Cellular Communication Lecture 1
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Questions and Answers

What is the primary characteristic of autocrine signaling?

  • Cells respond to molecules they produce themselves. (correct)
  • It affects nearby cells only.
  • It requires direct membrane contact.
  • It involves the release of neurotransmitters at synapses.
  • Which type of signaling involves cells affecting other target cells in their proximity?

  • Paracrine signaling (correct)
  • Autocrine signaling
  • Endocrine signaling
  • Contant-dependent signaling
  • What type of receptors do most hydrophilic signaling molecules bind to?

  • Cell surface receptors (correct)
  • Intracellular receptors
  • Cytoplasmic receptors
  • Nuclear receptors
  • Which of the following is a characteristic of endocrine signaling?

    <p>Hormones are transported via the bloodstream. (C)</p> Signup and view all the answers

    What distinguishes synaptic signaling from other forms of cell communication?

    <p>It is performed by neurons transmitting signals electrically. (B)</p> Signup and view all the answers

    What is true about intracellular receptors?

    <p>They require signaling molecules to diffuse through the membrane. (C)</p> Signup and view all the answers

    What is a feature of contant-dependent signaling?

    <p>It requires membrane-to-membrane contact. (D)</p> Signup and view all the answers

    Which type of molecule typically cannot cross the cell membrane directly?

    <p>Hydrophilic molecules (D)</p> Signup and view all the answers

    What is the primary function of carbohydrates in the human body?

    <p>To serve as a major source of energy (D)</p> Signup and view all the answers

    Which type of carbohydrate cannot be hydrolyzed into simpler sugars?

    <p>Monosaccharides (D)</p> Signup and view all the answers

    Which of the following is NOT a function of carbohydrates?

    <p>Acting as storage for genetic information (C)</p> Signup and view all the answers

    Oligosaccharides are classified as sugars composed of how many monosaccharide residues?

    <p>2 to 10 (A)</p> Signup and view all the answers

    What distinguishes monosaccharides from other carbohydrates?

    <p>They cannot be further hydrolyzed (A)</p> Signup and view all the answers

    What sugars are produced from the hydrolysis of pectins?

    <p>Galactose, arabinose, and galacturonic acid (B)</p> Signup and view all the answers

    Which statement best describes the characteristics of glycoproteins?

    <p>They consist mainly of protein with a small amount of carbohydrates. (C)</p> Signup and view all the answers

    What role do glycosaminoglycans (GAGs) play in bodily secretions?

    <p>They enhance the viscosity and lubrication of mucous secretions. (A)</p> Signup and view all the answers

    What are the primary constituents of glycosaminoglycans (GAGs)?

    <p>95% carbohydrates and 5% proteins (A)</p> Signup and view all the answers

    Which polysaccharide is primarily used as a culture medium for growing bacteria?

    <p>Agar-agar (B)</p> Signup and view all the answers

    What type of polysaccharide acts as a reserve food and can be hydrolyzed to sugars for respiration?

    <p>Starch (C)</p> Signup and view all the answers

    Which of the following polysaccharides gives a blue color with iodine?

    <p>Starch (A)</p> Signup and view all the answers

    What is the primary structural function of cellulose in plants?

    <p>Providing rigidity and strength (D)</p> Signup and view all the answers

    What characteristic distinguishes glycogen from starch?

    <p>It is more branched with α(1→6) linkages. (B)</p> Signup and view all the answers

    What happens to cellulose during partial hydrolysis with acids?

    <p>It yields cellobiose. (A)</p> Signup and view all the answers

    Which of the following properties is NOT true about cellulose?

    <p>It is soluble in water. (D)</p> Signup and view all the answers

    Inulin serves primarily as what type of compound in dietary contexts?

    <p>A diagnostic marker (B)</p> Signup and view all the answers

    Which of the following describes dextrins?

    <p>They are used as adhesive in tablet preparations. (D)</p> Signup and view all the answers

    What is the molecular formula of trioses?

    <p>C3H6O3 (D)</p> Signup and view all the answers

    How are the carbon atoms in a monosaccharide numbered?

    <p>Starting from the aldehyde or ketone functional group (B)</p> Signup and view all the answers

    Which of the following statements about monosaccharides is correct?

    <p>Monosaccharides exhibit optical activity. (A)</p> Signup and view all the answers

    Which sugar derivative is formed by the reduction of a monosaccharide?

    <p>Sugar alcohols (A)</p> Signup and view all the answers

    What happens to the carbonyl carbon during the oxidation of a monosaccharide to form an aldonic acid?

    <p>It gets oxidized to a carboxylic group. (A)</p> Signup and view all the answers

    Which compound is produced by the oxidation of glucose to an aldaric acid?

    <p>Glucaric acid (B)</p> Signup and view all the answers

    Which form do most monosaccharides with five or more carbon atoms predominantly take?

    <p>Cyclic form (D)</p> Signup and view all the answers

    What type of sugar is deoxyribose classified as?

