The digestive system, thermodynamics,
enzymes, and transport across membranes
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April 28, 2003
Learning objectives
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Understand the major organs involved in the digestive
system
Understand the molecular difference between sugars and
lipids
Understand how enzymes break down complex molecules to
derive energy
ATP is the energy currency of the cell
Understand how complex molecules are built up and know
that this is an energy-requiring process
Workshop-Work in groups to report on some aspect
of digestion
Homework-see last slide
Grading
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6
1
1
1
6
Quizzes (15%), Homework (10%),
Midterm (25%), Writing assignment
(15%), Final Exam (35%)
Quizzes (each 10 points) = 60
Midterm
= 100
paper
= 60
final
= 140
homeworks (ea. 6.67)
= 40
Total
= 400
points
points
points
points
points
points
6
5
1
4
3
2
H
(ATP)
(warmth)
First Law of Thermodynamics-Energy cannot be created
or destroyed but it can change form.
Second Law of Thermodynamics-Systems change in a way
that increases disorder of the system and its surroundings
+ 6O2 + ADP + Pi
6CO2 + 6H2O + ATP
+ heat energy
•Enzyme action video 1
•Enzyme action video 2
•Enzyme action video 3
Characteristics of enzymes
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Globular proteins that function as biological catalysts
to mediate specific biochemical chemical reactions
Enzymes are not changed by the reactions they
mediate
Functional units of metabolism - responsible for all
biochemical reactions
May require cofactors/coenzymes for reaction to occur
metal ions - e.g., Mn2+, Zn2+, Fe3+
coenzymes (NAD+, TPP, THF, etc.)
Characteristics of enzymes
(cont.)
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Apoenzyme - enzyme lacking essential
cofactor
Holoenzyme - intact & functional enzyme
containing all cofactors/coenzymes
Substrate (S) - molecules that enzymes react
with
Product (P) - molecules formed by enzymemediated reactions
Obesity in America
What is a calorie?
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The calorie (symbolized cal) is the unit of heat
Heat is a form of kinetic energy transfer from
one medium or object to another. An energy
transfer of 1 cal will raise the temperature of
one gram (1 g) of pure liquid water by one
degree Celsius (1 oC)
In nutrition, a unit called the diet calorie is
sometimes mentioned; this unit is equivalent to
1000 cal, or one kilocalorie (1 kcal).
Calorie content is measured with a bomb
colorimeter
H
Workshop
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Work in assigned groups of two
to give a 6 minute presentation
to the class on a molecular
aspect of human digestion
prepare a 3 question quiz for
the class
Starch hydrolysis
Protein digestion
Fat emulsification
Websites on human
digestive system
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Site 1
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Site 2
Types of transport
1.
2.
3.
Passive-requires no energy
Facilitated-requires no energy
(put needs a protein transporter)
Active transport-requires energy
Video on transport systems
Endocytosis vs. exocytosis
Do the following exercises
Homework Due May 5
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Answer Reviewing Ideas on p. 74, problems
1, 2, 5-9, 11; Using Concepts on p. 75,
problems 2, 3, 6, 8, 10
Answer Check and Challenge questions on p.
85
Reading for next week: 226-229; and
familiarize yourself with the following website:
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call
=bv.View..ShowSection&rid=gnd