2. Cell Structure and Varieties Flashcards
Cell
a small membrane bound unit filled with a
concentrated aqueous solution of chemicals with reproduction capacity
How surface area-to-volume ratio constrains cell size
- cell surface area determines the amount of substances entering and exiting
the cell - To function, cells must maintain a large surface area to volume ratio
Microscope
A tool which allows us to see details and objects too small to be seen with the naked eyes
Robert Hooke
built the first compound microscope (two converging
lenses)
Anton Van Leeuwenhoek
(1670)
- observed living
microorganisms - called them animalcules
Matthias Shleiden (1838) and Theodor Schwann (1839)
Concluded all living things are made of cells
Cell theory (1838)
- Cells are the fundamental units of life
- All living organisms are composed of cells
- All cells come from preexisting cells
Modern cell theory
Modern cells evolved from a common ancestor
Different types of light microscopy
Bright-field microscopy
light passes directly
through the cells, ittle contrast and details are not distinguished
Different types of light microscopy
Phase-contrast microscopy
contrast is increased
by emphasizing differences in refractive index, enhances light and dark areas in the cell
Different types of light microscopy
Differential interference-contrast microscopy
two beams of polarized light are used, the
combined images look as if the cell is casting a
shadow on one side.
Different types of light microscopy
Stained bright-field microscopy
a stain enhances
contrast and reveals details not otherwise visible
Different types of light microscopy
Fluorescence microscopy
a natural substance in the cell or a fluorescent dye that binds to a specific cell material is stimulated by a beam of light and the longer wavelength florescent light is observed coming directly from the dye
Different types of light microscopy
Confocal microscopy
fluorescent materials are used
but adds a system of focusing both the stimulating and emitted light so that a single plane through the cell is seen
Max Knoll and
Ernst Ruska (1931)
invented
electron microscope
Transmission electron microscopy (TEM)
- a beam of electrons is focused on
the object by magnets - objects appear darker if they absorb the electrons
- If the electrons pass through they are detected on a fluorescent screen
- A region of a cell in a piece of testis
Scanning Electron Microscopy (SEM)
- electrons are directed to the surface of the sample
- they cause other electrons to be emitted
cytoplasm
Everything inside the cell (except nucleus if present)
Cytosol
the fluid cytoplasm not
contained inside another compartment
Prokaryotic Cell
does not have a nucleus or any other membrane-enclosed internal compartments
Eukaryotic Cell
contain membrane-enclosed compartments called organelles
Nucleus
most noticeable organelle in eukaryotes
All prokaryotes
-A cell membrane
-A nucleoid
-A cytoplasm
-Ribosomes (25 nm in diameter)
Specialized prokaryotes
-A cell wall and capsule
-Internal membranes
-Cytoskeleton
-Flagella, Pili and Fimbriae
Some prokaryotes swim using their flagella
function
Cytosol
contains dissolved nutrients, helps break down waste products, and moves material around the cell
function
Nucleus
the repository of genetic information and as the cell’s control center
function
Endoplasmic reticulum (ER)
calcium storage, protein synthesis and lipid metabolism
function
Golgi apparatus
transport, sorting and modification of both protein and lipid
function
Lysosomes
the digestive system of the cell, serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself
function
Endosomes
sorting and delivery of internalized material from the cell surface and the transport of materials from the Golgi to the lysosome or vacuole
function
Mitochondria
generate most of the chemical energy needed to power the cell’s biochemical reactions
function
Chloroplast
to absorb light—usually sunlight
function
Peroxisomes
sequester diverse oxidative reactions and play important roles in metabolism, reactive oxygen species detoxification, and signaling
The endomembrane
system includes
-Cell membrane
-Nuclear envelope
-Endoplasmic reticulum
-Golgi apparatus
-Lysosomes
Vesicles
transport substances between the various components of the endomembrane system
Cytoskeleton
-Cell support and shape maintenance
-Positioning of cell organelles and other particles within the cell
-Organelles and other particles movement around in the cell
-Cytoplasm movements (cytoplasmic streaming)
-Anchoring the cell in place by interacting with extracellular structures
Endosymbiosis
responsible for the appearance of mitochondria and chloroplasts
