UNIT TWO COMPREHENSIVE

Study Guide: Key Questions from Chapters 7, 11, 45, 48, 49, and 50

Chapter 7: Membranes

• Functions of Membrane Proteins:

  • Transport, enzymes, signal transduction, cell recognition, intercellular joining, attachment to the cytoskeleton.

• Molecule Diffusion Prediction:

  • Consider molecular size, polarity, and charge to predict diffusion through the lipid bilayer versus requiring transport mechanisms.

• Semipermeable Membrane Concept:

  • Cell membranes allow selective passage of substances; some can pass freely, while others cannot.

• Prediction of Solute Net Diffusion:

  • Solute tends to move from a region of high concentration to a region of low concentration until equilibrium is reached.

• Prediction of Water Net Diffusion (Osmosis):

  • Water moves toward areas of higher solute concentration through a semipermeable membrane.

• Tonicity:

  • Hypertonic: Cells lose water, shrink.

  • Isotonic: No net movement of water, cells remain the same size.

  • Hypotonic: Cells gain water, swell.

• Passive vs. Active Transport:

  • Passive transport requires no energy (moves down concentration gradient).

  • Active transport uses energy (ATP) to move substances against their concentration gradient.

• Facilitated Diffusion by Membrane Proteins:

  • Transporters and channels assist in transporting polar molecules across the membrane without energy.

• Sodium-Potassium Pump:

  • Moves Na+ out and K+ into the cell; crucial for maintaining resting membrane potential and requires ATP.

• Exocytosis vs. Endocytosis:

  • Exocytosis: secretion of substances from the cell.

  • Endocytosis: uptake of materials into the cell; involves membrane invagination.

Chapter 11: Cellular Communication

• Reasons for Cell Signaling:

  • To respond to environmental changes, coordinate functions, and communicate between cells.

• Types of Signaling:

  • Paracrine: signals act on nearby cells.

  • Synaptic: signals transmitted across a synaptic cleft between neurons.

  • Endocrine: signals (hormones) travel through the bloodstream to distant targets.

• Stages of Cell Signaling:

  • Reception: binding of signaling molecules to receptors.

  • Transduction: conversion of the signal to a form that can bring about a cellular response.

  • Response: cellular actions activated by the transduced signal.

• Role of Transmembrane Proteins:

  • Receptors that transmit signals from the extracellular environment to the inside of the cell.

• Signal Transduction Purpose:

  • To amplify and relay the signal to elicit a specific cellular response.

• Examples of Cellular Responses:

  • Changes in gene expression, enzyme activity, or cell behavior.

Chapter 45: Hormones and the Endocrine System

• Stages of Cell Signaling in Endocrine System:

  • Reception, transduction, response define how hormones interact with cells.

• Hormones:

  • Chemical messengers that regulate physiological processes.

• Water vs. Lipid-soluble Hormones:

  • Water-soluble hormones bind to receptors on the cell surface; lipid-soluble hormones pass through the membrane to interact with internal receptors.

• Hormone Production Organs:

  • Endocrine glands (e.g., pituitary, thyroid, adrenals).

• Neurosecretory Cells and Neurohormones:

  • Neurons that release hormones into the bloodstream, coordinating nervous and hormonal signals in the hypothalamus.

• Positive vs. Negative Feedback:

  • Positive feedback amplifies a response; negative feedback reduces it to maintain homeostasis.

• Negative Feedback Examples:

  • Regulation of blood glucose levels, body temperature control.

• Tropic vs. Non-tropic Hormones:

  • Tropic hormones act on other endocrine glands; non-tropic hormones directly affect target tissues.

Chapter 48: Neurons

• Neuron Structure and Function:

  • Dendrites receive signals, axons transmit impulses, synaptic terminals communicate with other cells.

• Cell Membrane Potential:

  • Difference in charge across the membrane, crucial for nerve signal conduction.

• Sodium/Potassium Pump Role:

  • Maintains resting potential by pumping Na+ out and K+ in.

• Leak Channels:

  • Allow passive ion movement, contributing to resting potential.

• Ligand-Gated Ion Channels:

  • Open in response to binding molecules and contribute to graded potentials.

• Excitatory vs. Inhibitory Stimuli:

  • Excitatory (depolarizing) stimuli increase membrane potential; inhibitory (hyperpolarizing) stimuli decrease it.

• Voltage-Gated Ion Channels:

  • Open in response to membrane potential changes, crucial for action potentials.

• Action Potential Generation:

  • Sequence involves depolarization, repolarization, and hyperpolarization phases.

• Membrane Potential Graph Interpretation:

  • Recognize resting potential, graded potentials, and action potentials on a graph.

Chapter 49: The Nervous System

• Core Functions of the Nervous System:

  • Input (gathering information), integration (processing data), output (responding).

• CNS and PNS Overview:

  • Central Nervous System: brain and spinal cord; Peripheral Nervous System: nerves outside the CNS.

• Parasympathetic vs. Sympathetic Nervous System:

  • Parasympathetic: rest and digest; Sympathetic: fight or flight responses.

Chapter 50: The Senses

• Components of the Sensory System:

  • Reception (detecting stimuli), Transduction (converting stimuli into signals), Transmission (sending signals), Perception (interpretation)

  • Related terms: Amplification (increasing signal strength) and Adaptation (diminished response to constant stimulus).

• Sensory Receptor Cells:

  • Specialized cells that detect and transduce sensory stimuli.

• Stimulus Intensity and Action Potential Frequency:

  • Higher intensity leads to increased frequency of action potentials.

• Various Receptor Types:

  • Photoreceptors (light), mechanoreceptors (pressure), thermoreceptors (temperature), chemoreceptors (chemical stimuli)