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Chapter 5 – Cell Transport Study Guide

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Chapter 5 Cell Transport studyguide

 

 

Modified True/False
Indicate whether the statement is true or false.  If false, change the identified word or phrase to make the statement true.
 1.
One way that cells maintain homeostasis is by controlling the movement of substances across the cell membrane. _________________________
 2.
The cell membrane is made up of a double layer called the DNA bilayer. _________________________
 3.
A phospholipid is made up of a lipid “head” and two fatty acid “tails.” _________________________
 4.
The nonpolar tails of a phospholipid are attracted to water. _________________________
 5.
Cell-surface markers face the inside of the cell. _________________________
 6.
A concentration gradient exists when one area has a higher concentration of a substance than another area does. _________________________
 7.
The movement down a concentration gradient is called diffusion. _________________________
 8.
When the solute concentration outside a cell is equal to the solute concentration inside the cell, the cell’s environment is hypotonic. _________________________
 9.
A cell placed in a high salt solution would swell because of osmosis. _________________________
 10.
Osmosis is the diffusion of starch molecules through a selectively permeable membrane. _________________________
 11.
To pass through a cell membrane, water requires carrier proteins. _________________________
 12.
Facilitated diffusion is an active process that requires a cell to expend a great deal of energy. _________________________
 13.
Passive transport uses ATP to move molecules against their concentration gradient. _________________________
 14.
Exocytosis is a process that uses vesicles to capture substances and bring them into a cell. _________________________
 15.
Cells use exocytosis to export proteins modified by the Golgi apparatus. _________________________
 16.
Cells communicate by sending chemical signals that carry information to other cells. _________________________
 17.
Receptor proteins bind only to signals that match the specific color of the binding site. _________________________
 18.
Receptor proteins may cause the formation of a second messenger molecule inside the cell. _________________________
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 19.
cell membrane : cell ::
a.
 window : house
c.
 door : house
b.
 roof : house
d.
 wall : house
 20.
Which type of molecule forms the cell membrane?
a.
 protein
c.
 nucleic acid
b.
 phospholipid
d.
 carbohydrate
 21.
Phospholipids are molecules that have
a.
 one polar phosphate head and two polar fatty acid tails.
b.
 one polar phosphate head and two nonpolar fatty acid tails.
c.
 one polar phosphate head and one polar fatty acid tail.
d.
 one nonpolar phosphate head and two polar fatty acid tails.
 22.
The interior of the lipid bilayer of a cell membrane forms a nonpolar zone that
a.
 allows most polar molecules to pass through the membrane.
b.
 allows food to pass through the membrane.
c.
 repels ions and most polar molecules.
d.
 makes the membrane permeable to most molecules.
nar001-1.jpg
 23.
Refer to the illustration above. The structure labeled A is composed of
a.
 lipids.
c.
 proteins.
b.
 carbohydrates.
d.
 DNA.
 24.
Refer to the illustration above. The structure labeled D is a(n)
a.
 cell-surface marker.
c.
 enzyme.
b.
 receptor protein.
d.
 transport protein.
 25.
Refer to the illustration above. The structure labeled C is a(n)
a.
 cell-surface marker.
c.
 enzyme.
b.
 receptor protein.
d.
 transport protein.
 26.
Proteins in the cell membrane that identify the cell are called
a.
 cell-surface markers.
c.
 enzymes.
b.
 receptor proteins.
d.
 transport proteins.
 27.
As a result of diffusion, the concentration of many types of substances
a.
 always remains greater inside a membrane.
b.
 eventually becomes balanced on both sides of a membrane.
c.
 always remains greater outside of a membrane.
d.
 becomes imbalanced on both sides of a membrane.
nar002-1.jpg
 28.
Refer to the illustration above. The process shown is called
a.
 osmosis.
c.
 active transport.
b.
 facilitated diffusion.
d.
 diffusion.
 29.
Diffusion is the movement of a substance
a.
 only through a lipid bilayer membrane.
b.
 from an area of low concentration to an area of higher concentration.
c.
 only in liquids.
d.
 from an area of high concentration to an area of lower concentration.
 30.
The dispersal of ink in a beaker of water is an example of
a.
 diffusion.
c.
 active transport.
b.
 osmosis.
d.
 endocytosis.
 31.
Proteins that serve as tunnels for specific substances through the lipid bilayer are
a.
 cell-surface markers.
c.
 receptor proteins.
b.
 channel proteins.
d.
 enzymes.
 32.
Sugar molecules cross the cell membrane by
a.
 active transport.
c.
 osmosis.
b.
 facilitated diffusion.
d.
 simple diffusion.
 33.
Which of the following does not require energy?
a.
 diffusion
c.
 active transport
b.
 endocytosis
d.
 sodium-potassium pump
 34.
Ions move through ion channels by
a.
 endocytosis.
c.
 passive transport.
b.
 simple diffusion.
d.
 active transport.
 35.
The diffusion of water into or out of a cell is called
a.
 solubility.
c.
 selective transport.
b.
 osmosis.
d.
 endocytosis.
 36.
Osmosis is a type of
a.
 active transport.
c.
 simple diffusion.
b.
 passive transport.
d.
 endocytosis.
 37.
How does water pass through the cell membrane?
a.
 directly through the lipid bilayer
b.
 through a water ion pump
c.
 through water carrier proteins
d.
 through channel proteins just for water
 38.
Which of the following statements about an isotonic solution and a cell is correct?
a.
 The solution has the same solute concentration that the cytoplasm does.
b.
 The solution has a higher solute concentration than the cytoplasm does.
c.
 A cell in the solution will lose water.
d.
 A cell in the solution will gain water.
 39.
Unlike passive transport, active transport
a.
 requires energy.
b.
 moves substances down their concentration gradient.
c.
 does not involve carrier proteins.
d.
 moves water across the cell membrane.
 40.
Both active transport and facilitated diffusion involve
a.
 ATP.
b.
 movement against a concentration gradient.
c.
 carrier proteins.
d.
 channel proteins.
 41.
Which of the following is a form of active transport?
a.
 osmosis
c.
 facilitated diffusion
b.
 simple diffusion
d.
 sodium-potassium pump
 42.
The sodium-potassium pump
a.
 is a carrier protein.
c.
 is located in the cytoplasm of a cell.
b.
 uses passive transport.
d.
 transports sugar molecules.
 43.
The sodium-potassium pump usually pumps
a.
 potassium ions out of the cell.
b.
 sodium ions into the cell.
c.
 potassium ions into the cell.
d.
 only potassium ions and sugar molecules.
 44.
How many potassium ions does the sodium-potassium pump move into a cell if it moves six sodium ions out of the cell?
a.
 two
c.
 six
b.
 four
d.
 eight
 45.
Proteins and polysaccharides that are too large to move into a cell through diffusion or active transport move in by
a.
 exocytosis.
c.
 the sodium-potassium pump.
b.
 endocytosis.
d.
 channel proteins.
 46.
Molecules that are too large to be moved across a cell membrane can be removed from the cell by
a.
 diffusion.
c.
 endocytosis.
b.
 exocytosis.
d.
 osmosis.
 47.
Removing materials from a cell in vesicles is called
a.
 osmosis.
c.
 exocytosis.
b.
 diffusion.
d.
 endocytosis.
 48.
Which of the following descriptions of hormones is correct?
a.
 signal molecules distributed throughout the body
b.
 signal molecules that affect all cells in the body
c.
 target molecules that communicate through direct contact
d.
 target molecules that originate outside the body
nar003-1.jpg
 49.
Refer to the illustration above. What happens when the structure labeled A binds to the structure labeled B?
a.
 Information is sent into the cell.
c.
 The cell begins to swell.
b.
 Proteins enter the cell.
d.
 Ions enter the cell.
 50.
Refer to the illustration above. The structure labeled B in the diagram is an example of a(n)
a.
 channel protein.
c.
 receptor protein.
b.
 signal molecule.
d.
 ion pump.
 51.
Signal molecules bind to
a.
 carbohydrates.
c.
 receptor proteins.
b.
 marker proteins.
d.
 transport proteins.
 52.
Which of the following transmit information into a cell by binding to signal molecules?
a.
 channel proteins
c.
 marker proteins
b.
 receptor proteins
d.
 signal proteins
 53.
What change takes place in the cell membrane if a signal molecule causes a transport protein to open?
a.
 permeability change
c.
 formation of a second messenger
b.
 activation of an enzyme
d.
 change in chemical reactions
 

