Mastering Biology Practice Questions #3

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Questions and Answers

What do pH buffers consist of?

Weak acids and bases

How does this system buffer a solution against decreases in pH?

A- reacts with H+ to become HA

Buffers work best when?

about half of the buffer molecules are dissociated

How does the way a buffer stabilizes pH during the addition of acid differ from the way the same buffer stabilizes pH during addition of bases?

it's the same reaction running backward or forward Signup and view all the answers

Which answer helps to explain why all living cells need pH buffers?

Amino acid side chains have many carboxyl and amino groups. Signup and view all the answers

To make a buffer, you need to?

have a weak acid or a weak base half ionized in water Signup and view all the answers

What is true about the ionization of water?

Water ionizes to form hydroxide and hydronium ions; dissociation of water produces equal numbers of OH- and H+; dissociation of water is reversible. Signup and view all the answers

L-Dopa is used to treat?

Parkinson's disease Signup and view all the answers

What kind of effect does R-Dopa have on Parkinson's disease?

none Signup and view all the answers

Which molecules differ in the covalent bond relationships among their atoms?

Structural isomers Signup and view all the answers

Which molecules differ in how their atoms are arranged about a double bond?

Geometric isomers Signup and view all the answers

Which molecules are mirror images of each other?

Enantiomers Signup and view all the answers

Which functional group is a characteristic of alcohol?

Hydroxyl group Signup and view all the answers

Which functional group behaves as a base?

Amino group Signup and view all the answers

Which functional group is a characteristic of thiols?

Sulfhydryl group Signup and view all the answers

Which functional group plays a major role in energy transfer?

Phosphate group Signup and view all the answers

Which functional group is a characteristic of a ketone?

Carbonyl group Signup and view all the answers

Which functional group behaves as an acid?

Carboxyl groups Signup and view all the answers

Why are hydrocarbons insoluble in water?

The majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages. Signup and view all the answers

What is the chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule?

Dehydration synthesis Signup and view all the answers

What is the chemical process that lyses, or splits, molecules by the addition of water?

Hydrolysis Signup and view all the answers

Which of these classes of biological molecules does NOT include polymers?

lipids Signup and view all the answers

Sucrose is formed when a glucose is joined to fructose by a?

glycosidic linkage Signup and view all the answers

What is the major structural difference between starch and glycogen?

The amount of branching that occurs in the molecule. Signup and view all the answers

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

as a component of animal cell membranes Signup and view all the answers

The characteristic that all lipids have in common is that?

none of them dissolve in water. Signup and view all the answers

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 Signup and view all the answers

Study Notes

Buffer Systems

Buffers consist of weak acids and their conjugate bases, helping to maintain a stable pH in biological systems.
A buffer includes undissociated acid (HA) and its dissociated form (A-); when H+ is added, A- reacts to form HA, mitigating pH changes.
Optimal buffer function occurs when approximately half of the buffer molecules are in the dissociated state.
Buffers stabilize pH against acid addition by reacting with H+ and against base addition by producing H+ from HA.

Biological Importance of Buffers

All living cells require pH buffers due to the many carboxyl and amino groups present in amino acid side chains.

Water Ionization

Water ionizes into hydroxide (OH-) and hydronium (H3O+) ions, maintaining a reversible equilibrium.

Pharmacology

L-Dopa is a treatment for Parkinson's disease, while R-dopa has no therapeutic effect on the condition.

Isomer Types

Structural isomers differ in the covalent bond arrangements of their atoms, while geometric isomers differ in atom arrangement around a double bond.
Enantiomers are molecules that are mirror images of each other.

Functional Groups and Their Properties

Alcohols are characterized by the hydroxyl group.
Amino groups act as bases.
Thiols are defined by the presence of a sulfhydryl group.
The phosphate group is crucial in energy transfer.
Ketones feature a carbonyl group.
Carboxyl groups behave as acids.

Hydrocarbon Characteristics

Hydrocarbons are insoluble in water due to their predominantly nonpolar covalent carbon-to-hydrogen bonds.

Chemical Reactions

Dehydration synthesis involves the covalent bonding of two molecules with the removal of a water molecule.
Hydrolysis is the process of splitting molecules by adding water.

Biological Macromolecules

Lipids are unique among biological macromolecules, as they do not form polymers.
Sucrose is formed by a glycosidic linkage joining glucose and fructose.
Starch and glycogen differ structurally mainly in their branching patterns.

Cholesterol and Lipids

Cholesterol serves as a beneficial component of animal cell membranes.
A defining property of lipids is their inability to dissolve in water.
Vegetable oils are liquids at room temperature due to a higher number of double bonds compared to animal fats, which are more saturated.

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Description

Test your knowledge on the concepts of pH buffers with these practice questions. This quiz includes flashcards covering buffer composition and functionality. Perfect for students preparing for biology exams or reviewing key concepts.