Cell specialisation and differentiation

Question 1

Stem Cells

Answer 1

Unspecialised cells which have the potential to form more specialised different cells

Question 2

Benefits of cell specialisation

Answer 2

• Can perform functions more efficiently
• Cells can develop into specific sizes and shapes which are beneficial
• Cells can create only certain proteins needed for specific metabolic reactions.

Question 3

Differentiation

Answer 3

When different cell types express different genes

Question 4

What causes cells to specialise in an embryo?

Answer 4

Morphogens, specifically Retinoic acid

Question 5

What are morphogens?

Answer 5

Signalling molecules which direct cell fate in a concentration - dependant way

Question 6

How does Retinoic acid specialise cells?

Answer 6

• Certain inducing cells in embryo release morphogen
• Other cells recieve it and it causes certain genes to be expressed
• Cells further from the source have lower rates of differentiation.

Question 7

Stem cell niches

Answer 7

Areas within adults where a pool of stem cells are kept in preparation for future differentiation and proliferation

Question 8

Examples of stem cell niches?

Answer 8

Bone marrow, hair follicle

Question 9

What stem cells do the bone marrow store?

Answer 9

Haemopoietic stem cells which make blood cells

Question 10

What stem cells do the hair follicle store?

Answer 10

Epidermal stem cells which repair wounds and control sporadic bursts of hair growth.

Question 11

Totipotent

Answer 11

Can differentiate into any type of cell. e.g. first eight cells of morula

Question 12

Pluripotent

Answer 12

Can differentiate into all body cells, but not placenta or umbilical cord etc. e.g. inner cell mass of blastocyst

Question 13

Multipotent

Answer 13

Can differentiate into a few closely related cells in the body

Question 14

Unipotent

Answer 14

Can only differentiate into associated cell type e.g. liver stem cells.

Question 15

Liver stem cells

Answer 15

Can repair itself with liver stem cells, but they are unipotent

Question 16

How do sperm cells’ sizes help with function

Answer 16

long, narrow, small volume, reduces resistance - easy movement

Question 17

How do egg cells’ sizes help with function

Answer 17

large, spherical, large volume, can store lots of food reserves

Question 18

How do red blood cells’ sizes help with function

Answer 18

small size and shape - can pass through capillaries
biconcave, high SA:Vol - lots of haemoglobin can be stored and faster transport of oxygen

Question 19

How do white blood cells’ sizes help with function

Answer 19

B - lymphocytes grow 3X their size when activated

Question 20

How do cerebellar granule cells’ sizes help with function

Answer 20

small cell body, long pair axons extended in cerebullar cortex. Small volume allows cerebellum to accomodate lots of these at once

Question 21

How do motor neurons’ sizes help with function

Answer 21

Long axons can pass signals from CNS to distant muscles
Large size allows enough protein synthesis to maintain long axon

Question 22

How do striated muscle fibres’ sizes help with function

Answer 22

larger cells allow fibre to exert greater force and contract by greater length than other muscle fibres

Question 23

What is the ideal SA:Vol ratio for cells and why?

Answer 23

High SA:Vol ratio, so they remain small because if ratio is too small nutrients and waste products cannot be exchanged from the cell fast enough.

Question 24

Different adaptations to increase SA:Vol ratio

Answer 24

• cells dividing instead of infinetly growing
• Tissue surfaces have folds (villi) while cells have membranous extentsions (microvilli) to increase SA
• Cells that are flat and long (squamous) have higher SA relative to Vol

Question 25

Examples of cells specialised for material transport and their adaptations for high SA:Vol

Answer 25

Red blood cells - biconcave shape - increases SA, no nucleus - more haemoglobin can be stored Tubule cells (cells in kidney where selective reabsorption happens) - cells have microvilli - increased SA - more efficient nutrient uptake

Question 26

Pneumocytes

Answer 26

Cells that line alveoli and make up majority of inner lung surface

Question 27

How are pneumocytes type 1 and 2 adapted for their functions?

Answer 27

Type 1 - involved in gas exchange between alveoli and capillaries - squamous shape - reduced diffusion distance - cells connected by occluding junctions, which prevents fluid leakage into alveolar space Type 2 - Secretes pulmonary surfactant, which reduces surface tension in alveoli - cuboidal in shape - have folds - have granules called lamellar bodies to store surfactants

Question 28

Adaptations of cardiac muscle cells + location

Answer 28

- Within heart tissue - responsible for beating - Branching which allows faster signal transmission and 3D contractions - small, narrow, rectangular - Cells connected by gap junctions which allows electrical conduction between cells

Question 29

Adaptations of striated muscle fibres + location

Answer 29

- connected to bones and is responsible for voluntary movement (locomotion) - Multiple nuclei and continuous plasma - made from fusion of cells - long cylindrical fibres - Packed together in strands to form muscle bundle

Question 30

Adaptations of sperm cells

Answer 30

- Small, motile, only donates male haploid nuclus to zygote - 3 parts - head, mid-piece and flagellum - Head contains male haploid nucleus, acrosome cap which contains hydrolitic enzymes to penetrate egg, and paired centrioles needed for division of zygote - Mid-piece contains many mitochondria to produce ATP for movement - Flagellum made of axoneme which bends to move

Question 31

Adaptations of egg cells

Answer 31

- large, non motile and donates all organelles and cytoplasm to zygote - Zona pellicuda - outer layer made of glycoprotein matrix which is a sperm barrier - Corona radiata - external follicular cells which provide nourishment - Contains cortical granules which release contents once fertilised to prevent multiple sperm binding