Completion
Complete each statement.
 54.
One way cells maintain homeostasis is by controlling the movement of substances across the cell ____________________.
 55.
A(n) ____________________ is a specialized lipid made of a phosphate head and two fatty acid tails.
 56.
The phosphate head of a phospholipid is attracted to water because it is ____________________.
 57.
The fatty acid tails of a phospholipid are repelled by water because they are ____________________.
 58.
The phospholipids form a barrier through which only small, ____________________ substances can pass.
 59.
Ions and most polar molecules are repelled by the ____________________ interior of the lipid bilayer.
 60.
____________________ – ____________________ markers are attached to the cell surface and have sugars attached to their protein.
 61.
Proteins that aid in moving substances into and out of cells are called ____________________ proteins.
 62.
____________________ are proteins in the cell membrane that help with important biochemical reactions inside the cell.
 63.
____________________ proteins enable a cell to sense its surroundings by binding to certain substances outside the cell.
 64.
To reach equilibrium, substances always flow from an area of high concentration to an area of ____________________ concentration.
 65.
When one area has a higher concentration than another area does, a concentration ____________________ exists.
 66.
Substances diffuse through a cell membrane either through the lipid bilayer or through ____________________ proteins.
 67.
Oxygen and carbon dioxide pass through the lipid bilayer by ____________________ diffusion.
 68.
Diffusion of ions through ion channels is a form of ____________________ transport.
 69.
Carrier proteins change ____________________ to transport substances to the interior of cells.
 70.
A cell does not expend ____________________ when diffusion takes place.
 71.
The diffusion of ____________________ through cell membranes is called osmosis.
 72.
When the concentration of free water molecules is higher outside a cell than inside the cell, water will diffuse ____________________ the cell.
 73.
If a cell is placed in a(n) ____________________ solution, water will flow out of the cell.
 74.
If a cell is placed in a(n) ____________________ solution, water will flow into the cell.
 75.
If a cell is placed in a(n) ____________________ solution, water flows into the cell at a rate that is equal to the rate at which water flows out of the cell.
 76.
Active transport requires the use of ____________________ by a cell.
 77.
The ____________________ – ____________________ pump transports ions against their concentration gradients.
 78.
The sodium-potassium pump uses energy supplied by ____________________.
 79.
The sodium-potassium pump prevents the accumulation of ____________________ ions inside the cell.
 80.
The movement of a substance into a cell by a vesicle is called ____________________.
nar004-1.jpg
A
B
 81.
Refer to the illustration above. The process shown in figure B is called ____________________.
 82.
Refer to the illustration above. The process shown in figure A is called ____________________.
 83.
A signaling cell produces a signal that is detected by a ____________________ cell.
 84.
Light is an environmental ____________________ for the flowering of some plants.
 85.
In the cell membrane, proteins that bind to specific signal molecules and respond are called ____________________ proteins.
 86.
Receptor proteins can change the ____________________ of the cell membrane.
 87.
Receptor proteins may act as ____________________, triggering certain chemical reactions inside the cell.
 

Short Answer
 88.
In addition to its function as a gatekeeper, what are three other functions of the cell membrane?
 89.
What makes up the lipid bilayer?
 90.
In the lipid bilayer, what causes one layer of polar heads to face the cell’s cytoplasm and the other layer of heads to face the cell’s surroundings?
 91.
What characteristic of membrane proteins causes them to be held in the cell membrane?
 92.
What are four types of proteins in cell membranes?
 93.
What exists across a cell membrane if equilibrium is not reached?
 94.
What is the difference between how a molecule crosses the cell membrane in simple diffusion and in facilitated diffusion?
 95.
What are two types of transport proteins?
 96.
Why are some water molecules not free to move across the cell membrane?
 97.
Explain why osmosis is a form of facilitated diffusion.
 98.
What specific carrier protein moves sodium ions out of a cell and potassium ions into a cell?
 99.
What is the function of the cell membrane during endocytosis?
 100.
What are hormones, how are they distributed, and what cells do they affect?
 101.
What happens to a receptor protein once it binds to a signal molecule?
 102.
How can the cell’s response to a signal cause a permeability change?
 

Problem
 103.

