Biology 2601 (copy)

The milieu intérieur

Claude Bernard coined this term to describe the internal environment of organisms as distinct from the external environment

-he believed that the ability to maintain internal environment is related to a highly evolved organism

-variables such as water, ions, glucose, pH, temperature, gases and wastes

Pros and Cons of Regulation

Pro-cells experience constant conditions

Con-energetically costly (requires a lot of eating)

Pros and Cons of Conformity

Pro- energetically cheap

Con- cells must have mechanisms to cope with variability

Zone of Tolerance

-once outside of the tolerance zone the organism will conform, either below or above tolerance

Homeostasis

-the coordinated physiological processes which maintain most of the constant states in the organism (Walter Cannon)

-the condition of a relatively stable internal physiological environment, usually involving extensive feedback mechanisms

How does homeostasis work?

-with a negative feedback loop

-effectors (feathers)

-controlled variable (eg temp)

-sensor (eg hypothalamus)

What are the ways that homeostasis is achieved?

Hormonal

Neuronal

Biochemical

Molecular

Is fever homeostasis?

Yes, because the set point is changing to kill infection, until the set point returns to normal

Positive Feedback

-a control system reinforces deviations of a controlled variable from a set point

eg. a voltage gated ion channel

Scaling

-the study of how structural, mechanical, and physiological properties chain with changing size

Direct Proportionality in Organisms

-isometric scaling

Y=aX^b1 or

LogY=1LogX+Loga

Proportionality changes with size (non-linear) in organisms

-allometric scaling

Y=aX^b

LogY= blogX+Loga

Body Size

when b=1

when b

-when b=1 the scaling is isometric, eg the blood volume of mammals increase in proportion to body size

-when b

What is the most expensive form of transportation?

walking/running is the most expensive and taxing

Define energetics

-the study of how organisms "acquire energy, channel energy into useful functions, and dissipate energy from their bodies"

Anabolism vs Catabolism

Catabolism-breakdown of molecules to release energy

Anabolism-use of energy to assemble molecules

The 2nd Law of Thermodynamics

-entropy always increases

-it takes energy for animals to survive and remain organized

What is energy?

Biology-the capacity to increase order

Chemical Bond Energy

the energy liberated or requires when atoms are rearranged into new configurations

eg. ATP

Electrical Energy

the energy that a system possesses by virtue of the separation of positive and negative charges

eg. membrane potentials

Mechanical Energy

the energy of organized motion in which many molecules move simultaneously in the same direction

(the sum of kinetic and potential energies)

eg. moving a limb or circulating blood

What does heat do in terms of organisms?

-determines temperature which influences biological rates but does not do physiological work

Calorie vs calorie

Calorie- 1 kilocalorie

calorie- the amount of energy (heat) needed to raise the temperature of 1g of water by 1C

Define metabolic rate

-the rate at which an animal consumes energy

-this can be measured form heat production (calorimetry)

Respiratory Quotient

=CO2 produced/ O2 consumed

Define the different types of metabolism

BMR-basal metabolic rate, the measure of maintenance metabolism, endothermic homeotherms, thermoneutral zone, fasting (post absorptive) resting

SMR- standard metabolic rate, ectothermic poikilotherms, fasting, resting at a defined temperature

FMR- field metabolic rate, the daily energy expenditure of a free-living animal

Specific dynamic action

-the increase in metabolic rate associated with food ingestion

How does metabolic rate scale?

-metabolic rate scales allometrically, at a slope of 0.7-0.75

Describe the power curve for running

-the rate of O2 consumption increases linearly with speed

Describe the power curve for flying

-metabolic rate and flight speed graphs tend to be U shaped due to having to overcome gravity in the beginning of flight

The Metabolic Ceiling

-you can spend up the 7x your BMR (with good organs)

Define Temperature

-measure of the speed or intensity of the incessant random motions that all the atoms and molecules of any substance that undergo on an atomic-molecular scale

Convection vs Conduction

Convection- the transfer of heat by movement of liquid or gas

Conduction- the transfer go heat by solid materials

Define Endotherms

-generate internal (metabolic) heat

Define Ectotherms

-they rely mostly on external temperatures to determine body temperature

Define Homeotherms

-they defend a constant body temperature

Define Poikilotherms

-they allow their body temperature to vary

Define Heterotherms

-they have more than one temperature set point, or switch between home and poikilothermy

