DESCRIBES THE 3 MAIN PARTS OF THE CELL NAMELY, 1) PLASMA MEMBRANE 2)CYTOPLASM 3) NUCLEUS

1. THE CELL
Marilyn E. Soriano, PTRP,
LPT

2. Three main parts of the Cell:
1. plasma membrane,
2. cytoplasm,
3. nucleus.
1. The plasma membrane
 forms the cell’s flexible outer surface,
separating the cell’s internal
environment from the external
environment
 a selective barrier that regulates the
flow of materials into and out of a cell.
• This selectivity helps establish and
maintain the appropriate
environment for normal cellular
activities
 plays a key role in communication
among cells and between cells and
their external environment

3. 3. The nucleus
 is a large organelle that houses
most of a cell’s DNA.
 Within the nucleus, a
chromosome- a single molecule
of DNA associated with several
proteins, contains thousands of
hereditary units called genes
that control most aspects of
cellular structure and function.
2. The cytoplasm
 consists of all the cellular contents between
the plasma components: cytosol and
organelles.
1. Cytosol (intracellular fluid)- the
fluid portion of cytoplasm,
contains water, dissolved solutes,
and suspended particles.
2. Organelles
• Each type of organelle has a
characteristic shape and
specific functions: cytoskeleton,
ribosomes, endoplasmic
reticulum, Golgi complex,
lysosomes, peroxisomes, and
mitochondria.

4. THE
PLASMA
MEMBRANE

5.  a flexible yet sturdy
barrier that surrounds
and contains the
cytoplasm of a cell.
 is best described by
using a structural
model called the fluid
mosaic model.
THE PLASMA MEMBRANE

6.  The Lipid Bilayer
 The basic structural framework
of the plasma membrane is
the lipid bilayer, two back-to-
back layers made up of three
types of lipid molecules—
phospholipids, cholesterol,
and glycolipids.
• phospholipids- 75%.
• cholesterol- 20%,
• glycolipids- 5%,
THE PLASMA MEMBRANEStructure of the Plasma Membrane

7.  Lipids are amphipathic molecules,
which means that they have both
polar and nonpolar parts.
• In phospholipids:
o The polar part is the phosphate-
containing “head,” which is hydrophilic.
• hydrophilic heads facing outward
• the heads face a watery fluid on
either side—cytosol on the inside and
extrafluid on the outside
o The nonpolar parts are the two long fatty
acid “tails,” which are hydrophobic
• hydrophobic tails in each half of the
bilayer point toward one another
• nonpolar, hydrophobic region in the
membrane’s interior
THE PLASMA MEMBRANE

8.  Cholesterol molecules are weakly
amphipathic and are interspersed
among the other lipids in both
layers of the membrane.
o the only polar region of cholesterol
is the tiny —OH group
• it forms hydrogen bonds with
the polar heads of
phospholipids and glycolipids.
o The nonpolar are the stiff steroid
rings and hydrocarbon tail of
cholesterol
• they fit among the fatty acid
tails of the phospholipids and
glycolipids.
THE PLASMA MEMBRANE

9.  The carbohydrate groups of
glycolipids.
o A polar “head”
o A nonpolar their fatty acid “tails”.
o Glycolipids appear only in the
membrane layer that faces the
extracellular fluid, which is one
reason the two sides of the
bilayer are asymmetric, or
different.
THE PLASMA MEMBRANE

10. MEMBRANE PROTEINS
o icebergs in the lipid sea,
whereas others are anchored
specific locations like islands.
o allow passage of several types
of lipid-soluble molecules
o act as a barrier to the entry or
exit of charged or polar
substances.
o act as signal receptors or as
molecules that link the plasma
membrane to intracellular or
extracellular proteins.
THE PLASMA MEMBRANE

11. Membrane proteins are classified as:
I. Integral- proteins extend into or
through the lipid bilayer and are
firmly embedded which are called
transmembrane proteins.
 Many integral proteins are
glycoproteins attached to the
that protrude into the extracellular
fluid.
 Amphipathic:
• Their hydrophilic regions
protrude into either the watery
extracellular fluid or the cytosol.
• their hydrophobic regions
extend among the fatty acid
tails.
THE PLASMA MEMBRANEArrangement of Membrane Proteins

