Medical Biology for Medical Students
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Questions and Answers

What is the central part of the living world according to the preface?

  • Cells
  • Organisms
  • Human organism (correct)
  • Ecosystems

    • Aristotle is credited with being one of the first biologists.

    True

    What does DNA replication refer to?

    Copying DNA molecule

    _______ is the increase of the body weight and sizes.

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

    Match the following characteristics with their definitions:

    <p>Metabolism = Flow of energy and cycling of material between living organisms and environment. Regulation = Continuous adjustment to the always-changing environment to maintain homeostasis. Response and motion = Ability to react to external stimuli, usually expressed in motion. Heredity and variation = Transmission of traits through generations and ability of organisms to acquire new traits. Growth and development = Increase of body weight and sizes, and individual development of an organism.</p> Signup and view all the answers

    What are the two main types of microscopes mentioned in the text?

    <p>Light microscope and electron microscope</p> Signup and view all the answers

    The resolution power of a light microscope is 200 nm.

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

    What is the primary function of proteins?

    <p>Provide diversity of life (living organisms)</p> Signup and view all the answers

    ______ and external stimuli like sun radiation, temperature, and diet can regulate growth.

    <p>Growth hormone</p> Signup and view all the answers

    Match the life organization levels with their descriptions:

    <p>Biological microsystem = Includes molecular, subcellular, and cellular sublevels Biological mesosystem = Includes tissues, organs, organ-systems, and organism Biological macrosystem = Consists of population, community, ecosystem, and biosphere</p> Signup and view all the answers

    What is denaturation of proteins?

    <p>An irreversible change where peptide bonds are broken</p> Signup and view all the answers

    What is the primary function of enzymes?

    <p>Catalytic function</p> Signup and view all the answers

    Actin and myosin are involved in the contractile function of muscle cells.

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

    Hemoglobin transfers _______ in the blood.

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

    Match the protein with its function:

    <p>Antibodies = Immune protection Enzymes = Catalytic function Actin and myosin = Contractile function Hemoglobin = Transport function</p> Signup and view all the answers

    What is the primary difference between RNA and DNA nucleotides?

    <p>RNA contains ribose sugar, DNA contains deoxyribose sugar</p> Signup and view all the answers

    RNA synthesis on a DNA template is known as translation.

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

    What is the primary role of tRNA in protein synthesis?

    <p>Transfer amino acids to the ribosomes</p> Signup and view all the answers

    In DNA replication, the unit of replication is known as a _______.

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

    Match the following RNA types with their functions:

    <p>tRNA = Transfers specific amino acids to the ribosomes rRNA = Forms the ribosome subunits and catalyzes peptide bond formation snRNA = Involved in splicing pre-messenger RNA during post-transcriptional modification</p> Signup and view all the answers

    What is the function of DNA-polymerase in DNA replication?

    <p>Proof-reading the newly added nucleotides</p> Signup and view all the answers

    What is the function of telomerase in DNA replication?

    <p>Elongating the maternal strands on telomeres</p> Signup and view all the answers

    Epigenetic factors like DNA methylation can only affect gene expression at the transcription stage.

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

    The RNA molecule in transcription elongates in the _____ direction.

    <p>5' to 3'</p> Signup and view all the answers

    Match the following stages of transcription with their descriptions:

    <p>Initiation = Binding of RNA-polymerase to the promoter Elongation = RNA-polymerase elongating the RNA molecule Termination = Transcription ending at a terminator signal</p> Signup and view all the answers

    What are the non-cellular forms of life that do not have common cell structure?

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

    Viruses are obligate intracellular parasites that can reproduce outside of a host cell.

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

    What are the two types of viruses based on their genetic material?

    <p>DNA viruses and RNA viruses</p> Signup and view all the answers

    Viroids are small circular RNA molecules without a protein capsid that predominantly affect ______ cells.

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

    Match the following terms with their descriptions:

    <p>Prions = Infective protein agents not bound to genetic material Viroids = Small circular RNA molecules without protein capsids affecting plant cells Bacteriophages = Viruses that affect bacteria composed of DNA or RNA, tail and tail fibers Prokaryotes = Single-cell organisms without a true nucleus, such as bacteria and blue-green algae</p> Signup and view all the answers

    Study Notes

    Introduction to Medical Biology

    • The book focuses on eukaryotic cell biology, medical genetics, and parasitology, with a medical orientation.
    • It covers the fundamental aspects of cell structure and processes, making it accessible to medical students.

