Download free energy

BIG IDEA II
Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.A
Growth, reproduction and maintenance of the organization
of living systems require free energy and matter.
Essential Knowledge 2.A.1
All living systems require a constant input of free energy.
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.A.1: All living systems
require a constant input of free energy.
• Learning Objectives:
– (2.1) The student is able to explain how biological
systems use free energy based on empirical data
that all organisms require constant energy input to
maintain organization, to grow and to reproduce.
– (2.2) The student is able to justify a scientific claim
that free energy is required for living systems to
maintain organization, to grow or to reproduce, but that
multiple strategies exist in different living systems.
– (2.3) The student is able to predict how changes in
free energy availability affect organisms, populations
and ecosystems.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-2
Light
energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2 + H2O
Organic
+O
molecules 2
Cellular respiration
in mitochondria
ATP
ATP powers most cellular work
Heat
energy
Life requires a highly ordered system.
• The living cell is a chemical factory in miniature, where
thousands of reactions occur within a microscopic space.
–
Order is maintained by constant free energy input into the
system.
–
Loss of order or free energy flow results in death.
–
Increased disorder and entropy are offset by biological
processes that maintain or increase order.
• The concepts of metabolism help us to understand how
matter and energy flow during life’s processes and how
that flow is regulated in living systems.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Metabolism
• Metabolism is the totality of an organism’s chemical
reactions:
– An organism’s metabolism transforms matter and
energy, subject to the laws of thermodynamics.
• Metabolism is an emergent property of life that arises from
interactions between molecules within the cell.
• A metabolic pathway begins with a specific molecule and
ends with a product, whereby each step is catalyzed by a
specific enzyme.
• Bioenergetics is the study of how organisms manage their
energy resources.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: A Metabolic Pathway
Enzyme 1
Enzyme 2
B
A
Reaction 1
Enzyme 3
C
Reaction 2
Starting
molecule
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D
Reaction 3
Product
Catabolism and Anabolism
• Catabolic pathways release energy by breaking
down complex molecules into simpler compounds:
– Cellular respiration, the breakdown of glucose
in the presence of oxygen, is an example of a
pathway of catabolism.
• Anabolic pathways consume energy to build
complex molecules from simpler ones:
– The synthesis of protein from amino acids is
an example of anabolism.
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Forms of Energy
• Energy is the capacity to cause change.
• Energy exists in various forms, some of which can perform
work:
–
Kinetic energy is energy associated with motion.
–
Heat (thermal energy) is kinetic energy associated with
random movement of atoms or molecules.
–
Potential energy is energy that matter possesses because
of its location or structure.
–
Chemical energy is potential energy available for release in
a chemical reaction.
• Energy cannot be created or destroyed, but it can be
converted from one form to another.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
A diver has more potential
energy on the platform
than in the water.
Climbing up converts the kinetic
energy of muscle movement
to potential energy.
Diving converts
potential energy to
kinetic energy.
A diver has less potential
energy in the water
than on the platform.
The Laws of Energy Transformation
• Thermodynamics is the study of energy
transformations.
• A closed system, such as that approximated by
liquid in a thermos, is isolated from its
surroundings.
• In an open system, energy and matter can be
transferred between the system and its
surroundings.
• Organisms are open systems.
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The First Law of Thermodynamics
• According to the first law of thermodynamics,
the energy of the universe is constant:
– Energy can be transferred and transformed,
but it cannot be created or destroyed.
• The first law is also called the principle of
conservation of energy.
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The Second Law of Thermodynamics
• During every energy transfer or transformation,
some energy is unusable, and is often lost as heat.
• According to the second law of thermodynamics:
– Every energy transfer or transformation
increases the entropy (disorder) of the
universe.
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Living systems do not violate the second law of
thermodynamics, which states that entropy increases over time.
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Biological Order and Disorder
• Cells create ordered structures from less ordered
materials.
• Organisms also replace ordered forms of matter and
energy with less ordered forms.
• Energy flows into an ecosystem in the form of light
and exits in the form of heat.
• The evolution of more complex organisms does
not violate the second law of thermodynamics.
• Entropy (disorder) may decrease in an organism,
but the universe’s total entropy increases.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Free-Energy Change, G
https://paul-andersen.squarespace.com/gibbs-free-energy
• The free-energy change of a reaction tells us
whether or not the reaction occurs spontaneously.
• Biologists often want to know which reactions
occur spontaneously and which require input of
energy.
• To do so, they need to determine energy changes
that occur in chemical reactions.
• A living system’s free energy is energy that can
do work when temperature and pressure are
uniform, as in a living cell.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Free-Energy Change, G
• The change in free energy (∆G) during a process
is related to the change in enthalpy, or change in
total energy (∆H), change in entropy (∆S), and
temperature in Kelvin (T):
∆G = ∆H – T∆S
• Only processes with a negative ∆G are
spontaneous.
• Spontaneous processes can be harnessed to
perform work.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Free Energy, Stability, and Equilibrium
• Free energy is a measure of a system’s instability,
its tendency to change to a more stable state.
• During a spontaneous change, free energy
decreases and the stability of a system increases.
• Equilibrium is a state of maximum stability.
