(-) controlo 5 drops RBC suspensiono 5 mL 0.2M NaCl
Glucose (5 mL each test tube)o 0.075, 0.09, 0.1, 0.15, 0.2
M CaCl2 (5 mL each test tube)
o 0.03, 0.035, 0.05, 0.075, 0.09 M
Na2SO4 (5 mL each test tube)o 0.03, 0.035, 0.05, 0.075,
0.09 M KCl (5 mL each test tube)
o 0.025, 0.05, 0.075, 0.1, 0.15 M
NaCl (5 mL each test tube)o 0.025, 0.05, 0.075, 0.1,
0.15 M2. Procedure
Add 5 drops of suspension to each concentration of every solution
Record hemolysis time (complete hemolysis has occurred when the solution appears transparent against a white printed background)
Threshold: 10 minutes Calculate for Isotonic Coefficient (i) and
Degree of Dissociation (a) – see equations in discussion
Effect of Molecular Size on Permeability1. Solutions
RBC suspensiono 7 drops bloodo 5 mL 0.9% NaCl
(+) controlo 5 drops RBC suspensiono 5 mL dH2O
(-) controlo 5 drops RBC suspension
o 5 mL 0.2M NaCl 0.3 M urea 0.3 M glucose 0.3 M ethylene glycol 0.3 M glycerol
2. Procedure Add 2 drops of suspension in each
solution Record hemolysis time Threshold: 10 minutes
Permeability and Partition Coefficients1. Solutions
RBC suspensiono 7 drops bloodo 5 mL 0.9% NaCl
(+) controlo 5 drops RBC suspensiono 5 mL dH2O
(-) controlo 5 drops RBC suspensiono 5 mL 0.2M NaCl
0.6 M methanol 0.6 M ethanol 0.6 M isopropanol 0.6 M n-butanol
2. Procedure Immerse solutions in an ice bath are
take note of temperature Add 2 drops of suspension in each
solution Record hemolysis time Threshold: 10 minutes
Effect of Polar Groups on Permeability1. Solutions
RBC suspensiono 7 drops bloodo 5 mL 0.9% NaCl
(+) controlo 5 drops RBC suspensiono 5 mL dH2O
(-) controlo 5 drops RBC suspensiono 5 mL 0.2M NaCl
0.3 M chloroform 0.3 M hexane 0.3 M ethylene glycol 0.3 M isopropanol
2. Procedure Add 2 drops of suspension in each
solution
1
Record hemolysis time Threshold: 10 minutes
B. DISCUSSION
The Cell Membrane Phospholipid bilayer Outer: hydrophilic heads, inner: hydrophobic
tails Other components: membrane proteins,
other lipids (i.e. cholesterol) Selectively permeable Regulates the passage of materials into and
out of the cello Nutritiono Maintenance of irritability (i.e.
sensitivity to stimuli, fluidity of membrane)
o Homeostasis (milieu intérieur)
Transport Through the Membrane Passive
o Simple diffusion – the net movement of solutes through a selectively permeable membrane from an area of higher energy to an area of lower energy (higher to lower concentration) by random thermal motion
o Facilitated diffusion – assisted by proteins embedded in the membrane but still across a concentration gradient
Channel proteins – provide a path for lipid insoluble molecules to pass through
Carrier proteins – undergo conformational changes to transport solutes
Activeo Occurs against the concentration
gradient and, therefore, requires energy
o This energy is usually provided in the form of adenosine triphosphate (ATP)
Osmosiso Diffusion of water through a
selectively permeable membraneo Water moves according to its own
“concentration gradient”
Osmoticity vs. Tonicity
Osmoticity – refers to the relationship of solutions on opposite sides of an ideal selectively permeable membrane (one that does not allow the entry of any solutes); isosmotic solutions have the same number of particles per liter of solution (osmolarity)
Tonicity – refers to the relationship of solutions separated by a biological membrane (i.e. plasma membrane); refers to the response of a cell or tissue; for example: hypo-, hyper-, or isotonic to the cytosol
Solutions can be isosmotic but not isotonic; for example, 0.3M glucose is (theoretically) isosmotic to intracellular fluid of RBCs but it still caused hemolysis because of the nature of the actual biological membrane (allows solutes through)
Red Blood Cells Often used model for the membrane-solute-
solvent relationship Hemoglobin – pigment in the cell that (aside
from containing oxygen) gives it its characteristic red color
When hemolysis occurs in a hypotonic solution because water rushes into the cell, this pigment spreads through the solution, giving it a clearer appearance
Isotonic Coefficient
i=CNE
CE
=H NE
H E
where: CNE is the concentration of the NE that caused hemolysis within 10 minutes, CE is the
highest concentration of an E that caused hemolysis within 10 minutes
Characteristic of an electrolyte relative to a non-electrolyte: concentration of an electrolyte that exerts an equal amount of osmotic pressure as a non-electrolyte
