Biology Chapter 2: Chemical Basis of Life

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Questions and Answers

What distinguishes atoms of different elements?

The number of protons (correct)

The mass number

The electron cloud size

The number of neutrons

Which of the following accurately describes a compound?

A mixture of two or more elements

A substance that cannot be broken down chemically

A substance that consists of a single element

A substance consisting of two or more different elements combined in a fixed ratio (correct)

Which of the following accurately describes an element?

A mixture of two or more compounds.

A chemical substance made of two different atoms.

A fundamental substance that cannot be broken down by ordinary chemical means. (correct)

A substance that can be broken down into simpler substances.

Which subatomic particle has a positive charge?

Proton Signup and view all the answers

Which elements make up approximately 99% of the human body?

Oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Signup and view all the answers

Which of the following compounds is formed from hydrogen and oxygen?

Water (H2O) Signup and view all the answers

How do isotopes of an element differ from one another?

By the number of neutrons Signup and view all the answers

What is the charge of an atom if it has an equal number of protons and electrons?

Neutral Signup and view all the answers

What percentage of human body weight is comprised of trace elements?

Less than 0.1% Signup and view all the answers

Which statement correctly describes emergent properties in compounds?

Compounds exhibit characteristics that differ from those of their constituent elements. Signup and view all the answers

What is typically true about the masses of protons and neutrons?

Protons and neutrons have nearly identical masses Signup and view all the answers

What role does iron play in the human body?

It is essential for energy processing and oxygen transport in the blood. Signup and view all the answers

What defines a chemical substance?

A substance with a distinct molecular composition produced by or used in a chemical process Signup and view all the answers

Which of the following elements is considered a trace element essential for vertebrates?

Iodine Signup and view all the answers

What primarily determines an atom's chemical properties?

The number of electrons in the outermost shell Signup and view all the answers

What type of bond is formed when two atoms share electrons?

Covalent bond Signup and view all the answers

Which of the following elements is likely to form polar covalent bonds?

Oxygen Signup and view all the answers

An ionic bond is created when:

One atom completely transfers an electron to another Signup and view all the answers

Which of the following pairs are likely to form a nonpolar covalent bond?

Two hydrogen atoms Signup and view all the answers

What does the term 'valence' refer to in the context of atoms?

The number of electrons needed to fill the outer shell Signup and view all the answers

Which statement is true regarding inert elements?

They have full outer shells Signup and view all the answers

What occurs when two atoms with different electronegativities form a bond?

One atom becomes negatively charged Signup and view all the answers

Why are most drugs manufactured as salts?

They have better stability when dry and dissolve easily in water. Signup and view all the answers

What type of bond primarily links atoms to form a cell's molecules?

Covalent bonds Signup and view all the answers

Which statement about hydrogen bonds is true?

They involve a hydrogen atom attracted to a more electronegative atom. Signup and view all the answers

What does it mean for a molecule to be polar?

It has an uneven distribution of charges, resulting in partial positive and negative regions. Signup and view all the answers

How many hydrogen bonds can each water molecule potentially form?

Four Signup and view all the answers

In which biological processes are hydrogen bonds crucial?

Creating a protein's shape and holding DNA strands together Signup and view all the answers

What is one characteristic of water that results from its polarity?

It has a high boiling point and surface tension. Signup and view all the answers

Which of the following can be described as a polar molecule?

Water Signup and view all the answers

What is the term that describes the tendency of water molecules to stick together?

Cohesion Signup and view all the answers

How do hydrogen bonds affect the temperature of water compared to other substances?

Water has a stronger resistance to temperature change. Signup and view all the answers

What effect does cohesion have in trees?

It helps distribute nutrients from roots to leaves. Signup and view all the answers

What does surface tension measure?

The resistance to breaking the surface of a liquid Signup and view all the answers

What role does adhesion play in water's movement in plants?

Enhances the adhesion of water to cell walls. Signup and view all the answers

What happens to thermal energy when it transfers from a warmer body to a cooler body?

It is defined as heat. Signup and view all the answers

What must occur for the temperature of water to increase?

Hydrogen bonds must be broken. Signup and view all the answers

How is surface tension demonstrated when water is slightly overfilled in a glass?

Water forms a dome above the rim. Signup and view all the answers

What is the term for the substance that is dissolved in a solution?

