bio112 exam 1 study questions

What is a triacylglycerol (triglyceride)?

)? Triacylglycerol is a fat molecule composed of a glycerol molecule with three fatty acids attached to each carbon via an ester linkage.

Is water added or removed when triacylglycerol molecules are synthesized?

Synthesis of a triglyceride involves dehydration reactions, so water is removed

How many more electrons are needed to fill carbon's outermost shell?

4 electrons -needs 8 valence electrons in outer shell

Which of the following can be attributed to water's high specific heat?

a lake heats up more slowly than the air around it

Which factor is important in making it possible to cool yourself by sweating? Think carefully!

molecules collide with varied angles and speed, hydrogen bonds are relatively weak

starch: structure: location: function: can humans digest?

structure: helical, both branched and nonbranched location: plants tubers and grains function: energy storage can humans digest?: yes

True or false: a partially positive charged hydrogen atom must be present in a hydrogen bond

true -the partial positive charge in a hydrogen bond must always belong to a hydrogen atom

why is the valence of an atom important for understanding chemical bonding?

valence indicates how many electrons it can share with another atom to make a covalent bond. By knowing the valence of each atom, you can predict which atoms will be bonding partners

what characteristics does silicon share with carbon?

valence, bonds to oxygen, forms polymers with oxygen

Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?

vegetable oil has more double bonds than animal fats -no double bonds in animal fats

Is water a polar or non-polar molecule? Explain your reasoning?

Polar, unequal sharing of electrons, asymmetrical, contains partial positive and partial negative charged atoms

What types of proteins have quaternary structure?

Proteins that are composed of more than one polypeptide have quaternary structure

What four large biological molecules are found in all living organisms?

Proteins, lipids (fats), carbohydrates, and nucleic acids.

Sodas typically contain sugar, flavorings, coloring agents, and carbon dioxide dissolved in water. The best term to describe this mixture would be _____.

an aqueous solution

Steroids are considered to be lipids because they ____.

are not soluble in water/hydrophobic

What type of polysaccharide contains b Glucose monomers? what is the major function of this polysaccharide?

cellulose it is a structural carbohydrate found in plant walls

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

electronegativity

liquid water _____.

has a heat of vaporization higher than that of most other substances

A carbon atom has 6 electrons however, its valency is 4. This is because the carbon atom ________.

has only 2 electrons in its first shell and 4 in the second shell

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

polar

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

polar covalent

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____.

polar covalent bonds

A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a _____.

surface of hydrocarbons

why can some insects walk on water?

surface tension

Which of the following statements is true?

sweating cools the body by converting water into gas

How do phospholipids interact w water molecules?

the polar heads interact w water; the nonpolar tails do not

A polar covalent bond between two atoms results from

two atoms that do not have similar electronegativities.

What is a peptide bond?

A covalent bond between the carboxyl end of one AA and the amine end of another AA.

What is a hydration shell?

A hydration shell is the sphere of water molecules that surrounds solutes when they are dissolved in water?

What is a hydrocarbon? Are these molecules found in living organisms?

A hydrocarbon is a molecule that consists of only hydrogen and carbon No, hydrocarbons are found in fossil fuels. Fossil fuels consist of the partially decomposed remains of organisms that lived millions of years ago.

What is a polysaccharide?

A macromolecule made from ~100 to ~2000+ monosaccharides

How does a protein differ from a linear polypeptide sequence?

A protein forms when a single polypeptide or multiple polypeptides are twisted, coiled and folded into a unique shape. The shape of the protein determines the function of the protein.

What is a hydrogen bond?

A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to a slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.

Wheaton IL is an inland western suburb of Chicago. On any given day in July, why is the land temperature usually cooler at Navy Pier than it is in Wheaton? Can the same trend be seen in December?

As the temperature of land rises during the summer, Lake Michigan absorbs the heat and cools the costal area. Conversely, in winter, when air temperature over land drops, Lake Michigan releases stored heat and warms the costal area.

Beaker A and Beaker B are both filled to capacity with boiling water. Beaker A has a total volume of 500 ml while Beaker B has a total volume of 2 liters of water. Which beaker contains water with the greatest amount of heat?

