Cell Structure and Genetic Control
• Basic unit of structure and function of the body.
▫ Highly organized molecular factory.
• Great diversity of function.
▫ Organ physiology derived from complex functions of
• 3 principal parts:
▫ Plasma membrane.
▫ Cytoplasm and organelles.
• Is selectively permeable.
▫ Double layer of phospholipids due to hydrophobic/hydrophilic
Restrict passage of H20 and H20 soluble ions.
▫ Proteins span or partially span the membrane.
Provide structural support, transport molecules, serve as receptors.
▫ Negatively charged carbohydrates attach to the outer
Involved with regulatory molecules.
Cytoplasm, Organelles, Nucleoli
▫ Aqueous content of the cell.
▫ Sub-cellular structures within the cytoplasm.
▫ Is a large spheroid body.
▫ Largest of the organelles.
▫ Contains the genetic material (DNA).
Centers for production of ribosomes.
▫ Phagocytic cells use pseudopods to surround and engulf particles.
▫ Pseudopods join, fuse, and surround ingested particle (food
Lysosomes digest food vacuole.
▫ Protects from invading organisms.
▫ Removes debris.
Plasma membrane invaginates, fuses, vesicle containing ECF pinches off,
and vesicle enters cell.
Bulk Transport (continued)
• Receptor-mediated endocytosis:
▫ Interaction of molecules in ECF with specific membrane receptor
▫ Membrane invaginates, fuses, pinches off and forms vesicle.
▫ Vesicle enters cell.
▫ Process by which cellular products are secreted into extracellular
▫ Proteins and other molecules to be secreted are packaged in vesicles
by Golgi complex.
▫ Vesicles fuse with plasma membrane and release contents into
Cilia, Flagella, Microvilli
▫ Tiny hair-like structures that project from the
surface of the cell.
Stroke in unison.
Respiratory tract, uterine tube.
▫ Simple whip-like structure that propels sperm
through its environment.
▫ Numerous folds (finger-like projections) increase
Cytoplasm and Cytoskeleton
▫ Jelly-like matrix within
▫ Includes organelles and
▫ Highly organized
function as cytoskeleton.
▫ Actin and myosin
▫ Spindle apparatus
Contain only digestive enzymes.
Primary lysosome fuses with food vacuole or organelle.
Contain partially digested remnants of other organelles and organic
▫ Residual body:
Contain undigested wastes.
Process that destroys worn-out organelles, so that they can be
▫ Apoptosis (programmed cell death):
Lysosomes release digestive enzymes into the cell.
• Membrane-enclosed organelles.
▫ Contain specific enzymes that promote
▫ Oxidize molecules and form H202.
• Catalase: converts H202 H20 + 02.
• Oxidation of toxic molecules by peroxisomes
is an important function of liver and kidney
• Sites for energy
production of all cells;
but mature RBCs.
• Contain own DNA, can
▫ Outer membrane: smooth.
▫ Inner membrane: cristae.
▫ Cristae and matrix
Have different roles in
• Protein factories:
▫ Proteins produced according to genetic information
contained in mRNA.
▫ Located in cytoplasm and on the surface of
• rRNA molecules serve as enzymes (ribozymes)
required for protein synthesis.
▫ Contains 2 subunits composed of rRNA and
Endoplasmic Reticulum (ER)
• Granular (rough) ER:
▫ Bears ribosomes on
surface, in cells active in
Proteins enter cisternae
are modified for secretion.
• Agranular (smooth) ER:
▫ Provides site for enzyme
reactions in steroid
hormone production and
▫ Storage of Ca2+
• Stacks of hollow, flattened
sacks with cisternae.
▫ One side of sack faces site for
entry of vesicles from ER that
contain cellular products.
▫ Other site faces towards
plasma membrane and
releases vesicles of chemically
• Modifies proteins, separates
according to destination, and
packages into vesicles.
Most cells have single nucleus.
Enclosed by inner and outer membrane
◦ Outer membrane is continuous with ER.
Nuclear pore complexes fuse inner and outer
◦ Selective active transport of proteins and RNA.
Regulation of gene expression.
Transport of mRNA out of nucleus to ribosomes.
◦ DNA contains the genes that code for the production
▫ Cells deprived of blood supply swell, the membrane
ruptures, and the cell bursts (necrosis).
▫ Cells shrink, membranes become bubbled, nuclei condense.
• Capsases (“executioner enzymes”):
▫ Mitochondria membranes become permeable to proteins
and other products.
• Programmed cell death:
▫ Physiological process responsible for remodeling of tissues
during embryonic development and tissue turnover in the