Post on 07-Jul-2018
8/19/2019 Cells Revision - IBBIONINJA
1/24
CELL
8/19/2019 Cells Revision - IBBIONINJA
2/24
Cells
2.1 Cell Theory2.1.1 Outline the cell theory
The cell theory states that:
1. All living things are composed of cells (or cell products)
2. The cell is the smallest unit of life
3. Cells only arise from pre-eisting cells
2.1.2 Discuss the evidence for the cell theory
Microscopes:
!icroscopes have increased man"s a#ility to visualise tiny o#$ects
All living things %hen vie%ed under a microscope have #een found to #e made of
cells and cell products (e.g. hair) Note: Certain types of cells do not conform to the standard notion of %hat
constitutes a cell
!uscle cells contain multiple nuclei
&ungal hyphae consist of multiple cells that share a continuous cytoplasm
'ight vs lectron !icroscopes
Experimental Evidence:
Cells removed from tissues can survive independently for short periods of time
othing smaller than a cell has #een found to #e a#le to live independently
periments #y &rancesco *edi and 'ouis +asteur have demonstrated that cells
cannot gro% in sealed and sterile conditions
,istory of the Cell Theory
2.1.3 State that unicellular organisms carry out all the functions of life
nicellular organisms (such as amoe#a paramecium euglena and #acterium) are the
smallest organisms capa#le of independent life.
All living things share / #asic characteristics:
ovement: 'iving things sho% movement either eternally or internally
R
eproduction: 'iving things produce offspring either seually or aseually Sensitivity: 'iving things can respond to and interact %ith the environment
Growth: 'iving things can gro% or change si0e shape
Respiration: 'iving things use su#stances from the environment to mae
energy
Excretion: 'iving things ehi#it the removal of %astes
8/19/2019 Cells Revision - IBBIONINJA
3/24
Nutrition: 'iving things echange materials and gases %ith the environment
2.1.4 Compare the relative sizes of molecules, cell memrane thic!ness, viruses,
acteria, organelles and cells, using appropriate S" units
Relative sizes: Unit Conversion Table:
A molecule 1 nm
Cell mem#rane thicness /.4 nm 5irus 166 nm (range: 26 - 266 nm)
7acteria 1 - 4 um
8rganelles 916 um
uaryotic cells 9166 um
iagram of the *elative ;i0es and ;cale of 7iological !aterials
Cell ;i0e and ;cale ('earn
8/19/2019 Cells Revision - IBBIONINJA
4/24
Magnification = Size of image (with ruler) ÷ Actual size of object (according to
scale bar)
To calculate the actual size of a magnified specimen the equation is simply re-arranged:
Actual size = Size of image (with ruler)> !agnification 2.1.% &'plain the importance of the surface area to volume ratio as a factor limiting cell
size
The rate of meta#olism of a cell is a function of its mass volume
The rate of material echange in and out of a cell is a function of its surface area
As the cell gro%s volume increases faster than surface area (leading to a
decreased ;A:5ol ratio)
?f the meta#olic rate is greater than the rate of echange of vital materials and
%astes the cell %ill eventually die
,ence the cell must conse=uently divide in order to restore a via#le ;A:5ol ratio
and survive Cells and tissues specialised for gas or material echange (e.g. alveoli) %ill
increase their surface area to optimise the transfer of materials
!icrovilli increase surface area allo%ing for a more efficient echange of materials
heat
2.1.( State that multicellular organisms sho$ emergent properties
mergent properties arise from the interaction of component parts: the %hole is greater
than the sum of its parts
!ulticellular organisms are capa#le of completing functions that individual cells could
not undertae - this is due to the interaction #et%een cells producing ne% functions
8/19/2019 Cells Revision - IBBIONINJA
5/24
?n multicellular organisms:
Cells may group together to form tissues
