Download Animal Energetics II PPT

Allometry
The Problem of Size & Scaling
Get it??? “A – LLAMA – TREE”
Allometry

How does body size affect physiological
function?
◦
◦
◦
◦

8,000 species of birds
8,000 species of mammals
20,000 species of fish
>2,000 species of reptiles/amphibians
Great Differences in Size
Allometry

Mammals:
Etruscan Shew (2.5g)  Blue Whale (120 tons)
Allometry

Birds:
Humming bird (2.0g)  Ostrich (100kg)
Allometry

Can we study one end of the continuum
and know something about the other end?

Are there structural and/or functional
consequences of changes in size scale in
similar organisms?
Metabolic Rate & Body Size
Animal
Body Mass
(kg)
Total VO2
(LO2/hr)
Shrew
0.0048
0.036
Dog
11.7
3.9
Elephant
3833
268
Metabolic Rate & Body Size
Semi-Log Plot
ELEPHANT
y = a*massb
VO2
SHREW
DOG
Log Body Mass
Metabolic Rate & Body Size

y = a*massb
◦ y = physiological variable of interest
◦ a = intercept
◦ b = mass exponent
 Tells us something about the shape of the
relationship (slope of line).
Metabolic Rate & Body Size

To transform everything into log-log:

Log y = Log a + b(log mass)
Metabolic Rate & Body Size
Log-Log Plot
y = a*massb
Log VO2
DOG
SHREW
Log Body Mass
ELEPHANT
Metabolic Rate & Body Size

Fundamental debate as to what the
scaling exponent b is.

Originally thought to be 2/3rds
◦ Max Rubner 1880s

In 1932 Max Kliber concluded BMR
scaled to the 3/4ths power (b=3/4).
Exponent b

y = a*massb
If b is + :
◦ physiological variable  with  body mass

If b is - :
◦ physiological variable  with  body mass

If b is 0:
◦ physiological variable is unaffected by scale
Exponent b
Physiological
Variable
(b = 0)
Log Body Mass
Metabolic Rate & Body Size

Kliber – Mouse to Elephant Curve
Log
VO2 /HR
b= 3/4
Log Body Mass
Mass-Specific Relationships
Animal
Shrew
Dog
Elephant
Body Mass Total VO2
(kg)
(LO2/hr)
0.0048
0.036
11.7
3.9
3833
268
VO2/mass
(LO2/hr*kg)
7.4
0.33
0.07
What seems obvious at the whole animal
level gets turned upside down at the mass
specific tissue level!
Mass-Specific Relationships


Mass specific metabolic rate =
looking at tissue level metabolism
VO2/mass
Mass-Specific Relationships
SHREW
Mass Specific MR
LO2 /HR*kg
DOG
ELEPHANT
Log Body Mass
Mass-Specific Relationships
SHREW
Log Mass Specific MR
LO2 /HR*kg
DOG
ELEPHANT
Log Body Mass
Mass-Specific Relationships

Therefore, we see
that increasing
body size results in
a decrease in
mass specific
metabolic rate.
WHOLE
ANIMAL
Log VO2
MASS
SPECIFIC
Log Body Mass
What does that mean??
Metabolic Rate Across Taxa

What about differences between
taxonomic groups?
Metabolic Rate Across Taxa
Log MR
Similarly sized endotherms will
always have higher BMRs than
their ectotherm counterparts.
Log Body Mass
Metabolic Rate Across Taxa
Log BMR
Log Body Mass
Metabolic Rate Across Taxa

BMR for marine mammals is 2x that of
similarly sized terrestrial mammals

Marsupials have a BMR 30% lower than
you would predict for a terrestrial
mammal.
Metabolic Pathways, Macromolecules, &
High Energy Molecules
Energy Storage

Energy can be stored in different forms:
◦ Gradients
◦ Chemical bonds
Gradients

Molecules tend to disperse or diffuse
randomly within available space.
Diffusion

2 aspects of diffusion govern properties of
many biological systems:
1. Leads to random distribution of molecules,
but rates can be slow.
2. Source of energy that cells can utilize.
Diffusion Gradients

Biological systems can invest energy to
move molecules out of random
distribution, resulting in a diffusion
gradient.

This gradient is a form of energy storage
that the cell can use for other purposes.
Diffusion Gradients

Chemical Gradients

Electrical Gradients

Electrochemical Gradients

FIGURE 2.2
Chemical Bonds

Most biologically available energy is
stored in bonds
◦ Covalent bonds = Strong Bonds.
 Hold individual atoms together and form molecules
by sharing electrons
◦ Non-Covalent bonds = Weak Bonds.
 Organize molecules into 3D structures.
Energy Acquisition

How are organisms able to utilize the
energy stored in chemical bonds?

