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Chapter 5
The Working Cell
Cell ActivitiesCells have three basic
types of activities1. transport2. chemical
3. mechanical
Cell Activites
Transport Activities
Transport Mechanisms
Transport Mechanisms I. Passive transport
Passive transport mechanisms do not require the cell to input any
energy.It is dependent on two things:
1. The innate energy and movement of atoms and molecules
2. A concentration gradient
Transport MechanismsI. Passive transport
All atoms and molecules are in a constant state of motion.
Large molecules move slower than small ones.
Warm molecules move faster than cold ones.
Gases are more active than liquids which are more active than solids, but
all molecules move.
Transport Mechanisms I. Passive Transport
A concentration gradient occurs as molecules spread out into a space.
According to Newton’s Laws of motion, an atom or molecule moves in a straight line until it collides with
another force that causes it to change direction.
Transport MechanismsI. Passive transport
All passive transport mechanisms are really variations of diffusion.
Diffusion refers to a movement of molecules from an area of greater concentration to an area of lesser
concentration along a concentration gradient.
If the molecules are in an idealized closed system, they will ultimately
spread out and become equally dispersed throughout the space.
Passive Transport Mechanisms
A. Simple diffusionSimple diffusion is the diffusion of molecules as they move through open
space or through a membrane.As with all diffusion, the molecules
move from an area of greater concentration to an area of lesser
concentration.
Transport MechanismsA. Simple Diffusion
Initially the molecules are highly concentrated in one area.
As they move, they bump into each other and the confining
walls of their space.
Passive Transport Mechanisms
A. Simple diffusionWhen we open a perfume bottle in a room, the aromatic molecules begin to
move out of the bottle and into the larger space. This is an example of
simple diffusion.Oxygen moves out of the lung and into
the blood by simple diffusion.Also, carbon dioxide moves out of the
blood and into the lung by simple diffusion.
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport Mechanisms
A. Simple diffusion
Passive Transport MechanismsB. Osmosis
Osmosis is the diffusion of water through a membrane.
The process depends on the concentration of the molecules
dissolved in the water since these molecules exert osmotic pressure.
However, the dissolved molecules do not pass through the membrane during
the process of osmosis.
Passive Transport MechanismsB. Osmosis
During osmosis, water will move to the side of the membrane with the most
concentrated solution (the saltier side).Although, when we label a solution, we label it according to the concentration of the solute (dissolved material), not the
solvent (water).A 10% salt solution is 90% water. It is
important to keep this in mind when discussing osmosis.
Passive Transport MechanismsB. Osmosis
Also, in considering osmosis, it is important to understand that we are
comparing the solution outside the cell (A) to the solution inside the cell (B). In other words, we compare the solutions
on either side of the membrane.
Passive Transport MechanismsB. Osmosis
If the two solutions are equal in concentration, than A is isotonic to B
and B is isotonic to A.“iso” means “the same” and “tonic”
refers to the saltiness (or solutes).A=0.9% solutes
B=0.9%solutes
Isotonic isotonic
Passive Transport MechanismsB. Osmosis
If solution A has a higher concentration of solutes than solution B, A is hypertonic to B.
“hyper” means “more than”At the same time, solution B is hypotonic to A.
“hypo” means “less than”
A=10% solutes
B=0.9%solutes
hypertonic hypotonic
Passive Transport MechanismsB1. Osmosis
This is a U shaped tube with a membrane inside, at the bottom of the U, separating
side A from side B.
membrane
Passive Transport MechanismsB1. Osmosis
Side A has a concentration of 10% purple molecules
(the blue dots are water).Side B has a concentration of
20% purple molecules.A is hypotonic to B.B is hypertonic to A.
Passive Transport MechanismsB1. Osmosis
Since side B is the “saltier” side, water moves from side A to side
B
Passive Transport MechanismsB1. Osmosis
The solution level in side B rises while the solution
level in side A drops.
Passive Transport Mechanisms
B. How Osmosis affects cells
The solution (cytoplasm) inside most cells has a concentration of
approximately o.9%.Although this does vary some, for our purposes, we are going to consider this concentration a constant for all cells.
Passive Transport Mechanisms
B2. Osmosis in Animal CellsWhen a blood cell is placed into a solution
with a concentration of 0.9% salt, the solutions inside and outside of the cell are isotonic to each other. Water moves into
and out of the cell at an equal rate. The cell is not affected by this solution. It remains
normal and functional.