12. II. Peripheral- are not as firmly
embedded in the
membrane.
 They are attached to
the polar heads of
membrane lipids or
to integral proteins at
the inner or outer
surface of the
membrane.
THE PLASMA MEMBRANE

13. A. INTEGRAL PROTEINS
1. Ion channels- pores or
holes that specific ions
can flow through to get
into or out of the cell.
Most ion channels are
selective; they allow only
a single type of ion to
pass through.
2. Carriers (transporters)
selectively moving a polar
substance or ion from
one side of the
membrane to the other.
Functions of Membrane Proteins
THE PLASMA MEMBRANE

14. 3. Receptors- serve as cellular
recognition sites: recognizes
and binds a specific type of
molecule. Insulin receptors
bind the hormone insulin.
4. Enzymes- catalyze specific
chemical reactions at the
inside or outside surface of
the cell. *Peripheral proteins
Functions of Membrane Proteins
THE PLASMA MEMBRANE

15. 5. Linkers- anchor proteins in the
plasma membranes of
neighboring cells to one
another or to protein
filaments inside and outside
the cell. *Peripheral proteins
B. GLYCOPROTEINS
1. Cell identity markers-enable
a cell to (1) recognize other
cells of the same kind during
tissue formation or (2)
recognize and respond to
potentially dangerous
foreign cells.
Functions of Membrane Proteins
THE PLASMA MEMBRANE

16. Functions of Membrane Proteins
C. PERIPHERAL PROTEINS- help
support the plasma membrane,
anchor integral proteins, and
participate in mechanical
activities such as moving
materials and organelles within
cells, changing cell shape in
dividing and muscle cells, and
attaching cells to one another.
THE PLASMA MEMBRANE

17. THE
CYTOPLASM

18. Cytoplasm consists of all the
cellular contents between the
plasma membrane and the
nucleus, and has two
components:
1. the cytosol
2. organelles, tiny structures
that perform different
functions in the cell.
CYTOPLASMTHE CYTOSOL (intracellular fluid)
 is the fluid portion of the cytoplasm that
surrounds organelles
 constitutes about 55% of total cell volume
 75–90% water plus various dissolved and
suspended components: ions, glucose,
amino acids, fatty acids, proteins, lipids,
ATP, and waste products; organic
molecules: lipid droplets that contain
triglycerides, and clusters of glycogen
molecules called glycogen granules
 the site of many chemical reactions
required for a cell’s existence.

19. The cytoskeleton is a network of protein filaments
that extends throughout the cytosol.
 Three types of filaments contribute to the
cytoskeleton’s structure, as well as the
structure of other organelles
A. microfilaments,
B. Intermediate filaments,
C. Microtubules

20. A. Microfilaments
 are the thinnest elements
of the cytoskeleton
 composed of the
proteins actin and
myosin and are most
prevalent at the edge of
a cell
CYTOSOL have two general functions:
1. help generate movement: muscle
contraction, cell division, and cell
locomotion (migration of embryonic cells
during development, the invasion of tissues
by white blood cells to fight infection, or the
migration of skin cells during wound
healing)
2. provide mechanical support: responsible
for the basic strength and shapes of cells
 anchor the cytoskeleton to integral
proteins in the plasma membrane.
 provide mechanical support for cell
extensions called microvilli which are
abundant on cells involved in
absorption, such as the epithelial cells
that line the small intestine

21. B. Intermediate Filaments
 thicker than microfilaments but
thinner than microtubules.
 found in parts of cells subject to
mechanical stress
 they help stabilize the position of
organelles such as the nucleus
and help attach cells to one
another.
CYTOSOLC. Microtubules
 the largest, long, unbranched hollow tubes
composed mainly of the protein tubulin.
 Assembly begins in the centrosome which
grow outward from the centrosome toward
the periphery of the cell
 help determine cell shape
 function in the movement of organelles

22.  specialized structures within
the cell that have
characteristic shapes, and
they perform specific
functions in cellular growth,
maintenance, and
reproduction
 cooperate to maintain
homeostasis
ORGANELLES

23. 1. The centrosome
 located near the nucleus
 consists of two components:
i. a pair of centrioles
ii. pericentriolar material-
Surrounding the
centrioles, which contains
hundreds of ring-shaped
complexes composed of
the protein tubulin
ORGANELLES

