2.6.4 diversity in animal cells Flashcards
differentiation
process by which stem cells become specialised into diff. types of cells
epithelial cells
cells that form lining tissue
erythrocyte
red blood cell
neutrophil
type of white blood cell that is phagocytic
meaning of phagocytic
can ingest microbes & small particles
stem cell
unspecialised cell able to express all of its genes & divide by mitosis
do single-celled organisms require cell differentiation/specialisation
no, as:
- small
- large SA:V ratio
- thus, oxygen can diffuse across their plasma membrane & waster products can diffuse out
why do multi-cellular organisms require cell differentiation/specialisation
- larger
- smaller SA:V ratio
- thus, most of cells not in direct contact with external environment
what do multicellular organisms start life as
single undifferentiated cell = zygote
what is a zygote a result of
- when an ovum (egg cell) is fertilised by a spermatozoon
- the 2 haploid nuclei fuse to give a cell with a diploid nucleus
characteristics of a zygote
- unspecialised
- all genes in genome are able to be expressed
- able to divide by mitosis
- it is a stem cell
when does an embryo form
after many mitotic divisions
what occurs when an embryonic stem cell differentiates
- proportions of different organelles differ from those of other cells
- shape of cell changes
- some of contents of cell change
(specialised animal cells) function of erythrocytes & neutrophils
erythrocytes = carry oxygen from lungs to respiring cells
neutrophils = ingest invading pathogens
where are erythrocytes/neutrophils derived from
stem cells in the bone marrow
how are erythrocytes adapted for their function
- very large SA:V
–> oxygen can diffuse across membranes & easily reach all regions in cell
–> biconcave shape increases SA:V - flexible
–> well developed cytoskeleton allows them to change shape (twist/turn) to travel through narrow capillaries - most of organelles lost at differentiation
–> no nucleus, mitochondria or endoplasmic reticulum & very little cytoplasm
–> more space for haemoglobin molecules housed in them
how are neutrophils adapted for their function
- twice the size of erythrocytes
- each neutrophil contains multilobed nucleus
- attracted to/travel towards infection sites by chemotaxis
- function = ingest bacteria/some fungi by phagocytosis
how are spermatozoa cells specialised (sperm cells)
- many mitochondria for aerobic respiration
–> ATP provides energy for undulipodium (tail) to move/propel cell towards ovum - small but long/thin
–> move easily - once it reaches ovum, enzymes are released from acrosome
–> digest outer protective covering of ovum = sperm cell can enter ovum - head of sperm contains haploid male gamete nucleus & very little cytoplasm
acrosome
specialised lysosome
how are epithelial cells specialised
- squamous epithelial cells = flattened in shape
- many of cells in epithelium have cilia