8rgans are then formed from the functional grouping of multiple tissues
8rgans that interact may form organ systems capa#le of carrying out specific
#ody functions
8rgan systems carry out the life functions re=uired #y an organism
'evels of Anatomical 8rganisation
2.1.) &'plain
that cells in
multicellular organisms
differentiate to carry out specialised functions y e'pressing
some of their genes and not others
All cells of an individual organisms share an identical genome - each cell
contains the entire set of genetic instructions for that organism
The activation of different instructions (genes) %ithin a given cell #y chemical
signals %ill cause it to differentiate from other cells lie it
ifferentiation is the process during development %here#y ne%ly formed cells
#ecome more specialised and distinct from one another as they mature
Active genes are usually pacaged in an epanded and accessi#le form
(euchromatin) %hile inactive genes are mainly pacaged in a condensed form
(heterochromatin)
ifferentiated cells %ill have different regions of A pacaged as
heterochromatin and euchromatin depending on their function
8/19/2019 Cells Revision - IBBIONINJA
6/24
ifferential
8/19/2019 Cells Revision - IBBIONINJA
7/24
. #lood cells: 7one marro% transplants for cancer patients %ho are immuno-
compromised as a result of chemotherapy
2.2 Prokaryotic Cells
2.2.1 Dra$ and lael a diagram of the ultrastructure of &scherichia coli &. coli- as ane'ample of a pro!aryote
Representation
$% &%
2.2.2
n notate the
diagram $ith the function of each of the named structures
Cell 'all: A rigid outer layer made of peptidoglycan that maintains shape and protects
the cell from damage or #ursting if internal pressure is high
Cell Membrane: ;emi-permea#le #arrier that controls the entry and eit of su#stances
Cytoplasm: &luid component %hich contains the en0ymes needed for all meta#olicreactions
Nucleoid: *egion of the cytoplasm %hich contains the genophore (the proaryotic
A)
!lasmid: Additional A molecule that can eist and replicate independently of the
genophore - it can #e transmitted #et%een #acterial species
Ribosome: Complees of *A and protein that are responsi#le for polypeptide
synthesis (proaryotic ri#osomes are smaller than euaryotes - /6;)
Slime Capsule: A thic polysaccharide layer used for protection against dessication
(drying out) and phagocytosis
(la)ella *sin)ular la)ellum+: 'ong slender pro$ection containing a motor protein
%hich spins the flagella lie a propellor ena#ling movement!ili *sin)ular pilus+: ,air-lie etensions found on #acteria %hich can serve one of t%o
roles
,ttachment pili: ;horter in length they allo% #acteria to adhere to one another
or to availa#le surfaces
Sex pili: 'onger in length they allo% for the echange of genetic material
(plasmids) via a process called #acterial con$ugation
8/19/2019 Cells Revision - IBBIONINJA
8/24
2.2.3 "dentify structures from 2.2.1 in electron micrographs of &. coli
lectron !icrograph of &scherichia coli
2.2.4 State that acterial cells divide y inary fission
7inary fission is a form of aseual reproduction and cell division used #y proaryotic
organisms
?t is not the same as mitosis there is no condensation of genetic material and no
spindle formation
?n the process of #inary fission:
The circular A is copied in response to a replication signal The t%o A loops attach to the mem#rane
The mem#rane elongates and pinches off (cytoinesis) forming t%o separate
cells
The +rocess of 7inary &ission
8/19/2019 Cells Revision - IBBIONINJA
9/24
2.3 Eukaryotic Cells2.3.1 Dra$ and lael a diagram of the ultrastructure of a liver cell as an e'ample of an
animal cell
Representation $%
B
8/19/2019 Cells Revision - IBBIONINJA
10/24
2.3.2 nnotate the diagram from 2.3.1 $ith the functions of each named structure
