Post on 03-Jan-2016
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Cell Structure and Function
Preview
• Cell characteristics and cell theory
• Overview of cell membrane
• Eukaryotic cells
• Eukaryotic organelles
• Prokaryotic cells
• How Cells Move
• Smallest unit of life
• Can survive on its own or has potential to do so
• Senses and responds to environment
• Has potential to reproduce
• Differ in:– Size– Shape – functions
Characteristics of Cells
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Cell Theory
1) Every organism is composed of one or
more cells
2) Cell is smallest unit having properties of
life
3) Continuity of life arises from growth and
division of single cells
Structure of Cells
All cells have three distinct sections:
Plasma Membrane
Nucleus (or nucleoid region in prokaryotes)
Cytoplasm
Cell• Plasma Membrane
• Nucleus
• Cytoplasm
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Preview of Cell Membranes
Plasma membranes are composed mostly of a lipid bilayer that prevents free passage of water soluble substances across it.
one layerof lipids
one layerof lipids
8Plasma Membrane
Other names for a cell membrane:
• Cytoplasmic membrane
• Semipermeable membrane
• Phospholipid bilayer
Eukaryotic Cells
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• Have a nucleus
• Have organelles – small, membrane bound “organs” in the cell that perform a specific job for the cell.
• Found in the Protista, Fungi, Plant, and Animal kingdoms
• Have 1000 times more DNA than prokaryotic cells
Organelle Functions
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nucleus - controls the cell’s activities Nuclear membrane – separates cytoplasm from
nuclear materialNucleolus – site of RNA and ribosome synthesisDNA – genetic material
cytoplasm – Space between nucleus and plasma membrane(cytosol) jellylike substance that fills the inside of a
cell , gives structure and shape
Cont.
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endoplasmic reticulum - "tunnels" in the cytoplasm that allow materials to move through the cell easier (subway system of the cell)Rough (RER) – makes proteins, covered in ribosomesSmooth (RER) - makes lipids, degrades fats,
detoxifies materialribosomes – attached to ER and scattered in cytoplasm,
make proteins mitochondrion – powerhouse, produce energy in the cell Golgi body - stores, processes, and secretes proteins
and lipids (post office)
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• vesicle- sacs that transport material in cell
• centrioles – centers that produce and organize structures that help in cell reproduction (animal cells only)
• lysosome – digest, recycles nutrients (suicide sack)
• cytoskeleton – structurally supports, gives shape & helps move cell components
Quick Check
1. List two parts of the cell theory.
2. Rough endoplasmic reticulum is responsible for making ___ for the cell.
3. List the four eukaryotic kingdoms
4. Centrioles are only found in ___ cells.
Eukaryotic Animal Cell Structure
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Plant vs. Animal Cell
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Plant Cells Only
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• cell wall - rigid surrounding of plant cells, protects, structural to support
• chloroplasts - contain chlorophyll in plants; this is where the plant’s food is produced by photosynthesis
• vacuoles - large bodies in plant cells that hold water, waste, etc.
A closer look at major organelles
19A closer look at the nucleus:
Nuclear Envelope/Membrane20
• Double lipid membrane with pores• Controls what goes in and out
–Pores control ions & water soluble materials entrance and exit
• Ribosomes on outer membrane • Membrane merges with ER• Nucleoplasm - semifluid interior of nucleus
Nuclear Envelope
Nucleolus
Mass of proteins that codes for rRNA (ribosomal RNA)
Synthesis of ribosomes and proteins
Genetic Material (DNA)
• Chromosome – one DNA molecule and the many proteins that are associated with it
• Chromatin – total collection of all DNA molecules and their associated proteins
• DNA + proteins=
chromatin
Chromatin strands
bunched together=
chromosome
A closer look at ER:
• Endoplasmic reticulum
• A flattened channel that starts at the nuclear envelope/membrane and folds back and forth
• Two typesRough (RER)– Has ribosomes attached
• Makes proteins
Smooth (SER)– Detoxifies drugs, makes lipids
A closer look at Golgi bodies:
• Vesicles pinch off of ER.• Fuse with Golgi bodies• Golgi bodies repackage and ship vesicles by
adding or removing molecules to proteins and lipids.
• Think post office
and stacks of
pancakes with
syrup!
A closer look at lysosomes:
• membrane-enclosed vesicles that contain powerful digestive enzymes – internal pH reaches 5.0
• Functions– digest foreign substances
and recycles own organelles– Autolysis– Suicide sac
Tay-Sachs Disorder
• Affects children of eastern European descent• Genetic disorder caused by absence of single
lysosomal enzyme– enzyme normally breaks down glycolipid
commonly found in nerve cells– as glycolipid accumulates, nerve cells lose
functionality– chromosome testing now available
A closer look at mitochondria:
• Mitochondria resemble bacteria– Have DNA, ribosomes– Divide on their own
• May have evolved from ancient bacteria that were engulfed but not digested
• Mitochondrial DNA (genes) are usually inherited only from the mother.
