Cell Structure and Membrane Transport

Cell theory

A cell is the structural and functional unit of life; the entire organism's function depends on the activities of its cells; structure and function are complementary; biochemical functions are dictated by cell shape and subcellular structures

Integral proteins

Proteins with hydrophobic and hydrophilic regions; interact with lipid tails and water; function in cell communication, specialized membrane functions

Peripheral proteins

Loosely attached to integral proteins; serve as identification markers, receptors for molecule recognition; part of cell junctions

Passive transport

Requires no energy; includes diffusion (simple, facilitated, osmosis) and filtration

Diffusion

Movement of molecules from high to low concentration; includes simple diffusion, facilitated diffusion, and osmosis

Facilitated diffusion

Passive transport of specific molecules down their concentration gradient using carrier or channel proteins

Osmosis

Passive movement of water through a semipermeable membrane from low solute to high solute concentration

Tonicity

Ability of a solution to change cell shape by altering internal water volume based on osmolarity

Primary active transport

Shape change of proteins pumps solutes across the membrane using ATP; e.g., Na+-K+ pump

Exocytosis

Vesicle merges with plasma membrane to release substances out of the cell; involves secretion of various substances

Cytology

The study of cells

Cells

The living units

Cell diversity

There are over 200 different types of human cells that differ in size, shape, subcellular components, leading to functional differences

Generalized cell

All cells share common structures and functions; human cells have three basic parts

Plasma membrane

Acts as a barrier, provides cell identity markers, controls cellular activity, site of chemical reactions; consists of lipids forming a flexible structure; contains membrane proteins with specialized functions

Cell junctions

Ways cells bind together: tight junctions, desmosomes, gap junctions

Active transport

Requires ATP to move solutes across a membrane against their concentration gradient; includes primary, secondary, and vesicular transport

Secondary active transport

Depends on ion gradients created by primary transport; transports other molecules along with ions

Endocytosis

Cell membrane surrounds and brings substances into the cell; includes phagocytosis (solids) and pinocytosis (liquids)