Define regional endothermy/heterothermy

-body temperature is different in different parts of the body

Give an example of an endothermic homeotherm

-cheetah, humans, cats etc

Give an example of an ectothermic homeotherm

-lizards, reptiles etc

Give an example of an endothermic poikilotherm

-dragonfly, certain plants

Give an example of an ectothermic poikilotherm

-frogs and some plants

Describe the relationship between temperature and metabolism in an ectotherm

-as body temperature increases, metabolism also increases at an almost exponential rate

-therefore the higher the temperature the more O2 is consumed by the organism

What is the equation for metabolic rate?

M=a(10)^(nTb)

-where M is the metabolic rate

-a and n are constants

-and Tb is body temperature

*on a log scale of O2 consumption the

-the graph is linear

-the y intercept is log(a)

-the x axis is Tb

-and the slope is n

The Temperature Quotient Q10

-this is defined as the ratio of the rate of a process at one temperature over the rate of the same process at a temperature 10C lower

Q10=Rt/R(t-10)

-because the temperature-metabolic rate relationship is not exactly exponential, the impact of a change in temperature varies with temperature

-the same ratio for Q10 holds true for plant functions like respiration

What does it mean is Q10 is/close to 1?

-if Q10 is close to 1 then there is no significant change in rate as temperature changes

What is the Q10 for most biological processes?

-around 2-3 (or higher)

Explain how temperature causes metabolic changes to occur?

-temperature determines the motion of molecules, and therefore their rate that they encounter each other, more interactions=more reactions

-temperature also determines the conformation and efficiency of enzymes (Q10=(approx.) 2-3 in biological systems), and most enzymes have a temperature optimum which can effect efficiency

-enzymes active sites can change shape with temperature, leading to a change in binding affinity for substrate

What does Km have to do with enzyme-substrate affinity?

-Km is the amount of substrate required to reach 50% of the maximum reaction rate

-1/Km can be used to examine enzyme-substrate affinity

-high Km=low affinity

-low Km=high affinity

Explain how enzyme-substrate affinity changes with temperature

-enzyme-substrate affinity decreases with temperature

-the enzymes do have a normal operating temperature

What happens to enzyme-substrate affinity at low temperatures?

-enzyme-substrate affinity is high at low temperatures

-at low temperatures substrates bind so well and tightly to enzymes that the reaction rate is slowed down

What happens to enzyme-substrate affinity at high temperatures?

-enzyme-substrate affinity decreases with temperature

-the affinity is too low to the substrate binds too loosely meaning reactions are less likely to happen, decreasing the reaction rate

Adaptation vs Acclimitization

Adaptation-it is an altered genome

-it is a genetically controlled trait that through the process of natural selection has come to be present at a high frequency in a population

Acclimitization- is an altered expression of the genome

-it is a chronic response of an individual to a changed environment in cases in which new an old environments are natural environments that can differ in numerous ways, it is a form of phenotypic plasticity

Define Compensation

-to maintain performance in the face of varying conditions

-requires a shift away from the acute response

-plasticity on the order of hours to days to weeks

How does compensation work?

-changes enzymes in a pathway

-by changing the amount of the enzyme, version of the enzyme, phosphorylation and changing the enzyme's environment in the body/cells

How does changing the abundance of an enzyme affect reaction rate?

-compensation increases the amount of enzymes to compensate for low efficiency at low temperatures

How do isoenzymes work to compensate?

-these are enzymes that differ in amino acid sequence but catalyze the same chemical reaction

-they usually have different Km values and they permit the fine-tuning of metabolism to meet the particular needs of a given tissue

How does phosphorylation work to compensate?

-phosphorylation of an enzyme can activate it, change is conformation or alter its activity

-this is mediated by protein kinases and protein phosphatase

-for example, when there is too much light LHC 11 is phosphorylated by protein kinase and when there is less light protein phosphatase dephosphorylates the enzyme

How does changing an enzyme's microenvironment compensate?