A biologist conducts an experiment designed to determine whether a particular type of molecule is transported into cells by simple diffusion, facilitated diffusion, or active transport. He collects the following information:

1. The molecule is very small.
2. The molecule is polar.
3. The molecule can accumulate inside a cell, even when its concentration inside the cell initially is higher than it is outside the cell.
4. Cells use up more energy when the molecule is present in the environment around the cells than when it is not present.

The biologist concludes that the molecule moves across cell membranes by facilitated diffusion. Do you agree with his conclusion? Why or why not?
Paramecia are unicellular protists. They have a number of characteristics also found in animals, such needing to ingest food in order to obtain energy and being surrounded by a cell membrane but not by a rigid cell wall. Paramecia have organelles found in animal cells, including a nucleus, mitochondria, ribosomes, and cilia. In addition, they have star-shaped organelles, called contractile vacuoles, that expel excess water. The illustration below depicts a paramecium.

nar005-1.jpg
 104.

Refer to the illustration above. The data presented in the table below were obtained in an experiment in which paramecia were placed in salt water with different concentrations of salt and the rate at which their contractile vacuoles contracted to pump out excess water was recorded.

Salt Concentration
Number of contractile vacuole contractions/minute
Very high
2
High
8
Medium
15
Low
22
Very low
30

 

a. How can you explain the observed relationship between salt concentration and rate of contractile vacuole contraction?
b. If something happened to a paramecium that caused its contractile vacuoles to stop contracting, what would you expect to happen? Would this result occur more quickly if the paramecium was in water with a high salt concentration or in water with a low salt concentration? Why?

 

Essay
 105.
Distinguish between facilitated diffusion and active transport.
 106.
Compare the processes of sodium ions moving through the cell membrane by an ion channel and by an ion pump.
 107.
Why do dissolved particles on one side of a membrane result in the diffusion of water across the membrane?
 108.
Why is it dangerous for humans to drink seawater?
nar004-1.jpg
A
B
 109.
Refer to the illustration above. Identify and explain the processes taking place in figure A and figure B.
 110.
Describe three ways in which the binding of a signal molecule to a receptor protein can change the functioning of a cell.

 
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Dihybrid Crosses Quiz

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1. An organism of genotype AaBb can make gametes of all the following kinds except:

a. AB
b. Bb
c. aB
d. ab

 

2. If AaBb is crossed with aabb, what proportion of the offspring would be expected to be aabb?

a. 9/16
b. 1/8
c. 1/4
d. 1/16

 

3. If the offspring of a cross show a 9/16 to 3/16 to 3/16 to 1/16 ratio (9:3:3:1), the parents of the cross have the genotypes

a. AaBb x AaBb
b. AaBb x aaBB
c. aaBb x aabb
d. aaBb x Aabb

 

4. Whenever a capital letter is present, a red color is produced. In a cross of AaBb x AaBb, how many red offspring would you expect out of 16?

a. 1
b. 3
c. 9
d. 15

 

5. Assume that you mated two individuals heterozygous for each of two traits and obtained 80 offspring. How many of them would be expected to look like their parents?

a. 25
b. 45
c. 60
d. 80

 

6. Genes that assort independently are

a. located on different chromosomes
b. located on the same chromosome
c. alleles of each other
d. dominant

 

7. If W = purple flower and w = white, and D = tall plants and d = short plants, a wwDd plant would be

a. purple and tall
b. purple and short
c. white and tall
d. white and short

 

8. If two true-breeding parents are crossed with each other and all the offspring have their mother’s ears and their father’s tail, the parents in the cross would be

a. EETT x eett
b. eeTT x EEtt
c. EeTt x EeTt
d. eeTt x Eett

 

9. If aaBb is crossed with AAbb, what proportion of the offspring will be AAbb?

a. 0
b. 3/16
c. 9/16
d. 1/4

 

10. If AaBb is crossed with AaBb, what proportion of the offspring will be dominant for the ‘A/a’ trait and recessive for the ‘B/b’ trait (i.e. A-bb)?

a. 9/16
b. 3/16
c. 1/16
d. 0

 

 

Ecology Quiz

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Ecology Quiz

 

Test your knowledge of Ecology!

