Biology: Macromolecules and Cellular Structure
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Questions and Answers

What is the primary function of carbohydrates in living organisms?

  • To perform various cellular functions
  • To generate energy through cellular respiration
  • To store and transmit genetic information
  • To provide energy and structure (correct)

    • Which organelle is responsible for generating energy through cellular respiration?

  • Ribosomes
  • Nucleus
  • Mitochondria (correct)
  • Endoplasmic Reticulum

    • During DNA replication, what is the purpose of the replication fork?

  • To elongate the new DNA strands
  • To synthesize new nucleotides
  • To unwind the double helix (correct)
  • To transcribe genetic information

    • Which type of macromolecule provides energy and structure in cells, and includes examples such as fats, oils, and cholesterol?

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

    What is the primary function of the cell membrane?

    <p>To regulate what enters and leaves the cell</p> Signup and view all the answers

    During DNA replication, what is the purpose of the synthesis step?

    <p>To add new nucleotides to the template strands</p> Signup and view all the answers

    Which organelle is responsible for protein synthesis?

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

    What is the primary function of ligation during DNA replication?

    <p>To seal gaps between nucleotides</p> Signup and view all the answers

    Which type of biological molecule is composed of fatty acids?

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

    What is the primary force responsible for the attraction between non-polar molecules in aqueous environments?

    <p>Hydrophobic interactions</p> Signup and view all the answers

    Which type of bond is typically found between atoms with high electronegativity?

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

    What is the primary function of nucleotides in biological systems?

    <p>To form the building blocks of nucleic acids</p> Signup and view all the answers

    Which type of biological molecule is composed of amino acids?

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

    What is the primary function of covalent bonds in biological systems?

    <p>To form strong bonds between atoms</p> Signup and view all the answers

    What type of interaction is responsible for the attraction between non-polar molecules in aqueous environments?

    <p>Hydrophobic interactions</p> Signup and view all the answers

    Which type of bond is typically found between atoms with low electronegativity?

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

    What is the function of the cytoskeleton in cellular structure?

    <p>To provide structural support and shape to the cell</p> Signup and view all the answers

    What is the primary function of carbohydrates in cells?

    <p>To provide energy and serve as structural components</p> Signup and view all the answers

    What type of interaction is responsible for the attraction between oppositely charged ions?

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

    What is the function of organelles in cellular structure?

    <p>To perform specialized functions within cells</p> Signup and view all the answers

    What type of molecule is important for protein-ligand interactions?

    <p>Non-polar molecules</p> Signup and view all the answers

    What is the primary function of the cell membrane?

    <p>To separate the cell from its environment and regulate transport</p> Signup and view all the answers

    Which type of biological molecule has a primary structure that involves an amino acid sequence?

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

    During DNA replication, which enzyme synthesizes new DNA strands and proofreads/edit them?

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

    What is the function of RNA primers during DNA replication?

    <p>to provide a starting point for DNA synthesis</p> Signup and view all the answers

    Which type of lipid molecule is commonly found in cell membranes?

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

    During DNA replication, which strand is synthesized continuously in the 5' to 3' direction?

    <p>leading strand</p> Signup and view all the answers

    What is the function of topoisomerase during DNA replication?

    <p>to relieve tension in the DNA ahead of the replication fork</p> Signup and view all the answers

    Which type of bond is typically found between atoms with high electronegativity in biological molecules?

    <p>polar covalent bond</p> Signup and view all the answers

    During DNA replication, what is the function of helicase?

    <p>to unwind the double helix</p> Signup and view all the answers

    What is the primary function of cholesterol in the cell membrane?

    <p>To increase fluidity at high temperatures</p> Signup and view all the answers

    What is the effect of temperature on the fluidity of the cell membrane?

    <p>↑ temperature increases fluidity, ↓ temperature decreases it</p> Signup and view all the answers

    What is the primary function of integral proteins in the cell membrane?

    <p>To move freely within the membrane</p> Signup and view all the answers

    What is the effect of unsaturated fatty acids on the fluidity of the cell membrane?

    <p>They increase fluidity</p> Signup and view all the answers

    What is the primary function of peripheral proteins in the cell membrane?

    <p>To facilitate cell-cell recognition</p> Signup and view all the answers

    What is the function of glycoproteins in the cell membrane?

    <p>To recognize other cells</p> Signup and view all the answers

    What is the effect of saturated fatty acids on the fluidity of the cell membrane?

    <p>They decrease fluidity</p> Signup and view all the answers

    What is the function of adhesion molecules in the cell membrane?

    <p>To attach cells to other things</p> Signup and view all the answers

    What is the primary difference between trans-unsaturated and cis-unsaturated fatty acids in terms of their arrangement in cell membranes?

