Download The Cell

BI 5103
FISIOLOGI TERINTEGRASI
(Integrative Physiology)
Core Principle 4 : The Cell
(Konsep Inti 4 : Sel)
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Why the Cell ?
The cell is the basic unit of life.
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The cell is the smallest, selfreplicating unit
of integrated function.
A multicellular organism is an organized
structure made up of different cells, with
each cell having some properties in
common with other cells in the organism
and each cell having some specialized
structures and functions.
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
An animal cell
Smooth
endoplasmic
reticulum
Nucleus
Rough
endoplasmic
reticulum
Flagellum
Not in most
plant cells
Lysosome
Centriole
Ribosomes
Peroxisome
Golgi
apparatus
Microtubule
Cytoskeleton
Plasma membrane
Intermediate
filament
Microfilament
Mitochondrion
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Nucleus
Rough
endoplasmic
reticulum
Ribosomes
Smooth
endoplasmic
reticulum
Golgi
apparatus
Microtubule
Not in
animal
cells
Central
vacuole
Intermediate
filament
Cytoskeleton
Chloroplast
Microfilament
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
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Sub Topic
A.The cell membrane contains the contents of the cell and
determines what can enter and leave the cell.
B.The internal constituents and state of the cell are different
than the extracellular environment.
C. Although all cells have the same DNA, not all genes are
expressed in every cell.
D. As a consequence, cells have many common functions but
also many specialized functions.
E.The organism is a collection of cooperating cells, with each
cell type contributing its special functions to the
“economy” of the organism.
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A.The cell membrane contains the
contents of the cell and determines
what can enter and leave the cell.
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Figure 5.1
CYTOPLASM
Enzymatic
activity
Fibers of
extracellular
matrix (ECM)
Phospholipid
Cholesterol
Cell-cell
recognition
Receptor
Signaling
molecule
Transport
Attachment to the cytoskeleton
and extracellular matrix (ECM)
Signal
transduction
ATP
Intercellular
junctions
Glycoprotein
Microfilaments
of cytoskeleton
CYTOPLASM
Membranes are fluid mosaics of lipids and proteins
with many functions
Membrane proteins perform many functions.
1. Some proteins help maintain cell shape and
coordinate changes inside and outside the cell
through their attachment to the cytoskeleton and
extracellular matrix.
2. Some proteins function as receptors for chemical
messengers from other cells.
3. Some membrane proteins function as enzymes.
© 2012 Pearson Education, Inc.
Membranes are fluid mosaics of lipids and proteins
with many functions
4. Some membrane glycoproteins are involved in cellcell recognition.
5. Membrane proteins may participate in the
intercellular junctions that attach adjacent cells to
each other.
6. Membranes may exhibit selective permeability,
allowing some substances to cross more easily than
others.
© 2012 Pearson Education, Inc.
Many cell organelles are related through
the endomembrane system

The endomembrane system is a collection of
membranous organelles
◦ These organelles manufacture and distribute cell
products
◦ The endomembrane system divides the cell into
compartments
◦ Endoplasmic reticulum (ER) is part of the
endomembrane system
◦ (nuclear envelope, ER, Golgi apparatus, lysosomes,
vacuoles, and the plasma membrane)
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Rough endoplasmic reticulum makes
membrane and proteins


The rough ER manufactures membranes
Ribosomes on its surface produce proteins
Transport vesicle
buds off
4
Ribosome
Sugar
chain
1
3
Secretory
(glyco-) protein
inside transport
vesicle
Glycoprotein
2
ROUGH ER
Polypeptide
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Smooth endoplasmic reticulum has a
variety of functions
Smooth ER synthesizes lipids
 In some cells, it regulates carbohydrate
metabolism and breaks down toxins and drugs

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SMOOTH ER
ROUGH
ER
Nuclear
envelope
Ribosomes
SMOOTH ER
ROUGH ER
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The Golgi apparatus finishes, sorts,
and ships cell products