Beaker B. While both beakers contain water at the same temperature (100 °C), Beaker B has 4 times the volume of water as Beaker A.

which of the following is a hydrocarbon?

C3H8

Which three classes of large molecules are composed of monomers linked by covalent bonds?

Carbohydrates, Proteins, and Nucleic Acids are made up of linked monomers. Fats such as triacylglycerol are abit more complex (3 fatty acid chains connected to a glycerol molecule).

Using the structure of urea, explain how the arrangement of its atoms completes the valance shell of all the atoms in the molecule.

Carbon has a valance of 4, and in this molecule it forms 4 covalent bonds (2 single, 1 double). Oxygen has a valance of 2 and in this molecule it forms 2 covalent bonds (1 double bond). Nitrogen has a valance of 3, and in this molecule it forms 3 covalent bonds Hydrogen has a valance of 1, and in this molecule it forms 1 covalent bond

. Cite examples of two proteins with quaternary structure

Collagen and transthyretin

Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?

Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge

Why does sweating help cool the skin?

Energy (heat) is needed to break the hydrogen bonds in liquid water. The water molecules with the most kinetic energy (heat) are the ones that leave the skin surface as water vapor. The liquid water molecules that remain behind on the skin have less kinetic energy (less heat). Thus the surface of the skin cools.

What types of bonds contribute to the tertiary structure of a peptide?

Hydrogen bonds, disulfide bonds, ionic bonds and/or hydrophobic interactions

Scientists have observational evidence suggesting that water, in either its solid, liquid, or gas phase, is present throughout the solar system. Why is it not surprising that water is found on so many planets and moons?

Hydrogen is the most abundant element in the universe, followed by helium and oxygen. Water's molecular formula is H2O

Buffers contain a weak acid and its corresponding base. Cite an example of a blood buffer that is a weak acid and identify its corresponding base?

In blood, Carbonic Acid (H2CO3) is a weak acid (donates H+) and the Bicarbonate ion (HCO3-) is its corresponding weak base (accepts H+).

What is the definition of an isomer

Isomers are compounds with the same molecular formula but different structures and properties.

Why is a polypeptide considered a polymer?

It is composed of amino acid monomers linked by a covalent, peptide bond.

When the airways of the lungs become partially blocked, failure to properly ventilate the lungs can occur. This change in ventilation can cause acute respiratory acidosis, a condition where the blood pH decreases slightly (7.35) for a short period of time. Explain how the blood buffer, carbonic acid, and its corresponding weak base, bicarbonate ion, function to quickly return the pH of the blood to normal physiological levels (7.4).

Once [H+] increases in the blood, the bicarbonate ion (HCO3-) accepts H+ to form carbonic acid (H2CO3), which decreases [H+] and thus increases the pH of the blood. See slide from Chapter 3 handout.

In a water molecule, why does the oxygen atom carry a partial negative charge, and why do each of the two hydrogen atoms carry a partial positive charge?

Oxygen (O) is more electronegative than hydrogen (H). This means that an oxygen atom has a stronger ability to attract electrons towards itself than a hydrogen atom. The shared electrons in an O-H covalent bond are pulled towards oxygen causing a partial (-) charge on this atom. In contrast, the pull of these shared electrons away from hydrogen cause this atom to have a partial (+) charge.

In water, why does the oxygen atom have partial negative charges and why do the hydrogen atoms have partial positive charges?

Oxygen has a higher electronegativity than hydrogen (3.5 vs. 2.1). Thus the shared electrons in the O-H covalent bond are pulled towards oxygen and away from hydrogen. The oxygen atom in water holds the shared electrons much more strongly than hydrogen atoms. The pulling of the electrons from hydrogen closer to oxygen moves oxygen closer to having a full octet (e.g. 8 electrons in its valence shell), which is very stable and favorable

L-dopa is used to treat ______.

Parkinson's disease

Where would you find phospholipids in a cell?

