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CELLULAR BIOLOGY AND MICROSCOPY
AICE Biology
ULTRASTRUCTURE
• The fine or detailed structure of a cell that is revealed by an electron
microscope
• Compartmentalisation and division of labour in a eukaryotic is obvious
with an electron microscope than with a light microscope
THE PLANT CELL
THE ANIMAL CELL
• Nucleus*
• Centrioles*
• Endoplasmic reticulum
• Ribosomes
• Golgi apparatus*
• Lysosomes
• Mitochondria*
• Plasma Membrane*
• Cilia
• Small vacuoles
• Cytoplasm*
Same as animal cell EXCEPT:
No centrioles
Cell wall*
Central vacuole*
• Different from small
vacuoles
• Chloroplasts*
• grana
• Plasmodesmata
• Middle lamella
•
•
•
•
* Means that they ARE
visible with LIGHT
MICROSCOPE
TYPES OF CELLS
Plant Cells
• Mesophyll cells
Animal Cells
• Spongy
• Ciliated epithelial
cells
• palisade
• Bundle sheath cells
• Muscle cells
• Xylem/phloem cells
• Blood cells
• Sieve tube elements
• Nerve cells
• Tracheids
• Root cells
• cortex
BASIC ORGANELLES
•
Cell Surface membrane
• At high magnifications (100 000x +) you can see THREE
layers (trilaminar appearance)
• Hydrohphilic phosphate outer layer (dark line)
• Hydrophobic fatty acid tail inner layer (light line)
• Hydrophilic phosphate inner layer (dark line)
• 7 nm wide (small!!!!) (0.007 um)
• MICROVILLI finger-like extensions of cell surface membrane
• Typical of animal epithelial cells covering surfaces
• Increase surface area of cell membrane
• Good for absorption in gut and reabsorption in kidney
•
Cytoplasm
• Between nucleus and cell surface membrane
• Aqueous, watery material
• Varies from fluid to jelly-like
• Many organelles suspended in here
NUCLEUS
• Largest organelle
• DOUBLE MEMBRANE
• Surrounded by double membrane called the NUCLEAR
ENVELOPE
• Outer membrane of the envelope is continuous with the
ENDOPLASMIC RETICULUM
• Nuclear envelope contains many NUCLEAR PORES
• ALLOWS FOR MATERIALS TO BE EXCHANGED BETWEEN
NUCLEUS AND CYTOPLASM
• Ex. mRNA and ribosomes leave nucleus
• Ex. Hormones and nutrients enter nucleus
INSIDE THE NUCLEUS
•
Chromatin
• Loosely coiled chromosomes spread out in nucleus of
non-dividing cell
• Chromosomes
• Contain DNA organised into functional units
called genes
• Genes control the activities of the cell and
inheritance
• Gene section of DNA that codes for a specific
protein
•
Nucleolus
• Dense structure in nucleus that manufactures
ribosomes
• Usually darkly stained inside of nucleus in
micrographs
CENTRIOLES
•
Two Hollow cylinders about 0.4 um
long
•
Formed from a ring of microtubules
• “cell scaffolding” made of
protein tubulin
• Microtubules are used to grow
the spindle fibers for nuclear
division
•
Just outside the nucleus
•
Lie close together at right angles to
each other
ENDOPLASMIC RETICULUM (ER)
•
Extensive double membrane system running through
the cytoplasm
•
Form a system of flattened sacs (like sheets) called
CISTERNAE
•
Inside sacs form separate compartment from
surrounding cytoplasm
•
Cisternae continues to form the Golgi Apparatus
•
Rough ER
• Consists of ribosomes; modifies polypeptide
chains that are dropped off by the ribosome
• Function: modify polypeptide chains and proteins
(twist and fold into secondary structure)
•
Smooth ER
• Lacks ribosomes
• Function: makes lipids and steroids (cholesterol
and reproductive hormones)
ROUGH ER
• Involved in protein making (synthesis)
• So what are we going to see on it?
