cell specialisation

Question 1

what are the levels of organisation in an organism

Answer 1

specialised cells —> tissues —> organs —-> organ systems —> whole organism

Question 2

what are the different cells in an organism specialised for

Answer 2

different roles and organsied into efficient biological structures each with a particular function

Question 3

how do the necessary life functions happen in single celled organism

Answer 3

in one cell

Question 4

why do single celled organisms need only one cell to carry out all their functions

Answer 4

single celled organisms are small with a large surface area to volume ratio so oxygen can diffues out and carbon dioxide can diffuse in easily via the same membrane

Question 5

what can mutlicellular organisms do

Answer 5

delegate jobs to particular groups of cells.

Question 6

why do multicellular organisms need speciallised cells to carry out their functions

Answer 6

they are larger with a small surface area to volume ratio so most of the cells aren’t in direct contact with the external environment.

Question 7

what are specialised cells

Answer 7

cells that have adapted to form a particular function

Question 8

what is differentiation

Answer 8

process by which stem cells become specialised into different types of cells

Question 9

how do multicellular organisms start as

Answer 9

zygotes - when sperm and egg fuse to give a diploid nucleus in the cell

Question 10

what is different about the zygote

Answer 10

its not specialised and all the genes in the genome are able to be expressed. its able to divide by mitosis

Question 11

what is the name for an unspecialised cell

Answer 11

stem cell

Question 12

what forms after several mitotic divisions of the zygote

Answer 12

an embryo forms

Question 13

what does an embryo contain

Answer 13

undifferentiated embryonic stem cells

Question 14

why do embryonic stem cells differentiate

Answer 14

certain genes are switched off and others are expressed more so that the proportions of the different organelles differ from those of other cells. the shape of the cell changes. some of the contents of the cell change.

Question 15

what happens because of differentiation

Answer 15

each cell is specialised for a particular function

Question 16

what are erythrocytes

Answer 16

red blood cells

Question 17

why do erythrocytes have a flattened biconcave shape

Answer 17

it increases their surface area to volume ratio which is essential to their role of transporting oxygen around the body

Question 18

why dont erythrocytes have a nucleus or many other organelles

Answer 18

it increases the space for haemoglobin (carries oxygen)
the organelles are lost at differentiation

Question 19

where is haemoglobin synthesised

Answer 19

inside imamature erythrocytes

Question 20

why are erythrocytes flexible

Answer 20

so they can squeeze throug narrow capillaries

Question 21

what are other features of erythrocytes

Answer 21

• they derive from stem cells in bone marrow
• small (7.5 µm in diameter)
• well developed cytoskeleton so they can twist and turn
• transports oxygen from the lungs to respiring cells

Question 22

what are neutrophils

Answer 22

white blood cell

Question 23

what is the role of neutrophils

Answer 23

engulfs pathogens playing an important role in the immune system

Question 24

what does the characteristic multi lobed nucleus do for the neutrophil

Answer 24

it makes it easier for them to squeeze through small gaps to get to the sites of infection

Question 25

what does the granular cytoplasm of neutrophils do

Answer 25

they contain many lysosomes that contain enzymes used to surround and engulf pathogens

Question 26

how do neutrophils travel towards infection sites

Answer 26

by chemotaxis - they detect the chemicals given off by invading microbes

Question 27

what are sperm cells

Answer 27

they are male gametes. their function is to deliver genetic information to the female gamete and fertilise it

Question 28

why do sperm cells have a tail/flagella

Answer 28

it makes them capable of movement

Question 29

why do sperm cells need many mitochondria

Answer 29

to supply the energy needed to swim

Question 30

what is the role of the acrosome on the head of the sperm

Answer 30

contains digestive enzymes which are released to digest the protective layers around the ovum and allow the sperm to penetrate leading to fertilisation

Question 31

give other features of sperm cells

Answer 31

- they are small but long and thin - the head of the sperm contains haploid nucleus and very little cytoplasm

