B2.3 cell specialisation

stem cell properties

1. unspecialised

2. can divide repeatedly

   • 1 daughter cell can undergo specialisation

   • the other daughter cell continues to be divided

3. can reverse differentiation if given the right chemical signals

totipotent

can give rise to all cell types and extra-embryonic tissue

pluripotent

can give rise to all cell types

multipotent

can give rise to all cell types OF a particular tissue or organ

nullipotent

cannot give rise to other cell types / no more differentiation

stem cell niche

precise location of stem cells within a tissue

2 properties of stem cells

• remain inactive and undifferentiated over long periods of time

• proliferate rapidly and differentiate when required

examples of stem cell niche

• bone marrow

• hair follicle stem cells

how is egg cell’s size an aspect of specialisation

large size = large storage of nutrients for zygote

how is red blood cell’s size an aspect of specialisation

high surface area to volume ratio → allows for high rate of gas exchange

small volume and size → move through narrow capillaries

how is white blood cell’s size an aspect of specialisation

small when inactive, enlarges during active infection

how is cerebellar granule cells’ size an aspect of specialisation

long axon small volume → allows for greater accommodation of such cells

adaptations cells have to increase surface area to volume ratio

• folding in surface of cell membrane

• develop long thin or elongated shaped cells / flattened cells

• presence of large vacuoles inside cell that pushes organelles to the side of the cell for easier diffusion of materials

adaptations of type I and type II pneumocytes in alveoli

type I:

• flattened cells

  • reduce diffusion distance

type II:

• rounded cells

• many secretory vesicles in cytoplasm

  • helps increase rate of diffusion

adaptations of cardiac muscle cells and striated muscle fibres

• shorter, 1 nucleus per cell

• Y shaped / branched cell

  • cells can be interconnected

adaptations of egg cell

• zone pellucida

  • layer of glycoproteins containing ZP3 where sperm cells bind to

adaptation of sperm

• tail

  • locomotion

• mid-piece with mitochondria

  • ATP → aerobic respiration → energy for movement

• streamlined shape

  • reduced resistance when reaching to egg cell

• receptors in plasma membrane

  • bind to ZP3

• accrosome

• sac of enzymes that digest proteins