Topic 9 Cell Division

Question 1

Explain what a nucleus contains with detail

Answer 1

The nucleus of a cell contains chromosomes made of DNA molecules (chromosomes are sections of DNA that are tightly coiled to form compact structures)

Question 1

Genes explain in detail what they are and what Carry’s them?

Answer 1

Each chromosome carries a large number of genes. Gene = small section of DNA on a chromosome, which codes for a particular sequence of amino acids, to make a specific protein

Question 2

Explain in what grouping chromosomes are found in humans and why this is?

Answer 2

In body cells the chromosomes are normally found in pairs - most human body cells have 46 chromosomes (23 pairs; one chromosome in each pair comes from each parent)

Question 3

shortly summarise cell division why it happens and what is produced?

Answer 3

Cells divide in a series of stages called the cell cycle. During the cell cycle the genetic material is doubled and then divided into two identical cells

Question 4

Name the first stage of the cell cycle and explain what happens ?

Answer 4

Interphase: Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.

Question 5

Name the second stage of the cell cycle and explain what happens ?

Answer 5

Mitosis: In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.

Question 6

Name the third stage of the cell cycle and explain what happens ?

Answer 6

Cytokinesis: Finally the cytoplasm and cell membrane divides to form two identical cells

Question 7

Why is cell division by mitosis important?

Answer 7

Cell division by mitosis is important in the growth and development of multicellular organisms

Question 8

In mature animals cell division is mainly restricted to :

Answer 8

In mature animals, cell division is mainly restricted to repair of damaged tissues and replacement of old/damaged cells. (not “repair” of cells)

Question 9

Calculate the length of stages in the cell cycle equation:

Answer 9

Number of cells in particular stage / Total number of cells
* length of cell cycle

Question 10

Meristem tissue in plants can

Answer 10

differentiate into any type of plant cell, throughout the life of the plant

Question 11

Uses of stem cells from meristems in plants

Answer 11

-Produce clones of plants quickly and economically.
-Rare species can be cloned to protect from extinction.
-Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.

Question 12

In therapeutic cloning an embryo is produced

Answer 12

with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment

Question 13

The use of stem cells has potential risks short summary basically 1 marker

Answer 13

such as transfer of viral infection, and some people have ethical or religious objections

Question 14

As an organism develops, cells

Answer 14

differentiate to form different types of cells.

Question 15

As a cell differentiates it acquires different sub-cellular structures to

Answer 15

to enable it to carry out a certain function. It has become a specialised cell

Question 16

A stem cell is an

Answer 16

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

Question 16

Most types of animal cell differentiate at an —– whereas plant cells

Answer 16

early stage whereas many types of plant cells retain the ability to differentiate throughout life

Question 17

Stem cells from human embryos and adult bone marrow can be

Answer 17

cloned and made to differentiate into many different types of human cells

Question 18

Stem cells from adult bone marrow can

Answer 18

form many types of cells including blood cells

Question 19

Muscle cell function and adaptation :

Answer 19

function: contract and relax in order to move the skeleton, blood or substances in the body
adaptations: many mitochondria to provide energy for muscle contraction

Question 20

Root hair cell function and adaptation :

Answer 20

Function: Absorb water and mineral ions from the soil
Adaptations: - long ‘finger like’ villi which gives it a large surface area there is a thin wall to reduce the distance that molecules need to move to reach inside of the cell

Question 21

Sperm cell:

Answer 21

Function: this is the male gamete (sex cell) . It carries genetic information from the father and fertilises the egg cell
Adaptations:-many mitochondria to provide energy for movement of the tail
-the head has a specialised sac of enzymes called acrosome that digests the outer lining of the egg cell
-long tail to help propel the sperm along to the nucleus
-nucleus contains half the number of chromosomes of an adult cell

Question 22

Xylem cell
function and adaptations

Answer 22

function: to transport water and mineral ions from the roots of the leaves of a plant and provides support for the plant
adaptations: -consist of dead hollow cells- maximising space for water and dissolved substances to be transported
-walls of the xylem vessels are lignified (coated with lignin) this strengthens the xylem

Question 23

nerve cell
function and adaptions

Answer 23

function; to transmit information(messages) as electrical impulses
adaptations: long- to carry impulses rapidly throughout the body with no gaps between neurones
-insulatory sheath made of fatty myelin- to speed up impulses (100m/s)
-branched endings(dendrites)-make connections with other neurones and allow several different pathways for the impulse

Question 24

phloem cell
function and adaptations

Answer 24

function: to transport sugars
adaptations: -cross-walls separating cells are called sieve plates erforated by many pores to allow the sap to flow
-companion cells contain many mitochondria which provide energy needed to move sugars around the plant

Question 25

Issues and practical Problems with stem cells
(don’t mention ethical)

Answer 25

adult stem cells may not be able to be manipulated to produce all cell types. Which limits how adult stem cells can be use to treat diseases. Adult stem cells are also more likely to contain abnormalities due to environmental hazards, such as toxins, or from errors acquired by the cells during replication

Question 26

Ethical issues

Answer 26

human embryonic stem cell research is ethically and politically controversial because it involves the destruction of human embryos

Question 27

Embryonic stem cell
ability to differentiate
risks
is there a risk of rejection:

Answer 27

-Can differentiate into all types cell- so can treat many diseases
- risk of transmission of virus
- risk of cancer
- risk of infection during operation transplant
- risk of rejection stem cells.

Question 28

Adult stem cell therapy
ability to differentiate:
risks:
is there a risk of rejection:

Answer 28

can differentiate into some types of cells to treat less disease
-risk of transmission of virus
- risk of cancer
- risk of infection during operation transplant
risk of rejection need an adult donor can be painful to collect

Question 29

therapeutic/embryo cloning

Answer 29

-can differentiate into all types of cells so can differentiate into many types of cells
-risk of transmission of virus
- risk of cancer
- risk of infection during operation transplant
- risk of rejection stem cells from embryos can’t give consent or can be taken from amniotic fluid

Question 30

leaf palisade cell

Answer 30

The function of the palisade cell is photosynthesis. Each palisade cell contains chloroplasts which are used during this process. The palisade mesophyll cells are packed closely together to maximize light absorption for photosynthesis.

Question 31

red blood cells

Answer 31

Red blood cells are adapted for the transport of oxygen. They are small and flexible so they can fit through narrow vessels, have a bi-concave shape which maximises their surface area to absorb oxygen, have a thin membrane so gases easily diffuse through, and contain haemoglobin which binds to oxygen.

Question 32

specialised cells have a different —– that allows them to ——

Answer 32

structure, carry out their function