Question 32

where is squamous epithelial tissue found

Answer 32

they form the lining of the lungs and the walls of the alveoli and capillaries

Question 33

what is the function of squamous epithelial cells

Answer 33

allows rapid diffusion of oxygen into the blood

Question 34

why is important for the squamous epithelial tissue to be one cell thick

Answer 34

gives it a short diffusion pathway allowing rapid diffusion of oxygen into the blood

Question 35

give other features of squamous epithelial tissue

Answer 35

- thin - has a flat appearance - forms sheets connected by tight junctions and desmosomes

Question 36

what is a desmosome

Answer 36

specialised adhesive protein complexes found at intracellular junctions and responsible for joining cells together forming a complete barrier

Question 37

where are the ciliated epithelial tissues found

Answer 37

they line the trachea sweeping away the mucus away from the lungs and bronchi

Question 38

what do the cilia on epithelial tissues do

Answer 38

they move in a rhythmic manner which sweeps away mucus away from the lungs

Question 39

what does the mucus do

Answer 39

traps any unwanted particles and prevents bacteria from reaching the alveoli once its inside the lungs

Question 40

what releases the mucus

Answer 40

goblet cells

Question 41

give other features of ciliated epithelial tissues

Answer 41

they have short life cycles so they can replace themselves. they are tall columnar cells that withstand pressure forces such as breathing and coughing

Question 42

what are palisade cells

Answer 42

present in the mesophyll containing many chloroplasts which absorb large amounts of light for photosynthesis

Question 43

where are palisade cells found

Answer 43

within leaves

Question 44

why do palisade cells need lots of chloroplasts

Answer 44

to absorb large amounts of light for photosynthesis

Question 45

why are palisade cells long and cylindrical

Answer 45

so they pack together quite closely but with a little space between them for air to circulate

Question 46

how does carbon dioxide diffuse into palisade cells

Answer 46

in the small spaces between the cells

Question 47

where are the chloroplasts positioned on palisade cells and why is that

Answer 47

positioned at the edge of the cell to reduce the diffusion distance for carbon dioxide

Question 48

what does the large vacuole on palisade cells maintain

Answer 48

turgor pressure

Question 49

give other features of palisade cells

Answer 49

- thin cell walls - contain cytoskeleton threads and motor proteins to move the chloroplasts - nearer to the upper surface of the leaf when sunlight intensity is low but further down when it is high

Question 50

what is role of root hair cells

Answer 50

absorb water and minerals

Question 51

where are root hair cells found

Answer 51

present at the surfaces of roots near the growing tips

Question 52

what is the purpose of the "root hairs"

Answer 52

the long extensions increase the surface area maximising the absorption of water and mineral ions such as nitrates from the soil into which it projects

Question 53

why do root hair cells have many mitochondria

Answer 53

cells will need to produce ATP for active transport

Question 54

what do the carrier proteins in the plasma membrane in root hair cells do

Answer 54

they actively transport the mineral ions in lowering the water potential within them and causing the water to flow by osmosis down the concentration gradient

Question 55

what are the functions of guard cells

Answer 55

pairs of specialised cells that control the opening and closing of the stomata

Question 56

where are guard cells found

Answer 56

lower epidermis

Question 57

guard cells contain chloroplasts but why dont they carry out photosynthesis

Answer 57

they dont have the enzymes needed for the 2nd stage of the process

Question 58

what do the chloroplasts on guard cells do

Answer 58

absorb light energy to produce ATP to actively transport potassium ions from surrounding epidermal cells into the guard cells lowering their water potential. this allows water to enter

Question 59

what is different about the cellulose cell wall on guard cells

Answer 59

its more flexible at the tips and rigid where its more thicker. thickened wall on inner edge but not on the outer edge

Question 60

what do guard cells allow

Answer 60

carbon dioxide to enter

Question 61

what happens when guard cells lose water

Answer 61

they become less swollen allowing them to change shape and the stoma closes to prevent further water loss from the plant

Question 62

why is the cell wall of a guard cell thicker on one side

Answer 62

so the cell doesnt change shape symmetrically as its volume changes