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Cell Structure
Dr. Stafford
2015
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KEY CONCEPT Cells are the Basic unit of life.
Scientists
Robert Hooke – 1665
–Looked at cork
–Looked like monastery rooms (cells)
–Named the structures in the cork – “CELLS”
Scientists
Anton van Leeuwenhoek – 1674
–Father of microbiology
–Observed “living cells – “animalcules”
Scientists
Simple light microscope vs. compound light microscope
–Simple – one lens
–Compound – 2 or more lens
Scientists
Matthius Schleiden – 1838 – German
–Plants are made of cells
Theodor Schwann – 1839 – German
–All animals are made of cells
–“all living things are made of cells”
Scientists
Rudolp Virchow – 1855 – German
–“all cells come from preexisting cells”
Scientists
Cell Basics
• Cell Theory
– All living organisms are made of cells
– The cell is the basic unit of all living organisms
– All cells come from preexisting cells
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• Early studies led to the development of the cell theory.
– The Cell theory has three principles.
• All organisms are made of cells.
• Early studies led to the development of the cell theory.
– The Cell theory has three principles.
• All organisms are made of cells.
• All existing cells are produced by other living
cells.
• Early studies led to the development of the cell theory.
– The Cell theory has three principles.
• All organisms are made of cells.
• All existing cells are produced by other living cells.
• The cell is the most basic unit of life.
Cell Basics
• Things found in all cells
– DNA – genetic code – different for cells from different organisms
– Plasma membrane – boundary of all cells – maintains homeostasis inside the
cell
– Cytoplasm – jelly-like fluid that fills the cell
– Ribosomes – nonmembrane-bound organelle that assembles proteins
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Cell Basics
• Types of cells – all living organisms fall into two categories
– Prokaryotes – bacteria
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No nucleus
No membrane bound organelles
Smaller
First living organisms
Most have a cell wall
Bacterium
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(colored SEM; magnification 8800x)
Cell Basics
• Types of cells (cont.)
– Eukaryotes – all except bacteria
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Has a membrane-bound nucleus
Has membrane bound organelles
Larger than prokaryotes
More complicated – came later in history
Some have cell wall….some don’t
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s
nucleus
•s
organelles
cell membrane
cytoplasm
Eukaryotic Cell Structures
• Cell Boundaries
–Plasma membrane – selectively permeable
membrane
• Maintains homeostasis – controls what goes
into or leaves a cell
• Phospholipid bilayer with proteins,
cholesterol, and carbohydrate chains added in
or on it
• Found around the outside of all cells
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Eukaryotic Cell Structures
• Cell Boundaries (cont.)
–Cell wall – fairly rigid structure found outside
the plasma membrane
• Provides additional support and protection
• Found in plants, fungi, and some protist cells
• Not selectively permeable – allows most
everything to flow through it
• Made of cellulose in plants
• Gives the cell its more rigid shape
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• Plant cells have cell walls and chloroplasts.
– A cell wall provides rigid support.
Eukaryotic Cell Structures
• Nucleus – control center of the cell – contains two
main structures
–1. DNA - holds the code for making proteins
which is what controls all the activities of the
cell – comes in two forms
• Chromatin – loosely arranged DNA – the form
usually found in an active cell doing its daily
work
• Chromosomes – densely packed DNA – found
during cell division (mitosis)
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Eukaryotic Cell Structures
•Nucleus – contains two main structures
(cont.)
– 2. Nucleolus – seen as a smaller dark
structure inside the nucleus
•Makes ribosomes
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Eukaryotic Cell Structures
• Nucleus – control center of the cell (cont.)
–Nuclear envelope – a double membrane that
surrounds the nucleus
• 2 phospholipid bilayers
• Nuclear pores – holes in nuclear envelope for
substances like mRNA and ribosomes to pass
out of the nucleus into the cytoplasm where
proteins are made
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• Several organelles are involved in making and
processing proteins.
• The nucleus stores genetic information.
Eukaryotic Cell Structures
• Cytoplasm – jelly-like fluid that fills the cell from
the outside of the nucleus to the plasma
membrane
–Suspends the organelles
–Contains many substances the organelles need
to work with
• Building blocks for structures and
macromolecules
• Ions
• Water
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Eukaryotic Cell Structures
•Assembly. transport, and storage – the
organelles that make and complete proteins
and transports them around the cell and out
of the cell (secretion)
• Home of CELLS alive!
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Eukaryotic Cell Structures
• Assembly, transport, and storage (cont.)
–Ribosomes – found in all cells – organelle that makes
proteins
• Made by nucleolus – combination of proteins
and rRNA
• Found in cytoplasm
• 2 part organelle
• Can be attached to endoplasmic reticulum
• Can be unattached to endoplasmic reticulum
– free-floating
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• Several organelles are involved in making and processing proteins.
(continued)
• Ribosomes link amino acids to form proteins.
Eukaryotic Cell Structures
• Assembly, transport, and storage (cont.)
–Endoplasmic reticulum (ER) – site of cellular chemical
reactions – Highway of the cell
• Highly folded membranes – increase surface
area
• Found in cytoplasm – close to the nucleus
• Rough ER – has ribosomes attached to it –
makes proteins for membranes, proteins to
leave the cell (secreted), or proteins that are
transported to other organelles within the cell
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Eukaryotic Cell Structures
• Assembly, transport, and storage
-ER (cont.)
Smooth ER – used to produce other substances
besides proteins such as lipids
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• Several organelles are involved in making and processing proteins.
