10/16/24, 11:09 Midterm 1 - Cell
AM Biology
Cells: The Fundamental Units of
Life Lecture 1
Lecture Contents
- Unity and diversity of cells the smallest units of life
- Cells under the microscope
- The prokaryotic cell
- The eukaryotic cell
- Model organisms
Unity and Diversity of Cells
- Cells vary enormously in appearance and function
- Living cells all have a similar basic chemistry
o DNA synthesis: replication RNA synthesis: transcription protein synthesis:
translation
o 20 amino acids
- Living cells are self-replicating collections of catalysts
o Amino acids proteins catalytic activity
o Sequence information synthesis of DNA and RNA through nucleotides and catalytic
activity
- All living cells have evolved from the same ancestral cell
Cells Under the Microscope
- Invention of light microscope (1665 Robert Hooke and later by Antoine Van
Leeuwenhoek) led to discovery of cells
- Light microscopes reveal some of a cell’s components
- The fine structure of a cell is revealed by electron microscopy
- Types of microscopy:
o Conventional light microscope: allows us to magnify up to 1000 times
to resolve details as small as 0.2 micrometers (200nm), a limitation
imposed by wavelike nature of light. Three things required for viewing
cells. First, a bright light must be focused onto the specimen by lenses
in the condenser. Second, the specimen must be carefully prepared to
allow light to pass through it. Third, an appropriate set of lenses
(objective, tube, and eyepiece) must be arranged to focus an image of
the specimen in the eye
o Fluorescence microscopy: fluorescent dyes used for staining
cells are detected. This is similar to ordinary microscope,
except that the illuminating light is passed through 2 sets of
filters. The first filters the light before it reaches the
specimen, passing only those wavelengths that excite the
particular fluorescent dye. The second blocks out this light
and passes only those wavelengths emitted when the dye
fluoresces. Dyed objects show up in bright color on a dark
background.
o Super-resolution fluorescence microscopy: several recent techniques allowed
fluorescence microscopes to break resolution limit of 200 nm. One technique uses a
sample that is labeled with molecules whose fluorescence can be reversibly switched
on and off by different colored lasers. The specimen is scanned by a set of two laser
beams, in which the central beam excites fluorescence in a very small spot of the
sample, while the second beam – wrapped around the first – switches off
fluorescence in surrounding area. A related approach allows the positions of
individual fluorescent molecules to be
about:blan 1/
k 7
, 10/16/24, 11:09 Midterm 1 - Cell
AM Biology
accurately mapped while others nearby are switched off. Both approaches slowly build
up an image with a resolution as lows as 20 nm.
o Transmission Electron Microscopy: (TEM) is similar to a light one, but
it uses a beam of electrons instead of a beam of light and magnetic coils
to focus the beam instead of glass lenses. The specimen is placed in a
vacuum and stained with electron-dense heavy metals that locally absorb
or scatter electrons, removing them from the beam as it passes through
the specimen.
o Scanning electron microscopy: (SEM) involves a specimen coated in
thin film of a heavy metal is scanned by a beam of electrons brought to a
focus on the specimen by magnetic coils that act as lenses. The
microscope creates 3D images.
The Prokaryotic Cell
- Prokaryotes are the most diverse and numerous cells on Earth
- The world of prokaryotes is divided into 2 domains: bacteria
and archaea
- Spherical cells (Strep); rod-shaped (E. coli, salmonella); spiral
cells (treponema pallidum)
- Cytoplasm, plasma membrane, cell wall, outer membrane
- Some bacterial cells are photosynthetic (Anabaena cylindrica and
phormidium laminosum)
The Eukaryotic Cells
- The nucleus is the information store of the cell
- Mitochondria generate usable energy from food molecules
o Early anaerobic eukaryotic cell engulfs aerobic bacterium
(has outer membrane and plasma membrane) loss of membrane derived from early
eukaryotic cell mitochondria with double membrane = early aerobic eukaryotic cell
- Chloroplasts capture energy from sunlight
o Early anaerobic eukaryotic cell engulfs photosynthetic bacterium loss of membrane
derived from the plasma membrane of the engulfing early eukaryotic cell chloroplasts
in photosynthetic eukaryotic cell
- Internal membranes create intracellular compartments with different functions
- The cytosol is a concentrated aqueous gel of large and small molecules
- The cytoskeleton is responsible for directed cell
movements
- The cytosol is far from static
- Eukaryotic cells may have originated as predators
- All cells are thought to have evolved from the same cell
- DNA can mutate and then be selected for evolution
- Eukaryotic cells may have originated as predators
Model Organisms
- Focus on E. coli
- Brewer’s yeast is a simple eukaryote
- Arabidopsis has been chosen as a model plant
- Model animals include flies, worms, fish, and mice
- Biologists also directly study humans and their cells
- Comparing genome sequences reveals life’s common heritage
- Genomes contain more than just genes