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
0.9%
0.9%
Passive Transport Mechanisms
B2. Osmosis in Animal CellsWhen a blood cell is placed in a 10% salt solution, the outside solution is hypertonic to the solution inside the cell. The solution inside the cell is hypotonic to the outside solution. Water will move out of the cell at a faster rate than it moves into the
cell.
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
The cell shrinks as it loses water. Finally, the cell collapses. This
collapse is called crenation. In this form, the cell can no longer function
and will die.
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
0.9%
10%
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
Passive Transport Mechanisms
B2. Osmosis in Animal Cells•When an animal cell is placed in
distilled water, the solution inside the cell is hypertonic to the outside solution. The outside solution is
hypotonic to the solution inside the cell. Water moves into the cell at a
faster rate than it moves out.
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
•The cell swells and swells and swells and eventually ruptures.
•The rupturing of a cell is called lysis.
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
0.9%
D.I. water
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
.
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
Passive Transport Mechanisms
B2. Osmosis in Animal Cells
Should you look for this cell under the microscope, you would only find little bits of membrane, or, more likely, nothing at all.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
•A plant cell in a hypertonic solution will lose water mainly from its central
vacuole.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
•The central vacuole shrinks, the cell membrane collapses and all the
organelles inside the membrane get crowded together. This is called
plasmolysis.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
In general, the size of the cell does not change because the cell wall is
rigid and does not collapse. However, in this condition, the cells have no
pressure to hold up the leaves of the plant. It wilts.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
0.9%
10%
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
•A plant cell in a hypotonic solution will take
water into the central vacuole.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells•The vacuole swells, pushing the cell membrane against the cell wall. All the organelles are pushed out to the periphery of the cell. This is called
turgor.•This is the ideal condition for the plant because it creates a pressure in the cells
which allow them to hold up their leaves and flowers.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
The cell does not rupture because the cell wall is rigid and creates an opposing pressure that equalizes with the osmotic pressure.
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
0.9%
D.I. water
Passive Transport Mechanisms
B3. Osmosis in Plant Cells
Passive Transport MechanismsC. Dialysis
Dialysis is the movement of particles across the membrane.These particles are pulled through the membrane with
water that is diffusing through.
Passive Transport MechanismsC. Dialysis
Passive Transport MechanismsC. Dialysis
Passive Transport MechanismsC. Dialysis
Passive Transport Mechanisms
D. Carrier Facilitated DiffusionCarrier facilitated diffusion relies not only on the concentration of particles on
either side of the membrane. Carrier facilitated diffusion requires a
membrane carrier protein to carry the particles across the membrane.
Still, it is a diffusion process and does not require an input of energy from
ATP.
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Passive Transport Mechanisms
D. Carrier Facilitated Diffusion
Active Transport Mechanisms
II. Active TransportUnlike passive transport, active transport
does require an input of energy from the cell.
Another important difference between active and passive transport mechanisms is
that active transport can move particles against the concentration gradient, from an area of lesser concentration to an area of
greater concentration.
Active Transport Mechanisms
II. Active TransportIn situations where the cell needs to take in
all the particles it can despite concentration, it is important to have this option.
As you take in and digest nutrients, the cells that absorb the nutrients may start out with a lesser concentration, but as more and more
move into the cell, the concentration becomes greater inside the cell, but the cell still needs
to continue taking in more.
Active Transport Mechanisms
A. Typical Active TransportLike carrier facilitated diffusion, typical active transport requires a membrane carrier protein to bring the particles across the membrane.
However, ATP is required to activate the carrier and bring the
particle across.
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
ATP ATP
Active Transport Mechanisms
Active Transport
ADP + P
ADP + P
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
Active Transport
Active Transport Mechanisms
B. Co-TransportCo-transport is similar to typical
active transport except, in this case, a second type of particle attaches itself to the original particle and both are pulled
through the membrane at the same time (piggyback).
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
ATP ATP
Active Transport Mechanisms
B. Co-Transport
ADP + P
ADP + P
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
B. Co-Transport
Active Transport Mechanisms
C. Exchange pumpAnother example of an active
transport mechanism is the exchange pump.
This process involves moving one type of molecule to the inside of the cell while moving a different type of molecule to the outside of the cell.
Active Transport Mechanisms
C. Exchange pump When a nerve or muscle cell becomes
electrically charged, sodium ions rush out of the cell and potassium ions rush in (by diffusion).
In order for these cells to come back to their resting state, the ions must be returned to their
original place.The Na+/K+ pump pulls sodium ions into the
cell and potassium ions are pulled out of the cell.
