Chapter 3-Cellular Level of Organization.pdf - CHAPTER 3:...

CHAPTER 3: THE CELLULAR LEVEL OF
ORGANIZATION
Human Anatomy and Physiology I
Dr. Jenny Harper

THE CELL MEMBRANE
o The cell membrane or plasma membrane covers and protects every cell in our body
o The function of the plasma membrane is to act as a barrier and separate the
internal environment of the cell from the external environment outside the cell

STRUCTURE AND COMPOSITION OF THE CELL
MEMBRANE
• Phospholipid bilayer
• Phosphate “head”
• Lipid “tail”
• Hydrophobic and hydrophilic sides are
formed

PHOSPHOLIPID BILAYER
• Lipid tails of one layer face the lipid
tails of another layer
• Phospholipid heads face outwards from
each other on opposite ends

MEMBRANE PROTEINS
• Integral proteins
• Peripheral proteins

PASSIVE TRANSPORT
• Concentration gradients
• Diffusion

FACILITATED DIFFUSION
• Used for substances that cannot cross the
lipid bilayer due to their size, charge,
and/or polarity

OSMOSIS