Biology & Science: Cell Structure Based on theory

This explains about cell structure and its functions. Basically, Cells are the smallest parts of any organisms that can still be clearly identified as either being that organism, or originating in that organism - Matthias Schleiden (botanist) and Theodor Schwann (zoologist)

1. Cells
1. What’s a cell
2. Cell structure and functions

2. The Cell Theory
•Cells are the smallest parts of any organisms that
can still be clearly identified as either being that
organism, or originating in that organism -Matthias
Schleiden (botanist) and Theodor Schwann
(zoologist)
•All cells are derived from cells -Rudolf Virchow
•All cells can be traced back to a common ancient
ancestor -August Weissman (an extension of
Virchow’s concept)

3. Cells Are Small
•Most cells ~1mm (1/10
6
m) to 1
mm in diameter
•Some are bigger

4. Cells are Compartmentalized
•All cells are bounded by a plasma membrane
–Protects cellular reactions from the environment
•All cells have cytoplasm
–Fluid compartment of the ‘body’ of the cell called
cytosol
–Internal organelles found within the cytosol
•Cells have internal compartments
–Keep different reactions apart
–Keep compatible reactions together
•Eukaryotic cells have membrane-bounded organelles
•Membranes are very important to the cell
•Cellular membranes
–Transport materials in/out of cell
–Locate/hold reactions (in/on organelles)

5. Distinguishing Features of the Two
Major Cell Types
Prokaryotes Eukaryotes
No nucleus; nucleoidNucleus surrounds genome/DNA
Very small (~1-10 m) Larger (~10-1000 m)
Few internal
membranes
Many internal membranes
No cytoskeleton Extensive cytoskeleton intracellular filaments
Corkscrew flagellum
made of a single protein
Complex flagella made of >300 proteins!
Peptidoglycan cell wallCellulosic cell walls if present
Small ribosomes (70S)Big ribosomes (80S)

6. An Animal Cell
A pancreatic cell
that makes
digestive
enzymes

7. A Plant Cell
•A
photosynthetic
plant cell

8. Eukaryotic Endomembrane System
•Nucleus: Birthplace of the endomembranes
–DNA held in chromosomes: cellular library of information
–Nucleolus: birthplace of ribosomes
•Endoplasmic reticulum(rER and sER): cell’s factories
–Rough endoplasmic reticulum(rER) makes secreted proteins and
integral membrane proteins (IMPs) and modifies proteins
–Smooth ER(sER) makes lipid molecules, such as steroids, and
adds lipids to proteins
•Golgi apparatus
–Modifies proteins made in the rER
•Lysosomes
–The “destroyer”: proteolytic, lipolytic enzymes, acid pH
•Vacuolesand microbodies
–Storage & concentration of cellular waste, nutrients, and enzymes

9. The nucleus
•Nucleus
•Chromatin
•Condensed
heterochromatin
•Noncondensed
•Nucleolus
•Birthplace of
ribosomes
•Double-layered membrane
of nuclear envelope
•Nuclear pores

10. Endomembranes and
Secretion
•The nucleus produces the Rough
Endoplasmic Reticulum (RER), a
system of flattened membranes
•The RER makes proteins that are
secreted or inserted into membranes
•The RER passes its protein products
via transport vesicles to the Golgi
Apparatus, which are also flattened
membrane systems, which processes
them . . .
•And sends them to various locations,
including the plasma membrane
•Note that proteins produced inside
the RER stay inside the Golgi and
transport vesicles, but are expressed
on the surface of the plasma
membrane

11. Ribosomes
•Made of 3 RNA strands and 75 different
proteins
•Free: suspended in cytosol
•Bound: associated with rough
endoplasmic reticulum
•Assemble proteins by dehydration
synthesis

12. Smooth Endoplasmic
Reticulum
•The smooth endoplasmic
reticulum (SER) is tubular, unlike
the RER.
•It receives membrane from the
RER.
•Is tubular, (unlike the RER, which
consists of flattened membranes)
•Mitochondria are shown here
also

13. Non-Endomembrane Organelles
•Mitochondrion
–Energy organelle
–Aerobic respiration
–Derived from an ancient bacterium engulfed by a
heterotrophic prokaryotic ancestor of the eukaryotes
(’urkaryote’)
–Ancient bacterium became an endosymbiotic organism
•Chloroplast
–Light-energy collection organelle
–Makes oxygen
–Photosynthetic bacteria and chloroplasts changed the world
–Production of oxygen changed ancient atmosphere
–Derived from bacterium, like mitochondrion

14. Mitochondria
•Sausage-shaped
•Outerand inner
membranes
•Inner membrane
infolded to form
cristae

15. Chloroplast
•Similar in
structure to
mitochondrion
•Photosynthetic
membranes in
thylakoids