• A process is spontaneous and can perform work
only when it is moving toward equilibrium.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• More free energy (higher G)
• Less stable
• Greater work capacity
In a spontaneous change
• The free energy of the system
decreases (∆G < 0)
• The system becomes more
stable
• The released free energy can
be harnessed to do work
• Less free energy (lower G)
• More stable
• Less work capacity
(a) Gravitational motion
(b) Diffusion
(c) Chemical reaction
Free Energy and Metabolism
• The concept of free energy can be applied to the
chemistry of life’s processes:
– An exergonic reaction proceeds with a net
release of free energy and is spontaneous (∆G
is negative).
– An endergonic reaction absorbs free energy
from its surroundings and is nonspontaneous
(∆G is positive).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Reactants
Free energy
Amount of
energy
released
(∆G < 0)
Energy
Products
Progress of the reaction
(a) Exergonic reaction: energy released
Free energy
Products
Amount of
energy
required
(∆G > 0)
Energy
Reactants
Progress of the reaction
(b) Endergonic reaction: energy required
∆G < 0
∆G = 0
(a) An isolated hydroelectric system
(b) An open hydroelectric
system
∆G < 0
∆G < 0
∆G < 0
∆G < 0
(c) A multistep open hydroelectric system
ATP & Energy Coupling
https://www.youtube.com/watch?v=AhuqXwvFv2E
H2O
Energetically favorable exergonic reactions, such as ATPADP, that
have negative change in free energy can be used to maintain or
increase order in a system by being coupled with reactions that have
a positive free energy exchange.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Structure of ATP
•
The bonds between the phosphate groups of ATP’s tail can be broken
by hydrolysis
•
Energy is released from ATP when the terminal phosphate bond is
broken
•
This release of energy comes from the chemical change to a state of
lower free energy, not from the phosphate bonds themselves
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
NH2
Glu
Glutamic
acid
NH3
+
Glu
∆G = +3.4 kcal/mol
Glutamine
Ammonia
(a) Endergonic reaction
1 ATP phosphorylates
glutamic acid,
making the amino
acid less stable.
P
+
Glu
ATP
Glu
+ ADP
NH2
2 Ammonia displaces
the phosphate group,
forming glutamine.
P
Glu
+
NH3
Glu
+ Pi
(b) Coupled with ATP hydrolysis, an exergonic reaction
(c) Overall free-energy change
Membrane protein
P
Solute
Pi
Solute transported
(a) Transport work: ATP phosphorylates
transport proteins
ADP
+
ATP
Pi
Vesicle
Cytoskeletal track
ATP
Motor protein
Protein moved
(b) Mechanical work: ATP binds noncovalently
to motor proteins, then is hydrolyzed
Energy-related pathways in biological systems are sequential
and may be entered at multiple points in the pathway.
• Illustrative Examples include:
– Glycolysis
– Krebs cycle
– Calvin cycle
– Fermentation
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Organisms use free energy to maintain organization,
grow and reproduce.
• Demonstrated understanding includes a
knowledge of:
– Strategies to regulate body temperature
– Strategies for reproduction & rearing of
offspring
– Correlation between metabolic rate and size
– Excess acquired free energy (storage/growth)
– Insufficient acquired free energy (death)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Bioenergetics of Animals
• Animals use the chemical energy in food to sustain
form and function.
• All organisms require chemical energy for growth,
repair, physiological processes, regulation, and
reproduction.
• The flow of energy through an animal, its
bioenergetics, ultimately limits the animal’s behavior,
growth, and reproduction – which determines how
much food it needs.
• Studying an animal’s bioenergetics tells us a great
deal about the animal’s adaptations.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Bioenergetics of an Animal
Quantifying Energy Use
• An animal’s metabolic rate is the amount of energy it uses
in a unit of time.
• An animal’s metabolic rate is closely related to its
bioenergetic strategy – which determines nutritional
needs and is related to an animal’s size, activity, and
environment:
–
The basal metabolic rate (BMR) is the metabolic rate of a nongrowing, unstressed endotherm at rest with an empty stomach.
–
The standard metabolic rate (SMR) is the metabolic rate of a
fasting, non-stressed ectotherm at rest at a particular temperature.
–
For both endotherms and ectotherms, size and activity has a large
effect on metabolic rate.
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Organisms use various strategies to regulate body
temperature and metabolism.
Copyright
Copyright ©
© 2008
2008 Pearson
Pearson Education,
Education, Inc.,
Inc., publishing
publishing as
as Pearson
Pearson Benjamin
Benjamin Cummings
Cummings
Elevated Floral Temperature in Some Plant Species
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Different organisms use various reproductive strategies
in response to energy availability.
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Seasonal Reproduction in Plants
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Metabolic Rate and Size of Organisms
• There is a relationship between metabolic rate per
unit body mass and the size of multicellular
organisms – generally, the smaller the organism,
the higher the metabolic rate.
• Larger animals have more body mass and
therefore require more chemical energy.
• Remarkably, the relationship between overall
metabolic rate and body mass is constant across
a wide range of sizes and forms.
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Metabolic Rate and Size of Organisms
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Changes in free energy availability can result in changes in
population size and disruption to an ecosystem.
