Biological Hierarchy and DNA Structure
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Questions and Answers

What does the term "hierarchy" refer to in biology?

The hierarchical organization of life, starting from atoms and progressing to the biosphere.

What are the three main components that make up a nucleotide?

  • One sugar—ribose—One phosphate group—One nitrogenous base
  • One sugar—deoxyribose—Two phosphate groups—One nitrogenous base
  • One sugar—ribose—Two phosphate groups—One nitrogenous base
  • One sugar—deoxyribose—One phosphate group—One nitrogenous base (correct)

    • Which of the following are purines?

  • Uracil (U) and Guanine (G)
  • Adenine (A) and Uracil (U)
  • Cytosine (C) and Thymine (T)
  • Adenine (A) and Guanine (G) (correct)

    • What is the DNA backbone made up of?

    <p>Phosphate groups alternating with the sugar deoxyribose.</p> Signup and view all the answers

    How are nitrogenous bases in DNA united?

    <p>Hydrogen bonds.</p> Signup and view all the answers

    What is the function of genes?

    <p>Genes provide genetic instructions for the synthesis of proteins.</p> Signup and view all the answers

    What is a gene?

    <p>A segment of DNA that codes for a specific protein.</p> Signup and view all the answers

    What is chromatin?

    <p>Fine filamentous DNA material complexed with proteins.</p> Signup and view all the answers

    What are histones?

    <p>Disc-shaped clusters of eight proteins around which a DNA molecule winds.</p> Signup and view all the answers

    What does a nucleosome consist of?

    <p>A core particle made up of histones with DNA wrapped around them, and linker DNA that connects core particles.</p> Signup and view all the answers

    Each chromosome consists of two parallel filaments of identical DNA called sister chromatids.

    <p>True</p> Signup and view all the answers

    What is a base triplet?

    <p>A sequence of three DNA nucleotides that stands for one amino acid.</p> Signup and view all the answers

    Which of the following are stop codons?

    <p>UAG, UGA, and UAA</p> Signup and view all the answers

    What is the start codon?

    <p>AUG</p> Signup and view all the answers

    What is transcription?

    <p>The step from DNA to mRNA, occurring in the nucleus.</p> Signup and view all the answers

    What is RNA polymerase?

    <p>An enzyme that binds to DNA and assembles the mRNA.</p> Signup and view all the answers

    What is helicase?

    <p>An enzyme that unwinds the DNA double helix.</p> Signup and view all the answers

    Which four elements make up 96% of matter in organisms?

    <p>Carbon, oxygen, hydrogen, and nitrogen</p> Signup and view all the answers

    What are the key questions to consider when exploring how simple substances evolved into complex structures in living cells?

    <p>What are the physical structures of hydrogen, carbon, nitrogen, and oxygen atoms? What are the structures of simple molecules—water, carbon dioxide, etc.—that served as building blocks of chemical evolution?</p> Signup and view all the answers

    What is the nucleus of an atom made up of?

    <p>Protons (+) and neutrons (no charge).</p> Signup and view all the answers

    What surrounds the nucleus of an atom?

    <p>Electrons (-).</p> Signup and view all the answers

    An atom with an equal number of protons and electrons is electrically neutral.

    <p>True</p> Signup and view all the answers

    What are elements made up of?

    <p>A single type of atom.</p> Signup and view all the answers

    What is an atom's atomic number?

    <p>The number of protons in the nucleus of any atom.</p> Signup and view all the answers

    What is an atom's mass number?

    <p>The sum of protons and neutrons in the atom.</p> Signup and view all the answers

    The number of protons in an element does not vary.

    <p>True</p> Signup and view all the answers

    The number of neutrons can vary in an element.

    <p>True</p> Signup and view all the answers

    What is the atomic weight of an element?

    <p>The average of all masses of naturally occurring isotopes based on their abundance.</p> Signup and view all the answers

    What are radioactive isotopes?

    <p>Unstable isotopes that decay over time.</p> Signup and view all the answers

    Which five elements make up over 99% of atoms in the body?

    <p>Carbon, oxygen, hydrogen, nitrogen, and phosphorus</p> Signup and view all the answers

    What does each electron shell contain?

    <p>A specific number of orbitals.</p> Signup and view all the answers

    How many electrons can a single orbital hold?

    <p>Up to 2 electrons.</p> Signup and view all the answers

    How many electrons can a shell with four orbitals hold?

