The digestive system, thermodynamics, enzymes, and transport across membranes

April 28, 2003 Learning objectives-

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 Quizzes (15%), Homework (10%),

Midterm (25%), Writing assignment (15%), Final Exam (35%)

6 Quizzes (each 10 points) = 60 points1 Midterm                 = 100 points1 paper                    = 60 points1 final                   = 140 points6 homeworks (ea.  6.67) = 40 points  Total                   = 400 points

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23

4

56

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(ATP) (warmth)

First Law of Thermodynamics-Energy cannot be createdor destroyed but it can change form.

Second Law of Thermodynamics-Systems change in a way that increases disorder of the system and its surroundings

6CO2 + 6H2O + ATP

+ heat energy

+ 6O2 + ADP + Pi

•Enzyme action video 1•Enzyme action video 2•Enzyme action video 3

Characteristics of enzymes 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.)

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 enzyme-mediated reactions

Obesity in America

What is a calorie? 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

Site 1

Websites on human digestive system

Site 2

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

Types of transport

1. Passive-requires no energy2. Facilitated-requires no energy

(put needs a protein transporter)3. Active transport-requires energy

Video on transport systems

Endocytosis vs. exocytosis

Do the following exercises

Homework Due May 5 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