• For example, a change in the producer level can affect the
number and size of other trophic levels.
• A change in energy resource levels such as sunlight can
affect the number and size of the trophic levels.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
BIG IDEA II
Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.A
Growth, reproduction and maintenance of the organization
of living systems require free energy and matter.
Essential Knowledge 2.A.2
Organisms capture and store free energy for use in biological processes.
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.A.2: Organisms capture and
store free energy for use in biological processes.
• Learning Objectives:
– (2.4) The student is able to use representations to
pose scientific questions about what mechanisms
and structural features allow organisms to capture,
store and use free energy.
– (2.5) The student is able to construct explanations of
the mechanisms and structural features of cells that
allow organisms to capture, store or use free energy.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Autotrophs capture free energy from physical
sources in the environment.
• Photosynthetic organisms capture free energy
present in sunlight.
–
6CO2 + 6 H2O + light energy  C6H12O6 + 6 O2 + 6 H2O
–
carbon dioxide + water + light energy  sugar + oxygen + water
• Chemosynthetic organisms capture free energy
from small inorganic molecules present in their
environment, and this process can occur in the
absence of oxygen.
–
6H2S + 6 H2O + 6 CO2 + 6 O2  C6H12O6 + 6 H2SO4
–
hydrogen sulfide + water + carbon dioxide + oxygen  sugar + sulfuric acid
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Photosynthesis and Chemosynthesis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Heterotrophs capture free energy present in
carbon compounds produced by other organisms.
• Heterotrophs may metabolize carbohydrates,
lipids and proteins by hydrolysis as sources of free
energy.
–
C6H12O6 + 6 O2  6CO2 + 6 H2O + energy (ATP + heat)
–
organic compounds + oxygen  carbon dioxide + water + energy
• Fermentation produces organic molecules,
including alcohol and lactic acid, and it occurs in
the absence of oxygen.
–
C6H12O6  yeast  2 CH3CH2OH + 2 CO2 + heat
–
sugar  yeast  ethanol + carbon dioxide + heat
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Respiration and Fermentation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Different energy-capturing processes use different
types of electron acceptors.
• An electron acceptor is a chemical entity that
accepts electrons transferred to it from another compound.
• It is an oxidizing agent that, by virtue of its accepting
electrons, is itself reduced in the process.
–
For example, NADP+ in photosynthesis
–
For example, oxygen in cellular respiration
• Chemical reactions that transfer electrons between
reactants are called oxidation-reduction reactions, or redox
reactions.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Catabolic Pathways & ATP Production
• Catabolic Pathways yield energy by oxidizing organic fuels.
• Several processes are central to cellular respiration and
related pathways.
• The breakdown of organic molecules is exergonic:
–
Fermentation is a partial degradation of sugars that occurs
without O2.
–
Aerobic respiration consumes organic molecules and O2
and yields ATP.
–
Anaerobic respiration is similar to aerobic respiration but
consumes compounds other than O2.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cellular respiration in eukaryotes involves a series of coordinated
enzyme-catalyzed reactions that harvest free energy from simple
carbohydrates.
• Cellular respiration includes both aerobic and
anaerobic respiration but is often used to refer to
aerobic respiration.
• Although carbohydrates, fats, and proteins can all
be consumed as fuel, it is helpful to trace cellular
respiration with the sugar glucose:
• C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP + heat)
–
The transfer of electrons during chemical reactions releases
energy stored in organic molecules.
–
This released energy is ultimately used to synthesize ATP.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Oxidation of Organic Fuel Molecules During Cellular
Respiration
• During cellular respiration, the fuel (such as glucose)
is oxidized, and O2 is reduced:
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Stepwise Energy Harvest via NAD+ and the Electron
Transport Chain
• In cellular respiration, glucose and other organic molecules
are broken down in a series of steps.
–
Electrons from organic compounds are usually first
transferred to NAD+, a coenzyme.
–
As an electron acceptor, NAD+ functions as an oxidizing
agent during cellular respiration.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Stages of Cellular Respiration: A Preview
• WATCH IT!
http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.html
• Cellular respiration has three MAIN stages:
– Glycolysis (breaks down glucose into two molecules of
pyruvate) – occurs in cytosol.
– The citric acid cycle (completes the breakdown of
glucose) – occurs in mitochondrial matrix.
– Electron Transport/Oxidative Phosphorylation
(accounts for most of the ATP synthesis) – occurs
across inner membrane of mitochondria.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 9.16 Review: how each molecule of glucose yields many ATP molecules during
cellular respiration:
http://www.wadsworthmedia.com/biology/0495119814_starr/big_picture/ch07_bp.html
Oxidative Phosphorylation
• The process that generates most of the ATP during cellular
respiration is called oxidative phosphorylation because it is
powered by redox reactions of an electron transport chain.
• Oxidative phosphorylation accounts for almost 90% of the ATP
generated by cellular respiration.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Substrate-Level Phosphorylation
• A smaller amount of
ATP is formed in
glycolysis and the citric
acid cycle by
substrate-level
phosphorylation.
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Mitochondrion Structure & Function
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Visual Overview of Cellular Respiration
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Glycolysis rearranges the bonds in glucose molecules, releasing free energy to
form ATP from ADP and inorganic phosphate, and resulting in the
production of pyruvate.
