Biology Honors midterm 2012 SG

Completion
Complete each statement.

	1.	____________________ is the study of the interaction of organisms with their environment and with each other.

	2.	To function properly, all living things must maintain a constant internal environment through the process of ____________________.

	3.	An educated guess, or a(n) ____________________, may be tested by experimentation.

	4.	Stating in advance the result that may be obtained from testing a hypothesis is called ____________________.

	5.	A unifying explanation for a broad range of observations is a ____________________.

	6.	A ____________________ experiment is one in which the condition suspected to cause the effect is compared to the same situation without the suspected condition.

	7.	The base unit for length in the Système International d’Unités (International System of Units) is the ____________________.

	8.	A ____________________ electron microscope passes a beam of electrons over a specimen’s surface, whereas a ____________________ electron microscope passes a beam of electrons through a thin slice of a specimen.

	9.	Substances that are changed when they become involved in chemical reactions are called ____________________, while the new substances that are formed are called ____________________.

	10.	The energy needed to break existing chemical bonds during the initiation of a chemical reaction is called ____________________.

	11.	Chemical reactions in the body can be speeded up by adding a(n) ____________________, which lowers the amount of activation energy required to start the reaction.

	12.	The loss of electrons from a molecule is called ____________________, while the gain of electrons by a molecule is called ____________________.

	13.	A substance that dissolves in another is called a(n) ____________________.

	14.	____________________ is the most common solvent in cells.

	15.	____________________ and ____________________ ions form when water dissociates.

	16.	An acidic solution is one that has more ____________________ than ____________________ ions.

	17.	A solution with a pH of 3 has ____________________ times more hydronium ions than a solution with a pH of 6.

	18.	Buffers are important because body fluids must be maintained within a relatively narrow range of ____________________.

	19.	Water is very effective at dissolving other polar substances because of its ____________________.

	20.	Breaking of ____________________ bonds is the first thing that happens when water is heated, which means that it takes a great deal of thermal energy to raise the temperature of water.

	21.	Because carbon atoms have four electrons in their outermost energy level, they can form up to ____________________ covalent bonds with other atoms.

	22.	In the molecule that has the chemical formula C_2H_4, the carbon atoms are bonded together with a ____________________ bond.

	23.	In a condensation reaction, two molecules become linked together and a molecule of ____________________ is produced.

	24.	The formation of polymers from monomers occurs as a result of ____________________ reactions, and the breakdown of polymers into monomers occurs as a result of ____________________ reactions.

	25.	Lipids are ____________________ molecules because they have no negative and positive poles.

	26.	A substrate attaches to the ____________________ of an enzyme.

	27.	In a triple bond, ____________________ pair(s) of electrons is (are) shared between two atoms.

	28.	ATP contains ____________________ phosphate groups.

	29.	The statement “Cells are produced only from existing cells” is part of the ____________________.

	30.	The ratio of surface area to ____________________ puts limitations on a cell’s size.

	31.	Eukaryotic cells are much larger and have more specialized functions than prokaryotic cells because they contain ____________________, which carry out specialized activities.

	32.	A cell with a well-defined nucleus and cytoplasm surrounded by a plasma membrane is a(n) ____________________ cell.

	33.	A plasma membrane is said to be ____________________ permeable because it allows the passage of some solutes and not others.

	34.	____________________ molecules have “heads” and “tails” and are found in the plasma membrane.

	35.	Scientists have discovered that cells contain smaller specialized structures known as ____________________.

	36.	The spherical organelles that are the site of protein synthesis in a cell are the ____________________.

	37.	The meshlike network of protein fibers that supports the shape of the cell is called the ____________________.

	38.	The fluid portion of the cytoplasm is called the ____________________.

	39.	Photosynthesis takes place in the ____________________ of plant cells.

	40.	Both plant and animal cells have plasma membranes. In addition, plant cells are surrounded by a(n) ____________________.

	41.	

Refer to the illustration above. The diagram shows the ____________________ that makes up the framework of the plasma membrane.

	42.	Matthias Schleiden worked with ____________________ cells, and Theodor Schwann worked with ____________________ cells.

	43.	Some plants produce a _________________________ between the plasma membrane and the primary cell wall.

	44.	____________________ tissue joins, supports, and protects other types of tissue.

