"You are what you eat" is a popular refrain that is, in a strictly biological sense, true.  We are the proteins, fats, carbohydrates, vitamins and minerals that we eat and a large percentage of our body is made up of the water that we drink and that is in the food that we eat.

To the biologist, proteins are the most fascinating macro nutrient within our bodies.  Our lives depend on them as antibodies to fight foreign invaders, as antigens to distinguish self from non-self, as the scaffolding for skin, bones and cartilage, as the hair and nails that cover and protect our bodies and, of course, as enzymes.  As we learned in the previous assignment, enzymes are crucial for all cellular functions.  They are the workhorses of our cells.

In this assignment we will learn how proteins are assembled from the information found in DNA.  We will then learn how the coordinating digestive and excretory systems work in concert to break down and absorb the nutrients that we need and filter out the by-products and toxins that would do harm to our bodies.

PART I:  PRINCIPLES, UNIT 2   GENETICS
    DNA:  The Genetic Material

•8-1  Identifying the Genetic Material:  "You resemble your parents because you have copies of their chromosomes, which contain sets of instructions called genes…What are genes made of?  Scientists believed that if they could answer this question they would understand how chromosomes function as the bearers of heredity."

**ANSWER:  If you did not do the Master Molecules (Griffith dry lab) answer the questions, reviewing this lab, on page 168.

•8-2  The Structure of DNA:  "By the early 1950’s, most scientists were convinced that genes were made of DNA.  They began studying DNA in earnest, hoping that the mystery of heredity could be solved by understanding the structure of the molecule."

**ANSWER:  Page 173  #1-6

•8-3  The Structure of a Gene:  "Ever since it became clear that DNA is the hereditary material of the cell, scientists have peered ever more closely at DNA in an attempt to learn more about genes.  New questions revolved around the nature of the information held in the DNA molecule.  Scientists soon learned that genes hold information specifying how to build particular proteins.  Remember that a protein is a string of amino acids.  Each amino acid is coded for in the DNA.  A gene affects the phenotype of an individual because of the activity of the protein that it specifies.  If the protein is an enzyme that makes brown pigment, then the gene may affect hair color.  Simply stated, genes are the DNA-encoded information that specifies particular proteins;  each gene is made of a specific sequence of nucleotides."

**ANSWER:  page 176,  #1
Chapter Review:  Multiple choice  #1-7 and 9
Short Answer #18, 19, 22
Themes Review, #26, 27
Critical Thinking #30, 31

Films:  DNA:  Lab of Life
 

EXPERIMENTAL: DNA replication simulation

PART I:  PRINCIPLES, UNIT 2  GENETICS
    Gene Expression

Read:  Chapter 9 Gene Expression (omit section 2)

Themes in this chapter:
1. "Homeostasis:  Cells waste energy if they constantly transcribe every gene.  Genes are often turned off in cells unless the protein the genes produce is needed.  Feedback systems regulate which genes are turned on and which genes are turned off in a cell;  thus, feedback systems prevent overproduction of unnecessary protein in the cell.  If viruses or environmental agents alter feedback systems, cancers can result.
2. Structure and Function:  Control of gene expression is required for cells to become specialized.  Liver cells differ from brain cells because different genes are expressed within different cells.  Gene regulation allows cells to differentiate in the early developmental stages of an organism."

**ANSWER:  page 189 #1,2 and 5
Chapter Review:  Multiple choice #1-4 and 9
Short answer #17, 22, 26
During protein synthesis, a polypeptide is made by linking amino acids.  What kind of bonds are formed between amino acids?
What must still be done to this peptide chain to make a functional protein?

Films:  Genetic Engineering and Protein Synthesis
 

EXPERIMENT:  Protein Synthesis Kits

 

PART II:  EXPLORATION, UNIT 9 EXPLORING HUMAN BIOLOGY
    Digestive System

•38-1  Diet:  What We Need to Eat and Why  "You obtain energy from the foods you eat to fuel your every activity…The energy in food is stored in its chemical bonds…your cells break the chemical bonds of food molecules and harvest their energy to make ATP.  In addition to providing energy, the food you eat provides raw materials that your body uses to manufacture molecules for its own use…Every molecule in your body, every hair and bone and cell, is built from raw materials that come from food you ate."

••Fill in columns 2 and 3 in the Nutrition/Digestion Table.

NUTRITION/ DIGESTION TABLE
 

Nutrient	Uses In Body	End Product of Digestion
Carbohydrate	1. 2. 3.
Protein	1. 2. 3. 4. 5. 6. 7.
Fat	1. 2. 3.
Vitamins
Minerals
Water

**ANSWER:  page 903:  # 1 and 2
Why is a extremely low fat diet dangerous, especially for young children and teenagers?

•38-2  Digestion  "Your cells obtain the energy they need by extracting it from sugars, fatty acids, and amino acids during cellular respiration…Your cells cannot extract energy from these large chains.  First, these large molecules must be broken down into their individual components during a process called digestion."

••Study  the diagrams and descriptions on pages 651, 670, 672 and 691.

**ANSWSER:  page 909:  #4
Compare digestion in a flatworm and an earthworm.
 

EXPERIMENT:  Fat Digestion

PART II:  EXPLORATION, UNIT 8  VERTEBRATES and UNIT 9  HUMAN BIOLOGY
    Excretory System

•31-4  Challenge of Retaining Water  "Vertebrates evolved in water.  Though vertebrates now also live on land, no vertebrate can do without water for long…Preventing dehydration has been a key evolutionary challenge facing vertebrates in all environments."

**ANSWER:  page 726:  #2 and 3
Unlike other organisms, reptiles and birds can lay eggs on land.  Explain why this is true.
Explain how flame cells work and where they are found.

•38-3  Excretion  "If you live to be 70 years old, you will, in the course of your life, eat some 45,000 pounds of food and drink over 7,250 gallons of fluid—enough to fill a tanker truck.  Did you ever wonder what happens to all of this food and fluid?  Every atom of it still exists, if not in your body, then in the wastes that have been eliminated from it.  Humans eliminate wastes in a process called excretion."

**ANSWER:  Explain how filtration and reabsorption work in the human kidney (page 910-915) and help maintain homeostasis.
 

EXPERIMENT:  Size of Molecules

 

Note:  All quotations are taken from Raven and Johnson
 

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