Chapter 5 Review (pg 106-107)

1. Which of the following 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
b. side 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

8. Besides satisfying your hunger, why else might you consume a big bowl of pasta the night before a race?
It will fill you up with carbohydrates that can be broken down for energy during the race.

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

They are all kinds of sugar.

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

Steroids are special lipids that travel arounnd the body as chemical signals. Estrogen and testosterone work like this and are major components for the male and female appearances. Cholesterol is a steroid found in cell membranes from where other steroids are made.

11. How are polypeptides related to proteins?

Proteins consist of amino acids linked in large chains called polypeptides.

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

After a protein is unraveled in a process called denaturation, it is no longer able to function properly.

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?
water
b. What is this kind of reaction called? Explain.
This is called a dehydration reaction because two hydrogen molecules and an oxygen molecule were removed so the two amino acids could bond. The left over molecules make up water.
c. If an amino acid were added to this chain, at what two places could it attach?
They could attach either to the H on one side or the OH on the other side.

15. Analyzing Graphs Use the graph to answer the questions below.
a. At which temperature does enzyme A perform best? Enzyme B?
Enzyme A performs best around 38 degrees Celsius. Enzyme B performs best around 78 degrees Celsius.
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.
Enzyme A is probably found in humans while enzyme B is probably found in thermophilic bacteria.
c. Propose a hypothesis that explains why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40°C.
After 40 degrees Celsius, it's hot enough for reactions to take place on their own without the help of an enzyme.

Chapter 5.5 Summary

Enzymes are proteins that speed up specific reactions in cells.

• Enzymes and Activation Energy
• Activation energy: energy that activates the reactants to start a chemical reaction
• Catalysts: Compounds that speed up chemical reactions
• Enzymes: Proteins that are the main catalysts for reactions in organisms
• Lower energy requirement barrier so reactions can occur at normal temperatures
• Each enzyme catalyzes a specific reaction
• How Enzymes Work
• Shape of enzyme fits only particular reactant molecules
• Substrate: Specific reactant acted on by an enzyme
• Active Site: The region of the enzyme that the substrate fits into
• Functional groups of substrate are placed in positions to catalyze reaction
• Enzymes also lower activation energy by accepting two substrates into adjacent sites
• Holding reactants together makes them react easier
• Environment effects enzymes' functioning

Concept Check 5.5

1) Explain the role of activation energy in a reaction. How does an enzyme affect activation energy?
Activation energy is the amount of energy needed to start a chemical reaction. Heat is a common trigger, however heating up a cell could destroy its delicate structures. Enzymes are special proteins that lower the energy required so reactons can occur at a normal temperature.

2) Describe how a substrate interacts with an enzyme.
A substrate enters the enzyme's active site, positioning its functional groups in certain places to catalyze the reaction. The interaction between the substrate and enyzme lowers the activation energy so the chemical reaction can proceed.

Chapter 5.4 Summary

Proteins perform most functions in cells

The Functions of Proteins
Protein: A polymer constructed from a set of just 20 kinds of monomers called amino acids
Responsible for day to day functions of organisms
Eg. Make up muscles, defend body from harmful microorganisms, act as signals, control chemical reactions in cells
Amino Acids
Amino acid: A monomer consisting of a central carbon atom bonded to four partners
3 of the bonded partners are always the same: a hydrogen atom, carboxyl group, and amino group
Difference is the "side group" - responsible for chemical properties of each acid
Building a Protein
Polypeptide: Amino acids linked together to create proteins
Formed by dehydration reaction between amino group and carboxyl group
Variety of proteins because of different amino acids in different orders
Polypeptides at least 100 amino acids in lenghth
Protein Shape
Polypeptides precisely twisted, folded, coiled into unique shape
Sequence of amino acids is important
Influenced by environment (usually aqueous)
Hydrophilic amino acids - towards outside edges of protein
Hydrophobic amino acids - towards center of protein
Denaturation: When a change in the environment causes a protein to unravel
Denatured protein loses ability to work properly

Concept Check 5.4
1) Give at least two examples of proteins you can "see" in the world around you. What are their functions?
Two proteins you can see in the world around you are ones that form structures such as hair or fur, and make up the muscles of an organism.

2) Relate amino acids, polypeptides, and proteins
Proteins are polymers constructed from amino acids, which are monomers with a central carbon atom, that are linked together into a chain called a polypeptides. Most polypeptide chains are around 100 amino acids in length.

3) Explain how heat can destroy a protein.
Heat causes a process called denaturation in a protein which is when the protein unravels, preventing it from functioning properly. The forces that keep the protein in its folded shape are weak bonds between the side groups or a side group and water. Hot molecules collide with enough to force to overcome these weak attractions.

4) Which parts of an amino acid's structure are the same in all amino acids? Which part is unique?
All amino acids share the same three partners bonded to the central carbon atom: a hydrogen atom, a carboxyl group, and an amino group. The part that differentiates them is the side group which is the fourth partner. The side group determines each proteins properties.

