Download L2 Magnification and cell components

Cells L2 – Magnification and
organelles
17/9/14
Today….
• microscopy, resolution, magnification, EM
(photomicrographs), biological drawings,
chloroplasts & mitochondria
by the end of the day we should be able to…
• Work out magnification and size objects
• Identify structures within cells from
photomicrographs
• Deduce cell types/stages from structures
within them
Size of organelles.
The standard measurements:
• Metre= 1000milimetres
• 1mm= 1000 micrometres (um)
• 1um= 1000 nanometres (nm)
The size of organelles:
Nucleus: 10-20um
Chloroplasts: 2-10um in
Nucleolus: 1-2um
diameter.
Rough ER; membranes 4nm thick
Ribosomes: 20-25nm
Golgi apparatus: variable.
Lysosomes: 100nm
Mitochondria: 1um wide, up to 10um thick.
Centrioles: 0.5umx 0.2um
Why do we have many cells?
• Complexity (differentiation)
• Size
• But the basic unit is the same!
• or is it?…
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Recognising cells and structures in
photomicrographs
• Lymphocytes
Recognising cells and structures in
photomicrographs
• Plant leaf
Recognising cells and structures in
photomicrographs
• Cilia on the surface of cells
Recognising cells and structures in
photomicrographs
• Mitochondria
Specialised cells - Liver Cell
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Plant cell
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Animal cell Draw the animal and
plant cells and surround with
information about each organelle
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Organelles
• Cells contain organelles – have own
membrane.
• Specialised tasks.
• Most organelles are only visible when
the cell is viewed under an electron
microscope.
• COMPARTMENTALISATION
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Nucleus
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•
•
•
The nucleus
Easily seen with light microscope
Largest organelle in the cell with a typically spherical shape.
The ‘brain’ of the cell. Controls activities within the cell by controlling
chemical reactions. (Regulates the synthesis of proteins and enzymes).
Within the nucleus is the:
• Nucleoplasm: jelly like material, containing chromosomes and 1 or more
nucleoli.
• The chromosomes contain DNA (deoxyribonucleic acid) attached to
proteins called histones. During cell division, the chromosomes within
the nucleus become more visible.
• A nucleus not under going division can appear grainy because DNA
extends throughout the nucleus as chromatin.
• Nucleoli: these produce rRNA ( ribonucleic acid) which help to produce
ribosomes. Ribosomes produce proteins.
Nuclear envelope:
• Electron microscope reveals membrane as a double structure.
• This separates the nuclear content from the rest of the cell.
• Nuclear membrane is continuous with the ER. Space between is very
small.
• The inner and outer membranes fuse at intervals giving rise to the
nuclear pores.
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Nucleus
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Nuclear pores
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Nuclear pores
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Endoplasmic reticulum
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Endoplasmic reticulum
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Endoplasmic reticulum
• Made up of a system of parallel cavities or cisternae and
membranes.
• The ER is continuous with the nuclear envelope.
• The fluid filled space between these membranes acts as a
transport network for passing materials throughout the cell.
• Rough Endoplasmic reticulum
• Has ribosomes present on the surface of the membrane which
are involved in the synthesis of proteins which are then
transported in the rough ER.
• The Smooth endoplasmic reticulum
• Has no ribosomes and more tubular cisternae than the rough
ER.Involved in lipid production and is well developed in cells that
produce steroid hormones in the liver.
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Ribosomes
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Golgi
apparatus
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Golgi
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Lysosome
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Microtubules, cytoskeleton
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Cytoskeleton.
Made up of microtubules, microfilaments and
intermediate fibres.
Microtubules.
• Fine, tubular organelles, contribute to complex
network of fibrous proteins making up the
cytoskeleton, in cytoplasm.
• Provide internal skeleton.
• Straight, unbranched hollow structures.
• Walls made of tubulin (protein)
• Increase length by additions of sub units, or shorten
by removal, so can be continuously modified.
• Components of flagella and cilia
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• Microfilaments:
• Solid fibres.
• Made of actin (protein) and smaller amounts of
myosin.
• Both of theses proteins are found in muscle fibres,
and interactions between them are the basis of
muscle contraction.
• Related functions in other cells: e.g. movement of
organelles, such as chloroplasts and mitochondria.
• Intermediate filament:
• Also involved in motility.
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Cillia and flagella
• Cilia
•
Flagella
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Centrioles
• Small hollow cylindrical organelles.
• In most animal cells and also fungi and some algae.
• Walls made up of 9 triplets of microtubules arranged
at an angle.
• Occur in pairs, arranged at right angles to each other,
in AN AREA CALLED the centrosome.
• Situated close to Golgi apparatus and appear to have
a role in the organisation of the spindle fibres in
animal cells. – or do they? RECENT EVIDENCE SAYS
NOT
• Recent work indicates they may be the site of the
formation of the whole cytoskeleton network.
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cilia
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Cilia and flagella microtubule
arrangement 9+2
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Movement of cilia and flagella
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Microvilli
• Minute finger shaped outgrowths/ folds of plasma
membrane e.g animal cells: epithelium lining of small
intestine.
• Plant cells have cell wall, which prevents such
projections.
• Function, to increase surface area of cells, allowing
for increased absorption of materials.
• Contain many microfilaments of proteins actin and
myosin. These probably maintain the shape of
microvilli but also involved in moving them from side
to side.
