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BOTANY AN INTRODUCTION TO PLANT BIOLOGY: CHAPTER TWO REVIEW QUESTIONS

1. Do plants or animals have any metabolic reactions that cannot be modeled by hypotheses and verified by

experimentation and observation? What was vital force thought to be?

I dont think there are plants or animals undergoing metabolic reactions that cannot be modeled by

hypotheses because even though metabolism seem to be complex or complicated, ALL living things are capable

of growth, response, reproduction that can be modeled by hypotheses and verified by experimentation and

observation. Vital force is believed to be a theory that organic compounds can only be produced by living things

and cannot be prepared on laboratories.

2. In the concepts section of this chapter, three major discoveries of the 1800s are described. One concerned the

synthesis of biological compounds; one involved the enzymes and the third was a discovery made by Louis

Pasteur. List this discoveries, and explain why they are important.

The three major discoveries in 1800s:

a. Biological compounds could be synthesized using inorganic chemicals and ordinary chemical processes;

b. Enzymes were extracted from yeast cells and some steps of fermentation were carried out in vitro

without the presence of yeast cells and;

c. Louis Pasteur proved that spontaneous generation does not occur and there is no vital force.

For me, because of this discoveries, we are able to understand not only plant metabolism but also of all living

things and it lead for new discoveries and laws we are able to use up to this day.

3. Some elements are more stable as ions than as neutral atoms. Why? Give examples of biologically important

positive ions.

Some elements, either cation or anion , becomes positive when they transfer valence electron from one

element to another. It also says that atoms are more stable when they have less energy. Some examples of

biologically important positive ions are hydrogen, iron, sodium and manganese.

4. What does it mean to say that after sodium reacts with chlorine, the resulting compound NaCl is more stable

than the two reactants? If they are more stable, did they give off energy? If so, did they become warmer during

the reaction? If so, where did the energy of the heat go?

NaCl becomes more stable after reaction because when sodium transferred its single unpaired electron,

it gives sodium a stable arrangement while chlorine gets the electron it needs to have a full energy, making itmore stable than its two reactants. And yes, while reacting it gives off energy. (It is exergonic)

5. If a reaction gives off energy (liberates it to the environment), is that reaction exergonic or endergonic? If the

energy is given off as heat, what is the reaction called?

A reaction can be exergonic or exothermic, since the energy is not specified and heat can also be

considered as a form of energy. If the energy is given off as heat, then it is the time when we say it is exothermic.

6. The reaction for the formation of water from hydrogen and oxygenand can be made to run in the opposite

direction (water is break down into hydrogen and oxygen) if energy is supplied. This reverse reaction occurs in

plants in process of photosynthesis. What do you think is the source of energy? Because energy is put into

reaction, what type of reaction is this?The source of energy is called endothermic while the reverse reaction of this is called endergonic.

7. What type of bond holds sodium to chlorine in sodium chloride? What type of bond holds hydrogen to oxygen in

water?

The type of bond that holds sodium to chloride is called ionic bond, while oxygen to water is covalent

bond.

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8. Examine Figure2-3b, which shows hydrogen bonding in water. Within any plant or animal cell there are millions

of water molecules that are hydrogen bond together. This allows a plant to pull water upward through its body.

(water is pulled in plants and water is pushed in animals). Imagine how water is pulled. What would happen if

there is no hydrogen bonds?

Without hydrogen bonds, there will be no sticky effect in water molecules and therefore water will not

be lifted from roots to leaves.

9. If a solution is has a high concentration of protons, is it acidic or basic? What about if it has a high

concentration of hydroxyl ions (OH-)? When HCl is mixed with water, it breaks down to H+ ions and Cl- ions.

Because eof the H+ ions it produces, is HCl an acid or a base?

Any solution with high concentration of Hydrogen protons is an ACID while those with high hydroxyl ions

or (OH-) is a BASE. And HCL is an example of an acid since it contain a hydrogen atom.

10. The bonding between carbon atoms is important because virtually all biological molecules in plants contain

carbon atoms bonded to other atoms, often to other carbon atoms. What is the shape of a molecule in which the

Carbon has only single bond?

Single bond in carbon has a shape of tetrahedron, double bond is flat or linear and triple bond is usually

broken.

11.Why is it necessary for tworeactants to collide vigorously for a reaction to occur? What happens to the shape

of valence orbitals if a reaction occurs? What happen if there is no reaction occurs?It is necessary for two reactants to collide vigorously for a reaction because they need to overcome the

electron-cloud repulsion, and this energy they need to is called the activation energy. The valance orbitals

rearrange themselves to nonbonding to bonding orbitals, and if there is no reaction that occurred, cloud

repulsion will not be overcomed and two atoms bounce off to each other.

12.Although there is no way to change the energy of activation of a reaction, it is possible to change the

mechanism of reaction. There are two names for substance that do this: Catalyst (is a general term) and enzymes

(is used when this is a protein in a living organism).

13.An endergonic reaction tends to proceed slowly because it absorbs energy. How do plants force endergonic

reactions to occur rapidly? Is ATP involved? Why is ATP such a versatile molecule? Because its breakdown to ADPand Piis highly exergonic, is its synthesis endergonic?