1. A cold biome characterized by permafrost under the surface?
a) Taiga
b) Tundra
c) Deciduous forest
d) Savanna2. An organism that feeds on plants and animals?
a) Carnivore
b) Omnivore
c) Epiphyte
d) Herbivore

3. All of the following are abiotic factors except:
a) Tree
b) Temperature
c) pH
d) Sunlight

4. Corals would be found in which zone:
a) Oceanic
b) Estuary
c) Neritic
d) Benthic

5. Which of the following is not part of the nitrogen cycle:
a) Ammonification
b) Transpiration
c) Nitrification
d) Rhizobacteria

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Elephants Can

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Elephants Can’t Jump
& Other Freaky Scientific Facts

Welcome to a Fun Site about Science!

Did you know that elephants can’t jump even though they have the same number of bones in their feet as other mammals?
The bones in an elephant’s foot are more closely packed together than other mammals so they do not have the flexibility or spring mechanisms that would enable them to jump.
How many bones are in an elephant’s trunk? The elephant’s trunk has numerous muscles but NO BONE.

 
What is a baby oyster called? They are called spats!
Three fruits are native to North America. Cranberries, Concord grapes, and blueberries!
What was the name of the captain and the ship on which Darwin made his famous voyage? Captain Fitzroy on the H.M.S. Beagle
A Swedish botanist, naturalist, physician and zoologist — Who am I? Carolus Linnaeus
Protozoan can move by cilia, flagella, or pseudopodia.
Give an example of a protist that moves by each of these means.
Include your NAME & PERIOD
cheryl.massengale@russellvilleschools.net 

 

 

 

 

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When were you born?

Chapter 3 Biochemistry Studyguide

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Chapter 3 Biochemistry Study Guide

 

 

