Download Cell characteristics

•Cells
•Cells
basic unit of live
come from other living
cells
•Body is made of 75 trillion cells
•260 types of cells
•Cells are differentiated –specific
characteristics
 Cells
vary in size.
• Ovary cell- 140 micrometers
• Blood cell 7.5 micrometers
• Cell shape is determined b y function
 Neuron (nerve cells) have long axons
for transmitting impulses
 Skin cells are thin and flattened
because they reproduce constantly
 Three
main parts
• Nucleus: Stores DNA – control cell
functions
• Cytoplasm- Made of cytosol and
organelles
• Cell membrane- Separates the cell
from environment, protects and
communicate cells
 Made
of a double layer of phospholipids
 It is the boundary of cell and perform
some functions:
• Communication among cells
• Protect cell from the outside environment
• Selectively Permeable- Allow s substances in
and out of cell.
• It allows receive messages from other cellssignal transduction
-
It is mainly composed of lipids and
proteins, and some carbohydrates
It is a double layer of phospholipids.
• The phospholipids head is hydrophilic
( loves water) which are in the outside
of the membrane and the tails are
hydrophobic ( afraid of water) located
inside of the membrane
Interior is oily because made of fatty
acids.
-
• Carbon dioxide, oxygen and steroid can
pass through membrane easily.
• The layer is impermeable to water
molecules: proteins, amino acids…
• Cholesterol molecules embedded in cell
membrane make cell impermeable to
some of these molecules and stabilize it.
-
Contains a few lipids but many proteins
 Proteins in the plasma membrane decide
the functions of the membrane.
 Proteins are classified by shape, location
and function within the phospholipids
bilayer.
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Some are embedded in the plasma membrane
and are compact and globular. They function as
channels for small ions and molecules.
Some proteins coil in the plasma membrane and
extend outward, they function as receptors.
Peripheral proteins are globular and function as
enzymes and parts of signal transduction
pathways.
Other Peripheral proteins are cellular adhesion
molecules that enable certain cells to bind.
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Carbohydrate groups associate with peripheral
proteins form glycoproteins that help cells to recognize
each other. This is important because cells group
together to form tissues.
Some cells are separated by intercalated spaces with
fluid between.
Other cells are tightly packed with structures called
intercellular junctions that connect their cell
membranes.
 Types
of intercellular junctions:
• Tight junction: area of fusion, surrounds cells
like a belt. Example: digestive tract.
• Desmosomes: adjacent skin cells, they
reinforce structural unit. Example : skin cells.
• Gap junctions: channels that allow ions to
move between them. Example: heart.
• Proteins called Cellular Adhesion Molecules
(CAMs)guide cells to move. Example : white
blood cells
 1. Cytoskeleton
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2. Endoplasmic Reticulum
3. Ribosomes
4. Golgi Apparatus
5. Mitochondria
6. Lysosomes
7. Peroxisomes
8. Centrosomes
9. Cilia and Flagella
10. Microfilaments an d tubules
11. Nucleus
 It
is a group of protein rods and tubules
that form a supportive system.
Made of membraned-bound flattened sacs,
elongated canals and fluid filled vesicles.
 It is widely distributed through the cytoplasm,
and communicate with other organelles
 Function: Synthesis of protein and lipid
molecules
 The outer membrane of ER is full of spherical,
tiny structures called ribosomes. This is the
appearance of Rough Endoplasmic Reticulum.
 The tubules of Endoplasmic Reticulum move to
Golgi apparatus for further processing.

 Smooth
Endoplasmic Reticulum lacks of
ribosomes.
 It contains enzymes important in lipid
synthesis.
 Smooth Endoplasmic Reticulum is found
in cells in the digestive tract and it is
important in the breakdown of drugs and
alcohol.
 Some
are found in Endoplasmic
Reticulum and others are free in the
cytoplasm.
 All ribosomes are composed of RNA
and create a supportive enzyme activity
for amino acids to form proteins.
 Ribosomes are the sites of protein
synthesis.
 Composed
of a tack of half a dozen of
flattened membranous sacs called
cisternae.
 The Golgi apparatus refines, packs and
delivers protein synthesis.
 Proteins arrive at the Golgi apparatus
enclosed in tiny vessicles from the
Endoplasmic Reticulum and fuse with the
innermost of the apparatus to receive
proteins.
 As
the glycoproteins pass from layer to
layer through the Golgi stacks, they are
modified chemically.
 The vessicles fuse and they are release
outside (exocytosis)
 Movement of substances within cells by
the way of vessicles is called vessicle
trafficing.
 It
is formed by elongated, fluid filled
sacks about 2-5 micrometers.
 Contains
a small amount of DNA that
encodes information for making new
kinds of proteins and specialized RNA.
A
mitochondrion has two layers : an outer
membrane and an inner membrane
 The
inner membrane is folded in to form
of shelflike partitions called Cristae.
 Small enzymes are connected to cristae.
 The
mitochondrion captures and releases
energy into special chemical bonds of
the molecule ATP. ( Adenosine
Triphosphate)
 A typical cell contains about 1700 of them
 They
are called garbage disposals
 They
posses powerful enzymes that
destroy bacteria.
 Human
lysosomes contain 40 types of
enzymes.

Membranous sacks that resemble
lysosomes in size and shape
 Most
abundant in liver and kidneys
 Contain
enzymes –peroxidases
 Functions: Breakdown
lipids, bile acids,
degrade chemicals and detoxifies
alcohol
 It
is located in the cytoplasm near the
nucleus
 Consist
in two hollow centrioles. During
cell division, the centrioles move away
from each side of nucleus.
 Motile
extensions of cells
 They
are structurally different and they
differ in length and number present.
 Cilia
are abundant on the free surface of
certain epithelial cells.
 A cell usually only have one flagella,
wavelike movement.
 - Threadlike
structures
 Microfilaments
are tiny protein rods. They
cause movement, like in muscle fibers.
 Microtubules
are long and slender,
composed of protein tubulin, and help to
maintain the rigid of the cell
 It
is usually large, spherical and contains
the genetic material (DNA)
 The
DNA occurs as extremely long
molecules complexed with proteins form
chromatin fibers, which are visible in a
microscope as chromosomes.
 The
nucleus is double layered in a
nucleus envelope, which contain pores.
 The
nucleus pores are channels with
different proteins.
 Nucleus
contains a fluid (nucleoplasm)
 Nucleolus
is inside nucleus and is a small
dense body composed of DNA. It is the
site of ribosomes production
 Chromatin
is inside the nucleus and
contain loosely coiled fibers in the
nuclear fluid. Chromatin means colored
 When
cell division begins , these fibers
form chromosomes.
 Chromatin
fibers contain DNA wrapped
around proteins called histones.