Solute Signup and view all the answers

Which property of water allows it to dissolve ionic compounds effectively?

Polarity Signup and view all the answers

What happens to the concentration of H+ ions when an acid is added to an aqueous solution?

It increases Signup and view all the answers

Which substance is an example of a strong acid?

Hydrochloric acid Signup and view all the answers

What is the outcome when sodium hydroxide is added to an aqueous solution?

It decreases H+ concentration Signup and view all the answers

How does the pH of a solution relate to its hydrogen ion concentration?

Each pH unit represents a change in H+ by a factor of 10 Signup and view all the answers

What is the pH of pure water?

7 Signup and view all the answers

Which of the following substances increases the concentration of hydroxide ions when dissolved in water?

Sodium hydroxide Signup and view all the answers

What type of isomers differ in the arrangement of atoms around a double bond?

Geometric isomers Signup and view all the answers

What defines hydrocarbons?

Molecules consisting of only carbon and hydrogen Signup and view all the answers

Which chemical group is described as having a hydrogen atom bonded to an oxygen atom?

Hydroxyl group Signup and view all the answers

Which of the following statements is true about enantiomers?

They are mirror images of each other Signup and view all the answers

What impact do small differences in atomic groups have on hormones like testosterone and estradiol?

They affect the molecules' functions Signup and view all the answers

Which functional group is typically associated with alcohols?

Hydroxyl group Signup and view all the answers

In what way can a carbonyl group be positioned in a carbon skeleton?

Both at the end and within the skeleton Signup and view all the answers

What characteristic of carbon allows it to form a wide variety of complex organic molecules?

Having four valence electrons that can form four covalent bonds Signup and view all the answers

How do isomers differ from one another?

They have the same molecular formula but different structural arrangements. Signup and view all the answers

What geometric arrangement occurs when carbon forms four single bonds?

Tetrahedral Signup and view all the answers

Which of the following is NOT a way carbon skeletons can vary?

Type of bonding with oxygen Signup and view all the answers

What are the molecular formulas of butane and isobutane, which represent structural isomers?

C₄H₁₀ Signup and view all the answers

What role does cellulose play in human nutrition?

It contributes to digestive health as insoluble fiber. Signup and view all the answers

Which statement accurately describes lipids?

They are hydrophobic and do not mix well with water. Signup and view all the answers

What is formed when three fatty acids link to a glycerol molecule?

A triglyceride. Signup and view all the answers

What characteristics do unsaturated fatty acids have?

They contain one or more double bonds in their hydrocarbon chains. Signup and view all the answers

What is the main function of cellulose in ecosystems?

It aids decomposition and recycling of chemical elements. Signup and view all the answers

What do cows and termites have in common concerning cellulose digestion?

They host microorganisms that can digest cellulose. Signup and view all the answers

What are lipids primarily composed of?

Glycerol and fatty acids. Signup and view all the answers

What is a characteristic of saturated fatty acids?

They have the maximum number of hydrogen atoms. Signup and view all the answers

Why are unsaturated fats generally liquid at room temperature?

They have kinks in their fatty acid tails. Signup and view all the answers

What indicates that unsaturated fats have been converted to saturated fats in a product?

Partially hydrogenated oils Signup and view all the answers

What is the primary function of fats in the body?

Energy storage Signup and view all the answers

What is a triglyceride composed of?

One glycerol and three fatty acids Signup and view all the answers

What role do phospholipids play in cells?

Cell membrane structure Signup and view all the answers

How do the two ends of a phospholipid differ in their relation to water?

The tails are hydrophobic and the heads are hydrophilic. Signup and view all the answers

What is an effect of having a reasonable amount of body fat?

It provides insulation and cushions vital organs. Signup and view all the answers

What is a characteristic of fibrous proteins?

They are typically long and thin. Signup and view all the answers

How does lysozyme function in bacterial destruction?

It binds to surface molecules of bacteria. Signup and view all the answers

What is one consequence of protein denaturation?

It results in the loss of the protein's function. Signup and view all the answers

What role do R groups play in amino acids?

They influence the amino acid's hydrophobicity or hydrophilicity. Signup and view all the answers

What can misfolded proteins lead to in the body?

Accumulation of diseases such as Alzheimer's. Signup and view all the answers

What happens to proteins during the cooking process, such as frying an egg?

