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Anatomy and Physiology
Ch. 3 Notes
Cells: the basic unit of an organism. 75 trillion cells is the ave. person
Differentiated: cells with specialized characteristics
Cells vary in size, shape, content and function. Therefore we use a composite
cell.
3 Major parts to a cell
1. Nucleus: innermost part of the cell—enclosed by a nuclear envelope.
Contains genetic material
2. Cytoplasm: mass of fluid that surrounds the nucleus. Enclosed by a plasma membrane
Cytoplasmic organelles: specialized structures within the cytoplasm
Cytosol: a liquid within the cytoplasm
3. Cell Membrane: the outermost limit of the cell. Metabolic reactions take place on the
surface.
General Characteristics p. 64
Selectively permeable: controlling the entrance and exit of materials. Letting some in
and excluding others.
The cell membrane is composed of lipids and proteins with some carbohydrate. Its
framework is a double layer of phospholipids molecules. Fig. 3.6
Table 3.1 p. 67
Intercellular Junctions: a connecting point for cell membranes
Tight junction: membranes of cells converge and fuse
Desmosome: spot welds -- reinforced structural unit
Gap junctions: interconnected tubular channels—link cytoplasm of other cells so
molecules can move b/w them.
p. 67-70 Cellular adhesion molecules (Splinter Story)
Cytoskeleton: protein rods and tubules that form a supportive framework.
Organelles within the cytoplasm:
1. Endoplasmic reticulum: membrane bound sacs, canals, and fluid filled vesicles.
They are interconnected and provide a transport system for molecules.
2. Ribosomes: composed of protein and RNA. Site of protein synthesis.
3. Golgi apparatus: a stack of 6 or so flattened membranous sacs called cisternae.
Refines, packages, and delivers proteins synthesized by the ribosomes.
4. Mitochondria: enlongated fluid filled sacs. Controls chemical reactions that release
glusoce and other organic nutrients. Transfers this newly released energy into a form that
cells can readily use called ATP. The powerhouse of the cell.
5. Lysosomes: The garbage disposals of the cell. They dismantle debris and destroy
worn cellular parts.
6. Peroxisomes: most abundant in the liver and kidneys. They contain enzymes that
catalyze metabolic reactions. P. 76 more functions
7. Centrosome: structure located in the cytoplasm near the nucleus.
They form spindle fibers that pull on and distribute chromosomes and form
hairlike cellular projections called cilia and flagella.
8. Cilia and Flagella: motile extensions of certain cells p. 76
9. Vesicles: membranous sacs that vary in size and contents. Transport substances into
and out of cells—vesicle trafficking
10. Microfilaments and microtubules: threadlike structures in the cytoplasm
Microfilaments: tiny rods of the protein actin that typically occurs in meshwork or
bundles. It causes cellular movements.
Microtubules: long slender tubes –larger than microfilaments—help distribute
chromosomes in newly forming cells
Cell Nucleus: a large spherical structure that contains the genetic material DNA and
directs the activities of the cell
Nuclear Envelope: an inner and outer layered bilipid membrane
Nuclear pores: openings in the membrane, channels made of different types of proteins
Structures within the Nucleus:
1. Nucleolus: a small dense body largely composed of RNA and protein. Site of
ribosome production.
2. Chromatin: loosely coiled fibers in the nuclear fluid p. 79
Table 3.3 Review
Movements in and out of the cell
Diffusion: the tendency to move from an area of higher concentration to an area of lower
concentration. To become more diffuse.
Concentration Gradient: the difference in concentrations
Diffusional equilibrium: a uniform concentration throughout a substance.
Fig 3.21
Facilitated Diffusion: diffusion which uses membrane proteins as helpers in movement.
Factors which influence diffusion rate: distance, concentration gradient, and temperature.
Compare and contrast simple diffusion to facilitated diffusion.
Osmosis: a special case of diffusion in which water molecules diffuse from higher conc.
to lower conc. through a selectively permeable membrane.
Osmotic pressure increases as the number of particles dissolved in a solution increases.
Isotonic: any solution that has the same osmotic pressure as body fluids.
Hypertonic: solutions that have a higher osmotic pressure than body fluids
Hypotonic: solutions that have a lower osmotic pressure than body fluids
Fig. 3.26
Filtration: molecules move through a membrane from regions of higher hydrostatic
pressure towards regions of lower hydrostatic pressure.
Ex. Blood pressure filters water and dissolved substances through porous capillary walls.
Fig. 3.27
Active Transport: moves molecules or ions from areas of low conc. to regions of high
concentration.
Requires cellular energy and carrier molecules in the cell membrane.
Fig. 3.29
Endocytosis: molecules or particles that are too large to enter a cell by diffusion or AT
are conveyed within a vesicle that forms from a secretion of the cell membrane. This
occurs 3 ways.
1. Pinocytosis: a cell membrane engulfs tiny droplets of liquid.
2. Phagosytosis: a cell membrane engulfs a solid
3. Receptor-mediated endocytosis: receptor proteins combine with specific molecules
in the cell suffoundings. The membrane engulfs the combinations.
Fig. 3.33
Exocytosis: the reverse of endocytosis Vesicles containing secretions fuse with the cell
membrane, releasing the substances to the outside.
Transcytosis: combines endocytosis and exocytosis. A substance or particle crosses a
cell using cellular energy.
Table 3.4 Review
The Cell Cycle: a series of changes that a cell undergoes from the time it forms until it
divides
Daughter cells: the 2 cells that are the product of division
1. Interphase: an active period in which the cell grows and maintains its routine
functions as well as its contributions to the internal environment.
Phases of Cell Division Fig. 3.36
Mitosis: A form of cell division that occurs in nonsex cells and produces 2 daughter cells
from an original. Genetically identical 46 chromosomes.
1. Prophase: Chromatin condenses into chromosomes, centrioles move to opposite
sides of cytoplasm, nuclar membrane and nucleous disperse, microtubules appear and
associate with centrioles and chromatids of chromosomes.
2. Metaphase: Spindle fibers from the centrioles attach to the centromeres o feach
chromosome. Chromosomes align midway b/w the centrioles.
3. Anaphase: Centromeres separate, and chromatids of the chromosomes separate,
spindle fibers shorten and pull these new ind. Chromosomes toward the centrioles
4. Telophase: Chromosomes elongate and form chromatin threads, nuclar membranes
appear around each chromosome set, nucleoli appear, microtubules break down.
Fig. 3.37 Review
Cytoplasmic Division: begins during anaphase when the cell membrane starts to
constrict around the middle, which it continues to do into telophase. The muscle like
contraction of the ring of actin microfilaments pinches off two cells from one.
Control of Cell Division:
How often a cell divides is strictly controlled and varies with cell type.
A physical basis for this mitotic clock is DNA at the tips of the chromosomes called
telomeres.
External controls of cell division include hormones and growth factors.
Space availability is another external factor that influences timing and rate of cell
division.
Tumor: too frequent mitoses produce abnormal growth or neoplasm which may form a
disorganized mass.
2 Types of Tumors
1. Benign: remains is place like a lump, eventually interfering with the function of
healthy tissue.
2. Malignant: cancerous—an invasive tumor which extends into healthy tissue and
spreads.
2 types of genes that cause cancer
1. Oncogenes: genes that activate other genes to increase the cell division rate
2. Tumor suppressor genes: normally hold mitosis in check—if they are removed or
inactivated. This leads to uncontrolled growth (cancer)
Environmental factors: p. 94
Stem Cell: