Bio 168 Chapter 3 Part 1

Cell Theory

The cell is the basic structural and functional unit of life

Organismal activity

Depends on individual and collective activity of cells

Biochemical activities

Dictated by subcellular structure (principle of complementarity)

Continuity of life

Has a cellular basis

Cell shape

Reflects its function

Carbon, hydrogen, oxygen, nitrogen

Main elements in all cells

Generalized cell

Refers to all cells with same basic parts and common functions

Plasma membrane

Separates intracellular fluids from extracellular fluids

Fluid Mosaic Model

Double bilayer of lipids with imbedded, dispersed proteins

Phospholipids

Composed of a hydrophilic head and two hydrophobic tails

Cholesterol

Stabilizes and decreases the fluidity of the membrane

Membrane Proteins

Responsible for most specialized functions of the plasma membrane

Glycocalyx

Composed of proteins with branching sugar groups

Membrane Junctions

Function in securing cells together

Tight Junction

Form impermeable junctions between cells

Desmosome

Anchor cells together and distribute tension

Gap Junction

Allow small molecules to pass from cell to cell

Selective Permeability

Plasma membrane allows some materials to pass while excluding others

Membrane Transport

Movement of substances into and out of the cell

Passive Processes

No energy is required for transport

Diffusion

Movement of molecules from high to low concentration

Simple Diffusion

Unassisted movement of lipid-soluble materials or small molecules

Facilitated Diffusion

Requires protein carrier or channel for transport

Osmosis

Simple diffusion of water across a membrane

Tonicity

Ability of a solution to cause a cell to change shape

Isotonic

Solution with same solute concentration as cytosol

Hypertonic

Solution with greater solute concentration than cytosol

Hypotonic

Solution with lesser solute concentration than cytosol

Active Processes

Require ATP to move substances across the membrane

Active Transport

Moves solutes against concentration gradient

Primary Active Transport

Requires energy directly from ATP hydrolysis

Secondary Active Transport

Requires energy indirectly from ionic gradients

Vesicular Transport

Transport of large particles and fluids in vesicles

Exocytosis

Transport out of the cell

Endocytosis

Transport into the cell

Phagocytosis

Engulfing solids into cell's interior

Pinocytosis

Bringing extracellular fluid and solutes inside cell

Receptor-mediated endocytosis

Selective endocytosis and transcytosis

Cell Adhesion Molecules (CAMs)

Anchor cells to each other and molecules in extracellular space

Plasma Membrane Receptors

Integral proteins and glycoproteins that serve as binding sites

Chemical Signaling

Ligands bind to plasma membrane receptors

Cell Response to Ligands

Activated enzymes, ion gate opening or closing, second messengers

G Protein Linked Receptors

Activate membrane-bound enzymes or ion channels

Resting Membrane Potential (RMP)

Voltage across a membrane in all cells

Selective Diffusion

Establishes electrochemical gradient

Active Transport

Maintains electrochemical gradients