The Golgi apparatus consists of stacks of
membranous sacs
◦ These receive and modify ER products, then send
them on to other organelles or to the cell membrane
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
The Golgi apparatus
Golgi apparatus
Golgi
apparatus
“Receiving” side of
Golgi apparatus
Transport
vesicle
from ER
New
vesicle
forming
“Shipping”
side of Golgi
apparatus
Transport vesicle
from the Golgi
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Lysosomes digest the cell’s food and
wastes

Lysosomes are
sacs of digestive
enzymes budded
off the Golgi
LYSOSOME
Nucleus
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
Lysosomal enzymes
– digest food
– destroy bacteria
– recycle damaged organelles
– function in embryonic development in animals
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Rough ER
Transport vesicle
(containing inactive
hydrolytic enzymes)
Plasma
membrane
Golgi
apparatus
Engulfment
of particle
Lysosome
engulfing
damaged
organelle
“Food”
LYSOSOMES
Food
vacuole
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Digestion
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B.The internal constituents and state
of the cell are different than the
extracellular environment.
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Passive transport is diffusion across a membrane
with no energy investment

Diffusion is the tendency of particles to spread
out evenly in an available space.
◦ Particles move from an area of more concentrated
particles to an area where they are less
concentrated.
◦ This means that particles diffuse down their
concentration gradient.
◦ Eventually, the particles reach equilibrium where the
concentration of particles is the same throughout.
© 2012 Pearson Education, Inc.
Passive transport is diffusion across a membrane
with no energy investment
Diffusion across a cell membrane does not
require energy, so it is called passive
transport.
 The concentration gradient itself represents
potential energy for diffusion.

© 2012 Pearson Education, Inc.
Molecules of dye
Membrane
Pores
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
Osmosis is the diffusion of water across a membrane
One of the most important substances that
crosses membranes is water.
 The diffusion of water across a selectively
permeable membrane is called osmosis.

© 2012 Pearson Education, Inc.
Osmosis is the diffusion of water across a membrane

If a membrane permeable to water but not a
solute separates two solutions with different
concentrations of solute,
◦ water will cross the membrane,
◦ moving down its own concentration gradient,
◦ until the solute concentration on both sides is
equal.
© 2012 Pearson Education, Inc.
Lower
Higher
concentration concentration
of solute
of solute
Equal
concentrations
of solute
H2O
Solute
molecule
Selectively
permeable
membrane
Water
molecule
Solute molecule
with cluster of
water molecules
Osmosis
Water balance between cells and their
surroundings is crucial to organisms
Tonicity is a term that describes the ability of a
solution to cause a cell to gain or lose water.
 Tonicity mostly depends on the concentration of
a solute on both sides of the membrane.

© 2012 Pearson Education, Inc.
Water balance between cells and their
surroundings is crucial to organisms

How will animal cells be affected when placed
into solutions of various tonicities? When an
animal cell is placed into
◦ an isotonic solution, the concentration of solute is
the same on both sides of a membrane, and the cell
volume will not change,
◦ a hypotonic solution, the solute concentration is
lower outside the cell, water molecules move into
the cell, and the cell will expand and may burst, or
◦ a hypertonic solution, the solute concentration is
higher outside the cell, water molecules move out
of the cell, and the cell will shrink.
© 2012 Pearson Education, Inc.
Water balance between cells and their
surroundings is crucial to organisms

For an animal cell to survive in a hypotonic or
hypertonic environment, it must engage in
osmoregulation, the control of water balance.
© 2012 Pearson Education, Inc.
Water balance between cells and their
surroundings is crucial to organisms

