Cell Structure and Components
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Questions and Answers

What is the main function of the Rough Endoplasmic Reticulum (RER)?

  • Storage of calcium ions
  • Synthesis of carbohydrates and lipids
  • Detoxification of medications and poisons
  • Protein secretion and modification (correct)

    • What is the difference between protein synthesis at ribosomes attached to the ER and those free in the cytoplasm?

  • Proteins synthesized at ER-bound ribosomes are for secretion, while those at free ribosomes are for internal use (correct)
  • Proteins synthesized at ER-bound ribosomes are synthesized faster, while those at free ribosomes are slower
  • Proteins synthesized at ER-bound ribosomes are for internal use, while those at free ribosomes are for secretion
  • Proteins synthesized at ER-bound ribosomes are modified, while those at free ribosomes are not

    • What is the function of the Smooth Endoplasmic Reticulum (SER)?

  • Detoxification of medications and poisons
  • Storage of calcium ions
  • Protein synthesis and modification
  • Synthesis of carbohydrates, lipids, and steroid hormones (correct)

    • What is the main function of the nuclear envelope?

    <p>To regulate the passage of ions, molecules, and RNA</p> Signup and view all the answers

    What is the function of the endomembrane system?

    <p>To modify, package, and transport lipids and proteins</p> Signup and view all the answers

    What is the characteristic feature of the Rough Endoplasmic Reticulum (RER)?

    <p>Presence of ribosomes attached to its surface</p> Signup and view all the answers

    What is the composition of chromatin?

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

    What is the difference between the Rough Endoplasmic Reticulum (RER) and the Smooth Endoplasmic Reticulum (SER)?

    <p>RER has ribosomes attached, while SER does not</p> Signup and view all the answers

    What is the function of the nucleolus?

    <p>To produce ribosomes</p> Signup and view all the answers

    What is the main function of the plasma membrane?

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

    What is the main component of cytosol?

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

    What is the function of the nuclear envelope?

    <p>Part of the endomembrane system, extends into the ER</p> Signup and view all the answers

    What is the main function of lysosomes?

    <p>Digestion and recycling of cellular waste</p> Signup and view all the answers

    What is the function of free ribosomes?

    <p>To synthesize enzymes that aid in the control of cell function</p> Signup and view all the answers

    What is the composition of the phospholipid bilayer in the plasma membrane?

    <p>Two layers of phospholipids with a lipid layer in between</p> Signup and view all the answers

    What is the difference between free and attached ribosomes?

    <p>Free ribosomes are found in the cytoplasm, while attached ribosomes are bound to the endoplasmic reticulum</p> Signup and view all the answers

    What is the role of proteins in the plasma membrane?

    <p>To allow substances to enter the cell</p> Signup and view all the answers

    What is the function of aquaporins in the plasma membrane?

    <p>To allow water molecules to freely cross the membrane</p> Signup and view all the answers

    What is the function of the endoplasmic reticulum?

    <p>To transport proteins for secretion</p> Signup and view all the answers

    What is the main function of the cytoplasm?

    <p>To aid in the control of cell function</p> Signup and view all the answers

    What is the main component of the nucleus?

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

    What type of proteins are embedded in both layers of the phospholipid bilayer?

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

    What type of molecules can pass through the plasma membrane easily?

    <p>Small lipid-soluble molecules</p> Signup and view all the answers

    What is the function of carbohydrates in the plasma membrane?

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

    What is the primary function of the Golgi complex?

    <p>To complete posttranslational modifications of proteins and package them for transport</p> Signup and view all the answers

    Where are lysosomes typically found in the body?

    <p>In all cells of the body, but particularly in white blood cells</p> Signup and view all the answers

    What is the main function of mitochondria in a cell?

    <p>To generate energy for the cell</p> Signup and view all the answers

    What is the process called when a lysosome breaks down parts of a cell?

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

    What is the main difference between the outer and inner membranes of a mitochondrion?

    <p>The outer membrane encloses the intermembrane space, while the inner membrane has many folds</p> Signup and view all the answers

    What is the process called when a vesicle fuses with the plasma membrane and releases its contents?

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

    What type of transport uses vesicles to move large molecules across the plasma membrane?

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

    Where are Golgi complexes typically located in a cell?

    <p>Near the nucleus</p> Signup and view all the answers

    What is the defining characteristic of active transport?

    <p>Movement of molecules from an area of lower to an area of higher concentration</p> Signup and view all the answers

    What is the purpose of the pumps involved in active transport?

    <p>To move sodium ions out of the cell and potassium ions into the cell</p> Signup and view all the answers

    What determines the direction of water diffusion during osmosis?

    <p>The concentration of solutes in the solution</p> Signup and view all the answers

    What is the term for a solution that has a lower concentration of solutes than the fluid inside the cell?

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

    What happens to cells when they are placed in a hypotonic solution?

    <p>They swell and eventually burst</p> Signup and view all the answers

    What is the term for a solution that has the same concentration of solutes as the fluid inside the cell?