	45.	The ____________________ is a wall of muscle that separates the thoracic and ____________________ cavities.

	46.	Refer to the illustration above. Bones 2 and 3 are part of the ____________________ skeleton.

	47.	Refer to the illustration above. Bones 1 and 4 are part of the ____________________ skeleton.

	48.	The bones of the skull and backbone are part of the ____________________ skeleton.

	49.	The bones of the arms, legs, and pelvis make up the ____________________ skeleton.

	50.	The ____________________ is a membrane that surrounds individual bones.

	51.	The ____________________ inside long bones is important in blood cell production and fat storage.

	52.	The heart and lungs are protected by the ____________________.

	53.	The place where two bones meet is called a(n) ____________________.

	54.	_________________________ is a painful degeneration of movable joints caused by attacks on the joints by cells of the immune system.

	55.	____________________ tissue can be smooth, skeletal, or cardiac.

	56.	____________________ muscle is found in the walls of many internal organs.

	57.	The proteins actin and ____________________ in muscles enable the cells to contract.

	58.	Repeating units of actin and myosin filaments are called ____________________.

	59.	____________________ are muscles that cause bones to bend at a joint.

	60.	Muscles that function to straighten a joint are called ____________________.

	61.	Cords of connective tissue that attach muscles to bones are called ____________________.

	62.	The brown pigment ____________________ determines skin color.

	63.	Overexposure to ____________________ radiation may result in the mutations in skin cells that cause skin cancer.

	64.	The outermost layer of the skin is called the ____________________.

	65.	Hairs grow from specialized epidermal structures called hair ____________________.

	66.	Acne is caused by overactive ____________________ and hormones.

Problem  10 points each

	67.	Some scientists conducted an experiment in which they evaluated various measurements of human health in people who drank at least one cup of coffee a day. They found no significant differences in these health indicators between the subjects who drank only one cup of coffee a day and those who drank as many as 20 cups a day. They concluded that coffee has no adverse effects on human health. Write your answers to the following in the spaces below.
a. What were the independent and dependent variables in this experiment?
b. Was this a controlled experiment? If so, what were the control and experimental groups?
c. Do you agree with the conclusion the scientists drew from their results? Why or why not?

	68.	

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. Write your answers to the following in the spaces below.
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.

	69.	You are given four test tubes containing purified biological macromolecules. The test tubes are unlabeled except for a number between 1 and 4. You are told that one test tube contains a protein, one contains a lipid, one contains a carbohydrate, and one contains a nucleic acid. You then perform some tests on the macromolecules and collect the following information:
1)	Test tubes #2 and #4 contain nitrogen, but the other tubes do not.
2)	The contents of test tube #3 are not soluble in water, but the contents of the other test tubes are soluble in water.
3)	The contents of test tube #1 can be broken down into subunits that are all exactly identical to each other.
4)	The macromolecule in test tube #2 is found to have a globular shape.

What are the identities of the macromolecules present in the four test tubes? Write your answer in the space below.

	70.	A living cell has certain characteristics in common with a working factory. In a factory, products are assembled according to specified plans, energy is used in the assembly process, products are packaged and taken out of the factory, and a supervisor directs and oversees all of the activities occurring in the factory. Draw a model of a factory, labeling areas where the following important activities would occur: main office where supervisor keeps the plans and oversees activities, assembly line, electricity generator, packaging center, and factory doors. Next to each of your labels, write the name of the cellular organelle or structure that has a similar function. Choose the cellular organelles and structures from this list: nucleus, cytoplasm, cell membrane, mitochondrion, endoplasmic reticulum, Golgi apparatus, vacuole. Write your answer in the space below.

	71.	Connective tissue plays many different roles in the human body. It is crucial for providing structural support for the body. It provides protection for internal organs. It facilitates the movements of body parts. It functions in the transport of substances throughout the body. It serves a storage function for certain kinds of molecules. It also plays a vital role in enabling the body to defend itself against invading organisms or other foreign substances.
In the space below, write a short essay that first identifies the connective cell types discussed in your text. Next, distinguish these cell types from each other by their physical characteristics and by the type of matrix in which the cells are embedded. Finally, relate the physical characteristics and the type of intercellular matrix to the specific function(s) that each of these cell types performs.

Essay

	72.	Briefly discuss some of the major themes in biology that we will examine this year. Write your answer in the space below.

