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The Interactive Cell
Version 1.3
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Cell Anatomy
Cytoplasm
Cell Physiology
Cell Membrane
Mitochondrion
Centrosome/ centrioles
Movement across
the cell membrane
Protein
Synthesis
Cytoskeleton
Endoplasmic reticulum
Endoplasmic
Reticulum
Cell
Membrane
Enzyme
Function
Mitochondrion
Golgi Complex
Lysosome
Energy
Production
Lysosome
Nucleus
Nucleolus
Cell Division
Mitochondrion
Endoplasmic reticulum
Nucleolus
Ribosomes
Golgi Complex
Nucleus
Exocytosis
Centrosome
Peroxisome
Protoplasm
Ribosome
Peroxisome
Cilia
10 microns
Endocytosis
Nucleolus
- Contain RNA
- May be several in the cell
nucleus
Ribosomes are assembled from
- Ribosomes
RNA and protein
- Ribosomes then move into the cytoplasm
through the nuclear pores and begin
protein
Protein synthesis.
Synthesis
Ribosomes
Manufacturing protein
Protein
 manufacture
 can float free in the
cytoplasm
(these make soluble proteins)
 can attach to Endoplasmic Reticulum (ER)
Rough ER
making Rough
ER. Proteins made here are
transported away for use elsewhere in the
cell or for secretion.
Endoplasmic Reticulum
- membranous network
within the cell cytoplasm
Nuclear
Membrane
Click here to
find out about
membranes
There are two types of
Endoplasmic Reticulum :
Rough ER
Smooth ER
Rough
Endoplasmic
Reticulum
Ribosomes
Smooth Endoplasmic
Reticulum
Smooth Endoplasmic
Reticulum
 Channels that extend from Rough ER
 contains enzymes that synthesize lipids
such as cholesterol, steroid hormones and
fat for transport
 In some muscle smooth ER stores calcium
ions
Rough Endoplasmic Reticulum
 Membrane channels
Ribosomes make proteins
 Ribosomes
 which are assembled in
tips of the channels
(cisternae) bud off in
transport vesicles
 vesicles for secretion travel
to the Golgi
GolgiComplex
Complex
Golgi Complex
 Flattened membranes
forming a stack
 Proteins formed by the
Rough Endoplasmic
Reticulum are sorted and
packaged into vesicles
 Vesicles can be for
exocytosis
secretion (see exocytosis)
or internal use (e.g.
lysosomes)
Lysosomes
Mitochondria
- Energy Producing organelles
that perform cell respiration.
Mitochondria vary in shape from
tiny threadlike organelles to
classic bean shaped structures.
They have two membranes - the
inner one is highly folded into
cristae, which hold enzymes
used in cell respiration.
Mitochondria contain some DNA
and can replicate themselves.
Mitochondria
Ion Pumps
Protein
Synthesis
Cell
Division
ATP
ATP
 Adenosine Triphosphate
 contains energy
 gives up energy to power
Adenosine
chemical reactions
 disintegrates into ADP and a
free P
 reassembled into ATP by
cell respiration processes.
cell respiration
Tri = 3
Phosphates
Substrate molecules A&B:
(energy is required to join
them together)
AB
A
B
synthesis
Click here to find out
more about molecules
moving through the
cell membrane.
Cell Membrane
Carbohydrates
ein
Protein
Phospholipid
bilayer
bilayer
Cytoskeleton
The Phospholipid bilayer
Water (polar)
Phosphate heads
(hydrophilic)
Phospholipid
Phospholipid
Bilayer
Lipid tails
(hydrophobic)
Intermediate Filaments are another strong
The Cell Skeleton
Microfilaments
Thin protein
strands (actin,
stained green)
crosslinked and
braced, these
help hold the
cell in shape.
(e.g. supporting
the cell
membrane)
- they also link
with motor
proteins (e.g.
Mysosin) to
help create
movement.
protein strand that supports the inside of the cell
like guy wires.
For Microtubules, click the next  button
Microtubules
 Hollow protein tubes
made of tubulin
 Microtubules form the
major support
framework in the cell
 special arrangements of
microtubules form the
- Centrioles
- Cilia
Together Microtubules, Microfilaments and Intermediate fibres form the
Cyto, or cell, skeleton.
Endocytosis
Using endocytosis large particles can be
engulfed and brought into the cell.
There are two main forms of endocytosis:
Phagocytosis
Pinocytosis
Phagocytosis
Pinocytosis
Diagram
golgi
vesicles
complex
Vesicle
Electron Microscope
photograph
Exocytosis
Secretions are wrapped in membranous
sacs called vesicles
- produced by the golgi complex.
