Biology B2.3- cell specialisation

stem cells

• unidentified cells that can turn into anything

  • all cells are switched on, meaning they can make every protein

how stem cells become specialised

turn certain cells off- therefore cant make all proteins

morphogens

• single molecules that control cell differentiation

• starts switching genes off which causes the cell to specialize 

stem cell levels

• totipotent

• pluripotent

  • multipotent

  • unipotent

totipotent level

can differentiate into any type of cell

• all stem cells

pluripotent level

can differentiate into many types of cell

multipotent level

can differentiate into a few closely related types of cell

• bone marrow

unipotent level

can regenerate but can only differentiate into their associate cell types

• liver stem cells can only make liver cells

meristem

• in plants

• regions of undifferentiated cells

• plants only grow at the meristems- can be atypical or typical

  • found near root and stem tips

emergent properties

the whole is greater than the sum of its parts

• each part works better together than by themselves and become more efficient

skeletal muscle

• also called striated muscle (has stripes)

how to increase surface area

• invagination- folding inwards

• microvilli- hairs in the intestine

  • flatten the cells

other name for red blood cell

erythrocytes 

do small or large cells have a big or small surface area:volume ratio

• small cells - large ratio

  • large cells - small ratio

advantages of a small cell

• shorter path for diffusion - quicker & more efficient

  • concentration gradient are easier to measure

disadvantages of small cells

• animals loose heat quickly- need to eat constantly

how kidneys increase SA:V ratio

• a way of increasing surface area:volume ratio is flattening cells

• cells are packed closely together to use space well

• tiny microvilli pointing out the cell

• lots of mitochondria in the cell

• flattens the nephron in the kidneys

proximal convoluted tubule

responsible for absorbing essential substances

secreting waste (ions) from filtered blood

type 2 pneumocytes

• capable of mitosis for replacement of both types of alveoli cells

• makes it good for diffusion

• if cells are damaged they are uncappable of mitosis for replacement 

• protect and repair alveoli in lungs

• box shaped cells

• cover about 5% of the surface area

• many of them

  • can divide and replace type 1 and 2 cells after injury

type 1 pheumocytes

• flat and thin shape

• cover 95% of the alveoli surface

• allows gas exchange between alveoli and capillaries

• tightly joined together so no fluids can enter

  • cant divide

3 muscle fibres

• cardiac

• striated skeletal

• smooth

cardiac muscle fibre

• in the heart

• unique function

• contract to pump blood around the body

• has branched cells

• short due to the branching cells

• composed of branched, straited cells

skeletal striated muscle fibre

• long cylindrical shape

• multiple nuclei

• visible bards capable of shortening - produces involuntary movement

• generates force and contract to control movement

• contract to move body parts

  • fast contractions

smooth muscle fibre

• involuntary

• in the walls / organs and blood vessels

• moves substances through the organs

• spindle shape

  • non striated cells → they produce voluntary movement