Exam Two: Bio

C12H22O11

A dehydration reaction joins two glucose molecules to form maltose. The formula for glucose is C6H12O6. What is the formula for maltose?

The hydrophobic substance repels water, perhaps helping to keep the ends of the legs from becoming coated with water and breaking through the surface. If the legs were coated with a hydrophilic substance, water would be drawn up them, possibly making it more difficult for the water strider to walk on water.

A water strider (an insect that can walk on water) has legs that are coated with a hydrophobic substance. What might be the benefit? What would happen if the substance were hydrophilic?

CH3COOH→CH3COO− (+) H+. CH3COOH is the acid (the H+ donor), and CH3COO− is the base (the H+ acceptor).

Acetic acid (CH3COOH) can be a buffer, similar to carbonic acid. Write the dissociation reaction, identifying the acid, base, H+ acceptor, and H+ donor.

The antibiotic treatment is likely to have killed the cellulose-digesting prokaryotes in the cow's gut. The absence of these prokaryotes would hamper the cow's ability to obtain energy from food and could lead to weight loss and possibly death. Thus, prokaryotic species are reintroduced, in appropriate combinations, in the gut culture given to treated cows.

After a cow is given antibiotics to treat an infection, a vet gives the animal a drink of "gut culture" containing various prokaryotes. Why is this necessary?

Acts as a base; can pick up an H+ from the surrounding solution (water, in living organisms) Compound name: Amine

Amino group properties

The hydronium ion is charged, while glycerol is not. Charge is probably more significant than size as a basis for exclusion by the aquaporin channel.

Aquaporins exclude passage of hydronium ions (H3O+) but some aquaporins allow passage of glycerol, a three-carbon alcohol as well as H2O Since H3O+ is closer in size to water than glycerol is, yet cannot pass through, what might be the basis of this selectivity?

Exocytosis. When a transport vesicle fuses with the plasma membrane, the vesicle membrane becomes part of the plasma membrane.

As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis? Explain.

No. There is not enough diversity in propane's atoms. It can't form structural isomers because there is only one way for three carbons to attach to each other (in a line). There are no double bonds, so cis-trans isomers are not possible. Each carbon has at least two hydrogens attached to it, so the molecule is symmetrical and cannot have enantiomers.

Can propane (C3H8) form isomers? Explain

They are on the inside of the transport vesicle membrane.

Carbohydrates are attached to plasma membrane proteins in the ER. On which side of the vesicle membrane are the carbohydrates during transport to the cell surface?

Sugars with ketone groups are called ketoses; those with aldehydes are called aldoses. Compound name: Ketone (carbonyl group is within a carbon skeleton) or aldehyde (carbonyl group is at the end of a carbon skeleton)

Carbonyl group properties

Acts as an acid (can donate H+) because the covalent bond between oxygen and hydrogen is so polar. Compound name: carboxylic acid or organic acid

Carboxyl group properties

One of several compounds that have the same molecular formula and covalent bonds between atoms but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds; formerly called a geometric isomer

Cis-trans Isomers

Each ion is being transported against its electrochemical gradient. If either ion were transported down its electrochemical gradient, this would be considered cotransport.

Compare the sodium-potassium pump in with the cotransporter Explain why the sodium-potassium pump would not be considered a cotransporter.

Both have a glycerol molecule attached to fatty acids. The glycerol of a fat has three fatty acids attached, whereas the glycerol of a phospholipid is attached to two fatty acids and one phosphate group.

Compare the structure of a fat (triglyceride) with that of a phospholipid.

100,000

Compared with a basic solution at pH 9, the same volume of an acidic solution at pH 4 has________ times as many hydrogen ions (H+)

Ions dissolve in water when polar water molecules form a hydration shell around them, with partially charged regions of water molecules being attracted to ions of the opposite charge. Polar molecules dissolve as water molecules form hydrogen bonds with them and surround them. Solutions are homogeneous mixtures of solute and solvent.

