Mastering Assignment 3 : lipids and membranes

Which of the following helps most to explain why water has a high specific heat?

(a) A water molecule can make 4 hydrogen bonds.-When you heat water, much of the heat is used to break hydrogen bonds. Only the remaining heat can increase molecular motion, raising the temperature.

The open spaces in water's crystal structure make it possible for ...

(a) aquatic life to exist at the North Pole.-The openings in the lattice make ice less dense than liquid water, so it floats. That causes water to freeze from the top down, so there's always liquid in which organisms can live.

Which statement is true of water's tensile strength? Which statement is true of water's tensile strength?(a) It results from hydrogen bonding.(b) It helps to pull water through plants.(c) It involves both cohesion and adhesion.Both (a) and (b).(a), (b), and (c).

(a), (b), and (c).-Because of hydrogen bonding, water coheres to itself and adheres to cell walls. That makes it possible to pull water through plants without breaking the water column.

Why doesn't oil mix with water?

(c) Polar molecules attract one another.-Water molecules cling to one another and won't part to make room for uncharged (nonpolar) molecules. There's no repulsion.

The table shown here lists the specific heat of several substances. Based on the information in the table, which of the following statements are true? Select all that apply.

-Sulfuric acid is less resistant to temperature change than water. -Benzene is more resistant to temperature change than sulfuric acid. -Water has a high specific heat due to the hydrogen bonding between water molecules. -More heat is required to raise the temperature of 1 g of water 1 ∘C∘C than to raise the temperature of 1 g of ethyl alcohol 1 ∘C∘C.

In the molecule below, how many atoms could make hydrogen bonds with water?

10-The 10 atoms that can form hydrogen bonds with water are the 4 oxygens and 2 hydrogens around the phosphorus atom, the 2 oxygens double-bonded to carbon atoms, and the oxygen and hydrogen (the hydroxyl group) bonded to carbon. Your ability to predict hydrogen bonding will be a great help in understanding the central processes of life.

Which molecule is less soluble in water--a fat or a phospholipid? Why?

A fat molecule is less soluble in water because it has three non-polar fatty acids and no polar or charged head like a phospholipid has-The replacement of one of the fatty acids with a polar chemical group makes phospholipids more soluble in water than fats

Which statement about a methyl functional group is correct?

A methyl group consists of a carbon covalently bonded to three hydrogen atoms.

Which one of these is an amino group?

A(NH2)

Which of the functional groups behaves as a base?

A, the electronegativity of nitrogen means that amino groups tend to pick up hydrogen ions

Which of these is a phosphate group?

B Of the choices, this is the only one that contains phosphorus.

Which of these groups plays a major role in energy transfer?

B- Phosphate groups are a component of ATP.

Which of these is a hydroxyl group?

D This is a hydroxyl group.

Which of these functional groups is characteristic of alcohol?

D-Hydroxyl groups are characteristic of alcohol

What type of bond joins the carbon atom to each of the hydrogen atoms?

single (nonpolar) covalent (Each carbon-hydrogen bond involves a single pair of equally shared electrons.)

Which of these is a carboxyl group?

F This is a carboxyl group

Which of functional groups listed below behaves as an acid?

F-By donating hydrogen ions, carboxyl groups act as an acid.

Which of these bonds is weakest?

Hydrogen Bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges. (4th one)

Why isn't this insect drowning?

surface tension-The high surface tension of water allows the insect to remain on the surface.

which of these is a phospholipid?

Phospholipids are composed of a phosphate group, a glycerol, and fatty acids. (last one in this picture)

How many fatty acids are in a phospholipid?

two-Two fatty acids are attached to the glycerol and make up the tails of the phospholipid.

Which of these is NOT a lipid?

RNA;RNA is a nucleic acid

Label the following diagram of water molecules, indicating the location of bonds and the partial charges on the atoms. Drag the labels to their appropriate locations on the diagram of the water molecules below. Labels can be used once, more than once, or not at all.

The image on the left shows the unequal sharing of electrons in a water molecule. Notice that the electrons are pulled toward the oxygen atom, which is more electronegative than a hydrogen atom, resulting in a partial negative charge (δ−δ−) on the oxygen atom and a partial positive charge (δ+δ+) on each hydrogen atom. The image on the right shows hydrogen bonding between two water molecules: the partially negative oxygen atom of one water molecule is attracted to the partially positive hydrogen atom of another water molecule. Hydrogen bonds are much weaker than covalent bonds. In liquid water, hydrogen bonds last only a fraction of a second, breaking and re-forming with great frequency. In a given instant, one water molecule can be hydrogen bonded to up to four other water molecules.

Dissolving is best described as ...

a mingling of molecules and/or ions.-When sugar dissolves in water, the sugar molecules remain intact but mingle with water molecules. When salt (NaCl) dissolves, its Na+ and Cl- ions separately mingle with water.

Polar attractions are ...a) forces between atoms with partial charges.(b) weaker than covalent bonds.(c) important because they are numerous.(a) and (b) are true. (c) is false.(a), (b), and (c) are correct

a), (b), and (c) are correct -Polar attractions occur between atoms with partial charges and are weaker than covalent bonds. Still, they're important because so many of them occur in living cells.

