metabolism and thermal physiology

Question 1

what is the difference between anabolic and catabolic pathways

Answer 1

A- assembling simple molecules into complex = requires energy

c- breakdown of complex molecules into simple ones = releases energy

Question 2

Describe the laws of thermodynamics and how they apply to life

Answer 2

1) energy cant be created or destroyed- suggest life might operate forever on internal energy content
2) entropy(disorder) of a system+surroundings increases over time as energy decreases to ‘unusable’ heat, opposing law 1

each cell needs energy for function and performance in order to contribute to homeostasis which is provided by food and regulated to maintain this energy balance

Question 3

Define internal and external work in an animal and why heat is the primary output

Answer 3

1) external work- expenditure when skeletal muscles contracted to make more external objects
2) internal work- all other expenditure used to susatin life such as heart rate

heat is the primary output because any energy which is not used for work is given out as heat which can be used to maintain body temperatures
energy input must = energy ouput

Question 4

Define metabolic rate, standard and basal metabolic rate

Answer 4

metabolic rate = the sum total of all chemical reactions occuring in an organism

basal= the minimal amount of energy needed per unit of time to sustain working life under optimum conditions in endotherms

standard= the minimum amount of enegry needed per unit of time to sustain working life at a specified temperature usually used for ectotherms

Question 5

define dietary induced thermogenesis (DIT) and explain how it is measured by indirect calorimetry

Answer 5

DIT= an increase in metabolic rate about basal metabolic rate as a result of food intake
- can be measured using direct calorimetry = using insulated chamber and measuring differences in water in vs out= coslty and assumes all energy ends up as heat

= indirect methods- respiratory methods where 02 intake per unit of time is measured assuming there is a direct relationship between o2 inspired and heat produced

Question 6

Discuss scaling features and hypotheses regarding BMR?SMR

Answer 6

• BMR/SMR differs among species one reason is down to scaling e.g. SA:V
• larger animals consume more energy than smaller however have a lower BMR per unit of mass
• smaller organisms have a larger AS:V, endotherms generate heat which is lost through SA
• therefore smaller organisms must have higher MR per unit mass to compenstate for increased heat loss

Question 7

describe the three states of energy balance

Answer 7

1) Energy going into the body > Energy leaving the body = The body has positive energy balance.
2) Energy going into the body < Energy leaving the body = The body has negative energy balance.
3) Energy going into the body = Energy leaving the body = The body has equal energy balance.

Question 8

describe the role of the hypothalamus in energy balance regulation

Answer 8

regulation is controlled using sensors, integrators and effectors
food intake is controlled by the hypothalamus which has integrators located in the arcute nucleus which when stimulated tells if hungry or not
stimulated by feeding centres which tell you when to eat and seity centres which tell you when youve had enough

Question 9

what is the arcute nucleus

Answer 9

found in the hypothalamus is the integrator informing the body of food intake for energy balance
- contains 2 subsets of neurones which oppose one another
1) NPY(neuropeptide Y) which stimulates hunger
2)MSH which suppresses hunger

Question 10

Describe the source and role of the following in regulation of energy balance:
Leptin, insulin, Ghrelin and CCK

Answer 10

1) leptin inhibits NPY= signals for long term energy balance
- adipocytes/fat cells secrete hormones leptin which informs of how much triglycerides are present in fat tissues so more fat = more leptin creating negative feedback therefore suppressing appetite

2) Insulin stimulates cellular uptake therefore more insulin means more nutrients in cells and inhibits NPY suppressing apetite

3)Ghrelin= signals for short term energy balacne aka hunger hormone rises before a meal activating NPY stimulating appetie

4) CCK- important suppressor and signal for meal size and released when there is presence of nutrients in small intestine

Question 11

discuss the evolutionary differences in body-mass set points

Answer 11

different energy balance set points differ in different species and are a result of evolutionary adaptations for differences in food supply, there are 2 extreme set points
1) lean- increased leptin level set point as habitats with lots of food so storing more fat is not needed allowing individuals to be more agile

2) obese- decreased leptin levels habitats with less food mean increased fat storage to wait for next meal

TRADE OFF - INCREASED BODY MASS MEANS DECREASED AGILITY/MOBILITY WHICH MEANS EASIER PREY

Question 12

describe the basic effects of temperature on biological systems

Answer 12

1) alters rates of chemical = Q10
2) denatures macromolecules = optimum curve
adaptations= membranes held by hydrophobic bonds affecting fluidity, too hot increased fludity too cold reduced, can be changed by degree of sturation of fatty acids to maintain fludity

Question 13

define endothermy, ectothermy, poikilothermy and homeothermy

Answer 13

1) endothermy = an animal dependent on or capable of the internal regulation of heat

2) ectotherm= an anaimal which is dependent on external sources of heat

3)poikilotherm= an organisms that can not regulate its body temperature except by behavioural means such as basking

4)homeothermy= an organisms that maintains body temperature at a constant level by metabolic activity