• WATCH IT! http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/anima
tion__how_glycolysis_works.html
• Glycolysis harvests chemical energy by oxidizing glucose
to pyruvate – it is the first stage of cellular respiration.
• This means that glycolysis “splits sugar” into two molecules
of pyruvate.
• Glycolysis occurs in the cytoplasm and has two major
phases:
– Energy investment phase
– Energy payoff phase
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Glycolysis “Need to Know”
•
Glycolysis occurs WITH or WITHOUT oxygen.
•
The first step is the phosphorylation of glucose (glucose
molecule gains 2 inorganic phosphates) – this ACTIVATES the
glucose to split.
•
The second step is the splitting of glucose – breaking it down
into (2) 3-carbon molecules called pyruvic acid.
–
This process is achieved by stripping electrons and
hydrogens from the unstable 3-C molecules (as well as
the borrowed phosphates).
•
2 ATPs are needed to produce 4 ATPs (energy investment and
energy payoff phases).
•
A second product in glycolysis is 2 NADH, which results from
the transfer of e- and H+ to the coenzyme NAD+.
–
Occurs in the cytoplasm
–
Net of 2 ATPs produced
–
2 pyruvic acids formed
–
2 NADH produced
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-8
Energy investment phase
Glucose
2 ADP + 2 P
2 ATP
used
4 ATP
formed
Energy payoff phase
4 ADP + 4 P
2 NAD+ + 4 e– + 4 H+
2 NADH + 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The “Intermediate” Step
• The pyruvate produced during
glycolysis is transported from
the cytoplasm to the
mitochondrion, where further
oxidation occurs.
• The conversion of pyruvate to
acetyl CoA is the junction
between glycolysis (step 1) and
the Krebs cycle (step 2).
• If oxygen is present, Pyruvate
(3 C each) from glycolysis
enters the mitochondrion.
• Using Coenzyme A, each
pyruvate is converted into a
molecule of Acetyl CoA (2 C
each).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-10
CYTOSOL
MITOCHONDRION
NAD+
NADH + H+
2
1
Pyruvate
Transport protein
3
CO2
Coenzyme A
Acetyl CoA
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Citric Acid Cycle
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html
• In the Krebs cycle, carbon dioxide is released from
organic intermediates.
• ATP is synthesized from ADP and inorganic
phosphate via substrate level phosphorylation and
electrons are captured by coenzymes (NAD+ & FAD+).
• The citric acid (Krebs) cycle completes the energyyielding oxidation of organic molecules – and its
events take place within the mitochondrial matrix.
• The cycle oxidizes organic fuel derived from pyruvate,
generating 1 ATP, 3 NADH, and 1 FADH2 per turn.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-11
Pyruvate
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
FADH2
2 CO2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P i
ATP
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Chemiosmosis & Electron Transport
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_1_.html
• Following the Krebs cycle, the electrons captured by
NADH and FADH2 are passed to the electron transport
chain:
–
The electron transport chain uses the high-energy electrons
from the Krebs cycle to convert ADP to ATP.
–
Every time high energy electrons are transported down the
ETC, their energy is used to transport H+ across the inner
membrane of the mitochondria…this creates a (+) charge
on the inside of the membrane and a (–) charge in the
matrix of the mitochondria.
–
As a result of this charge difference, H+ ions escape
through channel proteins called ATP synthase causing it to
rotate.
–
Each time it rotates, the enzyme ATP synthase grabs a low
energy ADP and attaches a phosphate, forming highenergy ATP.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
NADH
50
2 e–
NAD+
FADH2
2 e–
40

FMN
FAD
Multiprotein
complexes
FAD
Fe•S 
Fe•S
Q

Cyt b
30
Fe•S
Cyt c1
I
V
Cyt c
Cyt a
Cyt a3
20
10
2 e–
(from NADH
or FADH2)
0
2 H+ + 1/2 O2
H2O
•
The electron transport chain captures free energy from electrons in a series of coupled reactions that
establish an electrochemical gradient across membranes.
•
Electrons delivered by NADH and FADH2 are passed to a series of electron acceptors as they move toward
the terminal electron acceptor, oxygen.
•
The passage of electrons is accompanied by the formation of a proton gradient (a type of electrochemical
gradient) across the inner mitochondrial membrane, with the membrane separating a region of high proton
concentration from a region of low proton concentration.
•
The flow of protons back through membrane-bound ATP synthase by chemiosmosis generates ATP from
ADP and inorganic phosphate (Pi).
