Cell Structure – More Detail
Cellular Biology: A Refresher
Anatomy and Physiology 121:
Dr. Jaeson T. Fournier
Cell Structure – More Detail
Compartmentalization
 Compartmentalization
is an important
concept relative to the
study of biology.
 Biological activities
typically occur in
defined locales – i.e.
separating one
environment from
another.
Examples of
Body Compartments
Unique to Human?
Compartmentalization - Unique
Not unique to humans
Compartmentalization:
Anatomical vs.
Physiological
Compartmentalization
Biological Exchange
 Diffusion = the overall (net) movement of
molecules from an area where they are more
concentrate to an area where they are less
concentrated.
– Example: Drop of dye spreading throughout the
water cup
Biological Exchange
 Why does diffusion occur?
– All molecules in the universe are in constant
motion.
– In gases (more widespread) molecules move
rapidly and unrestricted; in liquids it move
more slowly because molecules are closer. It is
slowest in solids, because molecules are the
closest.
– Molecules move because of their own energy
and as a result of being hit by other molecules.
Biological Exchange
 Movement of Molecules
– Is usually random and due to their own energy
or being hit by another molecule.
– Diffusion though is not random, as molecules
also like to be in equilibrium and will move
from an area of high concentration to an area of
lower concentration.
Biological Exchange
 Gradient = the difference in concentration of a
substance from one area to another
 Diffusion = net movement of a substance down its
own concentration gradient
Biological Exchange
Biological Exchange
 Differentially Permeable Barrier
– A membrane that surrounds every cell
– Membranes act as a selective barrier that
controls the movement of materials in an out of
cells.
– This means that some molecules to enter a cell
and others do not.
• Water, oxygen, carbon dioxide crosses easily.
• Large molecules do not and usually need assistance.
Biological Exchange
 Osmosis = diffusion of water across
differentially permeable membranes.
Biological Exchange
 Diffusion is a slow process
 Any organism that is visible to the naked
eye (such as a human) relies on diffusion
only.
Levels Of Structural
Organization in the Human Body:
 Tissue = Group of cells with similar
structure and function.
– 4 types of tissue in the human body
• Epithelial, Muscle, Connective, Nervous Tissue
Levels Of Structural
Organization in the Human Body:
 Epithelial Tissue
– Covers external and internal body surfaces
• Examples
– Skin; alimentary canal
• Function
– Protect the body’s surfaces and produce secretions such as
sweat and mucus
Levels Of Structural
Organization in the Human Body:
Levels Of Structural
Organization in the Human Body:
 Connective Tissue
– Found throughout the entire body
– Secretes nonliving material that forms a matrix
(which may be solid or liquid)
• Examples
– Blood; Bone
• Function
– Connects, supports and protects body structures
Levels Of Structural
Organization in the Human Body:
Levels Of Structural
Organization in the Human Body:
 Nerve Tissue
– Made up of nerve cells (neurons)
• Examples
– Brain; spinal cord
• Function
– Specialized to transmit an electrical signal from one part
of the body to another
Levels Of Structural
Organization in the Human Body:
Levels Of Structural
Organization in the Human Body:
 Muscle Tissue
– Consists of cells that are able to contract in
response to stimulation (electrical)
• Examples:
– Skeletal; Smooth and Cardiac – actually these are the
types of muscle tissue
• Function
– Gives shape and support to the body and produces heat.
– Body motion (segmentally and as a whole)
Levels Of Structural
Organization in the Human Body:
Levels Of Structural
Organization in the Human Body:
 Organ
– Group of tissues organized together to form a
structural and functional unit.
– Every organ consists of all 4 basic tissue types.
– Examples
• Stomach, heart, kidney