	73.	Name five characteristics that are considered distinct properties of all living things. Write your answer in the space below.

	74.	Toads that live in hot, dry regions bury themselves in the soil during the day. How might this be important to the toad? Write your answer in the space below.

	75.	The results of an experiment do not support the hypothesis that the experiment was designed to test. Was the experiment a waste of time? Explain. Write your answer in the space below.

	76.	Why is it important to study biology even if you are not planning a career in biology? Write your answer in the space below.

	77.	Plant growers often use sprinkler irrigation to protect crops they are growing from frost damage. The water that lands on the leaves turns to ice. How does this protect the plants from frost damage? Write your answer in the space below.

	78.	Define enzyme, and describe how an enzyme can function in speeding up a chemical reaction within a cell. Write your answer in the space below.

	79.	How does water’s polar nature affect its ability to dissolve different substances? Write your answer in the space below.

	80.	Explain the relationship between hydrogen bonding and the observation that a full sealed bottle of water breaks when it freezes. Write your answer in the space below.

	81.	How are the organs of a multicellular organism like the organelles of a single cell? Write your answer in the space below.

	82.	Give an example of each of the following types of tissue, and briefly describe its functions: epithelial tissue, muscle tissue, connective tissue, and nervous tissue. Write your answer in the space below.

	83.	List five types of freely movable joints in your body, and give a location for each. Write your answer in the space below.

	84.	Using examples, describe the three basic types of joints and their primary functions. Write your answer in the space below.