How are they able to convert the
chemical energy stored in food into
utilizable energy?
Metabolic Pathways
Eat Food
Fragment
Enter Cells
Oxidized thru Biochemical Pathways
Energy, Heat, CO2, and H2O
Metabolic Pathways

Metabolic pathway: Series of
consecutive enzymatic reactions that
catalyze the conversion of substrates to
products

Metabolic flux: flow through a pathway
Metabolic Pathways

Metabolic pathways can be:
◦ Synthetic (Anabolic)
◦ Degradative (Catabolic)
◦ Combination (Amphibolic)

Energy metabolism revolves around the
production of ATP and other energy-rich
molecules.
Enzymes

Enzymes = biological catalysts that aid in
the conversion of substrate to product.
◦ Most are composed of protein

Animals control the inner workings of cells
through the use of enzymes, which
interconvert macromolecules to create
building blocks and control the flow of energy
Enzymes

3 Important properties of enzymes:
◦ Active at very low concentrations within cell
◦ Speed up the rate of reaction without being
altered in the process
◦ Do not change the nature of the products
Enzymes

Enzymes aid in the transfer energy from
nutrients to molecules that function as
energy stores.

These energy rich molecules act as
substrate and product in hundreds of
different metabolic reactions.
Reducing Equivalents

Cells store energy in the form of reducing
equivalents to drive metabolic processes:

NAD+

NADP+ :
:
Nicotinamide adenine
dinucleotide
Nicotinamide adenine
dinucleotide phosphate
Redox Reactions

REDduction-OXidation reactions
◦ Transfer of electrons

Oxidation  loss of electrons
increase in oxidation state

Reduction  gain of electrons
decrease in oxidation state
Redox Reactions

NAD+ is an oxidizing agent.

It accepts electrons from other molecules
and becomes reduced.

NAD+  NADH

NADH can then be used as a reducing
agent to donate electrons.
Reducing Equivalents

In an enzymatic reaction, electrons are
transferred to NAD+ or NADP+

Reduced NADH or NADPH can be used
to drive other reactions.
Redox Status

Measure of how much reducing energy is
stored to drive metabolic reactions

Redox Status =
[NADH]
[NAD+]
High Ratio = cell rich in reducing energy
 Low Ratio = call poor in reducing energy

Reducing Equivalents

Why are they important?

Reducing equivalents are used in
metabolic pathways in order to produce
high energy molecules.
High Energy Molecules

High energy molecules are used as
energy currency by cells:
◦ Adenosine Triphosphate (ATP)
◦ Phosphocreatine (PCR)
◦ Acetyl CoA
High Energy Molecules
Energy Currency

The storage of high energy phosphates
and controlled release of energy is the
mechanism behind metabolism.

ATP = The universal source of
immediate energy in cellular
metabolism.
Adenosine Triphosphate (ATP)
Adenosine Triphosphate (ATP)

Each of the high energy bonds provided
the same amount of energy.

ATP  ADP  AMP

Energy is not stored in the bond, but is
released when the bond is broken.
Adenosine Triphosphate (ATP)
Phosphocreatine (PCR)

PCR is used when ATP
demand temporarily out
strips the capacity to
produce ATP.

Hummingbirds,
greyhounds, and cheetahs
have high levels of PCR
Phosphocreatine (PCR)

Can diffuse easily into areas needing
energy.

When ATP is low, the energy stored in
PCR is transferred to ADP or AMP.
ADP – ATP Cycle
Locomotion, Heart Fxn,
Biosynthesis, Growth, etc.
ATP
ADP
Oxidation of Fuel
Energy Exchange

ATP-ADP cycle is the fundamental
mode of energy exchange in
biological systems.

Recycling is a cyclic process fueled by the
food you eat and oxygen you consume.
Diving Marine Mammals
 ATP
  ADP
  AMP
  PCR


FAST AND CYCLIC PROCESS
Levels Back
to Normal
Types of Fuel

Macromolecules:
◦ Proteins
◦ Carbohydrates
◦ Lipids (fatty acids)
Proteins

Form exoskeletons, extracellular matrices,
& enzymes

Building blocks = amino acids (20)

Long strands of amino acids are folded
into 3D conformations.

The structure of proteins are stabilized by
many weak bonds.
Proteins
Proteins

Environmental conditions such as
temperature can alter weak bonds and
disrupt 3D shape.

When proteins begin to unfold, or
denature, they are no longer capable of
performing their function.

Negatively impacts enzymatic function
and metabolism.
Carbohydrates

Glucose = C6H12O6

Most common carbohydrate in animal diets.

Versatile: cells can break it down for energy,
store it for later consumption, or use it to
build other needed carbohydrates.
Carbohydrates

Polysaccharides = larger polymers of
carbohydrates that serve in energy storage
and structure.

Glycogen = polysaccharide that acts as an
internal energy store.
◦ Broken down for use in glycolysis
◦ Important for endurance
Glycogen Stores
Lipids

Hydrophobic Organic Molecules:
◦ Fatty Acids
◦ Triglycerides
◦ Phospholipids
◦ Steroids
Fatty Acids

The mammalian heart derives more than
70% of its energy from fatty acids.

Fatty acids are long chains of carbon
atoms that end in a carboxyl group.

They can be 2-30 carbons long, and are
either saturated or unsaturated.
Fatty Acids

Saturated F.A. = no double bonds.

