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8/9/2019 Lect Biod5
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Lecture BIOD 5: Eukaryotic Cell Structure &Function
- The cell is the basic unit of life.
- Based on their cellular structures, all living cells can be divided into 2 groups:
prokaryoticand eukaryotic.
- Only bacteriahave prokaryoticcell types.
- Animals, plants, fungi, protozoans, and algae all possess eukaryoticcell types.
- Fungi, protozoans, an algaeare Eukaryoticmicroorganisms.
-These microorganisms are very comple and prominent members of the ecosystem.
- !ungi "# some algae$ are useful in industrial microbiology.- %any fungi and protozoa are ma&or human pathogens' e.g. %alaria and African
sleeping sic(ness.
- )ro(aryotic cells are generally much smaller and more simple than eu(aryotic.
- )ro(aryotic cells are, in fact, able to be structurally more simple because of theirsmall size.
- *n the first part of this section, the focus is on the structure and function of the
eu(aryotic cell.
- At the end of the section, pro(aryotic and eucaryotic cells +ill be compared.
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Candida albicans
O!er!ie" o# Eucaryotic Cell Structure:
- The most obvious difference bet+een )ro. # uc. *s their use of membranes.
- ucaryotic cells have membrane-delimited nuclei, and have a variety of comple
membranous organellesin the cytoplasmic matri' "organellesare intracellular
structures that perform specific functions in cells$.
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Cytoplas$ic %atri:
- arge part of it is +ater "/0-13$.
- The 4environment5 of the organelles, and
location of important biochemical
processes.- 6ell is not 7&ust a bag in a bubble7. ots of
internal #ibers8 internal 4s(eleton5'
capable of being assembled, bro(en do+n in
minutes' involved in cell movement, shape
changes # division.- !ibers include $icro#ila$ents,
$icrotubules "e..g. form 6ilia and !lagella$
and Inter$eiate #ila$ents'
- Cell (allsalso, provide a rigid structure
around cells. %ade of cellulose in the case
of plants and fungi.
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Enoplas$ic )eticulu$ *E)+:
E)is a maze of parallel membranous tubules and
flattened sacs surrounding the nucleus that connects
+ith the nuclear membrane and runs throughout the
cytoplasm.- 9 provides a surface area for protein and lipid
synthesis'
- forms a path+ay for transporting molecules +ithi
n
the cell' and
- provides a storage area for molecules the cell has
synthesized.
- There are t+o distinct regions of the 9: the roug-
E)and the s$oot- E).
- 9 +ith riboso$es attac-eis called roug- E)
and is involved in protein synt-esis, prouction
o# ne" $e$brane, $oi#ication o# ne"ly #or$e
proteins, an transport o# t-ese proteins an
$e$brane to ot-er locations "it-in t-e cell.
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- 9 "it-out riboso$esis called s$oot-
E)and contains enzymes for lipi
biosynt-esis, especially the synthesis of
phospholipids and steroids.The smoothendoplasmic reticulum formstransition
!esicles to trans#er $olecules prouce in
t-e roug- E) to t-e .olgi apparatusan
ot-er parts o# t-e cell
.olgi /pparatus:
- The olgi apparatus "A$ consists of ;-20 flattened and stac(ed
sacli(e structures called cisternae. A comple net+or( of tubules
and !esiclesis located at the edges of the cisternae.
A sorts proteins and lipids received from the 9'
- modifies certain proteins and glycoproteins' and
- sorts and pac(ages these molecules into vesicles for transport to
other parts of the cell or secretion from the cell.
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Lysoso$es an Enocytosis:
- Lysoso$es, synthesized by the E)and the ./, are membrane-enclosed spheres
typically about 00 nm in diameter that contain po+erful igesti!e enzy$es.
- They function to igest materials that enter byenocytosis'
-
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%itoc-onria:
- %itochondria are rod-shaped structures ranging from 2 to
1 nm in length.
- !ound throughout the cytoplasm' up to 203 of the cell=s
volume.- %itochondria are surroune by t"o $e$branes.
- They have their o+n A and ribosomes
- !re?uently called the 4po+erhouses5 of the cell
- They are the centers forrespiratory catabolis$, during +hich oygen is combined
+ith chemicals to brea( do+n foods, and generate cell energy.
C-loroplasts:
- 6hloroplasts are dis(-shaped structures ranging from to
@0 m in length.
- i(e mitochondria, chloroplasts are surrounded by aninner and an outer membrane.
- 6ontain stac(s of t-ylakois, +here green pigmented
chlorophyll is embedded in membrane to trap lig-t.
- se lig-t energyto convert COand "aterto carbo-yratesand O, that is6-otosynt-esis.
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0ucleus: - is a membrane-delimited spherical body
filled +ith dense fibrous material called
c-ro$atin.
- A is organized as multiple chromosomes
located +ithin a nucleus.
- The nucleus is separated from the
cytoplasm by a nuclear $e$brane'
- The nuclear membrane has porest-at
connect "it- t-e E)'
- 0ucleolus is the most noticeable structure +ithin the nucleus, +here riboso$al
subunitsare assembled.
- The nucleus divides by $itosis, a process that ensures each daughter cell receives the
same number of chromosomes as the original parent cell.
- aploid se cellsare produced from diploid cells by $eiosis,
%eiosisis the nuclear division that occurs as a part of seual reproduction +herein
the daughter cell receives the haploid number of chromosomes.
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Flagella an Cilia:
- !lagella are long and fe+ in number
+hereas cilia are short and numerous.
- Both consist of 7 #use pairs o# protein
$icrotubules +ith side arms of the motormolecule dynein that originate from a
centriole.
- These #or$ a ring aroun an inner central pair of microtubules that arise from a
plate near the cell surface.
- !lagella and cilia function in loco$otion. 6ilia also function to move various material
that may surround a cell.
6rokaryotic *6+8s Eu9aryotic *E+ Cells:
- ): nuclear body is called nucleoid not bound by membrane' : bound by membrane
called nucleus.
- ): one circular chromosome composed of A Chistone-li(e proteins' : @ or more
paired linear chromosomes composed of A C histone proteins.
- ): no nucleolus' : nucleolus present.
- ): divide by binary fission' : divide by mitosis "diploid$ # se cells produced bymeiosis.
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- ): cytoplasmic membrane "6%$ is a fluid phospholipid bilayer +ithout carbohydrates,
contains sterol-li(e molecules called hopanoids, incapable of endocytosis # eocytosis.
- : 6% is a fluid phosphate bilayer, containing sterols # carbohydrates, capable of
endocytosis # eocytosis.
- ): 9ibosomes 0D # ;0D' : 9ibosomes E0D # F0D- ): %itochondria, 9, A, Gacuoles, ysosomes, chloroplasts are absent. >o
cytos(eleton.
- ): cell +alls composed of peptidoglycan' : 6H composed of cellulose or 6hitin.
- ): no cilia, flagella is composed of single rotating fibril' : flagella # cilia involved in
locomotion, consist of a distinct arrangement of sliding microtubules.
)epresentati!e organis$s:
- ): Bacteria "ubacteria # Archaebacteria$
- : Algae, )rotozoans, and !ungi. And of course Animals and )lants.
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