	85.	What is a ligament? Write your answer in the space below.

	86.	List the three types of muscle tissue, and give the function of each. Write your answer in the space below.

	87.	Describe the function of sliding filaments in the contraction of muscles. Write your answer in the space below.

	88.	What causes acne? Write your answer in the space below.

	89.	What is muscle fatigue? What causes it? Write your answer in the space below.

Biology Honors midterm 2012 SG
Answer Section

COMPLETION

	1.	ANS:	Ecology

PTS:	1	DIF:	1	OBJ:	1-2.1

	2.	ANS:	homeostasis

PTS:	1	DIF:	1	OBJ:	1-1.5

	3.	ANS:	hypothesis

PTS:	1	DIF:	1	OBJ:	1-3.2

	4.	ANS:	
predicting
prediction

PTS:	1	DIF:	1	OBJ:	1-3.1

	5.	ANS:	theory

PTS:	1	DIF:	1	OBJ:	1-3.5

	6.	ANS:	controlled

PTS:	1	DIF:	1	OBJ:	1-3.3

	7.	ANS:	meter

PTS:	1

	8.	ANS:	scanning, transmission

PTS:	1	DIF:	1	OBJ:	1-4.2

	9.	ANS:	reactants, products

PTS:	1	DIF:	1	OBJ:	2-2.2

	10.	ANS:	activation energy

PTS:	1	DIF:	1	OBJ:	2-2.3

	11.	ANS:	enzyme

PTS:	1	DIF:	1	OBJ:	2-2.3

	12.	ANS:	oxidation, reduction

PTS:	1	DIF:	1	OBJ:	2-2.4

	13.	ANS:	solute

PTS:	1	DIF:	1	OBJ:	2-3.4

	14.	ANS:	Water

PTS:	1	DIF:	1	OBJ:	2-3.4

	15.	ANS:	
Hydroxide, hydrogen
Hydrogen, hydroxide

PTS:	1	DIF:	1	OBJ:	2-3.2

	16.	ANS:	hydronium, hydroxide

PTS:	1	DIF:	1	OBJ:	2-3.5

	17.	ANS:	
1,000
1000
a thousand
one thousand

PTS:	1	DIF:	2	OBJ:	2-3.5

	18.	ANS:	pH

PTS:	1	DIF:	1	OBJ:	2-3.5

	19.	ANS:	polarity

PTS:	1	DIF:	1	OBJ:	2-3.2

	20.	ANS:	hydrogen

PTS:	1	DIF:	2	OBJ:	2-3.3

	21.	ANS:	
four
4

PTS:	1	DIF:	1	OBJ:	3-1.2

	22.	ANS:	double

PTS:	1	DIF:	3	OBJ:	3-1.2

	23.	ANS:	water

PTS:	1	DIF:	1	OBJ:	3-1.4

	24.	ANS:	condensation, hydrolysis

PTS:	1	DIF:	1	OBJ:	3-1.4

	25.	ANS:	nonpolar

PTS:	1	DIF:	1	OBJ:	3-2.4

	26.	ANS:	active site

PTS:	1	DIF:	1	OBJ:	3-2.3

	27.	ANS:	
three
3

PTS:	1	DIF:	1	OBJ:	3-1.2

	28.	ANS:	
three
3

PTS:	1	DIF:	1	OBJ:	3-1.5

	29.	ANS:	cell theory

PTS:	1	DIF:	1	OBJ:	4-1.3

	30.	ANS:	volume

PTS:	1	DIF:	1	OBJ:	4-2.2

	31.	ANS:	organelles

PTS:	1	DIF:	2	OBJ:	4-4.5

	32.	ANS:	eukaryotic

PTS:	1	DIF:	1	OBJ:	4-2.3

	33.	ANS:	selectively

PTS:	1	DIF:	1	OBJ:	4-3.1

	34.	ANS:	Phospholipid

PTS:	1	DIF:	1	OBJ:	4-3.1

	35.	ANS:	organelles

PTS:	1	DIF:	1	OBJ:	4-3.3

	36.	ANS:	ribosomes

PTS:	1	DIF:	1	OBJ:	4-3.3

	37.	ANS:	cytoskeleton

PTS:	1	DIF:	1	OBJ:	4-3.5

	38.	ANS:	cytosol

PTS:	1	DIF:	1	OBJ:	4-2.3

	39.	ANS:	chloroplasts

PTS:	1	DIF:	1	OBJ:	4-4.4

	40.	ANS:	cell wall

PTS:	1	DIF:	1	OBJ:	4-4.1

	41.	ANS:	phospholipid bilayer

PTS:	1	DIF:	2	OBJ:	4-3.1

	42.	ANS:	plant, animal

PTS:	1	DIF:	1	OBJ:	4-1.2

	43.	ANS:	secondary cell wall

PTS:	1	DIF:	1	OBJ:	4-4.2

	44.	ANS:	Connective

PTS:	1	DIF:	1	OBJ:	45-1.1

	45.	ANS:	diaphragm, abdominal

PTS:	1	DIF:	1	OBJ:	45-1.4

	46.	ANS:	appendicular

PTS:	1	DIF:	1	OBJ:	45-2.1

	47.	ANS:	axial

PTS:	1	DIF:	1	OBJ:	45-2.1

	48.	ANS:	axial

PTS:	1	DIF:	1	OBJ:	45-2.1

	49.	ANS:	appendicular

PTS:	1	DIF:	1	OBJ:	45-2.1

	50.	ANS:	periosteum

PTS:	1	DIF:	1	OBJ:	45-2.2

	51.	ANS:	marrow

PTS:	1	DIF:	1	OBJ:	45-2.2

	52.	ANS:	rib cage

PTS:	1	DIF:	1	OBJ:	45-2.1

	53.	ANS:	joint

PTS:	1	DIF:	1	OBJ:	45-2.4

	54.	ANS:	Rheumatoid arthritis

PTS:	1	DIF:	1	OBJ:	45-2.5

	55.	ANS:	Muscle

PTS:	1	DIF:	1	OBJ:	45-3.1

	56.	ANS:	Smooth

PTS:	1	DIF:	1	OBJ:	45-3.1

	57.	ANS:	myosin

PTS:	1	DIF:	1	OBJ:	45-3.2

	58.	ANS:	sarcomeres

PTS:	1	DIF:	1	OBJ:	45-3.2

	59.	ANS:	Flexors

PTS:	1	DIF:	1	OBJ:	45-3.4

	60.	ANS:	extensors

PTS:	1	DIF:	1	OBJ:	45-3.4

	61.	ANS:	tendons

PTS:	1	DIF:	1	OBJ:	45-3.4

	62.	ANS:	melanin

PTS:	1	DIF:	1	OBJ:	45-4.1

	63.	ANS:	ultraviolet

PTS:	1	DIF:	1	OBJ:	45-4.1

	64.	ANS:	epidermis

PTS:	1	DIF:	1	OBJ:	45-4.2

	65.	ANS:	follicles

PTS:	1	DIF:	1	OBJ:	45-4.5

	66.	ANS:	oil glands

PTS:	1	DIF:	1	OBJ:	45-4.3

PROBLEM

	67.	ANS:	
a. The independent variable was the number of cups of coffee a subject drank each day; the dependent variables were the indicators of human health measured.
b. This was not a controlled experiment because there was no group of subjects who drank zero cups of coffee a day.
c. Students should disagree with the scientists’ conclusion because this was not a controlled experiment (there could be something harmful in coffee that would be effective when only one cup of coffee was consumed each day).

