Biology Chapter 2: Life's Molecules and Bonds

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Questions and Answers

What distinguishes prokaryotic cells from eukaryotic cells?

Prokaryotic cells contain membrane-bound organelles.

Prokaryotic cells have a nucleus.

Prokaryotic cells are larger in size than eukaryotic cells.

Prokaryotic cells have DNA in an unbounded region called the nucleoid. (correct)

Which process allows substances to diffuse across a biological membrane without energy investment?

Active transport

Passive transport (correct)

Endocytosis

Facilitated diffusion

What is a key feature of mitochondria and chloroplasts that supports the endosymbiont theory?

They grow and reproduce independently within host cells. (correct)

They do not have ribosomes.

They contain linear DNA molecules.

They have a single membrane.

What is the role of anabolic pathways in metabolism?

They combine simple molecules to form complex ones. Signup and view all the answers

Which membrane protein function is primarily involved in the transmission of signals within a cell?

Signal transduction Signup and view all the answers

What is the main characteristic of catabolic pathways in metabolism?

They release energy by breaking down complex molecules. Signup and view all the answers

What is the primary difference between passive transport and active transport?

Active transport can occur against a concentration gradient. Signup and view all the answers

What is the role of the nucleus in a eukaryotic cell?

It contains the majority of the cell's DNA. Signup and view all the answers

Which type of bond is formed between two oppositely charged ions?

Ionic bond Signup and view all the answers

What occurs during a dehydration reaction?

Two monomers bond with the release of water Signup and view all the answers

What is the primary role of ATP in the cell?

To store energy for cellular processes Signup and view all the answers

What is a characteristic of saturated fats?

They are solid at room temperature Signup and view all the answers

The structure of DNA is characterized by what type of sugar?

Deoxyribose Signup and view all the answers

What type of protein structure is stabilized by interactions between side chains?

Tertiary structure Signup and view all the answers

Which of the following accurately describes the pH scale?

Each increase of 1 represents a 10x increase Signup and view all the answers

What results from the hydrolysis of a polymer?

Breaking down into monomers Signup and view all the answers

Which structure is formed from the association of two or more polypeptides?

Quaternary structure Signup and view all the answers

What functional role do carbohydrates primarily serve in organisms?

Fuel and building material Signup and view all the answers

What does the law of independent assortment state?

Each pair of alleles segregates independently during gamete formation. Signup and view all the answers

What is a Barr body?

An inactivated X chromosome in female mammals. Signup and view all the answers

Which of the following best describes a sex-linked gene?

A gene located on either the X or Y chromosome. Signup and view all the answers

How does apoptosis protect neighboring cells?

By fragmenting DNA and cytoplasmic components. Signup and view all the answers

Which of the following statements about viral properties is accurate?

Viruses are obligate intracellular parasites. Signup and view all the answers

What is the role of myoD in muscle cell differentiation?

It is a transcription factor that commits cells to becoming skeletal muscle. Signup and view all the answers

What is a characteristic of dsRNA viruses?

They contain double-stranded RNA in their genome. Signup and view all the answers

What occurs during the assembly phase of the viral replicative cycle?

Viral proteins and nucleic acid molecules spontaneously self-assemble into new viruses. Signup and view all the answers

What can result from nondisjunction during meiosis?

A gamete with an abnormal number of chromosomes. Signup and view all the answers

What is the primary function of a virus's envelope?

To facilitate attachment to host cells. Signup and view all the answers

What does the second law of thermodynamics state about energy transfers?

Every energy transfer increases the entropy of the universe. Signup and view all the answers

Which of the following statements accurately describes exergonic reactions?

They release energy and are spontaneous. Signup and view all the answers

What role does NAD+ play during cellular respiration?

Functions as an oxidative agent accepting electrons. Signup and view all the answers

Which process accounts for the majority of ATP generated during cellular respiration?

Oxidative phosphorylation. Signup and view all the answers

In glycolysis, how many ATP molecules are used in the energy investment phase?

Two ATP molecules are used. Signup and view all the answers

What is the primary role of histones in DNA structure?

To package DNA into structures called nucleosomes. Signup and view all the answers

What is a characteristic of competitive enzyme inhibitors?

They bind to the active site of an enzyme hindering substrate binding. Signup and view all the answers

What is the process of converting CO2 into organic molecules during the Calvin cycle called?

