2.6.4 diversity in animal cells

Question 1

differentiation

Answer 1

process by which stem cells become specialised into diff. types of cells

Question 2

epithelial cells

Answer 2

cells that form lining tissue

Question 3

erythrocyte

Answer 3

red blood cell

Question 4

neutrophil

Answer 4

type of white blood cell that is phagocytic

Question 5

meaning of phagocytic

Answer 5

can ingest microbes & small particles

Question 6

stem cell

Answer 6

unspecialised cell able to express all of its genes & divide by mitosis

Question 7

do single-celled organisms require cell differentiation/specialisation

Answer 7

no, as:
- small
- large SA:V ratio
- thus, oxygen can diffuse across their plasma membrane & waster products can diffuse out

Question 8

why do multi-cellular organisms require cell differentiation/specialisation

Answer 8

• larger
• smaller SA:V ratio
• thus, most of cells not in direct contact with external environment

Question 9

what do multicellular organisms start life as

Answer 9

single undifferentiated cell = zygote

Question 10

what is a zygote a result of

Answer 10

• when an ovum (egg cell) is fertilised by a spermatozoon
• the 2 haploid nuclei fuse to give a cell with a diploid nucleus

Question 11

characteristics of a zygote

Answer 11

• unspecialised
• all genes in genome are able to be expressed
• able to divide by mitosis
• it is a stem cell

Question 12

when does an embryo form

Answer 12

after many mitotic divisions

Question 13

what occurs when an embryonic stem cell differentiates

Answer 13

• proportions of different organelles differ from those of other cells
• shape of cell changes
• some of contents of cell change

Question 14

specialised animal cells - eg. erythrocytes & neutrophils FUNCTION

Answer 14

erythrocytes = carry oxygen from lungs to respiring cells
neutrophils = ingest invading pathogens

Question 15

where are erythrocytes/neutrophils derived from

Answer 15

stem cells in the bone marrow

Question 16

how are erythrocytes adapted for their function

Answer 16

• very small = 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

Question 17

how are neutrophils adapted for their function

Answer 17

• 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

Question 18

how are spermatozoa cells specialised (sperm cells)

Answer 18

• 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

Question 19

acrosome

Answer 19

specialised lysosome

Question 20

how are epithelial cells specialised

Answer 20

• squamous epithelial cells = flattened in shape
• many of cells in epithelium have cilia