Mitochondria (cont.)• Double outer membrane• Inner folded membrane• Site of most of cells ATP
production• Only in eukaryotic cells• Site of aerobic respiration
(oxygen present)• Numerous in skeletonal cells
A closer look at chloroplasts (and other plastids):
• Plastids • Are organelles that function in
photosynthesis or storage in plants.• Three types
– Chloroplast– Chromoplasts– Amyloplasts
Cont.Chloroplast – • Conduct
photosynthesis• Enclosed by a double
membrane• Thylakoid stacks of
grana – Contain pigments
such as chlorophyll• Stroma fluid filled area
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Other Plastids
• Chromoplasts – No chlorophyll
– Abundance of carotenoids
– Color fruits and flowers red to yellow
• Amyloplasts– No pigments
– Store starch (tubers- potatoes)
A closer look at plant cell walls:
• Surrounds the plasma membrane
• Protects, supports and give shape to cell
• Porous – allows water and solutes to pass in/out
• In all plants
• Some protist and fungi
• Cuticle on outer most surfaces of plants
Even Cells Have a Skeleton• Cyto means cell
– So cytoskeleton means cell skeleton
• It is organized system of protein filaments in the cytoplasm.
• Some are permanent others are temporary
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Cytoskeletal Elements
microtubule
microfilament
intermediatefilament
Functions ofCytoskeletal Elements:
• Move organelles within the cytoplasm
• Assist in cell division
• Provide structure and support for the cell
• Can be used to identify cells
Prokaryotic Cells
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DNA is not enclosed in nucleus
Generally the smallest, simplest cells
No organelles
Most ancient form of life
Archaeans and bacteria the only representatives
Prokaryotic means “before the nucleus
Prokaryotic Cells
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Permeable, semi-rigid cell wall outside plasma membrane gives shape
Plasma membrane- semi-permeable to control what goes in and outCan contain pigments for photosynthesis
Polysaccharides are on surface to help them stick to objects or give a protective coating
1-2 Flagella – movement
Prokaryotic Cells
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Pili – helps stick to surfaces and exchange genetic material
Cytoplasm – semifluid material inside cellRibosomes – scattered in cytoplasm,
protein making siteNucleoid – concentrated region where DNA
is located. DNA is circular. Plasmids – scattered in cytoplasm, these
can confer selective advantages such as antibiotic resistance. Contain just a few genes.
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Prokaryotic Structure
DNA
pilus
flagellum
cytoplasm with ribosomes
capsulecell wall
plasma membrane
Quick Check
How Do Cells Move?
• Cells must have ATP in order for movement to take place.
• Cilia, flagella and false feet are all ways that cells move.
Cilia, Flagella and False Feet• Cilia
– many small projections on cell membranes working in together for movement
– Along trachea, oviducts in humans
• Flagella – generally 1-2 projections that move an object– Sperm is the only flagella in humans
• Pseudopodia– False foot– Temporary extension of cytoplasm for movement
Protists use all three.
• Cilia pseudopodia
• flagella
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Lab Notes
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Lead to the ability to develop the Cell TheoryCreate detailed images of something that is
otherwise too small to seeLight microscopes
Simple or compoundUses two sets of lenses to magnify the living or dead
image
Electron microscopesTransmission EM or Scanning EMUses electrons view either inside or surface of a dead
cell
Microscopes
New Terms
• Wavelength – distance from the peak of a wave to the peak of another wave
• Ocular Lens enlarges 10x inside the eye piece
• Objective lens magnify at various levels
• Stage supports the object viewed on slide
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• Create detailed images of something that
is otherwise too small to see
• Light microscopes
– Simple or compound
• Electron microscopes
– Transmission EM or Scanning EM
Microscopes
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Limitations of Light Microscopy
• Wavelengths of light are 400-750 nm
• If a structure is less than one-half of a wavelength long, it will not be visible
• Light microscopes can resolve objects down to about 200 nm in size
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Electron Microscopy
• Uses streams of accelerated electrons rather than light
• Electrons are focused by magnets rather than glass lenses
• Can resolve structures down to 0.5 nm
SEM- surface views
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Electron Microscopes
TEM
SEM
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TEM- inside cell view
Image comparison
• The electron microscope allows a smaller object to seen
• The electron microscope is not limited by the wavelength of light
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