D 2.1 - CELL AND NUCLEAR DIVISION, B 1.1 CARBOHYDRATES & LIPIDS

Created by

Riti W

Cards (213)

why do all organisms need to produce new cells
growth, maintenance and reproduction
how do organisms produce new cells
cell division - one cell divides into two (mother cell too two daughter cells)
what happens to the mother cell in the process of cell division 
mother cell disappears as an entity in the process
what are the three factors of cell theory
1. All organisms consist of cells2. All cells come from pre-existing cells3. Cells are the smallest units of life
what evidence can we give that cells are formed from pre-existing cells
zygote which was formed by the fusion of a sperm and egg cell
What is cytokinesis?
splitting of the cytoplasm // cytoplasm of a cell is divided between two daughter cells
when does/can the process of cytokinesis happen
as soon as chromosomes have separated and are far enough apart to ensure that none of them ends up in the wrong cell
is cytokinesis in plant cells the same as in animal cells
no
process of cytokinesis in an animal cell
plasma membrane is pulled inwards around the equator of the cell to form a cleavage furrow - done by using a ring of contractile proteins immediately inside the plasma membrane
What is a cleavage furrow?
indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process of cell division
What are the contractile proteins?
actin and myosin and are similar to those that cause contraction in muscles
happens when the cleavage furrow reaches the centre
cell is pinched apart into two daughter cells
how many stages of cytokinesis do plants have
2
first process of cytokinesis in a plant cell
microtubules are built into a scaffold straddling the equator, which is used to assemble a layer of vesicles - vesicles fuse together to form plate-shaped structures
what happens in plant cells when more vesicles fuse together - cytokinesis 
two complete layers of membrane are formed across the whole of the equator of the cell - plasma membranes which connect to the pre-existing plasma membrane completing the division of the cytoplasm
what is the second part for plants
pectin's and other substances are brought in vesicles and deposited by exocytosis between the two new membranes - forms middle lamella which link the new cell walls. Both daughter cells will bring cellulose into the equator and deposit it by exocytosis adjacent tot he middle lamella
what is equal cytokinesis 
where the cytoplasm of the mother cell has been divided into equal halves
where does equal cytosis take place - one example
growing root tip
why is the root growth 
grows due to enlargement and division of cells arranged in columns
why is root growth equal cytokinesis
cells in a column all differentiate in the same way so cytoplasm is apportioned equally when they divide
what is unequal cytokinesis 
where the cytoplasm does not split equally
what must be ensured for an unequal split in cytoplasm to allow the cell to keep on living
can survive and grow if they have a nucleus and at least one of each organelle that can't be assembled from components in the cell
how can mitochondria be produced
by division of pre-existing mitochondrion
examples of unequal division
budding in yeast and oogenesis in humans
how do yeast cells reproduce
reproduce asexually in a process called budding
What is budding?
a new individual grows on the parent then separates
how does the nucleus in yeast cells divide
by mitosis and is given to the small outgrowth on the parent cell
describe the process of budding
nuclei and small amounts of cytoplasm is given to small outgrowth; a dividing wall is constructed separating the two cells and the small cell splits away
what is left once budding has ended
a scar to where it was attached on the larger cell
is budding a repeated process 
yes and it does not have to double in size between each division
What is oogenesis?
production of female gametes
what happens during sperm production
the cytoplasm is divided equally in the first and second divisions, resulting in four, equally sized small cells, each of which develops into a mature sperm
why is there unequal distribution of cytoplasm in oogenesis 
only one egg produced at a time, with enough stored food to sustain the developing embryo
what does the first division in oogenesis produce 
one large cell with nearly all the cytoplasm and a small polar body which does not develop further
which out of large cell and small polar body carries out the second division
large cell
what happens in the second division in oogenesis
the large cell experiences unequal division of the cytoplasm resulting in one large cell and one very small polar body
what happens to the large cell produced
develops into a mature oocyte that is ready for fertilisation
what surrounds the oocyte
zona pellucida
what is zona pellucida
thick outer, protective covering of human egg cell. penetrated by sperm acrosome
What are anucleate cells? 
without a nucleus