Chapter 5 Review

1. Which of the folloing is not an organic molecule? c. water
2. Which of the following terms includes all the other terms on this list? a. polysaccharide
3. Which term is most appropriate to describe a molecule that dissolves easily in water?
c. hydrophilic
4. Cholesterol is an example of what kind of molecule? b. lipid
5. The 20 amino acids vary only in their c. amino groups
6. A specific reactant an enzyme acts upon is called the d. substrate
7. An enzyme does which of the following? b. lowers the activation energy of a reaction
Short Answer
8. Besides satisfying your hunger, why else might you consume a big bowl of pasta the night before a race?
Because pasta contains fat and starch, which is a good source of energy for storage.
9. How are glucose, sucrose, and starch related?
Starch is made up of glucose monomers. Sucrose consists of glucose and fructose.
10. What are steroids? Describe two functions they have in cells.
A steroid is a lipid molecule in which the carbon skeleton forms four fused rings. Two steroid hormones: Testosterone and estrogen contribute to major differences in the appearance and behavior f male and female mammals.
11. How are polypeptides related to proteins?
Proteins are composed of one or more polypeptide chains.
12. How does denaturation affect the ability of a protein to function?
The polypeptide chains become tangled up with one another. Heating unfolds proteins because most of the forces that maintain folding are weak attractions between pairs of side group, an between side groups and water. Since a protein's function depends on its shape, a protein that becomes denatured and loses its shape also loses its ability to work properly.

14. Analyzing Diagrams
a. One product of this reaction is represented by a question mark. Which molecule is it?
Water
b. What is this kind of reaction called? Explain.
Dehydration reaction. When a monomer is added to another monomer, a water molecule comes out.
c. If an amino acid were added to this chain, at what two places could it attach?

15. Analyzing Graphs
a. At which temperature does enzyme A perform best? Enzyme B?
38 degrees. 78 degrees.
b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came frm which organism.
Enzyme A came from humans and enzyme B came from thermophilic bacteria.
c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40 degrees.
Because every enzyme have different conditions in which they work the best. Enzyme A may not work well after 40 degrees.

Concept 5.5 Summary

To start a chemical reaction, it is first necessary to weaken chemical bonds in the reactant molecules.

*When you start a chemical reaction, you need to provide "start-up" energy called activation energy in order to activate the reactants and trigger a chemical reaction.

Ways to provide activation energy:

1. heat up the mixture of molecules

-hotter molecules may collide with enough energy to weaken bonds

-cooler molecules colide with less energy

*BUT, heating up a cell would cause many unnecessary reactions to occur at once. (and some of them will destroy the cell's delicate structures.)

2. Using enzymes

-enzymes let reactions to occur at the cell's normal temperature (unlike heating up the molecules.) by lowering the energy requirement barrier. It means that the reaction needs less activation energy.

*Enzymes don't supply activation energy to the reacting molecules.

Enzyme-the main catalysts of chemical reactions in organisms

*catalysts-compounds that speed up chemical reactions

-specialized proteins

-each enzyme catalyzes a specific kind of chemical reaction.

-each catalyze only one type of reaction because te shape of each enzyme fits the shape of only particular reactant molecules.

Substrate-a specific reactant acted upon by an enzyme.

Active site-a particular region of the enzyme where it's substrate fits into.

-A substrate binds to an enzyme at an active site. The enzyme-substrate interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakend bond insucrose, breaking sucrose into glucose and fructose.

Concept Check 5.5

1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?

Activation energy activates the reactants and triggers a chemical reaction. An enzyme let a molecule need less active energy to proceed a reaction by lowering the active energy requirement barrier in the molecule so that the reaction can proceed at normal cell temperatures.

2. Descrbie how a substrate interacts with an enzyme.

As the substrate enters, the active site changes shape slightly, fitting the substrate more snugly. ths places certain functional groups of the active site in position to catalyze the reaction. The tighter grip may also bend the substrate, weaening its bonds.

Concept 5.4 Summary

a polymer constructed from a set of just 20 kinds of monomers called amino acids.

Amino acids-each amino acid consists of a central carbon atom bonded to four partners (Hydrogen, Amino group, Carboxyl group and side group(R-group)).

*The side group is responsible for the particular chemical properties of each amino acid.

Polypeptide-it is made up of the amino acids linked together.

*Each link is created by a dehydraton reaction between the amino group of one amino acid and the carboxyl group of the next amino acid in the chain.

Proteins-made up of one or more polypeptide chains.

-a polymer constructed from a set of just 20 kinds of monomers called amino acids.

Denaturation-An unfavorable change in temprature, pH, or some other quality of the environment can cause a protein to unravel and loose its normal shape. the function of it has been destroyed as the shape of it has been destroyed.

Concept Check 5.4

1. Give at least two examples of proteins you can "see" in the world around you. What are their functions?

Cheese and egg. Help us to grow and repair.

2. Relate amino acids, polypeptides, and proteins.

Polypeptides are made up of amino acids linked to each other, and proteins are made up of one or more polypeptides.

3. Explain how heat can destroy a protein.

Heating unfolds proteins because most of the forces that maintain folding are weeak attractions between pairs of side groups, and between side groups and water. Hot molecules collide with enough force to overcome these weak attractions.