Modified True/False
Indicate whether the statement is true or false.  If false, change the identified word or phrase to make the statement true.
 1.
Atoms have a positive charge. _________________________
 2.
Electrons have very little mass. _________________________
 3.
Molecules are atoms that have gained or lost one or more electrons. _________________________
 4.
An atom with more electrons than protons has a positive charge. _________________________
 5.
A covalent bond forms between two atoms that share electrons to form a molecule. _________________________
 6.
Water molecules attract nonpolar molecules such as oil. _________________________
 7.
The ability of water to retain heat helps cells maintain a constant internal temperature. _________________________
 8.
The role of carbohydrates in cells is to supply energy. _________________________
 9.
RNA is made up of a double strand of nucleotides. _________________________
 10.
When cells break down food, the energy from the food is temporarily stored as ATP. _________________________
 11.
The amount of energy needed to cause a chemical reaction to start is called activation energy. _________________________
 12.
Without enzymes, chemical reactions necessary for life would not occur quickly or easily enough to sustain life. _________________________
 13.
When an enzyme binds with its substrate, the activation energy needed for the chemical reaction to occur is increased. _________________________
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 14.
Atoms are not composed of
a.
 protons.
c.
 electrons.
b.
 neutrons.
d.
 chemical bonds
 15.
The electrons of an atom
a.
 are found in the nucleus along with the protons.
b.
 occupy the space surrounding the nucleus.
c.
 have a positive charge.
d.
 are attached to the positive charge of neutrons.
 16.
The smallest particle of matter that can retain the chemical properties of carbon is a carbon
a.
 molecule.
c.
 atom.
b.
 macromolecule.
d.
 element.
 17.
A substance that is composed of only one type of atom is called a(n)
a.
 compound.
c.
 element.
b.
 cell.
d.
 molecule.
 18.
All matter is composed of
a.
 cells.
c.
 atoms.
b.
 molecules.
d.
 carbon.
 19.
Covalent bonds form when
a.
 two molecules of water share electrons.
b.
 a molecule of water becomes an ion.
c.
 two hydrogen atoms share electrons with one oxygen atom.
d.
 two hydronium ions are attracted to each other.
 20.
Ionic bonds form between particles that have
a.
 opposite charges.
c.
 no charges.
b.
 the same charge.
d.
 neutral charges.
 21.
The bond formed when two atoms share a pair of electrons is called a(n)
a.
 hydrogen bond.
c.
 covalent bond.
b.
 ionic bond.
d.
 water bond.
 22.
Sharing of electrons in the outer energy levels of two atoms
a.
 results in ion formation.
b.
 makes both atoms stable.
c.
 only occurs if both are atoms of the same element.
d.
 is found only among carbon atoms.
 23.
A molecule that has a partial positive charge on one side and a partial negative charge on the other side is called a(n)
a.
 nonpolar molecule.
c.
 charged molecule.
b.
 polar molecule.
d.
 ion.
 24.
Nonpolar molecules have
a.
 no negative or positive ends.
c.
 only a negative end.
b.
 both negative and positive ends.
d.
 only a positive end.
 25.
When placed in the same container, oil and water do not mix because
a.
 they are both polar.
c.
 they are both nonpolar.
b.
 water is polar and oil is nonpolar.
d.
 water is nonpolar and oil is polar.
 26.
Attractions between water molecules are called
a.
 covalent bonds.
c.
 polar bonds.
b.
 ionic bonds.
d.
 hydrogen bonds.
 27.
Water is a polar molecule because
a.
 it contains two hydrogen atoms for each oxygen atom.
b.
 it has a charge.
c.
 different parts of the molecule have slightly different charges.
d.
 it does not have a charge.
 28.
Which is not a unique property of water?
a.
 Frozen water floats.
b.
 Water retains a large amount of heat.
c.
 Water molecules stick to each other.
d.
 Water cools rapidly.
 29.
Acidic solutions have a pH that is
a.
 less than 7.
c.
 a negative number.
b.
 between 7 and 14.
d.
 more than 7.
 30.
Hydronium ions, H+, react with hydroxide ions, OH-, to form
a.
 water.
c.
 a base.
b.
 an acid.
d.
 a buffer.
 31.
Which of the following is not a large biomolecule?
a.
 carbohydrate
c.
 lipid
b.
 ice
d.
 nucleic acid
 32.
The building blocks of most biomolecules contain the element
a.
 carbon.
c.
 calcium.
b.
 nitrogen.
d.
 sodium.
 33.
Which of the following molecules are classified as carbohydrates?
a.
 amino acids
c.
 nucleotides
b.
 fats
d.
 sugars
 34.
Polysaccharides are
a.
 carbohydrates.
c.
 proteins.
b.
 lipids.
d.
 nucleic acids.
nar001-1.jpg
nar001-2.jpg
Molecule A
Molecule B
 35.
Refer to the illustration above. Molecule A is a
a.
 carbohydrate.
c.
 nucleic acid.
b.
 lipid.
d.
 protein.
 36.
Plants store glucose in the form of
a.
 starch.
c.
 cellulose.
b.
 glycogen.
d.
 chitin.
 37.
Which of the following is a carbohydrate?
a.
 ATP
c.
 wax
b.
 steroid
d.
 sucrose
 38.