Question 14

Discuss features of the four heat transfer mechanisms: radiation, conduction convection and evaporation

Answer 14

1) radiation- light energy which can be emitted and absorbed wether a body gains or loses depends on difference in temp between skin surface and object surface as heat moves from hot to cold

2) conduction= transfer of heat between objects of different temperature gradients in direct contact which depends on temperature difference and thermal conductivity

3)convection= transfer of heat by currents of air/water, convection currents carry heat away replacing with cold air. can be enhanced by the forced movement of air

4) evaporation= when water evaporates the heat needed for it to change state is absorbed from the skin

Question 15

Discuss body heat balance and the key features of gain, retain, generate and lose heat

Answer 15

heat gain vs loss determines core body temp and has mechanisms to
1) gain = use of solar radiation, avoiding cold areas
2) retain = entropy means all metabolism produces heat and can be retained by behaviours , insulation, counter current exchange and larger body size
3) generate more= a feature of endotherm requiring significant heat generating tissues
4) lose excess heat = avoiding hot environments by behaviour, anatomy, increase blood flow, increased evaporation

Question 16

what affects an individuals energy demand

Answer 16

1) size and mode of thermal regulation
2) locomotion and movement
3) development
4) reproduction
5) temperature

Question 17

Describe the different responses in pure poikilothermy and ectothermic regulation

Answer 17

poikilothermy= metabolic rate decreases in cold temperatures and increases in warm, survival may depend on behaviours in order to avoid extremes , pure poikilotherms have an identical temp to the external environment

ecothermic regulation= cant cope with extreme temperature changes

Question 18

discuss the biochemical adjustments that account for metabolic compensation in ectotherms

Answer 18

metabolic compensation is a form of homeostatis where metabolic rate increases to that of what it would be if it was warm even though the environment is cold and vise versa
1) enzyme conc changes= if cold increases levels in aerobic pathways
2) homeoviscous membrane adaptation = restricts membrane fluidity
3) PH regulation
4) isoform regulation= protein used at different temperatures activated for appropriate conditions

Question 19

discuss the difference in freeze tolerance and avoidance with examples

Answer 19

tolerance= the formation of ice crystals in extracellular fluid increase causing conc of water to decrease so water moves out the cell, freeze tolerance allows survival of this, for example
- frogs livers cause the breakdown of glycogen in the liver where they flood glucose molecules increasing sugar conc acting as an antifreeze (osmolyte) by decreasing freezing point

avoidance = 1) antifreeze compounds such as proteins which contain hydrophilic amino acids and sugar side chains which bind to growing is crystals preventing growth 2) supercooling= state of water where temperatures below freezing but no nucleation site for ice formation

Question 20

discuss how heat shock proteins aid survival at extreme temepratures

Answer 20

small hydrophobic proteins which bind to longer and unfolded denatured proteins, refolding them
1) HSP is bound to inactive protein HSF-1
2) sudden stress causes them to unbind and rebind to denatured protein to stabilise it
3) also activated transcription factor HSF-1 which binds to 2 other HSF-1 proteins which enters the nucleus and binds to the response element in DNA called heat shock element
4) this activates the transcription of more heat shock proteins

Question 21

Describe mechanisms for ‘gain, retain, generate, lose’ heat in achieving homeothermy in birds and mammals

Answer 21

1) gain = behaviours such as seeking the sun or warm surface as well as anatomical features such as insulation e.g. feathers

2) retain = vasocontriction, anatomic insulation e.g. feathers and blubber, behavioural insulation e.g. nest building or huddling, increased body size in colder climates to decrease SA, counter current exchangers, muscular activity e.g. shivering

3) lose- decrease insulation, vasodilation, enhanced evaporation e.g. respiratory panting or cutaneous loss, avoidance behaviour

Question 22

Discuss how the hypothalamus maintains homeothermy with respect to temperatures out of the thermal neutral zone and when and why it elevates temps to create a fever

Answer 22

acts as a thermostat in a negative feedback fashion
- must be told all the time by skin ad core temp receptors
- the posterior of the hypothalamus is activated by cold and anterior by hot signalling
Thermal neutral zone= range of enviro temps in which an animal does not need to expend energy for thermal regulation
= below TNZ= lower critical temp activates heating mechanisms and id insufficent = hypothermia
= above TNZ= upper critical temp metabolic rate increases to cool, if insufficient= hyperthermia

Question 22

what is heterothermy

Answer 22

when regulation of core temp varies between self regulation and environmental temperature; split into two categories
1) regional heterothermy
2) temporal heterothermy

Question 22

what is the difference between regional and temporal heterothermy

Answer 22

regional- animals which heat only certain regions or organs not the entire body e.g. shiver fight muscles before flying or in swordfish which have special heater organs behind their eyes to heat retinas and brain

temporal- maintain higher temps for certain periods e.g. deer mouse at night drops from 35 degrees to 20 to save energy aka torpor