Chapter 5 Review Assessment

Reviewing Concepts Multiple Choice: Choose the letter of the best answer.

1. Which of the following is not an organic molecule? answer: c.water

a. cellulose

b. sucrose

c. water

d. testosterone

2. Which of the following terms includes all the other terms on this list? answer: b.carbohydrate

a. polysaccharide

b. carbohydrate

c. monosaccharide

d. glycogen

3. Which term is most appropriate to describe a molecule that dissolves easily in water? answer: c. hydrophilic

a. hydrocarbon

b. hydrophobic

c. hydrophilic

d. organic

4. Cholesterol is an example of what kind of molecule? answer: b. lipid

a. protein

b. lipid

c. amino acid

d. carbohydrate

5. The 20 amino acids vary only in their answer: c. amino groups

a. carboxyl groups.

b. side groups.

c. amino groups.

d. lipid groups.

6. A specific reactant an enzyme acts upon is called the answer: d. substrate

a. catalyst.

b. sucrose.

c. active site.

d. substrate.

7. An enzyme does which of the following? answer: b. lowers the activation energy of a reaction

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 a reaction

Short Answer

8. Besides satisfying your hunger, why else might you consume a big bowl of pasta the night before a race?

Not enough having carbons in body or proteins and fats that you need for each day.

9. How are glucose, sucrose, and starch related?

They are all in polysaccharides and they have different functions.

10. What are steroids? Describe two functions they have in cells.

Steroids are lipid molecule with four fused carbon rings. They work at both male's and female's sex hormone, and testosterone.

11. How are polypeptides related to proteins?

Because each links in the proteins are made out of several polypeptides formed together.

12. How does denaturation affect the ability of a protein to function?

Denaturation unfavorable changes in temperature, pH, or some other quality of the enviornment can cause a protein to unravel and lose its normal shape.

Applying Concepts Analyzing Information

14. Analyzing Diagrams The reaction below shows two amino acids joining together.

a. One product of this reaction is represented by a question mark. Which molecule is it?

b. What is this kind of reaction called? Explain.

c. If an amino acid were added to this chain, at what two places could it attach?

15. Analyzing Graphs Use the graph to answer the questions below.

a. At which temperature does enzyme A perform best? Enzyme B?

b. Knowing that one of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria, hypothesize which enzyme came from which organism.

c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C.

Summary of 5.5

CONCEPT 5.5: Enzymes are proteins that speed up specific reactions in cells.


Key Terms:

activation energy -- minimum amount of energy required to trigger a chemical reaction
catalyst -- compounds that speed up chemical reactions
enzyme -- the main catalysts of chemical reactions in organisms are specialized proteins
substrate -- a specific reactant acted upon by an enzyme
active site -- the substrate of its into a particular region of the enzyme


Summary:

Enzymes and Activation Energy
* to start a chemical reaction
- need to weaken chemical bonds in the reactant molecules first
--requires molecules absorb energy
--- "start-up" energy for chemical reaction - activation energy
* heat up the mixture of molecules - providing activation energy
- hotter molecules may collide with enough energy to weaken bonds
- cooler molecules collide with less energy
* heating up a cell would cause many unnecessary reactions to occur at once
- cellular reactions depend of the assistance of catalysts
-- main catalysts of chemical reactions in organisms are enzymes
* enzymes doesn't supply activation energy to the reacting molecules
- lowers the energy requirement barrier so that the reaction can proceed at normal cell temperatures
* figure 5-15: enzyme lowers the wall so that frogs have enough energy to reach the other side.


Concept:

1. Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?
Activation energy is a "start-up" energy for starting a chemical reaction. Enzymes affect on activation energy when a cell got heat up and cause many unnecessary reactions to occur at once, including reactions that destroy the cell's delicate structures.


2. Describe how a substrate interacts with an enzyme.
The fit between substrate and enzyme is not rigid. When the substrate enter the enzyme, active site changes shape sligthly which makes fitting substrate more fitly.

Summary of 5.4

CONCEPT 5.4: Proteins perform most functions in cells.