• ribosomes
• Once a protein is made, it leaves the ribosome and
goes into the Rough ER
• The rough ER then modifies the protein
• All proteins that are exported by the cell are made on
the RER
• Membrane proteins are made on the RER too
SMOOTH ER
• NO ribosomes on it
• Looks smooth
• Contains collections of ENZYMES that have specialized
tasks
• What do enzymes do?
• Tasks include:
• Synthesis of membrane lipids
• Detoxification of drugs
• Liver cells
• Big in detox therefore….what do u think liver cells have a lot of?
RIBOSOMES
•
Ribosomal RNA wrapped around protein
•
Very small (22 nm in diameter)
•
Consists of 2 parts:
• Large subunit
• Small subunit
•
Found:
• In Cytoplasm
• On Rough ER
• In nucleus
•
Function: hold mRNA in place while tRNA brings over
specific amino acids; makes a polypeptide chain
• Site of protein synthesis
• Prokaryotes 70S ribosomes
• Eukaryotes 80S ribosomes
(mitochondrial/chloroplasts ribosomes are 70S)
GOLGI APPARATUS (GA)
•
Stack of flattened sacs (cisternae)
•
Constantly being formed at one end from vesicles which
bud off from the ER and broken down on the other end to
form golgi vesicles that carry the products made in the GA
•
FUNCTION: collects, processes and sorts molecules
(particularly proteins from the rough ER) ready for transport
in Golgi vesicles either to other parts of the cell or out of
the cell (secretion)
• They are the CUSTOMIZATION
SHOP
• ALSO functions in the
creation/production of LYSOSOMES
MORE INFO ON THE GOLGI COMPLEX/BODY….
Examples of Protein Processing
Other Important Functions
• Addition of sugars to
proteins to make
Glycoproteins
• Golgi vesicles become
lysosomes
• Function in cell
membrane
• Removal of methoionine
(1st amino acid) to create
a functioning protein
• Conversion of sugars
into components of the
cell wall
• Form secretory vesicles
that can release
contents via exocytosis
ENDOMEMBRANE SYSTEM & PROTEIN
SYNTHESIS
•
DNA in nucleus gives message to mRNA
•
mRNA leave thru nuclear pore into cytoplasm
•
Ribsome “catches” mRNA
•
tRNA come over and start adding amino acids together making polypeptide chain
•
Polypeptide chain either functions immediately or goes onto next step
•
Ribosome deposits polypeptide chain into lumen of the RER
•
Polypeptide chain is modified (2* and 3* structure)
•
Functioning protein either stays and works in RER or…
•
Vesicle buds off RER and transports it to Golgi Apparatus
•
Protein is further modified in GA and leaves in a vesicle (either secretory or peroxisome or membrane)
LYSOSOMES (LIE-SO-SOH-MZ)
•
Spherical sacs surrounded by a single membrane and having no internal structure
•
Diameter of 0.1 - 0.5 micrometers
•
Contain hydrolytic (digestive) enzymes
• These can be harmful to other parts of the cell and must be kept in these lysosome compartments
• Interior has a low pH (acidic) pH 4.5-5 (cytoplasm is usually 7.2)
• Enzymes are active at a low pH (optimum conditions)
• proteases
• lipases
• nucleases
• polysaccharidases
• FUNCTON: responsible for the breakdown/digestion of unwanted structures (organelles or entire
cells); Digestion of lipids, carbohydrates, and proteins into smaller molecules that can be used by
the cell; also digests organs that have outlived their usefulness
• Used by white blood cells (leukocytes) to digest bacteria (endocytosis)
• Enzymes sometimes released outside the cell (replacement of cartilage in bone development)
• Specialized lysosome, “Acrosome”, in head of sperm; specialized for digesting a path to the ovum
• Digest mammary glands after lactation
•
Slightly larger than lysosome
•
About 1 um in diameter
•
Contain its own DNA
•
Surrounded by an envelope DOUBLE MEMBRANE
(two membranes)
MITOCHONDRIA
• Inner membrane
• Outer membrane
•
In Animal AND Plant cells
•
Nearly all come from the ovum
• You get your mitochondria from your mom!