-changing pH, substrate availability and lipid environments will change activity nd will alter the rate of the reaction

Describe how phospholipid membrane changes contribute to compensation

-homeoviscous adaptation is essential for compensation, it is the ability to maintain the same viscosity across temperatures

-short chain lengths increase fluidity (goof for low temperatures, less London forces), incorporating double bonds increases fluidity (good for low temperatures, they do not pack nicely using unsaturation) and changing head groups changes fluidity

Why is membrane fluidity important?

-if membranes become to rigid or too fluid their semipermeability is damaged

Are ectotherms passive victims of their thermal environments?

NO

Why aren't ectotherms passive victims of their environment?

-they use behavioural thermoregulation by adjusting their location

-for example lizards move to high rocks to sunbathe when they need to heat up and move into shade when cooling is needed

-in plants to eliminate evaporative heat loss rolling leaves and pointing them vertically reduces sun interception which saves water

Why are fish ectotherms?

-fish can generate heat (with metabolism like anything else) but they have problems keeping the heat because they are constantly surrounded by thermally-conductive water

Describe endothermic homeotherms

-they maintain a high and stable body temperature using internal heat

-they have a high basal metabolic rate (even cells have more mitochondrial volumes)

-Mechanisms to retain heat such as insulation (fur, feathers and blubber)

Define thermal inertia

-the idea that size keeps warmth

What is the equation for power to maintain a heated object at a certain temperature?

P=C(T(set)-Ta)

-when the temperature is at the set point zero power is used

-C=|slope| which is the thermal conductance

How does insulation change the amount of power to maintain a temperature?

-having insulation reduces the power required to maintain a certain temperature, the slope is decreased on the graph

-adding fur or feathers reduces the thermal conductance because less power/energy is required to maintain heat

The Scholander Curve

M=C(Tb-Ta) (body temperature-ambient temperature)

-the slope C is the conductance

-the thermoneutral zone is where MR is constant, the graph is horizontal here

-as the ambient temperature increases or decreases out of the thermoneutral zone the MR increases to either dump heat or maintain it

Vasodilation vs Vasoconstriction

Vasodilation- occurs when the organism is hot, the surface blood vessel expand and release heat through the skin, this is a form of high conductance

Vasoconstriction- occurs when the organism is cold, the surface blood vessels constrict to retain heat, this is a form of low conductance

Pilomotor vs Ptilomotor

Pilomotor- changing conductance using fur

Ptilomotor- changing conductance using feathers

Describe how postural changes can affect conductance

-when the ambient temperature is cold organisms pull in their extremities, bend over and fluff their feathers (if they have any) to retain their heat

-when is it very warm organisms stretch their extremities far from the body and flatten any fur or feathers

-penguins for example huddle together to retain warmth of a large group

Describe regional heterothermy through countercurrent exchange

-in animals where the climate is very cold, their extremities need a way to maintain heat

-to do this their arteries and veins are right next to each other going to the distal end of the extremity, this way the warm blood in the artery transfers heat through a temperature gradient to the now cold blood in the vein

-this blood is now still relatively warm so less energy is needed to reheat it

Does having less insulation result in higher or lower thermal conductance?

-having higher thermal conductance means that the organism has less insulation

-this is why cold adapted animals have lower thermal conductance than tropical animals

How do organisms change through seasons to affect conductance?

-some organisms shed their insulation and have much thinner fur in the summer months

-others change their peak metabolic rate

Define shivering

-non-synchronous muscle contractions that generate heat

Non-shivering thermogenesis

-the production of excess heat by futile cycles

-for example, H+ leaks across the inner mitochondria membrane mediated by uncoupling proteins, no ATP is made but heat is generated

-uncoupling protein 1 is found in the brown fat of animals, brown fat is specialized for non-shivering thermogenesis

-neonatal animals have a large amount of brown

Brown fat vs White fat

Brown fat- is densely packed

White fat- much less dense

-fat is burnt to produce heat but if there isn't enough heat produced shivering occurs

Heat loads at upper critical temperatures

-at the UCT conductance is maximal (spreading limbs)

-above the UCT excess heat can be stored or lost by evaporation (sweating, licking, panting vulgar flutter etc)

Describe thermogenesis in aroids

-this is not inhibited by CO, cyanide or azide

-it is an alternative oxidase pathway which does not involve pumping H+ and no ATP is produced

Describe regional endothermy in flight muscles of bees and moths

-they shiver before and during the flight

-this regulated blood flow to be at a constant temp

Describe regional endothermy in tuna

-tuna shows regional endothermy in 19C water

-its core swimming muscles are at a high 31C and other parts of the body range from 19-29C as well giving the fish much better swimming abilities than other fish

Area of Rete Mirable

-retains heat in a small region of the organism in water

-the vessels are right next to each other so warm blood can transfer heat to the now cold blood in the vein, the heat stays towards the centre

What bony fish evolved regional endothermy?

