B2.3 - cell specialisation

Question 1

anterior

Answer 1

head end

Question 2

posterior

Answer 2

tail end

Question 3

expressed

Answer 3

when info in a gene is used to synthesis a protein - when genes are “switched on”

Question 4

mulitnucleate

Answer 4

containing more than one nucleus

Question 5

oocyte

Answer 5

egg cell

Question 6

oogenesis

Answer 6

formation of an egg cell

Question 7

proteome

Answer 7

all the proteins produced by a cell

Question 8

sebaceous

Answer 8

oil-producing

Question 9

stem cell niche

Answer 9

an area within an organism where stem cells are located and receive signals to control their fate

Question 10

differentiation

Answer 10

process in which different genes are expressed in a cell
- can be a different sub-set of genes
- production of a different concentration of a protein

Question 11

what is the process for the development of an early-stage embryo?

Answer 11

1. gametes undergo fertilisation to produce a zygote
2. zygote divides by mitosis to form a ball of unspecialised cells
3. diffentiation is necessary for embryonic development and leads to the formation of specialised cells

Question 12

zygote

Answer 12

unspecialised cell

Question 13

what evidence is there for differentiation?

Answer 13

biochemical evidence from analysis of proteins which are present in different concentrations in different cells, so have different proteomes despite sharing a genome

Question 14

what determines which genes are expressed in an early embryo?

Answer 14

combination of concentrations of signalling molecules called morphogens

Question 15

how are gradients of the morphogen proteins formed?

Answer 15

1. mRNA molecules from “maternal effect genes” are deposited at the poles of the oocyte during oogenesis
2. gradients of the maternal effect proteins are created after fertilisation and multiple rounds of nuclear division
3. deposited mRNA is translated and the protein products diffuse away from the site of production
4. particular combination of concentrations identifies the position of the cell within an embryo

Question 16

how can gradients of bicoid and nanos be formed?

Answer 16

1. bicoid mRNA is deposited at the anterior end and nanos mRNA is deposited at the posterior end
2. bicoid protein is produced in the anterior region and diffuses away and nanos protein is produced in the posterior end and diffuses away
3. the higher the concentration of the bicoid protein and the lower the concentration of the nanos, the closer to the anterior end
4. the higher the concentration of the nanos protein and the lower the concentration of the bicoid, the closer to the posterior end

Question 17

what are the properties of stem cells?

Answer 17

• capacity to divide endlessly due to self-renewal
• less differentiated than body cells
• have the capacity to differentiate along different pathways to produce specialised cells

Question 18

stem cell

Answer 18

a cell that has not yet undergone differentiation

Question 19

stem cell niche

Answer 19

areas where stem cells are found in large numbers
- maintains the cells or promotes differentiation

Question 20

what are 2 areas of stem cell niches?

Answer 20

• bone marrow
• hair follicles

Question 21

bone marrow

Answer 21

contains stem cells that self-renew to produce blood
- transported in the circulatory system

Question 22

hair follicles

Answer 22

contain 2 regions of stem cells
- bulge stem cells - produce skin, hair and sebaceous gland cells
- dermal papillae - regulates hair follicle development and growth

Question 23

what are the 3 types of stem cells?

Answer 23

• totipotent stem cells
• pluripotent stem cells
• multipotent stem cells

Question 24

totipotent stem cells

Answer 24

embryonic stem cells that can differentiate into all cell types and can form a functional organism

Question 25

pluripotent stem cells

Answer 25

embryonic stem cells that can differentiate into almost all cell types but cannot form a functional organism

Question 26

multipotent stem cells

Answer 26

have the ability to differentiate into some cell types
- adult stem cells and umbilical cord stem cells

Question 27

what happens to surface area and volume as a cell size increases?

Answer 27

• surface area increases by a factors of the squared width
• volume increases by a factor of the cubed width
• ratio decreases (inverse proportion)

Question 28

model

Answer 28

simplified versions of complex systems

Question 29

how can surface area and volume affect exchange?

Answer 29

exchange of materials - depends on area
need for exchange - depends on volume
- larger organisms have more cells rather than bigger cells as they are limited in the size they can reach so that they are able to support life functions

Question 30

how is cell size important for sperm cells?

Answer 30

small size is sufficient to deliver genetic material
(3μm in diameter and 50μm in length)

Question 31

how is cell size important for egg cells?

Answer 31

large volume supplies the molecules and organelles to support early cell division during development
(120μm in diameter)

Question 32

how is cell size important for muscle fibres?

Answer 32

long fibre means there are a lot of contractile units stacked, leading to greater shortening of the muscle when each unit contracts
(10-50μm wide and 40-120mm in length)

Question 33

how is cell size important for neurons?

Answer 33

extremely long to rapidly transmit information via electrical impulses
(3-18μm in diameter, 350μm - 1.5m in length)

Question 34

how is cell size important for erythrocytes?

Answer 34

small size allows movement through capillaries
(7.5μm in diameter)

Question 35

how is cell size important for white blood cells?

Answer 35

larger size as it contains nuclei and organelles to carry out specific functions
(12-15μm in diameter)