•
Inner membrane folds inwards to make finger-like
projections called cristae that project
•
Interior space called the MATRIX
•
FUNCTION:
• Carry out later stages of aerobic cellular
respiration (Kreb’s Cycle and Electron Transport
Chain…ETC)
• MAKES ATP
MITOCHONDRIA
Outer Membrane
• Protein Porin
• Forms wide aqueous
channel in outer membrane
• Easy access for small,
water soluble molecules to
enter from surrounding
cytoplasm into the
intermembrane space
Inner membrane
• Much more selective
barrier
• Controls precisely what
ions and molecules
enter the MATRIX
MITOCHONDRIA=LOTS OF ATP
•
Site of cell respiration
•
ENZYMES important
• Cell Respiration (REQUIRES
OXYGEN=AEROBIC)
• 3 stages of Cell respiration
• GLYCOLYSIS
• Makes a lil’ bit of ATP
• Location: CYTOPLASM
• KREBS CYCLE
• Makes a lil’ bit of ATP
• Location: MATRIX of MITOCHONDRIA
• ELECTRON TRANSPORT CHAIN
• Makes A LOT of ATP!!!
• Location: INNER MEMBRANE of
MITOCHONDRIA
NO OXYGEN= ANAEROBIC
• No oxygen available (or not enough) cell switches to FERMENTATION
• Glycolysis over and over and over
• Happens in CYTOPLASM
• Makes a Little Bit of ATP
• Lactic Acid Fermentation
• Animals
• Muscle cells
• Only can use for a few seconds
• Alcohol Fermentation
• Bacteria and Fungi
• Ex. yeast
GREAT WEBSITE
• Endomembrane system
ATP HYDROLYSIS
• ATP is a small, water
soluble molecule
• Once made in the
mitochondria, it can leave
and spread to wherever it is
needed in the cell
• Energy is released by
breaking down ATP ADP
+P
ULTRASTRUCTURE OF PLANT CELL
• No centrioles
• Very rarely plant cells will have cilia
• Only plant cells
• Thick cell wall made of cellulose
• Large central vacuole
• chloroplasts
CHLOROPLASTS
• Plant and some Bacteria cells only ( NOT
in animal cells)
• Capture energy from the sunlight and
convert it into chemical energy…what is
this process called?
• PHOTOSYNTHESIS
• Like solar power for plants
• 2 membranes (Double membrane)
• Inside: large stacks of other
membranes that contain chlorophyll
CHLOROPLAST (FOUND IN CELLS IN LEAVES)
• Concentrated in the cells of the
mesophyll (inner layer of tissue)
in leaf
• Stomata
• Tiny pores on surface of leaf
• Allows carbon dioxide and
oxygen in and out of the leaf
• Veins
• Carry water and nutrients
from roots to leaves
• Deliver organic molecules
produced in leaves to other
parts of the plant
CHLOROPLAST
• Cellular organelle where
photosynthesis takes place
• Double membrane
• Outer membrane
• Stroma (fluid filled space)
• Inner membrane
• Thylakoids
• Thylakoid membrane contains
CHLOROPHYLL
• Granum
• Intermembrane space
• Contain chemical compound
called Chlorophyll
• This molecule gives chloroplast its
green color
STRUCTURE OF CHLOROPLAST
• Structures organize the many reactions that
take place in photosynthesis
• Stroma
• Thick fluid enclosed by the inner membrane
• Thylakoids
• Disc-like sacs suspended in the stroma
• Has membrane that surrounds inner
thylakoid space
• Grana (sing. Granum)
• Stacks of thylakoids
VACUOLES
• The factory’s storage place
• Only in certain cells
• Sac-like organelles
• Function: stores material such as water, salts, proteins, and
carbohydrates
• Tonoplast
• Membrane surrounding vacuole
• Cell sap
• Glcuse storage
• Plant cells have a single, large central
vacuole
• Pressure of central vacuole allows plants to support heavy
structures
Single Membrane
Double Membrane
• Ribosome (some)
• Nucleus
• Lysosome
• Mitochondria
• Endoplasmic reticulum
• Smooth
• Rough
• Golgi apparatus
• Vacuole
• Chloroplast
Part 3
MICROTUBULES
• Long, rigid, hollow tubes
• Small (25 nm in diameter)
• Part of cytoskeleton (with actin and
intermediate filaments)
• Protein TUBULIN
• Alpha tubulin
• Beta tublulin
• Alpha + Beta = DIMERS (double
molecules)
• PROTOFILAMENTS dimers joined
end to end (type of polymerization)
• 13 protofilaments line up next to
