Transcript education - Catherine Huff`s Site

“Education is a progressive discovery of our own
ignorance.”
-Will Durant
EDUCATION
The Amazing Cell
Chapter 3
Anatomy and Physiology
Cells
• Basic unit of living things.
• Can exist alone as a single, free, living plant or animal
• Can combine to form elaborate and complex organisms.
• Posses unique genetic material
• Diverse in apperance
• Multi-cellular organisms are when cells have differentiated and
become grouped into specialized tissues that work
collaboratively to sustain life for the animal as a whole.
• To understand the anatomy and physiology of tissues and
systems we first need to understand the cell.
Evolution of Cells
• Evolved about 3 billion years ago.
• Primitive cells are thought to have resembled present-day bacteria and
contained a single strand of DNA in a gelatinous protoplasm.
• Prokaryotes- “before nucleus”, cells without nucleus were thought to
have developed first.
• Has DNA but not in a separate compartment
• Only cells for about 1.5 billion years
• Eukaryotes- “true nucleus”, developed later and are found in all multicellular organisms.
• Has distinct nucleus surrounded by protective nuclear envelope.
• In the nucleus DNA has combined with protein to form
chromosomes.
Viruses / Prions
Viruses
• Smaller than cells
• Composed of a protein-covered capsule
• Contain one strand of DNA or one strand of RNA, but not both.
• Parasitic b/c they cannot survive independently.
• They cannot reproduce themselves, rely on cells to multiply.
• Essentially the virus injects its genetic material into the cells cytoplasm and reprograms
the cell to manufacture lots of viruses.
Prions
• Small, protein-based particle that is infectious and resilient, but not a living pathogen.
• Lack DNA/RNA
• Fatal and cause a progressive neurodegenerative disorder - Scrapie
Prokaryotic vs.
Eukaryotic Cells
Size Limitations
• Size of most cells is restricted to 10-30 µm in diameter because of
relationship between surface area and volume of a cell.
• Why is this important:
• Smaller cells can feed themselves efficiently to carry on functions.
• Large cells could not take in nutrients fast enough to support cell and
would therefore die.
• Also a small cell is better governed by a single nucleus. Larger cells
need multiple nuclei. Ex. Cardiac or Skeletal Muscle
Mammalian Cell Anatomy
• Contain essential structures:
• Cell membrane (also known as plasma
membrane).
• Separates cell from environment.
• Cytoplasm
• Everything inside the cell membrane aside
from nucleus and genetic material.
• Composed of proteins, electrolytes,
metabolites, flexible cytoskeleton and
organelles
• Nucleus
• Contains the genetic material of the cell.
Cell Membrane
• Video - The Cell Membrane
• Flexible, elastic barrier between inner cytoplasm and outer
environment.
• Contains infoldings and outpouchings that provide extra surface
area.
• Capable of self-repair
• If damages causes intracellular contents to release the cell dies.
• Governs the movement of atoms and molecules in and out of the
cell.
• Consists primarily of protein, phospholipids, cholesterol, lipids, and
carbohydrates.
https://www.youtube.com/watch?v=S7CJ7
xZOjm0
Membrane Structure
• Lipid bilayer: composed of two layers of
phospholipid molecules
• Hydrophilic “heads” are on outside
• Hydrophobic fatty acid “tails” are on
the inside
• Most lipid soluble molecules(O2, CO2)
easily pass through membrane
• Water-soluble molecules do not
readily pass through (AA, Sugars,
Protein)
• Cholesterol molecules wedge
themselves between the
phospholipids and help stabilize the
membrane.
Fluid mosaic: Proteins
suspended in bilayer and move
easily throughout membrane to
create a constantly changing
pattern.
Cell Membrane Structure
• Composed of Structural and Globular proteins.
• What are these also called?
• Globular proteins aka Functional Proteins
• What do they do?
• Responsible for the membrane’s special functions.
• Globular proteins may occur on the cell surface or inside the lipid bilayer.
Integral Proteins
• Proteins that occur within the bi-layer are called
integral proteins.
• Globular proteins that span the entire width of the membrane and
may create channels through which other molecules can pass.
• Some use ATP for energy to actively transport substances across cell
membrane
• Channels they create may be:
• Selective
• Permit only certain molecules in or out of the cell
• Pores
• Allow the passage of molecules water molecules freely.
• Selective with certain solutes
Cell Membrane
Peripheral Proteins
• Type of globular protein which can be bound to the
inside or outside surfaces of the cell membrane.
• Sometimes act as enzymes
• Inside are more restricted in movement
• May be involved in changing the cell’s shape (muscle
contraction).
Cell Membrane: Inner and
Outer Surface
• Proteins on the inner surface of the membrane may be bound to
the cytoskeleton, keratin fibers or peripheral proteins.
• Glycocalyx – ”sugar coating” on the cell surface of some cells
made of glycoprotein and glycolipids.
• Unique to each cell – provides improved cell to cell adhesion.
• Represents important biological marker for intercellular
recognition
• Cell and antibodies, cell and viruses
Glycocalyx
• 2 Families of molecules:
• Cell Adhesion Molecules (CAM’s)
• Sticky glycoproteins that cover cell surface, aid in bonding
• Help cells move past one another and signaling.
• Signal circulating cells like WBCs to areas of inflammation or
infection
• Membrane Receptors
• Integral proteins and glycoproteins that act as binding sites on
the cell surface.
• Involved in cell to cell recognition – Contact signaling.
• Important during cell mediated immune response through
assisting bacteria and viruses in finding target cells.
• Chemical Signaling – chemical messengers called ligands bind to
specific binding sites on cell surfaces and bring about change in
the cell’s activity.
Cilia and Flagella
• Extensions of the plasma membrane that extend into the extracellular
space.
• Energetic hairs that are structurally identical but functionally different.
• Both contain 9 pairs of microtubules that encircle a central pair of
microtubules.
Cilia- occur in large numbers on the exposed surface of
some cells.
•Shorter than flagella and move synchronously to create
waves of motion for propulsion.
Functions:
In upper respiratory tract, propel bacteria and
mucus from the lungs
In oviduct, pulls egg from ovary into oviduct.
http://www.dnatube.com/video/363/Cilia-andFlagella
Flagella
• Flagella- significantly longer than cilia and
usually occur singularly.
• Attached to individual cells and aid in
propulsion.
• Example:
• Tail of sperm is flagellum
• Only mammalian cell that is propelled by a
single flagellum
Tour of the Cell
• https://www.youtube.com/watch?v=1Z
9pqST72is