Maybe plants force endergonic reactions to occur rapidly by using catalysts or energy they get from the

sun. Yes, ATP is involved and ATP is a versatile molecule because almost all endergonic reactions are forced to

proceed using it. ATPs synthesis is endergonic, because before it is capable to occur, it needs a source of energy.

14. Name five functional groups and give the chemical formula for each. What properties does each functional

group give to the molecule to which it is attached?

FUNCTIONAL GROUPS:

a. Hydrogen (-H)

b. Hydroxyl (-OH)

c. Methyl (-CH3)

d. Amino (-NH2)

e. Sulfhydryl (-SH)

15. What are carbohydrates, pentoses, and hexoses? Name several hexoses and describe how they differ from

each other. How can enzymes distinguish between them?

Carbohydrates is an organic compound usually composed of carbon, hydrogen and oxygen. The ratio of

its hydrogen to oxygen is 2:1 and generalized by a chemical formula (CH2O)n. Pentoses (contains 5 carbon atoms)

and hexoses (six-) are the most abundant and important classification of monosaccharide, which is then a type of

carbohydrates.

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16. Various sugars in a class may have the same chemical formula but differ in their atomic arrangements; such

molecules are calledIsomers.

17. Monosaccharides are a bit unusual in that they are just long enough that as they vibrate one end often

accidentally comes close to the other end of the same molecule and the two can react. Therefore, they can exist as

ring-shaped molecules or as open, chain-shaped ones. Do the two forms of the same molecule have the same

chemical and physical properties?

YES. Because simply, they have the same components and chemical structures.

18. When we eat plants, we are eating mostly polysaccharides. What are the two starches we eat? One is

unbranched: amylose; the other is branched: amylopectin.Another polysaccharide that we eat is in the cell walls;

it iscellulose.

19. What is the technical name of the bond in starch? What is the technical name of the bond in cellulose? They

both involve the same carbon atoms of the glucose molecules. Starch and cellulose are virtually identical , except

that all of the glucose face the same way in starch, whereas in cellulose alternating glucoses face in the opposite

direction. Does this matter: Can you digest starch? Can you digest cellulose?

Alpha-1, 4-glycosidic bond is the technical name of bond in starch, while the bond in cellulose is called

beta-1, 4-glycosidic bond. Yes, we can digest starch but we cannot digest cellulose, unlike some organisms who

can digest them since their digestive tracts contain microorganisms like bacteria with proper enzymes forcellulose breakdown.

20. Proteins are unbranched polymers composed of amino acids. The bond that holds the monomers together in

proteins is called a peptide bond.

21. What are the three groups found in every amino acid? What are R Groups, and how do they differ from one

amino acid to another? Would you agree that because R Groups are not involved in forming a peptide bond they

are not really important?

The three groups of amino acid are:

a.-COOH or the carboxyl group that causes it to be an acid;

b.NH2 or the amino group and;c.H

though there is still one group and it is called the R group. They differ from other amino acid because they are not

involved in polymerization, they enter to the side of protein backbone and they determine the property of the

protein. Even though they are not part of forming peptide bond, I think that they are still essential since their

properties gives the properties of a certain amino acid, thats why they must still be considered important.

22. What is the primary structure of protein? Are proteins flexible or rigid? Are any of the bonds in the backbone a

double or triple bond or are all of them single bonds?

The amino acid sequence is the primary structure of protein. Proteins are said to be flexible.

23. If proteins had double bonds in the backbone they would be rigid molecules. Do you think they would then

have a secondary, tertiary or quaternary structure? Why is the tertiary structure of the hypothetical protein in

Figure 2-15 different form that of Figure 2-15c?

Protein with double bonds in the backbone might be a secondary structure. A tertiary structure in figure

2-15b is different from figure 2-15c because in figure b, there are present negative amino acids , making every

regions interact and thus forming a three dimensional shape or what we call a tertiary structure, while figure c

shows us that when there is no negative amino acids, the structure will not be the same.

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24. The tertiary structure of a protein is affected by pH (acidity) and heat. Can you give examples of that? Our

stomachs secrete acid. What do you think is its effect on our ability to digest protein? Have you ever friend or

boiled an egg? What is the change caused by the heat?

One example of tertiary structure of protein affected either by pH or heat is the sterilization of medical

instruments to denature and destroy proteins in bacteria, killing them off. I think it is one enzyme or rather a

chemical inside our stomach, HCl or hydrochloric acid responsible for digesting proteins we intake, which is one

effect we are capable of digesting it. Heat can also affect protein, they destroy and unfold proteins, giving

something like a structure of fried or boiled egg, making it firm and solid.

25. What do initials DNA and RNA stand for? What are the four nucleotides that occur in DNA? What are the four

that occur in RNA? Which nucleotide unique to DNA, is never found in RNA? Which nucleotide is unique to RNA?

DNA stands for deoxyribonucleic acid while RNA means ribonucleic acid. The four nucleotides that can be

found in DNA are Cytosine, Guanine, Adenine and Thymine, while we can find are Adenine, Guanine, Cytosine

and Uracil. Thymine is the only nucleotide unique to DNA, while uracil if for RNA.

