Questions (Set One)

p.106 1~12
1. Which of the following is not an organic molecule?
a)cellulose
b)sucrose
c)water
d)testosterone

2. Which of the following terms includes all the other terms on this list?
a)polysaccharide
b)carbohydrate
c)monosaccharide
d)glycogen

3. Which term is most appropriate to describe a molecules that dissolves easily in water?
a)hydrocarbon
b)hydrophobic
c)hydrophilic
d)organic

4. Cholesterol is an example of what kind of molecule?
a)protein
b)lipid
c)amino groups
d)lipid groups

5. The 20 amino acids vary only in their
a)carboxyl group
b)side groups
c)amino groups
d)lipid groups

6. A specific reactant an enzyme acts upon is called the
a)catalyst
b)sucrase
c)active site
d)subtrate

7. An enzyme does which of the following
a)adds heat to a reaction, speeding it up
b)lowers the activation energy of a reaction
c)cools a reaction, slowing it down
d)raises the activation energy of the reaction

8. Besides satisfying your hunger, why else mights you consume a big bowl of pasta the night before a race? Another reason why people may consume pasta the night before a race is to store sugar stockpiles (potential energy). When the body needs this energy, it will break down the stored sugar and use the energy.

9. How are glucose, sucrose, and starch related?
Glucose, sucrose, and starch are related because they are all sugars. Sucrose is formed from a glucose monomer connected with a fructose monomer. Starch is a polysaccharide that is formed by many glucose molecules.

10. What are steroids? Describe two functions they have in cells.
A steroid is a lipid with a carbon skeleton of four fused rings. One way in which steroids function in cells is through giving chemical signals throughout the body. Another function is that a certain kind of steroid called cholesterol is part of the membrane that surrounds our cells.

11. How are polypeptides related to proteins?
Proteins consist of one or more polypeptide chains. These chains are formed from a combination of amino acids.

12. How does denaturation affect the ability of a protein to function?
Denaturation affects the ability of a protein to function by causing the protein to either not function well, or not function at all.

p.107 14~15
14.
a) The one product represented with a question mark is a water molecule.
b)This kind of reaction is called a dehydration reaction because in order for the two amino acids to bond, a water molecule is removed.
c)If amino acids were added to this chain, the two places in which they could be attached would be to the OH molecules.

15.
a)At about 39 degrees enzyme A performs the best.
b)I would hypothesize that enzyme A is found in humans because the temperature range in which it performs well is about the average human temperature.
c)If the temperature rises above 40 degrees, then denaturation of the enzyme occurs, causing the rate of the reaction catalyzed by the enzyme to slow down.

Summary 5.5

In order to start a chemical reaction the chemical bonds in the reactant molecules have to be weakened. In this process it is required that energy is absorbed by the molecules. This "start-up" energy is referred to as activation energy, as it is the energy that activates the reactants and initiates a chemical reaction.

Cellular reactions rely on catalysts, compounds that speed up reactions. In the chemical reactions of organisms the main catalysts are specials proteins called enzymes. Enzymes do not supply activation energy, but lower the the energy required to start a reaction; thus, allowing reactions to occur faster at room temperature. Specific enzymes cause specific kinds of chemical reactions.

• if enzymes were to supply activation energy, the tempertaure would increase
  
• the lower the energy required to start a chemical reaction, the faster and more possibly it can occur
  

An enzyme catalyzes only one kind of reaction. The reason for this is that shape of each enzyme only fits the particular shape of reactant molecules. Furthermore, the reactant that is acted upon by the enzyme is defined as the enzyme's subtrate. The specific region in which the subtrate fits into is the activate site. The subratate's fit into the enzyme is not rigid. When a subtrate enters an enyzme, the enzyme slightly changes shape in order to fit the subrate snuggly.

Another way in which enzymes lower the activation energy is by accepting two subrates in adjacent areas. The holding of reactants together enables them to react more easily. Through this process, enzymes can catalyze the making of larger molecules from smaller molecules. Just like any protein, an enzyme's shape and structure are crucial to its functin. Furthermore, factors such as pH and temperature change can affect how an enzyme works, or if it works at all.

Concept Check

1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? The role of activation energy in a reaction is that this is the initial energy with which a reaction starts. This energy activates reactants to start a chemical reaction. An enzyme lowers the activation energy, thus speeding up the chemical reaction.