Phospholipids make up the plasma membrane of a cell. They are arranged in a bi-‐layer with the hydrophilicheads facing outward (in contact with the cytoplasm of a cell or the aquatic environment surrounding the cell) and the hydrophobic tails facing inward (in contact with each other). Phospholipids are also present within the membranes of organelles.

Why are hydrocarbons insoluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages.

How much more acidic is the gastric juices of the stomach lumen compared to the cytosol of parietal cells found in the villus of the stomach?

The pH of gastric juices is 2 while the pH of the cytosol of a parietal cell is 7. However, the gastric juices of the stomach are 100,000 times (10-2 ÷ 10-7 = 105) more acidic than the cytosol of parietal cells.

How do estradiol and testosterone differ biologically?

While both of these steroids play numerous reproductive and developmental roles in humans (and most vertebrates), estradiol is critical for female reproduction and development while testosterone is a critical for male reproduction and development

the open space in water's crystal structure makes it possible for...

aquatic life to exist at the North Pole

Enantiomers are molecules that _____.

are mirror images

Which of the molecules from the question above can often be composed of C, H, and O alone?

carbohydrates and lipids

What are the four classes of large molecules discussed in chapter 5?

carbohydrates, lipids, proteins, nucleic acids

saturated fat double bonds? cis or trans double bonds? example:

double bonds? no cis or trans double bonds? no example: butter (animal fat)

unsaturated fat double bonds? cis or trans double bonds? example:

double bonds? yes cis or trans double bonds? cis example: olive oil (plant fat)

hydrogenated double bonds? cis or trans double bonds? example:

double bonds? yes (hydration procedure produces mostly saturated fatty acids but also a few unsaturated fatty acids cis or trans double bonds? trans example: margarine, crisco (hydrogenated plant fat)

The brackets are indicating a(n) _____ bond.

hydrogen

What name is given to the bond between water molecules?

hydrogen

If the pH is too high, the goal of the buffer is to...

increase the concentration of H+ -buffer acts as acid to correct for extra OH- concentration in solution

Which has more heat: water in a lukewarm swimming pool or boiling water in a teacup?

swimming pool - heat based off of volume - pool has larger volume than teacup so total will be higher

which components of the phospholipid are hydrophobic

tails

Which has the highest temperature: water in a lukewarm swimming pool or boiling water in a teacup?

teacup - temperature not dependent upon volume

How does the pH of the solution on the right compare with that of the solution on the left?

the solution on the right is basic relative to the solution on the left

What is carbon's valence? why does this number make carbon such a major component of organic molecules?

4 Carbon can readily form up to 4 covalent bonds with four other atoms or molecules. This allows for an enormous amount of molecular diversity

What two monosaccharide monomers make up maltose, lactose, and sucrose?

- glucose and glucose -galactose and glucose -glucose and fructose

how does silicon differ from carbon?

-carbon oxidizes to carbon dioxide gas. silicon oxidizes to solid silica -carbon can be stored in carbohydrates and oxidized to water and carbon dioxide to release energy. the energy is released in small, manageable amounts at regulated times by enzymes. this fine tuned regulation requires a variety of different complex carbon based molecules that can differ based on handedness (isomers). Silicon is unable to give rise to a wide array of isomers and those found are highly unstable and reactive (energy released in large, unmanageable amounts)

What type of bond is present in maltose?

1,4 glycosidic bond

what is the valence of silicon?

4

What is the pH of an aqueous solution with the hydronium ion concentration [H3O+] = 2 x 10^-14 M ?

13.7

What is the valence of sulfur?

2 -two electrons needed to balance out the outer shell

What is the maximum number of hydrogen bonds one molecule of water can form?

4 hydrogen bonds -there are 4 total regions of partial charge in a water molecule so there is the possibility of up to 4 hydrogen bonds forming

The secondary structure of a protein is determined by the weak bonds that form between parts of the backbone of a peptide. What are the names of the two structures that contribute to the secondary structure of a protein?

Alpha helix and Beta sheets.

Carbonated cola is more acidic than coffee or even orange juice because cola contains phosphoric acid. What is the molar concentration of [H3O+] in a cola that has a pH of 3.120?

