Biology Chapter on Lipids and Proteins
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Questions and Answers

What is a primary characteristic of lipids?

  • They are soluble in water.
  • They form nuclear membranes.
  • They primarily consist of amino acids.
  • They are soluble in non-polar organic solvents. (correct)

    • What constitutes the main energy storage in the body?

  • Amino acids
  • Cholesterol
  • Phospholipids
  • Triglycerides (correct)

    • Which group is associated with fatty acids that allows them to link to other molecules?

  • Methyl group
  • Carboxyl group (correct)
  • Amino group
  • Hydroxyl group

    • Which type of lipid is primarily important for membrane structure?

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

    What is the main role of proteins in cells?

    <p>Perform most of the cell's functions.</p> Signup and view all the answers

    What defines the unique properties of an amino acid?

    <p>The side chain attached to the α-carbon.</p> Signup and view all the answers

    Which structure is formed by the folding of a polypeptide chain?

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

    What percentage of a cell's mass is typically contributed by proteins?

    <p>10-20%</p> Signup and view all the answers

    Which component contributes to the structure of triglycerides?

    <p>Glycerol and three fatty acids</p> Signup and view all the answers

    In what cellular location are triglycerides stored?

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

    What is the primary characteristic of water that allows it to dissolve many polar molecules?

    <p>Its uneven distribution of electrons</p> Signup and view all the answers

    Which type of molecules are described as hydrophilic?

    <p>Polar or charged molecules that dissolve easily in water</p> Signup and view all the answers

    What are ions primarily required for in cellular processes?

    <p>Transmission of electrical signals in nerves and muscles</p> Signup and view all the answers

    Which functional group is associated with the hydrophilic properties of certain molecules?

    <p>Amino groups</p> Signup and view all the answers

    What is the simplest form of carbohydrates, also known as sugars?

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

    What is glycogen primarily used for in the body?

    <p>Storage of energy for the body</p> Signup and view all the answers

    What type of bond links monosaccharides to form larger carbohydrates?

    <p>Glycosidic bonds</p> Signup and view all the answers

    Which of the following is a characteristic of hydrophobic molecules?

    <p>They are non-polar or uncharged.</p> Signup and view all the answers

    Which ions are essential for the transmission of electrical signals in muscles and nerves?

    <p>Calcium and sodium ions</p> Signup and view all the answers

    In what form is glucose primarily stored in the human body?

    <p>As glycogen in liver and muscles</p> Signup and view all the answers

    What roles do functional proteins primarily serve in biological processes?

    <p>Serving as catalysts for specific reactions</p> Signup and view all the answers

    Which of the following statements accurately describes prokaryotic cells?

    <p>They can divide very quickly, typically every 20 minutes.</p> Signup and view all the answers

    How do nucleotides contribute to the genetic makeup of organisms?

    <p>They are linked by phosphodiester bonds to create nucleic acids.</p> Signup and view all the answers

    What is the primary distinguishing feature of Gram-negative bacteria?

    <p>They have two membranes with a thin layer of peptidoglycan.</p> Signup and view all the answers

    What essential role does adenosine triphosphate (ATP) play in cellular functions?

    <p>It acts as a carrier of energy for various cellular processes.</p> Signup and view all the answers

    Which statement accurately describes eukaryotic cells?

    <p>Their DNA is organized into linear strands within a nucleus.</p> Signup and view all the answers

    What is the primary function of mitochondria in cells?

    <p>Energy production through nutrient breakdown</p> Signup and view all the answers

    Which process allows cells to synthesize protein molecules from the DNA sequence?

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

    What component of cells stores hereditary information?

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

    What chemical process is involved in breaking down glucose to produce ATP?

    <p>Cellular respiration</p> Signup and view all the answers

    During which phase do cells duplicate their DNA?

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

    Which four nitrogenous bases are found in nucleotides of DNA?

    <p>Adenine, Guanine, Thymine, Cytosine</p> Signup and view all the answers

    What is produced as a result of DNA replication?

    <p>Identical daughter cells</p> Signup and view all the answers

    How do cells ensure accuracy during DNA replication?

    <p>Using template strands for synthesis</p> Signup and view all the answers

    What is the chemical composition primarily involved in the cell's functions?

    <p>Same 6 main substances across different cell types</p> Signup and view all the answers

    What is the role of mRNA during protein synthesis?

    <p>To guide the synthesis of proteins</p> Signup and view all the answers

    What is the smallest unit capable of performing life functions?

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

    Which of the following correctly describes one of the main functions of a cell?