    History of Biology

    • The first biologists were ancient Greek philosophers, such as Aristotle.
    • Hippocrates is credited with being the first person to believe that diseases were caused naturally, rather than by superstition.
    • Leonardo da Vinci investigated the human body through dissection and produced anatomical drawings.
    • The invention of the microscope by Robert Hooke in 1665 and Anton van Leeuwenhoek's discovery of single-celled eukaryotic organisms and bacteria in 1676 opened up a new world of living things.
    • Theodor Schwann and Matthias Schleiden's work on cell theory in 1839 established that animal tissue is also composed of cells.
    • Carl Linnaeus developed the binomial nomenclature for classifying living organisms in the 18th century.
    • Louis Pasteur's work on microorganisms and vaccination in the 19th century led to the development of pasteurization.
    • Charles Darwin's theory of evolution by natural selection in the 19th century revolutionized the field of biology.
    • Gregor Mendel's work on inheritance in the 19th century earned him the title of "father of genetics."
    • The 20th and 21st centuries have seen an exponential growth in biology, with advances in fields such as microbiology and genetics.

    Characteristics of Life

    • Living organisms are characterized by:
      • Ordered structure: a hierarchical organization of parts, with each level made up of smaller units.
      • Metabolism: the flow of energy and cycling of materials between living organisms and their environment.
      • Reproduction: the ability to produce a copy of oneself to continue the species.
      • Repairing (regeneration): the ability to repair damaged or aged cells and tissues.
      • Regulation: the ability to adjust to changes in the environment, maintaining homeostasis.
      • Response and motion: the ability to react to external stimuli and move in response to them.
      • Heredity and variation: the transmission of traits through generations and the ability to acquire new traits.
      • Growth and development: the increase in size and complexity of an organism over time.

    Levels of Life Organization

    • Biological microsystem: molecular, subcellular, and cellular levels.
    • Mesosystem: tissue, organ, organ system, and organism levels.
    • Macrosystem: population, community, ecosystem, and biosphere levels.

    Microscopy

    • Microscopes are used to study cells and tissues in medical practice.
    • Light microscopes are used to study cells and tissues, with a resolution power of 200 nm.
    • Electron microscopes have a higher resolution power of 0.5 nm.
    • The microscope consists of mechanical, optical, and light parts.
    • The mechanical part includes the base, stand, ocular tube, and revolver.
    • The optical part includes the eyepiece and objectives.
    • The light part includes the mirror or lamp illuminator, iris diaphragm, and condenser.
    • The total magnification of a microscope is the product of the magnification of all the lenses.### Cell Organic Ingredients
    • Cells are composed of organic compounds, which are based on carbon and are known as organic compounds.
    • Proteins are the most important organic compounds, making up more than 50% of the dry weight of most cells.

    Protein Structure

    • Proteins are made up of monomers called amino acids, which are linked together by peptide bonds.
    • Amino acids have a central asymmetric carbon atom and four different partners: an amino group, a carboxyl group, a hydrogen atom, and a variable group (R).
    • There are 20 different types of amino acids that can be combined to form millions of proteins.
    • The sequence of amino acids in a protein determines its primary structure.
    • The secondary structure of a protein is formed by hydrogen bonds between different amino acids of the folding chain.
    • The tertiary structure is constructed by various interactions between different chemical groups, such as hydrogen bonds, hydrophobic interactions, ionic bonds, and disulfide bonds.

    Protein Functions

    • Proteins perform various functions, including:
      • Structural function: providing structure to cells and tissues.
      • Catalytic function: speeding up chemical reactions as enzymes.
      • Regulatory function: regulating various functions of the organism as hormones.
      • Signaling function: transmitting signals into the cell as receptors.
      • Contractile function: helping in motility.
      • Transport function: transferring chemicals.
      • Immune protection function: protecting the body against pathogens.
      • Energy source function: generating energy in certain conditions.

    Carbohydrates

    • Carbohydrates are organic substances consisting of carbon, hydrogen, and oxygen.
    • They are the simplest form of organic compounds and are an important source of energy.
    • Types of carbohydrates include:
      • Monosaccharides (simple sugars): trioses, tetroses, pentoses, and hexoses.
      • Disaccharides: sucrose, lactose, and maltose.
      • Oligosaccharides: made up of 3-20 hexose sugars.
      • Polysaccharides: starch, cellulose, and glycogen.

    Lipids

    • Lipids are a group of organic substances that are not soluble in water, but are soluble in organic solvents.
    • They are hydrophobic and have a hydrophilic head and a hydrophobic tail.
    • Types of lipids include:
      • Fats and oils: triglycerides consisting of glycerol and three fatty acids.
      • Phospholipids: consisting of glycerol connected to a phosphate group and two fatty acids.
      • Steroids: characterized by a carbon skeleton consisting of four fused rings.

    Nucleic Acids

    • Nucleic acids are biological polymers that provide continuity of life and expression of traits.
    • There are two types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
    • DNA is a double-stranded polynucleotide with a double helix structure, where two strands are twisted together.
    • RNA is a single-stranded polynucleotide with a varying amount of secondary structure.

