Cells: the building blocks of life!!!
What is a cell?
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Cells: An Overview Generalized
There are trillions of cells in the human body
Of those trillions, there are over 200 different kinds that vary in size, shape and function
Despite all their differences, all human cells have 3 main parts
_____________________________________– the outer layer of the cell
_____________________________________ – fluid inside the cells. Contains organelles
______________________________________ – the control center of the cell
The Plasma Membrane…What is it?
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The outer layer of the cell. Think of it as the _________________________________ for the cell
It is a _________________________________________________ that is selective about what
can enter or leave the cell
Separates the body’s 2 main fluid compartments
o __________________________________ – fluid inside the cell
o
__________________________________- fluid outside and in between the cells
The Plasma Membrane: Structure
Phospholipids: ______
Glycolipids: _______
Cholesterol:_______
Double layer membrane primarily made of ______________________________
The polar _______________ are attracted to water (hydrophilic) so they lie on the inner and outer surface of the
membrane
***remember intracellular fluid and extracellular fluid = water
The nonpolar _______________avoid the fluid (hydrophobic) and line up in the center of the membrane
Glycolipids
Lipid with an attached _________________________________
Found only in the outer surface of the plasma membrane
Combine with other glycolipids to make ______________________ (sugar coating)
Glycocalyx
o
o
o
Fuzzy, sticky carbohydrate-rich area surrounding the cell
Every cell has a _________________________________ of sugars in its glycocalyx; therefore, the
glycocalyx provides a very specific biological marker for ______________________________
Essentially I.D. tags for the cell to cell recognition
**This is why sperm know to fertilize an egg and not a blood cell!!!
Cholesterol
It’s not the devil!
O Wedges between ___________________________________________________
O _________________________ the membrane
Membrane Proteins
Integral Proteins
Peripheral Proteins
3 factors bind cells together
1. Glycoproteins in the glycocalyx act as an adhesive
2. Wavy contours of membranes fit together in a tongue and groove fashion
3. Special membrane junctions are formed
Special Membrane Junctions:
Tight Junction
o
__________________________________ junction helps prevent molecules from passing through the
extracellular space between adjacent cells
Desmosomes
o
______________________________ junctions scattered like rivets along the sides of adjacent cells that
prevent ________________________
o
Button like plaque on cytoplasmic side held together by thin linker proteins (cadherins) on the cellular
side
o
Thicker protein filaments “lock” together with the plaque on the opposite side to anchor them together
o
Strong yet flexible junctions
Gap Junctions
o
Allow chemical substances to pass between adjacent cells
o
Connected to other cells by a hollow cylinders ( ______________________)
o
Ions, sugars, and other small molecules pass through these channels
Membrane Transport
The plasma membrane is a _____________________________________________ membrane that allows
nutrients to enter the cell while keeping unwanted elements out of the cell as well as ridding itself of toxic waste
products.
Interstitial Fluid (the cellular super highway)
o
Fluid between the cells that contains nutrients such as vitamins, sugars and amino acids, hormones and
neurotransmitters, and waste products
Passive Transport
o
o
o
o
Simple diffusion
Facilitated diffusion
Osmosis
Filtration
Active Transport
o Solute Pumping
o Vesicular Transport
Exocytosis
Endocytosis (phagocytosis)
o Bulk Phase Endocytosis
o Receptor-Mediated Endocytosis
Passive Transport
Diffusion
o
o
The tendency of molecules or ions to scatter ____________________ throughout the environment
Molecules move from areas of _______________ concentration to ________________ concentration
Simple Diffusion
o
o
Substances that are nonpolar and lipid soluble (oxygen, carbon dioxide, fat-soluble vitamins, and
alcohol) diffuse directly through the lipid bilayer
However, polar and charged particles can selectively pass through channel protein pores if they are
small enough
Facilitated Diffusion
o
o
Certain molecules (glucose and other simple sugars) are too ________________________ to dissolve in
the lipid bilayer and too large to pass through membrane channels so they must be helped across
___________________________________________ in the plasma membrane allow entrance to the
cell bypassing the non- polar portion of the cell by engulfing then releasing the molecule into the cell
Osmosis
o
o
The diffusion of a ______________________, such as water through a selectively permeable membrane
Occurs whenever the water concentration differs on the two sides of the membrane
***Even though water is highly polar, it passes easily through the lipid bilayer****
Tonicity
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Osmotic imbalances cause cells to shrink or swell until the solute concentration on both sides of the
plasma membrane is the same, or the membrane is stretched to its breaking point
Tonicity is the ability of a solution to change the tone or shape of cells by altering their internal water
volume
Isotonic
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solutions with the same concentration of ________________________________ as the cells
Cells retain ______________________________shape and have no loss or gain of ________________
Hypertonic
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Solutions with ________________________concentration of solutes than the cell
Cells in a hypertonic solutions lose water and _________________________________ (crenate)
Hypotonic
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Solutions with a ______________________________ concentration of solutes than the cell
Cells in a hypotonic solution __________________ water and ____________________and sometimes
burst (lyse)
Filtration
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The process that forces water and solutes through a membrane or capillary wall by fluid, or hydrostatic,
pressure.
Pushes solute containing fluid from a higher pressure area to a lower pressure area.
Not selective, only blood cells and protein molecules too large to pass through the membrane pores are
held back
Active Transport
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Similar to ___________________________________diffusion in that it needs carrier proteins that
combine with the transported substances.