Unsaturated F.A. = 1≤ double bonds.
Fatty Acids

Fatty Acids are oxidized in the
mitochondria.

Pairs of carbons are sequentially cut off
the ends of fatty acid chains in the form
of Acetyl CoA.

Cycle repeats itself until the entire fatty
acid chain is broken down.
Fatty Acids

The most abundant energy source
available to the muscle fiber is fat.

The breakdown of fat to yield
ATP is referred to as lipolysis.

The rate at which lipolysis occurs is the
limiting factor in obtaining ATP.
Fatty Acids

Lipolysis is responsible for resting muscle
activity.

Contribution to overall muscle energy
supply decreases as contraction intensity
increases.

Once glycogen depletion occurs, exercise
intensity will be reduced dramatically.
◦ “Hitting The Wall”
Sprinter v. Marathoner
% Fuel Type
60%
FAT
CHO
60-75%
Exercise Intensity
Biochemical Processes

Biochemical pathways can be either:
AEROBIC
ANAEROBIC
Aerobic and Anearobic Metabolism

2 Major Pathways:
◦ Glycolysis (anaerobic) takes place in the
cytosol of a cell
◦ TCA / Krebs Cycle (aerobic) takes place in
the mitochondrial matrix followed by oxidation
by the electron transport system (ETS) in the
inner mitochondrial membrane.
Glycolysis

Low efficiency high velocity pathway. It is
the pathways that breaks down glucose.

Vital source of ATP because it can
proceed in the absence of oxygen
(anoxia) and can produce ATP rapidly,
though for brief periods.
Glycolysis
Glucose + 2ADP + 2NAD+ 
2ATP + 2 Pyruvate + 2 NADH + 2 H+

Negative feedback regulation:
ATP levels = ATP production
Glycolysis

Within the cytoplasm (no oxygen present):
pyruvate + NADH + H+  lactate + NAD+

Regenerates NAD+ for glycolysis

Lactate is slightly toxic.
◦ It can be tolerated for short periods by being
retained in tissues or exported into extracellular
fluid.
◦ Must me metabolized and removed from system.
◦ Associated with muscle fatigue in athletes.
Glycolysis (anaerobic)

So why bother?
◦ FAST!
◦ No Oxygen Needed!

Environmental hypoxia:
◦ Environmental O2 levels fall below critical
levels for prolonged periods.

Functional anoxia:
◦ Tissue O2 demands outstrip O2 delivery
from blood (ex. Exercise/diving animals).
Glycolysis

When oxygen is present, pyruvate is
converted to Acetyl CoA and used in
mitochondrial metabolism.
Mitochondrial Metabolism

Aerobic  uses oxygen

Main point of entry for mitochondrial
energy producing pathway is Acetyl CoA.

Acetyl CoA:
◦ Produced in
many pathways.
Mitochondrial Metabolism

2 Main Processes:

TCA / Krebs Cycle
◦ Occurs in mitochondrial matrix
◦ Produces reducing equivalents used in ETS

Oxidative Phosphorylation
◦ Occurs in Inner mitochondrial membrane
◦ Produces ATP
Mitochondrial Metabolism
TCA / Krebs Cycle

Acetyl CoA is oxidized to form reducing
equivalents:
NADH and FADH2

Provides fuel for mitochondrial ATP
production.
TCA / Krebs Cycle

TCA / Krebs Cycle

For every Acetly CoA that enters cycle:
2 CO2
3 NADH
1 FADH2
1 GTP
… are produced.
Oxidative Phosphorylation

Electron Transport System (ETS)

Phosphorylation
Electron Transport System (ETS)

Mitochondria utilize reducing equivalents
in ETS to aide in ATP production.

ETS maintains an electrochemical gradient
found in the inner mitochondrial
membrane and utilizes it to drive ATP
synthesis.
Electron Transport System (ETS)
Electron Transport System (ETS)

Break down of NADH and FADH2
produces energy used to pump H+ into
outer compartment of the mitochondria
Oxidative Phosphorilation

ATP is generated as H+ moves down its
concentration gradient through a special
enzyme called ATP synthase
Oxidative Phosphorylation
Net Final Score

Oxidative Phosphorylation=
36 mol ATP / mol Glucose
 Efficient but slow

Glycolysis =
2 mol ATP / mol Glucose
 Inefficient but fast
Energy & Metabolism

Cells must produce ATP at rates
that match ATP demand.

There will be different fuels and
pathways utilized depending on the
activity state of an individual
Energy System v. Running Speed

The primary energy source for sprinting
distances up to 400 m is PCr.

From 400 m to 1,500 m, anaerobic
glycolysis is the primary energy source.

Distances longer than 1,500 m, athletes
rely primarily on aerobic metabolism.
http://www.nismat.org/physcor/energy_supply.html
Speed and Distance

With increasing distances, average speeds
decline.

The average speed for the marathon world
record is 12.1 mph, which is 55% of the
world record sprinting speed.

Remarkable since the marathon is more
than 200 times the length of a 200 m race.
http://www.nismat.org/physcor/energy_supply.html