Cell Membrane: ;emi-permea#le #arrier that controls the entry and eit of su#stances
Cytosol: The fluid portion of the cytoplasm (does not include the organelles or other
insolu#le materials)Nucleus: Contains hereditary material (A) and thus controls cell activities (via
transcription) and mitosis (via A replication)
Nucleolus: ;ite of the production and assem#ly of ri#osome components
Ribosome: Complees of *A and protein that are responsi#le for polypeptide
synthesis (euaryotic ri#osomes are larger than proaryotes - 6;)
Mitochondria: ;ite of aero#ic respiration %hich produces large =uantities of chemical
energy (AT+) from organic compounds
-ol)i ,pparatus: An assem#ly of vesicles and folded mem#ranes involved in the
sorting storing and modification of secretory products
.ysosome: ;ite of hydrolysis digestion #reado%n of macromolecules!eroxisome: Catalyses #read%on of toic su#stances lie hydrogen peroide and
other meta#olites
Centrioles: !icrotu#ule-organising centres involved in cell division (mitosis meiosis
and cytoinesis)
Endoplasmic Reticulum: A system of mem#ranes involved in the transport of
materials #et%een organelles
8/19/2019 Cells Revision - IBBIONINJA
11/24
Rou)h ER: ;tudded %ith ri#osomes and involved in the synthesis and transport
of proteins destined for secretion
Smooth ER: ?nvolved in the synthesis and transport of lipids and steroids as
%ell as meta#olism of car#ohydrates
2.3.3 "dentify the structures in 2.2.1 in electron micrographs of a liver cell lectron !icrograph of a 'iver Cell
2.3.4 Compare pro!aryote and eu!aryote cells
Similarities: 7oth have a cell mem#rane
7oth contain ri#osomes
7oth have A and cytoplasm
8/19/2019 Cells Revision - IBBIONINJA
12/24
%ierences:
2.3.# State three differences et$een plant and animal cells
'a#elled iagram of a
8/19/2019 Cells Revision - IBBIONINJA
13/24
2.3.% Outline t$o roles of e'tracellular components!lants
The cell %all in plants is made from cellulose secreted from the cell %hich serves the
follo%ing functions:
+rovides support and mechanical strength for the cell (maintains cell shape)
+revents ecessive %ater uptae #y maintaining a sta#le turgid state
;erves as a #arrier against infection #y pathogens
,nimals
The etracellular matri (C!) is made from glycoproteins secreted from the cell %hich
serve the follo%ing functions:
+rovides support and anchorage for cells
;egregates tissues from one another
*egulates intercellular communication #y se=uestering gro%th factors
2.4 Membranes2.4.1 Dra$ and lael a diagram to sho$ the structure of memranes
8/19/2019 Cells Revision - IBBIONINJA
14/24
2.4.2 &'plain ho$ the hydrophilic and hydrophoic properties of phospholipids help to
maintain the structure of cell memranes
Structure o !hospholipids
Consist of a polar head (hydrophilic) made from glycerol and phosphate
Consist of t%o non-polar fatty acid tails (hydropho#ic)
,rran)ement in Membrane
+hospholipids spontaneously arrange in a #ilayer
,ydropho#ic tail regions face in%ards and are shielded from the surrounding
polar fluid %hile the t%o hydrophilic head regions associate %ith the cytosolic and
etracellular environments respectively
Structural !roperties o !hospholipid #ilayer
+hospholipids are held together in a #ilayer #y hydropho#ic interactions (%ea
associations) ,ydrophilic hydropho#ic layers restrict entry and eit of su#stances
+hospholipids allo% for mem#rane fluidity flei#ility (important for functionality)
+hospholipids %ith short or unsaturated fatty acids are more fluid
+hospholipids can move hori0ontally or occasionally laterally to increase fluidity
&luidity allo%s for the #reaing remaing of mem#ranes (eocytosis
endocytosis)
2.4.3 /ist the functions of memrane proteins
8/19/2019 Cells Revision - IBBIONINJA
15/24
T
ransport: +rotein channels (facilitated) and protein pumps (active)
R
eceptors: +eptide-#ased hormones (insulin glucagon etc.)
