Download Chapter 5

Metabolism
CHAPTER 5
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
 For example:
Glycolysis
40
35
Energy (Joules)
into the reaction
Energy of a reaction over time
30
25
20
Series1
15
10
5
0
1
2
3
4
5
6
Time (s)
7
8
9
Exergonic reaction
Energy (Joules)
Energy over time in a reaction
60
40
Series1
20
 Downhill
reaction
0
1
2
3
4
5
6
7
Time (s)
Example: The Kreb’s
cycle and
electron transport
system
 Energy is
released during
the reaction
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/Im
ages/tonicity1.jpeg
 http://www.greenscreen.org/articles_sr/energy/i
mages_potential_kinetic_energy/potential_kinet
ic.jpg
 http://regentsprep.org/Regents/biology/units/ho
meostasis/lockkey.gif
 http://bassethound.files.wordpress.com/2007/04
/sharris-deptofentropy.gif