PTS:	1	DIF:	3	OBJ:	1-3.4

	68.	ANS:	
a.	A and B
b.	C and D
c.	An input of energy, called the activation energy, is required in order to get the reaction going.
d.	The products contain less energy than the reactants and energy is given off in the reaction.
e.	The graph should be the same except that the energy level at point 2 should be higher.

PTS:	1	DIF:	3	OBJ:	2-2.2

	69.	ANS:	
Test tube #1 contains a carbohydrate.
Test tube #2 contains a protein.
Test tube #3 contains a lipid.
Test tube #4 contains a nucleic acid.

PTS:	1	DIF:	2	OBJ:	3-2.2

	70.	ANS:	
The drawing should include the following pairs:
main office—nucleus
assembly line—endoplasmic reticulum
electricity generator—mitochondrion
packaging center—Golgi apparatus
factory doors—plasma membrane

PTS:	1	DIF:	3	OBJ:	4-3.3

	71.	ANS:	
The students’ essays should include the following information: Bone is a kind of connective tissue that contains cells embedded in a hard, crystalline matrix containing calcium. This type of matrix makes bone rigid and thus well suited for providing structural support and protection of internal organs. For example, the skull protects the brain, the rib cage protects the heart and lungs, and the pelvic and abdominal cavities protect organs of the reproductive, digestive, and excretory systems. Cartilage is a kind of connective tissue that contains cells embedded in a semisolid, fibrous matrix. This structure makes cartilage strong yet flexible. Cartilage provides some structural support, particularly in young humans and at stress points between adjacent bones. Ligaments and tendons are both tough, fibrous connective tissue, also with a semisolid, fibrous matrix. Ligaments connect bones to each other at joints and tendons attach muscles to bones. Both help the body make skeletal movements. Fat tissue, which also has a semisolid matrix, is a kind of connective tissue that contains cells that store fat as an energy reserve. Blood is a kind of connective tissue that contains cells embedded in a liquid matrix. Blood is the medium in which nutrients and wastes are transported to and from the cells of the body. Some of the blood cells function as part of the immune system to defend our bodies against invading organisms and foreign substances.

PTS:	1	DIF:	3	OBJ:	45-1.1

ESSAY

	72.	ANS:	
Major themes are the diversity and unity of life, the interdependence of organisms, and the evolution of life. Diversity and unity refers to the many different kinds of organisms that share similar characteristics even though the organisms themselves are so different. Interdependence refers to ecology and the interaction of organisms with each other and the environment. Evolution refers to changes in species over time.

PTS:	1	DIF:	2	OBJ:	1-2.1

	73.	ANS:	
Possible answers include the following: All living things are composed of one or more cells and have a hierarchy of organization. All living things respond to stimuli. All living things maintain a constant internal environment (homeostasis). All living things carry out metabolic reactions that involve the use of energy. All living things grow. All living things reproduce and pass on genetic information to offspring. Populations of living things change over time.

PTS:	1	DIF:	2	OBJ:	1-1.3

	74.	ANS:	
Toads must maintain a constant internal environment (homeostasis) in order to function properly. Burying themselves in the soil is an adaptation that keeps their body temperature from rising too high and keeps their bodies from drying out.

PTS:	1	DIF:	2	OBJ:	1-2.4

	75.	ANS:	
No, the experiment was not a waste of time. A scientist works by systematically showing that certain hypotheses are not valid when they are not consistent with the results of experiments. The results of experiments are used to evaluate alternative hypotheses. An experiment can be successful if it shows that one or more of the alternative hypotheses are inconsistent with observations.

PTS:	1	DIF:	2	OBJ:	1-3.2

	76.	ANS:	
By studying biology, you can make informed decisions that impact both you and the society in which you live. Decisions about your health, your food supply, and your environment are only some of these issues.