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
ATP ATP
Active Transport Mechanisms
C. Exchange pump
ATP
ADP + P
ADP + P
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Active Transport Mechanisms
C. Exchange pump
Transport by VacuoleIII. Transport by Vacuole
Large molecules and cells cannot pass through the membrane by passive or
active transport.The only way to bring these into the cell
is by forming vacuoles.The cell also transports large molecules
out of the cell by vacuole. These mechanisms require the cell to expend a considerable amount of energy.
Transport by VacuoleA. Endocytosis
The process of bringing cells and large molecules into the cell by vacuole is called Endocytosis.
There are 3 forms of endocytosis.1. Phagocytosis means “cell eating”.2. Pinocytosis means “cell drinking”. 3. Receptor (membrane) mediated
endocytosis which uses receptor proteins on the membrane to initiate
the reaction.
Transport by VacuoleA1. Endocytosis/Phagocytosis
Cells like your white blood cells often take in bacterial cells to protect you from infection. Other cells (especially unicellular organisms or protozoa) take in small cells as food. In order to bring in a complete cell, the cell
membrane rises up, surrounds and engulfs the cell.
Also, phagocytosis may bring in large chunks of materials like splinter fragments.
Transport by VacuoleA1. Endocytosis/PhagocytosisAs the membrane closes over the
material to come in, membrane touches membrane and the
molecules reorganize so that the inner membrane forms a vacuole inside the cell that separates from
the membrane.
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA1.
Endocytosis/Phagocytosis
Transport by VacuoleA2. Endocytosis/Pinocytosis
Taking in fluid requires a different approach.
The cell membrane invaginates forming an inpocket.
As the pocket forms, it creates a vacuum that sucks the extracellular fluid along with
large molecules into the pocket.The membrane then closes over the top and pinches off the vacuole inside the cell.
Transport by VacuoleA2.
Endocytosis/Pinocytosis
Transport by VacuoleA2.
Endocytosis/Pinocytosis
Transport by VacuoleA2.
Endocytosis/Pinocytosis
Transport by VacuoleA2.
Endocytosis/Pinocytosis
Transport by VacuoleA2.
Endocytosis/Pinocytosis
Transport by VacuoleA3. Endocytosis/Receptor
MediatedReceptor Mediated Endocytosis is
much like pinocytosis, but more specific.
Receptors in the membrane attract and capture specific molecules, although
extracellular fluids do enter the newly forming vacuole as well.
Transport by VacuoleA3. Endocytosis/Receptor
MediatedY Y Y Y Y
Transport by VacuoleA3. Endocytosis/Receptor
MediatedY Y Y Y Y
Transport by VacuoleA3. Endocytosis/Receptor
Mediated
Y
Y
YYY
Transport by VacuoleA3. Endocytosis/Receptor
Mediated
Y
Y
YYY
Transport by VacuoleA3. Endocytosis/Receptor
Mediated
Y
Y
YYY
Transport by VacuoleA3. Endocytosis/Receptor
Mediated
Y
YYY
Y
Transport by VacuoleB. Exocytosis
The process of releasing vacuole-encased molecules from the inside of the cell is
called Exocytosis. The vacuole is formed within the cell and
then fuses with the cell membrane as it releases its
contents.
Transport by VacuoleB. Exocytosis
As the cell forms proteins and other materials for export out of the cell, the endoplasmic reticulum or the golgi package these materials in
vacuoles.This vacuole moves through the cell
until it reaches the cell membrane.
Transport by VacuoleB. Exocytosis
As the vacuole bumps into the cell membrane, membrane touches
membrane and the molecules reorganize.The membrane of the vacuole is
incorporated into the cell membrane and as the membrane stretches out, the
materials inside the vacuole is left on the outside of the cell.
Transport by VacuoleB. Exocytosis
Transport by VacuoleB. Exocytosis
Transport by VacuoleB. Exocytosis
Transport by VacuoleB. Exocytosis
Transport by VacuoleB. Exocytosis
Transport by VacuoleB. Exocytosis
EnzymeActivities
Energy and the Cell Energy
Energy = the capacity to do work.Kinetic energy = energy of motion or energy used to do
work.Potential energy = stored energy.
Energy and the CellLaws of ThermodynamicsThere are 2 laws of physics that concern energy transformations.
They are called the Laws of Thermodynamics.
Energy and the Cell1st Law of
Thermodynamics =Energy conservation
the amount of energy and matter in the universe is constant;
It can neither be created nor destroyed…it can change form.
Energy and the Cell2nd Law of Thermodynamics =
the Law of Entropy (chaos) The universe is moving towards entropy
or energy in the universe is becoming
more chaotic.Energy transfers or transformations
are not 100% efficient. Some energy is always lost in the
form of heat.
