s250 lecture 1

8/6/2019 s250 Lecture 1

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S250 CourseMAMMALIAN CELL

ULTRASTRUCTURELECTURE 1

8/6/2019 s250 Lecture 1


THE CELL• 1. All living things are composed of cells

and cell products.• 2. The cell is the basic unit of structure and

function of all living things.• 3. All cells come from the division of pre-

existing cells.• 4. An organism as a whole can be understood

through the collective activities and

interactions of its cells.Virchow 1855

8/6/2019 s250 Lecture 1


THE CELL

• Nucleus – control centre of cell

• Nucleoplasm – material within nucleus

• Cytoplasm – contains cytosol/organelles

• Plasma Memebrane - outer boundary of cell

8/6/2019 s250 Lecture 1


CELL ULTRASTRUCTUREORGANELLES

• 1 Nucleus/Nucleolus• 2 Endoplasmic Reticulum +/- Ribosomes• 3 Golgi Apparatus

• 4 Mitochondria• 5 Lysosomes – (Endo/exocytosis)

• 6 Peroxisomes• 7 Filaments

8/6/2019 s250 Lecture 1


8/6/2019 s250 Lecture 1


NUCLEUS

• Structure: Largest organelle. Round or oval body locatednear cell centre. Surrounded by nuclear envelope composedof two membranes. Envelope contains nuclear poresthrough which messenger molecules pass to cytoplasm. No

membrane-bound organelles present in nucleus, whichcontains coiled strands of DNA known as chromatin .• Function: Stores and transmits genetic information in the

form of DNA . Genetic information passes from nucleus to

cytoplasm, where amino acids are assembled into proteins.

8/6/2019 s250 Lecture 1


NUCLEOLUS• Structure: Densely stained filamentous structure with

nucleus. Consists of proteins associated with DNA inregions where information concerning ribosomal proteins

is being expressed.• Function: Forms ribosomal particles that then pass into

cytoplasm, where they function as sites of proteinsynthesis.

8/6/2019 s250 Lecture 1


Endoplasmic Reticulum

8/6/2019 s250 Lecture 1


GRANULAR ENDOPLASMIC RETICULUM• Structure: Extensive work of flattened sheets. Encloses a

space that is continuous throughout the organelle andcontinuous with the space formed by the two nuclear envelopemembranes. Has ribosomal particles attached to its cytosolicsurface.

• Function: Proteins are synthesized on the attached ribosomesultimately distributed to other organelles or secreted from cell.

8/6/2019 s250 Lecture 1


8/6/2019 s250 Lecture 1


CELL ULTRASTRUCTURERIBOSOMES

(A) Bound to ER and (B) Free in cytoplasm• Each ribosome composed of a large number of proteins

and several RNA molecules.• Ribosomes synthesize proteins from amino acids using

genetic information sent by messenger molecules fromDNA in the nucleus.

• Proteins synthesized on the free ribosomes are releasedinto cytosol.

• Proteins are synthesized by ribosomes attached to ER passinto the lumen to the Golgi apparatus.

8/6/2019 s250 Lecture 1


GOLGI APPARATUS

• Structure: Series of cup-shaped,closely opposed, flattened,membranous sacs; associatedwith numerous vesicles.Generally, a single Golgiapparatus is located in central

portion of cell near nucleus.

• Function: Concentrates,modifies and sorts newlysynthesized proteins prior totheir distribution, by way of the

Golgi vesicles, to other organelles or their secretionfrom cell.

8/6/2019 s250 Lecture 1


MITOCHONDRIA• Structure: Rod or oval-shaped body

surrounded by two membranes. Inner membrane folds into matrix of themitochondria, forming cristae.

• Function: Major site of ATP Production.O2 utilisation and CO2 formation.Contains enzymes of Krebs cycle andoxidative phosphorylation.

8/6/2019 s250 Lecture 1


8/6/2019 s250 Lecture 1


CELL ULTRASTRUCTURELysosomes

• Highly specialised intercellular digestive system.• Spherical or oval organelle surrounded by a single

membrane.

• Break down bacteria and debris from dead cells that have been taken into the cell.

• May also break down cell organelles that have beendamaged and are no longer functioning normally.

8/6/2019 s250 Lecture 1


CELL ULTRASTRUCTUREPEROXISOMES

• Oval bodies covered by a single membrane (similar structure to LYSOSOMES by chemically different)

• Consume oxygen (in smaller mounts thatMITOCHONDRIA)

• Destroy certain products formed from oxygen e.g.

hydrogen peroxide – can be toxic to cells.

8/6/2019 s250 Lecture 1


CELL ULTRASTRUCTUREFILAMENTS

• MICROFILAMENTS –major part of cytoskeleton.• INTERMEDIATE FILAMENTS – in cells subject to

mechanical stress.

• MUSCLE THICK FILAMENTS – found only in musclecells.• MICROTUBULES - most rigid of cytoskeletal filaments.

- associated with movements of partcells – cell division (CENTRIOLES)

- extensions on surface of epithelialcells (CILIA)

8/6/2019 s250 Lecture 1


s250 lecture 1

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