AP Biology

All living systems require constant input of free energy.

Metabolism and Energy

AP Biology

The First Law of ThermodynamicsEnergy cannot be created or destroyed, only transformed.Living systems need to continually acquire and transform energy in order to remain alive. “Free energy”: The energy available in a system to do work.

AP Biology

Flow of energy through life Life is built on chemical reactions

transforming energy from one form to another

organic molecules ATP & organic molecules

organic molecules ATP & organic molecules

sun

solar energy ATP & organic molecules

AP Biology

The 2nd Law of Thermodynamics

Every time energy is transformed, the entropy (“disorder”) of the universe increases.

In order to increase/maintain their internal order, living systems must process more ordered forms of matter in to less ordered ones

AP Biology

Living Systems are “Open” SystemsMatter and energy move in to living systems from the environment. Living systems transform matter and energy and return it to the environment

AP Biology

Multi-Step Metabolism

To increase control, living systems produce free energy in multiple-step pathways, mediated by enzyme catalysts.

AP Biology

Metabolic Reactions Can form bonds between molecules

dehydration synthesis synthesis anabolic reactions ENDERGONIC

Can break bonds between molecules hydrolysis digestion catabolic reactions EXERGONIC

breaking down molecules= less organization=lower energy state

building molecules= more organization=higher energy state

AP Biology

Endergonic vs. exergonic reactionsexergonic endergonic- energy released- digestion

- energy input- synthesis

-G

G = change in free energy = ability to do work

+G

AP Biology

What drives reactions? If some reactions are “downhill”, why

don’t they just happen spontaneously? because covalent bonds are stable bonds

Stable polymersdon’t spontaneously

digest into theirmonomers

AP Biology

Getting the reaction started… Breaking down large molecules

requires an initial input of energy activation energy large biomolecules are stable must absorb energy to break bonds

energycellulose CO2 + H2O + heat

Can cells use heat to break the bonds?

AP Biology

Too much activation energy for life The amount of energy needed to

destabilize the bonds of a molecule moves the reaction over an “energy hill”

Not a match!That’s too much energy to exposeliving cells to!

AP Biology

Catalysts So what’s a cell got to do to reduce

activation energy? get help! … chemical help… ENZYMES

G

Call in the ENZYMES!

AP Biology 2005-2006

Energy needs of life Organisms are endergonic systems

What do we need energy for?

synthesis (biomolecules) reproduction active transport movement temperature regulation

AP Biology

Metabolic pathways

Work of life is done by energy coupling use exergonic (catabolic) reactions to

fuel endergonic (anabolic) reactions

+ + energy

+ energy+

AP Biology

Metabolic Strategies Temperature must be maintained for

metabolic reactions. Ectotherms vs. endotherms Body size vs. metabolic rate

Reproductive strategies optimized

AP Biology

Insufficient Free Energy Production Individual = disease or death Population = decline of a population Ecosystem = decrease in complexity

Less productivity Less energy moving

through system

AP Biology

ATP

Living economy Fueling the body’s economy

eat high energy organic molecules food = carbohydrates, lipids, proteins, nucleic acids

break them down catabolism = digest

capture released energy in a form the cell can use Uses an energy currency

a way to pass energy around need a short term energy

storage molecule

Whoa! Hot stuff!

AP Biology

ATP

high energy bondsHow efficient!Build once,use many ways

Adenosine Triphosphate modified nucleotide

nucleotide = adenine + ribose + Pi AMP

AMP + Pi ADP ADP + Pi ATP

adding phosphates is endergonic

AP Biology

How does ATP store energy?

P

O–

O–

O

–O P

O–

O–

O

–O P

O–

O–

O

–OP

O–

O–

O

–O P

O–

O–

O

–OP

O–

O–

O

–O P

O–

O–

O

–O P

O–

O–

O

–O

Each negative PO4 more difficult to add a lot of stored energy in each bond

most energy stored in 3rd Pi

3rd Pi is hardest group to keep bonded to molecule

Bonding of negative Pi groups is unstable Pi groups “pop” off easily & release energy Spring Loaded!

Instability of its P bonds makes ATP an excellent energy donor

I thinkhe’s a bitunstable…don’t you?

AMPADPATP

AP Biology

How does ATP transfer energy?

P

O–

O–

O

–O P

O–

O–

O

–O P

O–

O–

O

–O7.3energy

+P

O–

O–

O

–O

ATP ADP releases energy (exergonic)

Phosphorylation (adding phosphates!) released Pi can transfer to other molecules

destabilizing the other molecules enzyme that phosphorylates = kinase

ADPATP

AP Biology

It’snever thatsimple!

An example of Phosphorylation… Building polymers from monomers

need to destabilize the monomers phosphorylate!

C

H

OH

H

HOC C

H

O

H

C+ H2O++4.2 kcal/mol

C

H

OHC

H

P+ ATP + ADP

H

HOC+ C

H

O

H

CC

H

P+ Pi

“kinase” enzyme

-7.3 kcal/mol

-3.1 kcal/mol

enzyme

H

OHC

H

HOC

AP Biology 2005-2006

ATP / ADP cycle

A working muscle recycles over 10 million ATPs per second

Can’t store ATP too reactive transfers Pi too

easily only short term

energy storage carbs & fats are

long term energy storage

AP Biology

What’s the point? Cells spend a lot of time making ATP!

“WHY?”For chemical, mechanical,

and transport work

Make ATP! That’s all I do all day. And no one

even notices!

AP Biology

2. MATH SKILLS: GIBBS FREE ENERGY

3.1: All living systems require constant input of free energy.

Be able to use and interpret the Gibbs Free Energy Equation to determine if a particular process will occur spontaneously or non-spontaneously.

ΔG= change in free energy (- = exergonic, + =

endergonic) ΔH= change in enthalpy for the reaction

(- = exothermic, + = endothermic)T = kelvin temperatureΔS = change in entropy

(+ = entropy increase, - = entropy decrease)

What You Have To Do

Spontaneity

Spontaneous reactions continue once they are initiated. Non-spontaneous reactions require continual input of energy to continue.

Using the Equation

To use the equation, you’ll need to be given values.

Exothermic reactions that increase entropy are always spontaneous/exergonic Endothermic reactions that decrease entropy are always non-spontaneous/endergonic. Other reactions will be spontaneous or not depending on the temperature at which they occur.

Sample ProblemDetermine which of the following reactions will occur spontaneously at a temperature of 298K, justify your answer mathematically:Reaction 1:

A + B → ABΔ H: +245 KJ/molΔ S: -.02 KJ / K

Reaction 2:BC → B + C

Δ H: -334 KJ/molΔ S: +.12 KJ/K

4. MATH SKILLS: COEFFICIENT Q10

3.1: All living systems require constant input of free energy.

Be able to use and interpret the Coefficient Q10 equation:

t2 = higher temperaturet1 = lower temperaturek2= metabolic rate at higher temperaturek1= metabolic rate at lower temperatureQ10 = the factor by which the reaction rate increases when the temperature is raised by ten degrees.

What You Have To Do

Q10 tells us how a particular process will be affected by a 10 degree change in temperature.

Most biological processes have a Q10 value between 2 and 3

What It Means

Sample ProblemData taken to determine the effect of temperature on the rate of respiration in a goldfish is given in the table below. Calculate the Q10 value for this data.

Temperature (°C) Heartbeats per minute

20 18

25 42