    <p>To synthesize proteins that perform various functions</p> Signup and view all the answers

    How do cells obtain energy, specifically in animal cells?

    <p>From chemical bonds in the food they consume</p> Signup and view all the answers

    What do all living things have in common?

    <p>They are composed of cells</p> Signup and view all the answers

    Which option accurately describes how cells reproduce?

    <p>By growing and then dividing into two</p> Signup and view all the answers

    What distinguishes prokaryotic cells from eukaryotic cells?

    <p>Eukaryotic cells are larger than prokaryotic cells</p> Signup and view all the answers

    What component of the cell performs the role of reaction catalysts?

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

    Which of the following is NOT a basic job of a cell?

    <p>Storing waste products</p> Signup and view all the answers

    Which statement best describes the morphology of cells?

    <p>Cells exhibit diverse shapes and functions</p> Signup and view all the answers

    Study Notes

    Cellular & Molecular Biology MD105

    • Course taught by Dr. C. Michaeloudes at the European University Cyprus, School of Medicine
    • Course content focuses on cell structure and function.

    Lecture Objectives

    • Understand what a cell is and its functions
    • Identify the main chemical components of cells
    • Recognize the diversity of cell morphology and function
    • Differentiate prokaryotic and eukaryotic cells.

    What is a cell

    • The smallest unit capable of performing life functions
    • Small, membrane-enclosed units
    • Filled with a concentrated aqueous solution containing numerous chemicals.
    • Capable of self-replication: growing and dividing in two
    • The fundamental units of life

    Cell structure & Function 1

    • Living organisms (sea urchins, mice, seaweed) are diverse.
    • All living things are made of cells.

    The Main Functions of a Cell

    • Generate energy: energy is needed for cellular activities
      • Animal cells obtain energy from chemical bonds in food.
      • Plant cells obtain energy from sunlight.
    • Synthesize proteins: proteins perform all functions in a cell, including cell structure, enzymes, signaling molecules, and receptors (communication)
    • Make more cells: cells divide to make identical copies for growth and repair.

    Cells Generate Energy

    • Cells break down nutrients (glucose/fatty acids) using oxygen to produce chemical energy(ATP)
    • This process occurs in structures called mitochondria.

    Instructions for Cell Functions

    • The instructions for all cell functions are stored in DNA.
    • Cells need to store their hereditary information (like computers store information on hard drive or cloud).
    • DNA is deoxyribonucleic acid.
    • DNA is a long polymer chain of nucleotides.
    • Nucleotides contain 4 different nitrogenous bases (adenine, guanine, thymine, cytosine).
    • Nucleotides join together in a linear sequence encoding genetic information.

    The DNA Code for Proteins

    • DNA sequence guides the synthesis of mRNA molecules (transcription).
    • mRNA sequence guides the synthesis of protein molecules (translation).

    Cells Make Identical Copies

    • Cells make copies of themselves that are genetically identical (have the same DNA)
    • To do this, cells duplicate their DNA and then divide in two.
    • Daughter cells are able to divide further, producing more cells.
    • This process is called DNA replication.
    • The two strands of the DNA helix are unzipped and used as templates to create complementary strands.

    Chemical Composition of Cells

    • Cells are composed of many chemicals, involved in the same types of chemical reactions.
    • 6 main components:
      • Water: most cells (except fat cells) contain 70-85%
      • Ions (calcium, sodium, magnesium, phosphate)
      • Amino acids
      • Sugars (monosaccharides, disaccharides, polysaccharides)
      • Fatty acids
      • Nucleotides

    Water

    • Most cells contain 70-85% water.
    • Water is polar—it has an uneven distribution of electrons.
    • Water molecules are held together by hydrogen bonds.
    • Polar and charged molecules can dissolve in water by forming hydrogen bonds.
    • Water is the medium for most reactions in the cell.

    Hydrophilic and Hydrophobic Molecules

    • Hydrophilic molecules easily dissolve in water ("water-loving").
    • Polar or charged molecules. Form hydrogen bonds with water.
    • Hydrophobic molecules do not dissolve in water ("water-fearing").
    • Non-polar/ uncharged side chains. Do not form hydrogen bonds with water.
    • Contain hydrocarbon chains or ring structures.

    Ions

    • Atoms carrying an electrical charge (anions or cations).
    • Essential for chemical reactions and key cellular control mechanisms.
    • Important for transmitting signals in nerves and muscles.

