Biology Chapter: Properties of Water and Buffers

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Questions and Answers

Which property of water is primarily responsible for its role as a lubricant in biological systems?

Hydrogen bonding (correct)

Heat capacity

Cohesion

Density

How do buffers function in biological systems?

By promoting the dissociation of water

By stabilizing the pH of solutions (correct)

By directly reacting with hydroxide ions only

By increasing the concentration of hydrogen ions

What happens to salts like NaCl when they dissolve in water?

They remain intact and do not dissociate

They release hydroxide ions

They form hydrogen bonds with water

They dissociate into their constituent ions (correct)

What effect does a high concentration of hydrogen ions (H+) in a solution have?

It disrupts cell and tissue functions Signup and view all the answers

Which characteristic of water contributes most to its role in biological chemical reactions?

Polarity and ability to form hydrogen bonds Signup and view all the answers

What role do enzymes play in chemical reactions?

They act as catalysts to speed up the reactions. Signup and view all the answers

What is the primary purpose of activation energy in a chemical reaction?

To initiate the reaction by overcoming energy barriers. Signup and view all the answers

Which property of water contributes to its ability to moderate temperature changes?

High specific heat capacity Signup and view all the answers

What distinguishes monosaccharides from polysaccharides?

Monosaccharides are single sugar molecules, while polysaccharides are chains of sugar units. Signup and view all the answers

Which of the following is NOT considered a biological macromolecule?

Water Signup and view all the answers

What is the primary function of enzymes in biochemical reactions?

They lower the activation energy of a reaction. Signup and view all the answers

Which statement best describes the 'lock and key' model of enzyme specificity?

Only substrates with a specific shape and charge can bind to the enzyme. Signup and view all the answers

What is a defining characteristic of carbohydrates?

They can be classified as monosaccharides, disaccharides, and polysaccharides. Signup and view all the answers

Which of the following best describes the relationship between monomers and polymers?

Polymers are formed when monomers join through dehydration synthesis. Signup and view all the answers

What type of macromolecule primarily functions as an energy source in the body?

Carbohydrates Signup and view all the answers

What is the role of activation energy in a chemical reaction?

It is the energy required for reactants to convert into products. Signup and view all the answers

Which component is commonly found in lipids but not in carbohydrates?

Phosphorus Signup and view all the answers

Why are enzymes sensitive to environmental conditions?

They only function in a narrow temperature range. Signup and view all the answers

Which of the following is NOT a classification of nucleic acids?

Proteins Signup and view all the answers

What determines the unique properties of proteins?

The three-dimensional shape of the protein. Signup and view all the answers

Study Notes

Chemical Level of Organization

The chemical level includes atoms, subatomic particles, bonding, states of matter, reactions, enzymes, water, pH, and biological macromolecules.
Atoms are the smallest stable units of matter and are composed of subatomic particles (protons, neutrons, electrons).

Levels of Organization

Levels of organization include the organism level, organ system level, organ level, tissue level, cellular level, and the chemical level.
The chemical level is the foundation. Atoms combine to form molecules and compounds, which then form larger structures.

Matter

Matter is anything that takes up space and has mass.
Mass is the quantity of matter in an object.
On Earth, mass is equivalent to weight (because gravity is 1). On a planet with different gravity the weight would be different.

Atoms

Atoms are the basic building blocks of matter.
They are composed of protons, neutrons, and electrons.
Protons have a positive charge. Neutrons are neutral (no charge). Electrons have a negative charge.
Atoms have a nucleus containing protons and neutrons, surrounded by electrons in electron shells.
The periodic table lists all known elements. There are hypothesized elements beyond the ones listed.
There is a total of 118 known elements.

Atomic Structure and Properties

Atomic symbol: One or two letter code for an element (e.g., C for carbon).
Atomic number: Total number of protons in an atom.
Mass number: Total number of protons and neutrons in an atom.
Atomic weight (atomic mass): Average mass number for all forms of an atom found on earth

Atoms - Practice

Given examples of elements, students should be able to identify protons, neutrons, electrons.

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons.
They have the same atomic number but different mass numbers.

Ions

Ions are atoms that have gained or lost electrons.
Gaining electrons creates a negative ion (anion).
Losing electrons creates a positive ion (cation).

Alchemy

Medieval chemistry, focused on transforming metals into gold and finding an elixir of life (fountain of youth).

Bonding

Atoms interact through bonding to form molecules and compounds.
Types of chemical bonds include ionic, covalent, and hydrogen bonds.

Electrons and Bonding

Electrons occupy energy levels (shells) around the nucleus.
Each shell can hold a maximum number of electrons.
Valence electrons are in the outermost shell. Valence electrons determine an atom's chemical behavior and whether or not a bond will occur.

Atoms – Bonds - Octet Rule

Atoms are most stable when their valence shell is full (8 electrons, except for first shell).
Atoms bond to acquire 8 valence electrons (or 2 if in the first shell).
This is called the octet rule.

Atoms – Ionic Bonds

Transfer of electrons forms ionic bonds.
One atom loses electrons to become a positive ion (cation).
The other atom gains electrons to become a negative ion (anion).
Opposites attract, which creates an ionic bond.
Ionic compounds are salts. Example: sodium chloride (NaCl).

Atoms – Covalent Bonds

Atoms share electrons to form covalent bonds.
Single bonds share one pair of electrons.
Double bonds share two pairs of electrons.
Triple bonds share three pairs of electrons.