The cell walls of plant cells, prokaryotes, and
fungi make water balance issues somewhat
different.
◦ The cell wall of a plant cell exerts pressure that
prevents the cell from taking in too much water and
bursting when placed in a hypotonic environment.
◦ But in a hypertonic environment, plant and animal
cells both shrivel.
© 2012 Pearson Education, Inc.
Hypotonic solution
H2O
Isotonic solution
Hypertonic solution
H2O
H2O
H2O
Animal
cell
Normal
Lysed
Plasma
membrane
H2O
H2O
Shriveled
H2O
Plant
cell
Turgid
(normal)
Flaccid
Shriveled
(plasmolyzed)
Transport proteins can facilitate diffusion
across membranes
Hydrophobic substances easily diffuse across a
cell membrane.
 However, polar or charged substances do not
easily cross cell membranes and, instead, move
across membranes with the help of specific
transport proteins in a process called
facilitated diffusion, which

◦ does not require energy and
◦ relies on the concentration gradient.
© 2012 Pearson Education, Inc.
Transport proteins can facilitate diffusion across
membranes
Some proteins function by becoming a
hydrophilic tunnel for passage of ions or other
molecules.
 Other proteins bind their passenger, change
shape, and release their passenger on the other
side.
 In both of these situations, the protein is specific
for the substrate, which can be sugars, amino
acids, ions, and even water.

© 2012 Pearson Education, Inc.
Transport proteins can facilitate diffusion across
membranes
Because water is polar, its diffusion through a
membrane’s hydrophobic interior is relatively
slow.
 The very rapid diffusion of water into and out of
certain cells is made possible by a protein
channel called an aquaporin.

© 2012 Pearson Education, Inc.
Solute
molecule
Transport
protein
Cells expend energy in the active transport of a solute

In active transport, a cell
◦ must expend energy to
◦ move a solute against its concentration gradient.

The following figures show the four main stages
of active transport.
© 2012 Pearson Education, Inc.
Transport
protein
Solute
1
Solute binding
Transport
protein
P
ADP
Phosphate
attaching
ATP
Solute
1
Solute binding
2
Transport
protein
Solute
1
Solute binding
2
P
ATP
ADP
Phosphate
attaching
P
Protein
changes shape.
3
Transport
Transport
protein
Solute
1
Solute binding
2
P
ATP
ADP
Phosphate
attaching
P
Protein
changes shape.
3
Transport
Phosphate P
detaches.
4
Protein
reversion
Exocytosis and endocytosis transport large
molecules across membranes

A cell uses two mechanisms to move large
molecules across membranes.
◦ Exocytosis is used to export bulky molecules, such
as proteins or polysaccharides.
◦ Endocytosis is used to import substances useful to
the livelihood of the cell.

In both cases, material to be transported is
packaged within a vesicle that fuses with the
membrane.
© 2012 Pearson Education, Inc.
Exocytosis and endocytosis transport large
molecules across membranes

There are three kinds of endocytosis.
1. Phagocytosis is the engulfment of a particle by
wrapping cell membrane around it, forming a vacuole.
2. Pinocytosis is the same thing except that fluids are
taken into small vesicles.
3. Receptor-mediated endocytosis uses receptors in
a receptor-coated pit to interact with a specific
protein, initiating the formation of a vesicle.
© 2012 Pearson Education, Inc.
Phagocytosis
EXTRACELLULAR
FLUID
Pseudopodium
CYTOPLASM
Food
being
ingested
“Food” or
other particle
Food
vacuole
Pinocytosis
Plasma
membrane
Vesicle
Receptor-mediated endocytosis
Coat protein
Receptor
Plasma membrane
Coated
vesicle
Coated
pit
Specific
molecule
Coated
pit
Material bound
to receptor proteins
Phagocytosis
EXTRACELLULAR
FLUID
Pseudopodium
CYTOPLASM
“Food” or
other particle
Food
vacuole
Food
being
ingested
Pinocytosis
Plasma
membrane
Vesicle
Plasma membrane
Receptor-mediated endocytosis
Coat protein
Plasma membrane
Coated
vesicle
Receptor
Coated
pit
Specific
molecule
Coated
pit
Material bound
to receptor proteins
Cells transform energy as they perform work
Cells are small units, a chemical factory, housing
thousands of chemical reactions.
 Cells use these chemical reactions for