Fig. 9-14
INTERMEMBRANE SPACE
H+
Stator
Rotor
Internal
rod
Catalytic
knob
ADP
+
P
i
ATP
MITOCHONDRIAL MATRIX
Fig. 9-16
H+
H+
H+
H+
Protein complex
of electron
carriers
Cyt c
V
Q


ATP
synthase

FADH2
NADH
2 H+ + 1/2O2
H2O
FAD
NAD+
ADP + P i
(carrying electrons
from food)
ATP
H+
1 Electron transport chain
Oxidative phosphorylation
2 Chemiosmosis
Fig. 9-17
Electron shuttles
span membrane
CYTOSOL
2 NADH
Glycolysis
Glucose
2
Pyruvate
MITOCHONDRION
2 NADH
or
2 FADH2
6 NADH
2 NADH
2
Acetyl
CoA
+ 2 ATP
Citric
acid
cycle
+ 2 ATP
Maximum per glucose:
About
36 or 38 ATP
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
Fermentation/Anaerobic Respiration
• Fermentation and anaerobic respiration enable cells to
produce ATP without the use of oxygen
•
Most cellular respiration requires O2 to produce ATP
• Glycolysis can produce ATP with or without O2 (in aerobic
or anaerobic conditions)
• In the absence of O2, glycolysis couples with fermentation
or anaerobic respiration to produce ATP
–
Anaerobic respiration uses an electron transport chain with
an electron acceptor other than O2, for example sulfate
–
Fermentation uses phosphorylation instead of an electron
transport chain to generate ATP
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-18
2 ADP + 2 Pi
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD+
2 NADH
+ 2 H+
2 CO2
2 Acetaldehyde
2 Ethanol
(a) Alcohol fermentation
2 ADP + 2 Pi
Glucose
2 ATP
Glycolysis
2 NAD+
2 NADH
+ 2 H+
2 Pyruvate
2 Lactate
(b) Lactic acid fermentation
Fermentation and Aerobic Respiration Compared
• Both processes use glycolysis to oxidize glucose
and other organic fuels to pyruvate.
• The processes have different final electron
acceptors: an organic molecule (such as pyruvate
or acetaldehyde) in fermentation and O2 in cellular
respiration.
• Cellular respiration produces 38 ATP per glucose
molecule; fermentation produces 2 ATP per
glucose molecule.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Anaerobes
• Obligate anaerobes carry out fermentation or
anaerobic respiration and cannot survive in the
presence of O2.
• Yeast and many bacteria are facultative
anaerobes, meaning that they can survive using
either fermentation or cellular respiration:
– In a facultative anaerobe, pyruvate is a fork in
the metabolic road that leads to two alternative
catabolic routes.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-19
Glucose
CYTOSOL
Glycolysis
Pyruvate
No O2 present:
Fermentation
O2 present:
Aerobic cellular
respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
The Versatility of Catabolism
• Glycolysis and the citric acid cycle are major
intersections to various catabolic and anabolic
pathways.
• Catabolic pathways funnel electrons from many
kinds of organic molecules into cellular respiration.
• Glycolysis accepts a wide range of carbohydrates.
• In addition to carbohydrates, heterotrophs may
metabolize lipids and proteins by hydrolysis as
sources of free energy.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-20
Proteins
Amino
acids
Carbohydrates
Sugars
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
Fats
Glycerol
Fatty
acids
Fig. 9-21
Glucose
AMP
Glycolysis
Fructose-6-phosphate
–
Stimulates
+
Phosphofructokinase
–
Fructose-1,6-bisphosphate
Inhibits
Inhibits
Pyruvate
ATP
Citrate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation
Energy Coupling
H2O
Following cellular respiration or fermentation, free energy becomes
available for metabolism by the conversion of ATPADP, which is coupled
to many steps in metabolic pathways.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Photosynthesis is the process whereby light energy is converted to
chemical energy and carbon is fixed into organic compounds.
• In the presence of light, plants transform carbon dioxide and
water into carbohydrates and release oxygen:
–
Photosynthesis uses the energy of sunlight to convert water
and CO2 into O2 and high energy sugars
–
6 CO2 + 6 H2O + light → C6H12O6 + 6 O2
–
carbon dioxide + water + light → sugar + oxygen
• Plants then use the sugars to produce complex carbohydrates
such as starches:
–
Plants obtain carbon dioxide from the air or water in which they
grow.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Inside a Chloroplast
Photosynthetic Pigments
•
Photosynthetic pigments absorb light energy and use it to provide energy to
carry out photosynthesis.
–
–
Chlorophylls (absorb light in the red, blue, and violet range):
•
Chlorophyll a - directly involved in transformation of photons to chemical
energy
•
Chlorophyll b - helps trap other wavelengths and transfers it to chlorophyll
a
Carotenoids (absorb light in the blue, green, and violet range):
•
xanthophyll - Yellow
•
beta carotene - Orange
•
Phycobilins – Red
–
Chlorophyll b, the carotenoids, and the phycobilins are known as ANTENNA
PIGMENTS – they capture light in other wavelengths and pass the energy
along to chlorphyll a.
–
Chlorophyll a is the pigment that participates directly in the light
reactions of photosynthesis!
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
During photosynthesis, chlorophylls absorb free energy from light,
boosting electrons to a higher energy level in photosystems I and II.
Different types of organisms use different
photosynthetic pigments to harvest energy.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 10.9 Location and structure of chlorophyll molecules in plants
The pigment molecules have a
large head section that is
exposed to light in the surface of
the membrane; the hydrocarbon
tail anchors the pigment
molecules into the lipid bilayer.
Photosystems
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Stages of Photosynthesis
•
The reaction that occurs during photosynthesis can be
broken into 2 stages:
1.
2.
