Cells: the Building Blocks of Life

Cells: the building blocks of life!!!

What is a cell?

______

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?

· 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 Fuzzy, sticky carbohydrate-rich area surrounding the cell

o Every cell has a ______of sugars in its glycocalyx; therefore, the glycocalyx provides a very specific biological marker for ______

o 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!

Membrane Proteins

Integral Proteins / Peripheral Proteins

3 factors bind cells together

Glycoproteins in the glycocalyx act as an adhesive
Wavy contours of membranes fit together in a tongue and groove fashion
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 / Active Transport
o Simple diffusion
o Facilitated diffusion
o Osmosis
o Filtration / o Solute Pumping
o Vesicular Transport
Exocytosis
Endocytosis (phagocytosis)
o Bulk Phase Endocytosis
o Receptor-Mediated Endocytosis

Passive Transport

Diffusion

o The tendency of molecules or ions to scatter ______throughout the environment

o Molecules move from areas of ______concentration to ______concentration

Simple Diffusion

o Substances that are nonpolar and lipid soluble (oxygen, carbon dioxide, fat-soluble vitamins, and alcohol) diffuse directly through the lipid bilayer

o However, polar and charged particles can selectively pass through channel protein pores if they are small enough

Facilitated Diffusion

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

o ______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 The diffusion of a ______, such as water through a selectively permeable membrane

o 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

· 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

· solutions with the same concentration of ______as the cells

· Cells retain ______shape and have no loss or gain of ______

Hypertonic

· Solutions with ______concentration of solutes than the cell

· Cells in a hypertonic solutions lose water and ______(crenate)

Hypotonic

· Solutions with a ______concentration of solutes than the cell

· Cells in a hypotonic solution ______water and ______and sometimes burst (lyse)

Filtration

· 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

· Similar to ______diffusion in that it needs carrier proteins that combine with the transported substances.

Solute pumping

· move ______“uphill” against their concentration gradients

Vesicular Transport

· 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

· 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

· Extracellular substances are engulfed by being enclosed in a membranous vesicle

Types of endocytosis

o Phagocytosis—cell ______‖

o Pinocytosis—cell ______‖

o Receptor mediated

The Cytoplasm

· The “stuff” between the plasma membrane and the nucleus

· Forms the foundation of the cell and contains the ______“Little organs”

The Organelles

· The “machinery” of the cell

· Each organelle “little organ” has a specific job in the cell to maintain the life of the cell

Mitochondria

· 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 ______

· Complex organelles that contain their own ______, ______, and ribosomes and are able to ______themselves

Ribosomes

· 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

· 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

· 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

· 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

· 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

· 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

· Cylindrical structures made of tubulin proteins

· ______the cell and give it ______

· Involved in intracellular and cellular ______

· Form the ______

Centrioles

· 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

· 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

· 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

· 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

· 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

· Spherical bodies found within the ______

· Produce ______molecules for the creation of ______

Chromatin

· Uncoiled ______consisting of DNA and histone protein molecules

· ______is responsible for packing long DNA molecules in a compact, orderly way

Cell Division

· 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