Download Chapters 4 and 5 Cell Structures, Functions and Transport

Cell Structure and Functions
Presentation by: Mahendra Kandel
For: Bachelor of Pharmacy
(NIST)
13 December 2010
The Eukaryotic Cell
The Beginnings
•Robert Hooke was the first person to observe cells in 1665.
•He looked at thin slices of cork under a very simple
microscope.
•The cork appeared as little boxes which he called cells.
•In 1883 MathiasSchleiden and Theodor Schwann proposed
that all plants and animals were composed of cells which were
the basic building blocks of life.
•In 1855 Rudolf Virchow stated that new cells arise from the
division of pre-existing cells and that chemical reactions
needed for life occurred inside the cell.
•All this work led to the formation of the cell theory
What is a cell?
• A cell is a small membrane-bound structure
that contains all the requirements for life.
• It is the smallest living structure.
Presentation By: Mahendra
Kandel.
The Cell Theory
• 1. All living things are composed of cells.
- can be a single cell or many cells
• 2. The cell is the smallest living thing that
shows all of the characteristics of life.
– homeostasis, metabolism, responsiveness, reproduction, evolution
• 3. All cells come from preexisting living
cells
Presentation By: Mahendra
Kandel.
Eukaryotic Animal Cell
• Eukaryotic means “true nucleus”
• Eukaryotic cells have a nucleus which contains the DNA.
• Eukaryotic animal cells are surrounded by a cell membrane.
• Inside is the jelly like substance called cytoplasm.
• Contained in the cytoplasm is the nucleus and other organelles
The other cell organelles include the endoplasmic
reticulum,(rough & smooth) mitochondria, Golgi apparatus,
ribosomes, lysosomes, centrioles, cilia, nucleolus.
Presentation By: Mahendra
Kandel.
The Human Cell
• The human cell is bounded by a plasma
membrane that encloses a central nucleus
surrounded by cytoplasm.
– Cytoplasm contains organelles, membranous
structures, and a cytoskeleton
• Human cells differ in size, shape and function
• Human body has at least 85 different cell types
Presentation By: Mahendra
Kandel.
Anatomy of a typical cell
1.
Cell membrane
2.
Cytoplasm
= cytosol + organelles
3.
Organelles
•Smallest:
•Granule cell in cerebellum: 4 μ
•RBC: 5-7 μ = 0.005-0.007 mm
•Largest:
•Anterior horn cell in spinal cord: 135 μ
•Ovum: 120 μ = 0.12 mm
•Longest:
Presentation By: Mahendra
•Pseudounipolar cell (toe to brainstem)
Kandel.
Cytosol
Cytoplasm refers to the jelly-like material with organelles in
it.
If the organelles were removed, the soluble part that would
be left is called the cytosol. It consists mainly of water with
dissolved substances such as amino acids in it.
Presentation By: Mahendra
Kandel.
Presentation By: Mahendra
Kandel.
Presentation By: Mahendra
Kandel.
Plasma (cell) membrane
STRUCTURE
• This is the boundary between
the cell cytoplasm & the
environment
• Is partially permeable
• Made up 45% protein & 45%
phospholipids with the
remaining 10% cholesterol,
glycoprotein & glyolipids
FUNCTION
• Controls movement of
substances in & out of the cell
• Forms a recognition site so
that the body’s immune system
can recognize its own cells
• Acts as a receptor site for the
attachment of specific
hormones and
neurotransmitters.
Presentation By: Mahendra
Kandel.
The fluid mosaic model describes the structure of the plasma
membrane.Different kinds of cell membrane models have been
proposed, and one of the most useful is the Fluid-mosaic model. In
this model the membrane is seen as a bilayer of phospholipids in
which protein molecules are embedded.
An illustration of the Fluid
mosaic model
Presentation By: Mahendra
Kandel.
Channels/pores- A channel in the cell's plasma membrane. This channel
is made up of certain proteins whose function is to control the movement
of food and water into the cell. These channels are made up of certain
proteins.
Presentation By: Mahendra
Kandel.
Exocytosis
Fig 2.17
Presentation By: Mahendra
Kandel.
