Download 2.5 Growth and repair – Questions and answers Q1. Bk Ch2 S2.5 Q1

2.5 Growth and repair – Questions and answers
Q1.
Bk Ch2 S2.5 Q1
Outline the significance of cell division in multicellular organisms.
A1.
Bk Ch2 S2.5 A1
Cell division in multicellular organisms is important because it allows organisms to grow, repair
damaged tissue, and maintain and reproduce themselves.
Q2.
Bk Ch2 S2.5 Q2
a
b
c
Define ‘mitosis’.
Use diagrams to illustrate the activities of chromosomes during the different phases of mitosis.
What is cytokinesis?
A2.
Bk Ch2 S2.5 A2
a
b
c
Mitosis is a particular kind of nuclear division resulting in the production of new cells that are
identical to the original cell.
Example diagram:
Cytokinesis is the division of the cytoplasm. It occurs after mitosis is complete and results in the
formation of two separate cells.
Q3.
Bk Ch2 S2.5 Q3
Describe what happens during the four phases of the cell cycle. Use diagrams to illustrate your answer.
A3.
Bk Ch2 S2.5 A3
The G1 stage occurs between the end of mitosis and the beginning of chromosome duplication. Cell
growth occurs during this time. During the S stage DNA synthesis occurs. This is the period during
which chromosomes are duplicated. The next stage is G2 and it occurs between the end of DNA
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synthesis and the beginning of the mitotic process. This is another period of growth for the cell.
Finally, the M stage is characterised by the process of mitosis: duplicated chromosomes separate to
form two daughter nuclei.
The following diagram is one way of illustrating the cell cycle.
Q4.
Bk Ch2 S2.5 Q4
Interphase is often referred to as a resting phase for the cell nucleus because the chromosomes are not
visible and seem to be inactive. Is this a correct description of the interphase nucleus? Explain your
answer.
A4.
Bk Ch2 S2.5 A4
No. During interphase cells are very active. As well as continuing all other normal cell functions, cells
grow and synthesise new DNA during this period.
Q5.
Bk Ch2 S2.5 Q5
a
b
Define ‘cell differentiation’.
Outline the importance of cell differentiation in multicellular organisms.
A5.
Bk Ch2 S2.5 A5
a
b
Cell differentiation is the process through which cells become different from one another,
acquiring features that allow them to take on specialised functions.
Cell differentiation is important in multicellular organisms because it ensures that every function
required by the body is able to occur. For example, nerve cells are specialised to transmit
information, red blood cells are specialised to carry oxygen. (If no cell differentiation occurred in
multicellular organisms all cells would be the same and no specialised functions could occur.)
Q6.
Bk Ch2 S2.5 Q6
Discuss some of the outcomes of uncontrolled cell growth in multicellular organisms.
A6.
Bk Ch2 S2.5 A6
Uncontrolled cell growth results in a mass of abnormal cells called a tumour. Tumour cells can be
cancerous when they grow in a disorderly way and bind to other cells and spread to other tissue
throughout the body.
Q7.
Bk Ch2 S2.5 Q7
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Identify the stages of mitosis illustrated in the following photographs.
A7.
Bk Ch2 S2.5 A7
a
b
Interphase
Metaphase
Q8.
Bk Ch2 S2.5 Q8
a
b
What is the role of the nucleus in cells?
What is DNA? How is it important in the functioning of cells?
A8.
Bk Ch2 S2.5 A8
a
b
The nucleus is the control centre of the cell; it is responsible for directing all of the activities of
the cell.
DNA is a particular kind of nucleic acid found in the nucleus of cells. The chromosomes present
in the nucleus are composed of this chemical. DNA contains the coded information that makes up
our genes and directs all of the cell’s activities including growth and differentiation.
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