Atoms – Covalent Bonds - Properties

Nonpolar covalent bonds share electrons equally.
Polar covalent bonds share electrons unequally.

Atoms – Hydrogen Bonds

Attractive force between a partially positive hydrogen atom of one molecule and a partially negative atom (O or N) of another molecule.
Results from unequal electron sharing in polar molecule.
Hydrogen bonds are relatively weak individually but significant when many occur.

Molecules and Compounds

Molecules: Two or more atoms held together by covalent bonds.
Compounds: Two or more different elements in a fixed proportion, regardless of bond type.

States of Matter

Solids: Atoms are tightly packed with regular arrangement.
Liquids: Atoms are close but not arranged in a rigid structure and take the shape of their container.
Gases: Atoms are widely separated and take the shape and volume of their container.

Chemical Reactions

Chemical reactions involve atoms, molecules, or compounds interacting.
The reactions in a cell are essential for functions like providing energy, maintaining cell structure, and growth.

Chemical Reactions – Diagrams

Reactants are the starting materials in a chemical reaction.
Products are the result of a chemical reaction.
Reactants are usually listed on the left side of an equation and products on the right.

Chemical Reactions- Metabolism

Metabolism: Collective term for all the chemical reactions within a cell or organism.
Anabolism: Sum of all the synthesis reactions; build molecules.
Catabolism: Sum of all the decomposition reactions; break down molecules

Chemical Reactions – Types

There are three types of chemical reactions:

Decomposition or Catabolic Reactions: Break a larger molecule into smaller molecules.
Synthesis or Anabolic Reactions: Combine smaller fragments into a larger molecule.
Exchange Reactions: Reactants are shuffled around between molecule fragments.

Chemical Reactions- Hydrolysis

Decompostion reaction involving water
A water molecule splits a chemical bond between fragments of a molecule
One fragment gains a hydrogen (H+) and the other gains a hydroxyl group (OH-).

Chemical Reactions- Dehydration Synthesis

Synthesis reaction that involves removal of water
New molecules are formed bonding fragments and releasing water as a by-product

Chemical Reactions- Free Energy Diagrams

Graph showing the amount of energy throughout a chemical reaction
Initial energy levels for reactants are shown, the activation energy, and the final energy level for products

Chemical Reactions- Exergonic

Release energy in a reaction
Reaction proceeds on its own
Common in the body

Chemical Reactions- Endergonic

Reactions that consume energy
Reactions proceed spontaneously

Chemical Reactions- Activation Energy

Minimum energy needed to start a reaction
Cells use enzymes to lower activation energy needed. This results in more efficient reactions.

Chemical Reactions- Enzymes

Enzymes are catalysts that speed up chemical reactions.
Enzymes lower the activation energy needed to begin the reaction
Enzymes are not changed or used up in a reaction.

Water (H₂O)

Water is essential for life.

Water – Properties

Water is a polar molecule that forms hydrogen bonds.
Water has high heat capacity
Water is a solvent

Water- Dependence (Acids & Bases)

pH is a logarithmic measure of hydrogen ion concentration.
pH values range from 0-14.
Substances with lower pH are acidic.
Substances with higher pH are basic (alkaline).
Normal blood pH is close to 7.4

Water- Dependence (Buffers)

Buffers stabilize the pH of a solution by removing or adding hydrogen ions.
Buffers are important in maintaining the pH of body fluids. Example: Sodium carbonate

Biological Macromolecules

Biological macromolecules are large molecules essential for life.
Four major categories: carbohydrates, lipids, proteins, and nucleic acids.

Biological Macromolecules - Carbohydrates

Contain C, H, and O in a near 1:2:1 ratio.
Simple sugars are the monomers
Complex carbohydrates are polymers of simple sugars. Example: Glycogen, starch

Biological Macromolecules - Lipids

Composed primarily of carbon and hydrogen, with little oxygen
Insoluble in water; hydrophobic
Four categories: fatty acids, glycerides, steroids, and phospholipids.

Biological Macromolecules - Proteins

Composed primarily of carbon, hydrogen, oxygen, and nitrogen.
Monomer is amino acid. There are 20 different amino acids.
Polymers are proteins.

Biological Macromolecules -Proteins- Enzymes

Enzymes are proteins that facilitate biochemical reactions by lowering the activation energy
Enzymes have a specific shape for reaction substrates (reacting molecules)
Enzymes bind to substrates at an active site.

Biological Macromolecules-Proteins- Specificity

Each enzyme is specific for its reaction and binds only to substrates with a unique shape and charge.

Biological Macromolecules – Proteins - Sensitivity

The function of enzymes are affected by changes in condition, such as changes in pH, temperature, or pressure.

Biological Macromolecules - Nucleic Acids

Nucleic acids are composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.
Two main varieties: DNA and RNA; also ATP
Contain nucleotides as monomers.
Example: ATP (adenosine triphosphate), a high energy molecule for storage and transfer.

Biological Macromolecules -Nucleic Acids- ATP

ATP is a critical molecule for energy transfer in living organisms.

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Description

Explore the essential properties of water and its role in biological systems through this quiz. Delve into the importance of water as a lubricant, the functioning of buffers, and the effects of hydrogen ions in solutions. Test your understanding of these key concepts!