Presentation By: Mahendra
Kandel.
Vesicles- This term literally means "small vessel". This organelle helps
store and transport products produced by the cell.
The vesicles are the transport and delivery vehicles like our mail
and Federal Express trucks. Some vesicles deliver materials to parts of
the cell and others transport materials outside the cell in a process called
exocytosis
Presentation By: Mahendra
Kandel.
Figure 7-5 Plant and Animal Cells
Animal Cell
Section 7-2
Cytoplasm
Nucleolus
Nucleus
Go to
Section:
Cell Membrane
Presentation By: Mahendra
Kandel.
Eukaryotic Cell Organelles and
Function
1. Nucleus
– Nickname: “The Control Center”
– Function: holds the DNA
– Parts:
1. Nucleolus: dark spot in the middle of the
nucleus that helps make ribosomes
Presentation By: Mahendra
Kandel.
Nucleus- The nucleus is the control center of the cell. It is the largest
organelle in the cell and it contains the DNA of the cell. The DNA of all
cells is made up of chromosomes.
DNA (Deoxyribonucleic Acid) contains all the information for cells to
live, perform their functions and reproduce.
Inside the nucleus is another organelle called the nucleolus. The
nucleolus is responsible for making ribosomes.
The circles on the surface of the nucleus are the nuclear pores. These are
By: Mahendra
where ribosomes, and other Presentation
materials
move in and out of the cell.
Kandel.
STRUCTURE
•
•
•
•
•
•
Nucleus, Nucleolus &
Nuclear envelope
Largest organelle in the cell
FUNCTION
(10um diameter)
Surrounded by a nuclear
membrane / envelope
• Acts as the control centre of
Double membrane – outer is
the cell through the production
continuous with the ER
of mRNA and protein synthesis
Nuclear pores in the membrane
• Retains the genetic material in
allow the passage of large
molecules in & out (eg
the cell in the form of DNA /
messengerRNA)
chromosomes
Material inside the nucleus is
• Manufactures ribosomal RNA
called nucleoplasm – this
(rRNA) & ribosomes
contains chromatin which makes
up the DNA of the cell – in nondividing cells it is spread out and • Starts the process of cell
division
during cell division it condenses
to form the chromosomes
A spherical structure called the
nucleolus is found in the nucleus
– this makes ribosomal RNA and
assembles the ribosomes.
Presentation By: Mahendra
Kandel.
Figure 7-5 Plant and Animal Cells
Animal Cell
Section 7-2
Cytoplasm
Ribosomes
Nucleolus
Nucleus
Go to
Section:
Cell Membrane
Presentation By: Mahendra
Kandel.
Eukaryotic Cell Organelles and
Function
2. Ribosomes
– Function: makes proteins
– Found in all cells, prokaryotic and eukaryotic
Presentation By: Mahendra
Kandel.
Ribosomes- Organelles that help in the synthesis of proteins. Ribosomes
are made up of two parts, called subunits.
They get their names from their size. One unit is larger than than the
other so they are called large and small subunits.
Both these subunits are necessary for protein synthesis in the cell. When
the two units are docked together with a special information unit called
messenger RNA, they make proteins.
Some ribosomes are found in the cytoplasm, but most are attached to the
endoplasmic reticulum. While attached to the ER, ribosomes make
proteins that the cell needs and also ones to be exported from the cell for
By: Mahendra
work elsewhere in the body.Presentation
Kandel.
Ribosomes
STRUCTURE
• Small dense structures
found in huge numbers.
• Can be attached to the
rough ER of floating in
the cytoplasm.
• Are about 20 – 25 nm in
diameter in eukaryotic
cells and slightly smaller
in prokaryotic cells
• Made up from two sub
units
FUNCTION
• Synthesize proteins
• Synthesize enzymes
Presentation By: Mahendra
Kandel.
Eukaryotic Cell Organelles and
Function
3. Endoplasmic Reticulum (ER)
– Nickname: “Roads”
– Function: The internal delivery system of
the cell
Presentation By: Mahendra
Kandel.