Assume the osmotic activity is directly related to hemolytic point (therefore, HNE
and HE are equal to the NE’s and E’s concentrations, respectively)
The value implies that the given concentration of electrolyte exerts i times as much osmotic pressure as the given concentration of the non-electrolyte
A non-electrolyte’s i is equal to 1, therefore:o i close to 1 = strong electrolyte
2
o i < 1, close to 0 = weak electrolyte
Degree of Dissociation
a= i−1k−1
where: i is the isotonic coefficient and k is the number of ions that the E dissociates into in
solution
the fraction of the solute molecules that dissociates in solution
related to the tendency of an electrolyte to dissociate in solution
generally (and logically), bigger molecules take longer to diffuse into a membrane—there is a direct (positive) relationship between molecular size and time of hemolysis
Partition Coefficients and Permeabilty
SolutePartition Coefficient
(k)Methanol 0.14Ethanol 0.26
Isopropanol 0.64n-Butanol 7.7
A partition coefficient measures hydrophobicity in that it is the ratio of a molecule’s solubility in a lipid and the same molecule’s solubility in water
Overton’s Rule states that higher hydrophobicity relates to higher permeability; there is a positive relationship between the partition coefficient and time of hemolysis
Non-polar compounds tend to have higher solubility in water and (way) lower solubility in water and, therefore, higher partition coefficients; molecules with longer carbon chains permeate the membrane more easily than molecules with shorter carbon chains
Because of the hydrophobic nature of a bulk of the cell membrane, substances with higher partition coefficients diffuse more quickly through the membrane
Polarity and Permeability
Solute Dielectric ConstantChloroform 4.81
Hexane 2.0Ethylene Glycol 37.0
Isopropanol 17.9
There is a positive relationship between polarity and hemolysis time in that more polar molecules less easily penetrate the cell membrane
This is due in part to the membrane’s composition (hydrophilic heads, hydrophobic tails) and due to its slight electrical potential—polar molecules have a separation of charges that affect the rate of their uptake by the cell
3
II. ACTIVITY OF SALIVARY AMYLASE
A. EXPERIMENT PROPER
Determination of Achromic Point1. Solutions
Salivary amylase dilutiono Saliva was collected after
stimulation of salivary glands through the mastication of paraffin wax
o Saliva was filtered through cheese cloth then diluted to 10 mL then filtered again through filter paper
1% Cooked Starch solutiono 5 g starch suspended in 50
mL d H2O then slowly dissolved with 450 mL boiling water
o Stirred and heated until translucent
Iodine-Potassium Iodide solution (IKI)
o 6 g KIo 4 g iodine crystalso 100 mL d H2O
1% NaCl solution 0.2 M Na2HPO4 (for McIlvaine’s
solutions) 0.1 M citric acid Phosphate buffer, pH 6.8 Digestive mixture (maintained at 38
℃)o 5 mL starcho 2 mL 1% NaClo 2 mL phosphate buffer, pH
6.8o 1 mL salivary dilution
2. Procedure 1 mL of the salivary dilution was added
to the prepared digestive mixture once it reached 38℃ and the time of addition was recorded
Temperature was kept constant by placing the test tube in a water bath
At minute intervals, a drop of the dilution was added to a spot plate with 1 drop of IKI and color change was observed
If no color change was observed within 2-10 minutes, the number of amylase
units and enzyme activity in the saliva were computed
Note: 1% starch contains 50 mg starch
5mL starchsol ' n×0.01 gstarchmLsol ' n
×1000mg1g
Effect of Enzyme Concentration The procedures for determining achromic
point, amylase units, and enzyme activity were performed for 6 different salivary dilutions
Enzyme activity vs. Enzyme concentration was graphed
Effect of Substrate Concentration The procedures for determining achromic
point, amylase units, and enzyme activity were performed with the [S] of the 5 mL starch in the digestive mixture varying from 1% to 6% (use MW of starch 3 x 104 Da to compute for concentration of solutions)
Enzyme activity vs. Substrate concentration was graphed
Michaelis-Menten Plot : Reaction velocity (M/min) vs. Substrate Concentration (M)
V 0=V max×[S ]
[S ]+Km
Lineweaver-Burke Plot : Reciprocal of reaction velocity (1/M-min-1) vs. Reciprocal of Substrate concentration (1/M)
Procedures for determination of achromic point, amylase units, and enzyme activity were performed with the 2 mL phosphate
4
buffer, pH 6.2 in the digestive mixture being varied
