LECTURE 1 - TOPIC 1 (INTRO TO CELL BIOLOGY)
Slide 2-What is a cell
-all living things are made of cells
-regulates internal environment
-reproduces to produce other cells
-responds to external environment surrounding it
-cytoplasm enclosed by lipid and protein membrane
-contains genetic information
-most have metabolic processes
1. all organisms consist of one or more cells
2. the cell is the basic unit of structure fro all organisms (theodore schwann 1839 & Matthias Schleiden
3. All cells arise only from pre existing cells (i.e the cell is the basic unit of reproduction. (rudolf Virchow
Slide 3-Can one speak of THE cell?
They vary, and are very diverse
Slide 4-Can one speak of THE cell?
Enormous diversity, shapes can be very diverse, and also interns of size. Most cells are very small (smalls
2nm) they can be as big as 13cm in diameter (eggs are an example)
Nerve cells that extend from the spinal cord to the foot of a giraffe are approximately a meter in size
cells vary also in function; some cells are really good at everything, but in multicellular organisms you can
get cells that highly specialized in terms of what they do.
although cells are immensely diverse, they have very important similarities. looking at the proteins, you'll find
similar amino acids, DNA aswell for genetic information, looking at metabolism they use ATP for cellular
Slide 5-Size of Cells
avg prokaryotic cell 1-5 microns
avg eukaryotic 10-30 microns
nucleus diameter-0.006mm (6 microns)
mitochondrion length-3x10^-6 (3 microns)
giraffe axon length-1x10^6
Microfilament diameter-0.007microns (7nm)
Slide 6- Why cells are small
relates to surface area to volume ration if the surface are to volume aren't well matched the cell either
starves of nutrients.Volume of the cell tells you how much it needs in terms of nutrients moving in, and wage
moving out. SUrface area is the area in which that exchange can take place.
(you need enough SA to match cells volume)
surface area is falling as cell becomes larger (6:1 --> 3:1) think of an entire class trying to leave marion
through only 4 small doors
How do we get large organisms? We make the cells smaller. the blue and the green organism are both the
same size, but the green one is made up of many small units, as to not jeopardize the SA:V, this allows
exchange area to keep up with the cells nutrients and waste requirements.
Limitation #2 is diffusion. It is good as long assistances are small.
cells cannot afford to be large because the rate of diffusion cannot keep up. diffusion is relatively slow, this is
what keeps cells small. 78d to move O2 molecule across a cell that is 1m.
this provides a major constraint on cell size.(diffusion is slow over long distances)
limitation #3, are the cell size increases, the number of molecules (substrates) that need to be synthesized
for reactions to occur increases. At a certain size, the synthetic machinery just simply cannot produce
enough molecules, to produce a great enough concentration for reactions to proceed.
Slide 7-Prokaryotic and Eukaryotic cells differ in their solutions to size problem
-lack a true nucleus (very simple cells)
-a cell membrane bounded by cell wall
-inside is (semi liquid fluid) cytoplasm
-Cytoplasm includes ribosomes for protein synthesis
-Genetic material of the cell is in the form of a single circular chromosome without structural proteins.
-All folded on itself and forms nucleiod (NO NUCLEUS)
Slide 8- (slide 7 cont'd)
Small simple cells is their solution to the constraints on cell size; They just stay small (despite the fact that
they are small, they are incredibly diverse. fall into group arches and eukarya)
Archea = extreme-o-philes