B2.3 Cell Specialisation Flashcards
(40 cards)
Fertilisation
fusion of gametes to produce single egg cell.
how is an embryo formed
through repeated divisions cell undergoes to generate embryo of many cells. Mitosis in cells ensures embryo are genetically identical.
How do cells specialise
early stage embryo, cells unspecialised, as it grows cells develop along pathways and specialise to different functions.
develop an ideal structure with enzymes necessary
what is differentiation
the development of cells in different ways to carry out specific functions.
different sequence of genes is expressed in different cell types
what is gene expression?
when a gene is used in a cell, ‘switched on’ and info in is used to make a protein/other gene product.
development of cell involves expressing particular genes but not others.
why does position of a cell in embryo determine how it differentiates
must be enough cells of each type and must be in positions where they are needed.
how is the position of a cell indicated and how is the pathway of differentiation determined?
gradients of signalling chemicals indicate cells position, acting as regulators, determining differentiation pathway.
what is a stem cell?
cell that is able to divide repeatedly.
e.g skin stem cells repeatedly divide, replacing lost skin cells.
what happens when a cell is produced by division of a stem cell?
can remain as a stem cell or differnetiate into specific cell type, once differentiated, no longer stem cells.
what are stem cells categorized as
undifferentiated/partially differentiated, capable of differentiating along diff pathways.
where is the location of stem cells in adult humans
some remain in adult body, e,g bone marrow skin liver, these give tissues regeneration and repair.
precise location is the ‘stem cell niche’
what does the stem cell niche provide
an microenvironment with conditions needed for stem cells to remain inactive/undiffernetiated over long periods.
and also to proliferate rapidly/differentiate when required.
e.g striated muscle, during injury changes in niche cause proliferation and differentiation to replace damages.
why are niches of research interest?
can be simulated outside of body for particular stem type.
can produce human tissue in vitro(glass) and use it for restorative surgery.
also non-therapeutic uses, e.g producing large quantities of muscle fibres/meat.
what are totipotent stem cells?
can differentiate into any cell type and are found in early stage embryos.
how do embryonic stem cells change?
cells commit to particularly pathway of differentiation during development, may commit along one path/another.
can change to pluripotent. being able to differentiate into a range but not every type.
what are multipotent stem cells
can differentiate into several types of mature cells.
how does the size of mature differentiated cell such as sperm adapted to perform its function
50micrometer long, extremely narrow, reduces resistance and allows swimming to egg more easily.
how does the size of mature differentiated cell such as sperm adapted to perform its function
how does the size of mature differentiated cell such as red blood cells adapted to perform its function
6-8 micrometres in diameter but indented on both sides, 1micrometre think middle.
small size+shape allows passage along narrow capillaries give large SA-VOL ratio, loading+unloading of oxygen faster.
biconcave shape gives lower vol, and smaller max distance from cytoplasm to plasma membrane.
how does the size of mature differentiated cell such as white blood cells adapted to perform its function
B-lymphocytes are only about 10 micrometres in diameter when inactive, enlarge to 30 micrometres if activated become antibody secreting plasma cells.
how does the size of mature differentiated cell such as cerebellar granule cells adapted to perform its function
cell body only 4 micrometres in diameter.
twin axons extend for about 3mm (3000micro) in cerebellar cortex.
very small volume allows cerebellum to accommodate 50 billion of them-75% of brains neurons.
how does the size of mature differentiated cell such as motor neurons adapted to perform its function
cell body is about 20 micrometres in diameter, large size allows enough proteins to be synthesised to maintain immensely long axon.
can extend for a metre (million micrometre), so can carry signals from CNS to distant muscle.
how does the size of mature differentiated cell such as striated muscle fibres adapted to perform its function
larger than normal, diameter 20-100 micrometre, lengths can exceed 100mm (100k micro).
Dimensions allow fibre to exert > force, and contract by a greater length than smaller muscle cells.
Metabolism
chemical reactions taking place in cyto, metabolic rate is proportional to vol of cell.
for meta to continue, substances used in reactions must be absorbed by cell and waste products must be expelled.
rate at which substances move in/out of cells depends on surface area.