26. What sugar occurs in DNA? What sugar occurs in RNA?

Deoxyribose sugar occurs in DNA, while ribose if for the RNA.

27. Fats and oils are substances known as lipids. These are always hydrophobic and insoluble in water. If one of

these molecules encountered a protein that has a region of hydrophobic amino acids and a region of hydrophilic

ones, which region would the molecule associate with?Since lipids are said to be hydrophobic, automatically they will associate to hydrophobic amino acids

because they will only repel to hydrophilic ones.

28. The basic units of many lipids are fatty acids. What is saturated fatty acid? Do they tend to be straight or

kinked?

Saturated fatty acid have carbon atom except the carboxyl carbon carries two oxygen. They can no longer

hold hydrogen and all carbon-carbon-bonds are single with parts of molecule that can rotate and they tend to be

straight.

29. What is an unsaturated fatty acid? Do they tend to be straight or kinked?

Unsaturated Fatty acids are double bonded to adjacent carbons, with rigid carbon-carbon double bondsand tendency to kink.

30. If you place both a stick of butter and cup of oil in the refrigerator, the butter becomes hard while the oil

remain liquid. Which is composed of saturated fats, and which is mostly composed of unsaturated ones? It is very

important for plants and animals to have fats in their cell membranes that remain liquidotherwise the plant

would die. Do you think plants of cold climates have more unsaturated fats in their cell membrane than do plants

in hot climates?

The stick of butter is composed of saturated fatty acids while oil is made up of unsaturated fatty acids. I

think that plants in cold climates have more unsaturated fats in their membranes because these fats easily melts

in low temperature and I think that it will be more easier for plants to produce food using a liquefied form of fat

for convenience, rather than using saturated fat which can even consume much energy if they use them.

31. Fatty acids tend to polymerize with each other, especially when exposed to oxygen. If the fatty acids are

relatively short, the polymer is called cutin. If they are relatively long, it is called wax.

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32. How does a triglyceride differ from phospholipid? How do these two differ in their ability to dissolve in water?

How does this make one especially suitable for the construction of membranes?

Triglycerides are composed of three fatty acids combined with one molecule of glycerol while

phospholipid contain glycerol, two fatty acid and a phosphate group. Triglycerides are usually hydrophobic or

they repel against water while phospholipids are hydrophilic. Phospholipids form two layer membranes, a

hydrophobic layer contacting another hydrophobic layer, making it both repelling and attracting to water which is

suitable and exactly the property needed to build biological membranes.

33. Cofactors are essential to the activity of some enzymes. Name two cofactors.

Magnesium (Mg2+

) AND iron (Fe3+

)

34. Each coenzyme carries one of three things into a reaction. What are the three things?

These three things are energy, electrons and functional groups.

35. What is the full name of ATP? The last two phosphate groups of ATP are attached by ____-_____________

bonds.

ATP stands for adenosine triphosphate. The last two groups of ATP are attached by high-energy

phosphate bonds.

36. When a reaction needs to have energy put into it, forcing it to proceed, what is the molecule that usually

participates? After the reaction, what has the energy-carrying coenzyme been converted to?Molecule that usually participates and forcing it to proceed is the adenosine diphosphate (ADP) and after

the reaction, the energy-carrying coenzyme been converted to adenosine monophosphate.

37.Examine Figure 2-22. The breakdown of ATP and P gives off energy. The reaction A+B->AB absorbs energy.

How does combining these two reactions allow the second one to proceed? Would combining the two reactions

force the second one to proceed if the breakdown of ATP gave off only 2 units of energy.

To allow the second one to proceed, they can be coupled with endergonic reactions and force them to

proceed. ATP can force the reaction A+B->AB to proceed by first transferring a phosphate to one of the reactants

in an enzyme-mediated phosphorylation: A+ATP->A-P+ADP.I think they can proceed to second one with only 2

units of energy gave by ATP, since based on the illustration, the dephosphorylation of ATP can supply power to

endergonic reaction.

38. Many reactions in plants generate molecules that have a strong tendency to donate electrons. Other reactions

need electrons to proceed. Name three electron carriers that transport electrons from one type of reaction to the

other.

These three electrons are nicotinamide adenine nucleotide (NAD+), flavin adenine dinucleotide (FAD) and

flavin mononucleotide (FMN).

39. The atoms or molecules that an enzyme interacts with it are its substrates, and these must fit into and be

bound by the enzymes active suitif a reaction is to occur.

40.Some enzymes will bind to only one or two substrates. Is their substrate specificity high or low? Other enzymes

will bind to various substrates as long as they are atleast somewhat similar. Is their substrate specificity high or

low?

Those enzymes which only bind to one or two substrates have high substrate specificity, while those

which bind with various similar substrates are low substrate specificity.

41. Cells control the activities of their enzymes by a variety of methods. Name of least five factors that affect

enzyme activity.

Those factors that can affect enzyme activity are the cellular pH, temperature, presence of magnesium

and calcium ions, presence of activators and its concentration.