7.59 × 10^-4

What is the name of the monomer unit in each of these large molecules? (carb, protein, nucleic acid)

? Monosaccharide (carbohydrates); Amino Acids (protein); Nucleotide (nucleic acids).

What is electronegativity?

A chemical property that describes the ability of an atom to attract electrons towards itself. This is a calculated value

Why is alanine categorized as a nonpolar amino acid and serine categorized as a polar amino acid?

Alanine's R group is a methyl group (-CH3) which is non polar, while Serine's R group has a hydroxyl group (-OH) which is polar

peptide bond is analogous to what type of bond in carbohydrates?

glycosidic linkage

What is a buffer?

Buffer: Substances that allow biological fluids to maintain a relatively constant pH despite additions of acids or bases.

Ribose is a carbohydrate containing five carbons. What is its molecular formula?

C5H10O5

Order the following atoms from the one with the lowest electronegativity (1) to the one with the highest electronegativity (C, N, O, H)

C: 2 H: 3 O: 4 H: 1

Molecules with the samesequence of covalent bonds, but different spatial arrangementdue to the inflexibility of adouble bond

Cis-Trans isomers Also called geometric isomers

Why is glutamic acid categorized as an acidic amino acid and lysine categorized as a basic amino acid?

Glutamic Acid's R group has a carboxyl group that readily donates a H+, while Lysine's R group has an amine that readily accepts a H+.

In terms of a water molecule, what is the difference between cohesion and adhesion? Use water droplets forming on a spider web to help explain these properties of water.

Cohesion: Water droplets are generated when water molecules form hydrogen bonds with other water molecules. Adhesion: Water droplets adhere to the spider web when the partial negative or partial positive charges on water molecules form hydrogen bonds with polar and/or ionic regions of the silk protein found in the spider web.

Where are ester linkages found in a triacylglycerol?

Ester linkages are formed between the -OH group of glycerol and the -COOH group of a fatty acid.

Using the atomic symbol, which element is the most electronegative?

F -trend for electronegativity: increases across periodic table and decreases when going down the periodic table

What type of weak bond stabilizes the secondary structure of a protein?

H-bonds between the partial negative charge of the H atom of the N-H covalent bond and the partial negative charge of the O atom of the C=O covalent bond

Cite at least two ways that heat differs from temperature

Heat is a form of energy while temperature is not. Heat cannot be measured directly while temperature can be measured directly with a thermometer

Which atom wins? Is ammonia a nonpolar or polar molecule?

N; polar -electronegativity values result in a difference of 0.9 (3.0-2.1) which is within the polar range

Which type of biological reaction requires a water molecule?

hydrolysis

Why does ice float in liquid water?

Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water.

Sugar dissolves when stirred into water. Match each component to the correct terminology

Sugar → solute Water → solvent Sweetened water → solution

Why is a saturated fatty acid that is composed of 18 carbons slightly less hydrophobic than a hydrocarbon that is composed of 18 carbons?

The carboxyl group at the end of the fatty acid is polar. A hydration shell can form around this part of the molecule

In general, as you move up a group or column of the periodic (bottom to top), how does the electronegativity of the atoms change? Why

The electronegativity will increase until you reach the inert atom. The bonding pair of electrons have less distance to the nucleus.

In general, as you move across a row of the periodical table (left to right), how does the electronegativity of the atoms change? Why?

The electronegativity will increase until you reach the inert atom. The increase in the of the number of positive charged protons in the nucleus will greater attract the bonding pair of electrons.

Use the drugs ibuprofen and albuterol to explain the pharmacological importance of isomers.

The enantiomers of ibuprofen and albuterol have different effects. Ibuprofen reduces inflammation and pain and sold as a mixture of the S and R forms, however the S form is 100X more effective. Albuterol relaxes bronchial passages in asthma patients. Albuterol must be sold in the active R form, because the S form counteracts the active form.

Cite an example of an organic molecule found in living organisms that contains stretches of hydrocarbons.

The fatty acids that are found in a triglyceride (triacylglycerol) have long stretched of hydrocarbons.

