Cell Structures - Microscopy... Cytology - Prokaryotes vs. Eukaryotes - Cell structures/ Organelles Nucleus Endoplasmic Reticulum Mitochondria - The Endosymbiont theory

1. BIOLOGY AS LEVEL
REVISION 01

2. 2. Cell Structures

3. Cells
 ALL organisms are made up of cells
 Simplest collection of LIVING matter
 Cell structure correlate to their functions
 All cells are related to earlier cells that they descend
from

4. MICROSCOPY

5. Microscopy
 Microscope is an instrument that magnifies objects
too small to be seen, producing an image that
appears larger.
 Photographs/ pictures of cells derived from the
microscope - Micrographs

6. Magnification
 A measure how much larger a microscope can
cause an object to appear
 The Ratio of the object to its actual size
(Magnification = measured length[of image]/ actual
length of object)

9. Resolution
 A measure of clarity – the smallest distance by
which two points can be distinguished in an image.
 Limited by the physical properties of light

10. Light Microscope
 Commonly used
 Visible light passes through
the specimen
 Bent through the lens system
– producing magnified image
 X1000 magnification
 Uses blue light – 400 nm
 Lowest Resolution = 200nm

11. The Electromagnetic
Spectrum
 The resolution depends on the wavelength of the
light/ radiation being used on the specimen

13. Light Colors
 Light with the largest wavelength is red = 700 nm
 Light with smallest wavelength is blue = 400 nm
 With the magnification, resolution is actually half the
wavelength
 Light microscope uses blue – 200 nm resolution

14. Electron microscope
 Uses electron – has a
shorter wavelength
 X-ray is hard to control –
electron can be controlled
using magnets
 Electron can only function
in vacuum – oxygen
molecules may cause the
electron to be knocked
around
 False-coloring by computer

15. SEM
 Scanning Electron
microscope
 Electron bounce back
and forth across
specimen’s surface
 Creating a detailed 3D
image
 Resolution smaller that
TEM

16. TEM
 Transmission
Electron Microscope
 Electron passes
through the surface
 Used to inspect the
inner structures of cell
 Resolution can go
down to 0.5 nm

17. Light Vs. Electron
Similarities
 Both uses
Lens
Differences
 One uses visible light, another uses electron molecule
(electron vs. photon)
 Resolution, one is 200, the other is 0.5
 With SEM – 3D image is possible
 Electron is more expensive
 One focuses light with lens, the other focuses light by
electromagnetic control
 One uses electron gun, the other uses low voltage
bulb
 On magnifies up to 1500, the other up to 500000
 One uses air as medium, another uses vacumm

18. Cell Fractionation
 Takes cell apart and separates organelles
 Cells are centrifuged where the heavier components
will sink to the bottom
 Ultracentrifuges – fractionates them into
components

19. Cell Sizes/ Scale
 Red Blood Cell: 7 micrometer (7000 nm)
 Egg cell: 100 micrometer (100000 nm)
 A virus: 20 – 400 nanometer
 Prokaryote: 0.1 – 5 micrometer (100 – 5000 nm)
 Nucleus: 6 – 7 micrometer (6000 nm)
 Ribosomes: 25 nanometer
 Cell Membrane: 7 nm
 Microtubules: 25 nm
 Microfilaments: 6 nm

20. Extra read:
http://peer.tamu.edu/curriculum_modules/Cell_Biology/module_1/whatweknow.
htm

21. Kingdom of living things
 Eukaryote
1. Animal
2. Plant
3. Fungi
4. Protists
 Prokaryote
1. Bacteria
2. Archea

22. PROKARYOTE
VS.
EUKARYOTE

23. Prokaryotic
 Prokaryote – a simple organism e.g. Bacteria
 No nucleus
 No membrane-bound organelles
 Has Cell Walls
 Has Circular chromosomes
 Common cell structures: Plasma membrane,
Cytoplasm, DNA, Ribosomes

