Cell Biology 2

Question 1

What is a stem cell?

Answer 1

An undifferentiated cell of an organism, capable of giving rise to many more cells of the same type, and from which certain other cells can arise by differentiation.

Question 2

Name the two types of stem cells found in animals.

Answer 2

-Embryonic stem cells
-Adult stem cells

Question 3

What is the function of stem cells in embryos?

Answer 3

To differentiate into all the cells needed in the human body (forming a foetus and then a baby).

Question 4

What is the function of adult stem cells?

Answer 4

They can differentiate into many types of cell including blood cells (red blood cells, white blood cells, and platelets) in order to replace damaged cells, keeping us alive.

Question 5

How do stem cells divide?

Answer 5

By mitosis.

Question 6

What can adult stem cells not do?

Answer 6

-Differentiate into ANY type of cell
-Form any new tissues like embryonic stem cells.

Question 7

Where are adult stem cells found?

Answer 7

Bone marrow

Question 8

How do we get embryonic stem cells?

Answer 8

-When a sperm cell fertilises an egg cell they form a single cell called a zygote.

-This cell then divides by mitosis to form a ball of cells which we call an embryo.

-The cells in this embryo are known as embryonic stem cells and can differentiate into any type of cell.

Question 9

What can all types of stem cell do?

Answer 9

-Divide by mitosis to form more cells
-Differentiate into specialised cells

Question 10

What do meristems (meristem tissues) contain?

Answer 10

Plant stem cells

Question 11

What is meristem tissue?

Answer 11

Tissue containing plant stem cells.

Question 12

What is the difference between plant stem cells and embryonic stem cells?

Answer 12

Plant stem cells persist for the plant’s entire life, whereas embryonic stem cells disappear by the time a person is fully developed.

Question 13

Differentiation

Answer 13

The process by which a cell changes to become specialised for its job.

Question 14

How can embryonic stem cells be used in labs?

Answer 14

They can be grown in a lab to produce clones (genetically identical cells) and made to differentiate into most types of specialised human cell for use in medicine or research.

Question 15

What conditions may treatment with stem cells be able to help?

Answer 15

-Diabetes
-Paralysis

Question 16

What happens in therapeutic cloning?

Answer 16

-An embryo is produced with the same genes as the patient.

-This means that the stem cells produced from the embryo would also contain the patient’s genes.

-Which means that the stem cells would not be rejected by the patient’s body if used in medical treatment to replace faulty cells.

Question 17

What are the risks of using stem cells in medicine?

Answer 17

-The transfer of viral infection
(-If stem cells grown in the lab become contaminated with a virus this can be passed on to the patient and so make them sicker)

Question 18

How can adult stem cells be used to cure blood-related diseases?

Answer 18

Stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in a patient.

Question 18

How can embryonic stem cells be used to cure diabetes?

Answer 18

You could make the stem cells differentiate into insulin-producing cells (beta cells in the pancreas).

Question 18

What ethical issues surround the use of embryonic stem cells?

Answer 18

-Each embryo has the potential for human life so shouldn’t be used for experiments

-Some people feel scientists should concentrate more on finding and developing other sources of stem cells (so ppl could be helped without using embryos)

-In some countries stem cell research is banned

Question 19

How can embryonic stem cells be used to cure paralysis?

Answer 19

You could make the stem cells differentiate into nerve cells for those paralysed by spinal injuries.

Question 20

Why might people be for stem cell research?

Answer 20

-Curing existing patients who are suffering is more important than the rights of embryos

-The embryos used in research are usually unwanted ones from fertility clinics so would’ve been destroyed anyway

Question 21

As stem cells from meristems in plants can differentiate into any type of cell throughout the plant’s entire life …

Answer 21

… they can be used to produce clones of whole plants quickly and cheaply. (economically).

Question 22

How can stem cells from meristems in plants be used?

Answer 22

-Rare species can be cloned to protect them from extinction

-Crop plants with desired features such as disease resistance can can be cloned to produce large numbers of identical plants for farmers.

Question 23

What are sperm cells specialised for?

Answer 23

Sperm cells are specialised for reproduction (to get the male DNA to the female DNA).

Question 24

How is a sperm cell adapted to perform its function?

Answer 24

-Long tail and streamlined head to help it swim to the egg
-Lots of mitochondria in the cell to provide the energy needed
-Carries enzymes in its head to digest through the egg cell membrane

Question 24

What are nerve cells specialised for?

Answer 24

To rapidly carry electrical signals from one part of the body to another.

Question 25

How are nerve cells adapted for their function?

Answer 25

-They are long (have a long axon) to cover more distance

-They have branched connections at their ends (dendrites and nerve endings) to connect to other nerve cells, forming a network throughout the body.

Question 26

What are muscle cells specialised for?

Answer 26

Muscle cells are specialised for (quick) contraction.

Question 27

How are muscle cells specialised for their function?

Answer 27

-Long so they have space to contract

-Contain lots of mitochondria to generate the energy needed for contraction

Question 28

Name some specialised cells in humans:

Answer 28

-Sperm cells
-Nerve cells
-Muscle cells

Question 29

Name some specialised cells in plants:

Answer 29

-Root hair cells
-Xylem and phloem cells

Question 30

What is cell differentiation?

Answer 30

The process by which a cell changes to become specialised for its job.

Question 31

Why is cell differentiation important?

Answer 31

It allows cells to specialise into different cells and perform specific functions in an organism. (happens as an organism develops).

Question 32

When do most types of animal cell differentiate?

Answer 32

At an early stage, as a multicellular organism develops.

Question 33

For animal cells, when is the ability to differentiate lost?

Answer 33

At an early stage, after they become specialised.

Question 34

In plant cells, when is the ability to differentiate lost?

Answer 34

For many plant cells-never. They retain the ability to differentiate throughout life.

Question 35

In mature animals, cell division is what?

Answer 35

Mainly restricted to repair and replacement.

Question 36

As a cells differentiate, they…

Answer 36

develops different sub-cellular structures and so turn into different types of cells.

Question 37

What can embryonic stem cells do that adult stem cells can’t?

Answer 37

Form new tissue. Adult stem cells can only repair damaged tissue.

Question 38

What can plant stem cells differentiate into?

Answer 38

Any type of cell or tissue that a plant needs (e.g. palisade cells where photosynthesis occurs, root hair cells, xylem and phloem cells).

Question 39

Where is meristem tissue found?

Answer 39

The growing tips of roots and shoots.

Question 40

Cells in plant roots don’t photosynthesise. Give reasons why.

Answer 40

-They have no chloroplasts

-Photosynthesis needs light

-They’re underground

Question 41

Suggest why the number of live bacteria cells in a colony may decrease over time.

Answer 41

-Lack of nutrients/ oxygen/space

-Temperatures are too high

-A build up of toxins