cmb lect 1 2011 colour 2 slides.pdf

8/14/2019 CMB Lect 1 2011 colour 2 slides.pdf

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LECTURE 1

CELLS AND ORGANELLES

BIOSCI 101: Cellular and Molecular Biology

Cell Biology• Cell Biology as a science began with thedevelopment of microscopy

-1674 - Anton van Leeuwenhoek improved the art ofpolishing lenses1838 - Schleiden and Schwann proposed the CellDoctrine1858 - Rudolph Virchow established the notion thatevery cell derives from a pre-existing cell1864 - Pasteur dis roved the theor of s ontaneous


generation

• By the beginning of the 20th century it wasfirmly established that all living things arecomposed of one or more units called cells



The diversity of cell size• Units of measurement used in microscopy:

1 cm = 10 -2 m1 mm = 10 -3 m1 μ m = 10 -6 m so 1mm = 10 3 μ m1 nm = 10 -9 m1 Å = 10 -10 m so 1 nm = 10Å

- ran e in cell size and sha e is enormous


- this represents evolutionary adaptation to

different environments or to differentspecialised functions within a multicellularorganism

The diversity


Campbell 6.2



Microscopy• resolving power is a measure of the capacity

to distin uish ob ects from one another afunction of the wavelength of energy beingused to illuminate the specimen)

• magnification is enlargement of an image


Microscopy (contd)• i) Light microscopy

-microscope is ~ 0.25 μ m (~500x better thanthe naked eye)- useful for the observation of whole cells andlarger subcellular structures (nucleus,chromosomes)-


using techniques such as confocal microscopy



Light microscope

BIOSCI 101: Cellular and Molecular BiologyCampbell Appendix D

Brightfield(stained specimen)(unstained specimen)

Brightfield


FluorescenceConfocal

Campbell 6.3



Prokaryotic cells (Bacteria and

Archaea)•

organised nucleus• little or no internal structure

- no organelles• large number of ribosomes• cell wall composed of


pep og ycan• flagella if motile, also may

have pili for attachment tosurfaces or to other bacteria

A prokaryotic cell

BIOSCI 101: Cellular and Molecular BiologyCampbell 6.5



Many prokaryotes are motile

Flagellum

HookMotor

Filament

Cell wall

BIOSCI 101: Cellular and Molecular Biology(Campbell 27.6)

RodPeptidoglycan

layer Plasma

membrane

Eukaryotic cells (Protists, Fungae,Plants and Animals)

• ’DNA enclosed by a double layer of membrane

• differences between plant and animal cells:-

PLANT CELLSPLANT CELLS ANIMAL CELLSANIMAL CELLS


cellulose cell wall no cell wallvacuoles unusual or smallchloroplasts no chloroplasts



Overview of an animal cell


Overview of a plant cell




Cell Organelles•

- bounded by nuclear envelope which consists oftwo membranes.- membranes fuse together periodically to formpores through which material can pass into andout of the nucleus.


- con a ns nuc ear con en s ermenucleoplasm)

The nucleus and its envelope




Cell Organelles (contd)• i The nucleus contd

- Chromatin - DNA / histone protein complexwhen it is amorphous and not condensed intovisible fibres (non-dividing interphase cells)

- Chromosomes - condensed chromatin fibresvisible during cell division


- Nucleolus - dense body usually only visiblewithin nucleus between cell divisions andconcerned with the synthesis of ribosomal RNA

Cell Organelles (contd)• ii) Endoplasmic reticulum and ribosomes

- interconnecting network of membranes in thecytoplasm continuous with the outer membrane ofthe nuclear envelope- Rough ER - flattened sheets of ER membranestudded with ribosomes making proteins destinedfor secretion (non-secretory proteins are


cytoplasm)- Smooth ER - generally more tubular, lacksattached ribosomes, major function in synthesisand transport of lipids, Ca 2+ storage, detoxificationof drugs and poisons



Ribosomes andthe endoplasmic

reticulum


Campbell 6.11

Cell Organelles (contd)• iii) The Golgi apparatus

-- involved in modifying, sorting and packagingmacromolecules for secretion from the cell or fordelivery to other organelles via membranevesicles

• iv) Lysosomes-


enzymes safely packaged away from the rest ofthe cell.- concerned with the breakdown of materialsbrought into the cell and recycling of damagedorganelles



The Golgi apparatus


Lysosomes




Relationships among organelles ofthe endomembrane system


Cell Organelles• vi) Mitochondria- power plant of eukaryotic cells where energyis obtained from combinin ox en with foodmolecules to make ATP- large cylindrical shaped bodies about 1 um indiameter.- bounded by a double membrane, inner partof which is thrown into folds (cristae) whichare the working surfaces for mitochondrial


.



Cell Organelles

• vi) Mitochondria (contd)- associated with the membranes are the

involved in the generation of ATP via glycolysisand the Krebs cycle.- also contain their own ribosomes and DNAthus they are capable of synthesising some oftheir own components (coding system differs


.

The mitochondrion




Cell Organelles (contd)•

- leucoplasts (storage), chromoplasts (pigments)or chloroplasts (photosynthesis), found only inplants and algae- chloroplasts are bounded by an outer and aninner membrane and also have a third internal


contains the photosynthetic apparatus.- chloroplasts also contain DNA and ribosomes.

The chloroplast




Cell Organelles (contd)•

- interconnecting protein structures within thecytoplasm- maintains the shape of the cell and provides abasis for its movements


- three different types of cytoskeletal filaments:microtubules, microfilaments and intermediatefilaments

Cytoskeletal filaments

BIOSCI 101: Cellular and Molecular BiologyCampbell Table 6.1



Cytoskeletal filaments

BIOSCI 101: Cellular and Molecular BiologyCampbell Table 6.1

Motor molecules and the cytoskeleton




Cell Organelles (contd)

•- permanent structures used for locomotion- many short ones = cilia, fewer long ones =flagellae- 9 pairs of microtubules surrounding two centraltubules, all enclosed by an extension of the


p asma mem rane- movement thought to be caused by each outerpair of microtubules moving with respect to itsnearest neighbour

Cilia and flagellae




Extension reading:

http://www.nature.com/nature/journal/v465/n7297/pdf/465422a.pdf


cmb lect 1 2011 colour 2 slides.pdf

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