24. i. Cilia- numerous, short, hairlike projections
that extend from the surface of the cell
• Each cilium contains a core of 20
microtubules surrounded by plasma
membrane.
2. Cilia and Flagella
 motile projections of the cell surface
ORGANELLES

25. ii. Flagella
 are similar in structure to cilia but are typically much
longer. Flagella usually move an entire cell.
 A flagellum generates forward motion along its axis by
rapidly wiggling in a wavelike pattern.
ORGANELLES

26. 3. Ribosomes
 the sites of protein synthesis
 high content of one type of
ribonucleic acid (ribosomal RNA, or
rRNA), but each one also includes
more than 50 proteins
 consists of two subunits, one about
half the size of the other
 attached to the outer surface of the
nuclear membrane and to an
extensively folded membrane called
the endoplasmic reticulum.
 Other ribosomes are “free” or
unattached to other cytoplasmic
structures.
ORGANELLES

27. 4. Endoplasmic Reticulum
 is a network of membranes in the
form of flattened sacs or tubules.
 extends from the nuclear envelope to
which it is connected and projects
throughout the cytoplasm
 contain two distinct forms of ER,
which differ in structure and function.
 Rough ER
 Smooth ER
ORGANELLES

28. a. Rough ER is continuous with the
nuclear membrane and usually is
folded into a series of flattened
sacs.
• outer surface of rough ER is
studded with ribosomes, the
sites of protein synthesis.
• proteins synthesized by
ribosomes attached to rough
ER enter spaces within the ER
for processing and sorting.
• rough ER produces secretory
proteins, membrane proteins,
and many organellar proteins
b. Smooth ER extends from the rough ER to form
a network of membrane tubules.
 does not have ribosomes on the outer
surfaces of its membrane.
 synthesize fatty acids and steroids, such as
estrogens and testosterone.
 In liver cells, enzymes of the smooth ER help release
glucose into the bloodstream and inactivate or
detoxify lipid-soluble drugs or potentially harmful
substances, such as alcohol, pesticides, and
carcinogens (cancer-causing agents).
 In liver, kidney, and intestinal cells a smooth ER
enzyme removes the phosphate group from
glucose-6-phosphate, which allows the “free”
glucose to enter the bloodstream.
 In muscle cells, the calcium ions (Ca2) that trigger
contraction are released from the sarcoplasmic
reticulum, a form of smooth ER.

29. 5. Golgi Complex
 proteins synthesized by ribosomes attached to
rough ER are ultimately transported to other
regions of the cell.
 The first step in the transport pathway is
through an organelle called the Golgi
complex.
 consists of 3 to 20 cisternae, small, flattened
membranous sacs with bulging edges that
resemble a stack of pita bread. The cisternae
are often curved, giving the Golgi complex a
cuplike shape.
 The cisternae at the opposite ends of a Golgi complex
differ from each other in size, shape, and enzymatic
activity.
o The convex entry (cis) face is a cisterna that faces the
rough ER.
o The concave exit (trans) face is a cisterna that faces
the plasma membrane.
o Sacs between the entry and exit faces are called
medial cisternae.
ORGANELLES

30.  Proteins arriving at, passing through, and
exiting the Golgi complex do so through
maturation of the cisternae and
exchanges that occur via transfer
vesicles:
1. Proteins synthesized by ribosomes
on the rough ER are surrounded by
a piece of the ER membrane, which
eventually buds from the membrane
surface to form transport vesicles.
2. Transport vesicles move toward the
entry face of the Golgi complex.
3. Fusion of several transport vesicles
creates the entry face of the Golgi
complex and releases proteins into
its lumen (space).
4. The proteins move from the entry face into one or more
medial cisternae. Enzymes in the medial cisternae modify the
proteins to form glycoproteins, glycolipids, and lipoproteins.
Transfer vesicles that bud from the edges of the cisternae
move specific enzymes back toward the entry face and move
some partially modified proteins toward the exit face.
ORGANELLES

31. 5. The products of the medial cisternae
move into the lumen of the exit face.
6. Within the exit face cisterna, the
products are further modified and are
sorted and packaged.
7. Some of the processed proteins leave
the exit face and are stored in secretory
vesicles. These vesicles deliver the
proteins to the plasma membrane,
where they are discharged by
exocytosis into the extracellular fluid.
8. Finally, some processed proteins leave
the exit face in transport vesicles that
will carry the proteins to another
cellular destination. For instance,
transport vesicles carry digestive
enzymes to lysosomes.
ORGANELLES

