BIOLOGY HELP. 1-The final shape of a protein is very important to its function. When proteins undergo an irreversible change in shape called ________________ they ________________ perform their usual functions.

	naturation/can
	naturation/cannot
	denaturation/can
	denaturation/cannot
	dehydration reaction/cannot

 

 

2-Which group of lipids will contain hydrophilic heads that face outwards and hydrophobic tails that face inwards that will form a barrier?

	phospholipids
	steroids
	triglycerides
	saturated acids
	trans-fatty acids

 

3-DNA codes for the sequence of amino acids in the primary structure of a protein, but not for sugars or lipids. This is because

	only proteins are involved in living metabolic reactions.
	sugars and lipids code for their own replication.
	sugars and lipids are ever present in the living environment and are not used in living structures.
	other hereditary molecules code for sugars and lipids.
	proteins are the main structural and functional components of cells.

 

4-Which statement about the cellular nucleic acids DNA and RNA is incorrect?

	DNA is double-stranded, and RNA is single-stranded.
	The sugar in DNA is deoxyribose, and in RNA the sugar is ribose.
	DNA has a helix shape; RNA does not.
	RNA and DNA have the same four nitrogen-containing bases.
	Both DNA and RNA are polymers of nucleotides.

 

5-All carbohydrate molecules

	contain amino acids.
	contain nitrogen and phosphate.
	are organic acids.
	are composed of atoms of C, H, and the functional group -OH.
	are composed of atoms of C, H, O, and N.

 

6-Two molecules of glucose combine to form a disaccharide molecule during a(n) ________ reaction.

	dehydration
	hydrolysis
	hydrogen bond
	ionic bond
	inert

 

7-One carbon atom can form covalent bonds with up to ___ other atoms to form an organic molecule.

	2
	3
	4
	6
	8

 

8-Enzymes are organic compounds classified as

	nucleic acids.
	carbohydrates.
	lipids.
	steroids.
	proteins.

 

9-Organic molecules

	always contain carbon.
	always contain hydrogen.
	always contain carbon and hydrogen.
	are found only in organisms, hence their name.
	are always food molecules.

10-The water strider is an insect that skates across the water without sinking. The tips of its feet must be coated with molecules that are

	ions.
	hydrophilic.
	hydrophobic.
	basic.
	acidic.

 

11-Nucleic acids are polymers of

	amino acids.
	nucleotides.
	glycerol.
	monosaccharides.
	fatty acids.

 

12-DNA codes for the sequence of amino acids in the primary structure of a protein, but not for sugars or lipids. This is because

	only proteins are involved in living metabolic reactions.
	sugars and lipids code for their own replication.
	sugars and lipids are ever present in the living environment and are not used in living structures.
	other hereditary molecules code for sugars and lipids.
	proteins are the main structural and functional components of cells.

 

 

13-The moon lacks life and varies dramatically in temperature. If we could keep a layer of water spread on the surface of the moon, what effect would it have?

	Life would be possible but it would have to withstand these extremes in temperature.
	Water would absorb and hold heat and moderate the temperature extremes.
	The temperatures would drop to the lower extremes.
	Because water has a high heat of vaporization, the temperatures would rise to the upper extremes.
	Physical conditions would remain the same.

 

 

14-____ is a polysaccharide that is found in plant cell walls and accounts for their strength.

	Cellulose
	Chitin
	Glycogen
	Starch
	Cholesterol

15-The primary function of carbohydrates is

	quick fuel and short-term energy storage.
	structural reinforcement of plant and fungal cell walls.
	encoding the hereditary information.
	to speed chemical reactions in cells.
	to transport molecules across cell membranes.

 

16-Which of the following types of lipid is the most abundant constituent of cell membranes?

	cholesterol
	phospholipid
	triglyceride
	neutral fat
	fa

BIOLOGY HELP

 

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Properties Of Water Lab. Name_________________ per____ date______ mailbox______

Properties of Water Lab

Water’s chemical formula is H2O. As the diagram to the left shows, that is one atom of oxygen bonded to two atoms of hydrogen. The hydrogen atoms are “attached” to one side of the oxygen atom, resulting in a water molecule having a positive charge on the side where the hydrogens reside and a negative charge on the other side, where the oxygen atom resides. This separation of charge on opposite ends of the molecule is called polarity. Since opposite

electrical charges are attracted to one another, water molecules tend to be attracted to each other. This makes water tend to be

kind of “sticky.” As the right-side diagram shows; the hydrogen end of the bottom water molecule’s (positive charge) is attracted to the oxygen end of the above water molecule’s (negative charge) and so on and so forth up the chain. This property of water is known as cohesion. All these water molecules attracting each other mean they tend to clump together. This is why water drops are, in fact drops! If it wasn’t for gravity, these drops would be ball shaped or spherical as is the case aboard the International Space Station.

