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Metabolism
Defining Energy
Potential energy is the capacity to do work.
Kinetic energy is the energy of motion.
ATP is the cell’s energy source
Potential energy of molecules is known as chemical energy.
Energy that is not given off as kinetic energy is given off as thermal (heat) energy. Heat energy is considered “wasted energy”
Laws of Thermodynamics
First law –Energy is not created or destroyed only transferred between forms.
The total amount of energy in the universe remains constant.
Second law -- No energy conversion can ever be 100% efficient.
Energy always flows from more useful forms of energy to forms that are less useful.
Endergonic reaction
Uphill reaction
Energy is put into the reaction
For example: Glycolysis
Energy of a reaction over time
0
5
10
15
20
25
30
35
40
1 2 3 4 5 6 7 8 9
Time (s)
En
erg
y (J
ou
les)
Series1
Exergonic reaction
Energy over time in a reaction
0
20
40
60
1 2 3 4 5 6 7
Time (s)
Ene
rgy
(Jou
les)
Series1
Downhill reaction
Energy is released during the reaction
Example: The Kreb’s cycle andelectron transport system
ATP Adenosine Triphosphate
Consists of a 5 carbon sugar and 3 phosphate groups.
It is the cell’s energy source
To release energy, it will break a bond between phosphates
Enzyme Structure & Function
Enzymes – speed up the rate of a reaction. Also called a catalyst
Equilibrium - when a reaction is running at the same rate forward as well as in reverse.
Four shared features
1. Enzymes do not make anything happen that could not happen on its own, it just makes it happen faster.
2. Reactions do not permanently change or use up an enzyme
3. The same type of enzyme usually works whether the reaction is occurring in a forward or reverse motion
4. Each type of enzyme is very picky
Enzyme-Substrate interactions Activation energy - the energy
that must be provided in order for the reaction to begin.
Enzymes lower the amount of activation needed to begin a reaction.
Enzymes have one or more active sites
At these places, enzymes interact with their substrate.
Active Site A specific shape that will only fit a
specific substrate. (Like a lock & Key).
When the substrate locks into the active site, the reaction can begin with a lower activation energy because bonds are weakened within the molecule.
Factors influencing Enzyme Activity
1. Temperature – enzymes only work in a certain temperature range
2. pH – measure of amount of acid or base in the solution
3. Salinity – measure of salt content in the solution
4. Feedback Inhibition – mechanism where a cellular change that resulted from an activity stops the activity that caused the change
Working with and against a concentration gradient
A concentration gradient is the difference in the number of molecules of a given substance in two adjoining regions.
In the absence of an opposing force, molecules move from an area of high concentration to an area of low concentration
Diffusion
The net movement of like molecules from high concentration to low concentration (also called down the gradient)
Passive Transport
Requires no extra energy in order to occur.
The flow of dissolved material across a
membrane through transport proteins following the concentration gradient.
If allowed to, this movement would occur until both areas had equal concentration of the solutes.
Osmosis
The diffusion of water molecules across a semi-permeable membrane.
Hypotonic solution
When too much water is moving into the cell and not enough water is leaving the cell
Hypertonic solution
When too much water is leaving the cell and not enough is entering.
Water tends to diffuse from hypotonic solution to hypertonic solutions
Isotonic solutions
Water is moving equally into and out of the cell.
Cell is in a state of equilibrium
Active Transport
Movement across the membrane against the concentration gradient.
This movement requires energy.
ATP provides the energy.
Vesicle Formation
Molecules too large to be transported by carrier proteins are moved into or out of the cell by vesicle formation.
Exocytosis
A vesicle fuses with the membrane and secretion occurs.
Endocytosis
Cells take in substances by vesicle formation.
Phagocytosis
When the material taken in is large and usually a “food”
Pinocytosis
Occurs when the particles taken in are a liquid.
Works Cited
http://biology.unm.edu/ccouncil/Biology_124/Images/tonicity1.jpeg
http://www.greenscreen.org/articles_sr/energy/images_potential_kinetic_energy/potential_kinetic.jpg
http://regentsprep.org/Regents/biology/units/homeostasis/lockkey.gif
http://bassethound.files.wordpress.com/2007/04/sharris-deptofentropy.gif
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