Carbon fixation. Signup and view all the answers

What is the function of DNA ligase during recombinant DNA technology?

It closes the sugar-phosphate backbone of DNA strands. Signup and view all the answers

Which statement accurately describes transcription?

Transcription progresses at a rate of 40 nucleotides per second in eukaryotes. Signup and view all the answers

What is the outcome of oxidative phosphorylation in cellular respiration?

It synthesizes ATP by transferring inorganic phosphate to ADP. Signup and view all the answers

During DNA replication, what are the replication bubbles formed?

Regions where DNA strands are unwound. Signup and view all the answers

In the light reactions of photosynthesis, what is released as a waste product?

Oxygen. Signup and view all the answers

What type of enzyme inhibitors form covalent bonds with the enzyme?

Irreversible inhibitors. Signup and view all the answers

What is the primary role of transfer RNA (tRNA) in translation?

To transfer amino acids to the ribosome Signup and view all the answers

Which type of mutation is likely to create a nonfunctional protein?

Nonsense mutation Signup and view all the answers

What is one of the main functions of the operator in an operon?

To bind repressor proteins Signup and view all the answers

How does differential gene expression contribute to cellular diversity?

By expressing different genes in different cell types Signup and view all the answers

During which stage of the cell cycle do chromosomes duplicate?

S phase Signup and view all the answers

What is the primary mechanism of regulation in the cell cycle checkpoints?

Internal and external signals Signup and view all the answers

Why are homologous chromosomes relevant during meiosis?

They align and separate to reduce chromosome number. Signup and view all the answers

Which of the following statements about eukaryotic genes is true?

They often have multiple control elements for regulation. Signup and view all the answers

What distinguishes heterozygous organisms from homozygous ones?

Heterozygous organisms have two different alleles for a gene. Signup and view all the answers

What is the difference between mitosis and meiosis regarding genetic outcome?

Meiosis leads to genetically distinct cells. Signup and view all the answers

Which of the following best describes the plasma membrane's role during binary fission?

It pinches inward to divide the cell into two. Signup and view all the answers

What is the main role of transcription factors in eukaryotic gene expression?

To assist in the assembly of the transcription complex Signup and view all the answers

In the context of the cell cycle, what happens during the M phase?

The cell undergoes division. Signup and view all the answers

Study Notes

Organization of Life Molecules

Life's organization progresses from molecules to genetic material to macromolecules to cells.

Elements and Atoms

Elements and atoms are fundamental components of all matter, including living organisms.

Chemical Bonds

Covalent Bonds: Atoms share electrons, indicated by lines. A single bond shares one pair, and a double bond shares two pairs. Bonding capacity reflects the number of electrons needed to complete an atom's valence shell.
Ionic Bonds: Formed between oppositely charged ions.
Hydrogen Bonds: Weak bonds between slightly positive hydrogen atoms and slightly negative atoms in other molecules, crucial for water's properties.

pH Scale

Measures acidity or basicity, ranging from 0 to 14. Each unit represents a tenfold difference.

Organic Molecules

Hydrocarbons: Organic molecules composed solely of carbon and hydrogen.
Macromolecules: Large molecules crucial for life's processes. They include carbohydrates, fats, proteins, and nucleic acids.
ATP: Adenosine triphosphate is a vital energy source in cells. It stores potential energy released during hydrolysis.

Polymer Synthesis and Breakdown

Dehydration Reactions: Monomers link together, losing a water molecule.
Hydrolysis: Polymers break down into monomers through water addition. Enzymes facilitate both reactions.

Carbohydrates

Sugary molecules, including monosaccharides (simple sugars), serving as fuel and building material.

Fats (Lipids)

Saturated Fats: Solid at room temperature, primarily from animal sources.
Unsaturated Fats (Oils): Liquid at room temperature, abundant in plants and fish.

Proteins

Crucial for various life processes including: defense, storage, transport, communication, movement, support.
Protein Structure Levels:
- Primary Structure: Linear chain of amino acids.
- Secondary Structure: Regions stabilized by hydrogen bonds (alpha-helices, beta-sheets).
- Tertiary Structure: Three-dimensional shape stabilized by interactions between amino acid side chains.
- Quaternary Structure: Association of multiple polypeptides.

