Theme B: Cells - B2.3 Cell Specialisation

Question 1

the development progression for humans

Answer 1

gametes –> zygote –> embryo –> foetus –> infant

Question 2

gametes

Answer 2

the 2 cells that fuse together in sexual reproduction. Gametes are haploid sex cells (sperm in males and eggs in females) that carry half the genetic material of an organism.

Question 3

zygote

Answer 3

A zygote is the diploid cell formed when two haploid gametes (sperm and egg) fuse during fertilization. It is the first stage of development in a multicellular organism.

Question 4

cell differentiation

Answer 4

Cell differentiation is the process by which unspecialized cells, such as stem cells, develop into specialized cells with distinct structures and functions. This occurs through the selective expression of certain genes while others are suppressed.

Question 5

after fertilization

how do cells intitially develop?

(in humans)

Answer 5

the zygote can divide very rapidly, and while the cells initially produced are unspecialised, the cells of the zygote also rapidly differentiate. this process results in the formation of specialised cells driven by the selective expression of certain genes while others remain inactive.

each cell will develop in a very specific manner depending on which genes become active and which signals the cell recieve.

Question 6

cell signalling

Answer 6

the process by which infomrtaion is transferred from the cell surface to the nucleus. this is essential in controllong gene expression and thus differentiation.

Question 7

morphogens

what are they? how does it effect the development of cells?

Answer 7

signal molecules that control cell differntiation. they occur in gradients (areas of concentration differences) in different regions of the early embryo.

the concentration of the signal molecules controls the regional development of teh first cells into head and tail structures.

the gradient of the signal molecules results in diffferent genes being expressed in different parts of the embryo. this leads different parts of the embryo to develop different structures.

as embryo develops, other signalling molecules become factors in differentitaion.

Question 8

stem cells

Answer 8

population of cells within organisms that retain the ability to divide indefinetely and can differentiate along different pathways, resulting in all the cell types an organism posses.

Question 9

meristematic tissue

Answer 9

Where stem cells are contained in plants. it’s composed of rapidly reproducing cells that can various types if tissue within the root or stem (a.k.a stem cells).

gardeners take advantage of these cells when they take cuttings from stems or roots and use them to grow new plants.

Question 10

2 unique properties of stem cells

Answer 10

1) self renewal
2) recreate functional tissues

Question 11

self renewal

Answer 11

when a stem cell divides, there are sveral possible outcomes:
1) both daughter cells remain stem cells
2) a stem cell and a differentiated cell may be formed
3) both cells differentiate
whatever the outcome is, the stem cells are maintained.

this process allows the continual production of a particular tissue whilse also providing for the continuation of stem cells.

Question 12

stem cell niches

Answer 12

in a stem cell niche, the stem cells are present in high numbers due to regular proliferation.
e.g. bone marrow and hair follicles (in humans)
stem cell niches in humans are also studied in the contral nervous system, intestinal system, and in the muscle fibre bundles.

Question 13

bone marrow

(as a stem cell niche)

Answer 13

stem cells that produce blood cells are found in the bone marrow alongside self renewing stem cells.

as blood cells are produced, differentiated cells are transported away via a large array of supporting blood vessels.

bone marrow tissue is multipotent.

the soft, spongy tissue that is in the medullary cavities (centers) of bones

Question 14

hair follicles

as stem cell niches

Answer 14

they exist in the skin, and large numbers of epithelial stem cells are found in the bottom rounded area of a hair follicle. these stemc ells are multipotent.

these stem cells are also involved with hair growth, skin and hair follicle regeneration, and the production of sebaceous (oil-producing) glands associated with hair follicles.

a tube-like structure (pore) that surrounds the root and strand of a hair

Question 15

what feature to all stem cell niches all have in common?

Answer 15

the presence of signalling factors that bring about both self renewal and differentiation.

Question 16

types of stem cells

(in order of decreasing potency)

Answer 16

1) totipotent (total - most ‘potent’)
2) pluripotent (plural)
3) multipotent (multiple)
4) unipotent (one - least potent)

Question 17

totipotent

Answer 17

• capable of continued dividiion and possesses the ability to produce any tissue in the organism.
• very few cells are totiptent.
• only exist in very early stages of embryo development.
• they may form a complete organism.

Question 18

pluripotent

Answer 18

• arise form totipotent cells and only exist in early embryonic stage
• can mature into almost all the differnet cell types that exist in an organism
• unlike totipotent, they cannot produce a complete organism.

Question 19

multipotent

Answer 19

• only forms limited number of cell types.
• bone marrow tissue is multipotent
• they occur later in the development of the embryo and present during the remainder of an organism’s life

Question 20

unipotent

Answer 20

• only forms a single cell type, e.g. sperm cells in mammals
• usually form late in the embryonic stage and exist in the funcioning organism

Question 21

one problem with using stem cells to treat disease

Answer 21

stem cells cannot be distinguished by appearance. they can only be isolated form other cells based on their behaviour.

Question 22

therapuetic clones

Question 23

cell type and size (in decreasing order)

Answer 23

sperm cell:
egg cell
fat cell
red blood cell
white blood cell
skeletal muscle fibre
neuron (nerve cell)

Question 24

what is cell size determined by

Answer 24

function of a cell determines its size

Question 25

sperm cell size importance

Answer 25

sperm cells are relatively small because they only carry out the function of transporting genetic material so viable zygote can be formed.

Question 26

red blood cell adaptations to carry oxygen through the organism

Answer 26

1) contain haemoglobin that combine with and release oxygen
2) biconcave disk shape allowing more surface area for oxygen absorption
3) lack mitcohondria and nucleus
4) flexible and limited size because they need to move through narrow blood capillaries

Question 27

white blood cell size

Answer 27

• bigger than red blood cell
• main function is defense against infections