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Biology 211
Anatomy & Physiology I
Cells
Recall:
SYSTEMS are composed of one or more organs,
all serving a common function
ORGANS are composed of one or more types
of tissues, all serving a common function
TISSUES are composed of one or more types
of cells and their products, all serving a
common function
CELLS are composed of different types of
organelles, all serving a common function
ORGANELLES are composed of different types
of molecules, all serving a common function
Cells:
- Highly organized; composed of organelles and cytoplasm
- Arise from prexisting cells
Some exist as stem cells
to replace more specialized ones
- In human, all eukaryotic:
nuclei and other organelles
surrounded by membranes
- Some = highly specialized & can perform only one function
Others = relatively unspecialized with many functions
Cells:
Shape: Highly variable:
Cells:
Size: Highly variable
Spheroid/polygonal/cuboidal:
Average = 10-15 micrometers diameter
Range = 2 micrometers (sperm)
100 micrometers (oocyte)
Skeletal muscle cells may be
300 millimeters long
Nerve cells may be more than
a meter long
Independent Study:
Chapter 3 of your Saladin
text discusses the organelles
of most cells.
You should understand the
basic structure and function
of each of the following:
Nucleus
Ribosomes
You should also understand the
Endoplasmic reticulum
basic structure and function of
Golgi complex
cilia and flagella
Mitochondria
Lysosomes
Peroxisomes
You will be responsible
Vesicles
for these on exams
Cytoskeleton
Plasma Membrane:
Also called "plasmalemma"
May have special names in specific types of cells
e.g. "sarcolemma" in muscle cells,
"neurolemma" in nerve cells
- Keeps inside in and outside out
while
- Controlling movement of ions/molecules into and out of cell
- Interacts with other cells and with extracellular materials
around cell
- Allows cell to recognize and respond to chemical signals
Plasma Membrane:
Basic structure = double layer of phospholipids with proteins
and cholesterol embedded within it
Plasma Membrane:
Proteins and glycoproteins:
a) Channels and carriers to allow ions
and molecules to pass in or out
b) Identity markers to allow cells to
identify each other
c) Cell adhesion molecules to hold cells together
d) Receptors to allow the cell to respond to hormones
and other chemical signals
e) Enzymes to form cellular messengers or to
remove unwanted molecules
Plasma Membrane:
Has many types of specialized junctions for cell-to-cell
attachment and/or communication. We will focus on three:
1. Tight junctions: Protein molecules in plasma
membranes of two adjacent cells form bonds; hold cells
strongly together and prevent materials from passing
between them
Plasma Membrane:
Has many types of specialized junctions for cell-to-cell
attachment and/or communication. We will focus on three:
2. Desmosomes: Protein molecules in plasma membranes
of two adjacent cells form bonds in isolated spots; hold cells
strongly together
Plasma Membrane:
Has many types of specialized junctions for cell-to-cell
attachment and/or communication. We will focus on three:
3. Gap Junctions: Protein molecules in plasma
membranes of two adjacent cells form channels between
them; allow molecules to flow from cell to cell
Movement of Materials Across Plasma Membrane:
Thousands of different materials are actively crossing the
plasma membranes of your cells every second of every day
of your life, both into and out of the cell:
e.g. Water
Nutrients like amino acids, monosaccharides,
fatty acids, nucleotides, vitamins
Gases like oxygen, carbon dioxide
Waste products like lactic acid, urea, bilirubin
Ions (electrolytes) like sodium, potassium, magnesium,
iron, calcium, chloride, phosphate, sulfate
Hormones like insulin, estrogens, growth hormone
Neurotransmitters
Proteins the cell secretes
Debris which phagocytic cells ingest
(many others)
Movement of Materials Across Plasma Membrane:
Thousands of different materials are actively crossing the
plasma membranes of your cells every second of every day
of your life, both into and out of each cell:
This is not a random process! Each cell has a variety of
different processes to regulate this exchange so that
The right materials cross the membrane
In the right concentrations
At the right time
In the right direction
etc.
Plasma Membrane:
This regulated movement of ions and
molecules is due to:
a) Solubility of phospholipids for
nonpolar molecules
b) Channels for passive movement of
materials across the membrane.
Channels can open and close.
c) Pumps to actively transport molecules
across the membrane.
Pumps turn on and off.
d) Vesicles which form from (or
fuse to) the plasma membrane
More Independent Study:
Saladin text discusses various types of membrane transport.
Be sure you understand, in moderate detail, how each of
the following occurs and what it accomplishes:
- Filtration
- Simple diffusion, including osmosis
- Carrier-mediated transport
Facilitated diffusion
Active transport (including cotransport & countertransport)
- Vesicular transport
Pinocytosis
Receptor-mediated endocytosis
Phagocytosis
Exocytosis
You will be
responsible for
these on exams
Let's move on to tissues