26. Animal Cells

27. Animal Cell Structure
 Nucleus: Contains chromosomes/ DNA – code for the
synthesis of proteins that control the function of the cell –
hence the nucleus commands the cell
 Cell Surface membrane: Holds the cell content, controls
the ins/outs, structural forms, cell recognition, adhesion,
signaling, transport of substances, endo/exocytosis
 Cytoplasm: the liquid where all the cell metabolic
activities take place
 Mitochondria: Produces energy in the form of ATP
through respiration

28. Animal Cell Structure
 Ribosomes: Receiving mRNA coded for Protein
synthesis
 Lysosome: Engulfs materials and destroy them with
enzymes
 Rough ER: Has ribosomes on it – involved in protein
synthesis – transport network for protein
 Smooth ER: Synthesis of lipid – involved in cell
detoxification
 Golgi bodies: Process the finished proteins

29. Nucleus
 Double nuclear envelope –
encloses/ protect DNA
 Nuclear pore – received
substances for DNA
Replication(extra phosphate),
exits for mRNA
 small molecules pass through
by diffusion, large ones get in
actively
 in micrographs – RNA/protein
complex can be seen
plucking the pore

30. Nucleus
 Nucleoplasm – contains
chromatin granules,
DNA/associated proteins:
during cell division, they
condense to form
chromosomes
 Nucleolus – produces rRNA
part of ribosomes, proteins,
coenzymes, enzymes for
nucleic acid synthesis, RNA
 Outer membrane continuous
with ER – easier transport

31. Endoplasmic Reticulum
 A system of hollow tubes/ sacs – transportation
purpose
nucleus
Rough
Endoplasmic
Reticulum
Smooth
Endoplasmic
Reticulum

32. Rough ER
 Covered with ribosomes
 Interconnected system of
flattened sacs
 Ribosomes on surface
synthesize proteins which are
then transported through the
interconnected system
 RER is abundant in cells which
needed to produce a lot of
proteins for exports e.g.
Digestive enzymes/ growth

33. Smooth ER
 Lacks ribosomes
 A system of interconnected
tubules
 Carbohydrate/ lipids metabolism
 Synthesizes: triglycerides,
phospholipid, cholesterol
 Modification of steroid hormones
 High percentage in cells
involved with metabolism of
lipids/drugs

34. Golgi Body
 Flattened cisternae
 Invaginate/ fuse to form
vesicles
 Internal transports by
vesicles
 Vesicles protect molecules
 In case of enzymes –
protect the cells

35. Cell Membrane
 Fluid mosaic bilayers which surround the cell content
 Control the ins/outs of the cell
 Gives the cell stability during temperature changes
 Endocytosis/ exocytosis
 Important in cell recognition
 Cell signaling
 Cell adhesion

36. Cytoplasm
 Makes up of liquid: Cytosol
 Where the metabolism takes place
 Contains water/ solution
 Most organelles float here
 Osmoregulation

37. Mitochondria
 Double Membrane – isolate
certain reaction – high
concentration of enzymes/
substrates can be maintained
 Outer membrane –
permeable to salt, sugar,
nucleotides
 Inner membranes –
selectively permeable
(control chemical composition
of the matrix – optimizes
enzyme activity)

38. Mitochondria
 Porins on inner membranes – entry of
oxygen/pyrovic acid – exit of ATP/ Carbon dioxide
 Folded inner membrane (cristae) – increases
surface area for enzymes/ coenzymes
 70s ribosomes – protein manufacturing
 Loop of circular DNA – codes for protein
 Enzymes

40. Endosymbiosis theory
 States that mitochondria’s
ancestors were bacterial
ingested by a eukaryote
 The eukaryote kept it as it is
useful for respiration
 Evidences: 70s vs. 80s
ribosomes
 Evidences: Own DNA
 Evidences: Divides by itself

41. Ribosomes
 2 subunits
 Made of rRNA/ Protein
 rRNA – formed in nucleus –
moves out via pores
 Protein part – assembled in
the cytoplasm
 Found as dense clusters
(polysomes)
 On membranes of RER

42. Lysosomes
 Vesicles that contains
hydrolytic enzymes
 Break down old organelles –
recycle the materials
 Break down storage
molecules
 Break down whole cell when
it dies