Describe how different types of solutes dissolve in water. Explain what a solution is

Hydrogen bonds hold neighboring water molecules together. This cohesion helps chains of water molecules move upward against gravity in water-conducting cells as water evaporates from the leaves. Adhesion between water molecules and the walls of the water-conducting cells also helps counter gravity.

Describe how properties of water contribute to the upward movement of water in a tree

The glycoprotein would be synthesized in the ER lumen, move through the Golgi apparatus, and then travel in a vesicle to the plasma membrane, where it would undergo exocytosis and become part of the ECM.

Describe the cellular pathway of synthesis and deposition of an ECM glycoprotein.

One of two compounds that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon

Enantiomers isomers

High humidity hampers cooling by suppressing the evaporation of sweat.

Explain the saying "It's not the heat; it's the humidity."

Due to its two polar covalent bonds, a water molecule has four regions of partial charge: two positive regions on the two hydrogens and two negative regions on the oxygen atom. Each of these can bind to a region of opposite partial charge on another water molecule.

Explain why the central water molecule can hydrogen bond to four (rather than three or five) other water molecules.

The pH of the water should decrease from 7 to about 2 (as mentioned in the text); the pH of the acetic acid solution will decrease only a small amount, because as a weak acid, it acts (like carbonic acid) as a buffer.

Given a liter of pure water and a liter solution of acetic acid, what would happen to the pH, in general, if you added 0.01 mol of a strong acid to each?

[H+] = 0.01 = 10^-2 M, so pH=2

HCl is a strong acid that dissociates in water: HCl→H+ (+) Cl− What is the pH of 0.01 M HCl?

Both consist largely of hydrocarbon chains, which provide fuel—gasoline for engines and fats for plant embryos and animals. Reactions of both types of molecules release energy

How are gasoline and fat chemically similar?

As water freezes, it expands because water molecules move farther apart in forming ice crystals. When there is water in a crevice of a boulder, expansion due to freezing may crack the boulder.

How can the freezing of water crack boulders?

CO2 is a nonpolar molecule that can diffuse through the plasma membrane. As long as it diffuses away so that the concentration remains low outside the cell, it will continue to exit the cell in this way.

How do you think a cell performing cellular respiration rids itself of the resulting CO2?

Nine, with one water molecule required to hydrolyze each connection between adjacent monomers

How many molecules of water are needed to completely hydrolyze a polymer that is ten monomers long?

The grasses living in the cooler region would be expected to have more unsaturated fatty acids in their membranes because those fatty acids remain fluid at lower temperatures. The grasses living immediately adjacent to the hot springs would be expected to have more saturated fatty acids, which would allow the fatty acids to "stack" more closely, making the membranes less fluid and therefore helping them to stay intact at higher temperatures.

How would the membrane lipid composition of a native grass found in very warm soil around hot springs compare with that of a native grass found in cooler soil? Explain.

Polar due to electronegative oxygen. Forms hydrogen bonds with water helping dissolve compounds such as sugars

Hydroxyl group properties

The activity of Paramecium's contractile vacuole will decrease. The vacuole pumps out excess water that accumulates in the cell; this accumulation occurs only in a hypotonic environment.

If a Paramecium swims from a hypotonic to an isotonic environment, will its contractile vacuole become more active or less? Why?

The amino acids in the fish protein must be released in hydrolysis reactions and incorporated into other proteins in dehydration reactions

If you eat a piece of fish, what reactions must occur for the amino acid monomers in the protein of the fish to be converted to new proteins in your body?

One of two or more compounds that have the same numbers of atoms of the same elements but different structures and hence different properties

Isomers

Amino group (-NH2)

Name this functional group

Carbonyl group ( >C=O)

Name this functional group

Carboxyl group (-COOH)

Name this functional group

Hydroxyl group (-OH)

Name this functional group

Phosphate group (-OPO3^2-)

Name this functional group

Contributes negative charge (1- when positioned inside a chain of phosphates, 2- when at the end) When attached, confers on a molecule the ability to react with water, releasing energy. Compound name: Organic Phosphate

Phosphate group properties

The internal environment of a lysosome is acidic, so it has a higher concentration of H+ than does the cytoplasm. Therefore, you might expect the membrane of the lysosome to have a proton pump such as that to pump H+ into the lysosome.