    Sugars

    • Simplest forms are monosaccharides.
    • Made up of carbon, hydrogen, and oxygen (CH₂O)ₙ where n = 3, 4, 5 or 6.
    • Monosaccharides link to form larger carbohydrates (disaccharides, polysaccharides).
    • Glucose is a vital energy source for cells; it is broken down into smaller molecules through reactions releasing energy in the form of ATP. Glycogen is how glucose is stored.

    Fatty Acids

    • Organic molecules with a hydrocarbon chain (hydrophobic) and a carboxyl group (hydrophilic).
    • Broken down in mitochondria for energy production.
    • Form complex lipid molecules (e.g., phospholipids, cholesterol, triglycerides).

    Lipids

    • Organic molecules insoluble in water but soluble in non-polar organic solvents.
    • Important in cell membranes and energy storage.
    • Types include phospholipids, cholesterol, and triglycerides.

    Phospholipids and Cholesterol

    • Main components of cell membranes.
    • Phospholipids have a hydrophilic head and hydrophobic tails.
    • Cholesterol contributes to membrane structure and fluidity.

    Triglycerides

    • The body's main energy store.
    • Made of glycerol and three fatty acids.
    • Stored in cytoplasm as lipid droplets.

    Amino Acids

    • Small organic molecules with a carboxyl group (-COOH) and an amino group (-NH₂) attached to a central α-carbon.
    • The α-carbon carries a specific side chain, which distinguishes amino acids.

    Proteins

    • Polymers of amino acids joined by peptide bonds.
    • Folded into a 3D structure for function.
    • Perform most cell functions.
    • Two main types: structural and functional proteins.

    Structural Proteins

    • Long chains of proteins forming filaments (actin, intermediate, microtubules).
    • Form the cytoskeleton—maintaining cell shape and enabling movement.
    • Found outside the cell in connective tissues, tendons, and ligaments.

    Functional Proteins

    • Mainly enzymes—catalysts for specific reactions in the cell.
    • Speed up the rate of chemical reactions.
    • Bind to specific molecules (ligands) and convert them into modified products.

    Nucleotides

    • Composed of a 5-carbon sugar (ribose or deoxyribose), a nitrogen-containing base, and one or more phosphate groups.
    • Building blocks of nucleic acids (DNA and RNA).
    • Bases include adenine, thymine, uracil, cytosine, and guanine.

    Nucleic Acids

    • Polymers of nucleotides linked by phosphodiester bonds.
    • Store and retrieve biological information.

    Adenosine Triphosphate (ATP)

    • A molecule that carries energy needed for cellular processes (e.g., muscle contraction, nerve firing).
    • Stores chemical energy in high-energy phosphate bonds.
    • Energy released by the cleavage (breakage) of phosphate bonds.

    Small Organic Molecules

    • Building blocks of macromolecules (sugars, fatty acids, amino acids, nucleotides)

    The Diversity of Cells

    • The human body has ~30 trillion cells and over 200 cell types.
    • Different cell types have different morphology and function.
    • Cell types vary in life spans

    Prokaryotic Cells

    • Smaller than eukaryotic cells.
    • Have simpler structure without a nucleus or other membrane-bound organelles.
    • Contain a circular DNA molecule in a nucleoid region.
    • Cell wall is a thick protective layer outside plasma membrane, and cell membranes enclose the cytoplasm.
    • Divide rapidly (e.g., every 20 minutes).
    • Examples: Bacteria, Archaea.
    • Survive in various environments.

    Eukaryotic Cells

    • Larger than prokaryotic cells.
    • Have a nucleus and other membrane-bound organelles.
    • Contain linear DNA molecules in the nucleus.
    • No cell wall, only a cell membrane.

    Classification of Bacteria

    • Traditionally categorized by shape (spherical, rod-shaped, spiral).
    • Classified as Gram-positive or Gram-negative based on cell wall structure and Gram stain retention.

    Prokaryotic vs Eukaryotic Cell Structures

    • Prokaryotic—no nucleus; circular DNA; no membrane-bound organelles.
    • Eukaryotic—has a nucleus; linear DNA; has membrane-bound organelles.

    The Tree of Life

    • Three major divisions of life: Bacteria, Archaea, and Eukaryotes.
    • Genome analysis suggests the first eukaryotes emerged from an archaeal cell engulfing a bacterium.

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    Cell Structure and Function 1 Cellular & Molecular Biology F2024 PDF

    Description

    Test your knowledge on the characteristics and functions of lipids and proteins in biological systems. This quiz covers key concepts such as energy storage, membrane structure, and molecular properties. Ideal for biology students looking to reinforce their understanding of these essential macromolecules.

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