each other in a ring with hollow
center forming microtubule
FUNCTION OF MICROTUBULES
• Support
• Cytoskeleton
• Move secretory vesicles inside and outside the cell
• Nuclear division
MTOC
• MTOCs
• Assemble tubulin to form
microtubules in special cell locations
• Microtubule organizing center
• Microtubules formed and broken
down here
• Ex. Centrioles (found at base of cilia
and flagella)
BASAL BODY
CILIA AND FLAGELLA
• Plural: cilium and flagellum
• Cilia: hundreds of extension of the cell membrane that move like the oars
of a boat
• Flagella: one or two long extensions off the cell that move in a whip like
fashion
• Enable cells to swim rapidly through liquid
CILIA & FLAGELLA
• Long, thin extensions that move in wavelike manner
• Flagella
• Very few extensions
• Long and whip like
• Cilia
• Short extensions (3-4 um long)
• Many present
• Hair like
• Covered with an extension of the plasma membrane
• Contains microtubules (with tubulin protein) that extend throughout its length
• Microtubules arise from structure called the BASAL BODY in cytoplasm
• Identical in structure to centrioles
MOVEMENT OF CILIA AND FLAGELLA
• Caused by microtubules
• Coordinated movement
• Each adjacent cilia is
slightly off from its
neighbor
• Ripple effect (long grass in
the wind)
• Purpose:
• Move substances around
the cell (if cell is attached)
• Move the cell itself if it is
unattached
ENDOSYMBIONT
THEORY
• 1960s
• Mitochondria and chloroplast contain:
• Ribosomes (70S)
• S is unit of measurement of
ribosome size
• Measures how fast they sediment
in a centrifuge
• Small, circular DNA
• Reproduce
• Make energy
• Mit. & Chl. Were once bacteria that came
to live symbiotically in larger cells
Biological Drawings
The following guidelines should be used when doing a formal biological drawing of an
object you view under the microscope:
1. Drawings, including labels, name and other info, must be done in pencil. (preferably
soft lead that will not smudge).
2. The title of the drawing is simply the name of the object you are looking at.
3. If the drawing is a formal drawing to be handed in, use unlined white 81/2” x 11”
paper or lab drawing paper.
4. The drawing should be as large as possible. (at least 1/3 of the page) and should
be kept to the left of the center of the page.
5. All labels must be printed and are to be lined up on the right hand side of the
drawing. Use a ruler for label lines.
6. The drawing should be an outline of what you see. Do not include additional
structures just because you think you should see them.
7. Do not shade or sketch. All lines should be solid and complete.
8. Magnification of your drawing MUST be included
PRACTICE
•
Anne viewed an amoeba under the high
power 40x objective lens on her microscope
and drew the following picture of the amoeba
•
She needs to calculate the magnification of
her drawing.
•
Here is other relevant info:
•
Answer the following:
a) Convert the diameter of field of view on low power to um.
b) Calculate the total magnification under low power and high power.
c) Calculate the diameter of the field of view under high power.
d) Calculate the size of the object under high power.
e) Measure the size of the drawing. Convert to um.
f) Calculate the magnification of Anne’s drawing.
Organell
e
Plant or
Animal (or
both)
Eukaryotic or
Prokaryotic or
Both
Size
in
um
Size
in
nm
Single,
double, or
no
membrane
Function
LM?
EM?
MICROSCOPE LAB WORK
•
Part 1
• Calibrate your eye piece graticule at low, medium and high power
• Determine the field of view at low, medium and high power
• Complete the chart below
•
Part 2
• Complete a plan diagram of the plant cell on slide 2
• Make sure to follow the guidelines for biological drawings
• Include the total
Large unit
of EG
Low Power
Medium
Power
High Power
Medium
unit of EG
Small Unit
of EG
FOV