    <p>Deoxy sugar (B)</p> Signup and view all the answers

    Which property is not associated with monosaccharides?

    <p>Presence of more than six carbon atoms (D)</p> Signup and view all the answers

    Which of the following correctly identifies the bond type in maltose?

    <p>α(1→4) glycosidic bond (D)</p> Signup and view all the answers

    Which monosaccharide is known to be reduced into sorbitol?

    <p>Fructose (D)</p> Signup and view all the answers

    Galactonic acid is produced from which monosaccharide?

    <p>Galactose (D)</p> Signup and view all the answers

    Which component forms the glycosidic bond in disaccharides?

    <p>Hydroxyl group of anomeric carbon (A)</p> Signup and view all the answers

    What is the molecular formula for lactose?

    <p>C12H22O11 (A)</p> Signup and view all the answers

    Isomaltose is formed from which type of glycosidic bond?

    <p>α(1→6) (D)</p> Signup and view all the answers

    Which sugar is an example of an amino sugar found in chondroitin?

    <p>Galactosamine (B)</p> Signup and view all the answers

    Flashcards

    Cell Communication Definition

    Ways living cells in an organism communicate, either directly or through chemical signals (like neurotransmitters, hormones, and cAMP).

    Contact-Dependent Signaling

    Cells communicate by direct contact of surface molecules.

    Paracrine Signaling

    Signals affect nearby cells only.

    Autocrine Signaling

    Cells respond to molecules they produce themselves.

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    Endocrine Signaling

    Hormones from glands travel through the bloodstream to distant cells.

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    Intracellular Receptors

    Receptors inside the cell, for hydrophobic signaling molecules that can cross the membrane.

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    Cell Surface Receptors

    Receptors on the cell surface; for hydrophilic signaling molecules that can't cross the membrane.

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    Hydrophobic Molecules

    Molecules that can dissolve in fats and pass through cell membranes easily.

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    Uronic Acid

    A sugar acid formed by oxidizing the 6th carbon (last hydroxyl group) of an aldose, creating a carboxyl group.

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    Aldaric Acid

    Di-carboxylic acid formed by oxidizing both the carbonyl group (1st carbon) and the last hydroxyl group (6th carbon) of an aldose to carboxylic acids.

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    Deoxy Sugar

    A sugar where a hydroxyl group (OH) has been replaced by a hydrogen atom (H).

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    Amino Sugar

    A sugar where a hydroxyl group has been replaced by an amino (NH2) group.

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    Glycosidic Bond

    A covalent bond linking a carbohydrate molecule to another molecule, often another carbohydrate.

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    Maltose

    A disaccharide formed by two glucose molecules linked by an α(1→4) glycosidic bond.

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    Isomaltose

    A disaccharide formed by two glucose molecules linked by an α(1→6) glycosidic bond.

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    Lactose

    A disaccharide formed by one glucose and one galactose molecule linked by a β(1→4) glycosidic bond.

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    Trioses

    Simple sugars with 3 carbon atoms and the chemical formula C3H6O3. They are the smallest monosaccharides.

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    Dihydroxyacetone

    A triose with a ketone group, making it a ketose. Its structure features two hydroxyl groups (OH) attached to the carbon chain.

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    Numbering Carbons in Monosaccharides

    Carbon atoms in monosaccharides are numbered starting from the aldehyde group (for aldoses) or the ketone group (for ketoses).

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    Cyclic Structure of Monosaccharides

    Most monosaccharides with 5 or more carbons exist in a ring form where the aldehyde or ketone group reacts with an alcohol on the same sugar molecule.

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    Sugar Alcohols

    Produced by reducing the carbonyl group of a sugar to a hydroxyl group, resulting in a sugar alcohol.

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    Sugar Acids

    Sugars can be oxidized to form acids. Aldonic acids are formed by oxidizing the aldehyde group, while uronic acids are formed by oxidizing the last hydroxyl group.

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    Cellobiose

    A disaccharide composed of two glucose molecules linked by a β-(1→4) glycosidic bond. It is a product of partial hydrolysis of cellulose.

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    Polysaccharide

    A carbohydrate made up of long chains of repeating sugar units linked together by glycosidic bonds. They serve as energy storage or structural components.

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    Storage Polysaccharide

    Polysaccharides that are stored in organisms as energy reserves. Examples include starch, glycogen, and inulin.

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    Starch

    A major storage polysaccharide in plants, composed of two components: amylose (linear chains of glucose) and amylopectin (branched chains of glucose).

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    Glycogen

    A highly branched polysaccharide that serves as the primary energy storage molecule in animals. Similar to amylopectin but with more branches.

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    Cellulose

    A structural polysaccharide found in plant cell walls, comprised of long, straight chains of glucose molecules linked by β-(1→4) glycosidic bonds. It provides rigidity and strength to plants.

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    Inulin

    A polysaccharide composed entirely of fructose units. Found in some plants, it's used in diagnostic tests for kidney function.

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    What are the two main types of polysaccharides?