Light Dependent Reactions
•
Take place within the thylakoid membranes inside a
chloroplast
•
“PHOTO” phase – make ATP & NADPH…USE LIGHT
ENERGY TO PRODUCE ATP & NADPH
Light Independent Reactions (Calvin Cycle)
•
Take place in the stroma of the chloroplast
•
“SYNTHESIS” phase – coverts CO2 to sugar…PRODUCE
SUGAR
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Light Reactions:
-carried out by molecules in thylakoid
membranes
-convert light E to chemical E of ATP and
NADPH
-split H2O and release O2 to the atmosphere
Calvin Cycle Reactions:
-take place in stroma
-use ATP and NADPH to convert CO2
into the sugar G3P
-return ADP, inorganic phosphate, and
NADP+ to the light reactions
Light Dependent Reactions - Overview
• The light-dependent reactions of photosynthesis in
eukaryotes involve a series of coordinated reaction
pathways that capture free energy present in light to
yield ATP and NADPH, which power the production of
organic molecules in the Calvin cycle (dark reactions).
–
require presence of light
–
occur in thylakoids of chloroplasts
–
use energy from light to produce ATP and NADPH (a
temporary, mobile energy source that helps store even more
energy)
–
water is split during the process to replace electrons lost from
excited chlorophyll
–
oxygen gas is produced as a by-product
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Light Independent Reactions - Overview
• The energy captured in the light reactions as
ATP and NADPH powers the production of
carbohydrates from carbon dioxide in the Calvin
cycle.
– do not require light directly – so also known as the
Dark Reactions or the Calvin Cycle
– take place in the stroma of chloroplasts
– ATP and NADPH produced during light dependent
reactions are used to make glucose
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
LIGHT REACTIONS:
How electron flow during the light reactions generates ATP and NADPH
Figure 8-10 Light-Dependent
Reactions
Section 8-3
Go to
Section:
Figure 10.15 Comparison of chemiosmosis in mitochondria and chloroplasts
http://bcs.whfreeman.com/thelifewire/content/chp08/0802002.html
The Dark Reactions (Calvin cycle)
• Calvin cycle can be divided into 3 phases:
– Phase 1: Carbon Fixation
– Phase 2: Reduction
– Phase 3: Regeneration of CO2 Acceptor (RuBP)
• REMEMBER: The Calvin cycle is an ANABOLIC
process – and therefore requires ENERGY – this
energy is provided by the ATP and NADPH made
during the light reactions!!!
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 10.17 The Calvin Cycle
BIG IDEA II
Biological systems utilize free energy and molecular building blocks
to grow, to reproduce and to maintain dynamic homeostasis.
Enduring Understanding 2.A
Growth, reproduction and maintenance of the organization
of living systems require free energy and matter.
Essential Knowledge 2.A.3
Organisms must exchange matter with the environment
to grow, reproduce and maintain organization.
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Essential Knowledge 2.A.3: Organisms must exchange matter
with the environment to grow, reproduce and maintain organization.
• Learning Objectives:
–
(2.6) The student is able to use calculated surface area-to-volume
ratios to predict which cell(s) might eliminate wastes or procure
nutrients faster by diffusion.
–
(2.7) The student is able to explain how cell size and shape affect
the overall rate of nutrient intake and the rate of waste elimination.
–
(2.8) The student is able to justify the selection of data regarding
the types of molecules that an animal, plant or bacterium will take up
as necessary building blocks and excrete as waste products.
–
(2.9) The student is able to represent graphically or model
quantitatively the exchange of molecules between an organism and
its environment, and the subsequent use of these molecules to build
new molecules that facilitate dynamic homeostasis, growth and
reproduction.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Molecules and atoms from the environment are
necessary to build new molecules.
• Carbon moves from the environment to organisms
where it is used to build carbohydrates, proteins,
lipids or nucleic acids. Carbon is used in storage
compounds and cell formation in all organisms.
• Nitrogen moves from the environment to
organisms where it is used in building proteins and
nucleic acids.
• Phosphorus moves from the environment to
organisms where it is used in nucleic acids and
certain lipids.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Biological and geochemical processes cycle nutrients between
organic and inorganic parts of an ecosystem.
• Life depends on recycling chemical elements.
• Nutrient circuits in ecosystems involve biotic and
abiotic components and are often called
biogeochemical cycles:
– Gaseous carbon, oxygen, sulfur, and nitrogen
occur in the atmosphere and cycle globally.