Lipids are
a.
 soluble in water.
b.
 made of chains of amino acids.
c.
 linked together with peptide bonds.
d.
 used by the body for storing energy.
 39.
All of the following are examples of lipids except
a.
 oil.
c.
 steroids.
b.
 starch.
d.
 candle wax.
 40.
Which molecules are most closely related to lipids?
a.
 amino acids
b.
 long chains of carbon and hydrogen
c.
 nucleotides
d.
 sugars
 41.
Which of the following molecules are most closely related to proteins?
a.
 amino acids
c.
 nucleotides
b.
 monosaccharides
d.
 sugars
 42.
Long chains of amino acids are found in
a.
 carbohydrates.
c.
 proteins.
b.
 lipids.
d.
 sugars.
 43.
The overall shape of a single chain of amino acids in a protein is that protein’s
a.
 primary structure.
c.
 tertiary structure.
b.
 secondary structure.
d.
 quaternary structure.
 44.
The amino group of one amino acid is linked to the carboxyl group of another amino acid in a protein. This link is a(n)
a.
 peptide bond.
c.
 ionic bond.
b.
 hydrogen bond.
d.
 polar bond.
 45.
What gives each amino acid its unique properties?
a.
 its side group
c.
 its carboxyl group
b.
 its amino group
d.
 its sequence
 46.
The two types of nucleic acids are
a.
 RNA and ATP.
c.
 DNA and ATP.
b.
 DNA and RNA.
d.
 nucleotides and ATP.
 47.
Which of the following molecules are most closely related to nucleic acids?
a.
 amino acids
c.
 nucleotides
b.
 fats
d.
 sugars
 48.
DNA stores
a.
 fat.
c.
 energy.
b.
 carbohydrates.
d.
 hereditary information.
 49.
The two strands of a DNA molecule are held together by
a.
 ionic bonds.
c.
 hydrogen bonds.
b.
 covalent bonds.
d.
 peptide bonds.
 50.
Which of the following is not part of a nucleotide in a DNA molecule?
a.
 three phosphate groups
c.
 a base
b.
 a sugar
d.
 a phosphate group
 51.
ATP (adenosine triphosphate) stores energy in the bonds between its
a.
 hydrogen atoms.
c.
 nucleotides.
b.
 carbon atoms.
d.
 phosphate groups.
 52.
When paper burns, the paper combines with oxygen to form carbon dioxide and water vapor. How does the mass of carbon dioxide plus water vapor compare with the mass of the paper plus oxygen?
a.
 The mass of carbon dioxide plus water vapor is greater than that of paper plus oxygen.
b.
 The mass of carbon dioxide plus water vapor is less than that of paper plus oxygen.
c.
 It is impossible to tell.
d.
 The mass of carbon dioxide plus water vapor is identical to that of paper plus oxygen.
 53.
The law of conservation of energy states that energy cannot be
a.
 changed from one form to another.
b.
 taken from the surroundings in a reaction.
c.
 released into the surroundings in a reaction.
d.
 created or destroyed in a chemical reaction.
 54.
A chemical reaction will probably occur between two substrate molecules if they
a.
 are far apart.
b.
 are aligned in the wrong spatial orientation.
c.
 have large amounts of kinetic energy.
d.
 have little kinetic energy.
 55.
Reducing activation energy
a.
 is a violation of the laws of nature.
b.
 requires higher temperatures than those found within cells.
c.
 occurs only when reactants are quickly added to the reaction mixture.
d.
 is accomplished by the action of enzymes on reactants.
nar002-1.jpg
 56.
Refer to the illustration above. Which of the following statements regarding the graph is true?
a.
 Reaction 2 occurs faster than Reaction 3 because Reaction 2 requires more energy than Reaction 3.
b.
 The difference between the graphs shown for Reaction 2 and Reaction 3 occurs because of a difference in the activation energy of these reactions.
c.
 Reactant A contains more energy at the beginning of the reaction than product C has at the end of the reaction.
d.
 Product B contains more energy at the end of the reaction than reactant A has at the beginning of the reaction.
 57.
Refer to the illustration above. Reaction 3 in the graph
a.
 probably occurred in the presence of an enzyme.
b.
 requires more activation energy than Reaction 2.
c.
 is the same as Reaction 1, but faster.
d.
 is slower than Reaction 2.
 58.
The molecule on which an enzyme acts is called a(n)
a.
 active site.
c.
 polar molecule.
b.
 inactive site.
d.
 substrate.
 59.
An enzyme
a.
 is used up in a reaction.
b.
 raises the activation energy of a reaction.
c.
 bonds with an active site on a substrate molecule.
d.
 lowers the activation energy of a reaction.
 60.
Enzymes
a.
 are able to heat up molecules so that they can react.
b.
 always provide carbon dioxide for chemical reactions.
c.
 hold substrate molecules in the correct alignment.
d.
 absorb excess heat so that reactions occur at low temperatures.
 61.
A cell contains
a.
 thousands of different kinds of enzymes, each assisting in a different chemical reaction.
b.
 one kind of enzyme that assists in thousands of different chemical reactions.
c.
 approximately 100 kinds of enzymes, each assisting in a different chemical reaction.
d.
 one enzyme that assists in reactions involving protein substrates and one enzyme that assists in reactions involving substrates that are not proteins.
 

