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Boundless Anatomy and Physiology
Physiology Textbooks Boundless Anatomy and Physiology
Physiology Textbooks
Physiology

Chapter 3

Organization at the Cellular Level

Book Version 29
By Boundless
Boundless Anatomy and Physiology
Physiology
by Boundless
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Section 1
Introduction to the Study of Cells
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Cells as the Basic Unit of Life

A cell is the smallest unit of a living thing and is the basic building block of all organisms.

Section 2
Cell Membranes and the Fluid Mosaic Model
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Components of Plasma Membranes

The plasma membrane protects the cell from its external environment, mediates cellular transport, and transmits cellular signals.

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Fluid Mosaic Model

The fluid mosaic model describes the plasma membrane structure as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates.

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Membrane Fluidity

The mosaic nature of the membrane, its phospholipid chemistry, and the presence of cholesterol contribute to membrane fluidity.

Section 3
Transport Across Membranes
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Diffusion

Diffusion is a process of passive transport in which molecules move from an area of higher concentration to one of lower concentration.

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Osmosis

Osmosis is the movement of water across a membrane from an area of low solute concentration to an area of high solute concentration.

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Tonicity

Tonicity, which is directly related to the osmolarity of a solution, affects osmosis by determining the direction of water flow.

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Facilitated transport

Facilitated diffusion is a process by which molecules are transported across the plasma membrane with the help of membrane proteins.

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The Role of Passive Transport

Passive transport, such as diffusion and osmosis, moves materials of small molecular weight across membranes.

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Primary Active Transport

The sodium-potassium pump maintains the electrochemical gradient of living cells by moving sodium in and potassium out of the cell.

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Electrochemical Gradient

To move substances against the membrane's electrochemical gradient, the cell utilizes active transport, which requires energy from ATP.

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Secondary Active Transport

In secondary active transport, a molecule is moved down its electrochemical gradient as another is moved up its concentration gradient.

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Endocytosis

Endocytosis takes up particles into the cell by invaginating the cell membrane, resulting in the release of the material inside of the cell.

Section 4
Cell Signaling
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Types of Receptors

Receptors, either intracellular or cell-surface, bind to specific ligands, which activate numerous cellular processes.

Section 5
The Nucleus and Ribosomes
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The Nucleus and Ribosomes

Found within eukaryotic cells, the nucleus contains the genetic material that determines the entire structure and function of that cell.

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Characteristics of Eukaryotic Cells

A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow for compartmentalization of functions.

Section 6
Organelles
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The Plasma Membrane and the Cytoplasm

The plasma membrane is made up of a phospholipid bilayer that regulates the concentration of substances that can permeate a cell.

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The Endoplasmic Reticulum

The endoplasmic reticulum is an organelle that is responsible for the synthesis of lipids and the modification of proteins.

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The Golgi Apparatus

The Golgi apparatus sorts and packages materials before they leave the cell to ensure they arrive at the proper destination.

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Lysosomes

Lysosomes are organelles that digest macromolecules, repair cell membranes, and respond to foreign substances entering the cell.

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Peroxisomes

Peroxisomes neutralize harmful toxins and carry out lipid metabolism and oxidation reactions that break down fatty acids and amino acids.

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Mitochondria

Mitochondria are organelles that are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule.

Section 7
The Cytoskeleton
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Intermediate Filaments and Microtubules

Microtubules are part of the cell's cytoskeleton, helping the cell resist compression, move vesicles, and separate chromosomes at mitosis.

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Microfilaments

Microfilaments, which are the thinnest part of the cytoskeleton, are used to give shape to the cell and support all of its internal parts.

Section 8
External Cellular Components
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Extracellular Matrix of Animal Cells

The extracellular matrix of animal cells holds cells together to form a tissue and allow tissues to communicate with each other.

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Intercellular Junctions

Intercellular junctions provide plant and animal cells with the ability to communicate through direct contact.

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Boundless Anatomy and Physiology by Boundless
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Chapter 2
The Chemical Building Blocks of Life
  • Atomic Structure
  • Chemical Bonds
  • Inorganic Compounds
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Chapter 3
Organization at the Cellular Level
  • Introduction to the Study of Cells
  • Cell Membranes and the Fluid Mosaic Model
  • Transport Across Membranes
  • Cell Signaling
  • The Nucleus and Ribosomes
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Chapter 4
Organization at the Tissue Level
  • Introduction to Tissues
  • Epithelial Tissue
  • Connective Tissue
  • Nervous Tissue
  • Muscular Tissue
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