– Less mobile elements such as phosphorus,
potassium, and calcium cycle on a more local
level.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-13
Reservoir A
Reservoir B
Organic
materials
available
as nutrients
Organic
materials
unavailable
as nutrients
Fossilization
Living
organisms,
detritus
Assimilation,
photosynthesis
Coal, oil,
peat
Respiration,
decomposition,
excretion
Burning
of fossil fuels
Reservoir C
Reservoir D
Inorganic
materials
available
as nutrients
Inorganic
materials
unavailable
as nutrients
Atmosphere,
soil, water
Weathering,
erosion
Formation of
sedimentary rock
Minerals
in rocks
Biogeochemical Cycles
• In studying cycling of water, carbon, nitrogen, and
phosphorus, ecologists focus on four factors:
– Each chemical’s biological importance
– Forms in which each chemical is available or
used by organisms
– Major reservoirs for each chemical
– Key processes driving movement of each
chemical through its cycle
– How humans are impacting each cycle
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-14a
Transport
over land
Solar energy
Net movement of
water vapor by wind
Precipitation Evaporation
over ocean
from ocean
Precipitation
over land
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
Fig. 55-14b
CO2 in atmosphere
Photosynthesis
Photosynthesis
Cellular
respiration
Burning of
fossil fuels Phytoand wood plankton
Higher-level
consumers
Primary
consumers
Carbon compounds
in water
Detritus
Decomposition
Fig. 55-14c
N2 in atmosphere
Assimilation
NO3–
Nitrogen-fixing
bacteria
Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
Nitrification
NH4+
NO2–
Nitrifying
bacteria
Denitrifying
bacteria
Nitrifying
bacteria
Fig. 55-14d
Precipitation
Geologic
uplift
Weathering
of rocks
Runoff
Consumption
Decomposition
Plant
uptake
of PO43–
Plankton Dissolved PO43–
Uptake
Sedimentation
Soil
Leaching
Decomposition and Nutrient Cycling Rates
• Decomposers (detritivores) play a key role in the
general pattern of chemical cycling.
• Rates at which nutrients cycle in different
ecosystems vary greatly, mostly as a result of
differing rates of decomposition.
• The rate of decomposition is controlled by
temperature, moisture, and nutrient availability.
• Rapid decomposition results in relatively low
levels of nutrients in the soil.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Ecosystem type
EXPERIMENT
Arctic
Subarctic
Boreal
Temperate
Grassland
A
Mountain
G
M
T
P
E,F
N
U
D
B,C
H,I
S
O
L
J
K
R
Q
RESULTS
80
Percent of mass lost
Fig. 55-15
70
60
K
J
50
40
D
30
20
C
A
10
0
–15
–10
BE
F
G
P
N
M
L
I
U
R
O Q
T
S
H
–5
0
5
10
Mean annual temperature (ºC)
15
Fig. 55-16
(a) Concrete dam
and weir
Nitrate concentration in runoff
(mg/L)
(b) Clear-cut watershed
80
60
40
20
4
3
2
1
0
Deforested
Completion of
tree cutting
1965
Control
1966
(c) Nitrogen in runoff from watersheds
1967
1968
Human activities now dominate most chemical cycles
on Earth.
• As the human population has grown, our activities
have disrupted the trophic structure, energy flow,
and chemical cycling of many ecosystems
• In addition to transporting nutrients from one
location to another, humans have added new
materials, some of them toxins, to ecosystems
• Disruptions that deplete nutrients in one area and
increase them in other areas can be detrimental
to ecosystem dynamics.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-17: Agriculture & Nitrogen Cycling
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Algae Blooms & Eutrophication
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Role of Matter in Living Organisms
Experiments were carried out to determine the
plant’s photosynthetic capacity by measuring the
net uptake of carbon dioxide and changes in tissue
starch concentration over a 32-hour period with 8
hours of dark at the start and end of the
measurement period and 16 hours of moderate
light between the two dark periods.
Epiphytic Plant from Rain Forest Canopy
The changes in the rate of carbon dioxide uptake
and the concentration of tissue starch are shown
graph.
•
What is an appropriate title for this graph?
•
What was the IV of this experiment? The DV?
•
What variables should have been controlled during this experiment?
•
The photosynthetic pattern of this plant species is unusual. Explain.
•
A useful control for the experiment would have included what?
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Living systems depend on properties of water that
result from its polarity and hydrogen bonding.
•
Four of water’s properties that facilitate an
environment for life are:
–
Cohesive/Adhesive behavior
–
Ability to moderate temperature
–
Expansion upon freezing
–
Versatility as a solvent
–
http://www.sumanasinc.com/webcontent/anim
ations/content/propertiesofwater/water.html
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The polarity of water molecules results in hydrogen
bonding.
• The water molecule is a polar
molecule: The opposite ends
have opposite charges
• Polarity allows water
molecules to form hydrogen
bonds with each other
– Water is polar because the
oxygen atom has a stronger
electronegative pull on
shared electrons in the
molecule than do the
hydrogen atoms
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cohesion & Adhesion
• Collectively, hydrogen bonds hold water
molecules together, a phenomenon called
cohesion
–
the attraction of water molecules to other water molecules as a
result of hydrogen bonding
–
Cohesion due to hydrogen bonding contributes to the transport of
water and dissolved nutrients against gravity in plants
• Adhesion is the clinging of one substance to
another
–
Adhesion of water to cell walls by hydrogen bonds helps to counter
the downward pull of gravity on the liquids passing through plants
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 3-3
Adhesion
Water-conducting
cells
Direction
of water
movement
Cohesion
150 µm
Cohesion and adhesion work
together to give capillarity – the
ability of water to spread through fine
pores or to move upward through
narrow tubes against the force of
gravity.