Enzyme activity vs. pH was graphed
Effect of Temperature Procedures for determination of achromic
point, amylase units, and enzyme activity were performed with the temperature of digestive mixture being varied (3 temperatures < 38℃ < 2 temperatures)
Enzyme activity vs. Temperature was graphed
B. DISCUSSION
Enzymes Biological catalysts that enable biochemical
reactions to occur in actual physiological conditions by lowering their activation energy
Contain highly specific active sites to which certain substrates can bind to form an enzyme-substrate complex
Highly sensitive to pH, temperature, and reactant concentrations
Regulation by Inhibition:o Competitive – inhibitor binds to active
siteo Non-competitive – inhibitor binds to
enzyme at site other than active site
Salivary Amylase Also known as ptyalin Hydrolyzes starch and glycogen through its
action on α-1,4- glycosidic bonds Starch dextrins maltose Optimum pH range: 5.6 to 6.9 Optimum temperature: 38℃
Starch-Iodine Test Starch is a polymer of α-D-glucose
molecules bound by α-linkages; it forms a helical structure
This structure is significant because it forms a complex with iodine molecules as the I2
particles nestle themselves within the helix and for a blue-black complex
In the lab, this can be used to test the presence of starch in a certain solution
Achromic Point
The point at which no blue-black color is produced when a drop of digestive mixture is added to I2-KI
The non-formation of blue, black, or violet is indicative of the cleavage of the starch in the digestive mixture into maltose as there is no helix into which the iodine can insert itself
Amylase Units and Enzyme Activity Using the number of minutes it took to reach
achromic point, amylase units and, consequently, enzyme activity of the amylase in the collected saliva can be computed
Amylase units (#AU) : the amount of amylase needed to digest 5 mL of 1% starch
¿ dilution factor ×mL digestivemixtureminutes ¿
achromic point ¿
Note: mL of digestive mixture in our experiment was 10 mL; dilution factor is equal to total mL of solution divided by mL of enzyme (in this case, saliva)
Enzyme Activity (EA) : the amount of starch (in mg) hydrolyzed per minute per unit enzyme
¿ mg starchminutes ¿
achromic point× ¿ AU ¿
Enzyme Kinetics Effect of Enzyme Concentration
o There is a positive relationship between enzyme concentration and the rate of reaction or enzyme activity
o Graph does plateau, however, since substrate concentration is kept constant
Effect of Substrate Concentration o Theoretically, there should also be a
positive relationship between substrate concentration and the rate of reaction or enzyme activity
o However, the reality is that enzymes occur in finite quantities in the body—even if the substrate is abundant, enzyme-substrate complexes can only form if there are available enzymes
5
Michaelis-Menten Equation
V 0=V max×[S ]
[S ]+Km
Reaction Velocity vs. Substrate concentration
The Michaelis-Menten constant (Km) describes the affinity of the enzyme and substrate; Km = affinity
At Km, the rate of reaction is at 50% of Vmax
Lineweaver-Burke Equation
1V o
= 1V max
+K m
V max
∙1[S ]
1/Reaction Velocity vs. 1/Substrate Concentration
To linearize the M-M plot Slope of Line Equation = Km / Vmax
x-intercept of line = - 1 / Km
y-intercept of line = 1 / Vmax
Effect of pH on Enzyme Activity The acidity or alkalinity of the environment
in which the enzyme occurs can affect its active site (conformational changes may occur)
Extreme pH can cause the protein to dismantle (too low and carboxyl ions protonate; too high and amino groups will be deprotonated)
Graph is a bell curve as there is an optimum range
Effect of Temperature on Enzyme Activity Higher temperatures generally benefit
chemical reactions in that they enable higher kinetic energy of the molecules, thus increasing rates of collision and reaction
Graph is skewed to the right as increasing temperatures can speed up reactions but after a certain point (i.e. 38℃), the rate of reaction will decline
Extremely high temperatures denature the enzymes
6
III. THE ANIMAL-LIKE Paramecium
A. EXPERIMENT PROPER
Gross Morphology & Movement Immobilize Paramecium using either 2%
agar or cotton fibers After noting observable morphology, stain
with methylene blue to visualize macro- and micronuclei and other features
Digestion Yeast feed – yeast and water were boiled
for 8 minutes then cooled, liquid decanted, and 4 drops of Congo Red were added 0.1 g dry active yeast 40 mL d H2O Congo red
