2: Cells and Membrane Transport
- Page ID
- 90492
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 2.1: Inorganic Chemistry Overview
- The ultra brief overview of inorganic chemistry covers the structure of atoms, including protons, neutrons, and electrons, and how their number and arrangement determine atomic charge, mass, and elemental identity. These principles explain the organization of the periodic table and form the chemical foundation for all biological structure and function.
- 2.2: Organic Chemistry Review
- Organic chemistry deals only with carbon-based molecules that form the chemical foundation: carbohydrates, lipids, proteins, and nucleic acids. It emphasizes how carbon bonding and molecular structure determine the function of these biologically essential compounds.
- 2.3: Cell Anatomy — Introduction
- Cells are the basic units of life, forming tissues, organs, and organ systems that together make up an organism, from single-celled bacteria to humans with trillions of cells. Differences in cell structure, organization, and specialization explain how complex bodies develop from a single cell and how form is closely tied to function.
- 2.4: Components of Plasma Membranes
- The plasma membrane is a flexible, selectively permeable barrier that protects the cell while controlling the movement of substances in and out. Embedded proteins enable transport, cell signaling, and cell recognition, allowing cells to communicate, maintain shape, and function together in tissues.
- 2.5: The Nucleus
- The nucleus houses and protects DNA, organizing it as chromatin during normal cell activity and as tightly packed chromosomes during cell division. It also contains the nucleolus, where ribosomes are assembled, linking the genetic information in DNA to the production of proteins that keep the cell functioning.
- 2.6: The Cytoplasm and Cellular Organelles
- Beyond the cell membrane, eukaryotic cells contain a cytoplasm filled with cytosol, where many biochemical reactions take place. Within this internal space are a nucleus and specialized organelles that carry out specific cellular functions.
- 2.7: Cytoskeleton and Cell Extensions
- The cytoskeleton is a dynamic network of protein fibers that supports cell shape, enables movement, organizes internal structures, and helps transport materials. Its three main components — microtubules, intermediate filaments, and microfilaments — work together to provide strength, flexibility, and coordinated motion within the cell.
- 2.8: Stem Cells and Cellular Differentiation
- A complex organism develops from a single fertilized egg through cellular differentiation, in which unspecialized cells become specialized in structure and function. Stem cells play a central role in this process by retaining the ability to divide and differentiate into multiple cell types.
- 2.9: Cell Physiology — Body Fluids and Fluid Compartment
- Cell physiology examines how cells carry out essential life processes, including metabolism, transport, communication, and energy use. It emphasizes the role of water, solutes, and fluid compartments, and how ion balance and membrane transport maintain normal cellular and body function.
- 2.10: Passive Movements across the Cell Membrane — Simple Diffusion
- Diffusion is a passive process in which molecules move from areas of higher concentration to lower concentration until equilibrium is reached. In cells, diffusion allows substances like gases and small solutes to cross membranes without energy, and its rate depends on factors such as concentration gradients, temperature, molecule size, and membrane properties.
- 2.11: Passive Movements across the Cell Membrane — Facilitated Diffusion and Osmosis
- Facilitated diffusion is a passive process in which larger, polar, or charged molecules move down their concentration gradient with the help of specific channel or carrier proteins. Osmosis is a specialized form of passive transport in which water moves across a selectively permeable membrane toward areas of higher solute concentration, helping maintain proper cell volume and fluid balance.
- 2.12: Tonicity
- Tonicity describes how the solute concentration of the surrounding fluid influences water movement into or out of a cell, thereby affecting cell volume. Hypotonic, isotonic, and hypertonic solutions determine whether a cell swells, shrinks, or remains stable based on osmotic balance.
- 2.13: Primary Active Transport — Pumps
- Primary active transport uses energy from ATP to move ions against their concentration gradients across the cell membrane. The sodium–potassium pump is the key example, maintaining unequal Na⁺ and K⁺ distributions that are essential for cell volume control, electrical signaling, and many downstream cellular processes.
- 2.14: Vesicular Transport — Endocytosis and Exocytosis
- Vesicular transport, finally, is an energy-requiring process that moves large materials into or out of cells using membrane-bound vesicles. Through endocytosis and exocytosis, cells can selectively engulf substances, recycle membrane, and release products such as enzymes, hormones, and signaling molecules essential for normal function.