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The Cell Organelles:
Acceleration in 7th Grade Life Science
Cell:
•A basic unit of living matter separated
from its environment by a plasma
membrane.
•The smallest structural unit of life.
The Cell Theory
1. All living things ( organisms ) are made of
one or more cells.
2.The cell is the basic unit of life ( it is the
basic structure and carries out the basic
functions of all organisms).
3. All new cells come from preexisting cells.
Microscope Features
Magnification:
• Increase in apparent size of an object.
• Ratio of image size to specimen size.
Microscope Features
Resolving power:
• Measures clarity of image.
• Ability to see fine detail.
• Ability to distinguish two objects as
separate.
• Minimum distance between 2 points
at which they can be distinguished as
separate and distinct.
Microscopes
Light Microscopes:
• Earliest microscopes used.
• Lenses pass visible light through a
specimen.
• Magnification: Highest possible from
1000 X to 2000 X.
• Resolving power: Up to 0.2 mm (1 mm =
1/1000 mm).
Types of Microscope
Electron Microscopes:
• Developed in 1950s.
• Electron beam passes through specimen.
• Magnification: Up to 200,000 X.
• Resolving power: Up to 0.2 nm (1nm =
1/1,000,000 mm).
Types of Microscope
Electron Microscopes:
Two types of electron microscopes:
1. Scanning Electron Microscope: Used
to study cell or virus surfaces.
2. Transmission Electron Microscope:
Used to study internal cell structures.
Components of All Cells:
1. Plasma membrane: Separates cell
contents from outside environment.
Made up of phospholipid bilayers and
proteins.
2. Cytoplasm: Liquid, jelly-like material
inside cell.
3. Ribosomes: Necessary for protein
synthesis.
Prokaryotic versus Eukaryotic Cells :
Feature
Prokaryotic
Eukaryotic
Organisms
Bacteria
Nucleus
Absent
All others (animals, plants,
fungi, and protozoa)
Present
DNA
One chromosome
Multiple chromosomes
Size
Small (1-10 um)
Large (10 or more um)
Membrane
Bound
Organelles
Absent
Present (mitochondria,
golgi, chloroplasts, etc.)
Division
Rapid process
(Binary fission)
Complex process
(Mitosis and Cytokinesis – Cell Cycle)
Relative Sizes of Prokaryotic and
Eukaryotic Cells and Viruses
Relative Sizes of Cells and Other Objects
Relative Sizes of Structures
1 nanometer (10-9 m)
10 nanometers (10-8 m)
100 nanometers (10-7 m)
1 micron (10-6 m)
10 microns (10-5 m)
100 microns (10-4 m)
1 millimeter (10-3 m)
water molecule
small protein
HIV virus
cell vacuole
bacterium
large plant cell
single cell embryo
http://learn.genetics.utah.edu/content/begin/cells/scale/
Prokaryotic Cells
• Bacteria and blue-green algae.
• Small size: Range from 1- 10 micrometers in
length. About one tenth of eukaryotic cell.
• No nucleus: DNA in cytoplasm or nucleoid region.
• Ribosomes are used to make proteins.
• Cell wall: Hard shell around membrane.
• Other structures that may be present:
• Capsule: Protective, outer sticky layer. May be
used for attachment or to evade immune system.
• Pili: Hair-like projections (attachment).
• Flagellum: Longer whip-like projection
(movement).
Prokaryotic Cells: Lack a Nucleus and
other Membrane Bound Organelles
Eukaryotic Cells
• Include protist, fungi, plant, and
animal cells.
• Nucleus: Protects and houses DNA.
• Membrane-bound Organelles:
Internal structures with specific
functions.
• Separate and store compounds.
• Store energy.
• Work surfaces.
• Maintain concentration gradients.
Membrane-Bound Organelles of
Eukaryotic Cells
• Nucleus
• Rough Endoplasmic Reticulum (RER)
• Smooth Endoplasmic Reticulum (SER)
• Golgi Apparatus
• Lysosomes
• Vacuoles
• Chloroplasts
• Mitochondria
Eukaryotic Cells: Typical Animal Cell
Eukaryotic Cells: Typical Plant Cell
Nucleus
• Structure:
• Double nuclear membrane (envelope).
• Large nuclear pores.
• DNA (genetic material) is combined with
histones and exists in two forms:
• Chromatin (Loose, threadlike DNA,
most of cell life).
• Chromosomes (Tightly packaged
DNA. Found only during cell
division).
• Nucleolus: Dense region where ribosomes
are made.
Nucleus
Functions:
• House and protect cell’s genetic
information (DNA)
• Ribosome synthesis
Structure of Cell Nucleus
Endoplasmic Reticulum (ER)
• “Network within the cell.”
• Extensive maze of membranes that
branches throughout cytoplasm.
• ER is continuous with plasma membrane
and outer nucleus membrane.
