3.2.2 all cells arise from other cells Flashcards
what is cell fractionation?
the process where cells are broken up and organelle are separated out
what is lysis?
breaking down he membrane of the cell
what happens in cell lysis?
some lysosomes are broken open, proteins inside the cell are exposed to the external solution, organelles are exposed to external solution
why are the cells placed in a buffer solution?
used for the purpose of breaking open cells, endures organelle are not damaged
what factors need to be controlled in a buffer solution?
temperature, pH and amount of water
why does the buffer solution have to be ice cold?
slows down the enzyme activity (less kinetic energy) but doesn’t denature them , no damage to organelle but cells can still respire
why do buffer solutions have to be buffered?
maintains the same pH, prevents proteins from being denatured altering cell structure
why do buffer solutions have to be isotonic?
same water potential as cytoplasm, prevent water entering or leaving organelle by osmosis, prevents osmotic lysis
what are the two stages to cell fractionation?
homogenation and ultracentrifugation
what is homogenation?
disrupting the tissue and cells
what is ultracentrifugation?
separating the organelle in a centrifuge
what happens in homogenation?
using high frequency sound or detergent to form a homogenate, must be in a buffer solution to stop damage to the organelle (mitochondria)
what happens in ultracentrifugation?
crush and filter homogenate to remove debris, spin at low speed and force which forms a pellet at the bottom containing structures of the same density, spin at higher and higher speeds and force, making sure you filter between each time, until you get the desired structure in the pellet
how can you predict which pellet an organelle will be in?
based on the density of the organelle
what is the supernatant?
homogenate that is taken out and spun again
why must the homogenate be filtered before spinning in a centrifuge each time?
so that the sample isn’t contaminated- all that is left is the organelle you are separating
what is the cell cycle?
a regular cycle of cell division, separated by periods of cell growth
what is the cell cycle needed for?
differentiation (cells becoming specialised), growth and repair e.g. in muscle cells
what is the first stage of the cell cycle?
interphase
what is the second phase of the cell cycle?
the mitotic phase
what is the third phase of the cell cycle?
cytokinesis
what are the three parts to the interphase?
growth and normal metabolic roles (G1), DNA replication (Synthesis) , growth and preparation for mitosis (G2)
why is growth and normal metabolic roles important?
growth of the cell and organelle so that each new cell has enough organelle to survive e.g. ribosomes, mitochondria needed for replication
synthesis of DNA polymerase so the reaction replicating DNA can be catalysed
why is DNA replication important?
so that the new cells are identical, and have the same genetic coding and have the correct amount of chromosomes (23 pairs)
why is growth and preparation for mitosis important?
replication of other organelle and prepare the cell for division, check point to make sure that each cell has everything it needs to survive and doesn’t have any abnormalities.
what is apoptosis?
programmed cell death of mutated cells
why is apoptosis important?
to prevent cells with abnormalities dividing further, potentially stopping cancer or tumours
what is G0?
also known as cell arrest, some cells don’t divide at all i.e nerve cells and some cells will stop dividing i.e when we reach adulthood
why does G0 happen?
overcrowding (temporary), differentiation (permanent) when they are specialised they don’t need to be replaced frequently
what is the centromere?
where the spindle fibre attaches during cell division, where the chromatids are joined together
what is a chromosome like before genetic replication?
contains on chromatid
what is a chromosome like after replication?
contains two sister chromatids joined at the centromere
what is a chromosome like after mitosis?
the sister chromatids split to form two chromosomes, each nuclei receives one chromatid per chromosome
what happens in the prophase?
preparation stage, chromosomes condense and become more visible, the nuclear membrane breaks down
what happens in the metaphase?
middle, a microtubule spindle forms within the cell, all the chromosomes line up along the equator (middle) of the cell attached to the spindle
what happens in the anaphase?
chromosomes move apart, microtubules shorten, pulling apart sister chromatids, chromosomes are pulled to opposite poles (ends) of the cell
what happens in the telophase?
formation of TWO new nuclei, new nuclear membranes form, chromosomes de-condense, becomes longer, thinner and less visible
what happens in cytokinesis?
AFTER MITOSIS, cell membrane divides, two daughter cells, each has its own nucleus containing a full set of chromosomes, cell cycle continues to G1
what is mitosis?
a controlled process which produces two identical daughter cells, each daughter cell contains the same number of chromosomes as the parent cell and each other
how do cancer treatments disrupt the cell cycle?
prevent DNA from replicating, inhibiting the metaphase by inhibiting the formation of the spindle
why are healthy cells not affected as much s cancer cells in cancer treatments?
a lot of cells are in G0 so will not be affected as they do not rapidly divide
which cells will be affected by cancer treatments?
hair follicles, nail follicles, immune system i.e. cells that need to be constantly replaced
what is the mitotic index?
the mitotic index tells us the ratio between the number of cells in a population undergoing mitosis to the total number of cells
how do you calculate mitotic index?
number of actively dividing cells in a field of view
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total number of cells in field of view
how to bacterial cells reproduce?
through binary fission
what is binary fission?
a form of asexual reproduction, used by all prokaryotes
what does asexual reproduction include? (5 points)
one parent, no mixture of genetic material, identical offspring, clones, quick
describe the process of binary fission
the DNA of the bacterium uncoils, DNA and plasmids replicate, replicated DNA and plasmids move to different parts of the cell membrane (poles), this causes the cell to lengthen, the equatorial plate of the cell constricts constricts and separates the plasma membrane, each new cell has exactly the same genetic material, the growth of a new cell wall begins to separate the bacterium, the new cell wall fully develops resulting in the complete split of the bacterium.
how is nuclear division in prokaryotes different from in eukaryotes?
binary fission, free floating DNA and plasmids, formation of the cell wall, the cell lengthens when DNA and plasmids move apart, much simpler and quicker, no nucleus/nuclear envelope,fewer/ no membrane bound organelle, free floating DNA, simpler DNA (no junk DNA)
how are mitosis and binary fission similar?
genetic material replicates, genetic material moves to the poles, both result in two identical daughter cells, both asexual reproduction
what is nuclear division like in eukaryotes?
mitosis, chromosomes pulled apart by spindle fibres, formation of nuclear envelope, sister chromatids joined at the centromere, four distinct stages
what is prokaryote DNA like?
single strand of DNA, DNA condenses in the nucleoid, majority of prokaryotes only contain one copy of each gene (haploid), has plasmids, efficient and compact
what is eukaryote DNA like?
multiple linear chromasomes, DNA in nuclear envelope/nucleus, contain pairs of chromosomes/two copies of each gene (diploid), plasmids not commonly present, large amount of non coding and repetitive DNA
what is a centriole?
tiny bundles of protein which begin moving to opposite ends of the cell in prophase, forming a network of protein fibres across the cell called the spindle
what happens in interphase?
the cell carries out normal functions, but also prepares to divide. The cell’s DNA is unravelled and replicated, to double it’s genetic content. The organelles are also replicated so it has spare ones, and it’s ATP content is increased (ATP provides the energy needed for cell division).