4. Which parts of an amino acid's strcture are the same in all amino acids? Which part is unique?

The hydrogen atom, the amino group and the carboxyl group. The side group part is unique.

Concept 5.3 Summary

Characteristic of Lipids:
Hydrophobic-water-fearing or water-avoiding

A fat consists of a three-carbon backbone called glycerol attached to three fatty acids, which contain long hydrocarbon chains.

*Some fats are solid at room temperature, other fats called oils are liquids at room temperature.

Two kinds of Fat:
1. Saturated fat-a fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms. *It is solid in room temperature.
2. Unsturated fat-a fat that one or more of its fatty acid chains contains less than the maximum number of hydrogen atoms because some of its carbon atoms are double-bonded to each other.

Steroids-a lipid molecule in which the carbon skeleton forms four fused rings.
* The best-knkown steroid is Cholesterol.
Cholesterol-an esential molecule found in the membranes that surround your cells.
*It is also the starting point from which your body produces other steroids.

Concept Check 5.3:
1. What property do lipids share?
Hydrophobic(water-fearing).

2. What are the parts of a fat molecule?
A fat consists of a three-carbon backbone called glycerol attached to three fatty acids(containing long hydrocarbon chains) and if all three fatty acid chains contain the maximum possible hydrogen number, it is saturated. If one or more of three fatty acid chains contain less than the maximum hydrogen number, it is unsaturated.

3. Describe two ways that steroids differ from fats.
1. All steroids have a core set of four rings.
2. Some steroids circulate in your ody as chemial signals.

4. What does the term unsaturated fat on a food label mean?
An unsaturated fat contains less than the maximum number of hydrogen atoms in one or more of its fatty acid chains because soe of its carbon atoms are double-bonded to each other.
The fats in fruits, vegetales, and fish are generally unsaturated, as are crn oil, olive oil, and other vegetabl oils.

Concept 5.1 Summary

Molecules consist of Carbon=organic molecules e.g: CO2

Molecules do not consist of Carbon=inorganic molecules e.g: H2O, O2

Hydrocarbons ONLY consist of carbon and hydrogen (most of them are fuels such as Methane-CH4).

Different shapes of the carbon backbones:


Straight chain Branched chain



*Each carbon forms four bonds at maximum.

Four common functional groups:
Hydroxyl group(hydrophilic), Carbonyl group, Carboxyl group, Amino group (from up to bottom)


*Together, the carbon skeleton and the attached functional groups determine the properties of an organic molecule.


Polymers are long chains made up of monomers.


Four main categories of life's large molecules:
1. carbohydrates
2. lipids
3. proteins
4. nucleic acids


Dehydration reaction:

• a monomer is added to a chain,
• it removes one water molecule,
• a new bond is formed.

Hydrolysis reaction:

• a water molecule is added to a chain-it breaks a bond beween two monomers.

Concept Check 5.1

1. Draw a molecule that has a three -carbon skeleton and a hydroxyl group on the middle carbone. (Hint: The molecule's formula is C3H8O.)



2. Explain the connection between monomers and polymers.
   Monomers link together into long chains to make a polymer.
   
3. What molecule is released during construction of a polymer? What is this reaction called?
A water molecule is released during construction of a polymer. It is called a dehydration reaction.


4. Draw at least three ways in which five carbon atoms could be joined to make different carbon skeletons.

Concept 5.2 Summary

Carbohydrate-an organic compound made up of sugar molecules (containing carbon, hydrogen and oxygen in the ratio of 1:2:1).
-most of carbohydrates are hydrophilic

Different Types of Sugar:
1. Monosaccharides-simple sugars containing just one sugar unit.
examples: glucose, fructose, galactose (sugar names end in the suffix -ose)

2. Disaccharides-made up by two monosaccharides (double sugar).
-formed by the dehydration reaction.
example: sucrose
*Sucrose consists of one glucose molecule and a fructose molecule linked together.

3. Polysaccharide-a long polymer chain made up of simple sugar monomers (complex charbohydrates)

Examples of polysaccharides:
1. starch-found in plant cells
-a chain of many glucose monomers
* The stored glucose in the starch molecules become available when those molecules are broken down or digested.
2. glycogen-a chain of many glucose monomers
-more highly branched than a starch polymer
-stored as granules in liver and muscle cells in humans (it breaks down to release energy when the body needs energy)
3. cellulose(also called fiber)-a chain of many glucose monomers
-multiple cellulose chains are linked together with hydrogen bonds
* Most animals (including humans) cannot digest cellulose because they lack the molecule necessary to break the bonds between the glucose monomers in cellulose. Therefore, it just passes through our digestive system, helps keeping it healthy, BUT, does not serve as a nutrient.

Concet Check 5.2
1. Explain the difference between a monosaccharide and a disaccharide. Give an example of each.
A monosaccharide is a simple sugar containing just one sugar unit. Example:glucose
A disaccharide is made up of two monosaccharides. Example:sucrose

2. Compare and contrast starch, glycogen, and cellulose.
Starch is mostly found in plants. A glycogen polymer is more highly branched than a starch polymer. A cellulose can't be digested in human and most of the animal bodies.

3. How do animals store excess glucose molecules?
The glucose molecules are stored in the form of a polysaccharide called glycogen. In humans, most glycogen is stored as granules in liverand muscle cells. When the body needs energy, itbreaks dwon these glycogen granules, releasing glucose.