• The nucleus stores genetic information.
• Many processes occur in the endoplasmic reticulum.
• There are two types of endoplasmic reticulum.
• rough endoplasmic
• smooth endoplasmic
reticulum
reticulum
Eukaryotic Cell Structures
• Assembly, transport, and storage (cont.)
–Golgi apparatus (GA) – post office of the cell
• Found in the cytoplasm – closer to the plasma
membrane
• Flattened system of tubular membranes
• Modifies the proteins
• Packages and sorts proteins in transport
vesicles to be sent to their appropriate
destination inside or out of the cell
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Eukaryotic Cell Structures
• Assembly, transport, and storage (cont.)
–Transport vesicles – bud off the GA to carry the
packages of completed proteins to their
appropriate destination inside the cell or out of
the cell (secretion)
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• Several organelles are involved in making and processing proteins.
(continued)
• Ribosomes link amino acids to form proteins.
• Vesicles are membrane-bound sacs that hold materials.
Eukaryotic Cell Structures
• Assembly, transport, and storage
–Vacuoles – membrane-bound spaces in the
cytoplasm for temporary storage of:
• Food
• Waste
• Enzymes
• Water in some organisms
Plants have a large central vacuole for storage
of starch or water. Animals have several small
vacuoles
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• Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
Eukaryotic Cell Structures
• Assembly, transport, and storage (cont.)
–Lysosomes – membrane-bound organelle in
cytoplasm that contains digestive enzymes to
digest worn out organelles, food particles, and
viruses and bacteria.
• An intact membrane is important to contain
the digestive enzymes
• Can combine with a vacuole to digest the
contents of the vacuole
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Eukaryotic Cell Structures
• Assembly, transport, and storage (cont.)
– Lysosomes (cont.)
• Sometimes the lysosomes release their
digestive enzymes into the cytoplasm of a cell
if the organism wants to destroy a cell – this is
how a tadpole gets rid of its tail – this is also
how human fetuses get rid of their tail
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• Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
• Lysosomes contain enzymes to digest material.
Eukaryotic Cell Structures
• Energy Transformers – energy cannot be made – it
can only be transformed into another form
–The form of energy a cell uses is ATP – just the
same as a gas car can only use gasoline to do its
work; a cell can only use energy in the form of
ATP to do its work
–2 different organelles can transform energy
from a source outside the cell into ATP
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Eukaryotic Cell Structures
• Energy transformers (cont.)
–Chloroplasts – capture light energy from the sun
and transform it into ATP or store the light
energy in the form of sugars for later energy use
• Found in the cytoplasm of plants and some
protists
• Double membraned organelle – inner
membrane is highly folded
• Contains a green pigment called chlorophyll
that captures the energy from sunlight
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• Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
• Chloroplasts convert solar energy to chemical energy.
Eukaryotic Cell Structures
• Energy transformers (cont.)
–Mitochondria – takes the sugar produced by
chloroplasts and breaks it down to release the
energy stored in the sugar molecule and
transforms that energy into ATP – a form of
energy the cell can use
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Eukaryotic Cell Structures
• Energy transformers (cont.)
–Mitochondria (cont.)
• Found in the cytoplasm of all eukaryotic cells
– including plants cells
• Double membrane with inner membrane
highly folded
• Vary in number found in cells depending on
the cells need for energy – found in high
numbers in muscle cells
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• Other organelles have various functions.
• Mitochondria supply energy to the cell.
Eukaryotic Cell Structures
• Cytoskeleton – structure for support of the cell and
movement of organelles within the cell. Made up
of:
1. Microtubule – thin, hollow cylinders made of
protein
2. Microfilaments –thin, solid protein fibers
–Forms the framework of the cell – constantly
changing
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• Cells have an internal structure.
• The cytoskeleton has many functions.
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supports and shapes cell
helps position and transport organelles
provides strength
assists in cell division
aids in cell movement
Eukaryotic Cell Structures
• Structures for locomotion – located on the outside of cells
– Cilia – short, numerous , hair-like projections that move in wave-like motion
– found in our airways
– Flagella – longer projections that move in a whip-like motion – usually only
one or very few
– Both are used for movement of many unicellular organisms
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Eukaryotic Cell Structures
• Plant and animal cell comparisons
–Plant cells have three structures not found in
animal cells and are usually larger and have a
more fixed shape
• Cell wall – for extra structure and protection
• Chloroplast – to convert sunlight into ATP
• Large central vacuole – to store sugar as
starch and water
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Eukaryotic Cell Structures
• Plant and animal cell comparisons
–Animal cells – usually smaller than plant cells
• Centriole is the only organelle found in animal
cells and not plant cells
• Usually have many small vacuoles
• Could have flagella or cilia while a plant cell
will not
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• Other organelles have various functions.
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Mitochondria supply energy to the cell.
Vacuoles are fluid-filled sacs that hold materials.
Lysosomes contain enzymes to digest material.
Centrioles are tubes found in the
centrosomes.
Eukaryotic Cell Structures
• The eukaryotic cell has many different organelles
that each have their own function that contributes
the work of the whole cell.
• The fact that all these organelles have evolved and
can work together for the good of the whole cell
gives eukaryotic cells the ability to do a lot more
than prokaryotic cells
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Eukaryotic Cell Structures
• The nucleus and more precisely, the DNA within
the nucleus is what controls all the organelles
along with the plasma membrane.
• It does this by directing which proteins are
produced and when. These proteins, many of
which are enzymes, control all the chemical
reactions (metabolism) of a cell.
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