A tour of a cell. Key Concepts To study cells, biologists use microscopes and the tools of...
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Transcript of A tour of a cell. Key Concepts To study cells, biologists use microscopes and the tools of...
Key Concepts• To study cells, biologists use microscopes and the
tools of biochemistry• Eukaryotic cells have internal membranes that
compartmentalize their functions• The eukaryotic cell’s genetic instructions are
housed in the nucleus and carried out by the ribosomes
• The endomembrane system regulates protein traffic and performs metabolic functions in the cell
• Mitochondria and chloroplasts change energy from one form to another
• The cytoskeleton is a network of fibers that organizes structures and activities in the cell
Cell theory emerges
• Every organism consists of one or more cells
• The cell is the structural and functional unit of life
• A cell is the smallest unit of life
• Cells contain hereditary information which they pass on to their offspring during division
Our ability to study cells has improved dramatically
Light microscope uses visible light to illuminate a specimen.
Our ability to study cells has improved dramatically
Fluorescence microscope allows users to view light emitted from the specimen when it is illuminated with a specific wavelength of light.
Our ability to study cells has improved dramatically
Electron microscopes use electrons instead of light.-Transmission electron microscope- electrons form an image after passing through the specimen -Scanning electron microscope- image forms from
electrons that bounce off the surface of the specimen
What have we learned about cells?
There are two main types of cells, prokaryotic and eukaryotic
Prokaryotes Eukaryotes
How are they similar?
Which organisms fall into each category?
How do they differ?
Prokaryotes EukaryotesHow are they similar?
Which organisms fall into each category?
How do they differ?
Prokaryotes EukaryotesHow are they similar?
-All cells have a plasma membrane-All cells contain DNA-All cells contain ribosomes-All cells have cytosol (fluid mixture of water sugar, ions, proteins)-All cells are small (need a large surface are to volume ratio)
Which organisms fall into each category?
How do they differ?
Prokaryotes EukaryotesHow are they similar?
-All cells have a plasma membrane-All cells contain DNA-All cells contain ribosomes-All cells have cytosol (fluid mixture of water sugar, ions, proteins)-All cells are small (need a large surface are to volume ratio)
Which organisms fall into each category?
-Bacteria-Archea
-Eukaryotes (plants, animals, protists, fungi)
How do they differ?
Prokaryotes EukaryotesHow are they similar?
-All cells have a plasma membrane-All cells contain DNA-All cells contain ribosomes-All cells have cytosol (fluid mixture of water sugar, ions, proteins)-All cells are small (need a large surface are to volume ratio)
Which organisms fall into each category?
-Bacteria-Archea
-Eukaryotes (plants, animals, protists, fungi)
How do they differ?
-Single celled-Not divided into functional compartments
-small in size (1-5µm)-cell wall surrounding the plasma membrane
-single chromosome in a nucleoid region (not membrane-enclosed) also in plasmids (small circular strands of DNA)
-Can be multicellular-Divided into functional compartments (or organelles)-larger in size (10-100µm)-not all eukaryotes have a cell wall surrounding the plasma membrane-many chromosomes in a nucleus (membrane-enclosed)
The eukaryotic cell’s genetic instructions are housed in the nucleus
and carried out by the ribosomes
The eukaryotic cell’s genetic instructions are housed in the nucleus
and carried out by the ribosomesNucleus • Enclosed by the nuclear
envelope• Contains most of the
genes in the eukaryotic cells
• DNA is organized into chromosomes inside the nucleus
• Contains a nucleolus-a place of RNA and ribosome synthesis
The eukaryotic cell’s genetic instructions are housed in the nucleus
and carried out by the ribosomesNucleus • Enclosed by the nuclear
envelope• Contains most of the
genes in the eukaryotic cells
• DNA is organized into chromosomes inside the nucleus
• Contains a nucleolus-a place of RNA and ribosome synthesis
What is a ribosome?