o Note: orange red in pH 5.0 or above, blue in pH 3.0 or below
Slides were prepared using both agar and cotton fiber method
1 drop of stained yeast feed was added to cover slip then slide was observed immediately
Role of Contractile Vacuole1. Solutions
d H2O Paramecium culture liquid 2.5%, 3%, 5%, 7.5% 10% NaCl M/500 KCN (13 mg solute in 100 mL
water) 0.1% neutral red
o Note: red in acidic medium, yellow in alkaline medium
2. Procedure Determination of pH of contractile
vacuole contentso Slides were prepared with cotton
fiberso 1 drop neutral red onto culture before
laying on cover slip to determine pH of contractile vacuole contents
Counting the pulsations of contractile vacuole per minuteo Slides were prepared using both agar
and cotton fiber immobilization techniques
o 1 drop of the different solutions was added before covering
o Number of pulsations was counted under the microscope
Thigmotaxis Observe Paramecium slide prepared using
cotton fiber method; note difference in movement when anterior and posterior ends hit thread
Chemotaxis1. Solutions
0.2% HCl 0.2% CH3COOH 0.1 M NaHCO3
3% NaCl 5% sucrose
2. Procedure Prepare Paramecium slides without
cotton fibers and agar Dip cotton thread into each of the
solutions listed above and lay it on the slide
Observe reaction of organism
Geotaxis & Phototaxis Geotaxis
o Test tube was filled ¼ of the way up with Paramecium culture then set upright in a test tube rack
o Positioned under a bright light for 15 minutes
Phototaxiso Test tube was filled ¼ of the way
with Paramecium culture then sealed with a rubber stopper
o Tube was laid on its side and its upper surface was covered with foil
o Light was shone from below the tube
Galvanotaxis Ringer’s Solution (1 L)
6.5 g NaCl 0.14 g KCl 0.12 g CaCl2 0.20 g NaHCO3
0.01 g Na2HPO4
4 x 0.5 x 0.3 cm Paraffin well on slide Fill well with 3-5 drops of Ringer’s solution
and culture Attach uninsulated ends of 24-gauge wires
with tape; wires connected to batteries to close the circuit
Voltage was adjusted to 4.5, 6, 7.5, 9.0, and 12 V using multiple batteries
7
B. DISCUSSION
Paramecium Kingdom Protista, Phylum Ciliophora;
eukaryotic, unicellular “animal-like” = locomotory, no cell wall,
heterotrophic easily excitable cell membrane
Gross Morphology
Slipper-shaped, dorsal surface is convex while ventral surface is flattened
Anterior end is more blunt, posterior end is slightly pointed
Cilia line the outside of the Paramecium and function for movement and gathering and moving food towards the oral groove
Ectoplasm – clear outer zone of cytoplasmo Pellicle – protective layer that
Ingestion: food enters the oral groove then vestibule then cytostome by movement of the cilia
Digestion: food is received by the gullet or cytopharynx, where a food vacuole will form
8
and bud off of the gullet and starts travelling around the cell in a clockwise path (cyclosis); note that it also decreases in size as it travels around the cell
The food vacuole contains lysozyme that hydrolyzes its contents, thus shifting the internal pH to acidic then back to alkaline (Congo red can be used to visualize this transition: blue red blue)
Egestion: release of alkaline digestive wastes through the cytoproct or anal pore (note that nitrogenous wastes are released through the cell membrane) and the re-fusion of the food vacuole with cytopharynx
Role of Contractile Vacuole Contractile vacuoles can also be called
water-expulsion vacuoles as they expel water; they facilitate the excretory pathway for nitrogenous wastes (urea and ammonia)
They are homeostatic; prevent cytolysis and osmolysis
Anterior and posterior contractile vacuoles do not pulsate or beat at the same time; they are temporary structures
Water passes through the radiating canals and into the vacuoles before being exuded through a pore
During diastole, the vacuoles enlarge, while they collapse in systole
Rate of discharge varies with temperature Higher rate of discharge occurs when
Paramecium is inactive Higher rate of discharge occurs when there
is a low salt concentration By creating a gradient wherein there is
higher salt content in the external environment, water is able to diffuse out of the cell
The contents of the contractile vacuole are acidic and, therefore, should appear red when stained with neutral red
Effect of Test Solutions on the Contractile Vacuole
As expected, most pulsations occur when the Paramecium is exposed to distilled water and least when in 10% NaCl