Solute pumping
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move ___________________________ “uphill” against their concentration gradients
Vesicular Transport
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The transport of large particles and macromolecules across the plasma membrane
The substance or cell product to be released is 1st enclosed in a membranous sac called a vesicle
2 types of vesicular transport
_______________________________ - movement of substances from the cell interior to the extracellular space
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Moves materials out of the cell
Material is carried in a membranous vesicle
Vesicle migrates to plasma membrane
Vesicle combines with plasma membrane
Material is emptied to the outside
__________________________________ – movement of substances from the extracellular space into the cell
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Extracellular substances are engulfed by being enclosed in a membranous vesicle
Types of endocytosis
o
o
o
Phagocytosis—cell _______________________‖
Pinocytosis—cell ________________________‖
Receptor mediated
The Cytoplasm
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The “stuff” between the plasma membrane and the nucleus
Forms the foundation of the cell and contains the ________________________________ “Little organs”
The Organelles
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The “machinery” of the cell
Each organelle “little organ” has a specific job in the cell to maintain the life of the cell
Mitochondria
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The “power plants” of a cell providing most of its __________________________________
Carbohydrate, lipid and protein molecules are broken down here and the energy is used to form
molecules of __________________
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Complex organelles that contain their own __________, ___________, and ribosomes and are able to
______________________________themselves
Ribosomes
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Made of protein and RNA, these are the site of ____________________________________ (production)
Some are free floating in the cytoplasm and others are attached to membranes forming
___________________________________
Rough ER
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Ribbons of membrane studded with _________________________________, which make all the
proteins secreted from the cells
Manufactures the ___________________________ proteins and ________________________________
that form the plasma membrane –considered a “membrane factory”
Once made, proteins are enclosed in _____________________________ for transport to the
____________________________________________ where they are further processed
Golgi Aparatus
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Made of stacked, flattened membranous sacs with many tiny vesicles that pinch of for “shipping
proteins.
Main function is to ________________________________________________________ the proteins
and lipids made by the rough ER. --See figure 3.20 on page 86
“Packages” are shipped 1 of 3 ways
o Vesicle is destined for _________________________________
o Vesicle is to become part of the __________________________________________________
o Vesicles becomes a ________________________________
Lysosomes
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Vesicles produced by the ______________________________________ that contain digestive enzymes
Function as a cell’s “demolition crew”by
o Digesting particles taken in by phagocytosis (esp. bacteria, viruses, and toxins)
o Geting rid of worn-out or non-functioning organelles
o Performing metabolic functions such as glycogen breakdown and release
o Breaking down non-useful tissues such as the webbing between the fingers and toes of a
developing fetus
o Breaking down bone to release Calcium ions into the blood
Peroxisomes
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Membranous sacs containing powerful _____________________________ (oxidases and catalases)
which detoxify harmful substances and neutralize free radicals
Especially numerous in the _______________________ and _________________________ cells which
are very active in detoxification
Free Radicals- normal byproducts of cellular metabolism that can have harmful effects on cells if allowed
to accumulate
The Cytoskeleton
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The “cell skeleton” – it is a network of _________________ running through the ___________________
Supports cell structure and aids in cell movement
3 types of rods from smallest to larges
o Microfilaments
o Intermediate filaments
o microtubules
Microtubules
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Cylindrical structures made of tubulin proteins
___________________________the cell and give it __________________________
Involved in intracellular and cellular ______________________________
Form the ________________________________
Centrioles
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Paired cylindrical bodies each composed of ______________ triplets of microtubules
Organize a microtubule network during ___________________________ to form the spindle and asters
Form the bases of ___________________________ and ________________________
Cilia
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Whip-like cellular extensions on the surface of certain cells
Example: cells that line the respiratory tract have cilia that propel mucus laden with bacteria and dust
particles upward away from the lungs
Flagella
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Long tail-like projection formed by centrioles
Example: sperm which have one flagellum used for movement
NOTE: Cilia propel other substances across the cell’s surface whereas the flagella propels the cell itself
Microvilli
“Little Shaggy Hairs”
 Tiny finger like extensions of the plasma membrane
 Increase the plasma membrane ______________________________________ tremendously
The Nucleus
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The ____________________________________________________ of the cell
Has 3 regions or structures
o The nuclear envelope
o Nucleoli
o Chromatin
Most cells only have 1 nucleus but some are ___________________________________ – having more
than 1 nucleus (ex. Skeletal muscles)
All human cells except ______________________________________ have at least 1 nucleus. RBC’s are
the only anucleate cells therefore cannot reproduce and only live for 3-4 months in the blood stream
The Nuclear Envelope
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Surrounds the _______________________ in a double layer membrane barrier separated by a fluid
filled space
The outer membrane is connected with the rough ER of the cytoplasm and studded with ribosomes &
pores
Nucleoli
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Spherical bodies found within the ____________________________
Produce ________________________________________ molecules for the creation of
_________________________________
Chromatin
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Uncoiled _____________________________________ consisting of DNA and histone protein molecules
_______________________________ is responsible for packing long DNA molecules in a compact,
orderly way
Cell Division
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Cells must reproduce if an organism is to grow and repair damaged tissues
During cell reproduction, a cell divides its genes equally and then splits into 2 identical cells
Cell division involves 2 major events
o Mitosis- when the chromatin in the nucleus combine into chromasomes and are equally divided
between the 2 forming cells
o
Cytokinesis – separation of the cytoplasm to produce 2 daughter cells. Each daughter cell has
the same number of chromosomes as the parent cell