Transcript Organelles 2010_1

Cell Organelles
of a Eukaryotic Cell
Prokaryotic Cells vs. Eukaryotic Cells
• Prokaryotic Cells
– Much smaller and simpler than eukaryotic cells
– Size less than 10 micrometers
– Thought to be first living life forms on Earth
– Bacteria cells
– Structures
• Cell wall
• The plasma membrane
• Flagella
• Ribosomes
• Nucleoid region (but NO NUCLEUS!)
• No Mitochondria
• I. Plasma Membrane II. Mesosome
III. Cell Wall
E. coli Bacteria
Definition of an Organelle
contained in Eukaryotic Cells
• Non-cellular structures that carry out specific functions (a bit like organs in
a multi-cellular organism)
– These structures bring about compartmentalization in eukaryotic cells
which allows for chemical reactions to be separated and for specific
reactions to be isolated which increases efficiency in a cell
• Different types of cells have different organelles
• Definitions found on IB External exam questions for the term “organelle”:
– Sub-cellular structures
– Discrete structures found inside all cells that have specific function.
Cytoplasm
• Cytoplasm is not specifically listed as an “organelle” that you need to
know, however, in other literature I have seen it included
• Book Definition: Contains dissolved substances, enzymes, and the cell
organelles
• Test Questions I found about it pertained to:
– The process of Translation occurs here
– Glycolysis, which is the beginning stage of cellular respiration occurs
here
• Glucose here is broken into pyruvate to release energy for use in a
cell
Free Ribosomes
• Definition (From Exam)- Small spherical structures,
consisting of two subunits.
• Structure/Function: Ribosomes are the workbenches where
proteins get manufactured. A ribosome is a large molecular
complex (organelle), composed of several proteins and
ribonucleic acid that reads messenger RNA and thereby
synthesizes proteins.
• Contents: Large and Small subunits in Eukaryotic cells.
• Characteristics- All cells, including Archaea and bacteria
have ribosomes.
Free vs. Attached: Ribosomes
• They
occur both as free particles within cells and,
in eukaryotes, as particles attached to the
membranes of the endoplasmic reticulum.
Prokaryotic
vs.
Smaller size (70S)
Eukaryotic cells
Larger size (80S)
Endoplasmic Reticulum
(ER)
• Functions
- Smooth ER –Lipid synthesis and transportation
- Rough ER –Protein transportation and processing
• Structure
Lysosome
• Function: Lysosomes are the cell's garbage disposal system.
Lysosomes digest excess or worn-out organelles, food
particles, and engulfed viruses or bacteria.
• Contents: Contain enzymes created by the cell that are used
to digest.
• Structure: Like rounded material with sacs inside
Golgi Apparatus
• Found in: Most eukaryotic cells
• Function: The primary function of the Golgi apparatus is to process and
package macromolecules, such as proteins and lipids. The Golgi apparatus
modifies, sorts, and packages these macromolecules for cell secretion.
• Structure: The Golgi is composed of stacks of membrane-bound structure.
Mitochondrion
•
•
•
Definition: Organelles surrounded by
two membranes, the inner of which
is folded inwards.
Function Example:
-Cell respiration
Structure Features Related to
Function:
- The mitochondrion is bounded by
a double membrane; inner
membrane has infoldings (cristae).
The cristae greatly increases the
surface area which allows the
membranes to carry out their
primary functions. Mitochondria is
protected by two membranes and
the inner membrane surrounds the
cristae.
•
Has similarities to prokaryotic cells.
Mitochondrion(cont.)
• Structures on electron micrograph
IB Micrograph of Mitochondria
A.
B.
1. Annotate similarities in
structure
2. State Visible
Differences other than
size
3. Predict which could
produce ATP at a
greater rate
The electron micrographs below show mitochondria in longitudinal
section. The mitochondrion in A is from a bat pancreas cell and that in
B is from a mouse liver cell.
Answers to Questions on last slide
(a)both have two (outer) membranes; both have cristae;
both have a matrix (with a grainy appearance) /
ribosomes;
2 max
(b)shape; arrangement of cristae; density of cristae;
amount of matrix granules / any reference to dark dots;
(do not accept ribosomes)2 max
(c)A / bat’s;larger size / volume; greater surface area of
cristae / more cristae;closeness of mitochondria in B
mouse reduces rate;3 max
Mitochondrion(cont.)
• What is contained in the inner membrane of the mitochondrion?
– Electron transport chain
– Crista
• Internal pockets formed to help proteins operate efficiently
– Many proteins
• These include transport proteins that transport metabolites across the
inner membrane
Nucleus
IB DEFINITION:
Region of the cell containing chromosomes,
surrounded by a double membrane, in which
there are pores. Provides for storage and
protection of chromosomes
Note: nucleus is only present in membranebound cells
• Structure
Nucleus
Endoplasmic Reticulum allows nutrients to flow in and out of nucleus
along with RNA strands to control activities.
Nucleus
Cell Wall
• Function: A cell wall is a tough, usually flexible but sometimes fairly rigid
layer that surrounds some types of cells.
• Structure: It is located outside the cell membrane and provides these cells
with structural support and protection, and also acts as a filtering
mechanism. A major function of the cell wall is to act as a pressure vessel,
preventing over-expansion when water enters the cell.
• They are found in plants, bacteria, fungi, and algae.
Animals and protozoa do not have cell walls.
Cell
Chloroplast
Chlorophyll in the Chloroplast
•
•
The function of the majority of the chlorophyll is to absorb and transfer
light energy by resonance energy transfer to the reaction center of the
photosystems to a specific chlorophyll pair.
The reaction chlorophyll pair then takes the light energy transferred
to them from the other chlorophyll pigments and undergoes a charge
separation where the chlorophyll gives up an electron into a electron
transport chain.
The electron flow produced by the reaction center chlorophyll pairs is
used mainly to produce ATP chemical energy .
The structure of chlorophyll:
Wavelengths of
How much
– There are two parts to the chlorophyll,
light
absorbed (nm)
the head and the tail. The head consists
of a porphyrin ring or nucleus, from
Red
650
which extends a tail made up of a 20Some orange
590
carbon grouping called the phytol
Some yellow
570
Why do plants appear green?
- Because the chlorophyll absorbs all the
Blue
475
wavelengths of the sunlight except green, so
Indigo
445
that is the color that reflects on our eyes.
Violet
400
General IB Questions on Organelles
Capillary
I
(a)Identify the structures labeled I,
II and III in the micrograph above
and give a role for each one.
Structure
Storage vesicles
II
Role
A.
B.
C.
D.
(b)(i)Using the letter A, identify one
location on the micrograph where
transcription takes place.
III
(ii)Using the letter B, identify one location
on the micrograph where chemiosmosis
occurs.
See next slide for answers!
Answers to questions on last slide
Structure
(i)
(ii)
I:
mitochondria
II:
nucleus
III:
(rough) endoplasmic
reticulum
Role
produce ATP / site of (aerobic)
respiration;
contains genetic information /
produces RNA /
site of replication;
(site of) translation / protein
production / protein
transport;
A in nucleus / A in mitochondria
B in a mitochondrion
1
1
General IB Questions on Organelles
The electron micrograph below shows part of a cell .
1. Identify the structures labeled I and II.
2. Deduce, with a reason, whether this cell
is eukaryotic or prokaryotic.
Answers:
I: membrane / (nuclear) envelope;
II: mitochondrion / mitochondria;
Answers:
eukaryotic, internal membranes
/ membrane bound organelles /
presence of mitochondria /
double nuclear membrane;