    <p>Up to 8 electrons.</p> Signup and view all the answers

    What is an atom's valence shell?

    <p>The outermost shell.</p> Signup and view all the answers

    What are valence electrons?

    <p>Electrons in the outermost shell.</p> Signup and view all the answers

    What does the number of unpaired valence electrons determine?

    <p>The valence of an atom.</p> Signup and view all the answers

    When are atoms most stable?

    <p>When their valence shells are full.</p> Signup and view all the answers

    When do covalent bonds form?

    <p>When unpaired valence electrons are shared by two atoms.</p> Signup and view all the answers

    What is a nonpolar covalent bond?

    <p>A covalent bond in which the electrons are shared equally by the two atoms.</p> Signup and view all the answers

    How are ionic bonds formed?

    <p>When one or more electrons are transferred from one atom to another.</p> Signup and view all the answers

    What is a cation?

    <p>A positively charged ion.</p> Signup and view all the answers

    What are compounds?

    <p>Molecules in which atoms of different elements are bonded together.</p> Signup and view all the answers

    What is electronegativity?

    <p>The pull shared electrons toward their nuclei with varying strengths.</p> Signup and view all the answers

    What determines electronegativity?

    <p>The number of protons and the distance of the valence shell from the nucleus.</p> Signup and view all the answers

    What happens to electronegativity when moving up and to the right on the periodic table?

    <p>It increases.</p> Signup and view all the answers

    What are buffers?

    <p>Substances that minimize changes in pH.</p> Signup and view all the answers

    What are acids?

    <p>Substances that release hydrogen ions (H⁺) when dissolved in water.</p> Signup and view all the answers

    What is pH?

    <p>The hydrogen ion concentration.</p> Signup and view all the answers

    What does hydrophobic mean?

    <p>Water fearing (usually nonpolar).</p> Signup and view all the answers

    What is hydrolysis?

    <p>Breaking down complex molecules by the chemical addition of water.</p> Signup and view all the answers

    Which of the following are characteristics of life?

    <p>Cells, replication, information, energy, evolution</p> Signup and view all the answers

    What is homeostasis?

    <p>The ability of an organism to maintain a stable internal environment despite changes in the external environment.</p> Signup and view all the answers

    What are the functions of microtubules?

    <p>Form the cytoskeleton (providing structure and support), form the mitotic spindle (involved in cell division), and are key components of cilia and flagella (involved in movement).</p> Signup and view all the answers

    What is a mitochondrion?

    <p>A eukaryotic organelle that is surrounded by two membranes and is the site of aerobic respiration and ATP synthesis.</p> Signup and view all the answers

    What is the nucleus?

    <p>The control center of the cell, containing the cell's DNA.</p> Signup and view all the answers

    What is the cell membrane?

    <p>A membrane that surrounds a cell, separating it from the external environment and selectively regulating passage of molecules and ions into and out of the cell.</p> Signup and view all the answers

    What is the cell wall?

    <p>A fibrous layer found outside the plasma membrane of most bacteria and archaea and many eukaryotes.</p> Signup and view all the answers

    What are the key differences between eukaryotic and prokaryotic cells?

    <p>Eukaryotic cells have membrane-bound organelles, while prokaryotic cells do not. Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus. Eukaryotic cells divide through mitosis and meiosis, while prokaryotic cells reproduce through binary fission. Eukaryotic cells are generally larger than prokaryotic cells.</p> Signup and view all the answers

    What is active transport?

    <p>The movement of substances across cell membranes against their concentration gradient, requiring energy in the form of ATP.</p> Signup and view all the answers

    What is facilitated transport?

    <p>The movement of specific molecules down a concentration gradient using proteins.</p> Signup and view all the answers

    What is diffusion?

    <p>The movement of molecules from an area of higher concentration to an area of lower concentration.</p> Signup and view all the answers

    What is facilitated diffusion?

    <p>The movement of specific molecules across cell membranes through protein channels.</p> Signup and view all the answers

    What is osmosis?

    <p>The diffusion of water across a selectively permeable membrane.</p> Signup and view all the answers

    What are transport proteins?

    <p>Proteins that allow particular molecules to enter and exit cells or carry them throughout the body.</p> Signup and view all the answers

    What are receptor proteins?

    <p>Proteins that bind to specific signal molecules, enabling the cell to respond to the signal molecule.</p> Signup and view all the answers

    Describe the structure of amino acids.