KCN is poisonous; in this case, it reduced the production of ATP in the mitochondria (inhibits NADH oxidase) and affected the contractions negatively
Thigmotaxis Negative response to stimuli
9
Difference between reactions when opposite ends are touched is due to type of channels located on each
Anterior end: reverse movemento Depolarization of membrane by
influx of Ca2+, cilia slow down and Paramecium reverses
Posterior end: faster forward swimmingo Hyperpolarization of membrane by
efflux of K+, cilia accelerate
Chemotaxis Defined as the directional response to
chemical stimuli (innate mechanism) Not to be confused with chemotactic
response, which refers to the reactions of Paramecium to a new or unknown stimuli
Chemokinesis, on the other hand, is random change in movement of organism due to chemical stimuli
Poositive chemotactic response to weak acids and sugar solutions (acetic acid and sucrose)
o Paramecium thrive in slightly acidic environments as the main component of their diet, bacteria, regularly occur in slightly acidic media
o Causes the hyperpolarization of the membrane (more negative membrane potential) and, thus, acceleration of ciliary beat
Negative chemotactic response to strong acids, bases, and salt solutions (HCl, NaHCO3, and NaCl)
o Salt solutions are hyperosmotic and, thus, cause the depolarization of the membrane as water rushes out of the cell (also, Paramecium is a freshwater resident)
o Strong acids have adverse effects on Paramecium; high concentration of H+ causes depolarization of membrane
o Bases cause the depolarization of the membrane due to the low concentration of H+
Geotaxis Response to gravity Paramecium exhibit negative geotaxis Individual organisms gather near the surface
of the medium
Mechanoreceptors on their anterior and posterior ends allow them to reorient themselves based on the pull of gravity
Buoyancy is also helped by the contractile vacuole
Phototaxis Response to light Positive phototaxis This response could be an adaptation to
find food (i.e. bacteria) Light could also follow increased
temperatures—the optimal temperature for Paramecium is said to be around 23℃
Galvanotaxis Response to electric current or flow of
charges in a medium Generally, Paramecium is attracted to the
cathode (negatively-charged pole) since they are naturally positive outside their membranes
In weak electrical voltage, the organisms moved towards the cathode
In strong electrical voltage, the organisms moved towards the anode then died
Depolarization due to Ca2+ influx causes ciliary reversal and movement to the cathode
Hyperpolarization due to the efflux of K+
causes ciliary augmentation or acceleration and movement to the anode
Ludloff Phenomenon: hyperpolarization of Paramecium causes ciliary augmentation
10
IV. OXYGEN CONSUMPTION AND METABOLIC RATES OF TERRESTRIAL ANIMALS & MEASURING CARBON DIOXIDE PRODUCTION IN ANIMALS
A. EXPERIMENT PROPER
1. Balb/C mouse 5-month old male Weighed using top-loading balance Inbred albino strain of mice commonly
used in the lab due to their reproductive efficiency and longevity
2. O2 consumption and CO2 production measurement 4.53 L-capacity PASCO EcoChamber
o Mouse was acclimatized for 5 minutes
o Lid was sealed with masking tape and entire chamber was covered with a lab gown to minimize mouse stress
PASPORT Temperature Sensor PASPORT O2 Sensor
o Calibrated to around 20.9% PASPORT CO2 Sensor
o Calibrated to around 400 ppm PASCO Scientific DataStudio
o Measured O2 and CO2 content of metabolic chamber for 10 minutes
3. Values computed for: Volume of O2
o V O2observed converted to μL/L
¿(V O2 initial– V O2 final
)×capacity of chamber∈L
o V O2corrected
¿V O2observed×755mmHg760mmHg
×273
273+T∈℃
Metabolic Rateo Basal Metabolic Rate (MR in g-cal/hr)
¿V O2corrected
mL
minutes×4.7ca lories
mL×60
o Mass-specific Metabolic Rate (MSMR in g-cal/hr/g)
= MR
massof animal
Volume of CO2
¿V CO2 final–V CO2 initial
Respiration Rate (RR in μM/g/hr)
¿V CO2observed
massof animal (g)×time(hr )4. Graphs needed:
O2 concentration vs. CO2 concentration Mass-specific metabolic rate vs. mass Respiration rate vs. mass
B. DISCUSSION
Metabolism Sum of all biochemical activity occurring
within an organism Related to the amount of energy that the
organism needs to function Two types:
o Anabolism – reductive reaction to synthesize bigger molecules using smaller ones; requires energy
