LECTURE 14 Flashcards
Is oxygen toxic and why ?
Uses,it reacts with organic molecules (including DNA) casing them to function improperly.
Organism. Can be placed in two categories with respect to O2
Anaerobic and aerobic
Anaerobic
O2 not used
Aerobic
O2 used
Obligate anaerobes
O2 is toxic
Aerotolerant anaerobes
O is not used
Facilitative anaerobes
Use O2 when its available
Obligate aerobes
O2 is required/needed
Cecil are respiration produces a lot of ATP from glucose, but if O2 is unavailabe for cellular respiration, then the organism has to
Use a secondary metabolic pathway
With out O2, there are tow ways to make ATP form organic molecules
1) continue to use electron transport chain, but use a different terminal e- acceptor (instead of O2)
2) use glycolysis to make ATP (doesn’t require O2). Oxidizing agent is NAD+, but without the e- transport chain, NADH will quickly build up. To continue, NAD+ will be regenerated.
Some prokaryotes that live in anaerobic conditions can perform
anaerobic respiration
Two types of fermentation
1) alcohol fermentation
2) lactic acid fermentation
Alcohol fermentation
Pyruvate is converted to ethanol in 2 steps with release of CO2.
used in brewing , winemaking and baking.
Lactic acid fermentation
Pyruvate is reduced by NADH, forming lactate as end product, without release of CO2
Makes cheese and yogurt
Muscle cells use this type off mere taint to generate ATP she O2 is scarce.
Cancer cells becomes more
Hypoxic
Hypoxic
Low oxygen, tumour grows it becomes more difficult for blood vessels to get O2 to the centre, becoming a site of lactic acid fermentation and glycolysis. Becomes primary source of ATP.
Blood vessels may be stimulated to gorw into the tumour mass for cancer cells, allowing the tumour to
Grow even larger
As tumours get larger, cells becomes more
efficient in importing glucose (glucose uptake correlates with poor prognosis)
PET scans so what too track tumours
Trace glucose movement because cancer cells increase glycolysis and intake last of it
This is done is isotope Fluorine-18
Which cells dont do fermentation
Nerve cells
Why would a cell not do fermentation
The don’t have the necessary enzymes
The cells that dont do fermentation :
- these are the first to die if deprived of O2
- cannot make ATP uncles O2 is present
- cannot maintain proper ion balance and membrane potential
- leads to cell damage, cessation of nerve function, death to organism
A stoke is an
interruption of blood supply (oxygen) to a localized area in the brain, resulting in cell death
All offs can be used as a source of energy IF they can be
Broken down to molecules that can enter glycolysis or Krebs cycle
Proteins break down into _____ which can enter _______ ________ and ___________
Amino acids
Pyruvate, acetyl CoA, and Krebs cycle
(Glycolysis and Krebs)
Carbohydrates break down to ________ and enter ________
Sugars and enter glucose
glycolysis
Fats break down to ____and ______ and enter into ______ and _________
Fats break down to glycerol and fatty acids and enter into glyceraldehyde-3- and acetyl CoA
Cells can also siphon off intermediates form glycolysis and krebs to use as
molecular building blocks as needed
PFK activity is _________ allosterically by high levels of ATP in cells
Inhibited
If cells generate more ATP the they can use, they prevent/slow glycolysis by
Inhibition of PFK
Excess glucose can be
1) stored
2) used in other metabolic pathways to makes other required molecules
AMP stimulates
PFK to be more active
As ATP is used, and AMP accumulates, this signals the cell to
make more ATP by stimulating PFK (glycolysis)
Citrate, the first product in the Krebs cycle, inhibits _____
- citrate formation Is fed by ______
PFK. Glycolysis
If citrate concentrations becomes to high, the
cell doesn’t need to make more
Cell division in BOTH prokaryotes and eukaryotes include
1) a reproductive signal that tells cell when to divide (can be inside or outside of cell)
2) DNA replication: each daughter cells relieves copy of DNA
3) DNA segregation: replicated DNA gets distributed to new cells
4) Cytogenesis: each new cells has cell membrane and cell wall if parents has one.
Reproductive signals in prokaryotes (binary fission)
They sense their environment and respond by alternating their cellular functions.
The time required to divide is called
Doubling time or generation time
Generation time is determined by :
- type of organism
- level of nutrients, wastes
- temp
A log plot of cell division shows it in a
theoretician situation with unlimited nutrients and no water build up.
Real growth is shown through exponential growth
Lag phase
- Little to no division occurring
- still have metabolic activity (growing in volume, synthesizing enzymes, proteins, RNA)
Log phase
- cells begin to divide
- cell number doubles at a rate
- use up nutrients and excretes waste products
Stationary phase
- metabolic rate of cells decrease
- cells die and divide at the same time
Death phase
- causes not always clear
- cells lays due to damaged cell walls
- toxicity of waste products
In all prokaryotes, the genetic info is contained in a single
Circular chromosome
Ori
(Origin) : site on DNA molecules where replication begins
Ter
(Terminus) : the site where replication ends
Prior to cell division, the bacterial chromosome starts to
Duplicate
- each daughter cell will recreate a fully copy
Prokaryotic DNA synthesis occurs at the
same time as other metabolic process in the life cycle, unlike eukaryotes, which separate DNA replication form other stages of life.
DNA segregation in prokaryotes
- before DNA is replicated, it is distributed throughout the cytosol
- immediately after DNA starts to replicate, dynamic actin like protein subunits bind to a region next to the ori and form filaments that help separate the two replicating nucleotides as they finish replication
- ParM
ParM involved in
Plasmid partitioning
Cytokinesis in prokaryotes
FtsZ proteins form a ring that pinches cell membrane inwards until cytosol separates
As the membrane pinches in, new cell wall materials are
deposited in the plane of the FtsZ ring (septum) which finally separated into two new cells
Septum
The new barrier that forms when the FtsZ ring pinches during cytokinesis in prokaryotes