    DNA Structure

    • Each DNA strand is a polymer of monomers called nucleotides.
    • Each nucleotide is composed of a nitrogenous base, a deoxyribose, and a phosphate group.
    • The nitrogenous bases are paired in a complementary manner, with A always pairing with T, and G always pairing with C.
    • The two strands of DNA are antiparallel, with the C3' end of one strand facing the C5' end of the other strand.

    RNA Structure

    • RNA is a single-stranded polynucleotide with a varying amount of secondary structure.
    • The RNA nucleotides vary from DNA nucleotides, with the pentose sugar being ribose instead of deoxyribose.
    • RNA contains uracil (U) instead of thymine (T).

    Human Genome

    • The human genome is composed of 23 nuclear DNA molecules (chromosomes) with a total of about 3 billion base pairs.
    • The human genome is completed by a mitochondrial DNA molecule with about 16,000 base pairs and 37 genes.
    • Only about 1.5% of the human genome carries information about proteins (protein-coding genes).
    • The remaining 98.5% of the genome is presented in non-coding sequences, which include repetitive DNA sequences.

    DNA Sequences and Repeats

    • DNA sequences can be classified into three patterns:
      • Unique sequences or single repeats: encode for various proteins providing certain traits.
      • Moderately repeated sequences: include "house-keeping" genes, transposons, and other repetitive elements.
      • Highly repetitive sequences: include satellite DNA, microsatellites, and minisatellites.### Telomeres and Satellite DNA
    • Telomeric DNA prevents the ends of chromosomes from sticking together and shortening after each replication
    • Satellite DNA refers to small, repetitive DNA fragments that separate from bulk DNA in centrifugation
    • Microsatellites and minisatellites are classified as Variable Number of Tandem Repeats (VNTR), with high mutation rates and unique lengths in each individual
    • VNTR analysis is used in DNA fingerprinting for kinship testing, forensic identification, and cancer diagnosis

    Non-coding RNAs (ncRNAs)

    • In addition to mRNA, tRNA, and rRNA, there are many ncRNAs that do not code for proteins
    • ncRNAs regulate gene expression after mRNA synthesis, from modification to translation
    • Structural ncRNAs include tRNA, rRNA, and snRNA, while regulatory ncRNAs include miRNA, siRNA, and Xist
    • Ribosomal RNA (rRNA) is the largest RNA molecule, with a structural role in forming ribosome subunits
    • Transport RNA (tRNA) transfers specific amino acids to ribosomes in protein synthesis

    Epigenetics and Gene Regulation

    • Epigenetics refers to mechanisms of gene regulation that do not change the DNA sequence
    • Non-coding RNAs are important regulators of multiple biological functions, and their dysregulation is implicated in diseases
    • siRNAs and miRNAs can silence gene expression by degrading mRNA
    • Epigenetic control involves transcription, transcription factors, histone modification, and DNA methylation

    DNA Replication

    • DNA replication occurs before mitosis, producing two identical DNA molecules
    • The process involves multiple enzymes, including helicase, topoisomerase, DNA polymerase, and ligase
    • The semi-conservative model of DNA replication produces one old and one new strand in each daughter molecule
    • The replication process involves initiation, elongation, and termination

    Transcription

    • Transcription is the process of transferring genetic information from DNA to RNA
    • RNA polymerase catalyzes transcription, which occurs in three stages: initiation, elongation, and termination
    • The primary transcript RNA undergoes processing to become mature mRNA, including capping, splicing, and polyadenylation

    Epigenetic Control of Gene Activity

    • Epigenetic control involves transcription factors, histone modification, and DNA methylation
    • Methylation of CG-rich regions in DNA and histone de-acetylation can silence gene expression
    • Alternative splicing allows for different proteins to be produced from a single gene

    Genetic Code

    • The genetic code is a triplet code, where each codon corresponds to an amino acid or stop signal
    • The code is redundant, specific, universal, non-overlapping, and continuous
    • The genetic code is translated into a sequence of amino acids in a polypeptide chain during protein synthesis

    Translation

    • Translation is the process of interpreting the genetic code to build a protein
    • The process involves ribosomes, tRNA, mRNA, amino acids, ATP, and enzymes
    • Translation consists of three stages: initiation, elongation, and termination

    Central Dogma of Biology

    • The central dogma describes the flow of information from DNA to RNA to protein
    • Although originally considered a dogma, exceptions have been found, including reverse transcription in retroviruses and RNA synthesis in viruses

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    This quiz covers the fundamental aspects of cell structure and processes, focusing on eukaryotic cell biology and its relation to human disease. It also introduces principles of classical genetics and medical genetics, as well as general parasitology concepts.

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