Which property of water allows a paper towel to pick up a puddle of water?

adhesion of water molecules to other kinds of molecules-Water adheres to the cellulose molecules in a paper towel, allowing the towel to pick up a puddle of water. This is similar to the adhesion between water molecules and cellulose in cell walls responsible for water transport in plants.

classify each statement as an example of adhesion, cohesion, or surface tension. Drag each statement to the appropriate bin.

adhesion: Water molecules cling to the side of a beaker. Water molecules cling to plant cell walls. cohesion: Water molecules are attracted to each other. A drop of water spilled on a table forms a drop on the table, rather than spreading out over the surface. surface tension: A sewing needle floats when it is placed gently on top of water in a bucket. A water strider runs across a pond without breaking the surface.

What holds phospholipids together in a bilayer formation?

hydrophilic and hydrophobic interactions with water-The hydrophobic tails interact with each other and are repelled by water, while the heads are hydrophilic and are attracted to water. This dual nature causes groups of phospholipids to assemble into distinct layers to minimize tail contact with water and maximize head contact with water.

A(n)_________is a chemical bond resulting from the attraction between atoms that have acquired a charge due to losing or gaining one or more electrons.

ionic bond

Though you add heat, the temperature of boiling water remains constant because ...

it takes energy to break hydrogen bonds.-At boiling, all the added heat is used to break hydrogen bonds. Free of the water mass, the departing steam carries away all the added energy, with none left over to raise the temperature.

What functional feature(s) does the phosphate group contribute to the structure of a phospholipid?

negative charge to interact with waterplace to attach another small charged molecule-The phosphate attaches to the glycerol and provides a place for another small molecule to attach to the phospholipid. The phosphate has a charge, so it interacts with polar water molecules.

Which of these is rich in unsaturated fats?

olive oil-Olive oil is a plant oil, and most plant oils are rich in unsaturated fats.

How many atoms in the pictured molecule can form hydrogen bonds with water molecules?

5-O and N can make hydrogen bonds, as can each H attached to O or N.

In this molecule, what type of bond is found between the oxygen and hydrogens?

polar covalent-While oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.

Which statements about hydrogen bonding in water are true?

Because oxygen is more electronegative than hydrogen, the electrons of the covalent bond between oxygen and hydrogen spend more time around the oxygen atom. The unequal distribution of charge in a water molecule results in a partial negative charge around the oxygen atom and a partial positive charge around the hydrogen atoms. Hydrogen bonding occurs between the partially negative oxygen atom of one water molecule and the partially positive hydrogen atom of another water molecule.

Which of these images shows the correct orientation of phospholipids in a biological membrane?

Biological membranes are made of phospholipids that have assembled with the polar heads facing out to interact with the water, and the non-polar tails pushed together in the interior of the membrane.

Water is a source of ______________ for chemical reactions in cells. Water is a source of ______________ for chemical reactions in cells.(a) hydrogen atoms(b) oxygen atoms(c) energyBoth (a) and (b)(a), (b), and (c).

Both (a) and (b)-Many reactions incorporate O and H from water into biological molecules. This happens when you digest starch and protein, for example.

Which factor is important in making it possible to cool yourself by sweating? Think carefully!(a) Molecules collide with varied angles and speeds.(b) Hydrogen bonds are relatively weak.(c) Water has more energy at the body surface.Both (a) and (b).(a), (b), and (c

Both (a) and (b).-Random collisions allow some molecules to accumulate more energy than other molecules. The weakness of hydrogen bonds lets those molecules escape, leaving the cooler molecules behind.

Which statement helps to explain why ice is less dense than liquid water? Which statement helps to explain why ice is less dense than liquid water?(a) Water molecules make hydrogen bonds at definite angles.(b) Cold molecules move less than warm molecules.(c) Hydrogen bonds lengthen in the cold.All of the above.Both (a) and (b).

Both (a) and (b).-The ice lattice has open spaces because of the angles at which hydrogen bonds form. Heat energy can break water molecules free of the lattice so they move into the openings.

Which of these is a carbonyl group?

C This is a carbonyl group.

A function of cholesterol that does not harm health is its role _____.

as a component of animal cell membranes-Cholesterol is an important component of animal cell membranes.

Hydrogen bonds ...can form between H and N.share electrons between the two bonded atoms.are covalent bonds.occur within a water molecule.All of the above.

can form between H and N-They can also form between H and other highly electronegative atoms, such as O, if the atoms have strong partial charges.

A(n)_______is a chemical bond in which two atoms share one or more pairs of valence electrons.

covalent bond

Which of these groups is characteristic of thiols?

e, thiols are characterized by the presence of a sulfhydryl group

The tendency of an atom to pull electrons toward itself is referred to as its _____.

electronegativity

A water molecule can bond to up to _____ other water molecules by ____ bonds.

four ... hydrogen

A(n)__________is a weak chemical bond that is formed when the partially positive hydrogen atom of a polar covalent bond in one molecule is attracted to the partially negative atom of a polar covalent bond in another molecule.

hydrogen bond

Water has surface tension because ...

hydrogen bonds between surface water molecules resist being stretched.-The hydrogen bonds between surface water molecules are normally slightly stretched. Like a stretched sheet of rubber, the surface tends to contract and resists being penetrated.

Which of these figures correctly illustrates the nature of the bonding of H2O?

oxygen is slightly negative while the H2Os are slightly positive

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?

polar groups attract one another- Polar water molecules pull together, holding the polar parts of the amphipathic molecules and squeezing out the nonpolar parts. That leaves the nonpolar parts waving in the air.

The unequal sharing of electrons within a water molecule makes the water molecule _____.

polar- The electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.

This figure is an example of a(n) _____.

saturated fat, The fatty acid tails lack double bonds.