◦ cell maintenance,
◦ manufacture of cellular parts, and
◦ cell replication.
© 2012 Pearson Education, Inc.
C. Although all cells have the same DNA, not all genes
are expressed in every cell.
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Multiple mechanisms regulate gene expression in
eukaryotes
◦ Many possible control points exist; a given gene may
be subject to only a few of these
– Chromosome changes (1)
– DNA unpacking
– Control of transcription (2)
– Regulatory proteins and control sequences
– Control of RNA processing
– Addition of 5’ cap and 3’ poly-A tail (3)
– Splicing (4)
– Flow through nuclear envelope (5)
Copyright © 2009 Pearson Education, Inc.
Multiple mechanisms regulate gene expression in
eukaryotes
◦ Many possible control points exist; a given gene may
be subject to only a few of these
– Breakdown of mRNA (6)
– Control of translation (7)
– Control after translation
– Cleavage/modification/activation of proteins (8)
– Breakdown of protein (9)
Copyright © 2009 Pearson Education, Inc.
NUCLEUS
Chromosome
DNA unpacking
Other changes to DNA
Gene
Gene
Transcription
Exon
RNA transcript
Intron
Addition of cap and tail
Splicing
Tail
mRNA in nucleus
Cap
Flow through
nuclear envelope
mRNA in cytoplasm
CYTOPLASM
Breakdown of mRNA
Translation
Brokendown
mRNA
Polypeptide
Cleavage / modification /
activation
Active protein
Breakdown
of protein
Brokendown
protein
D. As a consequence, cells have
many common functions but also
many specialized functions.
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Differentiation results from the expression of
different combinations of genes
◦ Differentiation involves cell specialization, in both
structure and function
◦ Differentiation is controlled by turning specific sets of
genes on or off
Copyright © 2009 Pearson Education, Inc.
Muscle cell
Pancreas cells
Blood cells
White blood cells help defend the body

White blood cells function both inside and
outside the circulatory system
◦ They fight infections and cancer
Basophil
Eosinophil
Monocyte
Neutrophil
Lymphocyte
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Five major classes of antibodies in human
and other mammals (differs in where it found and
how it works)
IgA
 IgD
 IgE
 IgG
 IgM

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E.The organism is a collection of
cooperating cells, with each cell type
contributing its special functions to the
“economy” of the organism.
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EXAMPLE
The islet of Langerhans in the pancreas is
composed of five different types of cells,
each of which has the common feature of
a membrane across which glucose can be
transported. However, each of these
different cells releases a different
hormone involved, in one way or another,
in the integrated regulation of glucose
metabolism.
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
Hormones produced in the islets of Langerhans are
secreted directly into the blood flow by (at least) five
different types of cells. In rat islets, endocrine cell
subsets are distributed as follows:[3]

Alpha cells producing glucagon (15–20% of total islet
cells)

Beta cells producing insulin and amylin (65–80%)

Delta cells producing somatostatin (3–10%)

PP cells producing pancreatic polypeptide (3–5%)

Epsilon cells producing ghrelin (<1%)
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
It has been recognized that the cytoarchitecture of
pancreatic islets differs between species. In particular,
while rodent islets are characterized by a predominant
proportion of insulin-producing beta cells in the core of
the cluster and by scarce alpha, delta and PP cells in the
periphery, human islets display alpha and beta cells in
close relationship with each other throughout the
cluster.

Islets can influence each other through paracrine and
autocrine communication, and beta cells are coupled
electrically to other beta cells (but not to other cell
types).
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
Paracrine feedback
The paracrine feedback system of the islets of
Langerhans has the following structure :

Insulin: activates beta cells and inhibits alpha
cells

Glucagon: activates alpha cells which activates
beta cells and delta cells

Somatostatin: inhibits alpha cells and beta cells
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Another example ?
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