    <p>Amino acids consist of a central carbon atom bonded to a hydrogen atom (H), an amino functional group (NH₂), a carboxyl functional group (COOH), and a variable &quot;side chain&quot; or R group.</p> Signup and view all the answers

    What is a glycoprotein?

    <p>A protein attached to a carbohydrate, involved in cell-to-cell recognition.</p> Signup and view all the answers

    What does PMAT stand for?

    <p>Prophase, metaphase, anaphase, telophase, the four stages of mitosis.</p> Signup and view all the answers

    What are bacteria and archaea?

    <p>Most are unicellular, all are prokaryotic, and lack membrane-bound nuclei.</p> Signup and view all the answers

    Prokaryotes that live on your body are part of your human...

    <p>microbiome.</p> Signup and view all the answers

    What is a microbiome?

    <p>A community of microbes that naturally inhabit a particular area, encompassing all the genetic material contained within it.</p> Signup and view all the answers

    Bacteria have only one type of RNA polymerase.

    <p>True</p> Signup and view all the answers

    Archaea have one type of RNA polymerase.

    <p>True</p> Signup and view all the answers

    Peptidoglycan is present in bacteria.

    <p>True</p> Signup and view all the answers

    Peptidoglycan is present in archaea.

    <p>False</p> Signup and view all the answers

    What is the first amino acid incorporated during translation in bacteria?

    <p>Formylmethionine.</p> Signup and view all the answers

    What is the first amino acid incorporated during translation in archaea?

    <p>Methionine.</p> Signup and view all the answers

    Histones are associated with DNA in bacteria.

    <p>False</p> Signup and view all the answers

    Histones are associated with DNA in archaea.

    <p>True</p> Signup and view all the answers

    What is the biological impact of bacteria and archaea?

    <p>The oldest fossils are of 3.5 billion-year-old bacteria, 1000 microbes (microscopic organisms) are in the human large intestine, and 700 microbes are in the human mouth.</p> Signup and view all the answers

    What are extremophiles?

    <p>Extremophiles are organisms that thrive in extreme habitats, such as hydrothermal vents, highly acidic environments, extremely cold regions, and highly saline waters.</p> Signup and view all the answers

    Study Notes

    Biological Hierarchy

    • Organisms are structured in a hierarchical order: atom → molecule → macromolecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.

    Nucleotide Structure

    • Each nucleotide comprises: one deoxyribose sugar, one phosphate group, and one nitrogenous base.

    Nitrogenous Bases

    • Purines (double ring): Adenine (A) and Guanine (G)
    • Pyrimidines (single ring): Cytosine (C) and Thymine (T)

    DNA Backbone

    • The DNA backbone alternates between phosphate groups and deoxyribose sugars.

    DNA Base Pairing

    • Nitrogenous bases are connected by hydrogen bonds.

    Genes and Genomes

    • Genes contain the genetic instructions for protein synthesis.
    • A gene is a segment of DNA that codes for a specific protein.
    • The genome encompasses all the genes of an individual.

    Chromatin Structure

    • Chromatin is a fine, filamentous material formed by the complex combination of DNA and proteins.
    • It's organized into a repeating pattern involving histones.

    Nucleosomes

    • A nucleosome is a structural unit of chromatin.
    • Comprised of a core particle (histones wrapped with DNA) and linker DNA connecting these core particles.

    Chromosomes

    • A chromosome consists of two identical DNA filaments known as sister chromatids.

    RNA Types

    • mRNA: Carries genetic instructions from DNA to ribosomes.
    • rRNA: Forms part of the ribosome, aiding protein synthesis.
    • tRNA: Brings amino acids to the ribosome for protein assembly, translating mRNA code.

    Genetic Code

    • A base triplet (three DNA nucleotides) codes for one amino acid.
    • A codon (three mRNA bases) corresponds to a particular amino acid.
    • Stop codons (UAG, UGA, and UAA) signal the end of protein synthesis.
    • AUG is the start codon.

    Central Dogma

    • Transcription: DNA is transcribed into mRNA within the nucleus.
    • Translation: mRNA is translated into a protein by ribosomes in the cytoplasm.

    Enzymes in DNA Replication

    • RNA polymerase: Enzyme that synthesizes mRNA from DNA template.
    • Helicase: Unwinds the DNA double helix.
    • DNA Polymerase: Adds new nucleotides to a growing DNA strand.
    • Ligase: Joins together the fragments of DNA.

