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Cells
Karen Malt, MSN, RN
Cells
(part 1)
• Robert Hooke (1635-1703)- a scientist who
first applied the word “cell” to describe the
basic unit of life after viewing small spaces
created by cell walls using a very primitive
microscope.
• Cells- the smallest unit of all living things.
Cells
(part 1)
•Cells differ in size and shape.
• Human cells are microscopic in size and vary in
shape (threadlike, flat, irregular, brick-shaped)
and size.
• Ovum – (female sex cell) is about 150
micrometers
• Red Blood Cell (RBC) – 7.5 micrometers
Cells
(part 1)
• Cell Composition –
• Cytoplasm- a living substance that exists only in
cells.
• Plasma Membrane- thin membrane which
surrounds the cell. This membrane separates
the contents of the cell from the saltwater
solution called “Interstitial Fluid” (tissue fluid),
which bathes every cell inside the body.
Cells
(part 1)
•Parts of the Cell (main parts)
• Plasma Membrane –outer boundary
• Cytoplasm- living material in the cell
(except the nucleus)
• Nucleus- large structure that contains the
genetic code
Cells
(part 1)
• Plasma Membrane –forms the outer
boundary of the cell, very delicate, thin
structure 3/10,000,000 of an inch thick.
• The Plasma Membrane is made up of
two layers of fat molecules;
• Phospholipids – form a framework
• Cholesterol – provides stabilization to prevent
breakage
Cells
(part 1)
• Plasma Membrane – although fragile, is strong
enough to keep the cell intact.
• Allows certain substances in and bars certain
substances from entering the cell.
• The Plasma Membrane has “receptors” on it which
allows for certain chemicals to bind to these
receptors therefore a change in the cell function will
follow.
• The Plasma Membrane also identifies a cell as being
part of a particular individual (Tissue Typing). This is
done before transplanting tissue from one person
into another.
Cells
(part 1)
• Cytoplasm- Internal living material of cells.
This substance fills the space between the
plasma membrane and the nucleus.
• Organelles- (little organs) numerous small
structures that make up much of the cytoplasm
and function for the cell, like organs in the
body.
• Cytoskeleton- “cell skeleton” or the cell’s
internal supporting moving framework.
Cells
• Organelles:
•
•
•
•
•
•
•
Ribosomes
Endoplasmic Reticulum
Golgi Apparatus
Mitochondria
Lysosomes
Centrosome
Cell Extensions
(part 1)
Cells
(part 1)
• Ribosomes- very small particles found
throughout the cell. Each ribosome is made up
of two tiny subunits constructed mostly of a
specific type of RNA called “ribosomal RNA” or
(rRNA).
• Function: make enzymes and other protein
compounds. Also known as “protein factories.”
Cells
(part 1)
• Endoplasmic Reticulum –tubular passage ways
that carry proteins and other substances through
the cytoplasm of the cell from one area to
another.
• Two Types of ER
• Rough- A rough surface on the ER is due to all of the
ribosomes attached to its surface. The rough ER
receives, folds, and transports newly made proteins.
• Smooth- ER has no ribosomes attached to it and the
smooth ER makes a new membrane for the cell.
Cells
(part 1)
• Golgi Apparatus- tiny, flattened sacs
stacked on one another near the
nucleus, which makes carbohydrate
compounds, combines them with
protein molecules and then
packages the product in a globule.
Cells
(part 1)
• Mitochondria- energy converting
chemical reactions occur within this
organelle. These supply most of the
“power” for the cellular work. This
organelle has been nicknamed the
cells “power plants.”
•NOTE: the mitochondria has its own DNA.
Cells
(part 1)
•Lysosomes – nicknamed “digestive bags”
because lysosomes contain enzymes that
promote hydrolysis. They break apart or digest
large nutrient molecules. They can also digest
microbes that are invading the cell.
• NOTE: lysosomes were once thought to be
responsible for “cell death” or apoptosis, which
makes space for new cells, but a different
mechanism is now known to cause this.
Cells
(part 1)
• Centrosome – is a region of cytoplasm near
the nucleus, which is responsible for
organizing and moving the structures within
the cell.
• Centrioles- paired organelles found within
the centrosome. These structures form a
“spindle” which moves chromosomes
during cell division.
Cell
•Cell Extensions• Microvilli
• Cilia
• Flagella
(part 1)
Cell
(part 1)
• Microvilli- “fingerlike” projections off of the cell
membrane of some cells. Increase its ability to
absorb substances.
• Cilia- “hair-like” extensions that allow for
movement. Example; propel mucus over the
surface of cells in the respiratory/reproductive
tract.
• Flagella- A single projection extending from a cell.
Whips around like a propeller. Example: sperm cell
Cell
(part 1)
• Nucleus – central structure of a cell.
• Appears like a small sphere in the center portion of
the cell. The nucleus contains most of the cells
genetic code, which controls every organelle in the
cell. It also controls cellular reproduction.
• Nuclear Envelope- has tiny openings called “nuclear
pores” that permit large molecules to move in and
out of the nucleus. Within the nuclear envelope is
“nucleoplasm.” Within the nucleoplasm are:
• Nucleolus- Critical in protein formation
• Chromatin Granules- substance in the nucleus of cells
made up of DNA
Cells
(part 1)
•Chromosomes – During cellular division,
DNA molecules become coiled tightly forming
chromosomes. Each cell of the body has 46
different DNA molecules.