Vesicles transported to the cell
membrane can fuse with it so that
contents are expelled to the outside
into the interstitial (tissue) fluid.
Cells release hormones and other
secretions (mucus, enzymes) in this
way.
Lysosomes
Membranous packets
of enzymes that
can digest nearly
anything.
Peroxisomes
 Tiny membranous
mitochondrion
Electron Microscope view approx. x 25000
sacs
 Contain powerful
enzymes
enzymes
 These utilise
oxygen (O2) to
oxidise toxic
compounds such
as alcohol and free
radicals.
Centrioles
 Bundles of short
microtubules
microtubules
 occur in pairs (Centrosome)
 the Centrosome duplicates
before cell division
 microtubule rods extend
and attach to
chromosomes during
cell
cell division
division
Cilia
 Small, hairlike projections of cell
membrane
 Produce movement at the cell surface
microtubule rods
 Reinforced with pairs of microtubule
that slide over each other to create
movement
The Nucleus
Nucleus
Nucleolus
With Chromosomes
Nuclear membrane
The Nuclear Membrane (or Envelope)
Two layers of membrane
(each a phospholipid
bilayer)
The outer layer is
continuous with the
Endoplasmic Reticulum
Reticulum
Endoplasmic
Nuclear pores are holes in
the nuclear membrane
that allow large
molecules through
Electron Microscope view
approx. 40,000x magnified
Lipids
Largely Nonpolar molecules that normally
repel water but dissolve in solvents
such a chloroform, ether and alcohol.
 2 key types of Lipid:
 1) Those based on carbon rings
Steroids
 2) Those based on carbon chains:
Fats
STEROIDS
Based on the four carbon ring
Cholesterol:
used in  Cell membrane structure,
 Hormone manufacture
Fats and Fatty Acids
More about
Saturation
of fats
Triglycerides
(neutral fat)
Found mostly in
adipose (fat)
cells as a way of
storing energy.
Fat is also useful as
insulation and
padding……
But are insoluble in
water - though
triglycerides can be
modified into
Phospholipids
Movement across the cell membrane
Passive processes
Active processes
- no energy used for transporting
material across the cell membrane
- Energy is used for transporting
material across the cell membrane
Diffusion
Osmosis
Facilitated
Diffusion
Bulk
Transport
(using vesicles)
Phagocytosis
Pinocytosis
Exocytosis
What the heck
was ATP again?
Active
Transport
Solute
pumps
ENZYMES
Active Sites
This yellow structure
represents a vitamin:
click here to find out why vitamins are important:
Enzymes are
made of
protein.
protein
They are
Biological
catalysts.
The lock and key
model:
The Sodium/ Potassium pump
 The pump is activated
by 3 sodium ions
entering the protein
channel.
 ATP is required for the
pump to work
ATP
Na+
K+
The Sodium/ Potassium pump
 ATP gives up its energy.
 The pump proteins
ADP
Na+
K+
P
change shape, expelling
sodium ions into the
extracellular fluid.
 Sodium ions are
pumped against their
concentration gradient
The Sodium/ Potassium pump
 Potassium ions
outside the cell then
enter the pump
ADP
Na+
K+
P
The Sodium/ Potassium pump
 Two Potassium ions
Na+
K+
are pumped to the
inside of the cell.
 Each transport pump
moves specific ions
across the cell
membrane - others
include Ca2+ or H+
Back to
membrane
transport
Review
Na+k+
pump
Diffusion
 Substances that are free to move will
spread out evenly into a medium they
will mix with.
Container with a high
concentration of molecules
Diffusion
 Substances that are free to move will
spread out evenly into a medium they
will mix with.
Diffusion
 Substances that are free to move will
spread out evenly into a medium they
will mix with.
Diffusion
Water soluble chemicals that are also
lipid soluble can diffuse through cell
membranes e.g. cholesterol, alcohol
But if they are not water nor lipid
soluble they cannot penetrate
the lipid based cell membrane
Cell
Review
Diffusion
Water can also diffuse freely through protein channels
Back to
in the cell membrane (See Osmosis)
movement across
the membrane
Osmosis
Diffusion of water across a selectively permeable membrane
- Larger solute molecules cannot penetrate the membrane
Water moves from
where it is in higher
concentration …..