A
nchora)e: Cytoseleton attachments and etracellular matri
C
ell reco)nition: !,C proteins and antigens
I
ntercellular /oinin)s: Tight $unctions and plasmodesmata
Enzymatic activity: !eta#olic path%ays (e.g. electron transport chain)
2.4.4 Define diffusion and osmosis
%iusion:
The net movement of particles from a region of high concentration to a region of lo%
concentration (along the gradient) until e=uili#rium
0smosis:
The net movement of %ater molecules across a semi-permea#le mem#rane from a
region of lo$ solute concentration to a region of high solute concentration untile=uili#rium is reached
8smosis
8/19/2019 Cells Revision - IBBIONINJA
16/24
2.4.# &'plain passive transport across memranes in terms of simple diffusion and
facilitated diffusion
The plasma mem#rane is semi-permea#le and selective in %hat can cross
;u#stances that move along the concentration gradient (high to lo%) undergo
passive transport and do not re=uire the ependiture of energy (AT+)
Simple diusion:
;mall non-polar (lipophilic) molecules can freely diffuse across the mem#rane
(acilitated diusion:
'arger polar su#stances (ions macromolecules) cannot freely diffuse andre=uire the assistance of transport proteins (carrier proteins and channel proteins) to
facilitate their movement (facilitated diffusion)
2.4.% &'plain the role of protein pumps and 0 in active transport across memranes
Active transport is the passage of materials against a concentration gradient
(from low to high)
This process requires the use of protein pumps which use the energy from ATP
to translocate the molecules against the gradient
The hydrolysis of ATP causes a conformational change in the protein pump
resulting in the forced movement of the substance
Protein pumps are specific for a given molecule, allowing for movement to be
regulated (e.g. to maintain chemical or electrical gradients)
An example of an active transport mechanism is the Na+ /K
+ pump which is
involved in the generation of nerve impulses
8/19/2019 Cells Revision - IBBIONINJA
17/24
Types of Membrane Transport
2.4.7 Explain how vesicles are used to transport materials within a cell between the
endoplasmic reticulum, Golgi apparatus and plasma membrane
Polypeptides destined for secretion contain an initial target sequence (a signal
recognition peptide) which directs the ribosome to the endoplasmic reticulum
The polypeptide continues to be synthesised by the ribosome into the lumen of
the ER, where the signal sequence is removed from the nascent chain
The polypeptide within the rough ER is transferred to the golgi apparatus via a
vesicle, which forms from the budding of the membrane
The polypeptide moves via vesicles from the cis face of the golgi to the trans face
and may be modified along the way (e.g. glycosylated, truncated, etc.)
The polypeptide is finally transferred via a vesicle to the plasma membrane,
whereby it is either immediately released (constitutive secretion) or stored for a delayed
8/19/2019 Cells Revision - IBBIONINJA
18/24
release in response to some cellular signal (regulatory secretion = for a more
concentrated and more sustained effect)
Overview of Vesicular Transport
2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and
reform during endocytosis and exocytosis
The membrane is principally held together by the relatively weak hydrophobic
associations between phospholipidsThis association allows for membrane fluidity and flexibility, as the phospholipids (and to
a lesser extent the proteins) can move about to some extent
This allows for the breaking and remaking of membranes, allowing larger substances
access into and out of the cell (this is an active process)
Endocytosis
The process by which large substances (or bulk amounts of smaller substances)
enter the cell without travelling across the plasma membrane
An invagination of the membrane forms a flask-like depression which envelopes
the material; the invagination is then sealed off forming a vesicle
8/19/2019 Cells Revision - IBBIONINJA
19/24
There are two main types of endocytosis:
1. Phagocytosis
The process by which solid substances (e.g. food particles, foreign pathogens)
are ingested (usually to be transported to the lysosome for break down)
2. Pinocytosis
The process by which liquids / solutions (e.g. dissolved substances) are ingested
by the cell (allows quick entry for large amounts of substance)
Exocytosis
The process by which large substances exit the cell without travelling across the
plasma membrane
Vesicles (usually derived from the golgi) fuse with the plasma membrane
expelling their contents into the extracellular environment
The Process of Exocytosis
8/19/2019 Cells Revision - IBBIONINJA
20/24
2.5 Cell Diision2.#.1 Outline the stages in the cell cycle, including interphase 1, S, 2 -, mitosis and
cyto!inesis