    <p>Trans-unsaturated fatty acids pack more tightly, while cis-unsaturated fatty acids have a more severe kink.</p> Signup and view all the answers

    What type of transport requires energy and is involved in the bulk transport of large, hydrophilic molecules across the cell membrane?

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

    What is the primary characteristic of integral proteins that allows them to traverse the entire cell membrane?

    <p>They are amphipathic</p> Signup and view all the answers

    Which prefix means 'outside' and is often used in biology to describe processes that occur outside of a cell or organelle?

    <p>Exo-</p> Signup and view all the answers

    Which type of endocytosis involves the cell membrane wrapping around an extracellular substance, internalizing it into the cell via a vesicle or vacuole?

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

    What is the term for the process by which a cell engulfs a foreign particle or organism, leading to the formation of a symbiotic relationship?

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

    What is the purpose of receptor-mediated endocytosis in the cell?

    <p>To facilitate the binding of dissolved molecules to peripheral membrane receptor proteins</p> Signup and view all the answers

    Which of the following is an example of a cell that is capable of engulfing other cells or particles?

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

    Which type of transport involves the diffusion of small uncharged molecules or lipid-soluble molecules directly across the cell membrane?

    <p>Simple diffusion</p> Signup and view all the answers

    What is the term for the process by which a cell secretes a substance outside of the cell?

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

    What is the primary function of channel proteins in facilitated transport?

    <p>To facilitate the diffusion of large molecules across the cell membrane</p> Signup and view all the answers

    Which type of transport involves the movement of substances against their concentration gradient, requiring energy?

    <p>Active transport</p> Signup and view all the answers

    Which prefix means 'within' or 'inside' and is often used in biology to describe processes that occur within a cell or organelle?

    <p>Endo-</p> Signup and view all the answers

    What is the primary function of the cell membrane in terms of transport?

    <p>To regulate the movement of substances into and out of the cell</p> Signup and view all the answers

    What is the term for the process by which a cell takes in a substance from outside of the cell?

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

    Which suffix means 'relating to cells' and is often used in biology to describe cellular processes or structures?

    <p>-cyte</p> Signup and view all the answers

    What is the primary function of peripheral membrane proteins?

    <p>To assist in cell signaling or transport</p> Signup and view all the answers

    What is the result of a drug binding to a receptor protein?

    <p>The receptor protein transmits a signal through the lipid bilayer</p> Signup and view all the answers

    What is the characteristic of the nonpolar parts of phospholipids in the cell membrane?

    <p>They are found in the middle of the bilayer</p> Signup and view all the answers

    What is the role of receptor proteins in cell signaling?

    <p>To transmit a signal through the lipid bilayer</p> Signup and view all the answers

    What is the effect of an antagonist binding to a receptor protein?

    <p>The receptor protein is inhibited</p> Signup and view all the answers

    What is the characteristic of integral proteins that transmit a signal through the lipid bilayer?

    <p>They are transmembrane proteins</p> Signup and view all the answers

    What is the primary function of cholesterol in the cell membrane?

    <p>To regulate the fluidity of the membrane</p> Signup and view all the answers

    What is the result of a receptor protein transmitting a signal through the lipid bilayer?

    <p>A secondary response is triggered within the cell</p> Signup and view all the answers

    What is the primary component of bacterial cell walls?

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

    Which type of junction connects the extracellular matrix to the cytoskeleton?

    <p>Focal adhesions</p> Signup and view all the answers

    What is the function of the glycocalyx?

    <p>Adhesion, protection, and cell recognition</p> Signup and view all the answers

    Which type of junction is responsible for direct cell-to-cell communication?

    <p>Gap junctions</p> Signup and view all the answers

    What is the component of the cell wall of archaea?

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

    Which type of junction is involved in the connection of the extracellular matrix to intermediate filaments?

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

    What is the function of connexons?

    <p>Direct cell-to-cell communication</p> Signup and view all the answers

    What is the term for the connection between the extracellular matrix and the cytoskeleton?

    <p>Cell-matrix junction</p> Signup and view all the answers

    Study Notes

    Macromolecules

    • Definition: Large molecules composed of smaller molecules (monomers) bonded together
    • Four main types:
      1. Carbohydrates: Provide energy and structure (e.g., sugars, starches, cellulose)
      2. Proteins: Perform various functions (e.g., enzymes, hormones, structural proteins)
      3. Nucleic Acids: Store and transmit genetic information (e.g., DNA, RNA)
      4. Lipids: Provide energy and structure (e.g., fats, oils, cholesterol)