The eukaryotic cell’s genetic instructions are housed in the nucleus
and carried out by the ribosomes
Ribosomes
• Complexes of rRNA and proteins
• They are located on the ER or free in cytoplasm
• Their function is protein synthesis
The eukaryotic cell’s genetic instructions are housed in the nucleus
and carried out by the ribosomes
The eukaryotic cell’s genetic instructions are housed in the nucleus
and carried out by the ribosomes
Are there analogous entities in a city?•DNA•Nucleus•Nuclear envelope•Ribosomes
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellEndomembrane systemIncludes:•Nuclear envelope•ER•Golgi•Lysosomes•Vacuoles•Plasma membrane
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellEndoplasmic reticulumSmooth v. Rough
Smooth ER•lacks ribosomes•Involved in synthesis of lipids, metabolism of carbohydrates, and detoxification of poisons
Rough ER•Has attached ribosomes•Makes proteins and phospholipids
Smooth ER
Rough ER
Nuclear envelope
Rough ERSmooth ER
ER lumen
200 nm
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellEndoplasmic reticulumSmooth v. Rough
Smooth ER•lacks ribosomes•Involved in synthesis of lipids, metabolism of carbohydrates, and detoxification of poisons
Rough ER•Has attached ribosomes•Makes proteins and phospholipids
Smooth ER
Rough ER
Nuclear envelope
Rough ERSmooth ER
ER lumen
200 nm
Transport vesicles-transport materials from the ER to the Golgi
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellGolgi•Looks like a stack of pancakes
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellGolgi•Looks like a stack of pancakes•Receives, modifies, manufactures, and stores products of the ER
cis face(“receiving” side of Golgi apparatus)
trans face(“shipping” side of Golgi apparatus)
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellGolgi•Looks like a stack of pancakes•Receives, modifies, manufactures, and stores products of the ER•Has a cis and trans side
cis face(“receiving” side of Golgi apparatus)
trans face(“shipping” side of Golgi apparatus)
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellLysosomes (digestive compartments in animal cells)•Sac filled with hydrolytic enzymes (produced by the Golgi)•Its function is to digest macromolecules•Monomers are released to the cytosol for reuse
Nucleus 1 µm
Lysosome
DigestiveenzymesLysosome
Plasmamembrane
Food vacuole
Digestion
Peroxisome
Vesicle
Lysosome
Mitochondrion
Peroxisomefragment
Mitochondrionfragment
Vesicle containingtwo damaged organelles
1 µm
Digestion
The endomembrane system regulates protein traffic and performs metabolic
functions in the cellVacuolesHave diverse roles•Important in storage•Can conduct hydrolysis
Central vacuole in plants•Hold reserves of organic compounds•Sequester toxins•Helps maintain turgor
Central vacuole
Cytosol
Central vacuole
Nucleus
Cell wall
Chloroplast
The endomembrane system regulates protein traffic and performs metabolic
functions in the cell
Smooth ER
Nucleus
Rough ER
Plasma membrane
cis Golgi
trans Golgi
The endomembrane system regulates protein traffic and performs metabolic
functions in the cell
Are there analogous entities in a city?•Endoplasmic reticulum•Golgi•Lysosomes•Vacuoles•Plasma membrane
Mitochondria and chloroplasts change energy from one form to another
Mitochondria • Found in all eukaryotic cells (about 1-10 µm long)• Contains DNA• Double membrane-bound organelle• Can reproduce on their own• Sites of cellular respiration
Free ribosomesin the mitochondrial matrix
Intermembrane spaceOuter membrane
Inner membrane
CristaeMatrix
0.1 µm
Mitochondria and chloroplasts change energy from one form to another
Chloroplasts• Found in plants• Contains DNA• More than one membrane• Can reproduce on their own• Enable plants to convert solar energy to chemical energy (via
photosynthesis)
Ribosomes
Thylakoid
Stroma
Granum
Inner and outer membranes
1 µm
Mitochondria and chloroplasts change energy from one form to another
• Specialized metabolic compartments
• Bounded by a single membrane
• Peroxisomes produce hydrogen peroxide and convert it to water
• Oxygen is used to break down different types of molecules (i.e. fatty acids)
Peroxisomes
ChloroplastPeroxisome
Mitochondrion
Mitochondria and chloroplasts change energy from one form to another
Are there analogous entities in a city?•Chloroplasts•Mitochondria
The cytoskeleton is a network of fibers that organizes structures and activities in
the cellThe functions of the cytoskeleton are diverse•Gives mechanical support to maintain cell shape•Providing anchoring for organelles•Can change the shape of a cell•Can move a cell from point A to point B •Can move cell parts
The cytoskeleton is a network of fibers that organizes structures and activities in
the cellThe components of the cytoskeleton are diverse•Microtubules•Microfilaments•Intermediate filaments
The cytoskeleton is a network of fibers that organizes structures and activities in
the cellMicrotubulesWhat are they?
•Hollow rods•25 nm in diameter•Made of tubulin•Cable of growing and shrinking by adding or subtracting tubulin
What do they do?•Compression resistant•Shape and support the cell•Tracks along which cellular components move
The cytoskeleton is a network of fibers that organizes structures and activities in the cellMicrotubulesCilia and flagella
•Microtubule-containing extensions of the cell•Locomotion appendages•Both are made of a core of microtubule sheathed in an extension of the plasma membrane
•Cilia and flagella are anchored by a basal body •Eukaryotes have a 9 + 2 arrangement •Each doublet has a dynein (motor protein) associated with it
The cytoskeleton is a network of fibers that organizes structures and activities in the cellMicrofilamentsWhat are they?•Solid rods (7nm in diameter)•Twisted double chain of actin subunits•Can also form branched networksWhat do they do?•Withstand tension (pulling forces)•Network of microfilaments inside the plasma membrane keep cell shape (the cortex)•Important in muscle contraction
Muscle cell
Actin filament
Myosin filamentMyosin arm
(a) Myosin motors in muscle cell contraction
Cortex (outer cytoplasm):gel with actin network
Inner cytoplasm: solwith actin subunits
Extendingpseudopodium
(b) Amoeboid movement
Nonmoving corticalcytoplasm (gel)
Chloroplast
Streamingcytoplasm(sol) Vacuole
Cell wall
Parallel actinfilaments
The cytoskeleton is a network of fibers that organizes structures and activities in the cell
Intermediate filamentsWhat are they?•Fibrous proteins supercoiled into thicker cables•8-12 nm•Formed from diverse proteins including keratinsWhat do they do?•Maintain cell shape (tension-bearing elements)•Anchor the nucleus and other organelles
Key Concepts• To study cells, biologists use microscopes and the
tools of biochemistry• Eukaryotic cells have internal membranes that
compartmentalize their functions• The eukaryotic cell’s genetic instructions are housed
in the nucleus and carried out by the ribosomes• The endomembrane system regulates protein traffic
and performs metabolic functions in the cell• Mitochondria and chloroplasts change energy from
one form to another• The cytoskeleton is a network of fibers that
organizes structures and activities in the cell