Even if it doesn’t form a perfect sphere on Earth, we ought to be happy water has the properties it does. Indeed without these properties we could not exist. For instance, for many of the same reasons water is “sticky” it is also known as the “Universal Solvent” because it dissolves perhaps more substances than any other liquid on Earth. This means that wherever water goes, either through the ground, our bodies, the sky or oceans it carries with it valuable chemicals, like minerals and nutrients.

Ever wonder, how a water strider walks across the surface of a pond without sinking? The surface water bears a remarkable property. On the molecular scale, it acts like a stretched elastic membrane or “skin.” This property is referred to as surface tension and is largely due to cohesion between adjacent water molecules. It is caused by the attraction of the particles in the surface layer and the bulking up of the liquid below, tending to minimize surface area as molecules strive for the optimal pole to pole bonding arrangement. The whole effect causes tightness at the surface, which resists the step of a water strider’s foot, supports a leaf temporarily and causes water to bead up on windows, certain clothing or a duck’s back. It can slow the wetting process of certain fabrics and inhibit the cleaning process too.

Surface tension can however be reduced. Increase the water’s temperature and kinetic energy starts to move molecules about again, while also promoting evaporation. The water vapor now above can linger in transition grabbing at remaining water molecules along the surface boundary and tugging at them from above. Bring water to a boil and surface tension is all but lost.

The addition of substances such as soap or detergent (known as surfactants) can reduce surface tension by increasing the spreading and wetting properties of water. Surfactant molecules look like tadpoles. The head is hydrophilic meaning attracted to water and typically soluble. Meanwhile, the tail of

a surfactant is composed of fatty material that is insoluble in water and allows grease, oils or other fats to stick to it. This property of not dissolving in water makes it hydrophobic

1

meaning to repel water. Surfactant molecules break cohesion and surface tension allowing water to contact more dirt particles, making fabrics wetter and allowing materials to be cleaned.

Water striders can walk on the surface of water despite having a density themselves greater than that of water. Meaning they ought to sink if not for water’s properties. However, surface tension and tiny hairs on their feet which are hydrophobic allow them to keep from getting wet and keeps them afloat.

1. Fill in the properties of water we investigate during this lab, from the reading above.

a. _____________ relating to the separation of charges in a molecule

b. _____________ meaning to repel water, literally “fear of water”

c. _____________ term for a chemical which can break surface tension

d. _____________ this term describes the force of attraction between adjacent water molecules.

e. _____________ meaning attracted to water or literally “water loving”

2. ______What is the property of water that describes a water molecule’s charge ?

a. polarity b. surface tension

c. cohesion

 

d. surfactant

3. ______What is the property of water that describes the force of attraction between water molecules?

a. polarity b. hydrophobic

c. cohesion

 

d. surfactant

4. ______What is the property of water allows a water strider to walk on the surface of water?

a. polarity b. surface tension

c. cohesion

 

d. adhesion

5. Definitions: use the reading.

Define: polarity- ________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

Define: cohesion- ________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

Define: surface tension-___________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2

Water QUESTIONS

1. Explain why water is the universal solvent using a complete sentence. Use the word solubility or dissolve.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

2. What is a polar molecule? Explain. Use the words positive, negative and charge.

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

3. Which end of the water molecule is negative? Which end is positive?

_____________________________________________________________________________

_____________________________________________________________________________

 

Fill in the blank:

Surface tension causes water to ______________________ on surface like glass.

Water molecules are _____________________ to other water by a process called cohesion.

Surfactants are used to break cohesion between water molecules, making surfaces wetter and allowing water to _____________ away dirt.

 

STATION 1: PENNY

1. Place a penny flat on the table.

2. Hypothesize – how many drops of water do you think the penny could hold before water spills over the edge? Experiment with the head side verses the tails side of the coins.

3. Using a dropper, count how many drops the penny holds until it spills over. Draw how the water appeared on the penny right before it spilled off.

 

Hypothesis – Estimated # of drops  Heads ________ Tails ________

 

Record the actual # of drops ________

Properties Of Water Lab

 

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