What is the primary structure of a protein?

The primary structure of a protein is its genetically coded sequence of AA. Each amino acid is connected by a covalent peptide bond

What is unique about the hydrogen bonds present in liquid water?

These bonds are very fragile and break easily (1/20th the strength of a covalent bond). Liquid water is constantly moving and forming, breaking, and reforming hydrogen bonds with different water molecules.

Why are lipids considered hydrophobic molecules?

They contain hydrocarbons, which are molecules composed of only nonpolar C-‐H covalent bonds

Why do He, Ne, and Ar have no electronegativity value?

They have a full outer shell -noble gases have a full outer shell so they do not need to attract electrons. Therefore, electronegativity is not needed.

Why did I use a picture of a polar bear standing on an iceberg to reinforce the key concept that water is critical for life on earth?

Water is abundant on earth. It covers ~75% of earth's surfaces and it exist in three phases (gas, liquid, and, solid). An organism's cells are surrounded by water and the content of water in cells varies from 70 to 95%. The unique chemical properties of water make the external environment livable. These properties also make the internal environment of organisms well-suited to the chemical and physical processes of life.

All of the following statements help to explain why water molecules form hydrogen bonds except:

Water is an electronegative molecule.

Which statement helps to explain why ice is less dense than liquid water?

Water molecules make hydrogen bonds at definite angles, Cold molecules move less than warm molecules.

Why are scientists excited when water is discovered on a different planet?

When water is located on different planets within our solar system, it leads to the speculation that chemistry capable of nourishing life could also exist on these planets.

The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called?

a hydrogen bond

Dissolving is best described as ...

a mingling of molecules and/or ions.

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

a water molecule can make 4 hydrogen bonds

Hydrogen bonding between water molecules creates a structural organization that leads to the four emergent properties of water. What are these four properties?

a. Water has cohesive behavior b. Water has the ability to moderate temperature c. Water expands upon freezing d. Water is a versatile solvent

The large diversity of shapes of biological molecules is possible because of the extensive presence of _____ in the molecules.

carbon

These molecules are _____.

cis-trans isomers (geometric isomers)

Water molecules can form hydrogen bonds with _____.

compounds that have polar covalent bonds

A carbon atom is most likely to form what kind of bond(s) with other atoms?

covalent

An increase in pH means that the concentration of H+ has ____.

decreased -higher pH means more OH- concentration

What type of biochemical reaction is involved in the synthesis of polymers?

dehydration

What type of reaction is it when removing water from two monosaccharides to form a disaccharide?

dehydration

Which type of biological reaction generates a water molecule?

dehydration

what type of reaction creates a peptide bond?

dehydration

What type of reaction is involved in the attachment of the fatty acid to glycerol?

dehydration -a building reaction = dehydration reaction

Cis-trans isomers (geometric isomers) are molecules that _____.

differ in the arrangement of their atoms about a double bond

Which of these bonds is the strongest? Why?

disulfide bridge It is a covalent bond that forms between two cysteine AAs. The bond is between the two sulfhydryl groups

Left and right handed versions of the same molecule.

enantiomers

these molecules are ______.

enantiomers

What type of bond connects each fatty acid to the glycerol molecule?

ester linkage

True or false: a partially negative charged oxygen atom must be present in a hydrogen bond

false -the partial negative charge doesn't HAVE to belong to an oxygen atom, it could belong to something else

What are the three major types of lipids?

fatty acids, phospholipids, steroids

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

four...hydrogen

When glucose is dissolved in water, how does its structure change?

glucose forms a ring structure between C1 and the O on C5

What two types of polysaccharides contain alpha Glucose monomers? what is the major function of these two polysaccharides?

glycogen and starch energy storage

Which component of the phospholipid is hydrophilic

head

Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____

high specific heat

Water is a source of ______________ for chemical reactions in cells.

hydrogen and oxygen atoms

In terms of its strength, how does a hydrogen bond compare to a covalent bond?

hydrogen bond is weaker

water has surface tension because...

hydrogen bonds between surface water molecules resist being stretched.

what is the arrow pointing to?

