Energy and food

Copyright 2009 President and Fellows of Harvard College... Reactions that absorb energy are calledLife Sciences-HHMI Outreach.. Copyright 2009 President and Fellows of Harvard College...

Summer 2009 Workshop

in Biology and Multimedia for High School Teachers

• Energy is a critical part of your

everyday life.

• Energy is either released or

absorbed in a chemical reaction

This occurs when the bonds

between the atoms are broken

and then the atoms rearranged.

• The food you eat is the fuel which

will provide the energy you need

to sustain life.

Life Sciences-HHMI Outreach Copyright 2009 President and Fellows of Harvard College

http://en.wikipedia.org/wiki/File:MyPyramidFood.svg

Reactions that absorb energy are called

Life Sciences-HHMI Outreach Copyright 2009 President and Fellows of Harvard College

Reactions that

release energy are

called

http://en.wikipedia.org/wiki/File:ThermiteFe2O3.JPG

the human body.

Life Sciences-HHMI Outreach Copyright 2009 President and Fellows of Harvard College

http://www.whfoods.com/genpage.php?tname=faq&dbid=16

Look

http://en.wikipedia.org/wiki/File:Macaca_arctoides.pn g

Metabolism refers to all the chemical reactions within an organism that breakdown molecules to release energy and all the reactions that use energy to build complex

molecules These reactions are referred to as

RELEASE

ENERGY

ABSORB ENERGY

When we speak of

energy we are talking ….

Catabolism is the process

where larger molecules are

broken down into smaller

molecules releasing energy

The molecules are broken

down into either simple

sugars, glycerol and fatty acids

or amino acids This process is

exothermic

http:// commons.wikimedia.org/wiki/File:Catabolism.svg http://commons.wikimedia.org/wiki/File:FlameV1.png

Anabolism is the process

where smaller molecules are

combined to form larger more

complex molecules This

process requires energy so it

is considered an

endothermic reaction

Life Sciences-HHMI Outreach Copyright 2009 President and Fellows of Harvard College

http://commons.wikimedia.org/wiki/File:Peptidbinding.svg

The change in energy is measured in

terms of heat The amount of energy

(heat) that is contained within the

bonds of the reactants is compared to

the amount of energy (heat) that is

contained within the bonds of the

products This is referred to as the

H

This symbol means the difference in Enthalpy.

ENTHALPY

• Endothermic reactions always have a positive H.

• Exothermic reactions always have a negative H.

• Enthalpy changes that are measured when reactants are in their standard states are called STANDARD ENTHALPY CHANGES.

• STANDARD ENTHALPIES are denoted by ∆ H˚ Standard states are at 25˚ C and 1 atm of pressure.

• The enthalpy change in a reaction is directly related to the amount of reactants.

Life Sciences-HHMI Outreach Copyright 2009 President and Fellows of Harvard College

Hess’s Law

states that if a series of

reactions are added together,

the enthalpy change for the

net reaction is the same as the

sum of the individual reactions

Huh?

More simply put:

2+2=4

is the same as 1+1+1+1=4

• The subject of calorimetry studies the flow of heat and heat

measurements.

• Every object has the ability to absorb heat The amount of heat that

is absorbed is referred to as the heat capacity.

• The heat capacity is the amount of heat required to raise the temperature by 1˚C.

• The heat capacity depends on the composition and the amount of the substance,

Life Sciences-HHMI Outreach Copyright 2009 President and Fellows of Harvard College

The heat capacity of one gram of a substance is referred to as the

SPECIFIC HEAT.

The specific heat of

• Kilocalories are used in

nutrition.

• Calorimeters are used to

figure out the calories in food

sources.

https://vinstan.wikispaces.com/file/view/calorimeter.PNG

• The catabolism of food is an oxidative reaction.

• Most of our energy comes from Calories found in fat and sugar