• Two types of ER:
• Rough Endoplasmic Reticulum (RER)
• Smooth Endoplasmic Reticulum (SER)
Rough Endoplasmic Reticulum (RER)
• Flat, interconnected, rough membrane sacs.
• “Rough”: Outer walls are covered with
ribosomes.
• Ribosomes: Protein making “machines.”
• May exist free in cytoplasm or attached to ER.
• RER Functions:
• Synthesis of cell and organelle membranes.
• Synthesis and modification of proteins.
• Packaging, and transport of proteins that
are secreted from the cell.
• Example: Antibodies
Rough Endoplasmic Reticulum (RER)
Smooth Endoplasmic Reticulum (SER)
• Network of interconnected tubular smooth
membranes.
• “Smooth”: No ribosomes.
SER Functions:
• Synthesis of phospholipids, fatty acids, and steroids
(sex hormones).
• Breakdown of toxic compounds (drugs, alcohol,
amphetamines, sedatives, antibiotics, etc.).
• Helps develop tolerance to drugs and alcohol.
• Regulates levels of sugar released from liver into
the blood.
• Calcium storage for cell and muscle contraction.
Smooth Endoplasmic Reticulum (SER)
Golgi Apparatus
• Stacks of flattened membrane sacs that may be
distended in certain regions. Sacs are not
interconnected.
• First described in 1898 by Camillo Golgi (Italy).
• Works closely with the ER to secrete proteins.
Golgi Functions:
• Receiving side receives proteins in transport vesicles
from ER.
• Modifies proteins into final shape, sorts, and labels
proteins for proper transport.
• Shipping side packages and sends proteins to cell
membrane for export or to other parts of the cell.
• Packages digestive enzymes in lysosomes.
The Golgi Apparatus: Receiving,
Processing, and Shipping of Proteins
Lysosomes
• Small vesicles released from Golgi containing at least
40 different digestive enzymes, which can break down
carbohydrates, proteins, lipids, and nucleic acids.
• Optimal pH for enzymes is about 5.
• Found mainly in animal cells.
Lysosome Functions:
• Molecular garbage dump and recycler of
macromolecules (e.g.: proteins).
• Destruction of foreign material, bacteria, viruses,
and old or damaged cell components.
• Digestion of food particles taken in by cell.
• After cell dies, lysosomal membrane breaks down,
causing rapid self-destruction.
Lysosomes: Intracellular Digestion
Lysosomes, Aging, and Disease
• As we get older, our lysosomes become leaky, releasing
enzymes which cause tissue damage and inflammation.
• Example: Cartilage damage in arthritis.
• Steroids or cortisone-like anti-inflammatory agents
stabilize lysosomal membranes, but have other
undesirable effects (affect immune function).
• Diseases from “mutant” lysosome enzymes are usually
fatal:
• Pompe’s disease: Defective glycogen breakdown in
liver.
• Tay-Sachs disease: Defective lipid breakdown in
brain. Common genetic disorder among Jewish
people.
Vacuoles
• Membrane bound sac.
• Different sizes, shapes, and functions:
• Central vacuole: In plant cells. Store starch,
water, pigments, poisons, and wastes. May
occupy up to 90% of cell volume.
• Contractile vacuole: Regulate water balance,
by removing excess water from cell. Found in
many aquatic protists.
• Food or Digestion Vacuole: Engulf nutrients in
many protozoa (protists). Fuse with lysosomes
to digest food particles.
Central Vacuole in a Plant Cell
Interactions Between Membrane Bound
Organelles of Eukaryotic Cells
Chloroplasts
•
•
•
•
Site of photosynthesis in plants and algae.
CO2 + H2O + Sun Light -----> Sugar + O2
Number may range from 1 to over 100 per cell.
Disc shaped structure with three different membrane
systems:
1. Outer membrane: Covers chloroplast surface.
2. Inner membrane: Contains enzymes needed to
make glucose during photosynthesis. Encloses
stroma (liquid) and thylakoid membranes.
3. Thylakoid membranes: Contain chlorophyll,
green pigment that traps solar energy.
Organized in stacks called grana.
Chloroplasts Trap Solar Energy and Convert
it to Chemical Energy
Chloroplasts
• Contain their own DNA, ribosomes, and
make some proteins.
• Can divide to form daughter chloroplasts.
• Plastid: Organelle that produces and stores
food in plant and algae cells.
Other plastids include:
• Leukoplasts: Store starch.
• Chromoplasts: Store other pigments
that give plants and flowers color.
Mitochondria (Sing. Mitochondrion)
• Site of cellular respiration:
• Food (sugar) + O2 -----> CO2 + H2O + ATP
• Change chemical energy of molecules into the
useable energy of the ATP molecule.
• Oval or sausage shaped.
• Contain their own DNA, ribosomes, and make
some proteins.
• Can divide to form daughter mitochondria.
• Structure:
• Inner and outer membranes.