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

    Which of the following is a type of passive transport?

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

    What is the term for the amount of solute in a solution?

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

    Study Notes

    Cell Structure and Components

    • Cells contain nucleoplasm, which lies inside the nucleus, and inclusions, which are metabolic by-products, storage forms of nutrients, and pigments.
    • Three main components of cells: plasma membrane, cytoplasm, and nucleus.

    Plasma Membrane

    • The plasma membrane is an outer membrane that separates the cell's interior from its surrounding environment.
    • It is composed of a phospholipid bilayer, proteins, and carbohydrates.
    • Phospholipid bilayer: a "sandwich" made of two layers of phospholipids, with polar phosphate molecules forming the top and bottom surfaces, and nonpolar lipid tails in between.
    • Proteins: scattered throughout the plasma membrane, play important roles in allowing substances to enter the cell, and come in different types (peripheral and integral proteins).
    • Carbohydrates: attached to lipids (glycolipids) and proteins (glycoproteins), form specialized sites on the cell surface for cell recognition.

    Plasma Membrane Functions

    • The plasma membrane isolates the interior of the cell from the external environment (physical barrier).
    • It allows only certain molecules and ions to enter and exit the cytoplasm freely (selectively permeable).
    • Small lipid-soluble molecules, such as oxygen and carbon dioxide, can pass through the membrane easily.
    • Water molecules can freely cross the membrane using protein channels called aquaporins.
    • Ions and large molecules cannot cross the membrane without direct assistance.

    Cytoplasm and Organelles

    • Cytoplasm includes the contents of a cell between the plasma membrane and the nuclear envelope.
    • It is a gel-like substance called cytosol, consisting of 70-80% water, and contains organelles and cytoskeleton.
    • Many metabolic reactions, including protein synthesis, take place in the cytoplasm.
    • Most organelles are surrounded by one or two lipid membranes, similar to the plasma membrane.

    Nucleus

    • The nucleus is a large organelle that may or may not be centrally located within the cytoplasm.
    • It is enveloped in a double membrane called the nuclear envelope, with nuclear pores that control the passage of ions, molecules, and RNA.
    • It stores genetic information as DNA organized into linear structures called chromosomes (chromatin).
    • Most nuclei contain at least one nucleolus, which consists of ribonucleic acid (RNA) and helps in producing ribosomes.

    Ribosomes

    • Ribosomes are organelles composed of proteins and RNA (nucleoproteins).
    • Protein synthesis occurs at the ribosomes.
    • Ribosomes exist as either free ribosomes in the cytoplasm or attached ribosomes to the membrane of the endoplasmic reticulum.
    • Free ribosomes synthesize proteins that aid in the control of cell function, while attached ribosomes synthesize proteins that have a different destination.

    Endomembrane System

    • The endomembrane system is a group of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins.
    • It includes the nuclear envelope, lysosomes, and vesicles, the endoplasmic reticulum, and Golgi apparatus.

    Endoplasmic Reticulum

    • The endoplasmic reticulum (ER) is a series of interconnected membranous tubules that extend from the surface of the nucleus throughout most of the cytoplasm.
    • ER is a major site for vital cellular activities, including biosynthesis of proteins and lipids.
    • There are two types of ER: rough ER (RER) and smooth ER (SER).
    • RER has ribosomes attached to its cytoplasmic surface and is specialized for protein secretion.
    • SER lacks bound ribosomes and is involved in the synthesis of carbohydrates, lipids, and steroid hormones, as well as detoxification and storage of calcium ions.

    Golgi Complex

    • The Golgi complex is located near the nucleus and consists of many smooth membranous saccules that contain enzymes and proteins being processed.
    • The Golgi complex completes posttranslational modifications of proteins produced in the RER and then packages and addresses these proteins to their proper destinations.

    Lysosomes

    • Lysosomes are membranous sacs produced by the Golgi apparatus that contain hydrolytic enzymes.
    • They are found in all cells of the body but are particularly numerous in white blood cells that engulf disease-causing microbes.
    • Lysosomes break down engulfed substances and recycle cellular waste.

    Mitochondria

    • Mitochondria are oval-shaped, double-membrane organelles that are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule.
    • They are abundant in cells or cytoplasmic regions where large amounts of energy are expended.

    Mechanisms of Transport across the Plasma Membrane

    • Bulk transport (vesicular transport): uses vesicles to move large molecules across the membrane, including exocytosis and endocytosis.
    • Exocytosis: a process where a vesicle fuses with the plasma membrane, releasing its contents outside the cell.
    • Active transport: a process that requires a protein carrier and energy to move materials into the cell against the concentration gradient.
    • Osmosis: a special case of diffusion, where water moves across a selectively permeable membrane from an area of high concentration to an area of low concentration.
    • Tonicity: a measure of the concentration of solutes in a solution, which determines the direction of water diffusion.

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    Description

    This quiz covers the main components of cells, including the plasma membrane, cytoplasm, and nucleus. Learn about the functions and characteristics of each component.

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