Completion
Complete each statement.
 62.
The negatively charged particles in an atom are ____________________.
 63.
Protons and neutrons are found in the ____________________ of an atom.
 64.
A(n) ____________________ is a group of atoms held together by covalent bonds.
 65.
Sodium chloride, NaCl, is an example of a(n) _________________.
 66.
A(n) ____________________ bond forms between two atoms sharing electrons.
 67.
The attraction between oppositely charged ions results in the formation of a(n) ____________________.
 68.
Weak chemical attractions between polar molecules are ____________________ bonds.
 69.
Lipids are ____________________ molecules because they have no negative and positive poles.
 70.
Water heats and cools ____________________.
 71.
The attraction that causes water and other liquids to form drops and thin films is ____________________.
 72.
The medium in which most cellular events take place is ____________________.
 73.
Substances with a pH less than 7 are ____________________.
 74.
Substances with a pH greater than 7 are ____________________.
 75.
The pH scale measures the concentration of ____________________ ions in solutions.
 76.
A carbon atom can bond with four other atoms because it has ____________________ valence electrons.
 77.
A(n) ____________________ contains carbon, hydrogen, and oxygen in a ratio of 1:2:1.
 78.
Amino acids are the building blocks of __________________.
 79.
Most proteins consist of two or more ________________ that twist and fold around each other.
 80.
Long chains of nucleotides are called ____________________.
 81.
The ability to move or change matter is ____________________.
 82.
All living things require a source of ____________________ to carry out their life activities.
 83.
The starting materials for chemical reactions are called ____________________, while the new substances that are formed are called ____________________.
 84.
The energy needed to start a chemical reaction is called ____________________.
 85.
A biochemical reaction can be speeded up by adding a(n) ____________________, which lowers the amount of activation energy required to start the reaction.
 86.
The portion of an enzyme molecule into which a specific substrate can fit is called the ____________________.
 