A stronger solution
with lots of solute
in it thus appears to
“suck” water into it
through the
membrane
.. Click the left
mouse button to see
the effects of osmosis
in this demonstration:
Selectively permeable
membrane
More water
less solute
.. to where it is
less concentrated
More solute
less water
Osmosis creates
enough pressure
to raise the height
of the fluid :
Osmotic Pressure
Osmosis and Cells
A cell with its selectively permeable membrane is quickly affected
by osmotic pressure changes. It is important for body fluid
concentrations to be maintained within narrow limits to stop
cells shrinking or swelling and bursting.
A salt solution that develops the same osmotic pressure as normal body fluids
is 0.9% (0.9 grams of NaCl per 100mls water). This is isotonic or medical saline.
Click the left mouse button
to see the effects of putting
a cell into a hypertonic solution:
Water is sucked out
Cells
for testing:
cell
shrinks
Solutions:
Hypertonic: High salt concentration
Click again to see the effects of putting
a cell into a hypotonic solution:
Water diffuses in
-swells and bursts
Hypotonic: Low salt concentration
Review
osmosis
Back to
movement
across
the membrane
Facilitated Diffusion
 Special protein channels
Protein Channel
allow certain chemicals to
diffuse through the cell
membrane along their
concentration gradients
(High to Low)
 There are different channels
each with a slightly different
shape for each substance for example glucose, and
different ions such as Mg2+
Amino Acids
 Amino acids are protein subunits.
 A central carbon has two groups added to it:
A nitrogen based
amine group
Different amino acids
have different side
groups:
There are 24 different side groups - some
attract water, others repel it - giving each
amino acid different characteristics.
A carboxyl group which
acts as a weak acid
CH
H 3
H
C O H
N C C O H
H
H
O
H O
alanine
glycine
Peptide bond
- links amino acids
Amino acids can link acid to amine group if lined up properly this is the basis of protein structure.
H+
Proteins
amino acids
acids .
Proteins are formed from chains of amino
Short chain proteins can be called peptides. Long
chains of amino acids (100+) we call proteins but all amino acid chains belong to the protein class.
Key:
Histadine
Alanine
Leucine
Glutamine
Lysine
Tyrosine
- there are 24 different
amino acids, each with a
different side chain.
Protein Structure
 Each protein is made by linking a specific sequence
of amino acids linking together through peptide
Aminoacid
acid page if you haven’t yet)
bonds (see the amino
As the amino acid chain forms the side groups will
attract or repel each other and the surrounding
polar water molecules.
As long as conditions stay constant
(e.g. homeostatic temperature and pH)
a protein of a particular amino acid
sequence (primary structure) will always
bend
(Secondary structure)
coil
wrap
the same way
forming the same shape.
(Tertiary structure)
Protein levels of structure
To find out how the
amino acid sequence
is determined:
Click here
to go to
Protein Synthesis
SEQUENCE
DETERMINES
SHAPE,
SHAPE
DETERMINES
FUNCTION
For an illustration, see
enzyme function
Chromosomes and DNA
DNA
Deoxyribose Nucleic Acid
The molecule of inheritance
- passed on from cell to cell
through cell division processes
- is formed into chromosomes by
coiling around proteins called
histones
- Uncoiled a small piece of DNA is
seen to be in the form of a
DOUBLE HELIX and linked by
base pairs (next slide).
DNA base pairing
Sugar phosphate “backbone”
linked by bases that pair:
Adenine
Thymine
Cytosine
Guanine
How DNA controls the cell
C G
A T
C
G
T
A
How DNA replicates and gets
passed on to new cells
Protein Synthesis
Part 1: Transcription
DNA is copied using ribose
A section of DNA
nucelic acids to form a strand of mRNA.
The mRNA breaks away from the DNA and
moves through nuclear pores to the
cytoplasm, where it is used as a template
to make protein.
In RNA strands, the
base Thymine is not
used -Uracil takes it’s
place. Base pairing is
G-C
U-A
Translation
Each group of three bases
that codes for an amino acid
is called a triplet code in DNA e.g. AGT
- a Codon in mRNA
e.g. UCA
- and an Anticodon in tRNA e.g. AGU
With four bases, there are 64 possible triplets.
With only 24 different amino acids, there are often
2 or more triplets coding for an amino acid.
The Second part of
protein synthesis
Transfer RNA has just 3 bases.
It attaches to an amino acid which amino acid depends on
the 3 bases:
AAU attaches to leucine
CGA or
CGG attaches to alanine
etc
Nucleus
mRNA leaves the nucleus
and attaches to a ribosome
mRNA
Ribosome in the cytoplasm
Translation
(2)
The ribosome lines up the
tRNA molecules with
their amino acids.
