jpg
Many insecticides used
to kill insects are enzymes
that inhibit various functions
in the body, such as nervous
system functioning. They
can do the same thing to the
human nervous system that
they do to insect nervous
systems.
Using Energy to Move Things Into and Out of the Cell
Movement into and out of the cell can
happen with or without E.
Movement that requires energy is called:
ACTIVE TRANSPORT-use energy to push molecules against the concentration
gradient…in other words…you are trying to fill up a space
that is already full.
-imagine rowing a canoe upriver, against the current
-important in keeping the cell “balanced” with some
molecules…Sodium/Potassium pump in muscle cells helps
keep nerves going.
-energy usually comes from ATP
-Fig. 5.15, pg. 82
Other movement across the cell membrane requires no E.
This is called PASSIVE TRANSPORT.
-Movement is with the concentration gradient. No energy
is needed to “go with the flow.”
-Imagine rowing a canoe down
river with the current.
Different Types of Passive Transport:
DIFFUSION:
-movement of molecules from areas of
higher concentration to areas of low
concentration
-Examples: iced tea in a pitcher of
water, O2 and CO2 in the
blood being exchanged, methane
gas moving into the air
when released by the bowels, i.e.
farting.
Water moves by diffusion in a class of it’s own. It is the only
molecule that has free passage across the cell membrane.
Thus:
OSMOSIS
-is the movement of water from areas of higher
concentration to areas of lower concentration.
-controls both solute concentration and volume in
cells.
Isotonic cells have equal amounts of solute and
water both inside the cell membrane and
outside the cell membrane.
Thus, there is no net movement of
water across the membrane. Most cells desire
to be isotonic.
APPLICATION: Blood has an isotonic saline
concentration of 0.9%. When hospitals give you an I.V.,
they use 0.9% saline so they don’t upset the isotonicity of
the blood.
Isotonic Cell Fluid Exchange
Solute=50%
H2O=50%
Equal
exchange
Solute=50%
H2O=50%
Cells that are:
-HYPERTONIC have more solutes outside the
cell than inside the cell. Example: salt water in ocean.
-by osmosis, water must move from inside the cell to
outside in order to balance the solution and volume.
-loss of water will cause the cell to shrink or crenate
-animal cells will lose shape and become limp
-plant cells lose shape and become flaccid…this is when
plants wilt
Hypertonic Cell Fluid Exchange
High solute conc.
Low water conc.
The cell will
shrivel up or “crenate” due
to a loss of water.
Water will
leave the cell
in an attempt to
create an isotonic
situation.
Low solute conc.
High water conc.
Cells that are:
HYPOTONIC have more solutes on the inside of the cell
than on the outside.
Thus, water moves into the cell by osmosis.
Animal cells will swell and burst or lyse.
Plant cells become “turgid” (develop turgor pressure)
and look healthy. They cannot burst due to the strength
of the cell wall.
Hypotonic Cell Fluid Exchange
Water will enter the
cell very rapidly in
an effort to provide
an isotonic
environment.
Low water conc
High solute conc
Low water conc
High solute conc
Plant cells just
become more
turgid.
This will cause animal
cells to swell and burst.
High water conc
Low solute conc
Review:
Can you identify the characteristics of each set of cells?
Isotonic
Hypotonic
Hypertonic
Explain how you can easily die of thirst if you get lost on the
ocean?
Sodas usually won’t quench your thirst. Why not?
What organelle do plants store water in to make them turgid?
How do protists that live in fresh water ponds and lakes avoid
bursting because of the environment they live in?