    Cellular Structure

    • Cell Membrane: Semi-permeable membrane surrounding the cell, composed of phospholipid bilayer and proteins
    • Cytoplasm: Gel-like substance inside the cell membrane, containing organelles and molecules
    • Nucleus: Membrane-bound organelle containing genetic material (DNA)
    • Mitochondria: Organelles responsible for generating energy (ATP) through cellular respiration
    • Endoplasmic Reticulum (ER): Network of membranous tubules and cisternae involved in protein synthesis and transport
    • Ribosomes: Small organelles responsible for protein synthesis

    DNA Replication

    • Process: Creation of an exact copy of DNA before cell division
    • Steps:
      1. Unwinding: Double helix is unwound, and replication fork is formed
      2. Unzipping: Hydrogen bonds between nucleotides are broken
      3. Synthesis: New nucleotides are added to template strands
      4. Elongation: New DNA strands are formed
      5. Ligation: Enzymes seal gaps between nucleotides

    Biological Molecules

    • Amino Acids: Building blocks of proteins (20 different types)
    • Nucleotides: Building blocks of nucleic acids (A, C, G, T, and U)
    • Fatty Acids: Building blocks of lipids
    • Carbohydrates: Simple sugars (e.g., glucose) and complex carbohydrates (e.g., starch, cellulose)

    Molecular Interactions

    • Hydrogen Bonds: Weak bonds between atoms with high electronegativity (e.g., oxygen, nitrogen) and hydrogen
    • Ionic Bonds: Strong bonds between atoms with large electronegativity differences
    • Covalent Bonds: Strong bonds between atoms sharing electrons
    • Van der Waals Forces: Weak bonds between non-polar molecules
    • Hydrophobic Interactions: Attraction between non-polar molecules in aqueous environments

    Macromolecules

    • Composed of smaller molecules (monomers) bonded together
    • Four main types: Carbohydrates, Proteins, Nucleic Acids, and Lipids
    • Carbohydrates: Provide energy and structure (e.g., sugars, starches, cellulose)
    • Proteins: Perform various functions (e.g., enzymes, hormones, structural proteins)
    • Nucleic Acids: Store and transmit genetic information (e.g., DNA, RNA)
    • Lipids: Provide energy and structure (e.g., fats, oils, cholesterol)

    Cellular Structure

    • Cell Membrane: Semi-permeable membrane surrounding the cell, composed of phospholipid bilayer and proteins
    • Cytoplasm: Gel-like substance inside the cell membrane, containing organelles and molecules
    • Nucleus: Membrane-bound organelle containing genetic material (DNA)
    • Mitochondria: Organelles responsible for generating energy (ATP) through cellular respiration
    • Endoplasmic Reticulum (ER): Network of membranous tubules and cisternae involved in protein synthesis and transport
    • Ribosomes: Small organelles responsible for protein synthesis

    DNA Replication

    • Process: Creation of an exact copy of DNA before cell division
    • Unwinding: Double helix is unwound, and replication fork is formed
    • Unzipping: Hydrogen bonds between nucleotides are broken
    • Synthesis: New nucleotides are added to template strands
    • Elongation: New DNA strands are formed
    • Ligation: Enzymes seal gaps between nucleotides

    Biological Molecules

    • Amino Acids: 20 different types, building blocks of proteins
    • Nucleotides: Building blocks of nucleic acids (A, C, G, T, and U)
    • Fatty Acids: Building blocks of lipids
    • Carbohydrates: Simple sugars (e.g., glucose) and complex carbohydrates (e.g., starch, cellulose)

    Molecular Interactions

    • Hydrogen Bonds: Weak bonds between atoms with high electronegativity (e.g., oxygen, nitrogen) and hydrogen
    • Ionic Bonds: Strong bonds between atoms with large electronegativity differences
    • Covalent Bonds: Strong bonds between atoms sharing electrons
    • Van der Waals Forces: Weak bonds between non-polar molecules
    • Hydrophobic Interactions: Attraction between non-polar molecules in aqueous environments

    Molecular Interactions

    • Hydrogen bonds are weak electrostatic attractions between molecules, crucial for maintaining DNA structure and protein folding
    • Ionic bonds are strong electrostatic attractions between oppositely charged ions, essential for protein structure and cell signaling
    • Van der Waals forces are weak attractions between non-polar molecules, significant for protein-ligand interactions
    • Hydrophobic interactions occur between non-polar molecules, vital for protein structure and membrane formation

    Cellular Structure

    • The cell membrane is a semi-permeable membrane separating the cell from its environment, composed of a phospholipid bilayer and proteins
    • Cytoplasm is a gel-like substance inside the cell membrane, containing organelles and cytosol
    • Organelles are specialized structures within cells, including mitochondria, ribosomes, and lysosomes
    • The cytoskeleton is a network of filaments providing structural support and shape to the cell