They denature and become solid. Signup and view all the answers

What is the significance of a protein's three-dimensional shape?

It allows the protein to function properly. Signup and view all the answers

What are prions known for?

They are infectious proteins that cause diseases. Signup and view all the answers

What differentiates DNA from RNA in terms of nucleotide composition?

DNA contains deoxyribose while RNA contains ribose. Signup and view all the answers

What role do nitrogenous bases serve in the structure of DNA?

They pair to hold the double helix structure. Signup and view all the answers

What is the function of RNA in relation to DNA?

RNA helps assemble polypeptides based on DNA instructions. Signup and view all the answers

How is a polynucleotide formed from nucleotides?

Through dehydration reactions creating a sugar-phosphate backbone. Signup and view all the answers

During DNA replication, what happens to chromosomes?

Two identical copies of each chromosome are made. Signup and view all the answers

Which base pairs are found in DNA and how do they pair?

Adenine pairs with Thymine and Cytosine pairs with Guanine. Signup and view all the answers

What is a defining characteristic of RNA compared to DNA?

RNA typically exists as a single polynucleotide strand. Signup and view all the answers

What are the building blocks of nucleic acids?

Monomers called nucleotides. Signup and view all the answers

Study Notes

Chapter 2: Chemical Basis of Life

Matter occupies space and has mass, existing in solid, liquid, and gas states
Elements are substances that cannot be broken down chemically. There are 92 naturally occurring elements, and others have been created synthetically. Each element has a unique symbol (e.g., O for oxygen, Na for sodium) derived from its name (English, Latin, or German).
Compounds are substances made of two or more elements combined in a fixed ratio. Their properties differ from the individual elements combining them
Essential elements for life (humans): 25 elements for humans, 17 for plants. About 99% of human body composed of oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. The other 1% includes potassium, sulfur, sodium, chlorine, and magnesium
Trace elements: Boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, and zinc, make up less than 0.01% of body weight.
Matter's states: Solid, liquid, and gas
Atoms: The smallest unit of matter, retaining the substance's properties, composed of protons (positive charge), neutrons (neutral charge), and electrons (negative charge)
Atomic number: Equals the number of protons in an atom
Mass number: Sum of protons and neutrons in an atom
Isotopes: Atoms of the same element with varying neutron numbers (e.g., carbon-12, carbon-13, carbon-14)
Electron Shells: Electrons orbit the nucleus in shells. Valence shells (outer electron shells) influence atomic reactivity.
Covalent bonds: Atoms share electrons to complete their outer electron shells. Polar covalent bonds form when atoms with differing electronegativity share electrons unequally. Nonpolar covalent bonds form when atoms have similar electronegativity and share electrons equally.
Ionic bonds: One atom transfers an electron to another atom to achieve a complete outer shell, resulting in electrostatic attraction between opposite charges
Hydrogen bonds: Weak attractions between a hydrogen atom on one molecule and a slightly electronegative atom on another molecule (often oxygen or nitrogen)
Molecules: Two or more atoms held together by covalent bonds
Chemical reactions: Rearrange matter by breaking and forming chemical bonds (reactions involved in life processes)
Reactants: Molecules that participate in a reaction
Products: Resulting molecules from the reaction
Cohesion: The tendency for like molecules to stick together
Adhesion: The tendency for molecules of different substances to stick together
Water as a solvent: Water's polarity allows it to dissolve many substances forming a solution (dissolved substance [solute] within a solvent). This property is crucial for life.
Surface tension: Water's hydrogen bonds cause high surface tension, making water behave as if coated with an invisible film
Hydrogen bonds moderate temperature: Water's hydrogen bonds absorb heat without large temperature changes, regulating temperature for living organisms.
Water density: Ice is less dense than liquid water, so it floats, allowing aquatic life to survive in freezing temperatures.
Acids and bases: Acids release hydrogen ions (H+); bases absorb hydrogen ions. pH is a measure of hydrogen ion concentration (0−14).
pH: Measure of the acidity or basicity of a solution.
Solution: A mixture consisting of a uniform distribution of two or more substances

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Explore the fundamental concepts of matter, elements, and compounds in this quiz based on Chapter 2 of Biology. Learn about essential elements for life and trace elements crucial for organisms. Test your knowledge on the chemical foundations that support life on Earth.