Mitosis Flashcards
without O2, ETC…
ceases to operate
- glycolysis must couple with fermentation or anaerobic respiration to make ATP
anaerobic respiration uses an
ETC with sulfur or other organic compound as final electron acceptor instead of O2 (forming HSO4 instead of H2O)
fermentation uses
substrate level phosphorylation to make ATP and
glycolysis and reactions to regenerate NAD+
- two types: alcohol and lactic acid fermentation
- all in cytoplasm
alcohol fermentation
pyruvate converted to ethanol in two steps
1. releases CO2 from pyruvate
1. reduces resulting acetaldehyde to ethanol
- used in brewing, winemaking, baking
Lactic acid fermentation
pyruvate reduced by NADH forming lactate, NO release of CO2
- cheese and yogurt and muscle cells
Anaerobic vs Aerobic
both: use glycolysis to oxidize glucose, NAD is oxidizing agent/accepts electrons from food during glycolysis
- fermentation: final electron acceptor is organic molecule and produces 2 ATP per glucose
- cellular respiration: electron from NADH to carrier molecule in ETC and produces 32 ATP per glucose
Obligate anaerobes
carry out only fermentation anaerobic respiration and cannot survive in presense of O2
Facultative anaerobes
can survive in either (yeast, bacteria)
- pyruvate is fork in metabolic road and leads to two catabolic routes
cell division
continuity of life is based on reproduction of cells
unicellular division
division of 1 cell reproduces entire organism
- fission
cell cycle
the life of a cell form its formation to its own division (cell division is integral part)
most cell division results in
two genetically identical daughter cells
genome
all the DNA in a cell constitutes this
- can be single DNA molecule (prokaryotes) or a number of DNA molecules (eukaryotes)
Chromsomes
DNA molecules packaged into cell
chromatin
complex of DNA and proteins
Somatic cells
two sets of chromosomes, non-reproductive
Gamets
one set of chromosomes (reproductive: sperm and eggs)
before cell division
Cell is replicated and condensed
- each duplicated chromosome has two sister chromatids
two sister chromatids
joined identical copies of the original chromosome
- centromere
- initially, sister chromatid are attached along their length by cohesions (protein complexes)
centromere
where the two chromatid are most closely attached
during cell division, the 2 sister chromatids….
separate and move into two nuclei
- once separated, called chromosomes
eukaryotic cell division consists of…
- mitosis
- cytokinesis
mitosis
the division of the genetic material in the nucleus
cytokinesis
the division of cytoplasm
gametes use meiosis
yield non-identical daughter cells with one set of chromosomes
phases of the mitosis cycle
- mitotic (M) phase: mitosis and cytokinesis
- interphase: cell growth and copying of chromosomes in prep for cell division (about 90% of cell cycle)
interphase phases
G1 phase (1st gap), S phase (synthesis), G2 phase (second gap)
- cell grows during all three phases but chromosomes duplicate in S phase
Mitosis five stages
- prophase
- prometphase
- metaphase
- anaphase
- telophase
- cytokinesis overlaps the latter stages of mitosis
mitotic spindle
a structure made of microtubules and associated proteins - controls chromosome movement in mitosis
- assembly of spindle begins at the centrosome
centrosome
a type of microtubule organizing center
interphase
the centrosome replicates, forming two that migrate to opposite ends of cell during prophase and pro metaphase
an aster
a radial arrow of short microtubules; extends form both centrosomes
The spindle =
centrosomes + spindle microtubules + asters
prometaphase
spindle microtubules attach to the kinetochores of chromosomes and begin to move them
kinetochores
protein complexes that assemble in sections of DNA at centromeres
metaphase
the centromeres of all chromosomes are at the metaphase place
metaphase plate
an imaginary structure at the midway point between the spindles two poles
non-kinetochores microtubules form opposite poles…
overlap and push against each other, elongating the cell
Anaphase
duplicate groups of chromosomes arrive at opposite ends of elongated parent cell
- microtubules shorten
- chromosomes “reeling in” by motor proteins at spindle poles
How are microtubules shortened?
depolymerizing at their kinetochore ends; happens after they pass by motor proteins
Cytokinesis begins during
anaphase or telophase, spindle disassembles
- occurs by process know as cleavage, forming cleavage furrow
- in plants, cell plate forms during cytokinesis
Binary fission
type of cell division for how prokaryotes reproduce
- single chromosome replicates at origin of replication
- two daughter chromosomes move apart while cell elongates
- plasma membrane pinches inward, dividing cell into two
the eukaryotic cell cycle is regulated by
a molecular control system - frequency of cell divisions varies with type of cell (regulated)
- cancer cells are the exception
cytoplasmic signals
specific signaling molecules present in the cytoplast; drive the cell cycle
study on cytoplasmic signals`
cells fused at different stages, cytoplasmic signals caused nucleus of second cell to enter “wrong” stage of cell cycle control system
sequential levels of cell cycle directed by
cell cycle control system
cell cycle control system
similar to timing device of washing machine; regulated by both internal and external controls
- checkpoints: Where the cell stops until a go-ahead signal is received
- G1 checkpoint is most important -go-ahead and it will compete S1, G2 and M phases and divide; NO go-ahead and it will exit the cycle, switching into a non-dividing state called G0
The cell cycle is regulated by
proteins and protein complexes like kinases and proteins called cyclins
M phase checkpoint
anaphase does not begin if any kinetochores remain unattached to spindle microtubules
- attachment of all kinetochores -> activates regulatory complex -> activates enzyme seperase
seperase
allows sister chromatids to separate, triggering the onset of anaphase
growth factors
proteins released by certain cells that stimulate other cells to divide; external signals
- platelet-derived growth factor (PDGF): stimulates the division of human fibroblast cells in culture
- density depended inhibition: in which crowded cells stop dividing
- anchorage dependence: in which they must be attached to a substratum in order to divide
Cancer cells do not
respond to signals that normally regulate the cell cycle - do not need growth factors to grow and divide
- may make own growth factor, may convey a growth factor’s signal without the presence of the growth factor
- they may have an abnormal cell cycle control system
Transformation
A normal cell is converted to a cancerous cell through this process
- cancer cells not eliminated by the immune system for tumors
HeLa Cells (Henrietta Lacks)
one of the most studied human cell lines - cells from her cervical cancer were 1st to be grown in culture
tumors
masses of abnormal cells within otherwise normal tissue
- benign: abnormal cells remain only at origin site
- malignant: invade surrounding tissues and undergo metastasis
metastasis
exporting cancer cells to other parts of the body, where they may form additional tumors
a localized tumor may be traced with
high energy radiation or chemotherapy
chemotherapy
used to treat suspected metastic tumors
- drugs that are toxic to actively dividing cells
-side effects due to drug’s effects on normal cells