about:blan 2/
k 7
AM Biology
Cells: The Fundamental Units of
Life Lecture 1
Lecture Contents
- Unity and diversity of cells the smallest units of life
- Cells under the microscope
- The prokaryotic cell
- The eukaryotic cell
- Model organisms
Unity and Diversity of Cells
- Cells vary enormously in appearance and function
- Living cells all have a similar basic chemistry
o DNA synthesis: replication RNA synthesis: transcription protein synthesis:
translation
o 20 amino acids
- Living cells are self-replicating collections of catalysts
o Amino acids proteins catalytic activity
o Sequence information synthesis of DNA and RNA through nucleotides and catalytic
activity
- All living cells have evolved from the same ancestral cell
Cells Under the Microscope
- Invention of light microscope (1665 Robert Hooke and later by Antoine Van
Leeuwenhoek) led to discovery of cells
- Light microscopes reveal some of a cell’s components
- The fine structure of a cell is revealed by electron microscopy
- Types of microscopy:
o Conventional light microscope: allows us to magnify up to 1000 times
to resolve details as small as 0.2 micrometers (200nm), a limitation
imposed by wavelike nature of light. Three things required for viewing
cells. First, a bright light must be focused onto the specimen by lenses
in the condenser. Second, the specimen must be carefully prepared to
allow light to pass through it. Third, an appropriate set of lenses
(objective, tube, and eyepiece) must be arranged to focus an image of
the specimen in the eye
o Fluorescence microscopy: fluorescent dyes used for staining
cells are detected. This is similar to ordinary microscope,
except that the illuminating light is passed through 2 sets of
filters. The first filters the light before it reaches the
specimen, passing only those wavelengths that excite the
particular fluorescent dye. The second blocks out this light
and passes only those wavelengths emitted when the dye
fluoresces. Dyed objects show up in bright color on a dark
background.
o Super-resolution fluorescence microscopy: several recent techniques allowed
fluorescence microscopes to break resolution limit of 200 nm. One technique uses a
sample that is labeled with molecules whose fluorescence can be reversibly switched
on and off by different colored lasers. The specimen is scanned by a set of two laser
beams, in which the central beam excites fluorescence in a very small spot of the
sample, while the second beam – wrapped around the first – switches off
fluorescence in surrounding area. A related approach allows the positions of
individual fluorescent molecules to be
about:blan 1/
k 7
, 10/16/24, 11:09 Midterm 1 - Cell
AM Biology
accurately mapped while others nearby are switched off. Both approaches slowly build
up an image with a resolution as lows as 20 nm.
o Transmission Electron Microscopy: (TEM) is similar to a light one, but
it uses a beam of electrons instead of a beam of light and magnetic coils
to focus the beam instead of glass lenses. The specimen is placed in a
vacuum and stained with electron-dense heavy metals that locally absorb
or scatter electrons, removing them from the beam as it passes through
the specimen.
o Scanning electron microscopy: (SEM) involves a specimen coated in
thin film of a heavy metal is scanned by a beam of electrons brought to a
focus on the specimen by magnetic coils that act as lenses. The
microscope creates 3D images.
The Prokaryotic Cell
- Prokaryotes are the most diverse and numerous cells on Earth
- The world of prokaryotes is divided into 2 domains: bacteria
and archaea
- Spherical cells (Strep); rod-shaped (E. coli, salmonella); spiral
cells (treponema pallidum)
- Cytoplasm, plasma membrane, cell wall, outer membrane
- Some bacterial cells are photosynthetic (Anabaena cylindrica and
phormidium laminosum)
The Eukaryotic Cells
- The nucleus is the information store of the cell
- Mitochondria generate usable energy from food molecules
o Early anaerobic eukaryotic cell engulfs aerobic bacterium
(has outer membrane and plasma membrane) loss of membrane derived from early
eukaryotic cell mitochondria with double membrane = early aerobic eukaryotic cell
- Chloroplasts capture energy from sunlight
o Early anaerobic eukaryotic cell engulfs photosynthetic bacterium loss of membrane
derived from the plasma membrane of the engulfing early eukaryotic cell chloroplasts
in photosynthetic eukaryotic cell
- Internal membranes create intracellular compartments with different functions
- The cytosol is a concentrated aqueous gel of large and small molecules
- The cytoskeleton is responsible for directed cell
movements
- The cytosol is far from static
- Eukaryotic cells may have originated as predators
- All cells are thought to have evolved from the same cell
- DNA can mutate and then be selected for evolution
- Eukaryotic cells may have originated as predators
Model Organisms
- Focus on E. coli
- Brewer’s yeast is a simple eukaryote
- Arabidopsis has been chosen as a model plant
- Model animals include flies, worms, fish, and mice
- Biologists also directly study humans and their cells
- Comparing genome sequences reveals life’s common heritage
- Genomes contain more than just genes
about:blan 2/
k 7