The cell cycle is an ordered set of events that culminates in cell gro%th anddivision into t%o daughter cells
?t can roughly #e divided into t%o main stages:
1nterphase
The stage in the development of the cell #et%een t%o successive ! phases
This phase of the cell cycle is a continuum of 3 distinct stages (< 1 ;
8/19/2019 Cells Revision - IBBIONINJA
21/24
2.#.2 State that tumours cancers- are the result of uncontrolled cell division and that
these can occur in any organ or tissue
The cell cycle is controlled #y a comple chemical control system that responds
to signals #oth inside and outside of the cell
Tumor suppressor genes produce proteins %hich inhi#it cell division %hile proto-
oncogenes produce proteins that promote gro%th and division
!utations to these genes result in uncontrolled cell division resulting in the
formation of a tumour
Tumours can gro% in si0e %hich causes damage local tissue@ they may also
spread to other parts of the #ody (malignant tumours)
iseases caused #y the gro%th of tumours are collectively no%n as cancers
Cancer in Tasmanian evils
2.#.3 State that interphase is an active period in the life of a cell $hen many metaolic
reactions occur, including protein synthesis, D replication and an increase in the
numer of mitochondria and chloroplasts
?nterphase is an active period in the life of a cell - many events need to occur #efore a
cell can successfully undergo division:
Protein synthesis: The cell needs to synthesise ey proteins and en0ymes to
ena#le it to gro% copy its contents and then divide
AT! production: The cell %ill need to generate sufficient =uantities of AT+ in
order to successfully divide
Increase number o or)anelles: The cell needs to ensure #oth daughter cells
%ill have the necessary num#ers of organelles needed to survive
DN, replication: The genetic material must #e faithfully duplicated #efore
division (this occurs during the ; phase)
8/19/2019 Cells Revision - IBBIONINJA
22/24
As none of these processes can occur during the ! phase interphase contains gro%th
checpoints to ensure division is via#le
G1
: A checpoint stage #efore A replication during %hich the cell gro%s
duplicates organelles synthesises proteins and produces AT+
S: The stage during %hich A is replicated
G2
: A checpoint stage #efore division during %hich the copied A is checed
for fidelity (mutations) and final meta#olic reactions occur
2.#.4 Descrie the events that occur in the four phases of mitosis
!rophase
A supercoils causing chromosomes to condense and #ecome visi#le under a
light microscope As A %as replicated during interphase the chromosomes are each comprised
of t%o genetically identical sister chromatids $oined at a centromere
The centrosomes move to opposite poles of the cell and spindle fi#res #egin to
form #et%een them (in animals each centrosome contains 2 centrioles)
The nuclear mem#rane is #roen do%n and disappears
Metaphase
;pindle fi#res from the t%o centrosomes attach to the centromere of each
chromosome
Contraction of the microtu#ule spindle fi#res cause the chromosomes to line up
separately along the centre of the cell (e=uatorial plane)
,naphase
Continued contraction of the spindle fi#res cause the t%o sister chromatids to
separate and move to the opposite poles of the cell
8nce the t%o chromatids in a single chromosome separate each constitutes a
chromosome in its o%n right
8/19/2019 Cells Revision - IBBIONINJA
23/24
Telophase
8nce the t%o sets of identical chromosomes arrive at the poles the spindle fi#res
dissolve and a ne% nuclear mem#rane reforms around each set of chromosomes
The chromosomes decondense and are no longer visi#le under a light
microscope The division of the cell into t%o daughter cells (cyto!inesis) occurs concurrently
%ith telophase
2.#.# &'plain ho$ mitosis produces t$o genetically identical nuclei
uring interphase (the ; phase) the A %as replicated to produce t%o copies of
genetic material
These t%o identical A molecules are identified as sister chromatids and are
held together #y a single centromere
uring the events of mitosis (as descri#ed in 2.4.) the sister chromatids are
separated and dra%n to opposite poles of the cell
Dhen the cell divides (cytoinesis) the t%o resulting nuclei %ill each contain one
of each chromatid pair and thus #e genetically identical
2.#.% State that gro$th, emryonic development, tissue repair and ase'ualreproduction involve mitosis
Growth: !ulticellular organisms increase their si0e #y increasing their num#er of cells
through mitosis
A
sexual reproduction: Certain euaryotic organisms may reproduce aseually #y
mitosis (e.g. vegetative reproduction)
T
issue Repair: amaged tissue can recover #y replacing dead or damaged cells
8/19/2019 Cells Revision - IBBIONINJA
24/24
Embryonic development: A fertilised egg (0ygote) %ill undergo mitosis and
differentiation in order to develop into an em#ryo