sac1 for bio prt 2

Cytokensis in animal cells

divides by a cleavage.

plasma membrane around middle of cell is drawn inwards forming a cleavage furrow.

As the cleavage furrow deepens, plasma membrane on each side joins up and 2 seperate cells results.

cytokinesis in plant cells

- vesicles produced by the Golgi apparatus collect on the equator, contain proteins, hemicelluloses and cellulose= make up the primary cell wall.

vesicles fuse together to form the cell plate

which eventually stretches forming the middle lamella.

cellulose builds up on sides to form the cell wall of the 2 new cells.

Where are the checkpoints in the cell cycle?

G1 checkpoint: end of G1 , checks, if large enough, enough resources, are dna/chromosomes damaged.

G2 checkpoint: end of G2, check if adequate resources, large enough, are dna/chromosome damaged.

M checkpoint: in metaphase, check if the spindle fibres attached correctly to the sister chromosomes.

If not met cell will not enter next phase.

what is the cell cycle control system?

group of proteins that regulate cell cycle.

types of neoplasms

Benign: localised masses but do not transform into cancer.

potentially malignant: localised masses that will eventually invade other tissues and transform into cancer.

Malignant: these form masses that invade other tissue and transform into cancer.

Cancer

abnormal cell growth

different between cancer and normal cell

divide much faster

division is not controlled by normal signals that control cell cycle

do not have a limited num of divisions

release cell growth hormone

dna mutations occur

do not undergo apoptosis

can spread to other parts of the body.

Apoptosis is

programmed cell death (cell suicide). does not spill cell contents, does not trigger an immune response.

reasons for apoptosis

- cells which are damaged/defective must be eliminated.

- during fetal development, removal of excess cells. (webbing)

necrosis def

- Accidental cell death, unregulated

- causes inflammatory response and damage to surrounding cells.

- damage to plasma membrane and ruptures. cell to explode and contents are released.

necrosis caused by

by physical damage, toxins, pathogens, lack of oxygen.

Major steps in apoptosis a e c b b a

1. activition of apoptotic enzymes, capsizes, within cells

2. enzymes digest cell contents and cell cytoskeleton collapses.

3. cell shrink

4. blebbing of the plasma membrane

5. budding of plasma membrane-bound vesicles (called apoptotic bodies).

6. apoptotic bodies released to be broken down by phagocytes (doesn't spill contents or tigger inflammatory response)

Malfunctions in apoptosis

excessive apoptosis can lead to degeneration disease such as: parkinson's disease.

inhibited apoptosis is seen in syndactyly- skin is not removed during embryonic develop.

Malfunctions in apoptosis: cancer

due to apoptosis not occurring when it should and can be caused:

- genetic mutations that increased rate of cell divison, leads to growth of tumors.

-mutations in capsizes that prevent functioning and causes the capsizes to stop.

-defects in proteins that lead to the activation of capsizes

-defects in the reception of signals that trigger apoptosis.

what are stem cells?

unspecialized cells from which differentiated cells develop

different types of stem cells

embryonic stem cells

adult (somatic) stem cells

induced pluripotent stem cells

(characterised by their ability to differentiate into other cell types (potency))

potency of stem cells tpmu

totipotent: can become any cell type/another embryo

pluripotent: can differentiate into any of the three germ layers

multipotent: can become multiple, but limited cell types.

unipotent: can only differentiate into one type of cell, can divide repeatedly.

embryoic stem cells (esc)

undifferentiated cells from zygote to blastocysts stage: totipotent or pluripotent.

obtained from 3-5 days old blastocysts from ivf program, can become many different types of cells, can replicate indefinitely.

adult stem cells/ somatic stem cells

are multipotent or unipotent

found in small numbers in some adults tissues.

purpose is to repair and regenerate tissues such as skin and liver cells

are not able to replicate indefinitely.

Induced pluripotent stem cells

IPSCs are adult somatic cells that have been genetically reprogrammed to an embryonic stem cell-like state.

are pluripotent stem cells .