Moderation of Temperature
• Water moderates air temperature by absorbing
heat from air that is warmer and releasing the
stored heat to air that is cooler
• Water can absorb or release a large amount of
heat with only a slight change in its own
temperature
• The ability of water to stabilize temperature stems
from its relatively high specific heat
– This is the amount of heat that must be absorbed or lost
for 1g of a substance to change its temperature by 1°C
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Water’s High Specific Heat
• Water’s high specific heat can be traced to hydrogen
bonding
– Heat is absorbed when hydrogen bonds break
– Heat is released when hydrogen bonds form
• High specific heat of water is due to hydrogen bonding –
H-bonds tend to restrict molecular movement, so when
we add heat energy to water, it must break bonds first
rather than increase molecular motion.
– A greater input of energy is required to raise the
temperature of water than the temperature of air!
– Minimizes temperature fluctuations to within limits that
permit life
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Evaporative Cooling
• Evaporation is transformation of a substance from
liquid to gas
• Heat of vaporization is the heat a liquid must
absorb for 1 g to be converted to gas
• As a liquid evaporates, its remaining surface
cools, a process called evaporative cooling
• The high amount of energy required to vaporize
water has a wide range of effects:
– Helps stabilize temperatures in organisms and
bodies of water
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 3-6
Insulation of Bodies of Water by Floating Ice
Hydrogen
bond
Ice
Hydrogen bonds are stable
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Liquid water
Hydrogen bonds break and re-form
The Solvent of Life
• A solution is a liquid that is a homogeneous
mixture of substances
– Solvent (dissolving agent)
– Solute (substance that is dissolved)
• An aqueous solution is one in which water is the
solvent
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Hydration Shell
http://www.sumanasinc.com/webcontent/animations/content/propertiesofwater/water.html
• A hydration shell refers to the sphere of water
molecules around each dissolved ion in an
aqueous solution
– Water will work inward from the surface of the
solute until it dissolves all of it (provided that
the solute is soluble in water)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Threats to Water Quality on Earth
• Acid precipitation refers to rain, snow, or fog with
a pH lower than 5.6.
• Acid precipitation is caused mainly by the mixing
of different pollutants with water in the air and can
fall at some distance from the source of pollutants.
• Acid precipitation can damage life in lakes and
streams.
• Effects of acid precipitation on soil chemistry are
contributing to the decline of some forests.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 3-10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
More
acidic
Acid
rain
Normal
rain
More
basic
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Threats to Water Quality on Earth
• Human activities such as burning fossil fuels
threaten water quality
• CO2 is released by fossil fuel combustion and
contributes to:
– A warming of earth called the “greenhouse”
effect
– This can cause acidification of the oceans;
leads to a decrease in the ability of corals to
form calcified reefs
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 3-11
EXPERIMENT
RESULTS
40
20
0
150
250
200
[CO32–] (µmol/kg)
300
Surface area-to-volume ratios affect a biological system’s ability to
obtain necessary resources or eliminate waste products.
• As cells increase in volume, the relative surface area
decreases and demand for material resources increases;
more cellular structures are necessary to adequately
exchange materials and energy with the environment.
• As the surface area increases by a factor of n2, the volume
increases by a factor of n3 - small cells have a greater surface
area relative to volume.
• These limitations restrict cell size. Illustrative examples
include:
–
Root hairs
–
Cells of the alveoli
–
Microvilli
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-8: Limits to Cell Size
Surface area increases while
total volume remains constant
5
1
1
Total surface area
[Sum of the surface areas
(height  width) of all boxes
sides  number of boxes]
Total volume
[height  width  length 
number of boxes]
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume]
6
150
750
1
125
125
6
1.2
6
Root Hairs
•
An increased surface area to volume
ratio means increased exposure to
the environment. The higher the
SA:Volume ratio for a cell, the more
effective the process of diffusion.
•
Root hairs are long, thin hair-like
cells that emerge from the root tip to
form an important surface over which
plants absorb most of their water and
nutrients via diffusion.
•
They present a large surface area to
the surrounding soil, which makes
absorbing both water and minerals
more efficient using osmosis.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cells of the Alveoli
•
The ratio between the surface area
and volume of cells and organisms
has an enormous impact on their
biology. Individual organs in animals
are often shaped by requirements of
surface area to volume ratio.
•
The numerous internal branchings of
the lung and alveoli increase the
surface area through which oxygen is
passed into the blood and carbon
dioxide is released from the blood.
•
Human lungs contain millions of
alveoli, which together have a
surface area of about 100m2, fifty
times that of the skin.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Microvilli & Other Cell Types
•
Large animals require specialized organs
(lungs, kidneys, intestines, etc.) that
effectively increase the surface area
available for exchange processes, and a
circulatory system to move material and heat
energy between the surface and the core of
the organism.
•
The intestine has a finely wrinkled internal
surface, increasing the area through which
nutrients are absorbed by the body.
•
A wide and thin cell, such as a nerve cell, or
one with membrane protrusions such as
microvilli has a greater surface-area-tovolume ratio than a spheroidal one.
•
Likewise a worm has proportionately more
surface area than a rounder organism of the
same mass does.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Plasma Membrane
• The surface area of the plasma membrane must be large
enough to adequately exchange materials;
• Smaller cells have a more favorable surface area-tovolume ratio for exchange of materials with the
environment.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings