B2.3 Cell Specialisation Flashcards
what is a stem cell
cell that can divide (by mitosis) an unlimited number of times
what tissues retain stem cells
bone marrow(for rbcs, wbs, platelets)
hair follicle
what is the potency
The ability of stem cells to differentiate into more specialised cell types
totipotent
can differentiate into any type of cell found in an embryo and extra embryonic cells eg. zygote
example of how active white blood cells are differentiated for function
larger than inactive white blood cells to allow space for rER and Golgi apparatus to allow protein (antibody) synthesis
as the size of an organism increases, what happens to its surface area to volume ratio
decreases
more difficult for an organism to gain enough oxygen and nutrients at its cell surface, as its requirements will increase faster than the available surface for diffusion
investigated sa with agar method
cut coloured agar into cubes of required dimensions
calc sa, vol, and sa to v ratio of each cube
place cubes into boiling tubes containing diffusion solution
measure time taken for agar cubes to become colourless
how are red blood cells specialised
function- carry oxygen from lungs to respiring cells
they are FLATTENED and have a BICONCAVE shape to maximise surface area and minimise volume so oxygen can diffuse into it quickly in lungs and out
what are proximal convoluted tubules
tiny tubes found in the outer region of the kidney which are responsible for the reabsorption of vital substances like glucose and mineral ions
how do cells of proximal convoluted tubule increase surface area
have microvilli and invaginations
what are type 1 pneumocytes
extremely thin alveolar cells which make up the majority of the alveolar epithelium
how are type 1 pneumocytes adapted
provide a short diffusion distance to maximise the rate of gas exchange
capillary walls are also only one cell thick maximises the rate of diffusion
what are type 2 pneumocytes
rounded cells that have many secretory vesicles which secrete a solution that coats the epithelium of the alveoli
what is the solution released by type II pneumocytes
pulmonary surfactant has hydrophobic tails and hydrophilic heads
which form a monolayer
benefits of pulmonary surfactant
reduces surface tension, maintaining alveolar shape and preventing the alveoli sacs sticking together
provides moisture so oxygen can dissolve before it diffuses into the blood
Carbon dioxide diffuses from the moist surface before it is removed in exhalation
are skeletal muscles striated
yes
what are striated muscles bundled into
into fibres which are surrounded by a single plasma membrane called the sarcolemma
what does each muscle fibre contain
an organised arrangement of CONTRACTILE PROTEINS in cytoplasm
many nuclei
sarcoplasmic reticulum
mitochondria and myofibrils
what are myofibrils
bundles of actin and myosin filaments, which slide past each other during muscle contraction
what doe the sarcolemma have
many deep tube-like projections that fold in from its outer surface- T tubules they run close to SR
is a cardiac muscle a striated
yes
how are cardiac muscle fibres connected to each other
via specialised branched connections called intercalated discs, which allows the contraction to spread more quickly across the chambers of the heart
how are sperm cells specialised
has a haploid nucleus in streamlined head- fuse w ovum to form diploid zygote
acrosome w digestive enzymes to enter ovum
many mitochondria for movement
a flagellum for movement
why are there lots of mitochondria in muscle fibres
to provide the large quantity of ATP needed for continual contraction