PTS:	1	DIF:	2	OBJ:	1-1.2

	77.	ANS:	
Water, like any other form of matter, requires an input of thermal energy to change from a solid to a liquid state. It therefore must also give off thermal energy when it changes from a liquid to a solid state. When liquid water turns to ice on plant leaves, it gives off thermal energy that warms the leaves.

PTS:	1	DIF:	3	OBJ:	2-2.1

	78.	ANS:	
Enzymes are biological catalysts. They are protein or RNA molecules that lower the activation energy that would otherwise be required for a reaction to occur.

PTS:	1	DIF:	2	OBJ:	2-2.3

	79.	ANS:	
A weaker attraction exists between polar and nonpolar molecules than between two polar molecules, so a water molecule cannot pull a nonpolar molecule into solution.

PTS:	1	DIF:	1	OBJ:	2-3.2

	80.	ANS:	
When water freezes, multiple hydrogen bonds form between the molecules. This hydrogen bonding causes water molecules to form a rigid array with large amounts of open space between the molecules relative to liquid water. Because water molecules move farther apart when they freeze, the ice took up more volume than the liquid water and the bottle broke.

PTS:	1	DIF:	3	OBJ:	2-3.3

	81.	ANS:	
The organs of a multicellular organism each carry out specialized tasks that enable the whole organism to survive. Similarly, organelles of a single cell each carry out specialized tasks that enable the whole cell to survive.

PTS:	1	DIF:	3	OBJ:	4-2.5

	82.	ANS:	
Epithelial tissues, such as skin, are generally flat sheets of cells that protect from damage and control water loss in the tissues that they cover. Muscle tissue moves the body (skeletal muscle) and moves materials through the body (heart, smooth muscle of digestive tract). Connective tissue defends the body from invaders (white blood cells), stores materials (fat), and supports the body (bone and cartilage). Nervous tissues (brain, spinal cord, nerves) carry information in the form of electrical impulses.

PTS:	1	DIF:	1	OBJ:	45-1.1

	83.	ANS:	
The shoulder and hip are ball-and-socket joints. The top two vertebrae of the spine form a pivot joint, allowing the head to turn from side to side. Gliding joints are found in the feet. The base of the thumb is a saddle joint. The knee is an example of a hinge joint.

PTS:	1	DIF:	1	OBJ:	45-2.4

	84.	ANS:	
Fixed joints are very tight joints that hold adjacent bones together, permitting no movement. The cranial bones of the skull are held together by fixed joints. Limited mobility is permitted by semi-movable joints, the second basic type of joint. In these joints, a bridge of cartilage joins two bones together, as in the joints between the vertebrae of the spine. The third type of joint is the freely movable joint. These joints allow the greatest degree of movement; they are found between bones that are held together by ligaments.

PTS:	1	DIF:	1	OBJ:	45-2.4

	85.	ANS:	
A ligament is a tough connective tissue that joins one bone to another.

PTS:	1	DIF:	1	OBJ:	45-2.4

	86.	ANS:	
The three types of muscle are skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle moves bones, and cardiac muscle pumps blood through the body. Smooth muscle moves food through the digestive tract and is also found in the uterus, the bladder, and the blood vessels.

PTS:	1	DIF:	1	OBJ:	45-3.1

	87.	ANS:	
Myosin and actin filaments lie in parallel lines along the length of a myofibril in units called sarcomeres. The myosin heads touch the adjacent actin filaments. When a muscle contracts, the myosin heads attach to the actin filaments, and when the heads bend inward, they pull the actin filaments along with them toward each other. Muscle contraction requires energy supplied by ATP. As the actin filaments move toward each other along the myosin filament, they pull their Z lines with them, thus shortening the sarcomere. As sarcomeres are shortened along the entire muscle fiber, the muscle contracts.

PTS:	1	DIF:	2	OBJ:	45-3.3

	88.	ANS:	
Acne is caused by hormones and an increase in oil production by glands during adolescence. Excessive oil production can clog the oil glands, causing a buildup of oil.

PTS:	1	DIF:	1	OBJ:	45-4.3

	89.	ANS:	
Muscle fatigue is the physiological inability of a muscle to contract and is a result of the depletion of ATP. When ATP is depleted, a state of continuous contraction occurs.

PTS:	1	DIF:	1	OBJ:	45-3.5