Translation
(3)
When the amino acids are
lined up beside each
other they will form a
peptide bond.
Translation
(4)
After the first peptide bond
formation the first amino acid
detatches from it’s tRNA.
The tRNA then breaks away to
find another amino acid in the
cytoplasm.
The ribosome moves along the
mRNA strand, and another
tRNA lines up another amino
acid…….
Translation
(5)
After each peptide bond forms
the ribosome moves along
and lines up the next tRNA
with its amino acid.
The amino acid chain (protein)
grows with the amino acid
sequence determined by the
base sequence - which was
determined originally by the
DNA base sequence.
Review the Protein Synthesis
section again?
In proteins, the amino acid sequence determines the shape of the protein the shape of the protein will determine it’s function:
Find out about
Protein and its uses
Cell Division
To duplicate itself, a cell first has
to duplicate it’s DNA.
This occurs when all the DNA is
unwound in the nucleus of
the cell -
DNA wound into
a chromosome
DNA
(DNA is often pictured wound up in the
form of chromosomes, but they spend
little time in this form. Most of the time
DNA spends unwound so that protein
synthesis can occur, and the DNA winds
up around histone proteins to form
visible chromosomes so the DNA can be
pulled apart during cell division).
Cell Division
Centrosome with a pair of centrioles
- protein tubules that will pull apart
chromosomes during the cell division
DNA wound into
a chromosome
Nucleus with DNA unwound
( Between cell divisions = Interphase)
Centrioles
Cell Division - DNA Replication
Free nucleotides:
DNA
Chromosomes and DNA
DNA unzipped by
enzymes:
Free nucleotides
then attach to
the exposed
bases to
replicate the
original DNA.
Base sequence is
maintained
due to base
pairing
C-G; A-T
Cell Division
Chromosome spread: 46 in total
Chromosome
Chromatid
Chromatid
Centromere
(holds chromatids together)
DNA molecules
The two DNA
then coil around their
histone proteins and form
the visible chromosome.
Each chromosome has
two chromatids, each
containing a complete
DNA molecule .
What is a Karyotype?
On to
mitosis
Cell Division - Mitosis
When DNA has been duplicated, the cell can then actually divide
Prophase - chromosomes become visible
centrioles form 2 pairs and move apart
nuclear membrane breaks down
Cell Division - Mitosis
When DNA has been duplicated, the cell can then actually divide
Metaphase - chromosomes line up across the cell and centriole tubules extend
to form the spindle apparatus (attaches to centromeres)
Diagram shows only 2 pairs of chromosomes
for clarity: humans have 23 pairs.
Cell Division - Mitosis
When DNA has been duplicated, the cell can then actually divide
Anaphase - chromatids (each containing a complete DNA molecule) are pulled apart
Cell Division - Mitosis
When DNA has been duplicated, the cell can then actually divide
Telophase - chromatids unwind, nucleus reforms
Cytokinesis occurs - the acutal separation of the cell into two new identical cells
Go over mitosis again
Cell Division
Microtubules and Centrioles
More about DNA and chromosomes
Maximum rate of
cell division
rate is about
once every
twelve hours once a day is
more typical.
The mitosis part
takes about an
hour or two.
Karyotype
Chromosomes arranged
in pairs from largest to
smallest (22 autosome
pairs)
- and the sex pair of
chromosomes, pair 23
XY for males (shown)
XX for females
Chromosome bands
Special lab techniques
can show different
patterns on
chromosomes to help
identify particular
chromosomes.
Carbohydrates
These simple sugars are
all variations on C6H12O6
They are all ISOMERS.
There are other types of
simple sugars in the body
as well - for example the
Ribose 5 carbon sugars
found in nucleic acids.
Made of C, H, O
Carbohydrates are
made of base
units called
simple sugars or
monosaccharides
The commonest
example in the
body is the 6
carbon sugar
glucose.
-OH groups make
the sugars water
soluble.
Di- and Poly- saccharides
Disachharides have two simple sugars
joined
Sucrose = Glucose + Fructose
Lactose = Glucose + Galactose
Maltose = Glucose + Glucose
Polysaccharides of importance to the
body are made of chains of glucose:
Protoplasm
 Descriptive term for the souplike
contents of a cell, including the fluids of
the nucleoplasm (inside the nucleus)
and cytoplasm (outside the nucleus)
H
Li
He
Be
B
C
N
O
F
Ne
Na Mg
Al
Si
P
S
Cl
Ar
K
Ca