Cell Membrane Functions
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Questions and Answers

What is the primary factor that influences the rate of diffusion, according to Fick's Law?

  • Surface area of the membrane
  • Molecular weight of the substance
  • Lipid solubility of the substance
  • Concentration gradient of the substance (correct)

Which of the following is NOT a characteristic of unassisted membrane transport diffusion?

  • It only occurs if the substance can cross the membrane
  • It is a passive mechanism
  • It always moves from an area of high to low concentration
  • It requires energy input (correct)

What type of hormones can move into cells passively?

  • Amino acid hormones
  • Peptide hormones
  • Protein hormones
  • Steroid hormones (correct)

What is the term for the movement of water down its own concentration gradient through a semipermeable membrane?

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

What is the term for the difference in concentration of non-penetrating solutes between two solutions?

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

What is the formula for the rate of diffusion, according to Fick's Law?

<p>Rate = (SA x CG)/ TW (A)</p> Signup and view all the answers

What happens to a cell in a hypotonic solution?

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

What is the function of membrane-spanning proteins in carrier-mediated transport?

<p>To bind and transport specific substances (D)</p> Signup and view all the answers

What is the maximum rate of transport by a carrier protein?

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

Which type of transport involves the movement of a substance from high to low concentration?

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

What happens to the carrier protein after the solute molecule binds to it in facilitated diffusion?

<p>It changes conformation to release the solute (D)</p> Signup and view all the answers

What is the purpose of GLUT4 in adipose muscles?

<p>To facilitate glucose uptake (D)</p> Signup and view all the answers

What is the primary function of the cell membrane as a physical barrier?

<p>To separate the cell from its environment and prevent toxic waste buildup (A)</p> Signup and view all the answers

What is the main characteristic of the fluid mosaic model of the cell membrane?

<p>A fluid structure with a dynamic arrangement of proteins and lipids (D)</p> Signup and view all the answers

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

<p>To span the entire width of the membrane and function as self-identity markers (A)</p> Signup and view all the answers

What is the purpose of cholesterol in the cell membrane?

<p>To provide fluidity and stability to the membrane (A)</p> Signup and view all the answers

What is the function of glycoproteins in the cell membrane?

<p>To function as self-identity markers and help with cell differentiation (C)</p> Signup and view all the answers

What type of protein is aquaporin?

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

What is the function of cell adhesion molecules (CAMs) in the cell membrane?

<p>To help with the adhesion of cells to each other (D)</p> Signup and view all the answers

What is the term for the entire structure of cells, tissues, organs, and systems that make up an organism?

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

What is the term for the process of cells working together to provide signals on what needs to happen?

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

What is the function of the phospholipid bilayer in the cell membrane?

<p>To form a barrier that separates the cell from its environment (D)</p> Signup and view all the answers

What is the effect of acetylcholine binding to its receptor on the voltage-gated ion channel?

<p>It opens the channel, allowing Na+ flow in. (B)</p> Signup and view all the answers

What is the purpose of the Na+/K+ ATPase pump in generating the resting membrane potential?

<p>To pump 3 Na+ out and 2 K+ in. (A)</p> Signup and view all the answers

What is the equilibrium potential of K+ (Ek+)?

<p>-90 mV (D)</p> Signup and view all the answers

What is the general mechanism of second messenger pathways?

<p>The first messenger binds to a receptor, releasing a second messenger, which then relays the signal. (C)</p> Signup and view all the answers

What is the primary mechanism by which sodium ions are transported out of the blood?

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

What is the purpose of leak channels for Na and K ions?

<p>To passively allow diffusion down their concentration gradients. (D)</p> Signup and view all the answers

Which type of transport involves the movement of molecules down their concentration gradient?

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

Why is the equilibrium potential for Na+ lower than for K+?

<p>Because the concentration gradient for Na+ is smaller than for K+. (B)</p> Signup and view all the answers

What is the primary function of Na+/K+ ATPase in the kidney?

<p>To regulate the concentration of sodium ions outside the cell (B)</p> Signup and view all the answers

Which type of vesicular transport involves the non-selective uptake of extracellular fluid?

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

What is the primary function of exocytosis in the cell?

<p>To secrete neurotransmitters and hormones (A)</p> Signup and view all the answers

Which type of cell communication involves the direct contact of plasma membranes between cells?

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

What is the primary function of lipid-soluble chemical messengers in signal transduction?

<p>To cross the plasma membrane and affect gene transcription (A)</p> Signup and view all the answers

What is the primary function of ion channels in the cell?

<p>To allow ions to move into the cell and affect physiological responses (D)</p> Signup and view all the answers

Which type of ion channel is always open and allows for the leakage of ions into and out of the cell?

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

What is the primary function of ligand-gated ion channels in the cell?

<p>To open and close in response to stimuli (D)</p> Signup and view all the answers

Flashcards

Passive Transport

The movement of substances across a cell membrane without the use of energy, from a region of high concentration to a region of low concentration.

Facilitated Diffusion

A type of passive transport where substances move down their concentration gradient with the help of carrier proteins.

Osmosis

The movement of water molecules across a semi-permeable membrane from a region of high water concentration to a region of low water concentration.

Active Transport

The movement of substances across a cell membrane against their concentration gradient, requiring energy input.