    Biological Molecules

    • Carbohydrates serve as energy sources, structural components, and signaling molecules
    • Monosaccharides, such as glucose, disaccharides, like sucrose, and polysaccharides, like cellulose, are types of carbohydrates
    • Proteins are structural, functional, and regulatory molecules, with primary structure referring to amino acid sequence, secondary structure comprising α-helices and β-sheets, and tertiary structure describing their 3D shape
    • Lipids function as energy storage, structural components, and signaling molecules, including triglycerides (fats and oils), phospholipids (cell membrane), and steroids (hormones)

    DNA Replication

    Initiation

    • Unwinding of the double helix occurs at the origin of replication, accompanied by the binding of helicase and primase

    Unwinding and Synthesis

    • The separation of DNA strands enables synthesis of new strands in the 5' to 3' direction
    • Synthesis occurs continuously on the leading strand and discontinuously on the lagging strand

    Elongation and Editing

    • Nucleotides are added to the growing strands, with proofreading and editing occurring simultaneously

    Termination

    • DNA replication is completed, and replication forks are resolved

    Leading Strand Synthesis

    • The leading strand is synthesized continuously in the 5' to 3' direction

    Lagging Strand Synthesis

    • The lagging strand is synthesized discontinuously in the 5' to 3' direction, resulting in the formation of Okazaki fragments
    • RNA primers provide the starting point for DNA synthesis
    • DNA ligase seals gaps between Okazaki fragments, forming a continuous strand

    Replication Fork and Enzymes

    • The replication fork is the region where DNA replication occurs, with leading and lagging strands
    • Helicase unwinds the double helix, creating the replication fork
    • Topoisomerase relieves tension in the DNA ahead of the replication fork
    • DNA polymerase synthesizes new DNA strands, proofreading and editing simultaneously

    Cell Membrane Structure

    • Phospholipids are the main component of the cell membrane, consisting of a glycerol backbone, one phosphate group (hydrophilic), and two fatty acid tails (hydrophobic), making them amphipathic.
    • Cholesterol is present in small amounts, has four fused hydrocarbon rings, and is a precursor to steroid hormones, also helping to regulate membrane fluidity.
    • Membrane proteins are either integral (transmembrane) or peripheral, with integral proteins traversing the entire bilayer and being amphipathic, while peripheral proteins are found on the outside of the bilayer and are generally hydrophilic.

    Cell Membrane Functions

    • Integral proteins can assist in cell signaling or transport, with some acting as receptors, triggering secondary responses within the cell.
    • Receptor proteins can transmit signals through the lipid bilayer, and drugs that bind to receptors can be either agonists or antagonists.
    • Peripheral proteins can be involved in adhesion, attaching cells to other things, and act as anchors for the cytoskeleton.
    • Cell membranes also contain glycoproteins, which have carbohydrate chains, used for cellular recognition.

    Cell Membrane Fluidity

    • The fluid mosaic model describes how the components of the cell membrane can move freely within the membrane, with the cell membrane containing many different kinds of structures.
    • The fluidity of the cell membrane can be affected by temperature, cholesterol, and the degree of unsaturation of fatty acids.
    • Saturated fatty acids pack more tightly than unsaturated fatty acids, which have double bonds that may introduce kinks.

    Cell Wall Structure

    • Peptidoglycan is a polysaccharide with peptide chains, the primary component of bacterial cell walls.
    • The cell wall of archaea is also made of polysaccharides, but does not contain peptidoglycan.
    • The glycocalyx is a glycolipid/glycoprotein coat found mainly on bacterial and animal epithelial cells, helping with adhesion, protection, and cell recognition.

    Cell-Matrix Junctions

    • Cell-matrix junctions connect the extracellular matrix (ECM) to the cytoskeleton, with two types: focal adhesions and hemidesmosomes.
    • Focal adhesions connect the ECM to actin microfilaments inside the cell via integrins.
    • Hemidesmosomes connect the ECM to intermediate filaments inside the cell via integrins.

    Crossing Cell Membranes

    • Cytosis refers to the bulk transport of large, hydrophilic molecules across the cell membrane, requiring energy (active transport mechanism).
    • Endocytosis involves the cell membrane wrapping around an extracellular substance, internalizing it into the cell via a vesicle or vacuole.
    • Phagocytosis, pinocytosis, and receptor-mediated endocytosis are different forms of endocytosis.
    • There are three types of transport across the cell membrane: simple diffusion, facilitated transport, and active transport.
    • Simple diffusion involves the diffusion of small uncharged molecules or lipid-soluble molecules directly across the cell membrane, down their concentration gradient, without using energy.
    • Facilitated transport involves the diffusion of large or charged molecules across the cell membrane, down their concentration gradient, without using energy, through channel proteins.
    • Active transport involves the transport of substances against their concentration gradient, requiring energy.

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