CHEM 361 Exam 1

The hydrogen and oxygen atoms in water are bound together by what type of strong chemical bonds?

polar covalent bonds

Each molecule of water can form a maximum of _ H-Bonds

4

Which of the following is not a property of water responsible for its unique characteristics?

• The strength of its covalent bonds.

• The shape of the water molecule.

• Its polar nature.

• Its capacity to form hydrogen bonds.

• The strength of its covalent bonds.

Liquid water is less dense than solid water (ice). T/F

F

Which of the following substances does water not dissolve?

• Polar

• Ionic

• Nonpolar

Nonpolar

Polar molecules are often (hydrophobic/hydrophilic) , while nonpolar molecules are often (hydrophobic/hydrophilic).

Hydrophilic, hydrophobic

The Bronsted -Lowry definition defines an acid as

Proton donor

The extent to which a weak acid dissociates in solution is described by its

K_a

Which of the following is NOT a property of an effective buffer.

 

• contains equal concentrations of weak acid and its conjugate base

• has a pH equal to its pKa

• has a high Ka

Has a high Ka

What equation would you use to calculate the pH of a solution given the concentration of H+?

-log(H+)

Is the HHb equation acid/base or base/acid

base/acid

The pKa of lactic acid is 3.86. Predict whether lactic acid will be intact (remain in the weak acid form) or dissociate when the pH of your muscles equilibrates back to 7.2 after recovering from a heavy workout.

It will dissociate

What gives water its special properties?

Its polarity and ability to form hydrogen bonds (the structure contributes to this).

What makes water good biologically?

• Its partial charges all it to dissolve many polar molecules and ionic compounds

• Can absorb/release a lot of heat to manage temp

• Requires a lot of energy to evaporate which allows for cooling systems like sweating.

Strong acids have a (big/small) Ka?

Big

Weak acids have a (big/small) pKa?

Big

Will an acid disassociate in a solution with a lower pH than its pKa?

No

How do human bodies use buffers?

Bicarb in the blood manages blood pH and prevents alkalosis or acidosis.

Why are weak interactions useful in organisms?

Biological functions need to be reversible and weak interactions allow for that.

Why doesn’t CH3CH3 dissolve in water but CH3CH2OH does?

Ethane is non polar and ethanol is polar.

You know the Keq of a chemical reaction that occurs in a human cell when the individual is healthy (assuming they are not fevered). This allows you to calculate the _______________ of the chemical reaction?

∆G'°

The ____________________ of a chemical reaction is a measure of a number of properties associated with that reaction in a given environment including: 1) the basic chemical structure and energy associated with those structures under constant conditions, 2) the temperature at which the reaction is occurring, and 3) the concentration of products/reactants of the reaction.

∆G

What parameters of the Gibbs free energy equation (∆G = ∆G^o + RTlnQ) might be altered within a cell to change the overall ∆G of an acid dissociation reaction?

pH

T

Q

∆G'°

Keq

pH, T, Q

A reaction at equilibrium will alter the way in which Gibb's Free energy is calculated. Of the following choices, which is correct?

 

At equilibrium, Q = 1 and ∆G = 0

 

At equilibrium, Q = Keq and ∆G = 1

 

At equilibrium, Q = Keq and ∆G = 0

 

At equilibrium, ∆G^o = 0 and Keq = 1

At equilibrium, Q = Keq and ∆G = 0

A reaction with a -∆G will always occur rapidly and spontaneously. T/F

F, yes spontaneous but does not say anything abt speed.

Which of the following nonspontaneous chemical reactions could ATP hydrolysis power if it were coupled to the reaction?

ATP hydrolysis = -∆G 30.5kj/mol

 

One with a ∆G of -15.5kj/mol

 

One with a ∆G of -31kj/mol

 

One with a ∆G of 29.5kj/mol

 

One with a ∆G of 33.5kj/mol

One with a ∆G of 29.5kj/mol

ATP is less stable than its hydrolyzed products due to

1) Repulsion of negative charges of phosphates on ATP

2) Unattached phosphate groups have more resonance structures

3) Water stabilizes ADP and Pi better

One method that a cell could use to drive a nonspontanous chemical reaction would be to employ the use of an enzyme to catalyze the reaction. T/F

F

The second law of thermodynamics can explain that

 

the disorder of the universe is always increasing.

 

the spontaneity of a reaction is affected by the change in entropy of a reaction.

 

a reaction with a -∆G value will occur spontaneously.

 

all of the above.

all of the above

What is the first law of thermodynamics?

Energy/mass cannot be created nor destroyed

What is the second law of thermodynamics?

The entropy of the universe is always increasing

Spontaneous rxs have a (- / +) delta g, are (exergonic/endergonic), (build/break) stuff, and (increase/decrease) entropy.

-, exergonic, break, increase

How can cells alter spontaneity?