Figure 7-5 Plant and Animal Cells
Animal Cell
Section 7-2
Cytoplasm
Nucleolus
Ribosomes
Nucleus
Cell Membrane
Smooth
Endoplasmic
Reticulum
Rough
Endoplasmic
Reticulum
Go to
Section:
Presentation By: Mahendra
Kandel.
Endoplasmic reticulum (ER)- It is a network of membranes
throughout the cytoplasm of the cell. There are two types of ER.
When ribosomes are attached it is called rough ER and smooth ER
when there are no ribosomes attached.
The rough endoplasmic reticulum is where most protein synthesis
occurs in the cell. The function of the smooth endoplasmic reticulum is
to synthesize lipids in the cell. The smooth ER is also helps in the
detoxification of harmful substances
in Mahendra
the cell.
Presentation By:
Kandel.
Endoplasmic Reticulum
STRUCTURE
• Complex system of sheet like
double membranes continuous
with the nuclear membrane
• Fluid filled spaces/sacs
between the membranes
called CISTERNAE which
allow materials to be
transported through cell
• Two types of ER –
– smooth – has no ribosomes
attached(SER)
– rough – has ribosomes
attached (RER)
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FUNCTION
Forms an extensive transport
system
Site of protein synthesis
(Rough ER)
Site of lipid, steroid and
carbohydrate synthesis
(smooth ER)
Stores and transports these
materials
Presentation By: Mahendra
Kandel.
Endoplasmic Reticulum
– 2 Types:
1.Rough ER:
– Rough appearance because it has ribosomes
– Function: helps make proteins, that’s why it
has ribosomes
2.Smooth ER:
– NO ribosomes
– Function: makes fats or lipids
Presentation By: Mahendra
Kandel.
Figure 7-5 Plant and Animal Cells
Animal Cell
Section 7-2
Cytoplasm
Ribosomes
Nucleolus
Nucleus
Cell Membrane
Smooth Endoplasmic
Reticulum
Rough Endoplasmic
Reticulum
Golgi Complex
Go to
Section:
Presentation By: Mahendra
Kandel.
Eukaryotic Cell Organelles and
Function
4. Golgi Complex
– Nickname: The shippers
– Function: packages, modifies, and
transports materials to different location
inside/outside of the cell
– Appearance: stack of pancakes
Presentation By: Mahendra
Kandel.
Golgi complex- It is organelle in the cell that is
responsible for sorting and correctly shipping the
proteins produced in the ER.
Just like our postal packages which should have a
correct shipping address, the proteins produced in
the ER, should be correctly sent to their respective
address.
In the cell, shipping and sorting done by the Golgi
complex. It is a very important step in protein
synthesis.
If the Golgi complex makes a mistake in shipping
the proteins to the right address, certain functions in
the cell may stop.
Presentation By: Mahendra
Kandel.
Golgi apparatus
•
•
•
•
STRUCTURE
Formed from small pieces of
rough ER which form small
vesicles which join to make a
Golgi body
Chemicals made in the ER
collect in the Golgi body where
they are modified
Small vesicles can then be
‘pinched’ off the Golgi body
carrying new chemicals away
which are secreted when the
vesicle reaches the cell
membrane
Some of the vesicles become
lysosomes
•
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FUNCTION
Assembling glycoproteins
(such as mucin) by combining
carbohydrate and protein
Transporting and storing lipids
Formation of lysosomes
Producing digestive enzymes
Presentation By: Mahendra
Kandel.
Figure 7-5 Plant and Animal Cells
Animal Cell
Section 7-2
Cytoplasm
Nucleolus
Ribosomes
Nucleus
Cell Membrane
Smooth Endoplasmic
Reticulum
Rough Endoplasmic
Reticulum
Golgi Bodies
Go to
Section:
Presentation By: Mahendra
Kandel.
Eukaryotic Cell Organelles and
Function
5. Lysosomes: circular, but bigger than
ribosomes)
– Nickname: “Clean-up Crews”
– Function: to break down food into particles
the rest of the cell can use and to destroy
old cells
Presentation By: Mahendra
Kandel.