Short Answer
 87.
How many different kinds of atoms are there in an element?
 88.
How does an atom become an ion?
 89.
An ionic bond forms between what two kinds of particles?
 90.
What makes a water molecule polar?
 91.
How well do nonpolar molecules dissolve in water?
 92.
What is an attraction between particles of different substances called?
 93.
What are the two most common elements found in large biomolecules?
 94.
What is the function of lipids in cells?
 95.
What determines the primary structure of a protein?
 96.
Where do your cells get most of the energy they need for metabolism?
 97.
How do enzymes speed up a chemical reaction?
 

Problem
 98.

The following statements are about the molecule ATP (adenosine triphosphate). For each statement, first determine whether it is true or false. Then, if it is false, rewrite the statement so that it is correct.

a. ATP is chemically similar to a carbohydrate.
b. Cells require ATP to function.
c. None of the energy in food molecules is stored in ATP.
d. ATP is the primary source of energy for chemical reactions occurring in all cells of all living organisms.

nar003-1.jpg
 99.

Refer to the illustration above. The graph depicts the relative energy levels of the products and reactants for the following chemical reaction: A + B « C + D.

a. Which substances, A, B, C, and/or D, are present at point 1 on the graph?
b. Which substances, A, B, C, and/or D, are present at point 3 on the graph?
c. Why is point 2 at a higher energy level than point 1?
d. Why is point 3 at a lower energy level than point 1?
e. Draw a dashed line on the graph indicating how the energy level of this reaction over time would be different if the enzyme that catalyzes the reaction were not present.

Enzymes catalyze a variety of biological reactions. The extent to which they can speed up the rate of a reaction is dependent on a number of factors. Draw a graph for the following condition(s), showing the effect of altering one factor on the relative rate of a reaction. Use “0” to indicate no activity, and “1” through “10” to indicate increasing rate of reaction from very low to very high. Include a label for your graph(s).
 100.
Refer to the paragraph above, and then draw your graph in the space below. Enzyme #1 is inactive between 0°C and 10°C. It is active above 10°C, with the rate increasing steadily until the temperature reaches 40°C. At 40°C, the rate of the reaction is very high. Above 40°C, the rate decreases steadily until the temperature reaches 60°C, at which point the enzyme is no longer active.
 101.
Refer to the paragraph above, and draw your graph. Enzyme #2 is inactive at a pH of 1–4. It is active above a pH of 4, with the rate increasing slowly until the pH reaches 6. Above a pH of 6, the rate increases sharply until the pH reaches 7. Above a pH of 7, the rate decreases sharply until the pH reaches 8. Above a pH of 8, the rate decreases gradually until the pH reaches 10, at which point the enzyme is no longer active.
 102.
Refer to the paragraph above, and draw your graph. Enzyme #3 is inactive when the concentration of the substrate it acts upon is zero. The enzyme is active when the substrate concentration is above zero, with the rate increasing only very slightly until the concentration reaches 30%. Above 30%, the rate increases very sharply to a high level, until the concentration reaches 60%. Above a concentration of 60%, the rate increases very little. The rate does not increase when the substrate concentration is above 80%.
 

Essay
 103.
Describe how an enzyme can function in speeding up a chemical reaction within a cell.

 
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