2. Describe how a subtrate interacts with an enyzme. A subtrate interacts with an enzyme by entering the active site of the enzyme. The fit between the subtrate and the enzyme is not rigid, but instead the enzyme's active sight slightly changes shape to fit the subtrate.

Summary 5.4

Proteins execute most of the functions in cells. A protein is a polymer that is built up from a set of 20 kinds of monomers called amino acids. Furthermore, proteins play an important role in many of our daily functions; such as proteins that form hair, make up muscle, etc.

Amino Acid:
-monomer that consists of a central carbon atom, bonded to four other partners
-three of these four partners are common to all amino acids (amino group, carboxyl group, and hydrogen atom)
-the last group is the side group (AKA the "R-group), which determines the particular chemical properties of an amino acid

Long chains of amino acids linked together are called a polypeptide. Each link between the amino acids is connected through the process of dehydration. Proteins are created from one or more polypeptide chains. By arranging different amino acids into different orders, the body can compose an enormous variety of proteins. Every protein has a unique amino acid sequence.

Every protein is a series of precisely coiled, twisted, and folded polypeptides. The answer to how the proteins fold in the exact way is not fully understood. Certain side groups bond with others, which helps to fold polypeptides and to keep them folded. A protein is also affected by its environment, which in usual circumstances is aqueous. Thus, the hydrophillic amino acids tend to move to the edges of the protein, while the hydrophobic amino acids cluster in the middle.

When a protein undergoes unfavorable changes in temperature, pH, and other qualities, it could cause the protein to unravel and lose its shape; this process is called denaturation. Heating causes proteins to unfold because it breaks apart the weak bonds between side groups, and between side groups and water. After a protein goes through denaturation, it loses its power to function properly.

Concept Check

1.Give at least two examples of proteins you can "see" in the world around you. What are their functions? Two proteins that I can see are the proteins that make up fur, hair, and muscles. The function of fur is to keep animals warm, and muscles are used to perform daily things, such as moving and eating.

2.Relate amino acids, polypeptides, and proteins. Polypeptides (polymers) are longs chains of amino acids (monomers), and these polypeptides form in specific folds creating proteins.

3.Explain how heat can destroy a protein. Heat can destroy a protein by overcoming the weak bonds that are between the side groups, and between the side groups and water. Once this occurs, it changes the shape of the protein, and causes it not to function well.

4.Which parts of an amino acid's structure are the same in all amino acids? Which part is unique? The parts of an amino acid's structure that are the same in all amino acids are the carboxyl group, the amino group, and the hydrogen atom. The unique part is the side group, which determines the particular chemical properties of the amino acid.

Summary 5.3

Lipids play an important role in our bodies. In more detail, lipids are also compounds that avoid water. The term used for water-avoiding molecules is hydrophobic (water-fearing). Lipids surround and contain the watery contents of our cells, circulate in our bodies and send chemical signals to cells, and store energy in our bodies.

A fat is made up of a three-carbon backbone, glycerol, which is attached to three fatty acids (long hydrocarbon chains). A saturated fat is a fat in which all its three fatty acid chains have the maximum number of hydrogen atoms. In contrast, an unsaturated fat has one or more fatty acid chains with molecules that don't bond with the maximum possible number of hydrogen atoms.

• diets high in saturated fat could be unhealthy
• lipid containing deposits may form (plaques), attaching to blood vessels walls, which may reduce the blood flow and cause heart disease

Steroids are another type of lipid. Steroid molecules are formed from carbon skeletons which make four fused rings. Although steroids are classified as lipids (since they are hydrophobic), they are very different in structure and function from fats. Certain steroids circulate around the body as chemical signs. A commonly known steroid is cholesterol. This steroid is an essential molecule as it is part of the membranes that surround your cells. Cholesterol often has a bad image, since high levels of specific cholesterol-containing substances are linked to cardiovascular disease.

Concept Check

1.What property do lipids share? The property that lipids share is that they are hydrophobic.

2.What are the parts of a fat molecule? The parts of a fat molecule are the glycerol (three-carbon backbone), and the three fatty acids attached to it.

3.Describe two ways that steroids differ from fat.
a)steroids differ from fats in the way they are structured in a four fused ring, while fats are structured with a three-carbon backbone, with three fatty acids attached to it.
b)steroids differ from fats in that steroids circulate in our bodies as chemical signals.

4.What does the term unsaturated fat on a food label mean? The term unsaturated fat on a food label means that the fat within the food have less than the maximum possible number of hydrogen atoms. Unsaturated fat foods are probably more healthy than saturated fat foods.