4.Stem cells and apoptosis Flashcards
what are stem cells
Stem cells are non-specialised cells that can divide and differentiate into different specialised cells
what is meant by stem cell ‘potency’
the varying capacity into which stem cells are able to differentiate into
two main types of stem cells
-adult stem cells
-embryonic stem cells
identify the order of stem cell potency from most to least potent
-totipotent
-pluripotent
-multipotent
what is meant by totipotent
the capacity to differentiate into all possible cell types, including extra embryonic tissue
what is meant by pluripotent
the ability to differentiate into all cell types, except those that make up the placenta
what is meant by multipotent
the potential to give rise to cells from multiple, but a limited number of lineages
what is the potency of adult stem cells
multipotent
source of adult stem cell
adult stem cells are isolated from tissue samples
examples of adult stem cell for medical use
-bone marrow transplantation
-regenerative medicine
examples of adult stem cell use in research
-testing new drugs for safety and effectiveness
-model for studying how diseases develop
what is the potency of embryonic stem cells
pluripotent
source of embryonic stem cells
ethical issues raised by stem cells
-human embryos are destroyed when stem cells are extracted
-offering unproven stem cell therapies to those who are desperate
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ethical issues raised by stem cells
-human embryos are destroyed when stem cells are extracted
-offering unproven stem cell therapies to those who are desperate
What is the term that is used to refer to an embryo that is 5 days old and consists of two groups of cells: Trophoblast and Inner cell mass?
blastocyst
define apoptosis
apoptosis is the natural and controlled death of cells in the body. It’s also known as programmed cell death
what is the purpose of apoptosis
-allows old and/or damaged cells to be removed in your body
-allows infected cells to be removed in your body
-allows unnecessary/unwanted cells to be removed during embryonic development
two pathways that can initiate apoptosis
-mitochondrial pathway (intrinsic)
-death receptor pathway (extrinsic)
step 1 of apoptosis
a damaged cell or unwanted cell receive signals that initiate apoptosis
step 2 of apoptosis
once signals are received by the cell, it leads to activation of capsazes
what are capsaze enzymes
group of enzymes that can cleave intracellular proteins
step 3 of apoptosis
as the digestion of cell contents continues, the cell starts to shrink and its membrane starts to bulge out, forming blebs
step 4 of apoptosis
the cell will eventually be broken down into small chunks called apoptotic bodies
apoptosis vs necrosis
-programmed and regulated cell death vs unexpected cell damage/death
-cell shrinks and contents are held in apoptotic bodies vs the cells contents swell and burst
-no inflammation vs inflammation
too much apoptosis
can lead to degenerative diseases
-eg alzheimers
briefly describe alzheimers disease
neurones begin to die leading to brain shrinkage. Because of increased apoptosis
too little apoptosis
-reduced cell death
-can lead to tumours
what is a tumour
a mass of abnormal cells
-in the sense that they divide uncontrollably and lack normal shape and structure
-cant undergo apoptosis naturally instead are flagged by the immune system
G1 checkpoint
-inspects for DNA damage and cell size
metaphase checkpoint
confirms that spindle fibres have correctly attached to the centromeres of replicated chromosomes
G2 checkpoint
confirms that DNA has correctly replicated in the s phase
important proteins involved in apoptosis
-capsaze enzymes
-death receptors
what happens if DNA damage isn’t repaired
-may lead to mutations in genes that code for proteins
-mutated genes may code for less or non functional proteins
-hence a reduced rate of apoptosis
-mutated cells are able to go through the cell cycle with further mutations to their DNA leading to formation of tumours
two classifications of tumours
-benign tumours
-malignant tumours (aka cancers)
characteristics of benign tumours
-relatively slow growing masses of cells that tend to stay together within a capsule
-hence they can’t seperate and invade other parts of the body
-benign tumours can be removed by radiation therapy, often successful
characteristics of malignant tumours
-benign tumours cells can mutate further and become malignant when they gain the ability to invade nearby tissue and/or enter the bloodstream or lymphatic system
metastasis
malignant tumour cells can travel to other parts of body and grow into new malignant tumours
why are cancers (malignant tumours) dangerous
-these tumours can grow in amongst healthy tissues and affect the structure of the healthy tissues
-if the structure of an organ is compromised by a tumour then then the function if the organ will be compromised too.
what causes cancer
carcinogens-are any substance that can increase the likelihood of developing malignant tumours
eg uv light increases risk of skin cancer