• Intermembrane space
• Cristae (inner membrane extensions)
• Matrix (inner liquid)
Mitochondria Harvest Chemical Energy
From Food
Origin of Eukaryotic Cells
• Endosymbiont Theory: Belief that chloroplasts
and mitochondria were at one point independent
cells that entered and remained inside a larger
cell.
• Both organelles contain their own DNA
• Have their own ribosomes and make their
own proteins.
• Replicate independently from cell, by
binary fission.
• Symbiotic relationship: the larger cell obtains
energy or nutrients and the smaller cell is
protected by larger cell.
Endosymbiont Theory
Cytoplasm
DNA
Plasma
membrane
Ancestral
prokaryote
Infolding of
plasma membrane
Endoplasmic
reticulum
Nucleus
Nuclear envelope
Engulfing
of aerobic
heterotrophic
prokaryote
Cell with nucleus
and endomembrane
system
Mitochondrion
Mitochondrion
Ancestral
heterotrophic
eukaryote
Figure 26.13
Engulfing of
photosynthetic
prokaryote in
some cells
Plastid
Ancestral
Photosynthetic
eukaryote
The Cytoskeleton
• Complex network of thread-like and tube-like
structures.
• Functions: Movement, structure, and
structural support.
• Three Cytoskeleton Components:
1. Microfilaments: Smallest cytoskeleton
fibers. Important for:
Muscle contraction: Actin & myosin fibers
in muscle cells
“Amoeboid motion” of white blood cells
Three Cytoskeleton Components:
1. Microfilaments: Smallest cytoskeleton fibers.
Important for:
Muscle contraction: Actin & myosin fibers in muscle cells.
“Amoeboid motion” of white blood cells.
2. Intermediate filaments: Medium sized fibers.
• Anchor organelles (nucleus) and hold cytoskeleton in
place.
• Abundant in cells with high mechanical stress.
3. Microtubules: Largest cytoskeleton fibers.
• Found in Centrioles: A pair of structures that help move
chromosomes during cell division (mitosis and meiosis).
• Found in animal cells, but not plant cells.
• Movement of flagella and cilia.
Components of the Cytoskeleton are
Important for Structure and Movement
Cilia and Flagella:
• Projections used for locomotion or to move
substances along cell surface.
• Enclosed by plasma membrane and contain
cytoplasm.
• Consist of 9 pairs of microtubules surrounding two
single microtubules (9 + 2 arrangement).
• Flagella: Large whip-like projections.
• Move in wavelike manner, used for locomotion.
• Example: Sperm cell
• Cilia: Short hair-like projections.
• Example: Human respiratory system uses cilia
to remove harmful objects from bronchial
tubes and trachea.
Structure of a Eukaryotic Flagellum
Cell Surfaces:
Cell wall: Much thicker than cell
membrane, (10 to 100 X thicker).
• Provides support and protects cell from
lysis.
• Plant and algae cell wall: Cellulose
• Fungi and bacteria have other
polysaccharides.
• Not present in animal cells or protozoa.
Sharing of nutrients, water, and chemical
messages.
Cell Surfaces:
Plasmodesmata:
• Channels between adjacent plant cells
form a circulatory and communication
system between cells.
• Sharing of nutrients, water, and
chemical messages.
Plasmodesmata: Communication Between
Adjacent Plant Cells
Cell Surfaces:
Extracellular matrix: Sticky layer of
glycoproteins found in animal cells.
• Important for attachment, support,
protection, and response to
environmental stimuli.
Cell Surfaces:
Junctions Between Animal Cells:
Tight Junctions: Bind cells tightly, forming a
leakproof sheet. Example: Between
epithelial cells in stomach lining.
Anchoring Junctions: Rivet cells together, but
still allow material to pass through spaces
between cells.
Communicating (Gap) Junctions: Similar to
plasmodesmata in plants. Allow water and
other small molecules to flow between
neighboring cells.
Different Animal Cell Junctions
Important Differences Between Plant
and Animal Cells:
Plant cells
Cell wall
Chloroplasts
Large central vacuole
Flagella rare
No Lysosomes
No Centrioles
Animal cells
None (Extracellular matrix)
No chloroplasts
No central vacuole
Flagella more usual
Lysosomes present
Centrioles present
Important Differences Between Plant
and Animal Cells:
Animal Cell
Plant Cell
Summary of Eukaryotic Organelles:
Function: Manufacture
• Nucleus
• Ribosomes
• Rough ER
• Smooth ER
• Golgi Apparatus
Summary of Eukaryotic Organelles:
Function: Breakdown
• Lysosomes
• Vacuoles
Summary of Eukaryotic Organelles:
Function: Energy Processing
• Chloroplasts (Plants and algae)
• Mitochondria
Summary of Eukaryotic Organelles:
Function: Support, Movement,
Communication.
• Cytoskeleton (Cilia, flagella, and
centrioles)
• Cell walls (Plants, fungi, bacteria, and
some protists)
• Extracellular matrix (Animals)
• Cell junctions