B2.1 Supplying the cell - Part 3

Question 1

<p>What is differentiation?</p>

Answer 1

<p>Process by which stem cells become specialised into different types of cells</p>

Question 2

<p>What is produced once a sperm cell enters an egg?</p>

Answer 2

<p>Zygote</p>

Question 3

<p>By what process does a zygote divide?</p>

Answer 3

<p>Mitosis</p>

Question 4

<p>The zygote is composed of what type of cells?</p>

Answer 4

<p>Stem cells</p>

Question 5

<p>When does a zygote become an embryo?</p>

Answer 5

<p>3-5 days after fertilisation</p>

Question 6

<p>How do the cells of a zygote differ from an organisms somatic cells?</p>

Answer 6

<p>They are unspecialised and can therefore differentiate into any type of specialised cell.</p>

Question 7

<p>Where are stem cells found in animals?</p>

Answer 7

<p>Embryos - Embryonic stem cellsBrain, bone marrow, skin, liver - Adult stem cellsN.B Multipluripotent stem cells have also now been isolated in the umbilical cord</p>

Question 8

<p>Where are stem cells found in plants?</p>

Answer 8

<p>The meristems - unspecialised cells found in the root tips, shoot tips and in rings around the stem</p>

Question 9

<p>How do the cells in the meristem differ from normal plant cells?</p>

Answer 9

<p>Differentiated plant cells cannot divide as they have thick & rigid cell wallsMeristem cells are much smaller, have thin walls, small vacuoles and no chloroplasts</p>

Question 10

<p>State a key difference between specialised plant and animal cells?</p>

Answer 10

<p>Once differentiated animal cells can only divide to produce that specialised cells.Plant cells however, under the right conditions, can become unspecialised and then re-specialise in order to adapt to their environment.</p>

Question 11

<p>Name 5 types of specialised cells that a stem cell could differentiate into.</p>

Answer 11

<p>Animal</p>

<ul> <li>Gamete e.g sperm cell, ovum</li> <li>Muscle cell</li> <li>Adipocyte cell</li> <li>Osteoblast</li> <li>Blood cell e.g erythrocyte, neutrophils</li> <li>Nerve cell</li> <li>Cilliate epithelial cell</li> <li>Goblet cell</li></ul>

<p></p>

<p>Plant</p>

<ul> <li>Palisade cells</li> <li>Root hair cell</li> <li>Guard cell</li></ul>

Question 12

<p>How is a red blood cell specialised for its role?</p>

Answer 12

<ul> <li>Biconcave discs - increases surface area</li> <li>Haemoglobin - binds to and releases oxygen</li> <li>Enucleated - more room for oxygen transport</li></ul>

Question 13

<p>How is sperm cell is specialised to transfer genetic material?</p>

Answer 13

<ul> <li>Flagellum - movement</li> <li>Mitochondria - provide energy for movement</li> <li>Acrosome - contains digestive enzymes to allow breakdown the outer membrane of ovum</li></ul>

Question 14

<p>How is an adipocyte specialised for its role?</p>

Answer 14

<ul> <li>Can expand to 1000 times original size</li> <li>Small layer of cytoplasm</li> <li>Fat reservoir.</li></ul>

Question 15

<p>What is the function of a goblet cell?</p>

Answer 15

<p>Produces mucus to trap dustmucus and bacteria which the cillia then waft back up the throat to be swallowed.</p>

Question 16

<p>How are palisade cells adapted for their function?</p>

Answer 16

<ul> <li>regularly shaped - can be closely packed cells that form a continuous layer at the top of the leaf</li> <li>Large surface area - able to absorb more light for photosynthesis</li> <li>Packed with chloroplasts - for photosynthesis</li></ul>

Question 17

<p>How are root hair cells adapted for their function?</p>

Answer 17

<ul> <li>Surround the stoma and regulate the rate of transpiration and CO₂ uptake.</li> <li>Inner wall thicker causing the ‘bean-like’ shape and gap when turgid</li> <li>Open to allow exchange</li> <li>Close to prevent exchange</li></ul>

Question 18

<p>What type of cells can adult stem cells differenetiate into?</p>

Answer 18

<p>Only into cells from the type of tissue where they are found.</p>

Question 19

<p>Why are adult stem cells not as useful for medical research?</p>

Answer 19

<p>They only differentiate into a narrowrange of cell types</p>

Question 20

<p>What are embryonic stem cells and why are they more useful to stem cell research?</p>

Answer 20

<ul> <li>Cells taken from 3-5 day old zygotes</li> <li>Thye can specialise into any type of specialised cells</li> <li>Potential to cure and treat disease</li></ul>

Question 21

<p>Why are embryonic stem cells controversial?</p>

Answer 21

<p>Embryos are killed to obtain the cells.</p>

Question 22

<p>What are induced-pluripotent stem cells and how may they be useful?</p>

Answer 22

<ul> <li>Adult somatic cells altered to have properties of embryonic stem cells</li> <li>May allow use of reprogrammed cells instead of embryonic stem cells</li> <li> <p>Solution to immune system rejection of ‘foreign’ stem cells</p> </li></ul>