    Essential Elements

    • Four elements (carbon, oxygen, nitrogen, and hydrogen) make up over 96% of an organism's matter.

    Atomic Structure

    • Atoms comprise a nucleus containing protons (positive charge) and neutrons (neutral charge), surrounded by orbiting electrons (negative charge).

    Elements and Isotopes

    • Elements consist entirely of one type of atom.
    • Atomic number is the number of protons in an atom's nucleus.
    • Mass number is the sum of protons and neutrons in an atom.
    • Isotopes are elements with varying numbers of neutrons but the same number of protons.
    • Atomic weight reflects the average mass of an element's naturally occurring isotopes.
    • Radioactive isotopes decay over time. -Key elements in organisms include carbon, oxygen, nitrogen, hydrogen, and phosphorus.

    Electron Shells

    • Electrons orbit the nucleus in specific energy shells.
    • Each shell has a specific number of orbitals, with a limit of 2 electrons for an orbital.
    • A shell with four orbitals can hold up to 8 electrons.

    Valence Electrons and Bonding

    • Valence shell is the outermost electron shell.
    • Valence electrons are important in chemical bonding and determining the atom's reactivity.
    • Atoms become most stable by filling their valence shells.

    Types of Bonds

    • Covalent bonds involve sharing valence electrons.
    • Nonpolar covalent bonds: Equal sharing of electrons.
    • Polar covalent bonds: Unequal sharing of electrons, leading to partial charges.
    • Ionic bonds involve the transfer of electrons and form oppositely charged ions (cations and anions).

    Electronegativity

    • Electronegativity is the measure of an atom's ability to attract shared electrons.
    • It depends on the number of protons and the distance of the valence shell from the nucleus.
    • Electronegativity increases moving up and to the right on the periodic table.

    pH and Buffers

    • pH is a measure of hydrogen ion concentration.
    • Buffers minimize changes in pH.
    • Acids release hydrogen ions in water.
    • Bases accept hydrogen ions or neutralize them.

    Water Properties

    • Hydrophobic molecules repel water.
    • Hydrophilic molecules attract water.
    • Hydrolysis involves the addition of water to break down molecules.

    Cells

    • Different cell types exist (eukaryotic and prokaryotic).
    • Prokaryotes lack membrane-bound organelles and a nucleus.
    • Eukaryotes have membrane-bound organelles, including a nucleus.

    Cell Transport

    • Passive transport moves substances down a concentration gradient (no energy required).
    • Active transport moves substances against a concentration gradient (requires energy).
    • Facilitated transport uses proteins to aid movement along a gradient.
    • Diffusion involves movement from high to low concentration.
    • Osmosis is the diffusion of water.

    Cell Structures

    • Cell membrane (plasma membrane) regulates material passage.
    • Cell wall (in some cells) provides structural support.
    • Nucleus houses DNA and controls genetic processes.
    • Mitochondria are the sites of cellular respiration.
    • Ribosomes synthesize proteins.

    Proteins

    • Proteins are composed of amino acids.
    • Amino acids contain an amino group, a carboxyl group, a hydrogen atom, and a variable R group.
    • Proteins have various functions depending on their amino acid sequence and structure (e.g., enzymes, structural proteins).
    • Glycoproteins are proteins with carbohydrate attachments, aiding cell recognition.

    Cell Processes

    • Transcription is the process of converting DNA to RNA.
    • Translation converts RNA to a protein.
    • Cell division involves stages like PMAT (prophase, metaphase, anaphase, telophase).

    Prokaryote Differences

    • Bacteria have peptidoglycan in their cell walls. Archaea do not.
    • Translation in Bacteria starts with formylmethionine, while in Archaea it starts with methionine.
    • Bacteria have one type of RNA polymerase, while Archaea have one as well.
    • Bacteria and Archaea differ in their structural components and genetic mechanisms.
    • Bacteria and Archaea are ubiquitous in various habitats on Earth.

    Extremophiles

    • Extremophiles survive in extreme environments, such as hydrothermal vents, acidic conditions, frigid temperatures or high salt concentrations.

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    Description

    This quiz covers the hierarchical organization of biological systems, the structure of nucleotides, and the components of DNA. It includes questions about nitrogenous bases, DNA backbone, and gene functions within the genome. Test your knowledge on these fundamental concepts of biology!

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