temperature and principles of heat exchange - exam 4

temperature

measure or kinetic energy of an atom or molecule

heat

the energy that matter possesses due to the random motions of atoms and molecules

random motion

molecules in a gas or soln undergo this type of motion → this is directly related to the kinetic energy of those molecules

thermoregulation

refers to strategies used by animals to manage their heat balance to maintain preferred body temps

• can do this two ways: internal mechanisms or behaviors

chemical reactions

take place when molecules (reactants) collide with one another with enough kinetic energy

• if an increase in temperature is an increase in kinetic energy, then molecules will collide with one another sooner, speeding up the rate of chemical reactions (simple probability)

activation energy

energy needed for a reaction to take place when reactants collide

how to increase probability of a reaction taking place

1. increase probability of reactants colliding

2. increase energy inherent to reactants (i.e., increase speed at which they are moving/kinetic energy - then more are above E_a)

3. enzymes (lower E_a, nothing to do with temp)

reaction rate

refers to the number of reactions that occur in a given time period

Q₁₀

describes how a reaction changes over a 10°C change in temperature

• if Q₁₀ is “2”, then the rxn rate doubles over a 10°C change

• true regardless of 10°C change (5 - 15°C or 20 - 30°C)

• when it is not true…something else is going on…something beyond the effects of activation energy

biochemical reactions

refers to more than just a chemical reactions, but chemical reactions behind biological processes

• it could be a series of reactions referred to as a metabolic pathway

• rxns increase with increasing temperature but typically start to decrease at a transition point

transition point causes

1. effect on protein structures (enzyme denaturing)

2. breakdown of metabolic pathways

3. effect on lipid bilayer (fluidity affected by temp)

eurythermal

larger range of temperature tolerance

stenothermal

narrow range of temperature tolerance

critical thermal maximum

species have upper lethal limits when they stop functioning

temperature effect on protein structures

slight changes in amino acid sequence lead to big effects on temperature sensitivity and stability

• heat shock proteins: “chaperones” refold denatured proteins (only work to a certain extent)

breakdown of metabolic pathways

different enzymes have different Q₁₀ values

• demand for one enzyme may surpass reaction rates of prior enzymes

temperature effect on lipid bilayer

fluid → transmembrane proteins can move around

• changing permeability will change way transmembrane proteins work and can break them apart

critical thermal minimum

death due to low temperatures typically due to:

1. ice formation in cells

2. metabolic pathway disruptions

3. biological functions slow beyond ability to maintain critical processes (breathing rate, heart rate, etc…)

general principles of heat exchange

heat can be exchanged via 4 main pathways:

1. radiation

2. conduction

3. convection

4. evaporation

first three methods help move heat from the body to the environment (works in both directions)

• when critical thermal maximum is exceeded by environment, organisms will dump heat via evaporation

radiation

all objects emit/radiate heat from their body (known as electromagnetic radiation)

• emissivity - directly proportional to how well something absorbs radiation

emissivity

measure of how well something emits radiation → directly proportional to how well something absorbs radiation

conduction

heat flow between two objects (solids) in contact with one another

• rate of heat flow will change from object to boject

• insulation

conduction equation

Q = k((T1-T2)*A / d)

• k describes the thermal conductivity: increasing k will increase rate of heat movement

insulation

describes resistance to conducting heat

convection

fluid medium surrounding animal is not stationary → conduction is similar to this, but the opposite side of the gradient keeps moving

• maintains a large gradient (new medium constantly coming in)

• free vs forced convection

evaporation

energy needed to transform liquid water into water vapor (latent heat of vaporization)

• thus, water loss also pulls heat from the body