hydrogen ion

In a neutral solution the concentration of _____.

hydrogen ions is equal to the concentration of hydroxide ions

What type of biological reaction is involved in the breakdown of polymers?

hydrolysis

what is the arrow pointing to?

hydroxide ion

The amount of energy that must be absorbed or lost to raise or lower the temperature of 1 g of liquid water by 1°C _____.

is 1 calorie

Which statement is true of water's tensile strength?

it results from hydrogen bonding, it helps pull water through plants, it involved both cohesion and adhesion

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

it takes energy to break hydrogen bonds

The kind and number of bonds an atom can form depends on ________.

its electron configuration

will nonpolar bonds form H-bonds with water?

no

The lower the pH of a solution, the _____.

more acidic the solution -low pH = acidic -high pH = basic

based on the similarities and differences of silicon and carbon, is a silicon based life possible?

no, life requires us to collect, store, and utilize energy from the environment. we ingest a variety of complex carbohydrates and then break them down in small units to release energy when we need it. the components we don't use can be stores for energy use later. the lack of variety of complex silicon compounds makes it difficult to have a similar model. isomers found are highly unstable (energy released in on large burst). even if silicon compounds can be broken down in small, manageable steps, the final product of oxidation is a solid which is more problematic for an organism to dispose of.

what kind of effect does R-dopa have on Parkinson's disease?

none

Is molecular oxygen a polar or nonpolar molecule?

nonpolar -molecular oxygen is 2 oxygens together, so the electronegativity difference between the two atoms is 0. Therefore, the molecule is nonpolar

Is C-H polar or nonpolar? (C electronegativity=2.5 and H electronegativity=2.1)

nonpolar 2.5 - 2.1 = 0.4

Bonds between two atoms that are equally electronegative are _____.

nonpolar covalent bonds

Hydrophobic substances such as vegetable oil are _____

nonpolar substances that repel water molecules

Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S will _____.

not form hydrogen bonds with each other

This pair of molecules are _____.

not isomers

A covalent bond is likely to be polar when ________.

one of the atoms sharing electrons is more electronegative than the other atom

what are the four major atomic components of an organic molecule?

oxygen, nitrogen, hydrogen, and carbon

what life supporting metabolic process requires water?

photosynthesis

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

polar groups attract one another

why doesn't oil mix with water?

polar molecules attract one another

Based on your knowledge of the polarity of water molecules, the solute molecule depicted is most likely ________.

positively charged

you disrupt all hydrogen bonds in a protein. what level of structure will be preserved?

primary

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

single (non polar) covalent

An atom has four electrons in its valence shell. What type(s) of covalent bonds is it capable of forming with oxygen?

single and double bonds

amount of heat absorbed or lost when 1g of a substance changes its temperature by 1 *C

specific heat

Molecules that differ in the covalent arrangements of atoms

structural isomers

These molecules are _____.

structural isomers

cellulose: structure: location: function: can humans digest?

structure: flat, forms microfibrils location: plant cell walls function: structural can humans digest?: no

glycogen: structure: location: function: can humans digest?

structure: helical, only branched location: liver cells function: energy storage can humans digest?: yes

What part of an amino acid forms these bonds?

the R groups

What is the difference between starch and glycogen?

the amount of branching that occurs in the molecule

electronegativity is...

the attraction of an atom for the electrons in a covalent bond.

The complexity and variety of organic molecules is due to _____.

the chemical versatility of the carbon atoms

The partial negative charge in a molecule of water occurs because _____.

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

define valence

the number of unpaired electrons required to complete the atom's outermost shell (or the number of covalent bonds an atom can form

What do all three types of lipids have in common?

they all contain hydrocarbons

The steroids estradiol and testosterone look very similar. What do these two molecules have in common? How do these two molecules differ structurally?

they both have a common steroid nucleus Estradiol has a hydroxyl group added to the steroid nucleus. Testosterone has a carbonyl group and a methyl group added the steroid nucleus

will polar bonds form H-bonds with water?

yes

Do cis-trans isomers have the same molecular formula?

yes -they are isomers so by definition they have the same molecular structure