o Catabolism – oxidative breakdown of complex molecules into smaller ones; releases energy
Two pathways based on the presence of O2:o Aerobic – in the presence of oxygen;
36-38 molecules of ATPo Anaerobic – in the absence of
oxygen; 2 molecules of ATP
Measurement of Metabolic Rate Metabolic reactions transform chemical
energy into heat energy; measure the amount of heat energy transformed per unit time measures metabolic rate
Direct – measuring heat produced directly (i.e. ice bath calorimeter)
Indirect – based on gas exchange; assumes that the intake of O2 and the output of CO2 corresponds to metabolic activity and relates the concentrations of these to heat production through stoichiometry
o Radioisotope Labelingo Respirometry
Warburg Method Pressure
measurement of gases
11
Gilson Respirometer Absorption of CO2
animal releases
Different Metabolic Rates in Individuals Standard or Basal Metabolic Rate
o The use of “standard” or “basal” to describe this depends on the mode of thermoregulation employed by an animal
o SMR is measured for ectothermic animals while BMR is measured for endothermic animals; BMR must be measured within the endotherm’s thermoneutral zone (when they expend no energy to regulate their core temperature)
o Measured under 3 conditions:i. Resting state outside of
reproductive stageii. Fasting or in post-absorptive
stateiii. Free from physical, thermal,
and psychological stress (i.e. not expending any energy to regulate temperature)
Active Metabolic Rate o Measured while animal is being
motivated or exposed to a stressoro Maximum level of activity (i.e.
exercising) Routine Metabolic Rate
o Measured while animal is unfed and performs its usual daily activities; in their natural habit and habitat
Correcting Observed Volume of O2
Based on the effect of actual deviations from standard pressure and temperature conditions, 760 mmHg and 0 K, respectively, on the volume of gas measured
Note: Ideal Gas Law: PV = nRT
Factors That Affect Metabolic Rate Mass or Body Size
o A larger animal would require more energy to maintain its function, therefore, it would have a higher metabolic rate
o However, small animals have higher metabolic and respiration rates per unit mass so there is an inverse
relationship between mass and mass-specific metabolic rate
Surface Area to Volume Ratio o Smaller animals that have a higher
surface area to volume ratio have higher metabolic rates than larger animals
o Heat radiates from the animal’s skin—a small animal would gain and lose more through its skin due to the lack of solid mass in their body to retain heat—so, in a sense, they compensate by facilitating higher metabolic activity
Temperature o Generally exhibits a positive
relationship with metabolic rate as oxygen consumption is said to increase with temperature
o In addition, higher temperatures favorably affect enzyme activity during metabolism
Light o Most drastically affects metabolic
rate through the circadian rhythm of organisms; diurnal animals are more active during the day and, thus, have higher metabolic rates during this time
o Studies have shown that light may affect metabolic rate as it stimulates the release of certain hormones
o In addition, a higher level of activity usually occurs in well-lit areas (i.e. fish as they forage)
Sex o Generally, men have higher rates of
metabolism than womeno Differences are due to male and
female differences in body composition (fat vs. muscle)
Factors That Affect Respiration Rate Temperature
o Generally, respiration increases with higher temperature—however, while this relationship is established, it does not occur too frequently as other factors more drastically affect respiration rate
o For ectotherms, their respiration rate increases while they adjust to their ambient temperature but, after they
12
reach physiological temperature, the rate normalizes or decreases
o For endotherms, temperature is only a notable factor when they are inactive
Level of Activity o Generally, a higher level of activity
results in a higher rate of respiration (for obvious reasons)
Size o Generally, larger animals have
higher rates of respiration as their functioning requires more metabolic activity
Possible Sources of Error Calibration error Stressed mice CO2 production is not a very accurate way
to measure metabolic rate:o Aside from exhaled CO2, there is a
large pool of free and dissolved CO2
in the bodyo Unlike O2 consumption, CO2
production (read: actual metabolic activity) is substrate dependent