Nucleic Acids

Store, transmit, express hereditary information.
DNA: Deoxyribonucleic acid, the genetic material composed of nucleotide monomers.
RNA: Ribonucleic acid, involved in protein synthesis.
Nucleotide Components: Sugar (deoxyribose in DNA, ribose in RNA), phosphate group, nitrogenous base (adenine, guanine, cytosine, thymine in DNA; uracil in RNA).

Cells: Prokaryotic vs. Eukaryotic

Prokaryotic: Simple cells without a nucleus or membrane-bound organelles. DNA is in the nucleoid region.
Eukaryotic: Complex cells with a nucleus and membrane-bound organelles. DNA is stored in the nucleus.

Organelles and Their Functions

Organelles are membrane-bound compartments performing specific functions. Their specific function is outlined in chapter 5.

Membrane Transport

Passive Transport (Diffusion): Substances move down their concentration gradient (high to low) without energy input.
Membrane Proteins: Facilitate transport, enzymatic activity, signal transduction, cell-cell recognition, and other functions.

Metabolic Pathways

Catabolic: Break down complex molecules, releasing energy. Examples include cellular respiration.
Anabolic: Build complex molecules, consuming energy. Examples include protein synthesis.

The Second Law of Thermodynamics

Increases entropy (disorder) in the universe during energy transfers.

Free Energy and Metabolism

Free energy (ΔG) determines the spontaneity of a reaction. Exergonic reactions release free energy, while endergonic reactions require it.

Enzyme Inhibitors

Competitive Inhibitors: Block the active site.
Non-competitive Inhibitors: Bind to a different site altering the active site.

Cellular Respiration

Glycolysis: Breakdown of glucose into pyruvate.
Citric Acid Cycle (Krebs Cycle): Further oxidation of organic molecules.
Electron Transport Chain (Oxidative Phosphorylation): Generates ATP using an electron transport chain.
Fermentation: Alternative pathway for ATP production in the absence of oxygen.

Photosynthesis

Light Reactions: Convert solar energy into chemical energy (ATP, NADPH). Water is split, releasing oxygen.
Calvin Cycle: Uses ATP and NADPH to synthesize sugar from carbon dioxide.

DNA Replication

Replication begins at origins of replication, forming replication bubbles.
DNA replication complex unwinds DNA, enabling DNA polymerase to replicate DNA strands to ensure identical genetic material.
DNA packing is regulated by proteins called histones. Nucleosomes are formed by DNA wrapped around protein cores of histones.

Recombinant DNA Technology

Restriction enzymes cut DNA at specific sites. Sticky ends facilitate bonding. DNA ligase joins DNA fragments.

Transcription

DNA sequence is transcribed into RNA.

Translation

RNA sequence is translated into a protein sequence.

Mutations

Nucleotide-Pair Substitutions: Replace one nucleotide pair with another.
Silent Mutations: Do not change the amino acid.
Missense Mutations: Change one amino acid to another.
Nonsense Mutations: Change an amino acid codon to a stop codon.

Gene Regulation

Operons: Clusters of genes with coordinated regulation. Repressors bind to operators.
Eukaryotic Regulation: Complex control elements and transcription factors regulate gene expression.

Cell Signaling

Three stages: reception, transduction, response.

Cell Cycle

M Phase: Mitosis and cytokinesis.
Interphase: Cell growth and chromosome replication.
Phases of Interphase: G1, S, G2.
Binary Fission: Prokaryotic cell division.

Cell Cycle Checkpoints

Control the cell cycle progression, ensuring accuracy.

Meiosis

Cell division reducing the chromosome number by half, generating genetically diverse gametes.

Genetics

Homozygous: Two identical alleles for a trait.
Heterozygous: Two different alleles.
Phenotype: Observable characteristics.
Genotype: Genetic makeup.
Independent Assortment: Alleles of different genes segregate independently.
Sex-linked Genes: Located on sex chromosomes.
X-inactivation: One X chromosome inactivated in females.
Nondisjunction: Errors in chromosome segregation during meiosis.

Viral Properties

Viruses are obligate intracellular parasites.
Viral genomics can be either ssRNA, dsRNA, ssDNA or dsDNA.
Viruses require host cells to replicate

Apoptosis

Programmed cell death.

Cellular Differentiation

Specialization of cell types via gene expression.

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Description

Explore the organization of life from molecules to cells in this biology quiz. Understand the fundamental components of matter, the types of chemical bonds, and the significance of the pH scale. This quiz covers essential concepts related to organic molecules and macromolecules critical for living organisms.