Cells Flashcards
Centrioles?
- centrosome - 2 centrioles (90 degrees to e/o)
- form network of fine fibres in cytoplasm aka: cytoskeleton
functions: - support cell’s shape
- organises & moves organelles
- cell division - pair separate to opp ends of cell & form the spindle
Differences between Prokaryotic & Eukaryotic cells (important ones)?
- Pro: no nucleus (only area in cytoplasm where DNA is found) & no membrane bounded organelles Euk: nucleus in which DNA contained) & membrane bounded organelles
- Pro: DNA circular, not associated w proteins (& extra plasmids) Euk: DNA linear, associated w histone proteins (& no plasmids)
- Pro: smaller 70s ribosomes Euk: larger 80s ribosomes
- Pro: cell walls made of murein (a glycoprotein) Euk: cellulose in plants & chitin in fungi
- Both: cytoplasm & cell membrane
- Pro: outer layer aka capsule for protection Euk: no capsule
Endomembrane system/organelles working together?
- mRNA copy of instructions (gene) for protein is made in nucleus
- mRNA leaves nucleus thru a nuclear pore
- mRNA attaches to a ribosome (attached to ER) - ribosome reads instructions to assemble protein
- protein molecules r pinched off in vesicles & travel towards Golgi apparatus
- vesicle fuses w Golgi apparatus
- apparatus processes & packages protein molecules ready for release
- packaged protein molecules r pinched off in vesicles from apparatus & move towards cell surface membrane
- vesicle fuses w cell surface membrane
- cell surface membrane opens to release protein molecules outside
Tissue definition?
a group of cells that work together to perform a specific function
Organ definition?
groups of different tissues that work together to perform a specific function
organ system definition?
groups of different organs that work together to perform a specific function
What structures do viruses always have?
- genetic material
- capsid
- attachment protein
(extras: reverse transcriptase/lipid envelope/matrix)
Importance of cell division?
- growth (increasing size/no. cells) (mitosis)
- repair/replacement (mitosis)
- reproduction (producing gametes) (meiosis)
Cell cycle 2) Mitosis?
nuclear division that produces 2 daughter nuclei that r genetically identical to parent nuclei as well as e/o
- diploid cells created
Cell cycle 1) Interphase?
- longest stage in cycle
- G1 -> S -> G2
- when organelles double & cell grows (G1)
- DNA replicates (S)
- error checking duplicated chromosomes - if mutation detected - cell destroyed
Cell cycle 3? cytokinesis?
division of cytoplasm to create new cells
Features of mitosis?
- 1 round of division
- genetically identical cells r made
- diploid cells are made (hv 2 copies of each chromosome)
- purpose: growth & repair e.g. clonal expansion (division) of B cells
Prophase?
- chromosomes condense (shorten & thicken) & become visible
(interphase - can’t see chromosomes) - centrioles separate & move to opp poles of cell
- spindle fibres start to develop
- nucleolus disappears
- nuclear envelope disintegrates
Metaphase?
- chromosomes align along equator of cell
- chromosomes attach to spindle fibres by their centromeres
Anaphase?
- centromeres divide into 2
- spindle fibres shorten & pull chromatids to opp poles of cell
- ATP needed
Mitotic index?
% of cells undergoing mitosis
mitotic index = no. cells in mitosis/total no. cells x 100
- for pics - count no. cells where can see chromosomes - as it’s in mitosis
Telophase?
(chromatids referred to as chromosomes)
- chromosomes become longer & thinner again (can’t see)
- spindle disintegrates
- nuclear envelope reforms
- nucleolus reappears
Mitosis is a gene controlled process…
- controlled by 2 types of genes:
1. oncogenes
2. tumour suppressor genes - activation of oncogenes - lead to cancer
- inactivation of tumour suppressor genes - lead to cancer
mutation of oncogenes leading to cancer?
- proto oncogenes - usually only switched on when cell is going to divide
- but - if mutate to become oncogene - becomes permanently switched on so - uncontrolled cell division
mutation of tumour suppressor genes leading to cancer?
- slow down cell division - gives the cell time to repair mistakes - helps to maintain normal rates of cell division so…
- mutation on a TS gene removes this break, leading to uncontrolled cell division
How does uncontrolled cell division lead to formation of tumours & cancers?
- most mutated cells die but - those that don’t r capable of dividing - form group of abnormal cells called a tumour
- Constantly grows in size
- Can grow in any organ
Treating cancer?
- killing rapidly dividing cells by blocking a part of cell cycle e.g.
- preventing DNA replication or…
- inhibiting metaphase - by interfering w spindle fibre formation
- prob: can interfere w cell cycle of normal cells that normally divide rapidly
Difference in mitosis in plant cells?
- cell plate forms between nuclei
- new cell wall created - diving cell into 2 daughter cells
Cell division in prokaryotic cells - binary fission?
- cell replicates circular DNA and plasmids
- cytoplasmic membrane elongates - separating DNA molecules
- cross wall forms & membrane invaginates (folds)
- cross wall forms completely - division of cytoplasm to produce 2 daughter cells
Log 10 converts true value into…
how many times 10 has been multiplied by itself to give that value
Why use log?
- if large range of data - need to convert to log so - can read data points off graph accurately