Energy and the Cell Chemical reactions
Endergonic reactions= require energyExergonic reactions= release energy
Exergonic reactions often drive endergonic reactions.
This is called Energy or reaction coupling.
ATP ADPCO2 + H2O Glucose + O2
Chemical ReactionsThe chemical reactions in the cell
are collectively called metabolism or metabolic reactions.There are 2 forms of metabolism1. anabolic reactions – build large
molecules from smaller ones. 2. catabolic reactions – break down
large molecules into smaller ones.
Chemical ReactionsTypical reactions
Substrate(s) (reactants) are converted to product(s)
Or
Or
+
++
+anabolic
catabolic
mixed
Chemical ReactionsEnzymes
Catalyst - speeds up the rate of a reaction
Biological catalyst - a catalyst that is safe to use in a living cell.
Enzymes are biological catalysts.
Enzymes are not changed by the reaction.
Can be used again and again
enzyme
Substrates are converted to product with the help of the enzyme
+
Enzymes
Enzyme at the start of the
reaction
Unchanged Enzyme at the
end of the reaction
Metabolic PathwayMetabolic pathway = a
series or chain of reactions.
Product of one reaction becomes substrate for next+ + +
A + B F + GD + EC
Metabolic PathwayEach reaction has a separate
enzyme.
Enz 1 Enz 2 Enz 3+ + +A + B F + GD + EC
Metabolic PathwayAlternate pathways are determined by enzymes
If Enzyme 3 is present, D will be converted to F and G the original pathway will be completed with
these final products. But if Enzyme 4 is present D will be converted to W and X and the alternate pathway
will occur, resulting in the final products Y and Z.
Enz 4
Enz 5
Enz 1 Enz 2 Enz 3+ + +A + B F + GD + EC
+
W + X Y + Z
+
EnzymesEnzymes :
1. are biological catalysts.2. are usually made at least
partly of protein.3. are substrate specific.
4. can be induced or inhibited.
EnzymesGeneralized enzyme
structure
Apoenzyme = protein part of
the enzyme
Coenzyme (organic) or
cofactor (inorganic) =
non-protein part of the enzyme
Active Site = where the substrate fits into the
enzyme
Allosteric site = where the enzyme is activated
or deactivated
enzyme
EnzymesActivation of an enzyme
An enzyme may be activated by placing an activator molecule into the allosteric site. This process
causes the shape of the active site to change so that the substrate can fit
into the active site.
EnzymesActivation of an enzyme
This is called positive allosterism.Without the activator molecule, the active site remains closed off so that
the substrate cannot fit into it.
EnzymesGeneralized enzyme
structure
Inactive enzyme
activator
substrate
EnzymesGeneralized enzyme
structure
activated enzyme
activator
substrate
EnzymesGeneralized enzyme
structure
activated enzyme
activator
substrate
EnzymesInhibition of an enzyme
An enzyme may be inhibited by placing an inhibitor molecule into the allosteric site. This process
causes the shape of the active site to change so that the substrate can no longer fit into the active
site.
EnzymesInhibition of an enzyme
This is called negative allosterism.
Without the inhibitor molecule, the active site remains open so that the substrate fits into it.
Enzymes
Example of negative allosterism
EnzymesHow an Enzyme Works1.E + S The substrate bumps into the
enzyme and aligns with the active site.2.E-S complex The substrate fits into the active site, and the enzyme shifts,
stressing the bonds of the substrate.3.E + P The products are formed and
released.4.The enzyme returns to its original shape
and can be used again.
EnzymesHow an Enzyme Works
EnzymesHow an Enzyme WorksAll enzymatic reactions require some
energy to get them started. This energy is called the energy of activation.
Enzymes reduce the energy of activation so that it takes much less energy to get the reaction going. Once started, the
reaction will continue on its own steam.
Enzymes
Enzymes
EnzymesFactors that affect the rate
of an enzymatic reaction 1. temperature
2. pH3. enzyme concentration
4. inhibitors
Enzymes1. Temperature profile
Every enzyme has a temperature profile. This profile is a graph
showing at what rates the reactions take place at various temperatures.
The temperature profile generally forms a “bell-shaped” curve.
Enzymes 1. Temperature profile
The peak of the curve represents the optimal temperature. This is the
temperature at which the reaction rate is fastest.
As temperature cools from optimal, molecules slow down and do not
encounter each other as often or with as much energy, so the reaction rate slows
down until the reaction no longer occurs. This temperature is called the minimal
temperature.