Chapter 5.3 Summary

Lipids include fat and steroids

• Characteristics of Lipids
• Lipids: water-avoiding compounds, eg. oil
• Hydrophobic: water-avoiding molecules
• Lipids are boundaries for containing aqueous contents
• Fats store energy in your body
• Fats
• Fat: A three-carbon backbone called glycerol attached to three fatty acids with long hydrocarbon chains
• Fat cushions organs and provides insulation
• Saturated fat: Fat where all three acid chains contain the maximum number hydrogen atoms (All carbons are single bonded)
• Most animal fats are saturated - solid at room temp
• Unsaturated fat: Less than max number of hydrogen because some carbons are double-bonded
• Fats in fruits, vegetable, and fish are usually unsaturated
• Saturated fat can promote buildup of plaque - lipid-containing deposits - which contributes to heart disease
• Steroids
• Steroid: A lipid whose carbon skeleton forms four fused rings
• Different from fats
• Steroids circulate in your body as chemical signals
• Cholesterol: Essential steroid found in cell membranes
• A starting point for producing other steroids

Concept Check 5.3

1) What property do lipids share?

All lipids are hydrophobic, meaning they avoid water.

2)What are the parts of a fat molecule?

A fat molecule consist of a three carbon backbone called glycerol attached to three fatty acids which contain long hydrocarbon chains.

3) Describe two ways that steroids differ from fats.

Unlike fats, steroids' carbon skeletons are formed by four fused rings. Instead of storing energy in the body, steroids travel around the body as chemical signals.

4) What does the term unsaturated fat on a food label mean?

Unsaturated fat means the food contains fat with less than the maximum number of hydrogen atoms in in its fatty acid chains. Unsaturated fat is usually found in fruit, vegetable, and fish products such as corn oil, olive, oil, and other vegetable oils.

Chapter 5.2 Summary

Carbohydrates provide fuel and building material

• Sugars:
• Carbohydrate: an organic compound made up of sugar molecules
• Sugar formula: 1 carbon, 2 hydrogen, 1 oxygen
• Core of sugar molecules are carbon skeletons with a ring shape
• Monosaccharides: Simple sugars containing one sugar unit
• Examples: glucose, fructose, galactose:
• Sugar molecules are main fuel supply for cellular work
• Cells break down glucose to extract energy
• Dissacharides: Two monosaccharides linked together
• Most common dissacharide is sucrose
• Polysaccharides:
• Polysaccharides: Long polymer chains made up of simple sugar monomers
• Starch: A polysaccharide found in plant cells
• Starch chains are sugar stockpiles
• Starch is broken down for glucose
• Glycogen: The polysaccharide animal cells use to store excess sugar
• Glycogen is usually stores as granules in liver and muscle cells
• Cellulose: A polysaccharide in plants used as a building material
• It protects and stiffens plants
• Humans cannot digest cellulose/fiber
• Most carbs are hydrophilic because of hydroxyl groups in sugar unites
• Monosaccharides and dissacharides dossolve easily in water
• Larger carbs (starch, cellulose) can't be dissolved but are still hydrophilic
  

starch:

Concept Check 5.2

1) Explain the difference between a monosaccharide and a dissacharide. Give an example.

Monosaccharides, such as glucose, consist of only one sugar unit while dissacharides, such as sucrose, consist of two sugar units bonded together

2) Compare and contrast starch, glycogen, and cellulose.

Starch, glycogen, and cellulose are all polysaccharides. Starch and glycogen are used to store energy in cells. Starch however is only found in plant cells, while glycogen is found in animal cells. Cellulose is a polysaccharide found in plants that protects the cells and stiffens the plant to prevent it from flopping over.

3) How do animals store excess glucose molecules?

Animals store glucose in the form of a polysaccharide called glycogen. glycogen is usually stored as granules in the liver and muscle cells. When the energy is needed, the glycogen granules are broken down to release the glucose.

Chapter 5.1 Summary

Carbon is the main ingredient of organic molecules

• Carbon Skeletons and Functional Groups
• Carbon can form up to 4 bonds with other atoms
• Organic molecules: carbon-based molecules
• Inorganic molecules: non-carbon-based molecules, eg. water/oxygen/ammonia
• Hydrocarbons: organic molecules composed of only carbon and hydrogen atoms
• Two other atoms often in organic molecules are oxygen and nitrogen
• Functional group: A group of atoms within a molecule that interact in predictable ways with other molecules
• Carbon skeleton and functional groups determine properties of org. molecules
• Hydrophilic: attract water molecules
• Monomers and Polymers
• Biomolecules composed of hundreds or millions of atoms
• Monomers: Similar, smaller molecular units
• Polymers: Long chains of monomers linked together
• May be straight chains, branching chains, or chains folding back on themselves
• Thousands of polymers built by fewer than 50 types of monomers
• Four categories of life's main molecules: carbohydrates, lipids, proteins, nucleic acids
• Building and Breaking Polymers
• Dehydration Reaction: When a water molecule is released when a monomer is added
• Polymers must be broken down
• Food is broken down to make monomers available
• Either break down monomers for energy to build new polymers
• Hydrolysis Reaction: When water is added to break bonds between monomers

Concept Check 5.1

1) Draw a molecule that has a three-carbon skeleton and a hydroxyl group on the middle carbon.

2) Explain the connection between monomers and polymers.
Monomers are the small molecular units that are linked together to create polymer.

3) What molecule is released during the construction of a polymer? What is this reaction called?
A water molecule is released during the construction of a polymer in a reaction called a dehydration reaction.

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