Key Terms:

protein -- a polymer constructed from a set of just 20 kinds of monomers called amino acids
amino acid -- monomer that makes up proteins; contains carboxy and amino functional groups
polypeptide -- cell create proteins by linking amino acids together into a chain
denaturation -- loss of normal shape of a protein due to heat or other factor


Notes:

The Functions of Proteins
* proteins are responsible for almost all of the day-to-day functioning of organisms
* proteins with less-visible functions defend the body from harmful small molecules, and other that act as signals, conveying messages from one cell to another


Amino Acids
* three of the central carbon's partners are the same in all amino acids
* the side group is responsible for each amino acid
- ex. side group of the amino acid - leucine = hydrocarbon

Building a Protein
* need a lot of amino acids to build up a protein


Protein Shape
* An unfavorable change in temperature, pH, or some other quality of the environment can cause a protein to unravel and lose its normal shape (denaturation)



Concept Check 5.4

1. Give at least two examples of proteins you can "see" in the world around you. What are their functions?
animals, and plants; proteins are responsible during everyday functioning organisms.

2. Relate amino acids, polypeptides, and proteins.
They are all made out of a lot of molecules, and they all support the living things tfor do their works.


3. Explain how heat can destroy a protein.



4. Which part of an anmino acid's structure are the same in all amino acids? Which part is uniques?

Summary of 5.3

CONCEPT 5.3: Lipids include fats and steroids


Key Terms:


lipid -- oil's inability to mix with water is typical of the class of water avoiding compounds
hydrophobic -- water-avoiding molecules

saturated fat -- fat in which all three fatty acid chains contain the maximum possible number of hydrogen atoms

unsaturated fats -- contain less than the maximum number of hydrogen atoms in one or more of it's fatty acid chains because some of it's carbon atoms are double-bonded to each other

steroid -- a lipid molecule in which the carbon skeleton forms four fused rings

cholesterol -- essential molecule found in the membranes that surround your cells


Notes:

Characteristics of Lipids


* hydrophobic - "water-fearing"

-ex. lipids act as a boundary that surrounds and contains the aqueous (watery) contents of your cells.
* other types of lipid molecules circulate in your body as chemical signals to cells



Fats

* some fats are solid at room temperature and some are liquids at room temperature (oil)
- liquids - saturated fat
- solids - unsaturated fat
* saturated fats may be unhealthy


Concept Check 5.3
1. What property do lipids share?


2. What are the parts of a fat molecule?




3. Describe two ways that steroids differ from fats.
Steroids are classified as lipids because they are hydrophobic, and some steroids circulate in your body as chemical signals.

4.What does the term unsaturated fat on a food label mean?
Contains less than the maximum number of hydrogen atoms in one or more of its fatty acid chains because some of its carbon atoms are double-bonded to each other.

Summary of 5.1

Concept 5.1: Carbon is the main ingredient of organic molecules.

Key Terms:
organic molecule -- carbon-based molecule

inorganic molecule -- non-carbon-based molecules
hydrocarbon -- organic molecule composed of only carbon and hydrogen atoms
functional group -- a group of atoms within a molecule that interacts in predictable ways with other molecules.

hydrophilic -- attracts water molecules

monomer -- small molecular unit that is the building black of a larger molecule

polymer -- cells link monomers together into long chairs.

Notes:

Carbon Skeletons and Functional Groups
* carbon atoms are so common in living things
-carbon has 4 electrons

-can hold 4 bonds with other atoms
-other atoms can branch off into four directions
* carbon can form bonds with one or more other carbon atoms endlessly

-carbon-based molecules (organic molecules)
-non-carbon-based molecules (inorganic molecules)

-ex. water (H2O), oxygen (O2), and ammonia(NH3)

* can bond with carbon atoms, and other elements

-ex. composed of only carbon and hydrogen (hydrocarbons)
* most organic molecules that contain hydroxyl groups are hydrophilic

-"water-loving"

Monomers and Polymers
* biomolecules maybe composed of hundreds or even millions of atoms

-molecular units: monomers

-many monomers together; form into long chain: polymers

* every living cells has thousands of different kinds of polymers

-vary from cell to cell within an organism

-all of these polymers are formed by fewer than 50 kinds of monomers

* life's large molecules are classifies into four main categories: carbohydrates, lipids, proteins, and nucleic acids.

Building and Breaking Polymers

* when monomer is added to a chain, a water molecule is released (dehydration reaction)

-de:removing hydro: water

* organisms build and break polymers down

-ex.many of the molecules in your food are polymers

-we need to break down large molecules into small pieces

* cells break bonds between monomers by adding water to them, the reverse of dehydration (hydrolysis reaction)

-hydro-: water -lysis: break down

Concept Check 5.1

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

2. Explain the connection between monomers and polymers.
Connection between monomoers and polymers are monomers are molecules that are large molecules built from many similar, smaller molecular units; and polymers are a long chain which is made out of many monomers.

3. What molecule is released during construction of a polymer? What is this reaction called?

Water is released during constrution of a polymer, and this reaction is called dehydration reaction.

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