Enzymes1. Temperature profile
As temperature becomes warmer than optimal, enzymes begin to change shape. This change
in shape is called denaturing the enzyme. If the temperature gets too warm, the enzyme
changes so radically that the substrate can no longer fit into the active site. The reaction rate is then 0 (no reaction occurs) and the enzyme is
irreversibly denatured. This temperature is called the
maximal temperature.
Enzymes1. Temperature profile
The range of temperatures between the minimal and maximal is called the functional range. This is the range of
temperatures within which the enzyme works.
Enzymes1. Temperature profile
Minimal temperature
Maximal temperature
Functionalrange
Enzymes1. Temperature profileEvery enzyme has a unique
profile based on the type of organism it is found in and/or the location in the organism where it
does its work.
Enzymes1. Temperature profileAmong mammals, smaller mammals tend to have higher
normal body temperatures than larger mammals. As a result, one
would expect the optimal temperature for a small mammal
to be at a higher temperature than the optimal for larger mammals.
Enzymes1. Temperature profile
Cold blooded animals do not regulate their body temperatures as closely as mammals, so their functional range may be broader
than that for mammals.The enzymes that work in cells all over the
body also need a broader functional range.Enzymes that work outside the body
(digestive enzymes of fungi or the enzymes that work in the testes) usually have a
cooler optimal temperature than enzymes that work inside the body.
Temperature in oC
Temperature Profile for various enzymes
Enzymes 2. pH profile
As with temperature, enzymes have a pH profile. This profile is a
graph showing at what rate the reaction takes place a various pHs.This profile also, generally forms
a “bell-shaped” curve.
Enzymes2. pH profile
The peak of the curve represents the optimal pH. This is the pH at which the
reaction rate is fastest. As the pH becomes more acidic or more
basic than optimal, the enzyme begins to denature.
When the enzyme no longer functions, it is irreversibly denatured. The points where this occurs will be the minimal
and maximal pH and the range between the two is the functional pH range.
Enzymes2. pH profile
Minimal pH Maximal pHFunctional range
Enzymes 2. pH profile
Every enzyme has a unique profile based primarily on where in the organism it functions.
A blood enzyme has a very narrow range that is slightly basic.
Stomach enzymes have a very low pH optimal.Pancreatic enzymes work best at a neutral pH.
Catalase, which breaks down hydrogen peroxide, has a broad range of pHs at which it works, since it must work in every cell of the
body.
Enzymes 3. Enzyme Concentration
The concentration profile for enzymes is quite different than the temperature and pH profiles. Initially, there is a steep positive correlation
between enzyme concentration and reaction rate, but at a certain point, using more enzyme cannot make the rate go faster and the curve levels off
into a plateau. There is no minimal or maximal concentration. The optimal concentration occurs just before the
plateau.
Enzymes3. Enzyme concentration
Enzymes4. Inhibitors
The more inhibitor present, the slower the reaction rate.
2 typesa. Competitive inhibitors
b. Non-competitive inhibitors
Enzymes 4a. Competitive Inhibitors
A competitive inhibitor partially mimics the substrate molecule and blocks the active site.
This inhibition is temporary since the inhibitor can move into or out of the active site.
The substrate and the inhibitor compete with each other for access to the enzyme.
Often competitive inhibitors are produced by the body to slow down the speed of a reaction.
Enzymes 4b. Non-competitive
InhibitorsA Non-Competitive inhibitor blocks the allosteric site or removes co-enzyme or co-
factor from the enzyme. A blocked allosteric is sometimes
temporary and reversible.A removed co-factor or co-enzyme destroys
the enzyme and is permanent.
EnzymesInhibitors
MechanicalActivities
Mechanical Activities Mechanical activities of the cell
involve movement of some sort.At the cellular level, mechanical
activities would include the following:cytoplasmic streaming amoeboid movement
The beating of cilia and flagellaThe movement of centrioles, microtubules
and chromosomes during cell division
Mechanical Activities Other cell-level mechanical
activities include the following:The movement of RNA out of the
nucleus.The movement of vacuoles,
mitochondria, plastids and other organelles.
Endocytosis and exocytosis are transport activities with a mechanical aspect.
Mechanical Activities Mechanical activities at the organism level
might include: Muscle contraction allowing gross
movement of the body.Peristaltic contractions of the digestive tract
The pumping action of the heartThe movement of blood through the vessels.
The movement of air into and out of the lungs.
Mechanical Activities
Most mechanical activities require ATP breakdown and the cells must
metabolize foods in order to maintain a constant supply of the
ATP.