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Chapter 3

Chapter Notes for Chapter 3 of Human Physiology 5e

Biological Sciences
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Human Physiology (Fifth Edition)
Silverthorn, D. U.
Chapter 3 Compartmentation: Cells and Tissues
Advantages: compartments separate biochemical processes that might
otherwise conflict with one another; barriers allow contents within
compartments to differ from adjacent ones
Disadvantages: barriers can make it difficult to move needed materials from
one compartment to another
Functional Compartments of the Body
The body has 3 major body cavities
oCranial cavity (skull): contain the brain
oThoracic cavity (thorax): bounded by spine and ribs, surrounds the heart
oAbdominopelvic cavity: surrounds the organs in the abdomen and the
pelvis (stomach, spleen, urinary bladder, etc.)
Lumens of Some Organs Are Outside the Body
oLumen: the interior of any hollow organ; may be wholly or partially
filled with air or fluid; essentially, an extension of the external
environment, material in the lumen is not part of the bodys internal
environment until it crosses the wall of that particular organ (hole in bead
Functionally, the Body has Three Fluid Compartments
oIntracellular fluid, plasma, interstitial fluid (plasma, interstitial =
extracellular fluid)
Biological Membranes
all membranes have a uniform thickness of about 8 nm
two meanings of membranes: 1. Tissue, 2. Phospholipid-protein boundary
The Cell Membrane Separates the Cell from its Environment
oCell membrane = plasma membrane = plasmalemma
oFunctions of the cell membrane:
1. Physical isolation: physical barrier separating intracellular and
extracellular fluid
2. Regulation of exchange with the environment: controls entry of
ions and nutrients, elimination of cell wastes, and product releases
3. Communication between the cell and its environment: contains
proteins that enable cell to react to its external environment
4. Structural support: proteins in the membrane hold cytoskeleton
in place to maintain cell shape
Membranes are Mostly Lipid and Protein
oMembranes also contain a small amount of carbs
oProtein-lipid ratio varies depending on membrane source; in general, the
more metabolically active a membrane is, the more proteins it contains

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oFluid-mosaic model: phospholipids are arranged in a bilayer, membrane is
studded with proteins, and the extracellular surface has glycoproteins and
Membrane Lipids Form a Barrier Between the Cytoplasm and
Extracellular Fluid
o3 main types of lipids in membrane:
Phospholipid: glycerol backbone with two fatty acid chains and a
phosphate group
Sphingolipid: fatty acid tails, phospholipid or glycolipid head,
slightly longer than phospholipid
Cholesterol: helps make membranes impermeable to small water-
soluble molecules and keeps membranes flexible
Membrane Proteins May Be Loosely or Tightly Bound to the
o3 types of membrane proteins:
Integral proteins: extend all the way across the cell membrane,
tightly bound, the only way to remove these is by disrupting the
membrane structure with detergents or other harsh methods
Peripheral proteins: attached loosely to integral proteins or to
phospholipid heads, can be removed without disrupting membrane
Lipid-anchored proteins: covalently bound to lipid tails, often found
with membrane sphingolipids, which leads to areas called lipid
Membrane Carbohydrates Attach to Both Lipids and Proteins
oMembrane carbs are mainly sugars attached to glycoproteins or
glycolipids, found only on cells external surface where it forms a
protective layer called the glycocalyx
Intracellular Compartments
Cells are Divided into Compartments
oCell membrane controls the movement of material between the cell
interior and the outside by opening and closing protein gates
oA cell is internally divided into the cytoplasm and the nucleus
The Cytoplasm Includes the Cytosol, Inclusions and Organelles
oCytosol: intracellular fluid; semi-gelatinous fluid containing dissolved
nutrients and proteins, ions, and waste products
oInclusions: particles of insoluble material (stored nutrients and
nonmembranous organelles), suspended in cytosol
oOrganelles: membrane-bound compartments with specific roles
Inclusions are in Direct Contact with the Cytosol
oInclusions do not have membranes so movement of material between
inclusions and the cytosol does not need be to transported across a
Cytoplasmic Protein Fibers Come in Three Sizes
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