Alter temp
Alter conc. of reactants or products
If acid disassociation, change pH

What rules are required for coupled rxns?

1) exergonic rxn must release >/= energy than the endergonic rxn it is powering.

2) both rxns must share an intermediate

How does ATP hydrolysis work in simple terms?

Water breaks off a phosphate group from ATP which makes it ADP.

What three factors are used to classify monosaccharides?

aldose/ketose
# carbons
isomeric form

What is an aldose vs a ketose

Aldose has double bond to oxygen on C1 while ketose has double bond to oxygen on C2

What are constitutional vs stereoisomers?

Constitutional isomers has atoms attached in different places, stereoisomers vary in how they are oriented in space.

What are enantiomers vs diastereomers?

Enantiomers are mirror images, diasteromers are not.

What are epimers or anomers?

Epimers are in linear form and differ at chiral carbons, anomers are only present in rings.

How can you determine the number of possible stereoisomers?

2^n, n being the number of chiral carbons

D-isomers are ______ and L-isomers are ______

Vertebrates, non vertebrates

A 6 membered ring is a _____ and a 5 membered ring is a ______

pyranose, furanose

How are rings formed?

OH group further from carbonyl carbon attacks the carbonyl carbon. Oxygen that was part of the hydroxyl group now becomes part of the ring and carbonyl group loses its double bond to oxygen.

How can you differentiate between an aldose ring and ketose ring?

What was the carbonyl carbon will have an H and OH if an aldose and a CH2OH and OH if a ketose.

What are alpha and beta isomers?

Alpha = -OH on anomeric carbon points opposite way of attacking carbon’s OH/other O containing group

Beta = -OH on anomeric carbon points same way of attaching carbon’s OH/other O containing group

What is the anomeric carbon?

The carbon that had the carbonyl group that was attacked. C1 in aldoses and C2 in ketoses.

Hexoses are commonly modified to alter their activity in a cell, common modifications include:

+ phosphate groups
+ amino groups
- hydroxyl groups
+ amino acids

What are reducing sugars?

Aldoses (or ketoses that rearrange) with a free aldehyde group/anomeric carbon.

Reducing sugars can undergo nonspecific glycation rxns w/ oxidizing reagents. What are two applications of this?

A1C measurements and blood glucose levels

Advanced glycation end (AGEs) products

Why are AGEs bad?

Causes cross linking between proteins which makes them too rigid to work

What are N vs O glycosidic linkages?

N attach at a nitrogen
O attach at an oxygen

How do you name a bond in a disaccharide?

alpha/beta C# - alpha/beta C# glycosidic bond

Alpha and beta are only required if the bond includes an alpha/beta C

How do you name a disaccharide?

[alpha/beta ] - [D/L] - [Sugar minus -ose][pyranose/furanose] - (C#→C#) - [alpha/beta ] - [D/L] - [Sugar minus -ose][pyranose/furanose]

What are homo vs heteropolysaccharides and what are they used for?

Homo is only the same sugar attached in repeating units
- Used for storage
Hetero is 2+ different sugars attached in repeating units
- Used for signaling/ECM attachment

______ is used by plants for storage of glucose, contains _______ and ______, and is commonly found in ____/_____.

Amylase
Amylopectin

roots/seeds

What is amylase?

long unbranched chains made of glucose with alpha1-4 glycosidic linkages

What is amylopectin?

Larger than amylase and branching, made of glucose, alpha1-4 linkages, and alpha1-6 linkages for attaching branches.

_______ is used by animals for storage of glucose, often found in _______.

Glycogen, muscles

What is glycogen?

Storage made of glucose with alpha1-4 linkages and alpha1-6 linked branches. (More branched than starch)

What is cellulose and what is it used for?

Linear and unbranched made of glucose, have beta1-4 linkages. Used for structure

Why can’t we break down cellulose?

It is connected by beta1-4 glycosidic linkages but we only have an enzyme to break alpha1-4 glycosidic linkages

What are glycoconjugates? What are the three types?

An information carbohydrate joined to a protein or lipid.

• Glycoproteins

• proteoglycans

• Glycolipids

What are glycoproteins?

mostly protein, some sugar. Found on cell membrane proteins and secreted proteins

What are proteoglycans?

Mostly sugar, some protein. Sugars draw water to them. Found in cartilage and synovial fluid, help cushion/lubricate.

What amino acids connect via O-linkages vs N-linkages?

O = serine/threonine
N = Asparagine

What is EPO?

A glycoprotein secreted by the kidneys to stimulate production of red blood cells.

Glycosylation of hemoglobin is measured in a clinical setting to determine whether a person has uncontrolled diabetes.  Glycosylation of a protein is a result of

a free aldehyde on the linear form of a sugar nonspecifically reacting with a free amino group on a protein.