Cell Biology: Introduction to Cells
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Questions and Answers

What is the primary function of the cell membrane?

  • To store genetic information
  • To produce energy for the cell
  • To synthesize proteins for the cell
  • To regulate what enters and leaves the cell (correct)

    • Which of the following is NOT a characteristic of a cell?

  • Produces its own energy
  • Reproduces by division
  • Needs nutrition and oxygen
  • Can survive independently outside the body (correct)

    • What is the primary function of epithelial tissue?

  • To protect the body from external damage (correct)
  • To produce hormones and regulate metabolism
  • To transmit nerve impulses
  • To provide support and structure to the body

    • Which type of tissue is responsible for transmitting nerve impulses?

    <p>Nervous tissue</p> Signup and view all the answers

    What is the term for the group of cells with similar function?

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

    What is the term for the structure formed by two or more primary types of tissues?

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

    Which of the following cells do not reproduce by division?

    <p>Nerve cells</p> Signup and view all the answers

    What is the term for the process by which cells respond to their environment?

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

    What is the function of cholesterol in the lipid layer of the cell membrane?

    <p>To provide structural integrity to the lipid layer</p> Signup and view all the answers

    What type of proteins pass through the entire thickness of the cell membrane?

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

    Which of the following is NOT a function of integral proteins?

    <p>Helping in the diffusion of water-soluble substances</p> Signup and view all the answers

    What is the term for proteins that are partially embedded in the outer and inner surfaces of the cell membrane?

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

    What is the purpose of the lipid layer in the cell membrane?

    <p>To allow only fat-soluble substances to pass through</p> Signup and view all the answers

    What is the term for carbohydrate molecules attached to proteins in the cell membrane?

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

    Which of the following is an example of an integral protein?

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

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

    <p>To help in the diffusion of water-soluble substances</p> Signup and view all the answers

    What is the term for the arrangement of phospholipid molecules in the lipid layer of the cell membrane?

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

    What is the function of carrier proteins in the cell membrane?

    <p>To transport substances across the cell membrane</p> Signup and view all the answers

    What is the function of glycocalyx in cell membranes?

    <p>It helps in the tight fixation of cells with one another.</p> Signup and view all the answers

    How do carbohydrate molecules contribute to the selective permeability of the cell membrane?

    <p>They are negatively charged, preventing negatively charged substances from entering the cell.</p> Signup and view all the answers

    Which of the following is NOT a function of the cell membrane?

    <p>Synthesis of proteins.</p> Signup and view all the answers

    How does the cell membrane contribute to the exchange of gases?

    <p>It provides a surface area for gas exchange.</p> Signup and view all the answers

    Which of the following is NOT a function of carbohydrates in the cell membrane?

    <p>Facilitating the movement of water across the membrane.</p> Signup and view all the answers

    Which of these statements BEST describes the role of the cell membrane in maintaining the cell's shape and size?

    <p>The cell membrane provides a framework for the cytoskeleton, which supports the cell's shape.</p> Signup and view all the answers

    Which organ system is primarily responsible for digestion of food particles?

    <p>Digestive system</p> Signup and view all the answers

    What is the primary function of the respiratory system?

    <p>Supplying oxygen and removing carbon dioxide</p> Signup and view all the answers

    How are proteins, lipids, and carbohydrates proportionally composed in the cell membrane?

    <p>55% proteins, 40% lipids, 5% carbohydrates</p> Signup and view all the answers

    What structure of the cell membrane was first proposed by James F Danielli and Hugh Davson?

    <p>Danielli-Davson model</p> Signup and view all the answers

    Which model of the cell membrane proposed that proteins float in the lipid layer?

    <p>Fluid mosaic model</p> Signup and view all the answers

    What is the thickness range of the cell membrane mentioned in the content?

    <p>75 to 111Å</p> Signup and view all the answers

    What is the role of the endocrine system in the body?

    <p>Regulation and maintenance of normal life</p> Signup and view all the answers

    Which type of lipid is primarily found in the lipid layer of the cell membrane?

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

    What distinguishes the fluid mosaic model from the Danielli-Davson model?

    <p>Fluid nature of the membrane</p> Signup and view all the answers

    What are the two parts of the cell body?

    <p>Nucleus and cytoplasm</p> Signup and view all the answers

    Study Notes

    Introduction to Cells and Tissues

    • Cells are the fundamental units of life, essential for all living organisms.
    • Each cell requires nutrition and oxygen, produces energy, eliminates waste, maintains its environment, responds to invaders, and can reproduce, with exceptions like neurons.
    • Tissues consist of groups of similar cells and are classified into four primary types: muscle, nervous, epithelial, and connective tissues.

    Organs and Organ Systems

    • Organs are structures formed from two or more primary tissue types that perform specific functions.
    • Types of organs include tubular (hollow) organs and compact (parenchymal) organs.
    • Organ systems are groups of interconnected organs that work together for specific bodily functions, such as:
      • Digestive system: processes food.
      • Excretory system: removes waste.
      • Cardiovascular system: transports substances.
      • Respiratory system: exchanges gases.
      • Reproductive system: facilitates reproduction.
      • Endocrine system: regulates growth and bodily functions.
      • Musculoskeletal system: provides stability and movement.
      • Nervous system: controls activities and intellectual functions.

    Structure of the Cell

    • Every cell consists of a cell body, a nucleus, and surrounding cytoplasm, all encased by a cell membrane.

    Cell Membrane

    • The cell membrane, or plasma membrane, is a protective and semi-permeable barrier between extracellular fluid (ECF) and intracellular fluid (ICF).
    • Thickness ranges between 75 to 111Å.
    • Composed of 55% proteins, 40% lipids, and 5% carbohydrates.

    Models of Cell Membrane Structure

    • Danielli-Davson Model: Proposed a lipid "sandwich" covered with protein layers.
    • Unit Membrane Model: Replaced the previous model, indicating structured layers based on electron microscopy.
    • Fluid Mosaic Model: Current model recognizing a dynamic arrangement of proteins floating within a fluid lipid bilayer.

    Lipid Layer and Phospholipids

    • The lipid layer is bilayered, consisting mainly of phospholipids which have hydrophilic heads and hydrophobic tails.
    • Cholesterol is interspersed among phospholipids, maintaining membrane integrity and fluidity.
    • The lipid layer's semi-permeability allows fat-soluble substances (e.g., oxygen, carbon dioxide) to pass, while being impermeable to water-soluble substances (e.g., glucose).

    Protein Layers in the Cell Membrane

    • Composed of integral (transmembrane) proteins that span the membrane and peripheral proteins that are loosely associated.
    • Functions of proteins include:
      • Structural integrity, transport, and as channels for molecules.
      • Serving as receptors for hormones and neurotransmitters.
      • Acting as enzymes for metabolic reactions.

    Carbohydrates in the Cell Membrane

    • Carbohydrates form glycoproteins and glycolipids, contributing to the glycocalyx, a protective layer on the membrane.
    • Functions include:
      • Restrictions on negatively charged substances.
      • Facilitating cell adhesion and signaling through receptor functions.

    Functions of the Cell Membrane

    • Protective barrier safeguarding the cytoplasm and organelles.
    • Selectively permeable to certain substances, enabling nutrient absorption and waste excretion.
    • Facilitates gas exchange (oxygen and carbon dioxide).
    • Maintains the cell's shape and size.

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    Learn about the characteristics of cells, the basic units of life. Discover how cells obtain nutrition, produce energy, and maintain their environment.

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