Lysosomes
STRUCTURE
• Small vacuoles formed when
small pieces of Golgi body are
pinched off
• Contain hydrolytic enzymes
which digest materials in the
cell
FUNCTION
• Release enzymes which
destroy worn out organelles
• Digest material taken into the
cell (eg white blood cells which
have engulfed a bacterium) –
phagocytosis
• Release enzymes to the
outside of the cell which digest
material around the cell –
exocytosis
• Completely break down cells
after they have died – autolysis
Presentation By: Mahendra
Kandel.
Figure 7-5 Plant and Animal Cells
Animal Cell
Section 7-2
Cytoplasm
Nucleolus
Ribosomes
Nucleus
Cell Membrane
Mitochondria
Smooth Endoplasmic
Reticulum
Rough Endoplasmic
Reticulum
Golgi Bodies
Presentation By: Mahendra
Kandel.
Eukaryotic Cell Organelles and
Function
6. Mitochondria
– Nickname: “The Powerhouse”
– Function: Energy formation
•
Breaks down food to make ATP
– ATP: is the major fuel for all cell activities that
require energy
Presentation By: Mahendra
Kandel.
Mitochondria
Mitochondria are membrane-enclosed organelles distributed through
the cytosol of most eukaryotic cells. Their main function is the
conversion of the potential energy of food molecules into ATP.
Every type of cell has a different amount of mitochondria.. There are
more mitochondria in cells that have to perform lots of work, for
example- your leg muscle cells, heart muscle cells etc. Other cells
need less energy to do their work and have less mitochondria.
Presentation By: Mahendra
Kandel.
Mitochondria
STRUCTURE
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Relatively large organelle
Rod/sausage shaped – 1um –
5um
Have a double membrane
– The outer controls the entry
& exit of materials
– Inner has many folds called
cristae
Surface of each crista is
covered with stalked particles
where ATP is made
Mitochondria are filled with a
jelly like matrix
The matrix contains proteins,
lipids, ribosomes and loops of
DNA
Mitochondria can replicate
themselves when the cell
divides
FUNCTION
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Site of aerobic respiration
(Krebs cycle & oxidative
phosphorylation)
Responsible for the production
of energy rich ATP molecules
The numbers of mitochondria
reflect the metabolic activity of
the cell – so large numbers are
found in muscle and liver cells
Presentation By: Mahendra
Kandel.
Presentation By: Mahendra
Kandel.
Animal Cell
Cytoplasm
Nucleolus
Ribosomes
Nucleus
Cell Membrane
Mitochondria
Smooth Endoplasmic
Reticulum
Rough Endoplasmic
Reticulum
Golgi Bodies
Presentation By: Mahendra
Kandel.
Centrosome
The centrosome, also called the "microtubule organizing center", is an
area in the cell where microtubles are produced.
Within an animal cell centrosome there is a pair of small organelles, the
centrioles, each made up of a ring of nine groups of microtubules. There
are three fused microtubules in each group.
The two centrioles are arranged such that one is perpendicular to the
other.
During animal cell division, the centrosome divides and the centrioles
replicate (make new copies). The result is two centrosomes, each with its
own pair of centrioles. The two centrosomes move to opposite ends of
the nucleus, and from each centrosome, microtubules grow into a
"spindle" which is responsible for separating replicated chromosomes
into the two daughter cells. Presentation By: Mahendra
Kandel.
Presentation By: Mahendra
Kandel.
•cilia are thread-like projections of certain cells that beat in a
regular fashion to create currents that sweep materials along;
Presentation By: Mahendra
Kandel.
Flagella may extend to the rear of a cell and push it forward by snakelike
wriggling, or stick out in front and draw it along.
We humans possess both flagella and cilia. Each sperm cell is propelled
by a trailing flagellum that accelerates the little torpedo forward in its
quest to fertilize an egg.
Presentation By: Mahendra
Kandel.
Some abbreviations
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nm: nano metre ( 10 to the power -9 metre )
um: micro metre ( 10 to the power -6 metre)
mm: milli metre (10 to the power -3 metre)
1 angstrom =10 to the power -7 mm.
1 micron (u)= 10 to the power -3 mm
1 millimicron (mu)= 10 to the power -6mm
Presentation By: Mahendra
Kandel.
Presentation By: Mahendra
Kandel.