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Carrier Protein

A protein that binds to specific substances and aids in their transport across the membrane in facilitated diffusion.

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Specificity

The ability of a carrier protein to bind only to specific substances.

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Saturation

The state where all carrier proteins are occupied by substances, preventing further transport.

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Competition

The competition between multiple substances for the same carrier protein.

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Fluid Mosaic Model

The dynamic and flexible structure of the cell membrane, characterized by a phospholipid bilayer with embedded proteins.

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Phospholipids

Amphipathic molecules that form the structural basis of the cell membrane, with a hydrophilic head and a hydrophobic tail.

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Cholesterol

A lipid molecule that helps maintain the fluidity and stability of the cell membrane.

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Carbohydrates

Sugar molecules attached to lipids or proteins on the cell membrane, functioning as cell recognition markers.

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Integral Proteins

Proteins embedded within the cell membrane, spanning its entire thickness.

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Peripheral Proteins

Proteins attached to one side of the cell membrane, without spanning its entire thickness.

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Aquaporins

Proteins that form channels in the cell membrane, allowing the passage of water molecules.

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Ion Channels

Proteins that form channels in the cell membrane, allowing the selective passage of specific ions.

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Second Messenger

Proteins that relay signals inside the cell following external stimulation.

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Membrane Potential

The difference in electrical charge across the cell membrane, with the inside being negatively charged relative to the outside.

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RMP

The resting membrane potential, typically around -70mV.

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Homeostasis

The process of maintaining stable internal conditions within a cell, despite external changes.

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Cell-Cell Adhesions

The specialized junctions between cells that help maintain the structure and function of tissues and organs.

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Extracellular Matrix (ECM)

The substance that surrounds cells and provides structural support, signaling cues, and adhesion points.

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Signaling Cascade

A signaling cascade triggered by a second messenger, amplifying the initial response.

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Cyclic AMP (cAMP)

A cyclic nucleotide molecule that acts as a second messenger, involved in various cellular processes.

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Ca2+/DAG Pathway

A signaling pathway involving calcium ions (Ca2+) and diacylglycerol (DAG), important in cell signaling.

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GLUT4

The specialized proteins that facilitate the movement of glucose into adipose and muscle cells.

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Insulin

A hormone that stimulates the insertion of GLUT4 proteins into the cell membrane, enhancing glucose uptake.

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Sodium-Potassium Pump (Na+/K+ ATPase)

A transport protein responsible for maintaining ion gradients across the cell membrane by pumping sodium out and potassium in.

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Study Notes

Passive Transport

  • Passive transport occurs without energy input, allowing substances to move from high to low concentration
  • Types of passive transport:
    • Diffusion: movement of substances from high to low concentration
    • Osmosis: movement of water molecules from high to low concentration

Facilitated Diffusion

  • Facilitated diffusion is a type of carrier-mediated transport
  • Carrier proteins bind to specific substances and transport them across the membrane
  • Characteristics:
    • Specificity: each carrier protein binds to specific substances
    • Saturation: finite number of carrier proteins, leading to saturation
    • Competition: multiple substances competing for same carrier protein
  • Examples:
    • GLUT4: facilitates glucose transport into adipose and muscle cells
    • Insulin stimulates GLUT4 insertion into cell membrane

Active Transport

  • Active transport moves substances from low to high concentration, requiring energy input
  • Examples:
    • Iodine uptake in thyroid gland cells
    • Sodium-potassium pump (Na+/K+ ATPase) maintains ion balance

Cell Membrane Structure

  • Fluid mosaic model: flexible and dynamic structure with integral and peripheral proteins
  • Components:
    • Phospholipids: amphipathic molecules forming bilateral layer
    • Cholesterol: maintains fluidity and stability
    • Carbohydrates: attached to lipids or proteins, functioning as identity markers
  • Functions:
    • Physical barrier
    • Homeostasis maintenance
    • Mechanical barrier
    • Adhesion between cells
    • Cell signaling

Membrane Proteins

  • Types:
    • Intrinsic (integral): spanning the membrane
    • Extrinsic (peripheral): attached to one side of the membrane
  • Functions:
    • Aquaporins: water channels
    • Ion channels: selective ion transport
    • Carrier molecules: facilitated diffusion
    • Receptors: binding specific molecules
    • Enzymes: performing physiological activities
    • Cell adhesion molecules (CAMs): adhering cells together

Cell-Cell Adhesions

  • Cell-cell adhesions form tissues, organs, and systems
  • Extracellular matrix (ECM) components:
    • Proteins
    • Polysaccharides
    • GAGs
  • Functions:
    • Adhesion
    • Signaling
    • Mechanical support

Second Messenger Pathways

  • Second messenger relays signals inside the cell
  • Amplifies initial response through a signaling cascade
  • Two major pathways:
    • Cyclic AMP
    • Ca2+/DAG

Membrane Potential

  • Plasma membrane is polarized electrically, with a potential difference across the membrane
  • Generation of RMP (-70mV) due to unequal distribution of Na+, K+, and anions
  • Membrane potential is the capacity to do work, measured in millivolts (mV)

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Learn about the crucial functions of the cell membrane, including its role as a physical barrier, maintaining homeostasis, and facilitating exchange of nutrients and wastes. Discover how it responds to environmental changes and signals, and how it knows when to produce an enzyme.

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