    Storage polysaccharides act as energy reserves for organisms, while structural polysaccharides provide structural support.

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    Heteropolysaccharide

    A complex carbohydrate made up of different types of sugar monomers. Examples include pectins, gum arabic, and agar-agar.

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    Pectins

    Structural polysaccharides found in fruits. They break down into galactose, arabinose, and galacturonic acid.

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    Gum Arabic

    A heteropolysaccharide containing galactose and glucuronic acid, often used as a food additive.

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    Agar-agar

    A polysaccharide made up of galactose, derived from seaweed. It's used as a culture medium for bacteria.

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    Glycoprotein

    A protein molecule with a small amount of carbohydrates attached. It plays important roles in immunity, cell recognition, and other biological processes.

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    Carbohydrate Definition

    Organic compounds composed of carbon, hydrogen, and oxygen, typically with the general formula Cn(H2O)n. They are polyhydroxy aldehydes or ketones, or compounds yielding them upon hydrolysis.

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    Function of Carbohydrates

    Carbohydrates serve as a primary energy source for the body, providing about 50% of its energy needs. They also contribute to the structure of cells and tissues, play a role in cellular signaling, and regulate intestinal movement.

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    Monosaccharides

    Simple sugars that cannot be broken down into simpler forms by hydrolysis. They serve as the building blocks for larger carbohydrates.

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    Disaccharides

    Carbohydrates composed of two monosaccharide units linked together. Examples include sucrose (table sugar) and lactose (milk sugar).

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    Study Notes

    Lecture 1: Cellular Communication

    • Cell communication is a process where living cells in an organism interact. This happens via direct contact or chemical signals.

    • Chemical signals are carried by neurotransmitters, hormones, or cyclic AMP.

    Modes of Cell Communication

    • Contact-dependent: Surface molecules on one cell bind to surface molecules on another. This requires direct membrane contact

    • Paracrine: Signaling molecules only affect target cells in the proximity of the signaling cell. Example: electrical signal transmission between nerve and muscle cells (neurotransmitters).

    • Autocrine: Cells respond to molecules they produce themselves. Examples include growth factors and prostaglandins, which often function in paracrine and autocrine signaling.

    • Endocrine: Hormones produced by an endocrine gland travel through the bloodstream and reach distant target cells

    Cell Communication Definition

    • Any way living cells in an organism communicate with each other, whether by direct contact or chemical signals.

    Types of Cell Communication

    • Autocrine: Signaling a cell to itself.

    • Paracrine: Signaling a neighboring cell.

    • Endocrine: Signaling a distant cell through the bloodstream.

    • Direct: Signaling a neighboring cell through a gap junction.

    Binding of Extracellular Signal Molecules to Receptors

    • Cell-surface receptors: Hydrophilic (water-soluble) signal molecules attach to these receptors on the exterior of the target cell's membrane.

    • Intracellular receptors: Hydrophobic (lipid-soluble) signal molecules pass through the membrane and bind to receptors inside the cell. These receptors are often located in the cytoplasm or the nucleus.

    Intracellular Receptors

    • Signaling molecules are hydrophobic, and can diffuse through the cell membrane.

    • Typically, polar molecules (e.g., hormones) cannot rapidly cross the cell membrane. Instead, they bind to a plasma membrane receptor.

    Cell Surface Receptors

    • Most signal molecules are hydrophilic, so they cannot pass through the cell membrane.

    • These bind to cell-surface receptors which then generate a signal inside of the target cell.

    Hormones

    • Hormones are chemicals that coordinate different functions in the body via carrying messages through the blood to organs, skin, muscles, and other tissues.

    Classification of Hormones

    • Group I (Lipophilic):
      • Steroids and thyroid hormones
      • Long half-life (hours to days)
      • Intracellular receptors
      • Receptor-hormone complex
    • Group II (Hydrophilic):
      • Amino acid derivatives
      • Short half-life (minutes)
      • Cell surface receptors
      • Second messengers (e.g., cAMP, Ca2+, etc.)

    Broad Classification of Hormones (by Structure)

    • Hydrophilic: Proteins, peptide hormones, catecholamines. Primarily act via second messengers
    • Lipophilic: Steroid and thyroid hormones. Primarily act by activating genes within the nucleus.

    Lipid-Soluble Hormones

    • Pass easily through the plasma membrane.
    • Have receptors inside the cell, in the cytoplasm
    • Binding to receptors activates enzymatic activity for changes in biochemical processes. Hormones like testosterone, progesterone, estrogen, cortisol, and thyroxine have receptors in the nucleus.

    Hydrophillic Hormones

    • Bind to specific receptor proteins on the cell surface of the target cells.
    • Do not enter the cytosol or nucleus.
    • Cell-surface receptors convert extracellular signals to intracellular signals.

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    Description

    Explore the fascinating world of cellular communication in this quiz. Learn about the different modes of communication including contact-dependent, paracrine, autocrine, and endocrine signaling mechanisms. Test your understanding of how cells interact and convey signals within an organism.

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