32. 6. Lysosomes
 are membrane-enclosed vesicles that form from
the Golgi complex.
 contain as many as 60 kinds of powerful digestive
and hydrolytic enzymes that can break down
a wide variety of molecules
 Because lysosomal enzymes work best at an acidic
pH, the lysosomal interior has a pH of 5, which is
100 times more acidic than the pH of the cytosol
(pH 7) help recycle worn-out cell structures.
 The lysosomal membrane also includes
transporters that move the final products of
digestion, such as glucose, fatty acids, and amino
acids, into the cytosol.
 lysosome can engulf another organelle, digest it,
and return the digested components to the
cytosol for reuse.
ORGANELLES

33.  Autophagy is the process by which entire
worn-out organelles are digested:
i. in which the organelle to be digested
is enclosed by a membrane derived
from the ER to create a vesicle called
an autophagosome;
ii. the vesicle then fuses with a lysosome.
• Autophagy is also involved in
• cellular differentiation,
• control of growth,
• tissue remodeling,
• adaptation to adverse
environments,
• cell defense.
 Autolysis is the process to destroy the entire cell
that contains them.
 responsible for the tissue deterioration that
occurs immediately after death.
 Fertilization: the head of a sperm cell releases
lysosomal enzymes that aid its penetration of
the oocyte by dissolving its protective
coating in a process called the acrosomal
reaction.
ORGANELLES

34. 7. Peroxisomes (microbodies)
 similar in structure to lysosomes
but smaller
 contain several oxidases:
that can oxidize (remove
hydrogen atoms) various organic
substances.
 example: amino acids and fatty
acids are oxidized, and toxic
substances such as alcohol.
 very abundant in the liver where
detoxification of alcohol and
other damaging substances
occurs.
8. Proteasomes
 tiny barrel-shaped structures consisting
of four stacked rings of proteins around
a central core
 functions as continuous destruction of
unneeded, damaged, or faulty proteins
 example: proteins that are part of
metabolic pathways need to be
degraded after they have accomplished
their function.
ORGANELLES

35. 9. Mitochondria
 “powerhouses” of the cell because they
generate most of the ATP through aerobic
respiration.
 Active cells that use ATP at a high rate—
such as those found in the muscles, liver,
and kidneys—have a large number of
mitochondria.
 play an important and early role in
apoptosis: orderly, genetically
programmed death of a cell.
• Large numbers of destructive free
radicals
• DNA damage
• Growth factor deprivation
• Lack of oxygen and nutrients
ORGANELLES

36.  A mitochondrion consists of:
1. Outer mitochondrial membrane
2. Inner mitochondrial membrane:
contains a series of folds called
mitochondrial cristae.
3. Central fluid-filled space between
in the mitochondrial matrix
ORGANELLES

37. The nucleus
 is a spherical or oval-shaped structure
that usually is the most prominent
feature of a cell.
I. A double membrane called the
nuclear envelope:
 which are lipid bilayers similar to
the plasma membrane
 is continuous with rough ER and
resembles it in structure
NUCLEUS

38. II. Nuclear pores extend through the nuclear
envelope
 which consists of a circular arrangement
of proteins surrounding a large central
opening that is about 10 times wider than
the pore of a channel protein in the
plasma membrane.
 control the movement of substances
between the nucleus and the cytoplasm.
III. Nucleoli
 function in producing ribosomes
 simply a cluster of protein, DNA, and RNA
 not enclosed by a membrane
 sites of synthesis of rRNA and assembly of
rRNA and proteins into ribosomal subunits
NUCLEUS

39. IV. Genes cell’s hereditary
units:
 control cellular
structure and direct
cellular activities
 man somatic cells: 46
chromosomes, 23
inherited from each
parent.
o Each chromosome is a
long molecule of DNA
that is coiled together
with several proteins.
o Chromatin: complex
of DNA, proteins, and
some RNA.
o chromatin has a beads-on-a-
string structure.
• Each bead is a nucleosome that
consists of double-stranded
DNA wrapped twice around a
core of eight proteins called
histones, which help organize
the coiling and folding of DNA.
• The string between the beads is
called linker DNA, which holds
adjacent nucleosomes together.
NUCLEUS