-billfishes have water eyes and brain which increase visual abilities

-tunas have warmer swimming muscles increasing their swimming abilities

-butterfly mackerel

Why do fish sometimes show regional endothermy?

-to allow long migration through water of different temperatures

-to allow better performance as a predator chasing prey into colder water

-improvements in power output of muscles or vision

Describe the role of photosynthesis in the global carbon cycle

-there is a net increase in C in the atmosphere

-the amount of carbon in every place are larger

Light-dependent vs Light-independent reactions

-these reactions are coupled

Light-dependent

-uses water and produces oxygen

-uses ADP, NADP+ and produces ATP and NADPH

-gets energy input from photons

-we can use O2 production to measure the rate of photosynthesis

Light-independent (carbon reaction)

-uses CO2, ATP and NADPH

-produces sugars, ADP and NADP+

-gets energy input from the light-dependent reactions

-we can use net CO2 consumption to measure the rate of photosynthesis

What are pigments?

-molecules that absorb photons, they are generally coloured (their reflective wavelengths)

-absorption of a photon inverses the energy level of the molecule

-blue light I the higher excited state and red light is the lowest excited state

What is found in the granum within the chloroplasts?

-photosystem 2 (PS11), light harvesting complex 2 (LHC11) and ATP synthase

What is found in the stroma?

-photosystem 1 (PS1), light harvesting complex 1 (LHC1) and ATP synthase

How do plants catch light?

-energy from the harvested proteins is transferred to the reaction centre

-the LHC acts as a satellite to allow PS to transform the photons into energy

Describe the photosynthetic electron-transport chain

1. oxygen evolving complex strips electrons from water, passes them to oxidized P680

2. charge separation at PS11 yields electrons and oxidized P680

3. electrons "stored" in the plastoquinine-pool are transferred to oxidized P700 via the photosynthetic electron-transport chain

4. second charge separation at PS1 yields electrons and oxidized P700

5. electrons passed to strong reductant (NADPH)

Describe the oxygen-evolving complex

-this oxidizes water

1. the reducing potential is transferred via the plastoquinone (PQ) and plastoquinol (PQH2)

2. energy lost includes driving a photon gradient

3. plastocyanin transfers electron to PS1

4. ferredoxin complex reduces NADP+

5. protons drive ATP synthase

Where does the light driven reactions take place? What is used and what is produced?

-they take place in the thylakoid membranes

-light, water, NADP+ and ADP + Pi are all used in this reaction

-O2, NADPH and ATP are products

Where does the Calvin-Benson cycle take place? What is used and what is produced?

-this reaction takes place in the stroma

-NADPH, ATP, CO2 and water are used

-NADP+, ADP+Pi and sugars are produced

How is carbon taken from the atmosphere?

-carbon is taken from the atmosphere by rubisco during carboxylation

Describe the photosynthetic carbon reduction (PCR) cycle

aka Calvin cycle/Calvin-Benson cycle

-carbon and water are used in carboxylation by rubisco

-ATP and NADPH from light dependent reactions are used in the reduction portion which produces ADP+Pi and NADP+ as well as sugars

-ATP from light dependent reactions is used in regeneration

Carboxylation

-catalyzed by rubisco

3(5-C molecules) + 3(1-C molecules) -> 6(3-carbon molecules)

3(ribose 1,5-biphosphate) + 3CO2 + 3H2O -> 6(3-phosphoglycerate)

Rubisco

-ribulose-1,5-biphosphate carboxylase oxygenase

-this is the most abundant protein on earth

-it has 8 small which are encoded into the nuclear genome, and 8 large ones in the chloroplast genome