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1
Chapter 1: the cell
(20μm)
Common features of plant
and animal cells:
-
Thin cell surface membrane
(plasma membrane)
Nucleus
Chromatin _ DNA _ nucleolus
Cytoplasm
Organelles
Mitochondria ( singular:
mitochondrion)
Golgi apparatus
(40 μm)
2
Differences between animal and plant cell:
-
Centrioles
Cell walls and plasmodata
Vacuoles
Chloroplasts
Microscopes:
Feature
Light
Electron
Source of radiance
Light
Electron
Wavelength of radiation
400-700 nm
∓0
...
1-0
...
o Water boils in RT in a vacuum, so specimen should be dead
...
o Has no units and is calibrated by the stage micrometer which has an accurate scale (in
mm) and provides
reference dimensions
...
The amount of detail that
can be seen- higher resolution, higher detail
...
▪ Electrons have extremely short wavelength
...
4
Nucleus:
●
●
●
●
●
Largest cell organelle
Surrounded by 2 membranes ( nuclear envelope)
Nuclear envelope has many small pores called nuclear pores ( allow and control
exchange between the nucleus and the cytoplasm)
Chromosomes ( loosely coiled = chromatin) ( contain DNA - organized into functional
units called genes)
10 µm
Endoplasmic reticulum and ribosomes:
• Rough endoplasmic reticulum: 80S ribosomes of the rough endoplasmic reticulum are sites
for protein synthesis and produce the rough appearance
...
E
...
Made of two-dimensional flattened sacs, which are membrane-enclosed structures
...
Transport
vesicles bud off from the RER and join forming the Golgi body
...
5
Meshwork of tubular membrane vesicles with fluid filled sacs that have no ribosome
on its surface
• Ribosomes: the site at which mRNA (transcribed from the nucleus) is translated into
polypeptides with the help of tRNA, therefore help with protein synthesis
...
E
...
-
Golgi body:
•Golgi body/complex/apparatus: stack of flattened sacs formed by transport vesicles which
bud off of the RER, and broken down to form Golgi vesicles
...
Makes lysosomes, glycoproteins and functioning proteins
...
1-0
...
They
contain digestive (hydrolytic) enzymes that’s kept separate from rest of cell to prevent
damage
...
old organelles or whole cells, in
WBC to digest bacteria
...
Has a matrix that contains 70S ribosomes and
circular DNA which is used to make some of the mitochondrion’s own proteins
...
Intermembrane space: space between the two membranes
...
Inner membrane: selective barrier controlling entrance of ions and molecules into the
matrix
...
The energy carrying molecule produced in mitochondria that spreads to parts where
needed
...
• Endosymbiont theory: mitochondria and chloroplast were bacteria that now live inside
larger cells of animals and plants, which is why chloroplast and mitochondria
have circular DNA
...
Extremely thin with trilaminar appearance
- It is comprised of phospholipid bilayers which are assembled with the hydrophilic
phosphate heads facing the aqueous environment (inside and outside the cell) and
the hydrophobic tails facing each other
...
absorption in the gut and reabsorption in the kidneys
Microtubules and microtubule organising centers ( MTOCs) :
-
Microtubules: long hollow tubes that make up the cytoskeleton which helps determine
cell shape
...
Dimers join end to end to form protofilaments (polymerisation)
...
Forms an intracellular transport system by moving along secretory vesicles,
organelles and cell components on its outer surface
...
Centriole: formed by 9 triplets of microtubules
...
Centrioles duplicate, and a pair of centrioles then move to opposite poles of the cell
(2 centrosome regions), thus separating sister chromatids during nuclear division
...
Microtubules
extending from basal bodies into cilia and flagella help with their beating movements
...
-
It has a double membrane and contains flattened sacs known as thylakoids
...
Thylakoids stacked on top of each other to form grana
...
These structures are present in a matrix called the
stroma
...
10
Cell wall:
•Cell wall (10 nm): rigid as it contains fibres of cellulose (polysaccharide)
...
May be reinforced by lignin for extra strength
...
11
Plasmodesmata:
• Plasmodesmata: pore-like structures found in cell walls that allow a link between
neighbouring cells by fine threads of cytoplasm
...
12
Two fundamentally different types of cell:
Eukaryotic cells: organisms with a true nucleus and have membrane bound organelles eg
animals, plants, fungi,protoctista
...
• Viruses (20-300 nm): non-cellular and are parasitic as they reproduce by infecting
and taking over living cells
...
13
Feature
Prokaryotes
Eukaryotes
Diameter
0