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L2 part 2 - Chloroplasts and
mitochondria
mitochondria
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PURPOSE - mitochondria
• The cells main source
of power
• Provide eukaryotic
cells with energy
• Main function is to help
with the respiration
process
STRUCTURE
• The mitochondria is normally rod shaped but can
be found as a circle.
• The mitochondria is surrounded by a double
membrane
• There is a space between these two membranes
• The inner membrane has folds which are called
CRISTAE. These are surrounded by the MATRIX –
a jelly-like substance which contains
mitochondrial DNA and RIBOSOMES.
Internal structure
• Mitochondrial inner membrane has little
stalks with spheres on the end =
‘elementary particles’
• The ATP producing enzyme is located in
the stalks.
KREBS/CITRIC ACID CYCLE
• This cycle is used to get as many electrons out of
the food we eat as possible
• The electrons are then used to produce ATP which
is then used for all kinds of cellular functions such
as movement, transport, entry and exit of products
etc.
What happens – in brief
• Glucose split to 2 pyruvate molecules in
cytosol = glycolysis.
• In mitochondria breakdown of glucose is
completed in citric acid cycle and CO2
formed
• At each stage electrons are produced and
stored in mitochondria in a way they can
be used to make ATP
DIAGRAM OF MITOCHONDRIA
• Draw mitochondrion and note how it actually
looks from page 16
Mitochondria
• Mitochondria – present in higher, complex cells and
are the site of aerobic respiration.The matrix
contains enzymes involved in the tricarboxylic acid
(TCA) cycle/ Krebs cycle.
• Adenosine triphosphate (ATP) – reactions in which
the ‘energy currency’ of the cell is produced, takes
place at the cristae.
• Membrane structure –Double membrane. Two
phospholipid membranes, the outer is smooth and the
highly folded inner membranes.( cristae)
• The cristae – formed from the highly folded inner
membrane which gives a large surface area. These
structures contain enzymes for the final stages of
respiration.
• Matrix – contains enzymes which catalyse reactions in
early stages of respiration.Also mitochondrial
ribosomes, which are smaller than those found in the
cytoplasm of the cell, and mitochondrial DNA, as a
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circular strand.
mitochondria
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Chloroplasts
• Chloroplasts occur in the
cells of the photosynthetic
tissue of plants.
• They belong to a group of
organelles known as
plastids, which often
contain pigments.
• Chloroplasts occur in
large numbers in the
palisade cells of the leaves
of flowering plants.
Structure of chloroplasts
•
They are disc-shaped structures and appear green due
to the presence of the pigment chlorophyll.
•
They range from 2 to 5 micrometres in diameter and are
1 micrometre thick, easily seen using a light microscope.
• Electron microscopy shows that each chloroplast is
surrounded by a double membrane, the chloroplast
envelope, enclosing the stroma in which there is a
system of flattened membranous sacs called
thylakoids/lamellae.
• Grana are formed from several thylakoids, or lamellae,
stacked together in the matrix.
Grana: Inside a plant cell’s chloroplasts are tiny grana. Each granum
contains chlorophyll, which absorbs light rays.
Thylakoids/Lamellae: These are sheet like membranes, whose
function is to hold the chlorophyll molecules in a suitable position for
trapping the maximum amount of sunlight.
Stroma: The lamellae are embedded in a watery medium called the
stroma. This contains the enzymes needed for photosynthesis. The
building of carbohydrates also takes place in the stroma.
Chloroplast from leaf palisade cell,
showing internal structure
Electronmicrograph of chloroplast
The site where photosynthesis
takes place. The lightdependant reaction of
photosynthesis happens in the
grana, and the lightindependent reaction of
photosynthesis happens in the
stroma.
STRUCTURE OF THE CHLOROPLAST
The structure of the chloroplast is
bounded by a double membrane within
which are numerous structures called
thylakoids. Each thylakoid consists of a
pair of membranes close to each other
with a narrow space between. In places
the thylakoids are arranged in neat
stacks, rather like a pile of coins.
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•
•
•
question 1
The organelles attached to the surface of rough endoplasmic reticulum are:
centrioles, cisternae, lysosomes, ribosomes
question 2
Small cylindrical structures containing microtubules and found near the
nucleus are called:
centrioles, cisternae, lysosomes, ribosomes
•
question 3
In electron micrographs, a transverse section of a cilium or flagellum shows an
arrangement of: 9 outer and 1 central microtubules, 9 outer and 2 central
microtubules
11 outer and 2 central microtubules, 11 outer and 4 central microtubules
•
question 4
All of the following organelles are only visible using an electron microscope
except:
centrioles, microtubules, mitochondria, ribosomes
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•
•
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question 5
All of the following are membrane-bound organelles except:
chloroplasts, lysosomes, mitochondria, ribosomes
question 6
All of the following are organelles except:
cell wall, chloroplasts, mitochondria, ribosomes
What is the
function of the
golgi?
What are the
internal folds of
mitochondria
called?
Where would
RNA go once it
leaves the
nucleus?
What are
microtubules
made of?
Where is energy
produced in the
cell?
What are the two
types of ER?
What might
happen to old
organelles in the
cell?
Via which
organelle does
modified protein
get transported
out of the cell?
How do you work
out overall
magnification?
H/W
• What are your e.mail addresses?
• Mine is… [email protected]
• Read chapter 1 and answer the book questions
• Draw up a table about similarities and differences of chloroplasts
and mitochondria (e.g. energy production, membrane bound,
contain DNA…)