Review the characteristics of the lysosome in Given the internal environment of a lysosome, what transport protein might you expect to see in its membrane?

These pumps use ATP. To establish a voltage, ions have to be pumped against their gradients, which requires energy.

Sodium-potassium pumps help nerve cells establish a voltage across their plasma membranes. Do these pumps use ATP or produce ATP? Explain.

One or two or more compounds that have the same molecular formula but differ in the covalent arrangements of their atoms

Structural Isomers

The oil droplet membrane could consist of a single layer of phospholipids rather than a bilayer, because an arrangement in which the hydrophobic tails of the membrane phospholipids were in contact with the hydrocarbon regions of the oil molecules would be more stable.

Suppose a membrane surrounded an oil droplet, as it does in the cells of plant seeds and in some animal cells. Describe and explain the form it might take.

The two ring forms of glucose are called α and β, depending on how the glycosidic bond dictates the position of a hydroxyl group. Proteins have α helices and β pleated sheets, two types of repeating structures found in polypeptides due to interactions between the repeating constituents of the chain (not the side chains). The hemoglobin molecule is made up of two types of polypeptides: It contains two molecules each of α-globin and β-globin.

Thus far in the chapter, the Greek letters α and β have been used to specify at least three different pairs of structures. Name and briefly describe them.

The four main classes are proteins, carbohydrates, lipids, and nucleic acids. Lipids are not polymers.

What are the four main classes of large biological molecules? Which class does not consist of polymers?

C, H, O, N, S, and P

What are the major elements of life

structural isomers, cis-trans isomers, and enantiomers

What are the three types of isomers

It has both an amino group (-NH2), which makes it an amine, and a carboxyl group (—COOH), which makes it a carboxylic acid.

What does the term amino acid signify about the structure of such a molecule?

Electronegativity is the attraction of an atom for the electrons of a covalent bond. Oxygen is more electronegative than hydrogen creating partial charges on each atom. Opposite partial charges are attracted to neighboring water molecules which will form hydrogen bonds.

What is electronegativity, and how does it affect interactions between water molecules?

Amino Acid structure

What is this

Secondary structure involves hydrogen bonds between atoms of the polypeptide backbone. Tertiary structure involves interactions between atoms of the side chains of the amino acid subunits.

What parts of a polypeptide participate in the bonds that hold together secondary structure? Tertiary structure?

O2 and CO2 are both nonpolar molecules that can easily pass through the hydrophobic interior of a membrane.

What property allows O2 and CO2 to cross a lipid bilayer without the aid of membrane proteins?

The covalent bonds of water molecules would not be polar, so no regions of the molecule would carry partial charges and water molecules would not form hydrogen bonds with each other.

What would be the effect on the properties of the water molecule if oxygen and hydrogen had equal electronegativity?

These are all nonpolar, hydrophobic amino acids, so you would expect this region to be located in the interior of the folded polypeptide, where it would not contact the aqueous environment inside the cell.

Where would you expect a polypeptide region rich in the amino acids valine, leucine, and isoleucine to be located in a folded polypeptide? Explain.

The forms of C4H10 in (b) are structural isomers, as are the butenes (forms of C4H8) in (c)

Which two pairs of molecules are isomers? For each pair, identify the type of isomer.

Human sex hormones are steroids, a type of compound that is hydrophobic and thus classified as a lipid.

Why are human sex hormones considered lipids?

Water is a polar molecule, so it cannot pass very rapidly through the hydrophobic region in the middle of a phospholipid bilayer.

Why is a transport protein needed to move many water molecules rapidly across a membrane?

The hydrogen atoms of one molecule, with their partial positive charges, would repel the hydrogen atoms of the adjacent molecule.

Why is it unlikely that two neighboring water molecules would be arranged like this?

C3H6O3

Write the formula for a monosaccharide that has three carbons.