43. Cytoskeleton
 Microtubules – tubulin proteins : Thickest fo the
three – around 25 nm
 Microfilaments – actin proteins
 Intermediate filaments

44. Microfilament
 Rods of about 7nm in diameter
 Made up of a twisted double chain of actin subunits

45. Microfilaments
 Create tension
 Support the shape of the cell
 3-D Cortex inside plasma membrane
 Bundles of microfilaments indie the microvilli

47. Microtubules

48. Microtubules
 25 nm wide
 Made up of tubulin proteins
 Arranged in dimers (alpha tubulin/ beta tubulin)
 This dimer repeat in vertical format – forming a
protofilament
 13 protofilaments arrange around a hollow core
 MICROTUBULES FORM

49. Microtubules
 Shapes the cell
 Guide the movements of cells/ organelles – with
help of motor proteins
 Make up spindles that separate chromosomes
during cell division

50. Centrosome
 Contains 2 centrioles
 The location for MTOC (Microtubules organizing
center)
 MAY have a role in regulating the cell division

51. Centrioles
 Microtubules form triplets (1
complete microtubule, 2 partial
microtubules)
 These triplets then arrange into a
cylinder
 200 nm in diameter, 500 nm long
 Two of these line up perpendicular
to form centriole
 Not sure of its function yet
 Some believe it might be MTOCs
for spindles during cell division

53. Cilia/ Flagella
 Long structures projecting out of a cell membrane
 A core of microtubules sheathed by the plasma
 Flagellum – longer and for movement of cell
 Cilia – shorter – usually to beat up things

54. Plant Cells

56. Cell Wall
 Cellulose fiber embedded in
other polysaccharides/
proteins
 Pectin and cellulose fiber
(strong)
 Permeable
 Space between cells above
the wall: middle lamella
 Things like wood may have
secondary cell wall

57. Cell Wall
 The osmotic pressure vs. the pressure from cell wall
gives the plant its structure
 Structure of Cellulose – resistant to degradation and
enzymes – only cellulase – Protects the cell
 Prevent bursting

58. Cell Wall
 May have multiple layers
1. Primary Cell Wall – thin and flexible
2. Middle lamella – a thin layer between primary walls
and adjacent cells
3. Secondary cell wall (only found in certain cells) :
between plasma membrane and primary cell wall –
on the inside where it grows

60. Cell Wall
 Tunnels between cells: Plasmodesmata
 Protoplast: A plant, bacterial or fungal cell with its
cell wall removed

61. Vacuoles
 Enclosed membrane
compartments – filled with water
content/ enzymes/ proteins etc.
 Storage for waste, harmful
materials
 Storage for water
 Hydrostatic pressure controlled
 Work with cell wall to maintain
turgidity
 The membrane around it:
Tonoplast

62. Chloroplasts
 Plant organelles specialized in conducting
photosynthesis
 Larger than mitochondria
 Double membrane
 Has its own DNA
 Endosymbiosis theory applied to it as well

64. Chloroplast
 Inner/ Outer membrane
 Stroma: The liquid inside the inner membrane
 Grana: Made up of stacks of thylakoid
 Thylakoid: Has chlorophyll on the surface

65. Virus
 Size: 20 – 750 nm
 We are not sure if virus
is considered an
organism
 As it is unable to fully
function without a host
 Nevertheless, virus is a
fascinating component
to Biology worthy of
studies

66. Virus Structure
 Consists of an RNA molecule
protected by a protective
protein coat called capsid
 Capsid made up of proteins
called capsomere
 On the outside a protein
envelope gives it another
layer of protection
 Glycoproteins/lipids stuck out
from the envelope

67. Plant Cell Vs. Animal Cell
Common
 Nucleus
 ERs/ Golgi body
 Plasma membranes
 Phospholipid bilayer
 Mitochondria
 Gap between cells (gap junction/
Plasmodesmata)
 Both have cytoskeleton
 Peroxisomes
Differences
 Cell Wall
 Cell membrane: Glycolipid/
Glycoprotein
 Centrioles
 Central vacuoles
 Chloroplasts